Electron-irradiation induced phase transition in poly (vinylidene fluoride-trifluoroethylene) copolymer

The electron-irradiation induced ferroelectric-to-relaxor phase transition in poly (vinylidene fluoride-trifluoraethylene) (P(VDF/TrFE)) copolymer was investigated One polymer with a composition of 53 mol% VF2 (PVDF53) and a Curie temperature of 67 degreesC, and another with 76 mol% VF2 (PVDF76) and a Curie temperature of 136 degreesC, were used in the research. Changes in hysteresis loop, permittivity and electrostriction during the phase transi tion were measured. X-ray diffraction showed that PVDF53 had a second-order phase transition during the irradiation in which the structure was changin g continuously, while PVDF76 had a first-order phase transition in which th e structure changed discontinuously. Field-induced piezoelectrics response was measured using a loudspeaker which provided a vibrational force, and d( 31) = 135 pC/N at bias E-3 = 40 MV/m was obtained. The conditions for elect ron irradiation and composition of the copolymers were discussed.