Modeling on domain switching in ferroelectric ceramics near the morphotropic phase boundary

Abstract

In this paper, domain switching in ferroelectric ceramics near the morphotropic phase boundary (MPB), where tetragonal phase and rhombohedral phase coexist, is analyzed by a micromechanical model using an inverse-pole-figure (IPF) method. Charge screening effect in ferroelectric ceramics is taken into account, thus the depolarization field by polarization switching vanishes. The mechanical constraint caused by non-180° switching, however, cannot be neglected and is assumed to be proportional to the switching strain caused by non-180° domain switching with a factor β as the measure of the constrained level. Using the IPF method, the domain switching induced polarization and strain can be explicitly obtained via integrations over the unit spherical surface. Two limiting cases are studied in this paper, i.e., the energy barrier for the interphase non-180° domain switching is equal to or much larger than that for the in-phase non-180° switching. In the former case, it is found that domains always tend to switch to the rhombohedral phase especially when the constrained level is high, i.e., at a large value of β. If the mechanical constraint is neglected, i.e., β=0, the maximum achievable polarization and strain can be analytically obtained in this case. While in the latter case, interphase domain switching is suppressed, thus domain switching in MPB ceramics is only a superposition of independent in-phase domain switching in tetragonal ceramics and rhombohedral ceramics.