Crystalline phase transition in the copolymer of vinylidenefluoride and trifluoroethylene

Abstract

The measurement of the temperature dependence of elastic, dielectric, and piezoelectric constants for the film of 55/45% VDF-TrFE copolymer suggests that the Curie temperature exists at about 70 °C. The lattice spacing sharply changes at a temperature range from 55 to 75 °C. The remanent polarization is also determined from the D versus E hysteresis loop below 75 °C. It is found that the spontaneous strain in crystal lattice is linearly related to the square of remanent polarization. The transition is ascribed to electrostriction due to dipolar orientation.