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Te–O, Bi–O and Nb–O bond lengths, co-ordinations in bismuth tellurite, bismuth niobium tellurite glasses and Bi2Te4O11 anti-glass by HEXRD, RMC and Riteveld analysis.

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xLi2O–(100 − x)TeO2 (x = 20 and 25 mol%) and xV2O5–(25 − x)Li2O–75TeO2 (x = 1, 2, 3, 4 and 5 mol%) glasses were prepared by melt-quenching and their thermal and structural properties were characterized by differential scanning calorimetry, Raman spectroscopy, high-energy X-ray diffraction and neutron diffraction and reverse Monte Carlo (RMC) simulations. The glass transition temperature increases steadily with an increase in V2O5 mol% in lithium tellurite glasses due to an increase in the average single bond energy of the glass network. The X-ray and neutron diffraction structure factors were modelled by RMC technique and the Te–O distributions show the first peak in the range 1.85–1.90 Å, with V–O = 1.75–1.95 Å, Li–O = 1.85–2.15 Å and O–O = 2.70–2.80 Å. The average Te–O coordination number decreases with an increase in Li2O mol% in lithium tellurite glasses, and the V—O coordination decreases from 5.12 to 3.81 with an increase in V2O5 concentration in vanadium lithium tellurite glasses. The O–Te–O, O–V–O, O–Li–O and O–O–O linkages have maxima in the ranges 86°–89°, 82°–87°, 80°–85° and at 59o, respectively. The structural analysis of tellurite glasses reveal significant short-range and medium-range disorder due to the existence of a wide range of Te–O and Te–Te distances in the first coordination shell.

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