Ultra-slim pinched polarization-electric field hysteresis loops and thermally stable electrostrains in lead-free sodium bismuth titanate-based solid solutions

Electric field-induced strains (electrostrains) with high amplitude, high thermal stability and ultra-low hysteresis are of great interest both in fundamental researches and industrial applications, such as high-precision displacement actuators. In this work, we present a strategy to fulfil these requirements via a relaxor antiferroelectric-like material that possesses intriguing antiferroelectric and relaxor characteristics simultaneously. Its antiferroelectric state would result in high electrostrains because of the electric-field induced antiferroelectric-to-ferroelectric phase transition, while the relaxor state would boost the temperature stability and ultra-slim hysteresis of electrostrains. According to this strategy, we obtained high electrostrains (>0.1% at 60 kV/cm) accompanying with good temperature stability (variation of strain < 20% from 30 °C to 120 °C) and ultra-low hysteresis (<7%) in lead-free (Bi_0.5Na_0.5)TiO₃-x(Sr_0.7Bi_0.2)TiO₃ (BNT-xSBT) solid solutions. The thermal stability of the electrostrains is directly correlated to the thermal stability of polarization based on electrostrictive effect. The electrostrictive coefficient in this system is discussed in detail. This work not only proves the effectiveness of this strategy, but also paves a way to search high electrostrains with good thermal stability and ultra-low hysteresis in unique BNT-based solid solutions.