Abstract
We have used high real-space resolution pulsed neutron diffraction to investigate the structure of six Tl2O-Bi2O3-Ga2O3 glass samples. The low Q behaviour of the diffraction patterns indicates that the intermediate range order increases when Tl2O is substituted for Bi2O3. The Ga-O, Bi-O and Tl-O distances are found to be 1.85, 2.10 and 2.43Angstroms respectively. Gallium is tetrahedrally coordinated by oxygen. The Tl-O coordination seems to be similar to that in crystalline Tl2O where thallium is coordinated by three oxygens. Bi-O also shows a relatively low coordination number. The paper discusses the detailed structure of these glasses, both with reference to the gallium-oxygen network and the coordination around the modifying cations. The methods of chemical crystallography are used to analyse the possible coordination polyhedra for Tl and Bi, to predict the likely oxygen environments in these glasses, and to generate a complete description of the connectivity of the three dimensional network.
