Structure-property correlations in lead tellurite glasses by neutron diffraction and reverse Monte Carlo simulations

Structural modeling of xPbO-(100-x)TeO₂ glasses containing x=10, 15 and 20-mol% of PbO was successfully carried out by Reverse Monte Carlo (RMC) simulations of the neutron diffraction data. The structural parameters such as the lead-oxygen, tellurium-oxygen bond lengths and the O-O nearest neighbour distances, the average cation-oxygen coordination numbers, O-Pb-O, O-Te-O and O-O-O bond angle distributions were determined by the RMC analysis. The average Pb-O coordination number is in the range of 5.66±0.196.02± 0.30 whereas the average Te-O coordination number (N_Te-O) decreases steadily from 3.55±0.04 to 3.36±0.03 with an increase in PbO concentration from 10 to 20 mol%. Raman spectroscopy also confirmed that N_Te-O decreases with increase in PbO concentration. The short-range structural properties of glasses namely cation coordinations and cation-oxygen bond length values were used in the Zwanziger model of stress-optic response to predict that xPbO-(100-x)TeO₂ glasses should exhibit negative stress birefringence, a result which is in agreement with the experimental findings reported in the literature. (author)