Dependence of depolarization temperature on cation vacancies and lattice distortion for lead-free 74(Bi1/2Na1/2)TiO3-20.8(Bi1/2K1/2)TiO3-5.2BaTiO3 ferroelectric ceramics

In this paper, the off-morphotropic-phase-boundary 74(Bi1/2Na1/2)TiO3-20.8(Bi1/2K1/2)TiO3-5.2BaTiO(3) 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.