Terminal Oxygens in Amorphous TeO₂

Understanding the structure of single-component glasses is essential for developing structural models of more complex multicomponent glasses. Currently, such models for tellurite systems are purely qualitative. This study presents neutron diffraction and Raman spectroscopy measurements of the structure of pure amorphous TeO2, showing that it is formed from a combination of two-thirds [TeO4] pseudo-trigonal bipyramids and one-third [TeO3] trigonal pyramids with a terminal oxygen. This is in contrast to all crystalline polymorphs of TeO2, which are formed solely from the four-coordinated units. Using this result, a quantitative model has been developed that successfully predicts the average Te–O coordination number, nTeO, for a series of potassium tellurite glasses, xK2O·(100 – x)TeO2. The observed nTeO is constant up to 15 mol % K2O due to the presence of terminal oxygen atoms in the tellurite network.