ALBERT

Description: 〈p〉Publication date: Available online 27 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society〈/p〉 〈p〉Author(s): S. Mestre, A. Gozalbo, M.M. Lorente-Ayza, E. Sánchez〈/p〉 〈h5〉Summary〈/h5〉 〈div〉〈p〉Obtaining low-cost ceramic membranes has attracted great interest in the scientific community in last years, as it allows to preserve the advantages of ceramic materials while significantly reduce their manufacturing costs. This type of membranes is mainly based on the use of raw materials and manufacturing processes typical of traditional ceramic materials, i.e silicate-based ceramics. This work exhaustively reviews the raw materials, ceramic compositions and variables of the manufacturing processes used in the development of these membranes, with special emphasis on their numerous potential industrial applications.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 25 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society〈/p〉 〈p〉Author(s): Elaheh Taghaddos, Harry Charalambous, Thomas Tsakalakos, Ahmed Safari〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Lead-free, (BiNa〈sub〉0.88〈/sub〉K〈sub〉0.08〈/sub〉Li〈sub〉0.04〈/sub〉)〈sub〉0.5〈/sub〉Ti〈sub〉0.995〈/sub〉 Mn〈sub〉0.015〈/sub〉 O〈sub〉3〈/sub〉 piezoceramic has been successfully densified by a novel electrical current applied technique known as flash sintering (FS) at 880 °C. The effect of alternating and direct current, current density limit and holding time on the densification, crystal structure, electromechanical and electrical properties have been investigated. The optimum flash condition was obtained with a 1 KHz alternating current, 100 V·cm〈sup〉−1〈/sup〉 initial electric field and preset maximum current limit of 1.5 A·cm〈sup〉-2〈/sup〉. The flash sintered specimen is characterized with finer grain size (10–15 μm), slightly higher electromechanical properties and higher symmetry butterfly shape strain hysteresis loop compared to conventional sintering. Under both sintering conditions uniform distribution of elements and pure rhombohedral structure were observed. Flash sintering also results in lower resistivity and more significant grain boundaries contributions in the conduction mechanism.〈/p〉〈/div〉

Description: 〈p〉Publication date: July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 8〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): July Andrea Rincón-López, Jennifer Andrea Hermann-Muñoz, David Andrés Fernández-Benavides, Astrid Lorena Giraldo-Betancur, Juan Manuel Alvarado-Orozco, Juan Muñoz-Saldaña〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, a systematic methodology to obtain third-generation bioceramics within the Ca〈sub〉2〈/sub〉SiO〈sub〉4〈/sub〉-Ca〈sub〉3〈/sub〉(PO〈sub〉4〈/sub〉)-NaCaPO〈sub〉4〈/sub〉 ternary system is proposed. The synthesis of Silicocarnotite (Ca〈sub〉5-x〈/sub〉(PO〈sub〉4〈/sub〉)〈sub〉2+x〈/sub〉(SiO〈sub〉4〈/sub〉)〈sub〉1-x〈/sub〉; x ≤ 0.3) (SC) and Nagelschmidtite (Ca〈sub〉7-x〈/sub〉Na〈sub〉x〈/sub〉(PO〈sub〉4〈/sub〉)〈sub〉2+x〈/sub〉(SiO〈sub〉4〈/sub〉)〈sub〉2-x〈/sub〉; x ≤ 2) (Nagel) single phases, from mixtures of bovine-derived HAp (BHAp) and 45S5-bioactive glass (BG) as precursors was developed using design of experiments (DoE). A combination of milling and sintering processing parameters was established by statistical analysis to optimize the microstructural and mechanical properties of BHAp/BG ceramics. The optimized sintering temperature obtained with simultaneous responses was 1220 °C. Variations in BHAp/BG ratios lead to isothermal phase transformation to single crystalline phases, where 85/15 and 70/30 vol:vol ratios transformed to SC and Nagel, respectively. Finally, the proposed methodology allows a feasible composition control depending only of BHAp/BG ratio to obtain non-stoichiometric SC and Nagel phases with potential applications in bone repair.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Václav Pouchlý, Jozef Ráheľ, Tomáš Spusta, Martina Ilčíková, David Pavliňák, Tomáš Morávek, Karel Maca〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Submicron Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 powders were activated by Diffuse Coplanar Surface Barrier Discharge (DCSBD) plasma. The influence of the plasma treatment on the powder properties and their impact on the microstructure of dry and wet shaped ceramics were investigated. Raman and FTIR analyses of treated powders showed a substantial increase of the powder’s surface hydroxylation, surface cleaning, and the presence of adsorbed NO〈sub〉x〈/sub〉 originating from the DCSBD. Sintering of the dry shaped plasma treated powders did not influence sintering behavior. On the other hand, the plasma treated powder was able to form stable water suspension without any chemical stabilization aid. Slip cast samples exhibited finer pore size distribution, a higher sinterability, and a finer final microstructure. The grain size of slip casted plasma treated powder was reduced by a factor of 1.7, which facilitated a grain size of 0.68 μm at the relative density of 99.54% t.d. obtained by pressure-less sintering.〈/p〉〈/div〉

Description: 〈p〉Publication date: May 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 5〈/p〉 〈p〉Author(s): Siqi Zhang, Artemis Stamboulis, Wen Ni〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Calcium fluoro-aluminosilicate (4.5SiO〈sub〉2〈/sub〉-3Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-1.5P〈sub〉2〈/sub〉O〈sub〉5〈/sub〉-3CaO-2CaF〈sub〉2〈/sub〉) glasses have significant applications in the medical and dental fields. However, due to the biological hazard of aluminium in the human body, this study focused on the influence of boron substitution for aluminium on the structure and properties of a series of substituted glasses and their correlated glass-ceramics. The results indicated that by increasing the amount of boron, the density of glasses and their glass-ceramics both decreased, whereas the number of bridging oxygens in the glasses increased. The glass transition temperature and the crystallization temperature remained almost unchanged for the glasses with a boron substitution of less than 25 mol%. Boron formed oxygen bridges in all glasses in the form of BO〈sub〉3〈/sub〉 triangles and BO〈sub〉4〈/sub〉 tetrahedra. Reducing the Al content in glasses, had an effect on the morphology and orientation of the fluorapatite crystal phase formed.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Massimo Rosa, Philippe Zielke, Ragnar Kiebach, Victor Costa Bassetto, Andreas Lesch, Vincenzo Esposito〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Water-based inks, containing nanometric NiO and YSZ particles in 66/34 vol. % ratio, are produced by colloidal stabilization of a binary dispersion obtained 〈em〉via〈/em〉 continuous hydrothermal synthesis at supercritical conditions, i.e. 280 bar and 400 °C. The method yields single-crystal particles with diameter ≤ 10 nm for both phases in a single-step process, achieving a highly mixed composite. Two different approaches are applied to formulate inks printable with piezoelectric printheads, i.e. an electrostatic and an electrosteric stabilization path. The use of an electrosteric dispersant results in colloids with superior stability 〉 200 days, more uniform thin films and finely nanostructured porous cermet films with thickness below 500 nm, after reducing NiO to Ni. Particles coarsening to 50–150 nm is obtained at 1000 °C, accompanied by a shrinkage of 〈em〉ca.〈/em〉 43% in thickness without the formation of cracks or delamination of the zirconia substrates.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Alexander Martin, Neamul H. Khansur, Kevin Riess, Kyle G. Webber〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Relaxor ferroelectrics are a unique material class with underlying microscopic processes that are yet to be fully understood. In particular, the electrical and mechanical field-modulated transition from the relaxor state to long-range ferroelectric order has been found to be the origin of the large unipolar strain response in some lead-free ferroelectric systems. Importantly, the dynamics of this transition are different than the domain wall nucleation and growth found in normal ferroelectrics, significantly changing the frequency response. In this study, the electromechanical behavior of a (Na〈sub〉1/2〈/sub〉Bi〈sub〉1/2〈/sub〉)TiO〈sub〉3〈/sub〉-based lead-free relaxor ferroelectric is shown under applied external mechanical and electric field over several orders of magnitude in loading rate. Depending on the loading history, it is possible to directly investigate both the relaxor-to-ferroelectric transition as well as domain wall motion in the same sample. These data demonstrate the variations in frequency response between these nonlinear hysteretic processes.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Jun Cao, Vladimir Koval, Hangfeng Zhang, Yunyin Lin, Jiyue Wu, Nan Meng, Yan Li, Zheng Li, Hongtao Zhang, Haixue Yan〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Highly textured Ba〈sub〉2〈/sub〉Bi〈sub〉4〈/sub〉Ti〈sub〉5〈/sub〉O〈sub〉18〈/sub〉 ceramic was prepared by spark plasma sintering (SPS). X-ray diffraction of the ceramics revealed the coexistence of a major ferroelectric phase (Space group, SG: 〈em〉B〈/em〉2〈em〉cb〈/em〉) and a minor paraelectric phase (SG: 〈em〉I4/mmm〈/em〉) at room temperature. A diffused phase transition was observed at around 240 °C. The evolution of the switching current peaks in the electric current 〈em〉vs〈/em〉. electric field (〈em〉I-E〈/em〉) loops with increasing temperature was interpreted by the structural changes and temperature dependent polarisation reversal processes. The slim polarisation 〈em〉vs〈/em〉. electric field (〈em〉P-E〈/em〉) loops, the extra switching current peaks in the 〈em〉I-E〈/em〉 loops and the non-zero piezoelectric 〈em〉d〈/em〉〈sub〉33〈/sub〉 coefficient indicate that Ba〈sub〉2〈/sub〉Bi〈sub〉4〈/sub〉Ti〈sub〉5〈/sub〉O〈sub〉18〈/sub〉 is a relaxor ferroelectric material. The recoverable energy density (0.41 ± 0.01 J/cm〈sup〉3〈/sup〉) of Ba〈sub〉2〈/sub〉Bi〈sub〉4〈/sub〉Ti〈sub〉5〈/sub〉O〈sub〉18〈/sub〉 ceramics in the perpendicular direction to the SPS pressing direction is close to that of Pb(Mg〈sub〉1/3〈/sub〉Nb〈sub〉2/3〈/sub〉)O〈sub〉3〈/sub〉-based ceramics. The obtained results suggest Ba〈sub〉2〈/sub〉Bi〈sub〉4〈/sub〉Ti〈sub〉5〈/sub〉O〈sub〉18〈/sub〉 ceramics might be promising for energy storage applications.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Sandrine Duluard, Elodie Delon, Jean-Pierre Bonino, André Malié, Aurélien Joulia, Luc Bianchi, Philippe Gomez, Florence Ansart〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Reactions between calcium magnesium aluminium silicates (CMAS) and Gd〈sub〉2〈/sub〉Zr〈sub〉2〈/sub〉O〈sub〉7〈/sub〉 or 2ZrO〈sub〉2〈/sub〉∙Y〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 (〈em〉ss〈/em〉) are investigated within a temperature range of 1200–1300 °C and for durations of 1 h–100 h. The evolution of CMAS penetration depth in Gd〈sub〉2〈/sub〉Zr〈sub〉2〈/sub〉O〈sub〉7〈/sub〉 and 2ZrO〈sub〉2〈/sub〉∙Y〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 (〈em〉ss〈/em〉) pellets varies considerably depending on the interaction time. A quantitative analysis of the nature and composition of phases observed in stationary conditions (powder/powder interaction) is performed by SEM-FEG coupled with WDS analyses using micro-agglomerated nanoparticles of Gd〈sub〉2〈/sub〉Zr〈sub〉2〈/sub〉O〈sub〉7〈/sub〉 and 2ZrO〈sub〉2〈/sub〉∙Y〈sub〉2〈/sub〉O〈sub〉3〈/sub〉. Faster kinetics of the gadolinium-based system are illustrated through an analysis of the morphology of the reaction area and of the resulting CMAS tightness of reaction products. The compositions and quantities of reaction products observed at equilibrium are very similar for the two systems, but transient states are significantly different.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Tae-Gon Lee, Sung-Hoon Cho, Dae-Hyeon Kim, Hyun-Gyu Hwang, Ku-Tak Lee, Chang-Hyo Hong, Youn-Woo Hong, Keun Hwa Chae, Ji-Won Choi, Jeong-Seog Kim, Sahn Nahm〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉CuO-added (1-y)(Na〈sub〉0.5〈/sub〉K〈sub〉0.5〈/sub〉)(Nb〈sub〉1-x〈/sub〉Sb〈sub〉x〈/sub〉)-yCaTiO〈sub〉3〈/sub〉 ceramics with 0.0 ≤ x ≤ 0.1 and 0.04 ≤ y ≤ 0.055 were sintered at 970 °C. Various cubic-based polymorphic-phase-boundary (PPB) structures were formed: orthorhombic-tetragonal-cubic, and tetragonal-cubic PPB structures. The crystal structure of the specimens near Curie temperature is a mixture of 〈em〉Pm3m〈/em〉 cubic and 〈em〉P4mm〈/em〉 tetragonal structures and these ceramics showed ferroelectric properties. A schematic phase diagram of these ceramics has been suggested. The piezoelectric properties of these specimens were influenced by their crystal structure. All the specimens are expected to have good fatigue properties. In particular, the specimen with a tetragonal-cubic PPB structure (x = 0.04 and y = 0.045) has a large 〈em〉d〈sub〉33〈/sub〉〈/em〉 of 338 pC/N and a high strain of 0.17% at 4.5 kV/mm. This specimen has good temperature stability; a 〈em〉d〈sub〉33〈/sub〉〈/em〉 value of 300 pC/N and strain of approximately 0.12% were obtained at 175 °C, indicating that this specimen is a good candidate for use as a piezoelectric multilayer actuator.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Hongquan Zhan, Chuanqi Wu, Ce Deng, Xiaohong Li, Zhipeng Xie, Changan Wang, Zhi-gang Chen〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The formation mechanism of titania based opacified glaze is discussed in this paper. The glaze system composed of albite, kaolin, talc, calcite, quartz, titanium dioxide and zinc oxide is used to adjust the glaze formula and to obtain the glaze samples with better opacifying effect. The whiteness and glossiness of glaze products formed with different TiO〈sub〉2〈/sub〉 contents are characterized by whiteness meter and gloss meter respectively. The structure of glaze layer is analyzed by means of SEM, TEM and EDS. The results show that the introducing of TiO〈sub〉2〈/sub〉 can promote the phase separation and forms the special Si-rich/Ti-rich core-shell nanostructure. During the cooling process of the glaze, the liquid-liquid phase separation occurs and results in the formation of uniform Si-rich nanoparticles. While the Ti-containing components are enriched at the interface between the different phases and a special spherical core-shell structure is obtained around the Si-rich nanoparticles. The glaze layer is filled with the core-shell nanospheres and shows a network structure like opal. However, due to the decrease of cationic content (Ti, Zn, Ca, and Mg) in the interface between glaze and body, the network nanostructure like reverse opal would be formed. In the interaction of special opal and reverse opal structure, the opacifying effect is enhanced obviously.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Wei Fu, Xiaoguo Song, Alberto Passerone, Shengpeng Hu, Hong Bian, Yixuan Zhao, Meirong Wang, Fabrizio Valenza〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Brazing and soldering following pre-metallization were employed to obtain reliable ZrO〈sub〉2〈/sub〉/Sn-Ti/ZrO〈sub〉2〈/sub〉 joints. Both the metallization and brazing depend on the wettability of ZrO〈sub〉2〈/sub〉 by Sn-Ti alloys. The interfacial microstructure of joints was analyzed by SEM, XRD and TEM, and the shear strength of joints was evaluated. Good brazed joints and fully covered metallization layers, leading to good soldered joints, were obtained by the Sn-4Ti and Sn-8Ti alloys, while unsatisfactory results were obtained with Sn-1Ti and Sn-2Ti alloys owing to their limited wettability on ZrO〈sub〉2〈/sub〉. Both kinds of ZrO〈sub〉2〈/sub〉/Sn-Ti/ZrO〈sub〉2〈/sub〉 joints possessed a β-Sn matrix with Ti〈sub〉6〈/sub〉Sn〈sub〉5〈/sub〉 and Ti〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 interfacial layers. A higher Ti concentration per unit area induced the formation of a Ti〈sub〉11.31〈/sub〉Sn〈sub〉3〈/sub〉O〈sub〉10〈/sub〉 layer along with the reduction of the Ti〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 layer thickness at the interface in the soldered joints. All the joints exhibited a similar shear strength of 22 ∼ 28 MPa and fractured through the β-Sn matrix.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Liangbo Sun, Chunfeng Liu, Jian Fang, Jie Zhang, Chengjie Lu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉B〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-containing MgO-Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-SiO〈sub〉2〈/sub〉-Li〈sub〉2〈/sub〉O glass-ceramics were fabricated via crystallization treatment of primal glasses for the purpose of joining Si〈sub〉3〈/sub〉N〈sub〉4〈/sub〉 ceramics. The effects of B〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 content on the crystallization behavior, coefficient of thermal expansion and softening temperature of MgO-Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-SiO〈sub〉2〈/sub〉-Li〈sub〉2〈/sub〉O-B〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 glasses were investigated. The results reveal that the glass transition temperature and the crystallization temperature of the glasses decrease with the increasing B〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 content. It also demonstrates that γ-spodumene solid solution is detected in the glass-ceramics after heat treatment at 735 °C and 840 °C, respectively, whereas the heat treatment at 1000 °C results in the precipitation of β/γ-spodumene coexisting phases solid solution and forsterite. Additionally, by controlling the composition and crystallization treatment, the CTEs of glass-ceramics can be matched with the Si〈sub〉3〈/sub〉N〈sub〉4〈/sub〉. Furthermore, contact angle measurement confirms that the glass-ceramics possess a good wettability on the Si〈sub〉3〈/sub〉N〈sub〉4〈/sub〉 substrate, which can be considered as the candidate materials for joining Si〈sub〉3〈/sub〉N〈sub〉4〈/sub〉 ceramics.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Jian Yang, Junnan Yan, Guiwu Liu, Zhongqi Shi, Guanjun Qiao〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉To improve the thermoelectric properties of n-type Bi〈sub〉2〈/sub〉S〈sub〉3〈/sub〉 materials, a certain amount of SbCl〈sub〉3〈/sub〉 were added into Bi〈sub〉2〈/sub〉S〈sub〉3〈/sub〉 materials by a conventional melting method combined with plasma activated sintering (PAS) process. The Bi〈sub〉2〈/sub〉S〈sub〉3〈/sub〉-based materials evolve from the lamellar- to particle-like structures after SbCl〈sub〉3〈/sub〉 doping. The phonon scattering has strong enhancement through the increased grain boundaries and in-situ Bi〈sub〉2〈/sub〉S〈sub〉3〈/sub〉 nanoprecipitates, resulting in the low lattice thermal conductivity. Meanwhile, the high power factor is achieved because of the marked increase in the electrical conductivity. Hence, the synergistic effect of antimony and chlorine substitutions not only contribute to reduce the thermal conductivity but also tune the electrical transport properties, yielding a peak ZT value of ∼ 0.65 at 773 K for the Bi〈sub〉2〈/sub〉S〈sub〉3〈/sub〉-1%SbCl〈sub〉3〈/sub〉 sample.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Eleni Temeche, Eongyu Yi, Vazrik Keshishian, John Kieffer, Richard M. Laine〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Traditionally, C12A7 materials have been processed via solid-state reaction followed by pulsed laser deposition (PLD) or floating zone (Fz) crystallization methods at high temperature, high cost approaches to single-phase films. These techniques require a significant number of process steps to generate C12A7:e〈sup〉−〈/sup〉 materials that have been shown to exhibit exceptional electrical conductivities as high as 1 S/cm. We demonstrate here an effective alternative method using flame made C12A7 nanopowders (NPs) produced via liquid-feed flame spray pyrolysis (LF-FSP). Nearly fully dense, single phase, and transparent C12A7 films (〈 50 μm) can be produced by processing these NPs into green films by tape-casting, thermo-compression and then sintering to 1300 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mi〉℃〈/mi〉〈/math〉/3 h/O〈sub〉2〈/sub〉. Subsequent heat treatments in 20/80 H〈sub〉2〈/sub〉/N〈sub〉2〈/sub〉 replaces cage trapped O〈sup〉2-〈/sup〉 ions forming C12A7:H〈sup〉−〈/sup〉 followed by UV irradiation to generate C12A7:e〈sup〉−〈/sup〉 with electrical conductivities of 35 mS cm〈sup〉-1〈/sup〉. C12A7:e- appears to belong to a new class of transparent conducting oxides (TCOs) that may offer commercial potential on further optimization due to low materials and processing costs, environmental stability, and natural abundance when processed efficiently.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Rui M. Novais, Robert C. Pullar〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Cork templates were used to produce lightweight bulk biomimetic ecoceramic (environmentally conscious ceramic) monoliths. Bulk/monolithic ceramics are vital for many applications, i.e. energy materials and fuel cells. Using simple and flexible, aqueous green-chemistry procedures, for the first time the influence of infiltration regime, number of infiltration cycles and sintering temperature on ecoceramic density and microstructure was studied. This lightweight three-dimensionally ordered macroporous (3DOM) CeO〈sub〉2〈/sub〉 preserved the hexagonal cellular structure of cork, but unlike the wood, the rear cell walls were open, greatly increasing open porosity. Higher sintering temperatures (1600 instead of 1000 °C) were required to produce cm size monolithic ecoceramics mechanically strong enough to be handled. The infiltration regime and number of infiltration cycles affected density and porosity. Lower infiltration pressure led to higher porosity ecoceramics (3.3–5.7%), which may favour catalytic performance, showing the possibility of tailoring porosity and specific surface area by modifying the number of infiltration cycles.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Hongyao Jia, Wancheng Zhou, Shichang Duan, Hanyi Nan, Fa Luo, Dongmei Zhu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉MgAl〈sub〉2-2x〈/sub〉Mn〈sub〉2x〈/sub〉O〈sub〉4〈/sub〉 (MAMO) with x = 0-0.12 was synthesized in a single-phase form by solid-state reaction. XRD analysis showed that the samples had the cubic center structure of the Fd-3 m space group. Electrical properties of the samples were studied over the temperature range of 300 K∼1073 K. The results showed that the DC conductivity (σ〈sub〉DC〈/sub〉) increased from 10〈sup〉−11〈/sup〉S/cm at 300 K (MAMO, x = 0) to 10〈sup〉-3〈/sup〉S/cm at 1073 K (MAMO, x = 0.12). The equivalent circuit of the complex impedance spectra suggested that the relaxation of charge carriers was of non-Debye type. The conduction was mainly caused by grain boundaries and the capacitance was mainly attributed to polarization. The complex permittivity values (〈em〉ε’〈/em〉 and 〈em〉ε’’)〈/em〉 were increased by two orders of magnitude with the increase in Mn content and temperature over the measured frequency range (1 Hz-1 MHz). Therefore, doping with Mn could be applied to modify the electrical properties of MAMO at high temperature.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Qi Pan, Cong Fang, Haosu Luo, Baojin Chu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The magnetoelectric effect of conventional magnetoelectric materials originates from the coupling between ferroelectricity and ferromagnetism. In this work, we demonstrate that a magnetoelectric response can also be achieved through the coupling between flexoelectricity and ferromagnetism. We show that the ferromagnetism and apparent flexoelectric response of BiFeO〈sub〉3〈/sub〉-based ceramics are greatly enhanced after an asymmetrical chemical reduction is applied to the materials. The reduction also induces an inhomogeneous magnetic property in the materials, resulting in a bending deformation and flexoelectric response under a magnetic field. A magnetoelectric response, evidenced by an abrupt change in magnetic-field-induced electrical signals near the resonance frequency of the bending deformation, is obtained in the reduced BiFeO〈sub〉3〈/sub〉-based ceramics. The present work provides an approach for designing magnetoelectric materials by exploiting the flexoelectric effect of materials.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): K. Andreev, V. Tadaion, Q. Zhu, W. Wang, Y. Yin, T. Tonnesen〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The paper discusses alternative methods to assess thermal shock in refractories. Thermal shock performance of two conventional silica bricks and two novice fused silica materials has been studied. Methods involving fracture mechanical tests of monotonic loading, repetitive thermal shock tests and cyclic strain controlled fatigue tests have been utilised. The amorphous fused silica is rather brittle. However low thermal expansion guarantees its superior thermal shock resistance. In-service crystallisation is to happen rather quickly. For crystallised fused silica of the studied morphology the tests coherently predict superior thermal shock resistance due to less brittle failure. Strain controlled fatigue test allows assessment of strain limits in the conditions of cyclic loading and thus combines the benefits of the thermal shock and monotonic fracture mechanics tests. Strain tolerance seems to be the property to correlate the results of the alternative test methods and those with the service loads.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Kangguo Wang, Huanfu Zhou, Xiaobin Liu, Wendong Sun, Xiuli Chen, Hong Ruan〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A low temperature co-fired dielectric material with low shrinkage during the sintering process can enhance the circuit design of electronic devices. Lithium aluminium borate composite ceramic with a composition of Li〈sub〉2〈/sub〉O:Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉:B〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 = 1:1:2 (abbreviated: LAB) was prepared by a traditional solid-state reaction method. These ceramics have a low sintering temperature (675–750 °C), low permittivity, and near-zero shrinkage. When the sintering temperature was 725 °C, the LAB ceramics exhibited a small shrinkage of ˜2.4% and the best microwave dielectric properties with 〈em〉ε〈sub〉r〈/sub〉〈/em〉 = 3.9, 〈em〉Q × f〈/em〉 = 35 500 GHz, and 〈em〉τ〈sub〉ƒ〈/sub〉〈/em〉= −64 ppm/°C. The LAB ceramics sintered at 700 °C have near-zero shrinkage of ˜ 0.4% and good microwave dielectric properties. The ceramics transformed from (Li〈sub〉2〈/sub〉B〈sub〉4〈/sub〉O〈sub〉7〈/sub〉 and Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉) to (Li〈sub〉2〈/sub〉Al〈sub〉2〈/sub〉B〈sub〉4〈/sub〉O〈sub〉10〈/sub〉 and Li〈sub〉4〈/sub〉Al〈sub〉4〈/sub〉B〈sub〉6〈/sub〉O〈sub〉17〈/sub〉) phases with increasing the sintering temperature, which may be the reason why they show marginal shrinkage. In addition, the ceramics could be co-fired with Ag, indicating that this material is a good candidate for low-temperature co-fired ceramic devices.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Xinchun Xie, Tianzi Wang, Zhiyong Zhou, Guofeng Cheng, Ruihong Liang, Xianlin Dong〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Bi〈sub〉4〈/sub〉Ti〈sub〉3〈/sub〉O〈sub〉12〈/sub〉 (BIT), a typical Aurivillius ceramics with high Curie temperature (〈em〉T〈sub〉c〈/sub〉〈/em〉 ˜ 675 °C), has great potential for high temperature applications. This work provides an effective method of inducing structure distortion, relieving the tetragonal strain of the TiO〈sub〉6〈/sub〉 octahedron and decreasing the concentration of oxygen vacancies to improve the piezoelectricity and temperature stability of BIT ceramics. Bi〈sub〉4〈/sub〉Ti〈sub〉2.98〈/sub〉W〈sub〉0.01〈/sub〉Nb〈sub〉0.01〈/sub〉O〈sub〉12〈/sub〉 possesses an optimum piezoelectric coefficient (〈em〉d〈/em〉〈sub〉33〈/sub〉) of 32 pC/N, a high 〈em〉T〈sub〉c〈/sub〉〈/em〉 of 655 °C and a large resistivity of 3 × 10〈sup〉6〈/sup〉 Ω·cm at 500 °C. The maximum 〈em〉d〈sub〉33〈/sub〉〈/em〉 reported here is approximately quadruple than that of pure BIT (˜7 pC/N). Moreover, the 〈em〉d〈sub〉33〈/sub〉〈/em〉 of W/Nb co-doped BIT and the 〈em〉in-situ〈/em〉 temperature stability of the compression-mode sensor present a highly stable characteristic in the range of 25–600 °C. These results imply that W/Nb-modified BIT ceramics is a promising candidate for application at high temperatures of up to 600 °C.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Ye Huang, Ying Chen, Xin Li, Genshui Wang, Liansheng Xia, Yi Liu, Yi Shen, Jinshui Shi, Xianlin Dong〈/p〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Mir Im, Woong-Hee Lee, Sang-Hyo Kweon, Chong-Yun Kang, Sahn Nahm〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉TiNbO〈sub〉5〈/sub〉 (TNO) thin films were deposited by electrophoresis at room temperature by using TNO〈sup〉−〈/sup〉 nanosheets. These TNO films exhibited a large (001) interplanar distance (1.18 nm) owing to the presence of TBA〈sup〉+〈/sup〉 between the TNO layers. The TBA〈sup〉+〈/sup〉, which were used to synthesize the TNO〈sup〉−〈/sup〉 nanosheets, were removed from the TNO film after annealing at 600 °C. Two types of structures were developed in the film annealed at 600 °C: type-1 and type-2, which revealed (001) interplanar distances of 0.52 and 0.71 nm, respectively. The TNO film annealed at 600 °C showed a dielectric constant of 48.5, low dielectric loss (0.02), and small leakage current density of 4.16 × 10〈sup〉−7〈/sup〉 A/cm〈sup〉2〈/sup〉 at 0.6 MV/cm. The dielectric properties were stable with respect to the film thickness and the applied electric field; the dielectric and insulation properties were maintained up to 300 °C. Therefore, TNO films are good candidates for high-temperature capacitors.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Xavier Vendrell, Devinder Yadav, Rishi Raj, Anthony R. West〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The ionic conductivity of flash-sintered, polycrystalline 8 mol% yttria stabilized zirconia (8YSZ) was enhanced compared with that of conventionally-sintered specimens. Flash sintering was carried out at a furnace temperature of 850 °C with an electric field of 100 V cm〈sup〉–1〈/sup〉 to initiate flash. The current density limit was varied between 60 and 100 mA mm〈sup〉–2〈/sup〉. Post-flash impedance measurements over the range 215–900 °C showed that both bulk and grain boundary conductivities had increased with the increased current density limit which was set prior to flash. The conductivity increases post-flash were ionic, not electronic, although electronic conductivity probably occurred, in addition to ionic conductivity, during flash. The conductivity increases were not attributable to sample densification or microstructural changes. The higher ionic conductivities are attributed to a change in YSZ defect structure that led to an increased concentration of mobile charge carriers; possible explanations for this are discussed.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Maxim Yaprintsev, Alexei Vasil’ev, Oleg Ivanov〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Elemental composition, crystal and grain structures, specific electrical resistivity, thermopower, thermal conductivity, and thermoelectric figure-of-merit of grained Bi〈sub〉1.9〈/sub〉Gd〈sub〉0.1〈/sub〉Te〈sub〉3〈/sub〉 compounds sintered at 〈em〉T〈sub〉S〈/sub〉〈/em〉 = 690, 720, 735, 750, 780 and 810 K have been studied. Strong 〈em〉T〈sub〉S〈/sub〉〈/em〉 – effect on the grain structure was found. Fine-grained samples with average grain size of ˜500 nm were prepared at 〈em〉T〈sub〉S〈/sub〉〈/em〉 = 690, 720 and 735 K, whereas coarse-grained samples with average grain size above 1100 nm were sintered at 〈em〉T〈sub〉S〈/sub〉〈/em〉 = 750, 780 and 810 K. Evaporation of Te takes place at high temperatures, which results in forming of anti-site defects of Bi in Te-sites. Electrical and thermal properties of the fine-grained and coarse-grained samples happened to be rather different. The highest value of the thermoelectric figure-of-merit equal to ˜ 0.55 was observed for the sample sintered at 〈em〉T〈sub〉S〈/sub〉〈/em〉 = 750 K. This temperature corresponds to transition from the fine-grained to coarse-grained samples.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Y.H. Zhang, J.J. Sun, N. Dai, Z.C. Wu, H.T. Wu, C.H. Yang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A new kind of low-temperature fired Eu〈sub〉2〈/sub〉Zr〈sub〉3〈/sub〉(MoO〈sub〉4〈/sub〉)〈sub〉9〈/sub〉 ceramic was fabricated by conventional solid-state reaction method. The mixed powders was calcined at 600 ℃ and the samples were sintered at 500 ℃ –700 ℃ for 4 h. X-ray diffraction analysis and Rietveld refinement indicated that Eu〈sub〉2〈/sub〉Zr〈sub〉3〈/sub〉(MoO〈sub〉4〈/sub〉)〈sub〉9〈/sub〉 belonged to a trigonal system with space group R-3c. Bond ionicity, lattice energy and bond energy of the ceramic were calculated by the complex chemical bond theory. Microwave dielectric properties were determined at microwave frequencies of 9.7–14.7 GHz by a network analyzer. Far infrared spectra indicated the main contribution to polarization for Eu〈sub〉2〈/sub〉Zr〈sub〉3〈/sub〉(MoO〈sub〉4〈/sub〉)〈sub〉9〈/sub〉 ceramics was the absorption of structural phonon oscillation. The ceramic sintered at 600 ℃ for 4 h exhibited the best dielectric properties with a relative permittivity (〈em〉ε〈sub〉r〈/sub〉〈/em〉) of 10.75, a quality factor (〈em〉Q·f〈/em〉) of 74,900 GHz and a temperature coefficient of resonance frequency (〈em〉τ〈sub〉f〈/sub〉〈/em〉) of -8.88 ppm/℃.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Huangyue Cai, Fangwei Guo, Guowei Wang, Xin Wang, Xiaofeng Zhao, Ping Xiao〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Densification mismatch and residual stresses of tri-layered yttria-stabilized zirconia (YSZ) membranes prepared by a non-solvent induced phase separation (NIPS) method were investigated. The tri-layered membrane consisted of sponge-like structures and finger-like voids in macroscale. The densification of the two structures were characterized to elaborate their contribution to the densification mismatch, which led to residual stresses of hundreds of megapascal retained in the sintered membranes. The profile of residual stress suggested that it was related to the strain rate mismatch within the NIPS membranes, which was further quantified with an in-situ monitored camber evolution.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Qianlong Dai, Ruzhong Zuo〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A new ultralow-loss Sr〈sub〉2〈/sub〉CeO〈sub〉4〈/sub〉 microwave dielectric ceramic was prepared via a conventional solid-state method. The X-ray diffraction and Rietveld refinement results demonstrate that pure-phase Sr〈sub〉2〈/sub〉CeO〈sub〉4〈/sub〉 ceramics belong to the orthorhombic structure with a Pbam space group. Scanning electron microscopy analysis reveals dense and homogeneous microstructure. Optimum microwave dielectric properties of ε〈sub〉r〈/sub〉 = 14.8, 〈em〉Q × f〈/em〉  = 172,600 GHz (9.4 GHz) and τ〈em〉〈sub〉f〈/sub〉〈/em〉 = -62 ppm/°C were obtained as it was sintered at 1270 °C for 4 h. In addition, the substitution of a few amount of Ti〈sup〉4+〈/sup〉 for Ce〈sup〉4+〈/sup〉 was found to have significant influences on the grain morphology, sintering behavior, phase structure and microwave dielectric properties. Among them, the Sr〈sub〉2〈/sub〉Ce〈sub〉0.65〈/sub〉Ti〈sub〉0.35〈/sub〉O〈sub〉4〈/sub〉 ceramic sintered at 1350 °C for 4 h demonstrates near-zero τ〈em〉〈sub〉f〈/sub〉〈/em〉 of -1.8 ppm/°C, ε〈sub〉r〈/sub〉 of 20.7 and 〈em〉Q〈/em〉×〈em〉f〈/em〉 of 115,550 GHz (8.1 GHz) because of its two-phase structure, showing large application potentials.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Zaoyu Shen, Limin He, Zhenhua Xu, Rende Mu, Guanghong Huang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Thermal barrier coatings (TBCs) with low thermal conductivity have triggered tremendous attention due to their promising application in the gas turbine engines. Albeit recent studies have investigated double ceramic layers (DCL) with pyrochlore (A〈sub〉2〈/sub〉B〈sub〉2〈/sub〉O〈sub〉7〈/sub〉) phase, it still remains a big challenge for controlling element content and investigating the relationship between the complex hierarchical architectures and their thermal performances. Here we describe a series of DCL La〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-ZrO〈sub〉2〈/sub〉-CeO〈sub〉2〈/sub〉 (LZC)/Y〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-stabilized ZrO〈sub〉2〈/sub〉 (YSZ) coating under different current of electron beam by electron beam-physical vapor deposition (EB-PVD). The formation of hierarchical architecture with feathery microstructure and intra-columnar have been investigated in detail. The DCL coatings achieve a high thermal cycling life and relatively low thermal conductivity at controlling current of electron beam from 1.0 A to 1.3 A. This work may open new opportunities to rationally design other promising TBCs.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉Hierarchical LZC/YSZ DCL coatings with feathery microstructure and intra-columnar pores were prepared by EB-PVD. The DCL coatings show an high thermal cycling life (excess 50% increased over the single YSZ coatings) and relatively low thermal conductivity (〈1 W/mK at 1200 °C) at controlling current of electron beam from 1.0 A to 1.3 A. The excellent thermal performances of these coatings can be attributed to the combined effect of three factors: the optimization of element content, the unique feathery microstructure and the improvement of phonon scattering. These feathery architectures by different deposition energy provide novel configurations for designing high performance TBCs.〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0955221918307490-ga1.jpg" width="430" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): D. Sola, P.B. Oliete, R.I. Merino, J.I. Peña〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Ni-doped MgO-MgSZ eutectic composites were investigated as selective emitters for thermophotovoltaic devices. MgO-MgSZ:Ni eutectic rods were directionally solidified at 25 and 500 mm/h using the laser floating zone technique. Microstructure was strongly dependent on the growth rate, the size of the eutectic phases decreased as the growth rate increased. A hardness of ∼11 GPa and a fracture toughness of ∼1.6 MPa were obtained from indentation techniques, not showing dependence on the growth rate. Flexure strength increased from ∼400 MPa in samples grown at 25 mm/h up to ∼1 GPa for those solidified at 500 mm/h, which was attributed to the decrease of the phase size. Thermal emission of eutectic composites was studied up to 1400 °C. An intense broad emission band centred in 1.5 μm matching with the sensitive region of the GaSb photoconverter was found. The selective emission was ascribed to the de-excitation of the thermally excited Ni〈sup〉2+〈/sup〉 ions.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 2 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society〈/p〉 〈p〉Author(s): Michelle Gervasio, Kathy Lu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Silicon oxycarbide (SiOC) is a unique class of materials with great potential for facile manufacturing of complex shaped high temperature parts and devices. In this study, we examine the characteristics of micron-sized ridge and rod patterns of SiOC created by imprint lithography. Feature fidelity, shape change, and shrinkage are studied as a function of pyrolysis condition and feature size. All the features have acceptable surface fidelity under the pyrolysis conditions studied. However, pronounced rounding and flattening of patterned features are observed as the pyrolysis temperature increases or the feature size decreases. Based on the Kelvin and Gibbs-Thomson equations, we can predict the feature evolution and show that the feature rounding and flattening are due to surface diffusion and evaporation-condensation. As a result, the features also have more linear shrinkage than the bulk.〈/p〉〈/div〉

Description: 〈p〉Publication date: June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 6〈/p〉 〈p〉Author(s): Hui Sun, Yuxi Lu, Xi Xie, Tiaoshu Yao, Zirou Xu, Yan Wang, Xiaobing Chen〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Sr〈em〉〈sub〉x〈/sub〉〈/em〉Bi〈sub〉6-〈/sub〉〈em〉〈sub〉x〈/sub〉〈/em〉Fe〈sub〉1-〈/sub〉〈em〉〈sub〉x〈/sub〉〈/em〉〈sub〉/2〈/sub〉Co〈sub〉1-〈/sub〉〈em〉〈sub〉x〈/sub〉〈/em〉〈sub〉/2〈/sub〉Ti〈sub〉3+〈/sub〉〈em〉〈sub〉x〈/sub〉〈/em〉O〈sub〉18〈/sub〉 (〈em〉x〈/em〉 = 0, 0.25, 0.5, 0.75, 1)(SBFCT-〈em〉x〈/em〉) ceramics were prepared by the sol-gel auto-combustion method, and their microstructures, ferroelectric, magnetic and dielectric properties were investigated. All samples show layer-perovskited Aurivillius phase, which confirms that Sr doping does not affect the structure of SBFCT ceramics. The coexistence of ferroelectricity and ferromagnetism were observed at room temperature for all the samples. The largest remnant polarization (2〈em〉P〈/em〉〈sub〉r〈/sub〉 ˜ 17.4 〈em〉μ〈/em〉C/cm〈sup〉2〈/sup〉) is observed in the SBFCT-1 ceramic, while the SBFCT-0.5 ceramic shows the highest remnant magnetization (2〈em〉M〈/em〉〈sub〉r〈/sub〉 ˜ 0.74 emu/g). To explore the effect of valance states of magnetic ions on the properties, we analysed the content variation of Fe〈sup〉2+〈/sup〉, Co〈sup〉2+〈/sup〉, and oxygen vacancies by the X-ray photoelectron spectroscopy results. Furthermore, dielectric anomalies have been found around 400 K, which can be ascribed to the hopping process of oxygen vacancies. The effects of Sr and Ti substitution on ferroelectric and magnetic properties have been investigated and discussed.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Lisheng Gao, Sinan Dursun, A. Erkan Gurdal, Eberhard Hennig, Shujun Zhang, Clive A. Randall〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉High-performance lead-free piezoelectrics are of interest as alternate materials to confront potential legislative actions on lifting the exemption on lead-based piezoelectric materials. In this work, we demonstrated a highly textured commercial-grade Li- and Ta- modified (Na, K)NbO〈sub〉3〈/sub〉 (NKN) lead-free piezoceramic that was sintered under low oxygen partial pressure (〈em〉pO〈/em〉〈sub〉〈em〉2〈/em〉〈/sub〉) atmospheres using the solid state template grain growth (TGG) method. It was found that a moderate low 〈em〉pO〈/em〉〈sub〉〈em〉2〈/em〉〈/sub〉 condition not only facilitated the reactive template grain growth but also lowered the temperature required for such process. Highly textured NKN with a converse piezoelectric coefficient 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.gif" overflow="scroll"〉〈msubsup〉〈mi〉d〈/mi〉〈mn〉33〈/mn〉〈mi〉*〈/mi〉〈/msubsup〉〈mo〉≈〈/mo〉〈mn〉680〈/mn〉〈mtext〉 〈/mtext〉〈mi〉p〈/mi〉〈mi〉m〈/mi〉〈mtext〉 〈/mtext〉〈msup〉〈mi〉V〈/mi〉〈mrow〉〈mo〉-〈/mo〉〈mn〉1〈/mn〉〈/mrow〉〈/msup〉〈/math〉 was obtained, this remarkable piezoelectric property can be explained by the position of the polymorphic phase boundary of NKN. With considerations on both performance and cost, this work not only presented the potential for NKN to meet the requirement of commercial applications, but also provided an effective processing strategy to utilize low cost base metal inner electrodes in the future.〈/p〉〈/div〉

Description: 〈p〉Publication date: May 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 5〈/p〉 〈p〉Author(s): Krishna Praveen Jonnalagadda, Robert Eriksson, Xin-Hai Li, Ru Lin Peng〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Models that can predict the life of thermal barrier coatings (TBCs) during thermal cycling fatigue (TCF) tests are highly desirable. The present work focuses on developing and validating a simplified model based on the relation between the energy release rate and the TCF cycles to failure. The model accounts for stresses due to thermal mismatch, influence of sintering, and the growth of TGO (alumina and other non-protective oxides). The experimental investigation of TBCs included; 1) TCF tests at maximum temperatures of 1050 °C, 1100 °C, 1150 °C and a minimum temperature of 100 °C with 1 h and 5 h (1100 °C) hold times. 2) Isothermal oxidation tests at 900, 1000 and 1100 °C for times up to 8000 h. The model was calibrated and validated with the experimental results. It has been shown that the model is able to predict the TCF life and effect of hold time with good accuracy.〈/p〉〈/div〉

Description: 〈p〉Publication date: May 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 5〈/p〉 〈p〉Author(s): Fen Qin, Hee-Suk Roh, Salim Caliskan, Seongha Lee, Sun-Dong Kim, Sang Kook Woo, Jung-Kun Lee〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We studied crystallization, grain growth and electric properties of La〈sub〉0.8〈/sub〉Sr〈sub〉0.2〈/sub〉MnO〈sub〉3〈/sub〉 (LSM) ceramics which were produced using the microwave-treatment. While co-precipitated nanoparticles remain mainly amorphous, the microwave irradiated particles are crystallized into LSM and La〈sub〉2〈/sub〉Mn〈sub〉2〈/sub〉O〈sub〉7〈/sub〉 at 550 °C, due to higher dielectric polarizability of La. This, in turn, decreases the amount of the second phase La〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 in calcined powder and promotes the growth of perovskite grains during sintering at 1400 °C. Larger grains of LSM ceramics lower the activation energy of small polaron hopping from 0.35 eV to 0.24 eV and increases high-temperature electric conductivity. In addition, high crystallinity of LSM ceramics from the microwave-treatment suppresses a chemical reaction with ZrO〈sub〉2〈/sub〉 and NiO in a temperature range of 900 – 1100 °C under oxidizing and reducing ambiances. These results show that LSM ceramics from the microwave-assisted reaction meet requirements for an interconnect layer for solid oxide electrolysis cells.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Jiayu Xie, Manwen Yao, Wenbin Gao, Zhen Su, Xi Yao〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A novel core-shell structured Pb〈sub〉0.91〈/sub〉La〈sub〉0.06〈/sub〉(Zr〈sub〉0.552〈/sub〉Sn〈sub〉0.368〈/sub〉Ti〈sub〉0.08〈/sub〉)O〈sub〉3〈/sub〉@PbO–B〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-SiO〈sub〉2〈/sub〉-Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-ZnO-MnO〈sub〉2〈/sub〉 (PLZST@PBSAZM) antiferroelectric particles were successfully fabricated via sol-gel method. As expected, the sintering temperature was notably reduced from 1250 ºC to 1100 ºC with the increasing glass contents. More importantly, the breakdown strengths of PLZST@PBSAZM ceramics were significantly increased from 252 kV/cm to 402 kV/cm. As a result, the energy density was up to 7.4 J/cm〈sup〉3〈/sup〉 with 1 wt.% of coating glass content, a 55.3% enhancement over the pure PLZST (4.7 J/cm〈sup〉3〈/sup〉). Furthermore, the simulations of electric field distribution provided a powerful evidence that the enhancement of the breakdown strength was induced by the core-shell structure, since the glass coating layer could not only undertake the most of electric field, but also impede the grain growth to achieve the smaller grains, which led to the reduction of electric field intensity on the grain cores.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Mingchao Wang, Xue Dong, Qingjun Zhou, Zhaojie Feng, Yunlong Liao, Xiaomeng Zhou, Mingrun Du, Yuqing Gu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Mullite whiskers were successfully in-situ synthesized in phosphate-based adhesive by taking Si and Al(OH)〈sub〉3〈/sub〉 as reaction sources and AlF〈sub〉3〈/sub〉 as the catalytic initiator. After calcination at 1300 °C, both strength and toughness of whisker-growth adhesive got greatly improved, which were increased by 75% and 156%, respectively. The bonding strength was enhanced to 23.8 MPa, which was close to some hot preceramic polymer-based adhesives. An approximate yield stage appeared on its corresponding loading-curve, showing unprecedented toughness and high damage capacity. In addition, the residual rate of bonding strength still maintained 63% after 20 thermal cycles (room temperature-1300 °C).〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Yongzhao Peng, Jiasong Zhong, Xinyue Li, Jiangkun Chen, Junjie Zhao, Xvsheng Qiao, Daqin Chen〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Glass ceramic has been regarded as an alternative to traditional bulk materials such as single crystal and transparent ceramic. The nucleation/growth behavior of glass ceramic via crystallization is an important topic but is seldom studied so far. In the present work, a series of La〈sup〉3+〈/sup〉-based oxyfluoride aluminosilicate glasses are designed to understand their nanocrystallization processes upon heating. Impressively, controllable LaF〈sub〉3〈/sub〉, α-NaLaF〈sub〉4〈/sub〉 and β-NaLaF〈sub〉4〈/sub〉 phase-competitive crystallization in glasses is achieved and structural/spectroscopic characterizations confirm the key role of Al/Si ratio to determine the release of Na〈sup〉+〈/sup〉 ions from glass network to participate in crystallization and phase transformation. Furthermore, the developed glass ceramics are evidenced to be ideal hosts for lanthanide dopants (such as Eu〈sup〉3+〈/sup〉 and Yb〈sup〉3+〈/sup〉/Er〈sup〉3+〈/sup〉), which can effectively incorporate into the precipitated fluoride crystal lattices by substituting La〈sup〉3+〈/sup〉 ions. As a consequence, incoherent LED-excitable upconverting devices are constructed to demonstrate their promising application as emitting media in display.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0955221918307544-ga1.jpg" width="284" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Meimanat Rahmani, Christian Pithan, Rainer Waser〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A comprehensive study was performed in order to find the effect of different calcination and sintering conditions on the physical properties of calcium manganite ceramics in dependence of temperature 〈em〉T〈/em〉 and partial pressure of oxygen 〈em〉p〈/em〉(O〈sub〉2〈/sub〉). The eventual formation of oxygen vacancies during sintering was investigated and the results were confirmed by monitoring the release of oxygen using a ZrO〈sub〉2〈/sub〉 oxygen sensor. The phase transition behavior was studied using thermogravimetric analysis (TGA) in a wide range of 〈em〉p〈/em〉(O〈sub〉2〈/sub〉) ≈ 10〈sup〉−1〈/sup〉 MPa down to 10〈sup〉-19〈/sup〉 MPa at high temperatures accompanied by dilatometry- and XRD-measurements. Furthermore, the present study reveals for the first time a way for reducing and preventing crack formation that may occur during sintering. The present systematic research provides essential fundamental information before performing electrical measurements necessary in order to understand important factors about charge carriers and electrical transport mechanism.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Isao Kagomiya, Tomoki Murayama, Kyosuke Tsunekawa, Ken-ichi Kakimoto, Yusuke Ogura〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A typical mixed conductive oxide with high oxygen permeability is La〈sub〉0.6〈/sub〉Sr〈sub〉0.4〈/sub〉Co〈sub〉0.2〈/sub〉Fe〈sub〉0.8〈/sub〉O〈sub〉3-〈/sub〉〈em〉〈sub〉δ〈/sub〉〈/em〉 (LSCF), which is applicable to oxygen separation membrane and to cathodes for solid oxide fuel cells. However, Sr and Co included in the LSCF lower its stability when kept at elevated temperatures. La〈sub〉1-〈/sub〉〈em〉〈sub〉x〈/sub〉〈/em〉Ca〈em〉〈sub〉x〈/sub〉〈/em〉FeO〈sub〉3-〈/sub〉〈em〉〈sub〉δ〈/sub〉〈/em〉(LCF) is a good candidate of mixed conductive oxides with no Sr and Co ions. This study investigated systematic details of crystalline phase, electrical conductivity, and oxygen permeability as functions of the Ca content in the LCF. The 〈em〉x〈/em〉 = 0.3–0.4 samples with perovskite structure reveal higher electrical conductivity and higher oxygen permeation flux 〈em〉J〈/em〉〈sub〉O2〈/sub〉 among the investigated LCF. Particularly, the 〈em〉J〈/em〉〈sub〉O2〈/sub〉 of the 〈em〉x〈/em〉 = 0.35 and 0.4 are higher than that of the LSCF, proposing that the samples replace the LSCF. Larger specific free volumes in 〈em〉x〈/em〉 = 0.3–0.4 are a possible main reason for higher vacancy mobility, resulting in higher 〈em〉J〈/em〉〈sub〉O2〈/sub〉.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Zhilin Tian, Jie Zhang, Tianyin Zhang, Xiaomin Ren, Wanpeng Hu, Liya Zheng, Jingyang Wang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Rare earth (RE) silicates X1-RE〈sub〉2〈/sub〉SiO〈sub〉5〈/sub〉 (RE = La, Nd, Sm, Eu, and Gd) are comprehensively investigated as promising thermal barrier coating candidates. The mechanical, thermal, and corrosion resistance properties are evaluated by theoretical exploration and experimental measurement. Mechanical properties and corrosion resistance to calcium-magnesium alumino-silicates (CMAS) melts of X1-RE〈sub〉2〈/sub〉SiO〈sub〉5〈/sub〉 are linearly correlated with ionic radius of RE elements. Elastic moduli increase with the decrease of ionic radius of RE〈sup〉3+〈/sup〉. X1-RE〈sub〉2〈/sub〉SiO〈sub〉5〈/sub〉 with larger RE〈sup〉3+〈/sup〉 exhibits better resistance to molten melts corrosion. For thermal properties, they are not obviously sensitive to RE species. All X1-RE〈sub〉2〈/sub〉SiO〈sub〉5〈/sub〉 demonstrate low thermal conductivities and their magnitudes are significantly modified by concentration of defects. Thermal expansion coefficients of X1-RE〈sub〉2〈/sub〉SiO〈sub〉5〈/sub〉 are more or less close and are compatible with the value of superalloy. The results highlight X1-RE〈sub〉2〈/sub〉SiO〈sub〉5〈/sub〉 as potential thermal barrier coating candidates with overall properties.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Petr Skalka, Karel Slámečka, Edgar B. Montufar, Ladislav Čelko〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Direct ink writing is a popular method for fabrication of scaffolds, yet its widespread usage in clinical practice requires guarantee of compatibility of a scaffold with bone tissues. Mechanical compatibility is mandatory to prevent stress shielding and is expressed using the difference between effective elastic constants (EECs) of a scaffold and tissue. In this paper, the solution for EECs of a calcium phosphate scaffold is derived for any combination of input parameters, inclusive of the contact radius at the joints, a feature arising mainly from the rheological properties of the ink. The model was validated by the comparison with data from the literature and those obtained from tests on produced scaffolds and monoliths. The contact radius significantly influences the elastic response and local stresses in the structure. The inverse solution can be used for estimation of bulk properties and is also helpful for the quality assessment of fabrication process.〈/p〉〈/div〉

Description: 〈p〉Publication date: May 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 5〈/p〉 〈p〉Author(s): Mirela Dragomir, Mojca Otoničar, Marko Vrabelj, Lovro Fulanović, Silvo Drnovšek, Tadej Rojac, Barbara Malič〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A systematic investigation of the seeding effects on the mechanochemical synthesis of lead magnesium niobate – lead titanate 0.9Pb(Mg〈sub〉1/3〈/sub〉Nb〈sub〉2/3〈/sub〉)O〈sub〉3〈/sub〉–0.1PbTiO〈sub〉3〈/sub〉 (PMN–10PT), one of the most studied relaxor-ferroelectric material for electrocaloric applications, is reported. The perovskite crystallisation process was followed by X-ray diffraction using the Rietveld refinement method and transmission electron microscopy. Compared to the mixed-oxides case which requires 143 h of high-energy milling, the milling time needed to obtain a phase-pure PMN–10PT perovskite using PT seeds is reduced almost twice. The presence of PT seeds leads to faster transitions from the amorphous to pyrochlore and to perovskite phases compared to the mixed-oxides case. A sintering study demonstrates, for the first time, that a second, metastable, pyrochlore phase is taking part in the processes of perovskite formation. The PMN–10PT ceramic prepared from the PT-seeded powder exhibits electrocaloric properties comparable to reported values for PMN–10 PT prepared from oxides.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): M.P. Popov, S.F. Bychkov, N.V. Bulina, A.P. Nemudry〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Oxygen-permeable hollow fiber membranes with the composition Ba〈sub〉0.5〈/sub〉Sr〈sub〉0.5〈/sub〉Co〈sub〉0.78〈/sub〉W〈sub〉0.02〈/sub〉Fe〈sub〉0.2〈/sub〉O〈sub〉3-〈/sub〉〈em〉〈sub〉δ〈/sub〉〈/em〉 were used to demonstrate the possibility of direct AC heating for 〈em〉in situ〈/em〉 high-temperature X-Ray diffraction (HT-XRD) of the hollow fiber membranes during their operation. 〈em〉In situ〈/em〉 HT-XRD measurements showed that under stationary conditions of oxygen flow through the hollow fiber membrane, the surface of the membrane from the permeate side (〈em〉p〈/em〉O〈sub〉2.2〈/sub〉) is determined by the oxygen partial pressure from the feed side (〈em〉p〈/em〉O〈sub〉2.1〈/sub〉), which allows to significantly reduce the operational requirements to the material of the hollow fiber membrane.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Apurv Dash, Byung-Nam Kim, Jens Klimke, Jef Vleugels〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Targeting higher toughness transparent ceramics, tetragonal (3 mol % yttria) and cubic (8 mol % yttria) ZrO〈sub〉2〈/sub〉 starting powder mixtures were densified by spark plasma sintering (SPS) in vacuum at 1100 °C and post hot isostatic pressing (HIP) in argon at 1100 °C. The influence of the ultra-fine microstructure and phase composition on the fracture resistance and light transmission in the visible and infra-red range was assessed. Of special interest was the influence of a thermal annealing step in air on the transparency of the SPS and SPS-HIP ceramics.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Zhi-Gang Wang, Jia-Hu Ouyang, Yong-Hui Ma, Yu-Jin Wang, Ling-Yun Xie, Abdelkhalek Henniche, Zhan-Guo Liu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This present work explores initially the feasibility of producing 〈em〉in-situ〈/em〉 surface nanoeutectic Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-ZrO〈sub〉2〈/sub〉(Y〈sub〉2〈/sub〉O〈sub〉3〈/sub〉) (SNAZ) ceramics via the oxyacetylene flame remelting (OAFR) process. Singular cellular nanoeutectics consist of nanoscale lamellae, which prevail in the samples formed under different irradiation times. Ultrafine nanoeutectics are achieved by prolonging the irradiation time, and their formation mechanisms associated with eutectic refinement are proposed to obtain a better understanding on the melt thermal history and microstructural inheritance. The enhanced nucleation undercooling is the essential mechanism associated with the microstructural refinement. SNAZ formed by the OAFR-based rapid solidification seem to offer an inexpensive route to realize 〈em〉in-situ〈/em〉 microstructure tailoring or surface shaping.〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 4〈/p〉 〈p〉Author(s): Weiya Zhu, Yang Liu, Kang Guan, Cheng Peng, Jianqing Wu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 membrane support with both enhanced permeability and strength was fabricated by introducing zirconia fiber (ZrO〈sub〉2(f)〈/sub〉). Effects of the ZrO〈sub〉2(f)〈/sub〉 content and sintering temperature on the open porosity, shrinkage rate, microstructure, water permeance, bending strength and pore size of the support were investigated. Results reveal that apart from fiber reinforcement, ZrO〈sub〉2(f)〈/sub〉 was found to promote open porosity and permeability by changing pore morphology and reducing flow resistance. However, it damages the porous structure if the sintering temperature is excessive. Compared with the un-added sample, the bending strength and water permeance of the support with a ZrO〈sub〉2(f)〈/sub〉 addition of 4 wt% sintered at 1550 °C increased by 261% and 52%, respectively. The modified support meets the requirement for more demanding operation conditions and may achieve the objects of miniaturizing and lightening the final products.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 16〈/p〉 〈p〉Author(s): Yuying Zhang, Chun-Yen Hsu, Prashant Karandikar, Chaoying Ni〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Diamond/SiC composites have attracted considerable research interests due to their outstanding properties sought for a wide range of applications. Among a few techniques used for the fabrication of diamond/SiC composites, molten Si infiltration is an approach highly favored due to its cost-effectiveness and process flexibility. This study critically evaluated the interfacial zone surrounding the diamond in a reaction bonded (RB) diamond/SiC composite. XRD suggests that the composite consists of diamond, α-SiC, β-SiC, Si, and graphite. TEM reveals that a thin layer of graphite surrounds the diamond grain and it appears to form through a process of diamond graphitization and amorphous carbon transformation during the fabrication. In addition, a carbon dissolution and saturation process is proposed as a predominant mechanism for the formation of nano-crystalline SiC near the interface as well as the defects inside the SiC grits. A minor Al〈sub〉4〈/sub〉C〈sub〉3〈/sub〉 phase is occasionally detected near the interface region.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 16〈/p〉 〈p〉Author(s): Xingyuan Zhao, Maanas Togaru, Qianying Guo, Christopher R. Weinberger, Leslie Lamberson, Gregory B. Thompson〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper explores the fracture behavior of niobium carbides of varying compositions between NbC〈sub〉1.0〈/sub〉 and NbC〈sub〉0.5〈/sub〉. The surface crack in flexure (SCF) method was used to evaluate the fracture toughness as a function of carbon concentration. Additionally, hardness measurements were conducted with a Knoop indenter, and X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to identify the phase content and microstructures. As the carbon content decreased, the hardness increased from 8 GPa for NbC〈sub〉1.0〈/sub〉 to 12 GPa for NbC〈sub〉0.5〈/sub〉 and the fracture toughness decreased from 2.5 MPa 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈msqrt〉〈mi mathvariant="bold"〉m〈/mi〉〈/msqrt〉〈/math〉 to 0.44 MPa 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈msqrt〉〈mi mathvariant="bold"〉m〈/mi〉〈/msqrt〉〈/math〉. Notably, the NbC〈sub〉0.67〈/sub〉 sample exhibited a secondary precipitate lath-like microstructure with the laths indexed to β-Nb〈sub〉2〈/sub〉C and a K〈sub〉IC〈/sub〉 near 2 MPa 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈msqrt〉〈mi mathvariant="bold"〉m〈/mi〉〈/msqrt〉〈/math〉. Though similar lath like structures in tantalum carbides have been reported to yield a K〈sub〉IC〈/sub〉 of approximately 15 MPa 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈msqrt〉〈mi mathvariant="bold"〉m〈/mi〉〈/msqrt〉〈/math〉, the laths in these two materials have fundamentally different structures where bonding in the former is comprised of β-Nb〈sub〉2〈/sub〉C and the latter of ζ-Ta〈sub〉4〈/sub〉C〈sub〉3-x〈/sub〉. This results in the observed different fracture properties, which can be explained through concepts of microstructural toughening.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 16〈/p〉 〈p〉Author(s): Yuting Peng, Zhi Tan, Jiao An, Jianguo Zhu, Qiming Zhang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The ferroelectric and piezoelectric properties of orthorhombic K〈sub〉1-〈/sub〉〈em〉〈sub〉x〈/sub〉〈/em〉Na〈em〉〈sub〉x〈/sub〉〈/em〉NbO〈sub〉3〈/sub〉 (KNN) piezoceramics with various Na concentrations 〈em〉x〈/em〉 are studied by the first-principles calculations. The spontaneous polarization of KNN single crystals increases monotonically with Na concentrations, indicating an enhanced ferroelectricity in KNN. Moreover, the averaged shear, transverse and longitudinal piezoelectric coefficient 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.gif" overflow="scroll"〉〈msubsup〉〈mrow〉〈mover accent="true"〉〈mrow〉〈mtext〉d〈/mtext〉〈/mrow〉〈mo mathvariant="normal"〉-〈/mo〉〈/mover〉〈/mrow〉〈mn〉15〈/mn〉〈mrow〉〈mtext〉*〈/mtext〉〈/mrow〉〈/msubsup〉〈/math〉, 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si4.gif" overflow="scroll"〉〈msubsup〉〈mrow〉〈mover accent="true"〉〈mrow〉〈mtext〉d〈/mtext〉〈/mrow〉〈mo mathvariant="normal"〉-〈/mo〉〈/mover〉〈/mrow〉〈mn〉31〈/mn〉〈mrow〉〈mtext〉*〈/mtext〉〈/mrow〉〈/msubsup〉〈/math〉 and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si5.gif" overflow="scroll"〉〈msubsup〉〈mrow〉〈mover accent="true"〉〈mrow〉〈mtext〉d〈/mtext〉〈/mrow〉〈mo mathvariant="normal"〉-〈/mo〉〈/mover〉〈/mrow〉〈mn〉33〈/mn〉〈mrow〉〈mtext〉*〈/mtext〉〈/mrow〉〈/msubsup〉〈/math〉 of KNN piezoceramics are calculated from the data of KNN single crystals to show that piezoelectricity of KNN piezoceramics positively correlates with Na concentrations and exhibits the best performance at 〈em〉x〈/em〉 = 0.5625, which agrees well with the available experimental data. At this concentration, 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.gif" overflow="scroll"〉〈msubsup〉〈mrow〉〈mover accent="true"〉〈mrow〉〈mtext〉d〈/mtext〉〈/mrow〉〈mo mathvariant="normal"〉-〈/mo〉〈/mover〉〈/mrow〉〈mn〉15〈/mn〉〈mrow〉〈mtext〉*〈/mtext〉〈/mrow〉〈/msubsup〉〈/math〉, 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si4.gif" overflow="scroll"〉〈msubsup〉〈mrow〉〈mover accent="true"〉〈mrow〉〈mtext〉d〈/mtext〉〈/mrow〉〈mo mathvariant="normal"〉-〈/mo〉〈/mover〉〈/mrow〉〈mn〉31〈/mn〉〈mrow〉〈mtext〉*〈/mtext〉〈/mrow〉〈/msubsup〉〈/math〉 and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si5.gif" overflow="scroll"〉〈msubsup〉〈mrow〉〈mover accent="true"〉〈mrow〉〈mtext〉d〈/mtext〉〈/mrow〉〈mo mathvariant="normal"〉-〈/mo〉〈/mover〉〈/mrow〉〈mn〉33〈/mn〉〈mrow〉〈mtext〉*〈/mtext〉〈/mrow〉〈/msubsup〉〈/math〉 of orthorhombic KNN piezoceramics reach maximum, which are 1.13, 1.79 and 0.85 times larger than those of KNbO〈sub〉3〈/sub〉 piezoceramics, respectively. This work provides a better understanding to the effect of Na concentrations on the enhanced ferroelectricity and piezoelectricity in the KNN piezoceramics.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 16〈/p〉 〈p〉Author(s): Meng Shen, Zhaoyao Hu, Yaqin Qiu, Shiyong Qiu, Ming-yu Li, Guangzu Zhang, Shujun Zhang, Zhengbao Yang, Fumitaka Kagawa, Shenglin Jiang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The pyroelectric effect provides an efficient route to convert low-grade waste heat into electricity. (Bi〈sub〉0.5〈/sub〉Na〈sub〉0.5〈/sub〉)TiO〈sub〉3〈/sub〉-based ceramic is one of the most attractive lead-free pyroelectric candidates due to its high polarization. However, the low breakdown strength (BDS) restricts its ability to achieve a high polarization, hindering the application for thermal energy harvesting based on the Olsen cycle. In this work, by incorporation of AlN into BNT-BZT ceramics to form the BNT-BZT: AlN composites, the BDS is enhanced from 160 kV cm〈sup〉−1〈/sup〉 to 260 kV cm〈sup〉−1〈/sup〉, leading to a high energy density of 1.54 J cm〈sup〉−3〈/sup〉 which is ∼5 times that of the pristine BNT-BZT. The reason for the high energy harvesting performance is due to the addition of AlN that can depress the conductivity of the matrix, resulting in the high BDS that permits high electric fields to be applied on the samples to induce high polarization that changes pronouncedly with temperature.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 16〈/p〉 〈p〉Author(s): Wen Wang, Yongping Pu, Xu Guo, Ruike Shi, Yu Shi, Mengdie Yang, Jingwei Li, Xin Peng, Yang Li〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Ca〈sub〉1-〈/sub〉〈em〉〈sub〉x〈/sub〉〈/em〉Sr〈em〉〈sub〉x〈/sub〉〈/em〉Ti〈sub〉1-〈/sub〉〈em〉〈sub〉y〈/sub〉〈/em〉Zr〈em〉〈sub〉y〈/sub〉〈/em〉O〈sub〉3〈/sub〉 (0.40 ≤ 〈em〉x〈/em〉 ≤ 0.60, 0.1 ≤ 〈em〉y〈/em〉 ≤ 0.4) ceramic samples were fabricated by conventional solid state method. The microstructure of ceramic samples were studied by XRD and SEM, and the influence of Zr〈sup〉4+〈/sup〉 doping on the electric properties and energy storage performances were systematically studied. The results showed that the introduction of Zr〈sup〉4+〈/sup〉 results in an inhibition of interfacial polarization and enhancement of grain boundary barrier effect. Ca〈sub〉0.5〈/sub〉Sr〈sub〉0.5〈/sub〉Ti〈sub〉1-〈/sub〉〈em〉〈sub〉y〈/sub〉〈/em〉Zr〈em〉〈sub〉y〈/sub〉〈/em〉O〈sub〉3〈/sub〉 ceramic samples exhibit excellent energy storage properties, with breakdown strength being on the order of 390 kV/cm versus 280 kV/cm for the counterpart Ca〈sub〉0.5〈/sub〉Sr〈sub〉0.5〈/sub〉TiO〈sub〉3〈/sub〉 ceramic samples, together with energy efficiency above 95%. Meanwhile, a maximum breakdown strength of 390 kV/cm, a high energy storage density of 2.05 J/cm〈sup〉3〈/sup〉 and an ultrahigh energy efficiency of 85% at high temperature of 125 ℃ were obtained in the sample with 〈em〉y〈/em〉 = 0.1 as well, indicating it as a good candidate for linear energy storage fileds.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 16〈/p〉 〈p〉Author(s): Kristina Hellström, Yngve Ögren, Melina da Silva, Monica Cristea, Erik Ström〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉A Mo(Si, Al)〈sub〉2〈/sub〉 based composite was pre-oxidized to establish an alumina scale on the material surface. Thereafter, the corrosion behavior of the composite was examined at 1700 °C for up to 24 h in 95% N〈sub〉2〈/sub〉 + 5% H〈sub〉2〈/sub〉.〈/p〉 〈p〉The weight change was followed by recording the material weight before and after exposure. The crystalline corrosion products were analyzed with X-ray diffraction (XRD) and the microstructure of the cross sectioned material was characterized using scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS).〈/p〉 〈p〉It was shown that AlN and Al〈sub〉5〈/sub〉O〈sub〉6〈/sub〉N layers developed on top of the pre-oxidized alumina layer and alumina threads develop out from the specimen surface. The accompanied aluminum consumption converts the substrate Mo(Si,Al)〈sub〉2〈/sub〉 into Mo〈sub〉5〈/sub〉Si〈sub〉3〈/sub〉 immediately below the alumina scale to the extent that the Mo〈sub〉5〈/sub〉Si〈sub〉3〈/sub〉 becomes porous underneath the alumina scale. Corrosion mechanisms are discussed with the support of thermodynamic calculations.〈/p〉 〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 16〈/p〉 〈p〉Author(s): Vladimír Prajzler, Stanislav Průša, Karel Maca〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Rapid pressure-less sintering of nanoparticle yttria-stabilized zirconia (YSZ) can result in the formation of a gradient structure characterized by an airtight layer at the surface and interconnected porosity inside the sintered compact. This structure constrains a sample from further shrinkage and limits its final density. In this study, we rapidly sintered green bodies prepared from four commercially available YSZ powder grades, all with a particle size of 60 nm, but with different chemical compositions. We have shown that all powders contained residual chlorine which is responsible for the above mentioned core-shell structure of rapidly sintered samples rather than low thermal conductivity of zirconia. The only sample without this gradient structure was prepared from the powder grade with an increased amount of binder that helped to reduce the chlorine content during binder burnout. The ultimate way for elimination of negative chlorine effect was annealing the sample at 1000 °C prior to rapid sintering.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 15〈/p〉 〈p〉Author(s): Meimanat Rahmani, Christian Pithan, Rainer Waser〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A comprehensive overview is provided about the role of bulk conductivity contributions in compounds of the composition Yb〈sub〉x〈/sub〉Ca〈sub〉1-x〈/sub〉MnO〈sub〉3〈/sub〉 (0–10 at. % Yb-dopant concentration). For this purpose, in-situ impedance spectroscopy was successfully employed at different temperatures (−100 up to 300 °C) and frequencies (1 Hz–1 MHz). These experiments reveal the main role of grain boundaries as well as electronic and ionic contributions in conductivity. The contribution of different resistance components in electric transport properties were proposed on the base of a double-Schottky-barrier model. Migration of oxygen vacancies and their participation in conductivity were studied and the results are confirmed by observing oxygen released using a ZrO〈sub〉2〈/sub〉 oxygen sensor during dilatometry measurements in a wide range of temperatures.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 15〈/p〉 〈p〉Author(s): Ji-Hoon Min, Jaehyung Lee, Dang-Hyok Yoon〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Transparent polycrystalline aluminum oxynitride (γ-AlON) was fabricated by the pressureless two-step sintering of α-Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 and AlN after adding a small amount of MgO and Y〈sub〉2〈/sub〉O〈sub〉3〈/sub〉. The process was based on two assumptions. The first was the utilization of AlN-deficient non-stoichiometric composition to increase the cationic vacancies and the second was the selection of the 1st step sintering temperature that suppresses the formation of γ-AlON phase to achieve a high density after the 2nd sintering step. The 1st and 2nd sintering steps were performed at 1610–1650 and 1940–1990 °C, respectively, for 10 h in a 2.5 atmospheric nitrogen pressure, and the optimal sintering conditions were determined. The fabricated γ-AlON showed a mean grain size of 164–248 μm without the presence of significant scattering centers, where the sample prepared using an optimal condition revealed a very high transmittance of 84.7% along with comparable mechanical properties.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 15〈/p〉 〈p〉Author(s): Zhuoqun Fang, Ying Chen, Xin Li, Wei Huang, Liansheng Xia, Yi Shen, Genshui Wang, Xianlin Dong〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Linear dielectric ceramics have received much attention due to high power density, fast discharge speed and ultralow dielectric loss, which are expected as promising candidates for the pulsed power system applications. However, their relatively low dielectric breakdown strength usually cannot meet the requirements of practical application. In this work, we adopt hot-press sintering method to enhance the dielectric breakdown strength of the TiO〈sub〉2〈/sub〉-SiO〈sub〉2〈/sub〉-Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 based ceramics, and the dielectric breakdown strength reaches 77.5 kV/mm, which is 1.8 times as large as samples prepared by conventional sintering method. The effect of different sintering methods on microstructure, dielectric properties and dielectric breakdown strength is investigated. The improvement of dielectric breakdown strength can be ascribed to improved bulk density, smaller grain size, and reduced reduction of Ti〈sup〉4+〈/sup〉 to Ti〈sup〉3+〈/sup〉, associated with the applied external pressure and lower sintering temperature. Eventually, large power density (18.20 MW/cm〈sup〉3〈/sup〉) is obtained in pulse overdamped discharge circuit. Meanwhile, the stored energy is also released in a short time (about 11.3 ns to release 90% of saturated energy density value).〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 15〈/p〉 〈p〉Author(s): Natalia Pawlik, Barbara Szpikowska-Sroka, Tomasz Goryczka, Maciej Zubko, Józef Lelątko, Wojciech A. Pisarski〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, the transparent oxyfluoride glass-ceramic materials containing YF〈sub〉3〈/sub〉:Eu〈sup〉3+〈/sup〉 nanocrystals were fabricated via controlled ceramization of precursor xerogels at relatively low temperature T = 350 °C. The formation of YF〈sub〉3〈/sub〉 nanocrystalline phase from Y(CF〈sub〉3〈/sub〉COO)〈sub〉3〈/sub〉 was verified based on X-ray diffraction (XRD) measurements as well as high-resolution transmittance electron microscopy (HR-TEM). Based on IR-ATR spectroscopy the functional groups inside sol-gel structures were identified. The optical properties of Eu〈sup〉3+〈/sup〉 ions in fabricated sol-gel samples were investigated based on photoluminescence excitation and emission spectra as well as luminescence decay analysis of the 〈sup〉5〈/sup〉D〈sub〉0〈/sub〉 excited level. Upon excitation at near-UV illumination, λ〈sub〉exc〈/sub〉 = 393 nm, the series of 4f〈sup〉6〈/sup〉-4f〈sup〉6〈/sup〉 photoluminescence bands of Eu〈sup〉3+〈/sup〉 ions in reddish-orange light area were recorded. The Stark splitting of photoluminescence bands, double-exponential character of decay curves and long-lived emission for fabricated glass-ceramic samples clearly evidenced the partial substitution of Y〈sup〉3+〈/sup〉 by optically active Eu〈sup〉3+〈/sup〉 ions in precipitated YF〈sub〉3〈/sub〉 nanocrystals. Indeed, it was identified that applied annealing conditions resulted in significant, almost 34-fold prolongation of luminescence lifetime from 0.24 ms (Eu〈sup〉3+〈/sup〉 ions in xerogel host) up to 8.14 ms (Eu〈sup〉3+〈/sup〉 ions incorporated into YF〈sub〉3〈/sub〉 nanocrystals). It was also observed a clear correlation between identified phonon energies from IR measurements and luminescence behavior of Eu〈sup〉3+〈/sup〉 ions.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 15〈/p〉 〈p〉Author(s): Yabin Zhang, Jingjing Liu, Xiongfei Du, Wei Shao〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, the PVDF/glass as-prepared composite membrane was prepared through phase-inversion method and used to adsorb methylene blue dye. The results of SEM and BET showed that the membrane had an asymmetric nanoscale porous structure. The electronegativity on the surface of membrane was determined through zeta potential test. The adsorption properties of as-prepared composite membrane and glass membrane were studied through testing the removal ratio of methylene blue from aqueous solution. Then the effects of membranes dose, pH value, temperature and initial concentration on the removal ratio were systematically studied. The adsorption mechanism was also studied. The adsorption kinetics and adsorption isotherm fitted well with the pseudo-second-order model and Freundlich model, respectively. In addition, the adsorption efficiency of glass membrane basically remained 85% after eight repeated adsorption-calcination cycles. The obtained membranes could be reused for methylene blue removal with high efficiency for multiply times.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 15〈/p〉 〈p〉Author(s): Ho Jin Ma, Wook Ki Jung, Seok-Min Yong, Doo Hyun Choi, Do Kyung Kim〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Y〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-MgO nanocomposite has attracted attention for use in infrared windows and domes. However, the large difference in refractive index between the two phases of this materials phases induces inevitable grain boundary scattering. To overcome this drawback, it is indispensable to greatly reduce the grain size and eliminate residual pores. Two-step sintering has been extensively used to produce fine-grained ceramics, but long incubation time and an additional process are required. As a robust approach, pressure-assisted two-step consolidation of Y〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-MgO nanocomposite ceramics is investigated to achieve full density while retaining domain size. A sintering path for pressure-assisted two-step sintering and related kinetic window are obtained for the first time. By effectively suppressing grain growth and eliminating residual pores via two-step hot-pressing, outstanding mid- and near-infrared transmittance were achieved. The results indicate that pressure-assisted two-step sintering is a promising alternative strategy that can decrease the domain size and achieve full density of ceramics.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 15〈/p〉 〈p〉Author(s): Fan Zhang, Gaojing Zhang, Li Yang, Yichun Zhou, Yong Du〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Thermodynamic parameters of the YO〈sub〉1.5〈/sub〉-TaO〈sub〉2.5〈/sub〉 system were obtained, and the effects of elastic strain energy and diffusion on phase transformation of YTaO〈sub〉4〈/sub〉 were analyzed in this work. The YO〈sub〉1.5〈/sub〉-TaO〈sub〉2.5〈/sub〉 system was critically modeled using the CALPHAD technique based on our calculated formation energies by DFT and available experimental data. According to DFT calculations, M′-YTaO〈sub〉4〈/sub〉 was suggested to be the thermodynamically stable phase at low temperature. For a displacive transformation of T→M between the equilibrium tetragonal and monoclinic YTaO〈sub〉4〈/sub〉, our calculations suggested it cannot be hindered by elastic strain energy. For a diffusive transformation of T→M′, it can be divided into T→M and M→M′. Diffusive transition of M→M′ was likely to be impeded due to large diffusion energy barrier, which was calculated to be 3.260 eV. However, the driving force ΔG 〈sub〉M→M′〈/sub〉 is about -0.121 kJ/mol. The large diffusion energy barrier and small driving force may be the main reason that T cannot transform to M′ after cooling.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 15〈/p〉 〈p〉Author(s): Yuzhu Fan, Zhiyong Zhou, Ruihong Liang, Xianlin Dong〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉There are urgent demands for high performance capacitors with superior energy storage density and discharge performances. In this work, novel NaNbO〈sub〉3〈/sub〉-based lead-free ceramics (0.91NaNbO〈sub〉3〈/sub〉-0.09Bi(Zn〈sub〉0.5〈/sub〉Ti〈sub〉0.5〈/sub〉)O〈sub〉3〈/sub〉) with high energy storage capability, high power density and fast discharge speed were designed and prepared. Bi(Zn〈sub〉0.5〈/sub〉Ti〈sub〉0.5〈/sub〉)O〈sub〉3〈/sub〉 was chosen for the purpose to reduce the remnant polarization and improve the induced polarization. Consequently, a large stored energy storage density (〈em〉W〈/em〉〈sub〉s〈/sub〉˜ 3.51 J/cm〈sup〉3〈/sup〉) and high recoverable energy storage density (〈em〉W〈/em〉〈sub〉rec〈/sub〉˜ 2.20 J/cm〈sup〉3〈/sup〉) were obtained in 0.91NaNbO〈sub〉3〈/sub〉-0.09Bi(Zn〈sub〉0.5〈/sub〉Ti〈sub〉0.5〈/sub〉)O〈sub〉3〈/sub〉 ceramic under a high breakdown strength of 250 kV/cm, with excellent thermal stability in the range of 20–120 °C. More importantly, the investigated ceramics exhibited high power density (〈em〉P〈/em〉〈sub〉D〈/sub〉˜ 20 MW/cm〈sup〉3〈/sup〉) and ultrafast discharge rate (〈em〉t〈/em〉〈sub〉0.9〈/sub〉˜ 0.25 μs), demonstrating potential application in pulse powehr systems. This work provides an effective means of achieving excellent energy storage and discharge performances in NaNbO〈sub〉3〈/sub〉-based ceramics for application in dielectric capacitors.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 15〈/p〉 〈p〉Author(s): Yu Huang, Qinghu Guo, Hua Hao, Hanxing Liu, Shujun Zhang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Lead free dielectric ceramics of 0.65Bi〈sub〉0.51〈/sub〉Na〈sub〉0.47〈/sub〉Ti〈sub〉1-5x/4〈/sub〉Nb〈sub〉x〈/sub〉O〈sub〉3〈/sub〉- 0.35Ba(Ti〈sub〉0.7〈/sub〉Zr〈sub〉0.3〈/sub〉)O〈sub〉3〈/sub〉 (BB35-100xNb, x = 0.00, 0.01, 0.02, 0.04 and 0.08) are fabricated by conventional solid-state sintering method for potential energy storage applications. Benefited from the coexistence of relaxor and antiferroelectric features, a high recoverable energy storage density of 3.2 J/cm〈sup〉3〈/sup〉, together with high energy efficiency of 93%, is simultaneously achieved in bulk BB35-1Nb ceramic at the critical electric field of 280 kV/cm. The studied BB35-1Nb ceramic exhibits a wide temperature usage range of 20–160 °C with energy density variation below 3%, and excellent cycling reliability with both energy density and efficiency variations less than 4% over 10〈sup〉6〈/sup〉 cycles, together with its fast discharge time of ˜1.2 μs, making BB35-1Nb ceramic promising candidate for high-temperature, high power energy storage applications.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 15〈/p〉 〈p〉Author(s): Siqi Zhang, Jia Li, Wen Ni, Keqing Li〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study focuses on the effect of boron substitution on the crystallisation behaviour of an important bioceramic phase, tetracalcium phosphate (TTCP, Ca〈sub〉4〈/sub〉P〈sub〉2〈/sub〉O〈sub〉9〈/sub〉), in the 4.5SiO〈sub〉2〈/sub〉-3Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-1.5P〈sub〉2〈/sub〉O〈sub〉5〈/sub〉-5CaO glass system. The influence of phase separation on the crystallisation activation energy as well as the microstructure is systematically analysed. The results indicate that increasing the extent of substitution of B for Al tends to lead to a decrease of the glass-transition temperature (〈em〉T〈/em〉〈sub〉g〈/sub〉) and crystallisation temperature (〈em〉T〈/em〉〈sub〉p〈/sub〉). When the substitution amount of B reaches 15 mol%, phase separation is observed. Weak phase separations during glass making can promote the nucleation of crystals due to heterogeneous nucleation with reduced nucleation activation energy. When 50 mol% B is substituted, serious phase separation is observed, with spherical-shaped TTCP phases appearing in the glass. The growth of striped-shaped TTCP crystals is largely suppressed even when a long holding time (1 h) at 900 °C is applied.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 15〈/p〉 〈p〉Author(s): Z. Yan, S. Hara, N. Shikazono, W. Negishi, A. Kajihara〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉La〈sub〉0.6〈/sub〉Sr〈sub〉0.4〈/sub〉Co〈sub〉0.2〈/sub〉Fe〈sub〉0.8〈/sub〉O〈sub〉3-〈em〉δ〈/em〉〈/sub〉 (LSCF) cathodes on rigid Gd〈sub〉0.1〈/sub〉Ce〈sub〉0.9〈/sub〉O〈sub〉1.95〈/sub〉 (GDC) substrate were sintered to different densities, and their three dimensional (3D) microstructures were characterized using focused ion beam-scanning electronic microscopy (FIB-SEM) tomography. The microstructure anisotropies of the green and constrainedly sintered cathodes were studied using 3D mean intercept length (MIL) method and the two dimensional (2D) best-fit ellipse method and 3D best-fit ellipsoid method. It shows that in the constrained sintering of LSCF films, the microstructures were transversely isotropic in the plane parallel to the substrate, while the microstructures in the thickness direction were anisotropic. Density and grain size gradients were observed and quantified along the cathode thickness direction during constrained sintering. The pores were preferentially oriented and elongated in the thickness direction. The anisotropy factor increased as increasing the sintering time or sintering temperature in the current density range. Cross-sectional 2D measurements underestimated the pore anisotropy, but showed qualitative agreement with 3D measurements.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 15〈/p〉 〈p〉Author(s): Shu Wang, Lei Shi, Zhiang Xie, Yuan He, Dong Yan, Man-Rong Li, Juergen Caro, Huixia Luo〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A series of composites based on (100-〈em〉〈sub〉x〈/sub〉〈/em〉)wt.%Ce〈sub〉0.9〈/sub〉Pr〈sub〉0.1〈/sub〉O〈sub〉2-〈/sub〉δ-〈em〉x〈/em〉wt.%Pr〈sub〉0.6〈/sub〉Ca〈sub〉0.4〈/sub〉FeO〈sub〉3-〈/sub〉δ (〈em〉x〈/em〉 = 25, 40 and 50) doped with the cheap and abundant alkaline earth metal Ca〈sup〉2+〈/sup〉 at the A-site has been successfully designed and fabricated. The crystal structure, oxygen permeability, phase and CO2 stability were evaluated. The composition of 60wt.%Ce〈sub〉0.9〈/sub〉Pr〈sub〉0.1〈/sub〉O〈sub〉2-〈/sub〉δ-40wt.%Pr〈sub〉0.6〈/sub〉Ca〈sub〉0.4〈/sub〉FeO〈sub〉3-〈/sub〉δ(60CPO-40PCFO) possesses the highest oxygen permeability among three studied composites. At 1000 °C, the oxygen permeation fluxes through the 0.3 mm-thickness 60CPO-40PCFO membranes after porous La〈sub〉0.6〈/sub〉Sr〈sub〉0.4〈/sub〉CoO〈sub〉3-〈/sub〉δ each to 1.00 mL cm〈sup〉−2〈/sup〉 min〈sup〉−1〈/sup〉 and 0.62 mL cm〈sup〉−2〈/sup〉 min〈sup〉−1〈/sup〉 under air/He and air/CO〈sub〉2〈/sub〉 gradients, respectively. 〈em〉In situ〈/em〉 XRD results demonstrated that the 60CPO-40PCFO sample displayed a perfect structural stability in air as well as CO〈sub〉2〈/sub〉-containing atmosphere. Thus, low-cost, Co-free and Sr-free 60CPO-40PCFO has high CO〈sub〉2〈/sub〉 stability and is economical and environmental friendly since the expensive and volatile element Co was replaced by Fe and Sr was waived since it easily forms carbonates.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0955221919304558-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 15〈/p〉 〈p〉Author(s): Yuzhu Fan, Zhiyong Zhou, Ruihong Liang, Mingxing Zhou, Xianlin Dong〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The impact of A-site nonstoichiometry on the microstructure, electric properties, and phase stability of sodium niobate ceramics (Na〈sub〉1+〈/sub〉〈em〉〈sub〉x〈/sub〉〈/em〉NbO〈sub〉3〈/sub〉, 〈em〉x〈/em〉 = −2 to 1 mol %) was investigated. All the components maintained an orthorhombic antiferroelectric (AFE) structure. The grain size increased from 3.9 to 14.3 μm with the variation in 〈em〉x〈/em〉 from −2 to 1. The AFE–FE phase transition electric field dramatically increased from 100 kV cm〈sup〉−1〈/sup〉 at 〈em〉x〈/em〉 = 0 to 170 kV cm〈sup〉−1〈/sup〉 at 〈em〉x 〈/em〉= −2, confirming the enlarged energy barrier between AFE 〈em〉Pbma〈/em〉 and FE 〈em〉Pmc〈/em〉2〈sub〉1〈/sub〉 phase under external field in A-site deficient components. This is attributed to the lattice compressive stress generated by introducing proper A-site vacancies. Combined results of transmission electron microscopy and Raman spectroscopy indicated that the AFE distortion of 〈em〉Pbma〈/em〉 phase was significantly enhanced in A-site deficient components, which jointly contributed to the stability of AFE phase in A-site deficient NaNbO〈sub〉3〈/sub〉 material.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 15〈/p〉 〈p〉Author(s): Mei Fangsheng, Yuan Tiechui, Chu Aimin, Li Ruidi〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Due to the resource shortage of indium, the application of 10 wt%- tin doped indium oxide (10 wt%- ITO) with 74.4 wt% of indium is restricted in the field of flat panel display. A new ternary compound TCO material with 53.8 wt% of indium (35 wt%- ITO) was prepared by In〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-35 wt% SnO〈sub〉2〈/sub〉 powders, whose microstructure and properties were studied in comparison to 10 wt%- ITO. The research findings show that: (1) The phase composition of 35 wt%- ITO target is mainly In〈sub〉4〈/sub〉Sn〈sub〉3〈/sub〉O〈sub〉12〈/sub〉 and In〈sub〉2〈/sub〉SnO〈sub〉5〈/sub〉, without In〈sub〉2〈/sub〉O〈sub〉3〈/sub〉: Sn phase for 10 wt%- ITO; (2) When films possess the strong crystalline structure, the photoelectric properties of 35 wt%- ITO films are superior to 10 wt%- ITO. In addition, the crystalline structure of 35 wt%- ITO films could be changed from In〈sub〉4〈/sub〉Sn〈sub〉3〈/sub〉O〈sub〉12〈/sub〉 + amorphous to In〈sub〉4〈/sub〉Sn〈sub〉3〈/sub〉O〈sub〉12〈/sub〉 + In〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 by annealing, but for 10 wt%- ITO, only the crystallinity is changed.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 15〈/p〉 〈p〉Author(s): M.S. Nikova, V.A. Tarala, D.S. Vakalov, D.S. Kuleshov, A.A. Kravtsov, S.V. Kuznetsov, I.S. Chikulina, F.F. Malyavin, L.V. Tarala, E.A. Evtushenko, V.A. Lapin, M.A. Pankov〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The paper presents the results of the 〈em〉Sc〈sup〉3+〈/sup〉〈/em〉 solubility limits estimation in dodecahedral and octahedral garnet sites for 1100–1700 °C temperature range. The region of existence of solid solutions with the garnet structure in the 〈em〉Y〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-Sc〈sub〉2〈/sub〉O〈sub〉3〈/sub〉〈/em〉 and 〈em〉Yb〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-Sc〈sub〉2〈/sub〉O〈sub〉3〈/sub〉〈/em〉 systems narrows with increasing synthesis temperature. The 〈em〉Sc〈sup〉3+〈/sup〉〈/em〉 solubility in the dodecahedral site of the 〈em〉YbSAG〈/em〉 and 〈em〉YSAG〈/em〉 garnets decreases with increasing temperature, and at 1700 °C it is about 64 at. %. In the octahedral site of 〈em〉YbSAG〈/em〉 garnet, the 〈em〉Sc〈sup〉3+〈/sup〉〈/em〉solubility decreases from 89.5 to 66.5 at. % with increasing temperature, and in the 〈em〉YSAG〈/em〉 system it is about 97.5 at.%. The overall 〈em〉Sc〈sup〉3+〈/sup〉〈/em〉 solubility with the simultaneous introduction into both garnet sites is lower than with doping on one of the sites and also decreases with increasing temperature. The thermal stability of the compositions belonging to single-phase regions was confirmed by vacuum sintering up to 1850 °C.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 15〈/p〉 〈p〉Author(s): Junjie Zhao, Xiuxia Xu, Xiaotong Chen, Qian Xu, Zhou Luo, Xvsheng Qiao, Jincheng Du, Xianping Fan, Guodong Qian〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Oxyfluoride glass and glass ceramics have been widely used in optical devices with Ln〈sup〉3+〈/sup〉 doping. Especially, fluoride phase separation is considered as the initial stage of nanocrystallization that can help to realize the controllable crystallization and also provide the low phonon energy environment in oxyfluoride glass. Therefore, a structure model to describe this phase separated glass system is in great help for designing optical materials with high luminescence. In this study, large-scale molecular dynamics (MD) simulations were performed to understand the structural heterogeneity and make attempt to propose a structure model for fluoroaluminosilicate glass. The simulation results reveal immiscible behaviors of the fluoroaluminosilicate glass that separate into fluoride-rich phase and aluminosilicate-rich residual matrix, which have structural features analogous to fluoride and aluminosilicate glass, respectively. Besides, Al〈sup〉3+〈/sup〉 plays an essential role to inter-connect oxygen and fluorine ions on the oxide-fluoride phase interface, maintaining the stability of the glass system.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 15〈/p〉 〈p〉Author(s): Meiqi Yang, Ding Zhou, Jiayue Xu, Tian Tian, Runping Jia, Zhanyong Wang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉(Tb〈sub〉0.5〈/sub〉Y〈sub〉0.5〈/sub〉)〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 transparent ceramics have been prepared by wet chemical co-precipitation route and flowing H〈sub〉2〈/sub〉 atmosphere sintering. The optical quality, microstructure and magneto-optical properties of the ceramics were investigated. No sintering aids or milling were adopted in the ceramic fabrication processing. The cold isostatic pressed green compact could be sintered to be transparent (Tb〈sub〉0.5〈/sub〉Y〈sub〉0.5〈/sub〉)〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 ceramic at 1800 ℃ in flowing H〈sub〉2〈/sub〉 atmosphere. The mechanical polished ceramic showed the good transmittance from visible to near infrared wavelength, corresponding to a 71.9% transmittance at 1400 nm wavelength. The Verdet constant measured at 632.8 nm of the (Tb〈sub〉0.5〈/sub〉Y〈sub〉0.5〈/sub〉)〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 transparent ceramics was -220.19 rad T〈sup〉−1〈/sup〉  m〈sup〉-1〈/sup〉, which was 1.64 times that of Tb〈sub〉3〈/sub〉Ga〈sub〉5〈/sub〉O〈sub〉12〈/sub〉 single crystal.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 15〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 15〈/p〉 〈p〉Author(s): Muhammad Sheeraz, Abdul Khaliq, Aman Ullah, Hyoung-Su Han, Aurangzeb Khan, Amir Ullah, Ill Won Kim, Tae Heon Kim, Chang Won Ahn〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We use a strategy to reduce the driving electric field of the relaxor 0.72Bi〈sub〉1/2〈/sub〉Na〈sub〉1/2〈/sub〉TiO〈sub〉3〈/sub〉–0.28SrTiO〈sub〉3〈/sub〉 (BNT–28ST) by introducing ferroelectric plate–type Bi〈sub〉1/2〈/sub〉(Na〈sub〉0.78〈/sub〉K〈sub〉0.22〈/sub〉)〈sub〉1/2〈/sub〉TiO〈sub〉3〈/sub〉 (BNKT) particles. Consequently, 10 vol.% BNKT added BNT–28ST/BNKT (relaxor/ferroelectric) composite has delivered large normalized strain (〈em〉S〈/em〉〈sub〉max〈/sub〉/〈em〉E〈/em〉〈sub〉max〈/sub〉 = 650 pm/V) under relatively low applied field of 2.5 kV/mm with the reduction in the poling field value to 36% compared to that of pure BNT–28ST ceramics. We demonstrated that such behavior comes from the stress induced effect at the boundary of the ferroelectric and relaxor materials due to their different nature (relaxor/ferroelectric). The generation of stress is expected from the ferroelectric (BNKT) to the relaxor (BNT–28ST) at the boundary. Thereby, field–dependent stress at relaxor/ferroelectric phase boundary is monitored proposing the reduction of the poling field due to the strain coupling mechanism. Our findings provide a pathway for reducing the poling field in BNT–based incipient piezoelectric ceramics.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0955221919305369-ga1.jpg" width="387" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 15〈/p〉 〈p〉Author(s): Hirofumi Inada, Yuki Okazaki, Yuya Arakawa, Taigo Takaishi, Hideki Hashimoto〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉For red overglaze enamel decoration, a type of colored ceramic coating for ceramics, a partial peeling might occur in mass-produced ceramic ware products. In this study, multinuclear core/shell hematite/glass composite particles, comprising a hematite core and a glass shell, where hematite particles are highly dispersed in a glass matrix, were developed to prepare a red coating material that could achieve a bright red-colored overglaze enamel without peeling. A peeling-free, bright yellowish red-colored overglaze enamel could be obtained when using the composite particles as the red paint. The former function (preventing peeling) can be derived from micrometric size of the shell glass particles and the latter function (high chroma and lightness) is caused by highly dispersive hematite particles in the shell glass particles. Our results suggest that the composite particles are suitable for mass-production due to their peeling-free nature, indicating a potential to be widely used as coloring for ceramic coating products.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 15〈/p〉 〈p〉Author(s): Yanhui Li, Minglang Wang, Haidong Wu, Fupo He, Yong Chen, Shanghua Wu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, the light absorption of the pure ZrO〈sub〉2〈/sub〉 and three types of colorful ZrO〈sub〉2〈/sub〉 mixtures were investigated. It was found that the absorbance of colored ZrO〈sub〉2〈/sub〉 powder increases with the colorant content, and the yellow-colored powder has the strongest absorbance at the wavelength of 405 nm compared with the other two types of colored ZrO〈sub〉2〈/sub〉 powder. The cure behavior investigation on the ceramic suspensions of the above four types of ZrO〈sub〉2〈/sub〉 powders during DLP process shows that as the colorant content increases, the cure depth and excess cure width both decrease due to the ceramic absorbance. The cure depth of colored suspensions is linear with logarithm of incident energy, consistent with Beer-Lambert model, while the further research into the cure width shows that the excess cure width increases nonlinearly with logarithm of incident energy, which is inconsistent with Quasi-Beer-Lambert model. Additionally, colorful ZrO〈sub〉2〈/sub〉 accessories were successfully fabricated.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 15〈/p〉 〈p〉Author(s): Yahuan Zhao, Xiaoqiang Li, Chuanxin Liu, Hong Yang, Bo Chen, Yiming Qin, Shanshan Xu, Laifei Cheng, Litong Zhang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉SiC〈sub〉f〈/sub〉/SiC composites were irradiated to over 100 dpa with 300 keV Si ions at 300 ℃. Here, electron microscopy and Raman spectroscopy were utilized to study the microstructural evolution. The Raman spectra of fiber and matrix showed that the crystal structure was seriously damaged. TEM images revealed that the fiber underwent grain nucleation and growth in lower fluence region, accompanied by an amorphous layer near the damage peak area. Also, the matrix went through recrystallization, and the columnar grains turned into equiaxial ones. Moreover, stacking faults and massive amorphous islands were observed in high resolution TEM images. Following irradiation at 300 ℃, the matrix swelled, but the fiber and interphase shrunken along the axis. And, more remarkably, the hardness of fiber and matrix decreased to different extents, a result that was explained by the generation of amorphous islands and breakdown of covalent bonds, and recrystallization might be responsible for this.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 15〈/p〉 〈p〉Author(s): Jian Fang, Liangbo Sun, Qin Qi, Jie Zhang, Chunfeng Liu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A novel CaO-Li〈sub〉2〈/sub〉O-Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-SiO〈sub〉2〈/sub〉 (CLAS) glass was developed for the joining of porous Si〈sub〉3〈/sub〉N〈sub〉4〈/sub〉 and dense Si〈sub〉3〈/sub〉N〈sub〉4〈/sub〉. A multiphase interlayer consisting of CaAl〈sub〉2〈/sub〉Si〈sub〉2〈/sub〉O〈sub〉8〈/sub〉, LiAlSi〈sub〉2〈/sub〉O〈sub〉6〈/sub〉 and CaSiO〈sub〉3〈/sub〉 phases was formed in joint, which possessed matched CTE with the Si〈sub〉3〈/sub〉N〈sub〉4〈/sub〉 substrates. In addition, the infiltrated layer with bilayer structure in the porous Si〈sub〉3〈/sub〉N〈sub〉4〈/sub〉 substrate was observed. The effects of joining temperature and cooling rate on microstructure, phase evolution and shear strength of joints were studied carefully. The results showed that the kinds of precipitated phases remained invariable with the joining temperature increased, but the crystallinity in the interlayer was improved remarkably as the cooling rate reduced. The maximum shear strength of 45 MPa was obtained when the joining temperature and cooling rate were 1100 °C and 5 °C/min, respectively. Moreover, fracture during the shear test occurred mainly within porous Si〈sub〉3〈/sub〉N〈sub〉4〈/sub〉 side, indicating superior joining of dense Si〈sub〉3〈/sub〉N〈sub〉4〈/sub〉/glass-ceramic/porous Si〈sub〉3〈/sub〉N〈sub〉4〈/sub〉.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 15〈/p〉 〈p〉Author(s): Kai Xu, Houke Zou, Keke Chang, Zixuan Deng, Xiaobing Zhou, Yeyan Huang, Leilei Chen, Feng Huang, Qing Huang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Y〈sub〉3〈/sub〉Si〈sub〉2〈/sub〉C〈sub〉2〈/sub〉 coating on the surface of the silicon carbide powders can play as an important additive to improve the sintering process of silicon carbide ceramics. A detailed thermodynamic description for the Y-Si-C system is desired to study the sintering and densification mechanisms. Coupling the first-principles calculations and CALPHAD approach, we have thermodynamically investigated the Y-Si-C with its binary sub-systems. The presently obtained thermodynamic parameters can reasonably reproduce the available experimental data. With the theoretical analysis, we have successfully elaborated the thermal behaviors of the Y〈sub〉3〈/sub〉Si〈sub〉2〈/sub〉C〈sub〉2〈/sub〉 coating during the sintering process. Similar work on other SiC based systems may provide a solid thermodynamic basis for the development of other sintering aids in ceramics.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 16〈/p〉 〈p〉Author(s): T. Ibn-Mohammed, C.A. Randall, K.B. Mustapha, J. Guo, J. Walker, S. Berbano, S.C.L. Koh, D. Wang, D.C. Sinclair, I.M. Reaney〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The rising cost of energy and concerns about the environmental impact of manufacturing processes have necessitated the need for more efficient and sustainable manufacturing. The ceramic industry is an energy intensive industrial sector and consequently the potential to improve energy efficiency is huge, particularly through the introduction of modern sintering technologies. Although several energy efficient sintering processes have been developed, there is no comprehensive techno-economic analysis which compares and contrasts these techniques. This paper presents a critical review and analysis of a number of sintering techniques and compares them with the recently developed cold sintering process (CSP), including mode of operation, sintering mechanism, typical heating rates, duration of sintering, energy consumption profile and energy saving potential, limitations, key challenges for further development and current research efforts. By using a figure of merit, pounds per tonne of CO〈sub〉2〈/sub〉 saved (£/tCO〈sub〉2〈/sub〉-eq), which links initial capital investment with energy savings, within a framework derived from ranking principles such as marginal abatement cost curves and Pareto optimisation, we have demonstrated that under the scenarios considered for 3 separate functional oxides ZnO, PZT and BaTiO〈sub〉3〈/sub〉, CSP is the most economically attractive sintering option, indicating lower capital costs and best return on investment as well as considerable energy and emission savings. Although the current work establishes the viability of CSP as a competitive and sustainable alternative to other sintering techniques, the transition from laboratory to industry of CSP will require hugely different facilities and instrumentation as well as relevant property/performance validation to realise its full potential.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 16〈/p〉 〈p〉Author(s): Yong Deng, Weiguo Li, Shifeng Zheng, Xu Zhang, Xin Zhang, Ying Li, Xuyao Zhang, Zhouyu Fang, Jianzuo Ma, Zhaoliang Qu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, we proposed a temperature-dependent first matrix cracking stress model for cross-ply fiber reinforced ceramic-matrix composites (FRCMCs) first. It takes into account of the effects of interfacial shear stress and residual thermal stress as well as their evolution with temperature. Moreover, in order to characterize the effect of temperature on fracture strength, we defined the critical strain energy density associated with composites fracture, by which and the force-heat equivalence energy density principle, the temperature-dependent fracture strength model for cross-ply FRCMCs was established. The models’ predictions of first matrix cracking stress and fracture strength at different temperatures are in good agreement with experimental results available. This study not only advances our in-depth understanding of the quantitative relationship between temperature and mechanical properties of cross-ply FRCMCs, but also offers a powerful tool to predict the temperature-dependent first matrix cracking stress and fracture strength.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 16〈/p〉 〈p〉Author(s): Hai Jiang, Xiao-Hong Wang, Gui-Fen Fan, Wen Lei, Ming Fu, Xiao-Chuan Wang, Fei Liang, Wen-Zhong Lu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The effects of hot-pressing sintering on the phase composition, microstructure, thermal and electrical properties of AlN ceramics with CeO〈sub〉2〈/sub〉–CeF〈sub〉3〈/sub〉 additives were studied. During hot-pressing sintering, high pressure reduced the grain boundary phase CeAlO〈sub〉3〈/sub〉 and decreased the concentration of oxygen in AlN ceramics. The hot-pressing sintered AlN samples had a much higher thermal conductivity of 191.9 W/m·K than pressureless sintered ones because of the great reduction of grain boundary phases and oxygen impurities in AlN ceramic. As the carbon content in hot-pressing sintered sample was very high, carbon contamination led to the decrease in electrical resistivity and changes in polarization mechanisms for AlN ceramics. The relaxation peak in the dielectric temperature spectrum with an activation energy of 0.64 eV for hot-pressing sintered samples was caused by electrons from free carbon at low temperature. Overall, hot-pressing sintering can effectively increase the thermal conductivity and change the electrical properties of AlN ceramics.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 16〈/p〉 〈p〉Author(s): Hui Hua, Xinjia Wang, Hui Ding, Qiping Du, Shaowei Feng, Hongtao Jiang, Jun Jiang, Haochuan Jiang, Zhijun Zhang, Haiming Qin〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉YGG:Dy and YGG:Cr polycrystalline ceramics were prepared via a solid-state reaction-two step sintering approach. The crystalline structure, phase evolution, morphologies and luminescence properties of as prepared transparent ceramics were intensively investigated. In-line transmittance of YGG:Dy and YGG:Cr transparent ceramics can reach up to 70.6% and 67.3% at 1200 nm, respectively. For YGG:Dy transparent ceramic, three emission bands centered at 492 nm, 581 nm and 669 nm can be observed under excitation of 353 nm. Its CIE color coordinate is (0.3182, 0.3326) under UV irradiation, which is a promising UV-converting candidate for WLEDs. While the emission peak of YGG:Cr transparent ceramic is at about 709 nm, which can be one of the candidate materials applied in red-emitting LEDs with excellent color rendering index. The experimental results demonstrate that Y〈sub〉3〈/sub〉Ga〈sub〉5〈/sub〉O〈sub〉12〈/sub〉:M〈sup〉3+〈/sup〉 (M = Dy, Cr) transparent ceramics are promising novel luminescent materials for LEDs.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 16〈/p〉 〈p〉Author(s): Wanli Wang, Jihua Huang, Yonglei Wang, Jian Yang, Shuhai Chen, Xingke Zhao〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Taking advantages of reaction composite brazing, transient liquid phase bonding (TLP) and partial transient liquid phase bonding (PTLP), a novel process with the characteristics of low-temperature bonding and high-temperature resisting was developed for joining C〈sub〉f〈/sub〉/SiC composite to GH3044 alloy by using (Cu-Ti) + C + Ni mixed powder filler. Under the bonding temperature (980 °C), the reaction between the liquid Cu-Ti alloy and C particles (reaction composite mechanism), composition homogenizations between the joining layer and Ni particles (PTLP mechanism) as well as Ni-based substrate (TLP mechanism) occurred to complete the transformation (Cu,Ti)〈sub〉l〈/sub〉 + C〈sub〉s〈/sub〉 + Ni〈sub〉s〈/sub〉 → TiC〈sub〉s〈/sub〉 + (Cu,Ni)〈sub〉s〈/sub〉. Thereby, a joint with high-temperature resistance and excellent mechanical properties was obtained in relatively short holding time. The melting-point of the joint (1050 °C) was obviously higher than that of Cu-Ti alloy (898 °C) in the filler. The bonded joints exhibited shear strengths of 229, 225 and 104 MPa at room temperature, 600 °C and 1000 °C, respectively.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 15〈/p〉 〈p〉Author(s): Yong-Hyeon Kim, Young-Wook Kim〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉SiC ceramics sintered with yttria were successfully joined without an interlayer by conventional hot pressing at lower temperatures (2000–2050 °C) compared to those of the sintering temperatures (2050–2200 °C). The joined SiC ceramics sintered with 2000 ppm Y〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 showed almost the same thermal conductivity (˜198 Wm〈sup〉−1〈/sup〉 K〈sup〉−1〈/sup〉), fracture toughness (3.7 ± 0.2 MPa m〈sup〉1/2〈/sup〉), and hardness (23.4 ± 0.8 GPa) as those of the base material, as well as excellent flexural strength (449 MPa). In contrast, the joined SiC ceramics sintered with 4 wt% Y〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 showed very high thermal conductivity (˜204 Wm〈sup〉−1〈/sup〉 K〈sup〉−1〈/sup〉) and excellent flexural strength (˜505 MPa). Approximately 16–22% decreases in strength compared to those of the base SC materials were observed in both joined ceramics, due to the segregation of liquid phase at the interface. This issue might be overcome by preparing well-polished and highly flat surfaces before joining.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 16〈/p〉 〈p〉Author(s): J.S.K.-L. Gibson, J. Gonzalez-Julian, S. Krishnan, R. Vaßen, S. Korte-Kerzel〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉MAX phases have great potential under demands of both high-temperature and high-stress performance, with their mixed atomic bonding producing the temperature and oxidation resistance of ceramics with the mechanical resilience of metals.〈/p〉 〈p〉Here, we measure the mechanical properties up to 980C by nanoindentation on highly dense and pure Cr〈sub〉2〈/sub〉AlC, as well as after oxidation with a burner rig at 1200 °C for more than 29 h. Only modest reductions in both hardness and modulus up to 980 °C were observed, implying no change in deformation mechanism.〈/p〉 〈p〉Furthermore, micro-cantilever fracture tests were carried out at the Cr〈sub〉2〈/sub〉AlC/Cr〈sub〉7〈/sub〉C〈sub〉3〈/sub〉 and Cr〈sub〉7〈/sub〉C〈sub〉3〈/sub〉/Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 interfaces after the oxidation of the Cr〈sub〉2〈/sub〉AlC substrates with said burner rig. The values are typical of ceramic-ceramic interfaces, below 4 MPa〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈msqrt〉〈mi〉m〈/mi〉〈/msqrt〉〈/math〉, leading to the hypothesis that the excellent macroscopic behaviour is due to a combination of low internal strain due to the match in thermal expansion coefficient as well as the convoluted interface.〈/p〉 〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 16〈/p〉 〈p〉Author(s): Alexei Richter, Lutz-Michael Berger, Yoo Jung Sohn, Susan Conze, Kerstin Sempf, Robert Vaßen〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Atmospheric plasma sprayed (APS) Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-TiO〈sub〉2〈/sub〉 coatings have found a wide range of industrial application due to their favorable properties, combined with low costs and a high availability. However, the detailed effect of the phase composition and the element distribution of the feedstock powders on the coating properties and the spraying process have only crudely been investigated so far. Here the impact of aluminum titanate (Al〈sub〉2〈/sub〉TiO〈sub〉5〈/sub〉) on the microstructural features and mechanical properties of Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-40 wt.% TiO〈sub〉2〈/sub〉 APS coatings is demonstrated by investigating the detailed phase composition and the distribution of aluminum and titanium in three fused and crushed feedstock powders and the respective coatings. Thereby, a direct influence of Al〈sub〉2〈/sub〉TiO〈sub〉5〈/sub〉 content on the deposition efficiency, the porosity, the elastic modulus, and the hardness of the coatings is revealed. The results emphasize the need for a more detailed specification of commercial Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-TiO〈sub〉2〈/sub〉 feedstock powders to ensure a high reliability of the coating properties.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 16〈/p〉 〈p〉Author(s): Roy M. Sullivan〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The formulation of Deal and Grove for the oxidation of silicon and the growth of a silica layer is revisited to include the effects of a protective coating layer. The linear-parabolic equation of the form 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si6.svg"〉〈mrow〉〈msubsup〉〈mi〉x〈/mi〉〈mi〉o〈/mi〉〈mn〉2〈/mn〉〈/msubsup〉〈mo〉+〈/mo〉〈mi〉A〈/mi〉〈msub〉〈mi〉x〈/mi〉〈mi〉o〈/mi〉〈/msub〉〈mo〉=〈/mo〉〈mi〉B〈/mi〉〈mi〉t〈/mi〉〈/mrow〉〈/math〉 is still applicable, but the expression for the constant 〈em〉A〈/em〉 must be modified to account for the coating. The modified expression for 〈em〉A〈/em〉 is a linear function of the coating thickness. The modified formulation is applied to assess recently published experimental results for the oxidation of a silicon bond coat in an environmental barrier coating. Application of the modified expression for 〈em〉A〈/em〉 to the experimental results leads to an estimate of the ratio of the oxidant permeability in the oxide to its permeability in the coating.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 16〈/p〉 〈p〉Author(s): Yu Pan, Jing Wang, Ning Wang, Yongsheng Liu, Chenhao Wang, Sujun He, Laifei Cheng〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Herein, C/SiC-CNTs composites were prepared by laser assisted chemical vapor infiltration (LA-CVI) method combined with vacuum impregnation. Density, mechanical property and thermal conductivity of as-prepared composites were then investigated by various analytical methods. Scanning electron microscopy (SEM) revealed good dispersion of CNTs in C/SiC-CNTs between composites layers and directional heat transfer channels. This formed unique three-dimensional connected networks, reinforcing multi-scale composites matrix. Average density and bending strength of composites were estimated to 2.35 g cm〈sup〉−3〈/sup〉 and 598 MPa, respectively, which is 20.5% and 27.2% higher than those of CVI-C/SiC composites. The comparison between theoretical thermal conductivity and experiments revealed that the overall thermal conductivity of LA-CVI-C/SiC-CNTs composites (150.42 W m〈sup〉−1〈/sup〉 K〈sup〉−1〈/sup〉) was nearly 25 times higher than that of CVI-C/SiC composites.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 16〈/p〉 〈p〉Author(s): Hui Sun, Tsung-Yen Kuo, Sheng-Chi Chen, Yin-Hung Chen, Hsin-Chih Lin, Mohammad Arab Pour Yazdi, Alain Billard〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Herein, intrinsic p-type conductivity of NiO films were enhanced by high power impulse magnetron sputtering (HiPIMS) technology, where more charged Ni〈sup〉3+〈/sup〉 ions are created during the deposition process. The formation of Ni〈sup〉3+〈/sup〉 ions are advantageous for strengthening the p-type conductivity of NiO films. As the pulse off-time increases from 0 μs to 3000 μs, Ni〈sup〉3+〈/sup〉 concentration improves greatly, indicating the amount of Ni vacancies as well as the hole concentration significantly enhances. It confirms that HiPIMS is a preferential technology for preparing NiO films with high p-type conductivity. Especially, when pulse off-time reaches 3000 μs, a high carrier concentration of 2.86 × 10〈sup〉21〈/sup〉 cm〈sup〉−3〈/sup〉 and a relatively low electrical resistivity about 0.07 Ω·cm are achieved.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 16〈/p〉 〈p〉Author(s): Mao Fu, Jing Liu, Xinfa Dong, Li Zhu, Yingchao Dong, Stuart Hampshire〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Coal fly ash, a solid state waste massively produced from coal combustion, is considered to be highly hazardous to the environment due to its persistently toxic trace elements. High-value added waste recycling is a promising technique to address this issue. In this work, a waste-to-resource strategy is proposed for design of highly porous whisker-structured mullite ceramic membranes derived from waste coal fly ash and Al(OH)〈sub〉3〈/sub〉 as raw materials and MoO〈sub〉3〈/sub〉 as a single sintering additive. These were characterized in terms of their dynamic sintering behavior, shrinkage, bulk density, porosity, phase evolution, microstructure, pore size distribution, N〈sub〉2〈/sub〉 permeation flux, and mechanical strength. Addition of molybdenum trioxide effectively inhibited the sintering densification of membranes while at the same time forming a metastable low viscosity liquid at lower temperatures. This enables formation of a novel and more highly porous whisker-interlocked structure and accelerates the growth of mullite whiskers with controllable morphologies. Without degradation of mechanical properties, the open porosity increased significantly from 41.65 ± 0.13% to 58.14 ± 0.15% with increasing MoO〈sub〉3〈/sub〉 content from 0 to 20 wt.% without any pore-forming agent, while shrinkage and pore size decreased. The method proposed in this study is expected not only to give a new and facile insight for high-value added recycling of waste coal fly ash but also to fabricate low-cost high performance ceramic membranes with novel structures for further environmental applications.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 16〈/p〉 〈p〉Author(s): Daoyao Ke, Anna Jiang, Mattia Biesuz, Mauro Bortolotti, Gianmarco Taveri, Xiaoyi Wang, Ming Xu, Jiang Li, Yagang Feng, Chunfeng Hu, Salvatore Grasso〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We developed Cold Isostatic Joining (CIJ) which is an environmental friendly room temperature joining method. This technique extends cold sintering process to joining of glasses. By optimizing the CIJ conditions a shear stress (18 MPa) comparable to bulk fused silica was achieved. The technique surpasses other joining methods (e.g. adhesive bonding and brazing), because it is insensitive to thermal degradation. Unlike pressure-less silicate bonding, pressure assisted CIJ resulted in a thin joining interlayer (≈27 nm) which maintained its integrity after being heated up to 1000 °C. The in-line transmittance (92%) was identical to un-joined material over the full spectrum making the joining nearly undetectable. The mechanism of CIJ formation and joining were clarified using X-ray diffraction (XRD and pole figure), scanning electron microscopy (SEM) and in line transmittance measurements. The cold joining method could find applications in the field of optics and semiconductors for wafer and lens bonding.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 16〈/p〉 〈p〉Author(s): Juan Jiang, Na Ni, Wei Hao, Xiaofeng Zhao, Fangwei Guo, Xiaohui Fan, Ping Xiao〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Yttrium aluminum garnet (YAG) fibers were prepared by a sol-gel method, and then sintered in air or nitrogen atmosphere, respectively. The effects of sintering atmosphere on the densification process and microstructure of YAG fibers were investigated. No obvious difference can be found in the fibers sintered below 800 °C. At 1100 °C, the grain size of YAG fibers sintered in nitrogen is much smaller than in air. This difference is much clearer at the higher temperature of 1200 °C. The fine grains are explained by the existence of residual carbon in YAG fibers, which can be trapped at the grain boundaries to hinder the movement of grain boundary. Meanwhile, the densification degree of fibers sintered in nitrogen is higher than in air at 1200 °C, due to the smaller grain size and higher oxygen vacancy concentration generated in the nitrogen atmosphere, which leads to a higher fiber densification rate.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 16〈/p〉 〈p〉Author(s): Jiangkun Chen, Shaoxiong Wang, Shichen Li, Feng Huang, Daqin Chen〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In-situ glass crystallization is an effective way to integrate lanthanide-doped upconversion nanocrystals into amorphous glass, producing bulky nanocomposites for specific applications. However, the precipitation of hexagonal NaYbF〈sub〉4〈/sub〉 nanocrystals from glass is rarely reported owing to the preferred crystallization of cubic phase. Herein, phase-controllable in-situ crystallization of cubic/hexagonal NaYbF〈sub〉4〈/sub〉 nanocrystals in glass is achieved 〈em〉via〈/em〉 Y〈sup〉3+〈/sup〉 doping. A series of structural and spectroscopic characterizations evidence the formation of Na(Yb/Y)F〈sub〉4〈/sub〉 solid-solution nanocrystals in glass and the incorporation of lanthanide emitting centers (Er〈sup〉3+〈/sup〉, Tm〈sup〉3+〈/sup〉, Eu〈sup〉3+〈/sup〉) into the crystalline lattice. Introducing high-content Y〈sup〉3+〈/sup〉 dopants is beneficial to induce the crystallization of hexagonal NaYbF〈sub〉4〈/sub〉 phase in glass and enables elaborated tunability of Er〈sup〉3+〈/sup〉 upconversion emissive colors. Finally, a prototype upconverted solid-state-lighting device is constructed by coupling 980 nm laser with the as-prepared Er/Tm doped monolithic glasses containing Na(Yb/Y)F〈sub〉4〈/sub〉 nanocrystals, producing bright upconversion white-light with luminous efficiency of 1 lm/W and energy efficiency of 0.5%.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0955221919305928-ga1.jpg" width="468" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 16〈/p〉 〈p〉Author(s): I.S. Merenkov, H. Katsui, M.N. Khomyakov, V.S. Sulyaeva, R.V. Pushkarev, R. Tu, T. Goto, M.L. Kosinova〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Herein, we report on the synergetic effect of simultaneously using of hexamethyldisilane (HMDS) and trimethylamine borane (TMAB) as precursors for a high-rate laser chemical vapor deposition of SiBCN films. The major components of obtained films were successfully controlled by deposition temperature from B〈sub〉4〈/sub〉C to graphene and β-SiC. In addition, B〈sub〉4〈/sub〉C and graphene/β-SiC films were synthesized from TMAB and HMDS, respectively. The growth rate of SiBCN films was extremely high (up to 1620 μm/h) in contrast to 18 μm/h and 415 μm/h for graphene/β-SiC and B〈sub〉4〈/sub〉C films, respectively. Thermodynamic modeling demonstrated that reactions between nitrogen- and silicon-containing gas species during double-source CVD process could be the possible reason of synergism and growth rate increasing. A mechanical study demonstrated very high hardness (up to 43 ± 7 GPa) and wear resistivity of the SiBCN films. The reported results reveal a significant potential of precursor synergism for the design of new materials with enhanced properties.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 16〈/p〉 〈p〉Author(s): Kento Ishii, Chika Matsunaga, Kiyoshi Kobayashi, Adam J. Stevenson, Caroline Tardivat, Tetsuo Uchikoshi〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Ba〈sub〉0.5〈/sub〉Sr〈sub〉0.5〈/sub〉Co〈sub〉0.8〈/sub〉Fe〈sub〉0.2〈/sub〉O〈sub〉3-〈/sub〉δ (BSCF), which exhibits a high mixed oxide ionic-electronic conduction, was used for the fabrication of an oxygen separation membrane. An asymmetric structure, which was a thin and dense BSCF membrane layer supported on a porous BSCF substrate, was fabricated by the electrophoretic deposition method (EPD). Porous BSCF supports were prepared by the uniaxial pressing method using a powder mixture with BSCF and starch as the pore-forming agent (0–50 wt.%). The sintering behaviors of the porous support and the thin layer were separately characterized by dilatometry to determine the co-fired temperature at which cracking did not occur. A crack-free and thin dense membrane layer, which had about a 15 μm thickness and 〉95% relative density, was obtained after optimizing the processes of EPD and sintering. The dense/porous interface was well-bonded and the oxygen permeation flux was 2.5 ml (STP) min〈sup〉−1〈/sup〉 cm〈sup〉-2〈/sup〉 at 850 °C.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 16〈/p〉 〈p〉Author(s): Peng Wan, Mian Li, Kai Xu, Haibo Wu, Keke Chang, Xiaobing Zhou, Xiangdong Ding, Zhengren Huang, Hongxiang Zong, Qing Huang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A ternary carbide Dy〈sub〉3〈/sub〉Si〈sub〉2〈/sub〉C〈sub〉2〈/sub〉 coating was fabricated on the surface of SiC through a molten salt technique. Using the Dy〈sub〉3〈/sub〉Si〈sub〉2〈/sub〉C〈sub〉2〈/sub〉 coating as the joining interlayer, seamless joining of SiC ceramic was achieved at temperature as low as 1500 °C. Phase diagram calculation indicates that seamless joining was achieved by the formation of liquid phase at the interface between Dy〈sub〉3〈/sub〉Si〈sub〉2〈/sub〉C〈sub〉2〈/sub〉 and SiC, which was squeezed out under pressure and continuously consumed by the joining interlayer. This work implies the great potential of the family of ternary rare-earth metal carbide Re〈sub〉3〈/sub〉Si〈sub〉2〈/sub〉C〈sub〉2〈/sub〉 (Re = Y, La-Nd) as the sacrificial interlayer for high-quality SiC joining.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 16〈/p〉 〈p〉Author(s): M. De Smedt, K. Andreev, N. Shetty, E. Verstrynge〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Variability of in-service loads justifies the broad range of microstructures in ceramic refractories used as high temperature industrial insulation. Application of the non-destructive technique of Acoustic Emission (AE) potentially provides an insight into the microstructural response to thermo-mechanical loads and enables rational material development and application. Regarding the multitude of existing AE approaches, effectiveness of a number of AE damage parameters was studied. The AE parameters were obtained in cyclic three-point bending for refractory castables showing different brittleness at failure. No significant damping effects and good correlation with material brittleness was seen for the parameters of event counts, b-value, and AF/RA ratio. The loads introducing critical damage obtained from LOAD and CALM ratios of AE were in agreement with those indicated by AF/RA ratio and event counts during unloading. In the study, the parameter of AF/RA ratio differentiating between shear and tensile failure signals was seen as the most universal criterion.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the European Ceramic Society, Volume 39, Issue 16〈/p〉 〈p〉Author(s): Enrico Storti, Cameliu Himcinschi, Jens Kortus, Christos G. Aneziris〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Calcium zirconate fibers were produced by electrospinning and characterized in this work. The solution was prepared from zirconium and calcium salts, using polyvinyl-pyrrolidone (PVP) as processing aid. The decomposition of the organic fraction and crystallization of calcium zirconate were followed by thermogravimetry and differential scanning calorimetry (TG/DSC). Raman Spectroscopy was used to measure the vibrational modes in the green as well as in the calcined fibers. The final phase composition was studied by means of X-ray diffraction (XRD). The fiber morphology was investigated by confocal laser scanning microscopy (CLS) and scanning electron microscopy (SEM). The formation reaction of calcium zirconate was observed at about 740 °C. Highly crystalline fibers were obtained already at 800 °C, but the crystallinity and calcium zirconate yield improved when the temperature was increased to 1000 °C.〈/p〉〈/div〉