Tailoring electromechanical performance in BiScO₃-modified Bi_0.5Na_0.5TiO₃-based lead-free piezoceramics

The strain response of lead-free ternary solid solution (1 − x) (0.94 Bi_0.5Na_0.5TiO₃–0.06BaTiO₃)–xBiScO₃ (BNT–BT–BS) have been tailored by controlling the phase transition temperature. The effects of BiScO₃ on the phase structure, dielectric, ferroelectric, piezoelectric properties, and electric field-induced strain are systematically investigated. A schematic phase diagram has also been established to clarify the relationship between strain behavior and structure evolution. The field-induced strain increases progressively, and a large strain of 0.35% with S_max/E_max = 471 pm/V is achieved at the critical composition x = 0.03, owing to the shift of the ferroelectric-to-relaxor transition temperature T_F–R to ambient temperature. Intriguingly, the established correlation between strain response and T_F–R demonstrates that the optimization of strain behavior of BNT-based ceramics can be realized though the regulation of T_F–R to room temperature. Furthermore, a high and thermally stable electrostrictive coefficient Q₃₃ of 0.018 m⁴/C² can also be attained at the composition x = 0.06. In this study, it is believed that the modulation of phase transition temperature is feasible to achieve the large strain response in BNT-based ceramics.