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  • 1
    Electronic Resource
    Electronic Resource
    Microstructure and Microwave Dielectric Properties of Ba(Zn1/3Ta2/3)O3 Ceramics with ZrO2 Addition (2002)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 85 (2002), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The effect of ZrO2 on crystallographic order, microstructure, and microwave dielectric properties of Ba(Zn1/3Ta2/3)O3 (BZT) ceramics was investigated. A small amount of ZrO2 disturbed the 1:2 cation ordering. The average grain size of the BZT significantly increased with the addition of ZrO2, which was attributed to liquid-phase formation. The relative density increased with the addition of a small amount of ZrO2, but it decreased when the ZrO2 content was increased. Variation of the dielectric constant with ZrO2 addition ranged between 27 and 30, and the temperature coefficient of resonant frequency increased abruptly as the ZrO2 amount exceeded 2.0 mol%. The Q value of the BZT significantly improved with the addition of ZrO2, which could be explained by the increased relative density and grain size. The maximum Q×f value achieved in this investigation was ∼164 000 GHz for the BZT with 2.0 mol% ZrO2 sintered at 1550°C for 10 h.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00060.x
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  • 2
    Electronic Resource
    Electronic Resource
    Microstructural Observations in Barium Calcium Magnesium Niobate (2000)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 83 (2000), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Microstructural studies on (1 −x)Ba(Mg1/3Nb2/3)O3–xCa(Mg1/3Nb2/3)O3 (BCMN) complex perovskite compounds, which are mixtures of Ba(Mg1/3Nb2/3)O3 (BMN) and Ca(Mg1/3Nb2/3)O3 (CMN), were conducted using scanning electron microscopy, transmission electron microscopy, and X-ray diffractometry. Pure BMN and CMN both have a 1:2 ordered structure, via the chemical ordering of B-site cations; however, the tilting of oxygen octahedra is involved in pure CMN, whose structure has a 1:2 ordered monoclinic unit cell that is characterized by (±1/6,±1/6,±1/6)-type superlattice reflections in electron diffraction patterns along the [110] zone axis that is based on a simple cubic perovskite. Studies of the morphologic differences have indicated two types of inhomogeneities in a mixture of the BCMN system: (i) a rather large-scale segregation (i.e., grain sizes of several micrometers), where the grains are separated compositionally as being barium-rich or calcium-rich, and (ii) fine-scale lamellar-type segregations 20 nm wide and 200 nm long. The segregation that is caused by Ba and Ca ions can be identified by the difference of superlattice modulations from high-resolution transmission electron microscopy lattice images.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2000.tb01546.x
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  • 3
    Electronic Resource
    Electronic Resource
    Formation of self-assembled GaAs/AlGaAs quantum dots by low-temperature epitaxy (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 2615-2617 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the direct formation of self-assembled GaAs/AlGaAs quantum dots by low-temperature molecular beam epitaxy. To drive a three dimensional growth mode, the (1×1) AlGaAs surface was exposed alternately to the Ga and As sources. The resulting GaAs nanocrystals having {111} facets were clearly identified by high-resolution transmission electron microscopy. The emission spectra also confirmed the formation of dots. The transition to a three-dimensional growth mode is attributed to the limited surface migration of Ga adatoms on the AlGaAs surface, which has excess As at low substrate temperature. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122523
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  • 4
    Electronic Resource
    Electronic Resource
    Structural Variation of the BaTi4O9 Thin Films Grown by RF Magnetron Sputtering (2005)
    Oxford, UK : Blackwell Science Inc
    Journal of the American Ceramic Society 88 (2005), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: BaTi4O9 thin films were grown on a Pt/Ti/SiO2/Si substrate using rf magnetron sputtering and the structure of the thin films were then investigated. For the films grown at low temperature (≤350°C), an amorphous phase was formed during the deposition, which then changed to the BaTi5O11 phase when the annealing was conducted below 950°C. However, when the annealing temperature was higher than 950°C, a BaTi4O9 phase was formed. On the contrary, for the films grown at high temperature (〉450°C), small BaTi4O9 grains were formed during the deposition, which grew during the annealing. The homogeneous BaTi4O9 thin films were successfully grown on Pt/Ti/SiO2/Si substrate when they were deposited at 550°C and subsequently rapid thermal annealed at 900°C for 3 min.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00311.x
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  • 5
    Electronic Resource
    Electronic Resource
    Electron-Beam-Induced Phase Transformations from Metakaolinite to Mullite Investigated by EF-TEM and HRTEM (2001)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Both energy-filtered electron diffraction and EDS data clearly indicate extraction of amorphous silica from the parent metakaolinite by electron beam heating. Compared with the extracted silica through furnace heating, a larger population with inhomogeneous distribution and higher structural disorder of extracted silica by beam heating was noticed. There is a possibility that the spinel-type phase has lower symmetry than the suggested cubic symmetry, while the 〈111〉 orientation of the spinel-type phase is not perpendicular to the (001) plane of metakaolinite. HRTEM images of mullite crystals apparently demonstrate their random orientations with respect to the parent metakaolinite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00964.x
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  • 6
    Electronic Resource
    Electronic Resource
    Microstructure and Dielectric Properties of Barium Strontium Magnesium Niobate (2001)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Dielectric properties and their related microstructural characteristics in solid solutions of (1 –x)Ba(Mg1/3Nb2/3)O3–xSr(Mg1/3Nb2/3)O3 (BMN–SMN, or BSMN) were investigated by measuring the relative permittivity (ɛr), Q values, and temperature coefficient of resonator frequency (τf), and by observing microstructure using transmission electron microscopy. When the tolerance factor (t) was 〉0.99 in BSMN with composition 0 〈 x 〈 0.5, where the tilting of oxygen octahedra was not involved, the microstructure included only 1:2 ordered phase. In the region where 0.99 〉 t 〉 0.97 with 0.7 〈 x 〈 1.0, the phase due to the antiphase tilting of oxygen octahedral, the disordered phase, and the 1:2 ordered phase were also present. In a few of the grains, core–shell-type structures, whose main components were dislocations and stacking faults, were found in the solid solution of BSMN.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00966.x
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  • 7
    Electronic Resource
    Electronic Resource
    Microstructure Characterizations in Calcium Magnesium Niobate (2001)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Microstructural studies on the domain boundaries in Ca(Mg1/3CNb2/3)O3 (CMN) complex perovskite compound were conducted using X-ray diffractometry and transmission electron microscopy. The 1:2 chemical ordering of B-site cations and the tilting of oxygen octahedra were involved in the CMN microstructure, as inferred from the presence of two types of domain boundaries. One type was the antiphase boundaries (APBs), which did not lie on a specific set of crystallographic planes. These boundaries were caused by the chemical 1:2 ordering of B-site cations, magnesium and niobium. The other type was the ferroelastic domain boundaries, which were parallel to a certain crystallographic plane. Therefore, CMN had the 1:2 ordered monoclinic unit cell distorted by the antiphase or in-phase tilting of oxygen octahedra. CMN had the mixed phases rather than the homogeneous phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00888.x
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  • 8
    Electronic Resource
    Electronic Resource
    Microstructure of Lanthanum Magnesium Niobate at Elevated Temperature (2000)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 83 (2000), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Microstructural studies of the complex perovskite compound La(Mg2/3Nb1/3)O3 (LMN) were conducted using transmission electron microscopy (TEM) and X-ray diffractometry (XRD) at elevated temperatures. 1:1 chemical ordering of B-site cations and tilting of oxygen octahedra were observed in LMN. Three types of superlattice reflections, [1—2]{111}, [1—2]{110}, and [1—2]{100} were observed at room temperature and at 800°C in electron diffraction patterns. In the XRD experiments, the [1—2]{210} and [1—2]{300} extra peaks disappeared at temperatures 〉1200°C. However, the intensity of the superlattice [1—2]{111} peak did not change with increased temperature up to 1400°C. These results strongly indicated that the origin of superlattice reflection [1—2]{111} was different from that of the other superlattice reflections. It was mainly caused by the 1:1 chemical ordering of magnesium and niobium atoms. The TEM image observed at 800°C showed the ordered domain structures separated by the antiphase boundaries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2000.tb01299.x
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  • 9
    Electronic Resource
    Electronic Resource
    Interfacial Structure of Disordered-Ordered Domain Boundaries in Lanthanum-Doped Barium Magnesium Niobate (1998)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 81 (1998), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Microstructural studies on the interfacial boundaries of disordered and 1:2 ordered domains in lanthanum-doped (Ba0.975La0.025)(Mg0.34Nb0.66)O3 were performed using high-resolution transmission electron microscopy and synchrotron powder X-ray diffractometry. Disordered and 1:2 ordered domains both coexisted in a single grain. Each domain occupied its own region, and the interfaces were atomically sharp and coherent. The wavelength of the superlattice modulation in the 1:2 ordered domain was ∼0.71 nm. The transition from the 1:2 ordered region to the disordered one could be differentiated at the interface by using the superlattice modulations in the 1:2 ordered domain. From these observations, a deducible interfacial model also was presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1998.tb02779.x
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  • 10
    Electronic Resource
    Electronic Resource
    High-Resolution Transmission Electron Microscopy Observations on Antiphase Boundaries in Barium Lanthanum Magnesium Niobate (2001)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Atomic structural observations on the antiphase boundaries (APBs) in the complex barium lanthanum magnesium niobate perovskite compound Ba0.7La0.3(Mg0.43Nb0.57)O3 (BLMN), which has a 1:1 chemical ordering of B-site cations, were conducted using high-resolution transmission electron microscopy. Using APB contrast, the curved APB was determined to have a ledged structure, with a terrace that was composed of the (111) plane at an atomic level. In APBs with finite widths, microfacets on the (111) planes also were observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00936.x
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