Effect of TiO2 addition on grain shape and grain coarsening behavior in 95Na1/2Bi1/2TiO3–5BaTiO3

Grain coarsening behavior in the 95Na1/2Bi1/2TiO3–5BaTiO3 system has been studied as a function of the addition of TiO2. As the amount of added TiO2 was increased, the grain shape changed to a more faceted cube, indicating an increase in the step free energy of the facets, and hence a rise in the critical driving force for appreciable growth of grains. Grain coarsening behavior also changed from pseudo-normal to abnormal with an increasing TiO2 concentration and thus increased faceting. The pseudo-normal behavior observed in the system without TiO2 addition also changed to quite abnormal behavior during extended sintering. These observations support our theoretical prediction based on the coupling effects between the maximum driving force for growth and the critical driving force for appreciable growth.