Aging-induced double ferroelectric hysteresis loops in BiFeO3 multiferroic ceramic

Double ferroelectric hysteresis (P-E) loops are observed in aged BiFeO3 multiferroic ceramic at room temperature and are explained according to an aging effect driven by charged defects with high activation energy. The aged BiFeO3 shows R3c defect symmetry and allows a nonzero charged defect-induced polarization (P-D) below the ferroelectric Curie temperature. This P-D is strong enough to recover the switched 180 degrees ferroelectric domains upon the removal of E, but it is rather weak to effectively switch back the 71 degrees/109 degrees ferroelectric domains. As a result, the traits of the double P-E loops weaken with increasing the maximum E from 121 to 167 kV/cm.