The temperature-dependent electrical properties of Bi0.5Na0.5TiO3–BaTiO3–Bi0.5K0.5TiO3 near the morphotropic phase boundary Original Research Article

Bi0.5Na0.5TiO3–BaTiO3–Bi0.5K0.5TiO3 (BNT–BT–BKT) lead-free piezoceramics with compositions near the rhombohedral–tetragonal morphotropic phase boundary (MPB) were prepared and investigated. At room temperature, all ceramics show excellent electrical properties. In this study, the best properties were observed in 0.884BNT–0.036BT–0.08BKT, with the remnant polarization, bipolar total strain, unipolar strain, piezoelectric constant, and planar electromechanical coupling factor being 34.4 μC cm−2, 0.25%, 0.15%, 122 pC N−1, and 0.30, respectively. Detailed analysis of the temperature dependence of polarization–electric field (P–E) loops and bipolar/unipolar strain–electric field (S–E) curves of this composition revealed a ferroelectric–antiferroelectric phase transition around 100 °C. Around this temperature, there is a significant shape change in both P–E and S–E curves, accompanied by enhanced strain and decreased polarization; the largest recoverable strain reaches 0.42%. These results can be explained by the formation of antiferroelectric order and the contribution of field-induced antiferroelectric–ferroelectric phase transition to piezoelectric response. Our results indicate that BNT–BT–BKT lead-free piezoceramics can have excellent electrical properties in compositions near the MPB and also reveal some insight into the temperature dependence of the electrical performance with the MPB composition.