Migration in the Absence of Concentration Gradients

Under certain circumstances, the passage of electric current through an electrolyte does not lead to a concentration gradient, and Eq. (78) becomes 

The term is called the conductivity 7, and under these conditions Ohm s 

Apart from the most dilute solutions, however, we do expect interactions between unassociated defect species, and in general this will lead to a lieqnency-dependent conductivity. This has been recognized for many years by electrochanists (Onsager [1926,1927], Debye and Falkenhagen [1928]). The form of the fieqnency dependence, however, is of considerable interest. 

Following the work of Jonscher (see, for example, Jonscher [1977,1980]), who showed that a large number of different types of conductors exhibited a frequency dispersion of the CPE type, the presence of interactions has been invoked to explain the observed frequency dispersion in the conductivity of a number of solid electrolytes by Almond, West, and coworkers (Almond and West [1983a, b]), Almond et al. [1982, 1983, 1984]. These authors expressed the real part of the ionic conductivity of a number of materials by an expression of the type 

In general, both conductivity and dipolar relaxation processes may be present in the same material, and the total conductivity is given by 

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