XPS study of lead vanadate glasses

X-ray photoelectron spectroscopy (XPS) has been used to obtain structural information from the Pb 4f, V 2p, and O Is core level photoelectron peaks in glasses of general formula xPbO-(1-x)V₂O₅ where x = 0.22 and 0.54. The Pb 4f_7/2 peaks was symmetrical for the x = 0.22 glass and asymmetrical for the x = 0.54 glass and was therefore fitted with two contributions, one from Pb atoms forming PbO₃ trigonal pyramids, and the other from Pb atoms forming PbO₄ square pyramids. The V 2p _3/2 peaks were also asymmetrical and fitted with two contributions, one from V⁴⁺ ions and the other from V⁵⁺ ions. The concentration of V⁵⁺ was high in the x = 0.22 glass and no V ⁴⁺ ions were detected in the glass with x = 0.54. The O 1s spectra show asymmetry for the samples having the composition x = 0.22. For this glass composition, the O 1s peak was fitted with two contributions, one from oxygens in the configuration V-O-V, called bridging oxygens, and the other from oxygens in the configurations V-O-Pb and Pb-O-Pb, called non-bridging oxygens. For x = 0.54, the O 1s spectrum was symmetric and was fitted to a single peak. This is explained by the fact that the polarization of Pb atoms grows with the increase in PbO content in the glass and the Pb-O bond becomes covalent at x = 0.54. The oxygen atoms in the three configurations, V-O-V, V-O-Pb, and Pb-O-Pb are of the bridging type and therefore the contributions to the O 1s core level spectrum from these three configurations for the x = 0.54 glass composition are undistinguishable.