Piezoelectric properties of (Bi_0.5Na_0.5)TiO₃–BaTiO₃ ceramics poled by direct current electric field above curie temperature

Abstract

Lead-free (1 − x)(Bi_0.5Na_0.5)TiO₃–xBaTiO₃ (abbreviated as BNT–BT, x = 0.05–0.55) ceramics were synthesized by solid-state reaction, and their crystal structures, dielectric and ferroelectric properties were investigated in detail. For poling treatment, a special poling strategy was conducted, which is applying a direct current electric field above the Curie (or phase transition) temperature on the BNT–BT ceramics. The Curie (or phase transition) temperatures of BNT–BT samples were determined by temperature dependence of polarization versus electric field measurement. The piezoelectric coefficient d₃₃ of poled BNT–BT samples were calculated from their resonance curves. Among them, the 0.875BNT–0.125BT was considered an interesting composition due to the relatively high phase transition temperature (>200 °C), and it showed a d₃₃ value of 88.6 pC/N and a coupling factor k₃₃ of 38.8 % after poling above its phase transition temperature. This work may contribute to optimizing the poling treatment for BNT–BT system.