Effect of BiCoO3 on piezoelectric properties and depolarization temperature of BNT-BKT piezoelectric ceramics

A Bi-based perovskite-type lead-free piezoelectric ceramic, (1-x)Bi0.5 (Na0.82K0.18)0.5 TiO3-xBiCoO3, was prepared by a conventional ceramic sintering technique. The effect of BiCoO3 on microstructure, piezoelectric properties and depolarization temperature was investigated. X-ray diffraction patterns indicate that the ceramics can form pure perovskite structure solutions. The crystal structure of the ceramics varies from co-existence of rhombohedral-tetragonal phases to pseudocubic phase with increasing the BiCoO3 content. The grain size increases evidently with increasing the BiCoO3 content. The optimum piezoelectric properties of d33=148 pC/N and kp=0.329 are obtained at x=0.01. The depolarization temperatures are confirmed by temperature dependence of kp and θmax, and it decreases with the increase of BiCoO3 content.