Giant strain with ultra-low hysteresis by tailoring relaxor temperature and PNRs dynamic in BNT-based lead-free piezoelectric ceramics

State-of-the-art ferroelectric materials with large field-induced strain together with low hysteresis are required in high precision or positioning devices. However, the high electro-strain is always suffered from a large strain hysteresis, severely restricting its practical application. In this study, the relaxor temperature (Tf) of BNT-6BT near the morphotropic phase boundary with initially high polarization was adjusted to near room temperature by adding Sr0.7La0.2TiO3. The room temperature relaxation properties feature with the high dynamic polar nanoregions with moderate polar spatial correlations, which paired the high strain (0.325%) and ultra-low hysteresis (8.02%). This actuation strain is superior to those of previously reported lead-free piezoelectric materials. Meanwhile, the strain responses also displayed outstanding temperature and frequency stability from 30°C to 150 °C and 1 Hz–25 Hz, respectively, indicating its practical application potential. The results will provide new insight into the design of high-performance BNT-based ceramics for use in actuators.