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 ca lorimetric 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 quantit ative analysis of the macroscopic behavior of the systems. In particul ar, the Landau expansion parameters, the sample crystallinities, the s pontaneous polarizations, and the coercive electric fields have been e stimated for the copolymers with 25, 30, and 40 mol % of trifluoroethy lene. (C) 1994 John Wiley & Sons, Inc.