RAMAN-SPECTRA OF BO3/2-TEO2 GLASSES

The structure Of BO3/2-TeO2 glasses was investigated by Raman spectroscopy. Glasses with low BO3/2 content have a continuous network structure composed mainly of TeO4 trigonal bipyramids. In the network, a considerable fraction of boron atoms form BO4 groups and a small fraction of boron atoms form B2O5 and BO3 groups. With increase of BO3/2 content, both trigonally coordinated tellurium and tetrahedrally coordinated boron atoms are increased in numbers. Condensed borate groups are formed by condensation of BO4, B2O5 and BO3 groups. In glasses containing nearly 50 mol% BO3/2, a continuous network is constituted by tellurite clusters, B2O5, BO3, BO4 and condensed borate groups. The behavior of boron in the BO3/2-TeO2 system is discussed on the basis of Te-O and B-O bond strengths.