The effect of porosity and grain boundary structure on abnormal grain growth has been investigated in a 0.4mol% TiO2 excess-BaTiO3 model system. The powder compacts were pre-sintered at 1250°C for 30min or 3h in H2 atmosphere to make the samples with different average grain sizes; 1.3??m or 2.4??m. Pre-sintered samples were sintered in air for a short period of time to create porosities of 9% and 5%, respectively. The samples were sintered in different oxygen partial pressures. Abnormal grains with an isotropic shape were observed only in samples of the small grain size (1.3??m) sintered at Po2=10-18~10-15 regardless of the porosity. In samples with large grain size (2.4μm) and with different porosities showed stagnant grain growth. The observed stagnant grain growth can be attributed to the presence of a critical driving force for migration of the boundary, which is apparently larger than the maximum driving force for boundary migration. These experimental observations suggest that pore/boundary separation is not a cause of abnormal grain growth in the studied experimental condition, but the boundary faceting and boundary migration of faceted boundaries are the direct cause.
The effect of porosity and grain boundary structure on abnormal grain growth has been investigated in a 0.4mol% TiO2 excess-BaTiO3 model system. The powder compacts were pre-sintered at 1250°C for 30min or 3h in H2 atmosphere to make the samples with different average grain sizes; 1.3??m or 2.4??m. Pre-sintered samples were sintered in air for a short period of time to create porosities of 9% and 5%, respectively. The samples were sintered in different oxygen partial pressures. Abnormal grains with an isotropic shape were observed only in samples of the small grain size (1.3??m) sintered at Po2=10-18~10-15 regardless of the porosity. In samples with large grain size (2.4μm) and with different porosities showed stagnant grain growth. The observed stagnant grain growth can be attributed to the presence of a critical driving force for migration of the boundary, which is apparently larger than the maximum driving force for boundary migration. These experimental observations suggest that pore/boundary separation is not a cause of abnormal grain growth in the studied experimental condition, but the boundary faceting and boundary migration of faceted boundaries are the direct cause.
