Glasses with Ag concentrations which ranged from 0.008 to 25at% were studied by using 110mAg tracers. It was found that the room-temperature conductivity of both systems increased by 9.0 to 9.5 orders of magnitude with increasing Ag content, while the activation energy decreased from about 1 to 0.4eV. Meanwhile, the Ag tracer diffusion coefficient at 298K increased by 5.0 to 5.5 orders of magnitude, with a similar decrease in the diffusion activation energy. A comparison of the conductivity and Ag diffusion data clearly showed that ionic transport predominated; even at the lowest Ag concentrations. The Haven ratio decreased with increasing Ag content. Extremely dilute glasses, with 0.008 to 0.1at%Ag, had a Haven ratio of unity. Vitreous Ag-rich alloys were characterized by Haven ratios of 0.2 to 0.4. The composition dependences of the ionic conductivity and Ag tracer diffusion coefficient exhibited very different transport regimes at low (less than 2 to 5at%Ag) and high (greater than 10at%Ag) concentrations. A power-law compositional dependence of the diffusivity and conductivity was observed at low Ag concentrations. This was true over 3.5 to 5.0 orders of magnitude of the ionic conductivity and over 2 to 3 orders of magnitude of the diffusion coefficient. This transport regime was attributed to percolation in the critical region just above the percolation threshold. Theoretically predicted dynamic and statistical effects upon percolative ionic conduction were in good agreement with the experimental observations. Following short-range and intermediate-range structural changes, at higher Ag contents (greater than 10at%), ionic transport no longer involved percolation. Instead, it became network-dependent with strongly correlated Ag+ motions.

E.Bychkov, V.Tsegelnik, J.Vlasov, A.Pradel, M.Ribes: Journal of Non-Crystalline Solids, 1996, 208[1-2], 1-20