Investigation of the dielectric relaxation, conductivity and energy storage properties for biaxially oriented poly(vinylidene fluoride-hexafluoropropylene)/poly(methyl methacrylate) composite films by dielectric relaxation spectroscopy

摘要

The dielectric relaxations in biaxially oriented P(VDF-HFP)/PMMA composite films with less than 40 % PMMA were investigated using dielectric relaxation spectroscopy. Various relaxation processes and their locations of P(VDF-HFP), PMMA, and P(VDF-HFP)/PMMA composite films were analyzed. According to the fitted data of the Havriliak-Negami (HN) function, different relaxation processes belong to non-debye relaxation, the activation energy (E_a) and dielectric relaxation strength (Δ_ε) of P(VDF-HFP)/ PMMA composite films significantly decreased around and above glass transition temperature (T_g) with increasing PMMA content. In addition, the conductivities (σ) of P(VDF-HFP)/PMMA composite films also sharply decreased with the addition of PMMA. The decrease of dielectric relaxation strength (Δ_ε) benefits the drop of P_r, lower the activation energy (E_a) makes coercive field decrease and the lower conductivity (σ) could enhances the breakdown strength. Thus, dielectric film of high energy storage density and low loss was closely related with the lower E_a, Δ_ε and σ.