Vinyl fluoride-trifluoroethylene copolymers were prepared by free-radical polymerization. The hysterisis loop of electrical displacement D versus electrical field E was obtained for 44 moi% vinyl fluoride copolymer. Values of the remanent polarization ranged from 20 to 50 mC m- 2. The temperature dependence of the dielectric constant indicated a dielectric anomaly with frequency dependence. The reciprocal dielectric constant was thus plotted in conformity with the Curie-Weiss law. The remanent polarization gradually decreased from room temperature and completely disappeared at about 100°C. A discontinuous change in the linear thermal expansion coefficient was observed at 100°C. It was found that this vinyl fluoride copolymer is ferroelectric at the Curie point. It was also found that the copolymer has a phase transition in relaxation that resembles second order.
Посилання на статтю:
Ferroelectric properties of vinyl fluoride-trifluoroethylene copolymers / Kazuhiko Maeda*, Shigeru Tasaka, Norihiro Inagaki and Tomohiko Kunugi // Polymer. – 1993. – Vol 34. – P. 3387-3390.