DIFFUSE PHASE-TRANSITION IN FERROELECTRIC POLYMERS

The first order ferroelectric-paraelectric transitions in ferroelectric polymers are discussed in the framework of the Diffuse Phase Transition models. In order to describe these transitions, we use the classical Landau-Devonshire treatment for the sample micro-regions undergoing normal phase transition and look for a critical temperature distribution function. Thus, this model is applied to study the phase transition of a vinylidene fluoride-trifluoroethylene copolymer. We show how to obtain the correct behaviour of the spontaneous polarization and of the dielectric constant besides the Landau expansion parameters.