X-ray absorption and Raman characterizations of TeO2-Ga2O3 glasses

The thermodynamic properties of transparent glasses prepared in the TeO2-Ga2O3 system were investigated by differential scanning calorimetry. The change of the thermal parameters as a function of the chemical composition is discussed. Raman and both Te L-III and Ga K edge X-ray absorption spectroscopies at room temperature were used to examine the short range order. Analyses of the spectra suggest that the addition of Ga2O3 content to the TeO2 glass matrix induces the transformation of trigonal bipyramids (TeO4E, E = lone electronic pair 5s(2) of Te) to trigonal pyramids (TeO3E) with formation of Te-O-Ga bridging bonds. Furthermore, Ga K edge XANES and EXAFS studies show that Ga atoms exhibit both tetrahedral (GaO4) and octahedral (GaO6) environments. (C) 2003 Elsevier B.V. All rights reserved.