OBSERVATION OF 2 RELAXATION PROCESSES IN AN ION CONDUCTING GLASS YIELDS NEW STRUCTURAL INFORMATION

The frequency dependent ionic conductivity of the glass B2O3.0.56Li2O.0.45LiBr has been measured from 1 kHz up to 60 GHz, at temperatures up to 573 K. At first sight, the frequency spectra seem to conform with the so-called ''new universality'', i.e., with a sigma(omega) is-proportional-to omega1.0 power law at high frequencies/low temperatures. However, inspection of Arrhenius plots constructed at different frequencies clearly shows that two very well defined processes are superimposed, featuring different activation energies and different power-law exponents. The latter are 0.67 and 1.30, respectively, while a genuine power law with exponent 1.0 does not exist. The two processes are identified with translational jump diffusion (including jump relaxation) and a non-Debye localised reorientational motion of the ions within a given neighbourhood.