COMPLETE CONDUCTIVITY SPECTRA OF FAST-ION CONDUCTING SILVER-IODIDE SILVER SELENATE GLASSES

We present complete dynamic conductivity spectra of the fast-ion condu cting glass 0.48(AgI)(2) . 0.52Ag(2)SeO(4). The spectra were recorded at frequencies between 4 Hz and 10 THz and at temperatures between 93 K and 573 K. This temperature range covers the glassy and molten state of matter. In the spectra, we can clearly distinguish between the hop ping conductivity at low frequencies, and the vibrational regime at ve ry high frequencies. We remove the vibrational contribution and obtain spectra which are then entirely interpreted in terms of the hopping m otion of the silver ions ('complete hopping spectra'). To describe the se complete hopping spectra a superposition of two power laws is neede d. One of them is the 'Jonscher power law' with an exponent 0.62, whil e the additional power law has an exponent larger than one. Both power -law components are thermally activated. The low-frequency hopping con ductivities of 0.48(AgI)(2) . 0.52 Ag2SeO4 are consistent with the 'ma ster curve', recently obtained by Roling et al. The interpretation of our hopping spectra includes the idea of different 'target sites for t he mobile silver ions as described in the unified site relaxation mode l as well as the existence of 'Coulombic traps' which is an essential feature of the counter-ion model.