Structural studies of lead aluminate glasses

Lead aluminate melts were quenched rapidly with a roller quencher and bulk glasses were formed over a composition range from 72.5 to 80.0 mol% PbO. Pulsed neutron diffraction, 27 Al MAS NMR and Raman spectroscopy were used to study the structure of a series of these glasses. The results show that in the glasses the aluminium is four coordinated by oxygen across the compositional range, with a bond length of about 1.76 angstrom The Pb-O peak in the neutron correlation function is asymmetric, and it can be modelled in terms of two bond lengths of similar to 2.25 angstrom and similar to 2.47 angstrom, with the majority of the coordination at the shorter distance. There is evidence that most or all of the lead ions are on asymmetric sites, coordinated by three oxygens in a trigonal pyramid arrangement. Both the neutron diffraction and Raman results indicate that the Pb-O bond lengths become shorter with increasing lead content. (c) 2007 Elsevier B.V. All rights reserved.