ION DYNAMICS IN GLASS-FORMING SYSTEMS .1. CONDUCTIVITY SPECTRA BELOW THE GLASS TRANSFORMATION TEMPERATURE

Complete conductivity spectra of a lithium ion-conducting glass of com position B2O3-0.56Li(2)O-0.45LiBr have been taken at twelve temperatur es, covering the frequency range from a few hertz to about 50 THz. For the first time, a separation of the hopping and vibrational contribut ions to the spectra has been performed. The resulting frequency-depend ent hopping conductivity displays a high-frequency plateau similar to those known to exist in crystalline solid electrolytes such as RbAg4I5 and Na-beta-alumina. In its dispersive regime, the hopping conductivi ty is empirically decomposed into Jonscher and non-Jonscher contributi ons of different activation energies. Apart from the 'new universality ' component, which is still unexplained, the other constituents are in terpreted in terms of translational and localized hopping processes.