Aging-induced, defect-mediated double ferroelectric hysteresis loops and large recoverable electrostrains in Mn-doped orthorhombic KNbO3-based ceramics

Double ferroelectric hysteresis (P–E) loops and large recoverable electrostrains of >0.13% at 5 kV/mm are observed in aged Mn-doped orthorhombic KNbO3-based [K(Nb0.90Ta0.10)O3] lead-free ceramics over a wide temperature range of 25–140 °C. The observations are found to have striking similarities to tetragonal ferroelectrics, besides following a point defect-mediated reversible domain switching mechanism of aging driven by a symmetry-conforming short-range ordering (SC-SRO) of point defects. Such aging effects, being insensitive to crystal structure and constituent ionic species, provide a useful way to enhance electromechanical properties of lead-free ferroelectric material systems.