Critical Grain Size for Abnormal Grain Growth of BaTiO_3 in Air(Sintering and Microstructure,<Special Issue>Guest Editors Dedicated to Prof. Gunter Petzow: Modern Trends in Advanced Ceramics)

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The critical average size of matrix BaTiO_3 grains for {111} twin-assisted abnormal grain growth in air was determined through the use of bi-layer samples of large BaTiO_3 grains with {111} twin lamellae and fine matrix grains of various sizes. Plates with large BaTiO_3 grains containing {111} twin lamellae were prepared by sintering 0.4mol%-TiO_2-added BaTiO_3 powder compacts at 1250℃ for 20h in air. Additionally, plates with matrix grains having various grain sizes were prepared by sintering BaTiO_3 powder compacts at 1300℃ for 0.5, 2, 8 and 48h in H_2. Abnormal growth of the twin-containing large grains into matrix grains occurred for the matrix grain size of 4.1μm and did not occur for that of 5.6μm. It appears, therefore, that the critical size for abnormal grain growth is approximately 5μm, which correspond to a critical driving force of 4.6J/mol. The commonly observed abnormal grain growth during sintering of undoped BaTiO_3 in air is, hence, understood to result from much higher driving forces of fine powders than the critical value.
社団法人日本セラミックス協会の論文
2006-11-01