Raman spectroscopic studies of fluorophosphate glasses

Some fluorophosphate glasses obtained by fluorination of NaPO3, xNaPO3−yAlF3 or tNaPO3−wAlF3−vCaF2 have been studied by Raman spectroscopy in VV and VH polarisations. The observed bands have been assigned by comparison with those vitreous NaPO3 and Na4P2O7, as well as crystallised K2PO3F and KPO2F2, and molten cryolite. Structural models are proposed for the various compositions. They are built up with arrangements of following species: (PO3)2n−n chains; (P2O7)4− dimers, (AlF6)3− octahedra, P(O, F)4, (AlF4)− and (AlOF3)2− tetrahedral groups. For glasses rich in phosphate −OPO2F− and −OPOF2 terminal groups are displayed; the latter being favoured for a higher fluorine concentration.