Anomalies of dielectric properties of vinylidene fluoride-trifluoroethylene copolymer films

The temperature dependences of the real and imaginary parts of the complex permittivity of vinylidene fluoride-trifluoroethylene copolymer films at temperatures ranging from ?40 to 140°C are determined in the frequency range 10^?1–10⁸ Hz. An analysis of the experimental data has demonstrated that the behavior of the dielectric characteristics of the copolymer in the course of heating to temperatures above the ferroelectric phase transition point and during subsequent cooling differs substantially. In the latter case, the high-frequency dielectric response exhibits properties characteristic of relaxor ferroelectrics. The observed features are discussed in terms of the competition of two mechanisms associated with the short-range and long-range forces.