Effect of electron irradiation on electroactive phase and dielectric properties of PVDF films

Abstract

The effect of electron irradiation on the crystal structure and dielectric properties of poly(vinylidene fluoride) (PVDF) films was investigated. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were employed to examine the degree of participation in PVDF and the relative fraction of electroactive phase as well as the thermal property of PVDF films. The results showed that both the exothermal peak temperature and the crystallinity of the irradiated film decreased with increasing doses. Huge damage on the morphology of spherulite was observed in irradiated films by atomic force microscopy (AFM). The results of fine structures in PVDF films characterized by X-ray absorption near edge structure (XANES) implied that the dominance of the oxidation reaction occurred during irradiation, and further induced destruction of the regular packed structure. The results indicate that the β-phase exhibits good anti-irradiation ability during the electron irradiation on PVDF film. Because a large portion of the electroactive phase is maintained and intermediate phases are produced in the irradiated PVDF sample, the irradiated film exhibits a relatively high dielectric constant (around 7.8 under 2200 kGy) with low loss.