An evaluation of random R-C networks for modelling the bulk ac electrical response of ionic conductors

The ac electrical characteristics of a 2-D square randomly filled RC network are shown to exhibit many features in common with those of a typical ionic conductor. These include the 'universal' power law frequency responses of ac conductivity and permittivity, It is suggested that a random network of ion conduction channels and insulating islands may provide a realistic model of the conduction paths within a bulk ionic conductor. DC ionic conductivity is identified with a resistive percolation path through the network and the higher frequency power law component with that of the random network of ac conducting linked capacitive and conductive regions. The dielectric loss peak associated with ionic conductors is also found to be a random R-C network characteristic. The effect of the insulating islands having a Debye-like capacitance is modelled and ZrO2 12 mol% Y2O3 data are presented which exhibit the effects predicted. (C) 1999 Elsevier Science B.V. All rights reserved.