Effect of step free energy on delayed abnormal grain growth in a liquid phase-sintered BaTiO3 model system

The changes in solid/liquid interface structure and grain growth behavior with oxygen partial pressure (PO2) were systematically studied during liquid-phase sintering of 8TiO2/2SiO2-added BaTiO3. As the PO2 of the sintering atmosphere increased, the grain boundaries and solid/liquid interfaces showed increased faceting, indicating an increase in step free energy. This increase in PO2 and step free energy caused a change in grain growth behavior as a function of sintering time. When samples were sintered in H2, abnormal grain growth (AGG) occurred from the beginning, resulting in a coarse microstructure with a large average grain size. With increasing PO2, the incubation time necessary for AGG also increased. Finally, for samples sintered in air, AGG did not occur even after 100 h. These changes in incubation time for abnormal grain growth demonstrate the effect of changing the step free energy on the microstructural development during liquid phase sintering of ceramic systems.