AC conductivity in dispersed ionic conductors: the effective medium approximation

We developed a stochastic transport theory for the calculation of the ac-conductivity in two-phase mixture materials (with high interface conductance). A perturbation around the different configurational interface paths is introduced by using the Effective Medium Approximation (EMA). Data of LiI conductivity after the addition of an insulating second phase Al2O3 show that our approach describes the main features of the ac-conductivity. The dielectric constant and the static effective capacitance, as a function of the concentration of the insulating material, are compared against previous Monte Carlo simulations and Renormalization Group results. Conductivity (Cole-Cole plots) and dielectric properties of dispersed ionic conductors are studied in a self-consistency way. A random walk in a random-resistor network and the use of an effective electric circuit are presented in order to describe all the features of the ac-response in these materials.