IMF2017

The switching time distribution plays a crucial role in polarization reversal of polycrystalline ferroelectric materials. As the switching time is strongly field dependent, the field distribution has a great impact on the time-dependent ferroelectric poling. The current work is dedicated to investigation of switching kinetics in ferroelectric ceramics. The main kinetic equation to describe the local polarization reversal is derived from the Kolmogorov-Avrami-Ishibashi equation for 180° switching. Using the finite element method the field values in the granular matrix are evaluated and then the kinetic equation is iteratively solved using the average field values inside the grains updated at each iteration step. Iteractions are repeated until the total saturation polarization is reached. Simulations are performed for a matrix containing 400 grains of random form and size (with average size of 1 µm) under applied field values 3 V/µm, 4 V/µm, and 5 V/µm. The obtained polarization-time curves, and polarization and electric field maps are presented. The case of 3 V/µm is exemplarily investigated in detail disclosing statistical polarization and electric field distributions and their spatial correlations. We found that the field distribution is continuously broadening during the poling of an anisotropic material. However, for isotropic permittivity the width of the field distribution is proportional to an absolute value of the polarization and thus changes non-monotonically. An analytical explanation of these effects is given in terms of the dielectric tensor and the bound charge distributions. We have also established that short-range correlations of polarization components and field components are present. However, no cross-correlations between the polarization and field components are observed.