Structure of lithium tellurite and vanadium lithium tellurite glasses by high-energy X-ray and neutron diffraction.

ABSTRACT

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 Šand 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.