Constitutive Relations of Ferroelectric Ceramics with Electric Fatigue Effects

Recent experiments have demonstrated that cyclic electric loading may cause polarization switching fatigue of ferroelectric ceramics. We formulate a novel constitutive model for ferroelectric ceramics with electric fatigue induced by the two most important physical mechanisms, i.e. accumulation of point defects (or microcracking damage) and domain wall pinning. The local domain pinning effect is considered to be associated with the nonhomogeneous spatial distribution of positive and negative space charges. The proposed model can elucidate various experimental phenomena reported in the literature. It is found that the electric property of space charges has an essential effect on the asymmetry of strain hysteresis loops while point defects influence the change of remanent polarization and coercive field.