Effect of Ba Substitution on Dielectric and Piezoelectric Properties of Lead-Free Bi1/2(Na0.82K0.18)1/2TiO3 Ceramics

Lead-free piezoelectric [(1-x)Bi-1/2(Na0.82K0.18)(1/2) + xBa]TiO3 ceramics (x = 0, 0.01, 0.02, 0.03, 0.04, 0.05) were synthesized by a conventional solid-state reaction method. The effect of Ba substitution on crystal structure, dielectric, ferroelectric and piezoelectric properties of Bi-1/2(Na0.82K0.18)(1/2)TiO3 (BNKT) ceramic was investigated. A phase transition from the coexistence of rhombohedral and tetragonal to tetragonal phase with the rhombohedral distortion gradually diminished was observed at x = 0.02, and the tetragonality (c/a) was found to increase with increasing Ba content. The temperature and frequency dependence of the dielectric curves exhibited that BNKT-Ba ceramics show relaxor characteristics with diffuse phase transition. However the diffuse character of the ceramics was inhibited with increasing Ba content. The depolarization temperature, T-d increased with increasing Ba substitution. Enhanced remnant polarization and piezoelectric coefficient of 33 mu C/cm(2) and 158 pC/N, respectively were obtained at low substitution of Ba (x = 0.01).