Phase transition temperature and electrical properties of (Bi1/2Na1/2)TiO3-(Bi1/2A1/2)TiO3 (A=Li and K) lead-free ferroelectric ceramics

(1-x)(Bi(1/2)Na(1/2))TiO(3)-x(Bi(1/2)Li(1/2))TiO(3) and (1-x)(Bi(1/2)Na(1/2))TiO(3)-x(Bi(1/2)K(1/2))TiO(3) (abbreviated as BNLT100x and BNKT100x, respectively) ceramics were prepared by the conventional ceramic fabrication process. In this study, the depolarization temperature T(d), rhombohedral-tetragonal phase transition temperature T(R-T), and the temperature of the maximum dielectric constant T(m) were determined from the temperature dependences of the dielectric and piezoelectric properties. The results showed that T(d) of BNLT100x and BNKT100x increased to 199 and 209 degrees C, respectively, at the rhombohedral composition. In addition, we revealed that T(d) is related to the magnitude of the rhombohedrality 90-alpha and the tetragonality c/a. We studied the piezoelectric properties in detail, and the relationship between T(d) and piezoelectric properties was clarified. Moreover, we discussed the ferroelectricity of the middle phases of T(d)-T(R-T) and T(R-T)-T(m). (C) 2008 American Institute of Physics.