Analysis of Switching in Perovskite Ferroelectrics on the Tetragonal Side of the Morphotropic Phase Boundary Using a Landau-Theory-Based Lattice Model with Polarization Vector Rotations

Abstract

The polarization reversal in perovskite ferroelectrics having a tetragonal phase is studied using the Landau-theory-based lattice model, extended to the three-dimensional polarization case. Switching at various electric field levels is analyzed for near and far distances from the theoretical morphotropic phase boundary (MPB), in the presence of the latent nuclei. The calculated time dependence of average polarization during switching is correlated with the changes of polarization profiles in the lattice. For low electric fields, switching can be achieved by polarization vector rotations triggered by infinitesimal tilting at the latent nuclei sites. Polarization vector rotations are most significant close to the MPB, where the free energy is isotropic in the space spanned by the polarization components. For electric fields beyond the longitudinal polarization instability, the transversal polarization components do not play a very significant role. Inferior retention properties near the MPB due to the polarization vector rotations are predicted, though higher reversal speed and lower switching threshold are expected.