XPS Study of Lead Vanadate Glasses

X-ray photoelectron spectroscopy (XPS) has been used to obtain the structural information from the Pb4f, V2p, and O 1s core level photoelectron peaks in glasses of general formula xPbO-(1-x)V2O5 where x=0.22 and 0.54.The Pb4f7/2 peaks was symmetrical for x=0.22glass and asymmetrical for 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 V2p3/2 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 V4+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 the oxygen in the configuration V-O-V, called bridging oxygens, and 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 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, Pb-O-Pb are of the bridging type and therefore contributions to O 1s score level spectrum from these three configurations for the x=0.54 glass composition are undistinguishable. (author)