In the literature, the electric modulus representation has been used to provide comparative analysis of the ion transport properties in different ion-conducting materials. In this paper we show that the modulus representation is not a suitable tool for such purposes. Our arguments derive from an examination of the scaling properties of both the ac conductivity ${\sigma }^{*}\left(\nu \right)$ and the modulus $M^{*}\left(\nu \right)$ which demonstrates how scaling that is inherent in ${\sigma }^{*}\left(\nu \right)$ is lost in $M^{*}\left(\nu \right)$ by inclusion of the high frequency permittivity ${\varepsilon }^{\prime }\left(\infty \right),$ the latter quantity being unrelated to ion transport processes. Furthermore, we show how highly regarded shape changes of the modulus that occur with varying ion concentration are merely a manifestation of including ${\varepsilon }^{\prime }\left(\infty \right)$ in the definition of $M^{*}\left(\nu \right).\mathrm{}$ We conclude then that the electric modulus formalism has resulted in misleading interpretations of the ion dynamics and, hence, should be discouraged.

• Received 21 August 2000

DOI:https://doi.org/10.1103/PhysRevB.63.024301