Leakage current and relaxation characteristics of electron-irradiated poly(vinylidene fluoride-trifluoroethylene) copolymers

Leakage current of direct current (DC) conduction for high-energy electron-irradiated poly(vinylidene fluoride-trifluoroethylene) 56/44 and 80/20 mol% copolymers have been studied at room temperature under various electric fields. It is found that the leakage current is strongly dependent of time and that the trapping limit of space-charge changes with the transition from a normal ferroelectric to a relaxor ferroelectric. It is suggested that the leakage current at low electric field is mainly due to the effect of space-charge trapping during the poling process in addition to contribution from dipoles. The copolymers become typical relaxor ferroelectrics after irradiation, which obeys the Vogel-Fulcher (V-F) law, indicating that the ferroelectric relaxation is also responsible for the limit of space-charge trapping in the electron-irradiated copolymer electrets. (C) 2003 Elsevier B.V. All rights reserved.