Analyses for a dipolar relaxation in the featureless dielectric spectrum, and a comparison between the permittivity, modulus and impedance representations

Abstract

The apparently featureless permittivity, ε′, and loss, ε″, spectra of a nylon 12 polymer have been analysed to reveal its dipolar relaxation process and dc conductivity. Two other representations of the data, namely electric modulus and impedance, have been examined for their suitability in cases where overwhelmingly large contributions from electrode impedance and dc conductivity mask the dipolar relaxation process. In these two representations, the shape of the spectra of the relevant quantities could be fitted to a distribution of conductivity relaxation times, but when the parameters obtained from such fittings were used to calculate ε′ and ε″, large discrepancies between the calculated and measured quantities became obvious. Thus, modulus and impedance representations seem unsuitable for the analysis of the dielectric data. Critical examination demonstrated that unique and reliable information is obtained only when the dielectric data were analysed in permittivity representation and interfacial (electrode/sample) effects taken into account. The permittivity representation seems preferable to the other two representations.