X-ray diffraction analysis on the structure of the glasses in the system PbOSiO 2

Abstract

The structures of PbO·SiO 2 and 2PbO·SiO 2 glasses have been analyzed by use of X-ray diffraction data and pair function method. For PbO·SiO 2 glass, a model consisting of chains of PbO 3 pyramids and silicate chains showed good agreement with the observed RDF. For 2PbO·SiO 2 glass, the present authors reported previously a model in which chains of PbO 3 pyramids are connected with SiO 4 tetrahedra, while the chromatographic analyses of silicate anions by Götz et al. and Smart et al. showed that silicate anions are distributed from monomer to polymer in the glass. We reexamined the structure of this glass referring to these results. Three representative models containing isolated SiO 4, Si 4O 12 rings and (SiO 3) n chains respectively as well as PbO 3 chains were constructed and the RDFs were calculated with changing structure parameters. These three models showed satisfactory agreement with the observed data, showing that silicate anions are distributed from monomer to polymer in 2PbO·SiO 2 glass and an increase of SiO 2 content leads to polymerization of silicate anions to longer chains up to PbO·SiO 2 composition, while the chains of PbO 3 pyramids remain unchanged.