Ion and polaron conducting glasses

Conductivity spectra, sigma(omega), covering wide frequency ranges up to the mid infrared, have been taken of various glasses at different temperatures. The systems studied include the ion-conducting glasses 0.30 Na2O . 0.70 B2O3, 0.30 Li2O . 0.70 B2O3 and B2O3 . 0.56 Li2O . 0.45 LiBr as well as the polaron conducting glass 0.2 P2O5 . 0.8 (0.89 V2O5 . 0.11 V2O4). In the case of the ion-conducting glasses it is possible to separate vibrational and hopping spectra from each other. The resulting hopping spectra display high-frequency plateaus; in the dispersive regime, two power-law exponents are observed, one being smaller, the other larger than unity. In contrast, the dispersive conductivity of the polaron conducting glass shows a simple single-power-law behavior with an exponent smaller than one. The interpretation of the spectra includes the idea of different ''target'' sites for the mobile species. A model concept for ion and polaron transport in glasses is proposed.