On the structure of phosphosilicate glasses

Vibrational spectra of phosphosilicate glasses with P2O5 concentrations up to 15 mol% are investigated by the methods of Raman spectroscopy and quantum-chemical modeling. We have found that the Raman band at 1320 cm(-1) characteristic for such glasses is not simple and may be decomposed into two components with frequencies at approximate to 1317 and approximate to 1330 cm(-1) caused in our opinion by single phosphorus centers (O=PO3 tetrahedra surrounded by SiO4 ones) and by double phosphorus centers (pairs Of O=PO3 tetrahedra bonded by a common oxygen atom). In the investigated phosphosilicate glasses manufactured by MCVD and SPCVD methods the ratio of concentrations of single and double centers varies from 1:5 to 1:2. A novel interpretation of the Raman bands distinct from the traditional one is suggested. The approach to the Raman spectra analysis developed in this article can be applied for control and optimization of manufacturing process of phosphosilicate and similar glasses as well as optical fibers.