It was noted that, compared with other mixed-cation glasses (with large deviations from additivity, a pronounced minimum in the conductivity isotherms, and a diffusivity cross-over when guest cations reduced the mobility of ions supplied by the host material), the CuI–AgI–As2Se3 glass system exhibited markedly different transport properties. Firstly, the ionic conductivity increased monotonically, by 4 orders of magnitude, from 3 x 10−8 to 5 x 10−4S/cm when CuI was gradually replaced by AgI; with no minimum at intermediate concentrations. Secondly, no diffusivity cross-over was observed. The 64Cu tracer diffusion coefficient, DCu, increased by a factor of 20 to 30 when Cu was replaced by Ag. The values of DCu were always lower than those of DAg. The exception was an 0.5CuI-0.5As2Se3 glass, where DAg and DCu were very similar. The results could be explained in terms of a degenerate mixed-cation effect, with different trends for Ag and Cu mobile cations.

Degenerate Mixed Cation Effect in CuI–AgI–As2Se3 Glasses - 64Cu and 110Ag Tracer Diffusion Studies. A.Bolotov, E.Bychkov, Y.Gavrilov, Y.Grushko, A.Pradel, M.Ribes, V.Tsegelnik, Y.Vlasov: Solid State Ionics, 1998, 113-115, 697-701