The structure of tellurite glass: a combined NMR, neutron diffraction, andX-ray diffraction study

Models are presented of sodium tellurite glasses in the composition range ( Na2O)(x)-(TeO2)(1-x), 0.1 < x < 0.3. The models combine self-consistently d ata from three different and complementary sources: sodium-23 nuclear magne tic resonance (NMR), neutron diffraction, and X-ray diffraction. The models were generated using the Reverse Monte Carlo algorithm, modified to includ e NMR data in addition to diffraction data. The presence in the models of a ll five tellurite polyhedra consistent with the Te4+ oxidation state were f ound to be necessary to achieve agreement with the data. The distribution o f polyhedra among these types varied from a dominance of bridged species at lower sodium contents, to polyhedra with one or zero bridging oxygen at la rger sodium contents. The models indicate that the sodium cations themselve s form sodium oxide clusters particularly at the x = 0.2 composition. (C) 2 000 Elsevier Science B.V. All rights reserved.