Tracer Diffusion and Electrical Conductivity in Sodium-Rubidium Silicon Sulfide Glasses

The tracer diffusion coefficients of 22Na and 86Rb and electrical conductivity were measured in a series of 0.56(Na, Rb)2S.0.44SiS2 glasses as a function of the Rb/Na ratio and temperature. The data were used to calculate the Haven ratio as a function of the Rb/Na ratio. The Haven ratio at 149.6°C increases from ∼0.3 in single‐alkali glasses to ∼0.80 for intermediate compositions. The results are consistent with a single jump mechanism involving jumps of alkali ions between unoccupied sites. The observed correlation effects arise through interactions between alkali ions and charge‐compensating centers in the glass network. The charge‐compensating centers are thought to correspond to non‐bridging oxygen ions in some oxide glasses and to nonbridging sulfur ions in sodium‐rubidium silicon sulfide glasses.