Simulations of constrained domain switching in ferroelectric ceramics based on an optimization model

An optimization-based computational model is proposed to study the constrained domain switching in polycrystalline ferroelectrics. Charge screening effect is taken into account thus the depolarization field induced by polarization switching vanishes. The stress field induced by non-180deg switching cannot be compensated and is considered in an Eshelby inclusion manner. Domain switching is realized by an optimization process to minimize the free energy of each grain using fractions of each domain as the optimization variables. This model does not impose any priori domain switching criterion, thus having the similar superiority as the phase field model. Besides the polarization and strain, the domain textures can also be calculated using this model. Simulation results show that very little 90deg domain switching can occur in tetragonal PZT ceramics, while in rhombohedral PZT ceramics, about half of non-180deg switching can be accomplished under moderate electric poling. The large difference in poling difficulties between the tetragonal and rhombohedral PZT ceramics is partial due to the crystal symmetry differences, and also due to the large difference in lattice deformation during P-F phase transitions.