Title: Raman and X-ray Absorption Spectroscopy Studies of Chromium-Phosphorus Interactions in High-Bismuth High Level Waste Glasses

Mo-containing high-level nuclear waste borosilicate glasses were investigated as part of an effort to improve Mo loading while avoiding yellow phase crystallization. Previous work showed that additions of vanadium decrease yellow phase formation and increases Mo solubility. X-ray absorption spectroscopy (XAS) and Raman spectroscopy were used to characterize Mo environments in HLW borosilicate glasses and to investigate possible structural relationships between Mo and V. Mo XAS spectra for the glasses indicate isolated tetrahedral Mo6+O4 with Mo-O distances near 1.75 Å. V XANES indicate tetrahedral V5+O4 as the dominant species. Raman spectra show composition dependent trends, where Mo-O symmetrical stretch modemore » frequencies (ν1) are sensitive to the mix of alkali and alkaline earth cations, decreasing by up to 10 cm-1 for glasses that change from Li+ to Na+ as the dominant network-modifying species. This indicates that MoO4 tetrahedra are isolated from the borosilicate network and are surrounded, at least partly, by Na+ and Li+. Secondary ν1 frequency effects, with changes up to 7 cm-1, were also observed with increasing V2O5 and MoO3 content. These secondary trends may indicate MoO4-MoO4 and MoO4-VO4 clustering, suggesting that V additions may stabilize Mo in the matrix with respect to yellow phase formation.« less

Transparent glasses were synthesized in the NaPO{sub 3}-BaF{sub 2}-WO{sub 3} ternary system and several structural characterizations were performed by X-ray absorption spectroscopy (XANES) at the tungsten L{sub I} and L{sub III} absorption edges and by Raman spectroscopy. Special attention was paid to the coordination state of tungsten atoms in the vitreous network. XANES investigations showed that tungsten atoms are only six-fold coordinated (octahedra WO{sub 6}) and that these glasses are free of tungstate tetrahedra (WO{sub 4}). In addition, Raman spectroscopy allowed to identify a break in the linear phosphate chains as the amount of WO{sub 3} increases and the formationmore » of P-O-W bonds in the vitreous network indicating the modifier behavior of WO{sub 6} octahedra in the glass network. Based on XANES data, we suggested a new attribution of several Raman absorption bands which allowed to identify the presence of W-O{sup -} and W=O terminal bonds and a progressive apparition of W-O-W bridging bonds for the most WO{sub 3} concentrated samples (30% molar) due to the formation of WO{sub 6} clusters.« less

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