Analysis of the alternating current properties of ionic conductors

Abstract

A method of analysis of inclined semicircular complex impedance (Z) diagrams for ionic conductors has been developed on the basis of the concept of “non-Debye” behaviour of solid dielectrics. This approach replaces the rather arbitrary distribution of relaxation times by the physically much simpler concept of a frequency-independent ratio of energy lost per cycle to energy stored. This criterion of dielectric behaviour leads directly to complex admittance (Y) plots in the form of straight lines inclined to the vertical which then transform to inclined semicircles in Z. The use of Y diagrams gives better accuracy of representation and it is shown how this can be further enhanced by plotting log Y _i − log Y _r instead of the usual linear representation. Different parts of the graphs are assigned to “bulk” and “barrier” regions on the basis of the value of the dielectric permittivity and it is shown that a hitherto unrecognized physical process can manifest itself as a strong dispersion at frequencies intermediate between the high-frequency bulk response and the low-frequency barrier-dominated behaviour.