THE DIFFUSE BEHAVIOR OF THE FERROELECTRIC TRANSITION IN POLY(VINYLIDENE FLUORIDE-TRIFLUOROETHYLENE) COPOLYMERS

The ferroelectric-to-paraelectric phase transition in poly (vinylidene fluoride-trifluoroethylene) copolymers has been investigated using calorimetric and dielectric technics. In these materials, as it is well known, the ferro- and paraelectric phases coexist at large temperature intervals, which produces a smearing of the physical anomalies within the transition region. Thus, in order to treat our data, we have used an extended Landau-Devonshire treatment, which has provided a quantitative analysis of the macroscopic behavior of the systems. In particular, the Landau expansion parameters, the sample crystallinities, the spontaneous polarizations, and the coercive electric fields have been estimated for the copolymers with 25, 30, and 40 mol % of trifluoroethylene. (C) 1994 John Wiley & Sons, Inc.