Effect of electron beam irradiation on polymer electrolytes: Change in morphology, crystallinity, dielectric constant and AC conductivity with dose

• 8 MeV EB irradiation effect on dielectric constant and AC conductivity of polymer electrolyte films was observed.
• Occurrence of chain scission due to breaking of bonds was confirmed by FT-IR analysis.
• AC conductivity increases with dose due to more number of free charges involved in conduction.

Polymer electrolyte (PEO:Li2SO4) films were exposed to 8 MeV electron beam (EB) with various doses to investigate the radiation effect on dielectric permittivity (real and imaginary) and AC conductivity by using PC based Impedance Analyzer in the frequency range of 40–1 MHz at different temperatures. The change in chemical interaction, morphology, and thermal properties was analyzed with the help of Fourier Transform InfraRed (FT-IR), Scanning Electron Micrographs (SEM) and Differential Scanning Calorimeter (DSC) techniques respectively for before and after irradiation. The chemical change was confirmed from the FT-IR result which showed that peak intensities corresponding to C–H, C=C, and –C–O–C– bonds decrease with increase in EB dose clearly indicating that the degradation of polymer chain or segments (i.e., –CH2–CH2–). The DSC result showed that the melting temperature of unirradiated film is 69.42 °C which reduced to 67.55 °C for 30 kGy dose suggesting an exothermic behaviour. The SEM images give that surface roughness and crack depths increase with increasing dose. The XRD result reveals a decreased ~30% crystallite size for 30 kGy dose compared with unirradiated film. Further, it is seen that dielectric permittivity and frequency dependent conductivity were found to increase with increasing irradiation dose. The maximum AC conductivity was observed to be 1.88×10−4 s/cm for 30 kGy and the estimated change in charge carrier concentration also showed high for 30 kGy dose. The AC conductivity obeys Power׳s law. The frequency exponent (s) parameter shows temperature dependent behaviour which decreases after irradiation.