The dielectric properties of these ionic glasses (figure 5) were investigated at low frequencies (10Hz to 10MHz) by performing complex impedance measurements at temperatures ranging from 20 to 330K. Microwave frequencies (8.2 to 18GHz) were also used at temperatures ranging from 77 to 300K. An analysis which was based upon a jump relaxation model showed that translational and reorientational hopping motions of the mobile Ag+ ions were responsible for the observed frequency-dependent alternating-current conductivity. The temperature dependence of the latter conductivity at a given frequency could be fitted by using 3 relaxation processes which had characteristic activation energies that differed from each other by an order of magnitude and were very similar to those which had been deduced from previous ultrasonic attenuation studies of the same glasses. The highest energy of about 0.4eV was associated with the translational hopping motion which was responsible for long-range ionic diffusion through the glasses in the low-frequency limit. The lowest activation energy of about 0.01eV was attributed to a topological disorder that was characteristic of glassy materials, and probably corresponded to ion hopping between almost energetically equivalent available sites. The intermediate energy values of 0.05 to 0.1eV, which depended upon the modifier concentration, were suggested to characterize various reorientational motions and/or various jump lengths.

M.Cutroni, A.Mandanici, A.Piccolo, C.Fanggao, G.A.Saunders, P.Mustarelli: Philosophical Magazine B, 1996, 73[2], 349-65