The modifier/former role of MoO3 in some calcium-phosphate glasses

Highlights: ► A new calcium-phosphate glass system with high molybdenum content was prepared. ► The EPR spectra for different MoO3 concentrations were recorded and discussed. ► The characteristic bands of these glasses were analyzed by Raman spectroscopy. ► By both techniques the role of network former/modifier of MoO3 was discussed. -- Abstract: This paper report the results obtained by EPR and Raman investigations of xMoO3⋅(100 − x)[P2O5⋅CaO] with 0 ⩽ x ⩽ 50 mol% glass system. From EPR spectroscopy were evidenced the local symmetry and the interaction between Mo5+ ions. Depending on the content of MoO3 were highlighted the EPR spectra modifications. By Raman spectroscopy were identified and analyzed the modification which appear on the characteristic bands of these glasses. At low concentration of molybdenum oxide the specific Raman bands of long phosphate chains (Q2) dominate the spectra meanwhile for high molybdenum content the most intense bands are those specific to MoO3 and short phosphate groups. From both techniques we can conclude that at low concentration of molybdenum oxide, it acts as a very strong network modifier while for high concentrations it plays the role of network co-former