Dynamics of polarization reversal in virgin and fatigued ferroelectric ceramics by inhomogeneous field mechanism

Temporal behavior of ferroelectric ceramics during the polarization switching cannot be satisfactorily explained by simple Debye or even stretched exponential laws. These materials exhibit rather a wide spectrum of characteristic times interpreted by different authors as switching or nucleation waiting times, the physical reasons for a wide time distribution still remaining unclear. A new model of polarization switching presented here suggests that the characteristic time variance in the ferroelectrics originates from the random distribution of the local electric fields due to intrinsic randomness of the material. The presented theory allows a direct extraction of the distribution of field values from the experiment. Systematic studies of polarization switching in fatigued lead zirconate titanate demonstrate the evolution of the field distribution with increasing level of fatigue. Plausible cause of the formation of regions subject to different field strengths is the generation of defects such as microcracks, pores, or voids in the course of fatigue. Suitability of the proposed model is demonstrated by an excellent correlation between experimental and calculated data for virgin and differently fatigued samples in a broad time-field region covering the electric field values of 0.5-2.5 kV/mm and nine orders of the magnitude of poling time.