Optimized strain properties with small hysteresis in BNT-based ceramics with ergodic relaxor state

Electric field-induced high strain with small hysteresis and good temperature stability is necessary for piezoactuators devices. Most of previous works focus on the giant strain achieved in Bi0.5Na0.5TiO3 (BNT)-based ceramics through electric field-induced transition from nonergodic relaxor to ferroelectric state, while the high remnant strain or/and large hysteresis are always accompanying. In this work, through enhancing the local polarization by rare earth ions doping (e.g., La3+), we propose to improve the strain properties of BNT-based lead-free ceramics with ergodic relaxor state which displays the near zero remnant strain, small hysteresis, high temperature stability but the low strain value. The addition of La3+ would not change the ergodic relaxor state, but can improve the short-range correlation of local polar nanoregions, cut down the critical electric field of transition between relaxor and ferroelectric states, and elevate the electrostrictive effect of ceramics. Finally, high strain of ∼0.3 % with low hysteresis of ∼8−30 % was obtained in the broad temperature range from room temperature to 100 °C, which is superior to previous BNT-based ceramics and other lead-based/lead-free ceramics. This work affords a paradigm to regulate the ergodic relaxor state to optimize the strain properties, which give the significant guide for strain developments.