Ultrahigh electrostrain with excellent fatigue resistance in textured Nb⁵⁺-doped (Bi_0.5Na_0.5)TiO₃-based piezoceramics

(Bi_0.5Na_0.5)TiO₃ (BNT)-based lead-free piezoceramics exhibit excellent electric field-induced strain (electrostrain) properties, but often suffer from large hysteresis and poor fatigue resistance, which strongly limit their applications. Here, <00l> textured Nb⁵⁺-doped 0.8(Bi_0.5Na_0.5)TiO₃–0.2(Bi_0.5K_0.5)TiO₃ (0.8BNT–0.2BKT) ceramics with a high degree of texturing (~80%) were prepared by the reactive template grain growth (RTGG) method using Bi₄Ti₃O₁₂ as a template. By the combination of donor doping in the B-site and the RTGG method, the electrostrain performance achieves a significant enhancement. A high electrostrain of 0.65% and a piezoelectric coefficient ( $d_{33}^{*}$) of 1083 pm/V with reduced hysteresis at an electric field of 6 kV/mm are obtained. No electrostrain performance degradation is observed after unipolar electric field loading of 10⁵ cycles, showing excellent fatigue endurance. These results indicate that the texturing BNT-based lead-free piezoceramics by the RTGG method is a useful approach to developing eco-friendly actuators.