Ionic conductivity and relaxation dynamics in fast ion conducting silver borate glasses

Abstract

Dynamics of Ag⁺ ions in AgI-Ag₂O-B₂O₃ glasses has been studied in the frequency range 10 Hz to 2 MHz and in the temperature range from 323 K to 93 K. The frequency dependent electrical data have been analyzed in the framework of conductivity and modulus formalisms. Both of these formalisms have provided for qualitative similarities in the compositional variation of the relaxation times and the dc conductivity. The results were compared with specific assumptions in the various structureal models of the glasses. We have obtained the mobile ion concentration and the power law exponent from the analysis of the conductivity spectra. We have observed that the concentration of Ag⁺ ions is independent of temperature and the conductivity is primarily determined by the mobility. A fraction of the Ag⁺ ions in the glass is involved in the dynamic process. We have also shown that the power law exponent is independent of temperature and demonstrated the existence of three dimensional conduction pathways of the glasses. The results are also supported by the temperature and composition independence of the scaling of the conductivity spectra. The stretched exponential parameter β remains almost invariant with temperature and composition and its small value for all the compositions signify that, the conductivity relaxation is highly non-exponential. Conductivity relaxation in these glasses was observed to be independent of temperature as that of conductivity spectra.