Simulation of microstructure evolution in polycrystalline ferroelectrics–ferroelastics

A thermoactivation analysis of experimental data is used along with a constitutive model to determine the microscopic parameters of domain wall dynamics in polycrystalline ferroelectrics–ferroelastics. The proposed constitutive model takes into account thermally activated processes assisting domain walls to overcome the energy barriers of short-range obstacles. The microstructure in polycrystals is described effectively, employing the volume fractions of ferroelectric domains with different polarization orientations as structural (internal) variables, and its evolution is given in terms of rate equations for these variables. The average polycrystal properties are computed using a discrete orientations approximation (a set of representative orientations) for the distribution function of grain orientations. Assuming that the domain wall mobility depends on temperature according to the Arrhenius equation, the microscopic parameters of the model including the obstacle strength and activation energy are extracted from the temperature dependence of the coercive field. Using experimental data for doped lead zirconate titanate (PZT) ceramics, it is shown that within the framework of the constitutive model the “soft” and “hard” PZT compositions differ considerably, not only in defect strength but also in activation volume.