Aging effect and large recoverable electrostrain in Mn-doped KNbO3-based ferroelectrics

KNbO3-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 (K0.99Li0.01)(Nb0.65Ta0.35)O-3 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 kV/mm in an unpoled state. Such a behavior persisted up to 140 degrees 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(+)B(5+)O(3) and acceptor-doped A(2+)B(4+)O(3) systems indicates a common physical origin of aging. (C) 2007 American Institute of Physics.