What do electrical conductivity and electrical modulus spectra tell us about the mechanisms of ion transport processes in melts, glasses, and crystals?

Abstract

The significance of electrical conductivity and electrical modulus spectra with respect to ion transport mechanisms in melts, glasses, and crystals is discussed. It is shown that in the typical frequency range of an ac impedance experiment, the real part of the conductivity, σ′, is exclusively determined by the ion transport dynamics, while the imaginary part of the modulus, M″, is additionally influenced by vibrational and electronic polarisations. Accordingly, conclusions from the shape of M″ spectra about ion transport mechanisms cannot be drawn without properly taking into account the influence of these polarisations. Generally, it can be argued that analyses in terms of conductivity or dielectric spectra are preferable to analyses in terms of modulus or resistivity spectra if the electrical properties of a sample can be represented by resistances acting in parallel.