Influence of Sintering Atmosphere on Abnormal Grain Growth Behaviour in Potassium Sodium Niobate Ceramics Sintered at Low Temperature

The present study aims to identify the effect of sintering atmosphere [O-2, 75N(2)-25 H-2 (mol%) and H-2] on microstructural evolution at the relatively low sintering temperature of 1040 degrees C. Samples sintered in O-2 showed a bimodal microstructure consisting of fine matrix grains and large abnormal grains. Sintering in 75 N-2 - 25 H-2 (mol %) and H-2 caused the extent of abnormal grain growth to increase. These changes in grain growth behaviour are explained by the effect of the change in step free energy with sintering atmosphere on the critical driving force necessary for rapid grain growth. The results show the possibility of fabricating (K0.5Na0.5)NbO3 at low temperature with various microstructures via proper control of sintering atmosphere.