Detrapping behavior of trapped space charges in ferroelectric copolymers of vinylidene fluoride with trifluoroethylene

Three kinds of slowly-cooled ferroelectric VDF/TrFE copolymer samples with different VDF contents (56, 70, 77 mole%) were prepared by casting from methyl ethyl ketone solution and followed by cooling slowly from melting state to room temperature. The thermally stimulated depolarization current (TSDC) of the copolymer has been measured at various polarization temperatures (60-130°C). In the TSDC spectra, three peaks of detrapping charges for VDF(70)/TrFE(30) and VDF(77)/TrFE(23), two peaks for VDF(56)/TrFE(44) are observed. According to the peaks appeared at different cooling temperature during polarization and the analysis of phase transition, the structural origin of the TSDC peaks is proposed. The detrapping density of trapped charges shows that the ability of charge storage for VDF(70)/TrFE(30) is higher than that for other two copolymers