Grain-Growth Behavior during Stepwise Sintering of Barium Titanate in Hydrogen Gas and Air

To study the effect of oxygen partial pressure on grain growth in BaTiO₃, TiO₂-excess samples have been sintered in air with and without a prior H₂ heat treatment. Without prior H₂ treatment, abnormal grain growth occurs below and above the eutectic temperature ( T _e). An introduction of H₂ treatment before air sintering, however, increases the average grain size and suppresses the formation of abnormal grains during subsequent air sintering below and above T _e. This H₂ treatment effect has been explained in terms of a decrease of the driving force for the growth of faceted grains below a critical value for formation of abnormal grains. The observed grain-growth behavior under various atmospheres demonstrates the possibility of having various microstructures via control of oxygen partial pressure and initial grain size.