Study of structural aspects of PbO–P2O5–Sb2O3 glasses

Abstract PbO–P2O5 glasses in which part of the PbO or P2O5 has been replaced by Sb2O3 were prepared by conventional melt-quench method and characterised by powder X-ray diffraction (XRD), infrared, X-ray photoelectron spectroscopy (XPS), 31P magic angle spinning nuclear magnetic resonance, differential scanning calorimetry (DSC) and uv-visible optical absorption studies. (PbO)1−x(P2O5)x glasses contain mainly two types of Q2 structural units of phosphorus, which are ionically and covalently bonded to Pb2+. XPS studies of the glasses, where part of the PbO or P2O5 has been replaced by Sb2O3, revealed the existence of both Sb3+ and Sb5+ in these glasses. 31P MAS NMR studies of Sb2O3-substituted glasses suggested the formation of two types of additional Q2 structural units of phosphorus which have Sb3+ and Sb5+ as next nearest neighbours in the network, thereby giving rise to different values of chemical shift. Sb2O3-containing glasses were found to be thermally more stable compared to PbO–P2O5 glasses as revealed by the formation of crystalline Pb(PO2)2 phase at higher temperatures. Eopt values were found to decrease for the partial replacement of PbO or P2O5 by Sb2O3 in (PbO)0.4(P2O5)0.6 base glass.