Quantification of phosphorus structures in CaO–SiO2–P2O5 glasses via Raman spectroscopy

Abstract The phosphorus structures in CaO–SiO2–P2O5 glasses were analyzed by Raman spectroscopy and integral Raman intensities of [PO4]-tetrahedrons were calibrated by 31P MAS-NMR spectroscopy. Spectral results showed the presence of Q0(P) and Q1(P), and calculated values of Raman scattering coefficients of Q0(P), Q1(P) units were 1 and 0.576, respectively. Good agreement between experimental and theoretical values of non-bridging oxygen number per coordinated atom indicated the reliability of evaluating Raman scattering coefficients of Qn(P). Quantitative Raman analysis indicated that CaO exerted stronger ability to depolymerize [PO4]-tetrahedrons rather than [SiO4]-tetrahedrons with increasing basicity under the condition of higher degree of polymerization. P2O5 added to silicate melt could cause an increase in amount of Q2(Si), Q3(Si) and Q4(Si) units due to stronger stability of P–O–Ca linkages than that of Si–O–Ca linkages. Moreover, P5+ ions could be partly replaced with Si4+, forming Q1(Si+P) and Q2(Si+P) units.