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

The polarization reversal in perovskite ferroelectrics having a tetragonal phase is studied using the Landau-theory-based lattice model. extended to t he three-dimensional polarization case. Switching at various electric field levels is analyzed for near and far distances from the theoretical morphot ropic phase boundary (MPB), in the presence of the latent nuclei. The calcu lated time dependence of average polarization during switching is correlate d with the changes of polarization profiles in the lattice. For low electri c fields. switching can be achieved by polarization vector rotations trigge red by infinitesimal tilting at the latent nuclei sites. Polarization vecto r rotations are most significant close to the MPB, where the free energy is isotropic in the space spanned by the polarization components. For electri c fields beyond the longitudinal polarization instability, the transversal polarization components do not play a very significant role. Inferior reten tion properties near the MPB due to the polarization vector rotations are p redicted. though higher reversal speed and lower switching threshold are ex pected.