Aging effect and large recoverable electrostrain in Mn-doped KNb O3 -based ferroelectrics

KNb O3 -based ferroelectrics have drawn much attention in recent years owing to their good piezoelectric performance among Pb-free piezoelectrics. However, little is known about the aging effect of these materials. In the present study, the authors systematically studied the aging effect of a Mn-doped (K0.99 Li0.01) (Nb0.65 Ta0.35) O3 ceramic with an aim to find an aging-induced recoverable electrostrain effect based on a reversible domain switching mechanism. They found that aging in the ferroelectric state made the otherwise normal hysteresis loop into a double loop, and more interestingly the aged sample demonstrated a large recoverable electrostrain of 0.125% at 4 kVmm in an unpoled state. Such a behavior persisted up to 140 °C and showed good recoverability. The aging-induced double hysteresis and recoverable electrostrain suggest a reversible domain switching mechanism due to a symmetry-conforming short-range ordering of point defects. The striking similarity of the aging effect between acceptor-doped A+ B5+ O3 and acceptor-doped A2+ B4+ O3 systems indicates a common physical origin of aging.