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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
    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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  • 4
    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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  • 5
    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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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    Crack Repairing in Alumina by Penetrating Glass (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: Through-the-thickness cracks with the depth of about 2.5 mm were introduced on the flexural specimens of alumina. Borosilicate glass was then penetrated into the cracks at 1500°C to repair them. Strength testing indicated that the cracks, once repaired, became even stronger than mother material alumina. The reason of the strengthening was discussed in terms of residual stress and the rebonding of alumina grains on crack surfaces. This investigation implies that cracks in alumina can be repaired by simply penetrating glass into them.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00086.x
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  • 8
    Electronic Resource
    Electronic Resource
    Crack Healing in Silicon Carbide (2004)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 87 (2004), 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: Crack healing in silicon carbide was investigated by introducing cracks into specimens and subsequently heat-treating the specimens. It was observed that cracks were healed, dramatically increasing the strength, by being filled with amorphous silica produced by the oxidation of silicon carbide. It was shown that the residual stress produced by the thermal expansion mismatch between silica within cracks and surrounding silicon carbide played a major role in the increase of the strength. Our results imply that a simple oxidation heat treatment can improve the reliability of silicon carbide components.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2004.00490.x
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  • 9
    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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  • 10
    Electronic Resource
    Electronic Resource
    Microstructural Changes in Lanthanum-Doped Barium Magnesium Niobate (1999)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), 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: Observations of microstructural changes in (Ba0.95La0.05)-(Mg0.35Nb0.65)O3 and (Ba0.925La0.075)(Mg0.36Nb0.64)O3 (BLMN) were carried out using high-resolution transmission electron microscopy (HRTEM) and synchrotron powder X-ray diffractometry (XRD). In both samples, not only 1:1 and 1:2 ordered domains coexisted in a single grain, but also the intermediate phase, whose structure had a superlattice modulation of 1.42 nm, which was equivalent to 6 times the unit cube of disordered perovskite found on the nanoscale. The ordered 1:2 domains gradually transformed to 1:1 ordered structure through the formation of an intermediate superlattice structure that comprised 6 × 6 × 6 cubic unit cells with different chemical orderings of B-site ions in B-site lattices. Also, the features of thin plates could be detected by XRD patterns and HRTEM. When the thicknesses were very thin, about several atomic distances, stacking faults occurred on (111) planes. However, when their thicknesses were 〉50 nm, the thin plates existed as a transition phase with their own structure. They were coherent with the matrix and continuously decomposed into the matrix phase by the lateral migration of the interfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1999.tb02115.x
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