Raman Spectra of Molybednum Phosphate Glasses and Some Crystalline Analogues

The Raman spectra of a series of glasses in the system MoO₃-P₂O₅ and the polyerystalline compounds molybdenum metaphosphate (MoO₂(P0₃)₂) and molybdenum pyrophosphate ((MoO₂)₂P₂O₂) are reported. The spectra indicate that traces of P=O and phosphate chains are present only in glasses having less than 50 mol% MoO₃. Comparison of the glass spectra with spectra of crystalline molybdenum phosphates indicates the presence of metaphosphate and orthophosphate structural groups of MoO₃ concentrations of about 50 mol% or less. As the MoO₃ concentration is increased, the bands characteristic of pyrophosphate groups appear in the spectra and become the dominant feature at 76 mol% MoO₃ concentration. Metaphosphate groups are present in the glass even at the highest MoO₃ concentrations measured.