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 l ess than or equal tox less than or equal to1, were prepared and their ion t ransport properties and glass transition temperatures were found to show cl ear manifestations of the mixed cation effect. These Rb-Ag thiogermanate gl asses were shown to be homogeneous in the mesoscopic domain by small-angle x-ray scattering. Extended x-ray-absorption fine structure indicated that e ach mobile cation forms its own specific environment that is not influenced by the presence of the dissimilar cation. On the other hand, Raman and inf rared spectra showed nonlinear structural changes of the glassy matrix upon cation mixing. The maximum deviation from structural additivity was observ ed for compositions giving the extreme values for conductivity and T-g, and was found to result from cation-triggered rearrangements of the local germ anate polyhedra toward a more homogeneous glass structure. These results su pport the recently proposed CIRON model that focuses on cation-induced rela xations of the network in mixed cation glasses.