A novel multi-component lead-free (1−x)BF–xBT–0.01(BNT–20BKT) piezoelectric ceramic exhibits excellent high-temperature piezoelectric properties and thermal stability

Abstract

This paper uses the conventional solid-state reaction method to prepare (1−x)BiFeO₃–xBaTiO₃–0.01[0.8(Bi_0.5Na_0.5)TiO₃–0.2(Bi_0.5K_0.5)TiO₃]-(referred to as (1−x)BF–xBT–0.01(BNT–20BKT), 0.27 ≤ x ≤ 0.35). The influence of BaTiO₃ content on the phase structure, dielectric properties, and piezoelectric properties of the BF–BT–BNT–BKT ceramics was systematically investigated. The XRD results indicate that with increasing BaTiO₃ content, the material undergoes a composition-induced phase transition from the rhombohedral phase (R) to the pseudocubic phase (P_C). Within the composition range 0.27 ≤ x ≤ 0.31, a metamorphic phase boundary (MPB) forms where the R phase and P_C phase coexist. In situ d₃₃ testing results indicate that at x = 0.31, an ultra-high piezoelectric property of 687.8 pC N⁻¹ was achieved at a real-time depolarisation temperature (T_dr) of 381.8 °C, reflecting the ceramic's real-time piezoelectric properties and exceptional high-temperature stability. Transmission electron microscopy results indicate that nanodomains and polar nanodomains play a crucial role in enhancing the piezoelectric response. This study provides novel insights and experimental references for the composition design and phase structure regulation of high-performance lead-free piezoelectric ceramics.