It was shown that absolute values of the time-dependent mean-square displacement of mobile ions in glasses could be deduced from a combined analysis of electrical conductivity and tracer diffusion data. By applying this method to sodium germanate glasses with various compositions, it was found that the distances through which the ions travelled at characteristic stages of the transport process increased considerably with decreasing Na2O content. At low Na2O contents, a linear relationship was observed between the transport distances and the interionic separation distances. This relationship disappeared at high Na2O contents. The same phenomena occurred in other alkali-ion conducting glassy systems. It was concluded that analysis of this effect was important for separating the influence of the network structure, upon the ion dynamics, from that of interionic Coulombic interactions.

Information on the Absolute Length Scales of Ion Transport Processes in Glasses from Electrical Conductivity and Tracer Diffusion Data. B.Roling, C.Martiny, K.Funke: Journal of Non-Crystalline Solids, 1999, 249[2-3], 201-9