INVESTIGATION BY RAMAN-SCATTERING OF THE [TEO2-RMO0.5] (M=AG OR TL) GLASSES AND OF THE RELATED IONIC CONDUCTORS [TEO2-RMO0.5](1-X)[AGI]X

The structure of binary glasses [TeO2-RMO0.5], with M = Tl (or Ag) and 0.22 less-than-or-equal-to R less-than-or-equal-to 1 (0.28 less-than-or-equal-to R less-than-or-equal-to 1) has been investigated by Raman scattering under VV and VH polarizations. The two systems behave in nearly the same way: in the tellurite-rich part, the structure is built up of [TeO4] trigonal pyramids, a disordered form of the paratellurite alpha-TeO2. With increasing R between 0.40 (0.35) and 1 (the upper R value limiting the vitreous domain in each system), an increasing proportion of tri-coordinated tellurium [TeO3] is formed in the glasses. The ternary [TeO2-RMO0.5](1-x)[AgI]x glasses have been reported as ionic conductors. The structure of the tellurite network is not modified by the addition of silver iodide. A band appearing in the low-energy part of the Raman spectra is assigned to vibrations of [AgI4] species.