Chemical model of binary molybdenum phosphate glasses

The influence of molybdenum on the actual chemical composition of phosphate glasses prepared in the range of the batch compositions from ultraphosphate to pyrophosphate was studied. An analysis of the glasses by XRF, ESR and 31P MAS NMR, supplemented by Raman spectroscopy, showed that the chemical composition of the ultraphosphate glass shifted significantly to the metaphosphate region of divalent cations, leading to very stable glass. The chemical composition of the remaining glasses also shifted towards a lower phosphorus content, i.e., to pyrophosphates, but their chemical composition remained in the area between metaphosphates and pyrophosphates of divalent cation. A chemical model was designed for all the glasses, the main glass-forming compounds were determined and the result was successfully confronted with the compositional dependences of both the glass transition temperature and the coefficient of thermal expansion.