¹²⁵Te NMR study of MO-TeO₂ (M = Mg, Zn, Sr, Ba and Pb) glasses

The structure of MO-TeO₂ (M=Mg, Zn, Sr, Ba and Pb) glasses has been studied by means of ¹²⁵Te static NMR technique. The fraction of TeO₄ trigonal bipyramid (tbp), N₄ decreased and that of TeO₃ trigonal pyramid (tp), N₃ increased almost linearly up to 33.3 mol% MO and rapidly in the range of 33.3 to 40 mol% MO, with increasing MO content. It was found that the glasses containing MO in the range of 40 to 45 mol% MO consisted only of TeO₃ tp. On the basis of the structural model proposed in a previous paper, the fractions of TeO₁ tbp without a non-bridging oxygen (NBO) atom, TeO_4/2 (N₄⁰), TeO₄ tbp with an NBO atom, O_3/2 Te-O^- (N₄^-) and TeO₃ tp with two NBO atoms, O_1/2Te(=O)-O^- (N₃^-) were calculated. The structural change for MO-TeO₂ glasses in the range of 0 to 33.3 mol% MO could be well represented by the model previously proposed for alkali tellurite binary glasses. A new model which represents the structural change for MO-TeO₂ glasses containing more than 33.3 mol% MO has been proposed.