Dissipative Domain Wall Motion and Macroscopic Response of Ferroelectric Ceramics

We present a model which is based on the notion of a polycrystalline material with grains having a lamellar domain structure. The domain stack is homogenized by analytical methods whereas the interaction of grains is taken into account by the effective medium approximation. Domain wall motion is allowed to take place by considering the total potential energy variation of the polycrystalline material in comparison with microscopic retarding forces. The model is numerically evaluated with data for barium titanate single-crystals. Thus the hysteretic material behavior occurring under large-signal unipolar loading can be correlated with the dissipative domain wall motion. We also get some quantitative information on the fluctuating internal fields.