Electrostrictive and dielectric properties of stretched poly(vinylidene fluoride-trifluoroethylene) copolymers at cryogenic temperatures

The electrostrictive property and dielectric behavior of the stretched poly (vinylidene fluoride-trifluoroethylene) copolymers, denoted as P(VDF-TrFE), have been studied at cryogenic temperatures. Polarization hysteresis loops and high electrostrictive performance (strain similar to1%) are obtained at room temperature. An obvious dielectric relaxation process is observed and the relaxation rate follows the Vogel-Fulcher relation with T-VF=160 K, U=0.18 eV, nu(0)=5.7x10(12) Hz. The dielectric relaxation behavior and high strain level decrease quickly with decreasing temperature, and below 160 K only a small strain level (similar to0.1%) and an "intrinsic" dielectric constant sustains. The correlation of dielectric behavior and strain activity and the physical mechanism of the quick suppression of the strain with decreasing temperature are briefly discussed. The results indicate that a high dielectric constant is critical for obtaining high electrostrictive strains in the polymers at a reasonable electric field. (C) 2003 American Institute of Physics.