IMF2017

Electromechanical materials (mainly ferroelectric materials) can convert electrical energy to mechanical work and have been widely used in actuators, ultrasonic imagines and telecommunciations. However, the combination of low hystersis and large strain with good thermal stability has been hardly attained in ferroelectric materials since the discovery in 1920. Here we report an exceptional combination of low hysteresis (< 10%) and large electrostrain (0.16% at 6 kV/mm) over a broad temperature range (~80 K) in a lead-free (Ba_0.925Bi_0.05)(Ti_1-x/100Sn_x/100)O₃ (BT-5Bi-xSn) ceramic system. Moreover, it is against the conventional hysteresis-strain trade-off, i.e., both hysteresis and strain properties become better. In-situ transmission electron microscopy observations further reveal a "frozen" heterogeneous microstructure of isolated ferroelectric domains embedded into relaxor matrix over a broad temperature range, namely the re-entrant relaxor-ferroelectric composite (RRFC). This RRFC serves as the origin of the property anomalies: reversible non-180^o polarization rotation with negligible irreversible domain wall motion over a broad temperature range, which is different from previous well-known wisdoms of morphotropic phase boundaries in ferroelectrics or polar nanoregions in relaxors. Our work may open a new way to develop high-performance electromechanical materials.