Achieving large electrostrain in 0.94(Bi_0.5Na_0.5)TiO₃-0.06BaTiO₃ Pb-free piezoelectric ceramics via phase transition and domain engineering

Piezoelectric ceramics have been extensively applied in various electronic devices, owing to their substantial electrostrain capacity. Bi_0.5Na_0.5TiO₃-based ceramics are regarded as one of prospective substitute for lead-based piezoelectric ceramics on account of their rival electrostrain ability. In current study, the modifications of phase transition and domain structure by compositional regulation and phase boundary engineering are widely employed to enhance the electrostrain property. So, a series of (1-x)(0.94(Bi_0.5Na_0.5)TiO₃-0.06BaTiO₃)-xSr(Sn_0.5Hf_0.5)O₃ were prepared through a traditional solid-state reaction route. The correlations among Sr(Sn_0.5Hf_0.5)O₃ (SSH) composition, ceramic microstructure, and the electrostrain properties were established through a systematic investigation. Within all the designed compositions of the ceramic samples, BNBT-0.020SSH ceramics exhibited excellent electrostrain performance, attributing to the ergodic relaxor state, which enables a strain response of 0.41% under an relatively undemanding applied field of 60 kV/cm, whilst simultaneously exhibiting a remarkably high piezoelectric strain coefficient (d∗ 33) of 683 p.m./V. Moreover, the strain exhibited a variation of no more than 10% from ambient temperature up to 90 °C, demonstrating very good temperature-insensitive characteristics. Beyond that, this composition also exhibited excellent frequency stability, with d₃₃∗ remaining above 600 p.m./V from 1 to 50 Hz. Thus, this work offers both a compelling strategy for achieving high electrostrain and a promising material candidate for next-generation piezoelectric actuators.