Modeling the dielectric response in relaxer ferroelectrics

A two-state thermodynamic model of ferroelectric materials exhibiting relax er properties is proposed. One state represents ferroelectric properties wi th a fenoelectric-paraelectric transition. The second one is relaxer-like, with vanishing macroscopic polarization and diffusive onset of local cluste r polarization. The model is able to reproduce qualitatively the dielectric susceptibility both for materials with phase transition into the ferroelec tric phase, and for ones remaining only incipient ferroelectric with high p ermittivity. Examples of dielectric responses have been calculated. They mo del the situations in pure relaxer, pure ferroelectric as well as in some m ixed cases.