Structural Analysis of Glassy Lead Borate Containing MoO3 In Relation to Its Optical Properties

Glasses with the base un-doped composition 80%PbO.20%B2O3 and
that containing MoO3 with 1% and 5% were studied using X-ray diffraction
(XRD) technique. The scattered X-ray intensity was Fourier transformed and
the Radial Distribution Function (RDF) analysis was applied to extract the
structural information's of these samples. The first nearest neighbor is observed
at 1.315Å, 1.456Å and 1.499Å respectively for the un-doped and doped
samples. This first nearest neighbor seems to be due to B-O correlations in the
form of triangles. The second nearest neighbor is centered at about 2.12Å for
the base sample and is shifted to 1.92Å for the doped ones; this peak is
attributed to O-O correlations having a coordination number of about two. The
B-B pairs were located at 2.36Å for the investigated samples with a reduced
coordination number, ~2.0. The coordinated Pb-O pairs were observed at
2.60Å with a form of PbO3 in the sample having 1% MoO3, and an appreciable
change in both Pb-O bond length and coordination number was noted in the
other two samples. The Pb-O pairs in the two samples(0.0 and 5% MoO3) were
stretched (at 2.80Å) and arranged in the tetrahedral form(PbO4). The peak
located at 3.55Å for the base sample and that contains 1% MoO3 is mainly due
B-O pairs arranged in BO4 and BO3 forms. In the third sample (having 5%
MO3) both of Non-Bridging Oxygen(NBO) and Bridging ones(BO) in the
connected B-O pairs are evolved; at 3.24Å and 3.64Å with an arranged BO3
form. The Pb-Pb metallic correlations were observed at ~4.0Å with a
coordination number about 4.0 for all samples. The structure of these glassy
networks was modeled and the different bond angles were concerned. The XRD
experimental findings were supported by IR, Raman and ESR measurements of
the studied samples.