Dependence of depolarization temperature on cation vacancies and lattice distortion for lead-free 74(Bi_(1/2)Na_(1/2))TiO_3-20.8(Bi_(1/2)K_(1/2))TiO_3-5.2BaTiO_3 ferroelectric ceramics

摘要

In this paper, the off-morphotropic-phase-boundary 74(Bi_(1/2)Na_(1/2))TiO_3-20.8(Bi_(1/2)K_(1/2))TiO_3-5.2BaTiO_3rn ceramics were fabricated at different sintering temperatures. It was found out that as the sintering temperature increases, the volatilization of the A-site elements is aggravated, thus generating the oxygen vacancies; meanwhile, the tetragonality of the perovskite lattice reduces gradually. Besides, the temperature-dependent dielectric responses revealed that as the sintering temperature increases, the depolarization temperature T_d decreases while the Curie-Weiss point T_C increases. It is suggested that the lattice distortion, other than the oxygen vacancies, is the crucial factor in influencing the depolarization temperature.