Temperature dependence of dielectric properties and phase transition behavior in quenched (Bi_0.5Na_0.5)TiO₃ ceramics

Lead-free piezoelectric (Bi_0.5Na_0.5)TiO₃ (BNT) ceramics, which exhibit a Bi-based A-site complex perovskite structure with rhombohedral symmetry, were prepared by controlling: the quenching temperature and the quenching rate (QR). We examined the relationship between structural order and quenching effect of the structural phase transition behavior, which was obtained from the dielectric properties. Additionally, the electrical properties were evaluated. These measurements showed that the depolarization temperature (T_d) increased by approximately 50 °C during these two control processes. Furthermore, the full width at half maximum (FWHM) for temperature dependence of tan δ decreased with increasing quenching temperature and QR. In conclusion, the increase in T_d is strongly correlated with the decrease in FWHM, which suggests a more ordered arrangement of cations, Bi³⁺ and Na⁺, in the Bi-based A-site complex perovskite structure. Moreover, the quenching effect does not deteriorate the piezoelectric properties. (author)