Temperature Dependence of Electric Properties of [Bi_0.5(Na_1-xAg_x)_0.5]_1-yBa_yTiO₃ Ceramics

The temperature dependence of the piezoelectric and dielectric properties of lead-free piezoelectric ceramics, namely, [Bi_0.5(Na_1-xAg_x)_0.5]_1-yBa_yTiO₃ (abbreviated as BNBTy–xAg, x=0–6 mol % and y=0–10 mol %), was investigated, and the features of the depolarization temperature (T_d) of the ceramics were discussed. The temperature dependence of the piezoelectric properties shows that the piezoelectric constant (d₃₃) decreases sharply and that the piezoelectricity almost disappears at T_d for all of the ceramic samples. With an increase in the amount of Ag⁺, the T_d of the BNBT6–xAg ceramics decreases. Moreover, the T_d of the BNBTy–4Ag ceramics decreases with an increase in the amount of Ba²⁺ up to 6 mol %, and then increases with a further increase in the amount of Ba²⁺. Furthermore, the temperature dependence of the dielectric properties shows that the characteristic of the diffuse phase transition is more evident for the compositions near the morphotropic phase boundary (MPB).