Conductivity relaxation was measured in these ionic conductors by using the admittance spectroscopic technique. A study of the frequency dependence of the dielectric modulus showed that Havriliak-Negami dielectric functions accurately described the relaxation process. This permitted the use of an analytical distribution of relaxation times in order to deduce the time decay function from admittance data in the frequency domain. Conductivity relaxation of the ionic conductors was analyzed by using this method, and revealed a marked non-Debye frequency behavior and stretched-exponential Kohlrausch-Williams-Watts time decay functions. The results were explained in terms of cooperative effects or correlations among ions.

C.León, M.L.Lucía, J.Santamaría: Philosophical Magazine B, 1997, 75[5], 629-38