Modeling the dielectric response in relaxor ferroelectrics

A two-state thermodynamic model of ferroelectric materials exhibiting relaxor properties is proposed. One state represents ferroelectric properties with a ferroelectric-paraelectric transition. The second one is relaxor-like, with vanishing macroscopic polarization and diffusive onset of local cluster polarization. The model is able to reproduce qualitatively the dielectric susceptibility both for materials with phase transition into the ferroelectric phase, and for ones remaining only incipient ferroelectric with high permittivity. Examples of dielectric responses have been calculated. They model the situations in pure relaxor, pure ferroelectric as well as in some mixed cases.