Grain Growth Behavior of 0.95(Na_0.5Bi_0.5)TiO₃–0.05BaTiO₃ Controlled by Grain Shape and Second Phase

Abstract

The grain growth behavior of 0.95(Na0.5Bi0.5)TiO3 −0.05BaTiO3 (mole fraction, NBT−5BT) grains was investigated with excess Bi2O3 addition. The powder compacts of NBT−5BT were sintered at 1200 °C for various sintering times and with various amounts of Bi2O3 (0.1, 1.5, 4.0 and 10.0 mol%). When Bi2O3 was added to round-edged cubic NBT−5BT, the grain shape changed to a more faceted cube and the amount of liquid phase increased during sintering. A more faceted cubic grain shape indicates an increase in the critical driving force for appreciable growth of grains. However, obvious abnormal grain growth did not appear in any of the NBT−5BT samples with excess Bi2O3. The amount of liquid phase increased as the amount of Bi2O3 increased. Therefore, the rate of grain growth could be decreased by the increasing the distance for the diffusion of atoms. These observations allowed us to conclude that the growth of Bi2O3-excess NBT−5BT grains is governed by the growth of facet planes via the two-dimensional nucleation grain growth mechanism during changing grain shape and amount of liquid.

Keywords

• grain growth
• grain shape
• liquid phase
• sintering
• microstructure
• nbt-bt