Ion dynamics in glass-forming systems: I. Conductivity spectra below the glass transformation temperature

Complete conductivity spectra of a lithium ion-conducting glass of composition B2O3-0·56Li2O-0·45LiBr have been taken at twelve temperatures, covering the frequency range from a few hertz to about 50THz. For the first time, a separation of the hopping and vibrational contributions to the spectra has been performed. The resulting frequency-dependent hopping conductivity displays a high-frequency plateau similar to those known to exist in crystalline solid electrolytes such as RbAg4I5 and Na-β-alumina. In its dispersive regime, the hopping conductivity is empirically decomposed into Jonscher and non-Jonscher contributions of different activation energies. Apart from the ‘new universality’ component, which is still unexplained, the other constituents are interpreted in terms of translational and localized hopping processes.