A simple model to reproduce the strong enhancement of the dielectric response near the morphotropic phase boundary (MPB) is proposed. This model consists of a long-range dipole-dipole interaction and compositional chemical disorder incorporated by the variation in lengths of dipole moments. By applying a Monte Carlo simulation, we show that a ferroelectric boundary phase appears between an antiferroelectric phase and a relaxor ferroelectric phase at an optimal strength of randomness. In the boundary phase, the ferroelectric domain becomes extremely large and flexible to external electric fields, leading to a huge dielectric response. This observation indicates that the huge dielectric response near the MPB originates from local polarization rotation under the suppression of anisotropy by phase competition.
ASJC Scopus subject areas