Twins and grain growth during liquid-phase sintering of BaTiO3 ceramics

“…The platelike abnormal grains are also known to be bounded by {111} planes. 15 R. E. Riman-contributing editor journal When the specimens were heat-treated at 1280°C for 30 min, AGG was observed to occur, as shown in Fig. 2.…”

Section: Methodsmentioning

confidence: 98%

Effect of Twin‐Plane Reentrant Edge on the Coarsening Behavior of Barium Titanate Grains

Lee¹,

Kim²,

Kim³

2002

Journal of the American Ceramic Society

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When BaTiO 3 ceramics were sintered at relatively low temperatures (<1250°C), the grains with reentrant edges caused by a (111) double twin grew exclusively. As a result, a microstructure with a bimodal grain-size distribution composed of platelike large grains and fine matrix grains was obtained. In contrast, at the usual sintering temperature between 1250°and 1350°C, grains containing a (111) double twin did not exhibit any growth advantage. In this case, a coarse and uniform microstructure was obtained. When this coarse-grained specimen was further heat-treated at 1365°C, the grains possessing a double twin were observed to grow exclusively again. The results were explained in terms of a coarsening process controlled by two-dimensional nucleation.

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“…These are commonly observed in BT powders and ceramics processed in air. Many authors 29,30 have correlated twinning with exaggerated grain growth, in particular anisotropic grain growth. Nevertheless, there is experimental evidence that the existence of {111} twins alone is not sufficient to trigger anomalous grain growth as initially proposed by Schmelz and Thomann 31 .…”

Section: Discussionmentioning

confidence: 99%

Structure–Property Relationships of BaTi_1−2yGa_yNb_yO₃ (0≤y≤0.35) Ceramics

Feteira

Sinclair

Reaney

et al. 2005

Journal of the American Ceramic Society

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BaTi1−2yGayNbyO3 (BTGN) (0≤y≤0.35) powders were synthesized at 1300°C by the conventional solid‐state method. Room temperature x‐ray diffraction patterns for y≤0.025 and 0.05≤y≤0.30 can be indexed as the tetragonal (P4mm) and cubic (Pm m) polymorphs of BaTiO3, respectively, whereas y=0.35 consists of a mixture of the cubic polymorph of BaTiO3 and an 8H hexagonal‐type perovskite (P63/mcm) isostructural with Ba8Ti3Nb4O24. Scanning electron microscopy shows the microstructures of BTGN ceramics (y≤0.30) sintered at 1500°C to consist of fine grains (1–3 μm) within a narrow grain size and shape distribution. Room temperature transmission electron microscopy for y≤0.08 reveals core–shell structures and (111) twins in some grains; however, their relative volume decreases with y. Energy dispersive spectroscopy reveals the cores to be Ga and Nb deficient with respect to y. For y>0.08 there is no evidence of core–shell structures, however, some grains have a high density of dislocations, consistent with chemical inhomogeneity. BTGN ceramics exhibit a diverse range of dielectric behavior in the temperature range 120–450 K and can be subdivided into two groups. 0.025≤y≤0.15 display modest ferroelectric relaxor‐type behavior, with high room temperature permittivity, ɛ25′, (>300 at 10 kHz), whereas 0.25≤y≤0.30 are temperature and frequency stable dielectrics with ɛ25′<100 that resonate at microwave frequencies with modest quality factors, Q×f, ∼3720 GHz (at ∼5 GHz) for y=0.30.

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Twins and grain growth during liquid-phase sintering of BaTiO3 ceramics

Cited by 12 publications

References 6 publications

Electrical properties and structure of grain boundaries in n-conducting BaTiO3 ceramics

Electrical properties and structure of grain boundaries in n-conducting BaTiO3 ceramics

Effect of Twin‐Plane Reentrant Edge on the Coarsening Behavior of Barium Titanate Grains

Structure–Property Relationships of BaTi_1−2yGa_yNb_yO₃ (0≤y≤0.35) Ceramics

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Twins and grain growth during liquid-phase sintering of BaTiO3 ceramics

Cited by 12 publications

References 6 publications

Electrical properties and structure of grain boundaries in n-conducting BaTiO3 ceramics

Electrical properties and structure of grain boundaries in n-conducting BaTiO3 ceramics

Effect of Twin‐Plane Reentrant Edge on the Coarsening Behavior of Barium Titanate Grains

Structure–Property Relationships of BaTi1−2yGayNbyO3 (0≤y≤0.35) Ceramics

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Structure–Property Relationships of BaTi_1−2yGa_yNb_yO₃ (0≤y≤0.35) Ceramics