Electron Irradiation Effects in Electrostrictive P(VDF-TrFE) Copolymers

Electrical field-induced strain response of electron-irradiated Poly(viny1idene fluoride trifluoroethylene) copolymer has been studied by a Mach-Zehnder type Heterodyne interferometer in the frequency range of 3 to 9 kHz. The electrostrictive constant is calculated from the strain results, which is of the same order of magnitude as those obtained at 1 Hz by a bimorph-based strain sensor, but at much lower electrical field. Changes in the piezoelectric coefficient, dielectric property and phase transition behavior of the same copolymer have been studied. The structural changes in the irradiated films were probed by means of differential scanning calorimetry, X-ray diffraction and IR spectra. The reversible solid-state transition between the polar and non-polar phase in the crystalline regions of the copolymer dnven by the external electric field is suggested to be responsible for the significant high electrostrictive strain of the electron-irradiated copolymer.