Mixed cation effect in chalcogenide glasses Rb2S-Ag2S-GeS2 -: art. no. 184204

Chalcogenide glasses with composition 0.5[(1-x)Rb2S-xAg(2)S]-0.5GeS(2), 0 less than or equal tox less than or equal to1, were prepared and their ion transport properties and glass transition temperatures were found to show clear manifestations of the mixed cation effect. These Rb-Ag thiogermanate glasses were shown to be homogeneous in the mesoscopic domain by small-angle x-ray scattering. Extended x-ray-absorption fine structure indicated that each mobile cation forms its own specific environment that is not influenced by the presence of the dissimilar cation. On the other hand, Raman and infrared spectra showed nonlinear structural changes of the glassy matrix upon cation mixing. The maximum deviation from structural additivity was observed for compositions giving the extreme values for conductivity and T-g, and was found to result from cation-triggered rearrangements of the local germanate polyhedra toward a more homogeneous glass structure. These results support the recently proposed CIRON model that focuses on cation-induced relaxations of the network in mixed cation glasses.