Compositional dependence of the stress-optic response in zinc tellurite glasses

The compositional dependence of the stress-optic coefficient of zinc tellurite glass was studied and correlated with local structure. The stress-optic response was determined by using the Sénarmont method, while local structure was determined by using x-ray absorption fine structure spectroscopy (XAFS) at the zinc K-edge, and Raman spectroscopy. Estimates of bond lengths d and coordination numbers NC were made and the ratio d/NC showed a strong correlation with the stress-optic coefficient, in agreement with the empirical model proposed previously by Zwanziger and co-workers. This finding is significant because both glass constituents, namely ZnO and TeO2, have complex electronic structure and are predicted by the empirical model to be at the threshold between positive and negative stress response; these glasses thus represent a rigorous check of the empirical model.