X-ray absorption study of the short range order of tungsten and molybdenum ions in BaO-P₂O₅-WO₃ and CaO-P₂O₅-MoO₃ glasses

The analysis of XANES and EXAFS in BaO-P₂O₅-WO₃ and CaO-P₂O₅-MoO₃ glasses at the W L_1,3 and Mo K edges was performed in comparison with a number of crystalline WO₃, CaWO₄, Na_0.66WO₃, α-MoO₃, β-MoO₃ and amorphous a-WO₃, a-MoO₃ compounds. The results of the EXAFS modelling by two different methods ((1) multi-shell single-scattering model within harmonic approximation and (2) model-independent radial distribution function (RDF) approach) allowed us to extract detailed structural information on the first coordination shell of metal (W or Mo) ion. Using the obtained data together with the information given by other experimental techniques, we propose a structural model of the local environment distortion around tungsten and molybdenum ions in phosphate glasses.