ELECTRICALLY INDUCED FERROELECTRIC PHASE-TRANSITION OF COPOLYMERS OF VINYLIDENE FLUORIDE AND TRIFLUOROETHYLENE

The ferroelectric phase transition of copolymers of vinylidene fluoride and trifluoroethylene was studied by means of measurements of dielectric constants under a bias electric field. Phase transition temperatures for unpoled samples initially shifted to lower temperatures with the bias field in the region of the small electric field, but to higher temperatures under large bias field. Thermodynamical analysis of the phase transition in poled samples in terms of Clausius-Clapeyron and Ehrenfest equations determined the thermodynamical order of the phase transition.