Molybdenum modified phosphate glasses studied by 31P MAS NMR and Raman spectroscopy

•Glasses from the P2O5SiO2K2OCaOMgOMoO3 system were analysed.•The modifier role of MoO3 was confirmed via 31P MAS NMR and Raman spectroscopy.•The introduction of MoO3 results in depolymerisation of the phosphate framework.•It was shown that molybdate units can form [MoO4/MoO6]OP or [MoO4/MoO6]OSi bonds.•The molybdate units can form bonds with NBOs atoms of Q2 methaphosphate units.

Glasses have been synthesized in the system P2O5SiO2K2OMgOCaO modified by addition of MoO3. Glasses were prepared by conventional fusion method from 40 g batches. The influence of Mo-cations on the analysed glass structure was investigated by means of Raman and 31P MAS-NMR techniques. It has been found that molybdate units can form Mo[MoO4/MoO6]OP and/or Mo[MoO4/MoO6]OSi bonds with non-bridging oxygens atoms of Q2 methaphosphate units, resulting in the transformation of chain methaphosphate structure into pyrophosphate and finally into orthophosphate structure. It has been also found that increasing amount of MoO3 in the structure of investigated glasses causes their gradual depolymerization and molybdenum ions in the analysed glass matrix act as modifying cations.

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