A NEW ANALYSIS OF THE BULK AC ELECTRICAL RESPONSE OF IONIC CONDUCTORS

Measurements of the bulk ac electrical response of the fluorine ion co nductor (1 - x)CdF(2)xErF(3), x = 0.15, are shown to be composed of se parable dipolar dielectric and hopping conductive components. The diel ectric component has a relaxation frequency of similar to 4 kHz and po wer law, Cole-Davidson frequency dependencies of real and imaginary pa rts. The conductive component is frequency independent up to similar t o 100 kHz and decreases in a Drude fashion at higher frequencies. Ion hopping, characterised by a narrow exponential distribution of activat ion energies, is shown to generate the measured electrical responses. A model is proposed in which the dielectric component is identified wi th ions associated with immobile counter-ion or defect clusters and th e conductive component with ions at lower activation energy sites betw een the clusters. It is found that a quantitative account of the condu ctivity can be obtained by assuming it to arise from a percolation fra ction of the ions. (C) 1998 Elsevier Science B.V. All rights reserved.