EXAFS AND RDF STUDIES OF TEO2-LI2O GLASSES

Local arrangements around Te atoms in TeO2-Li2O glasses with four different Li2O contents (15, 20, 25, and 30 mol%) are observed by Te K EXAFS spectroscopy and x-ray diffraction by making use of synchrotron radiation. EXAFS results based on the two-shell fitting method indicate that interatomic distances of Te-O in axial (ax) sites decrease from 0.208 to 0.197 nm with increasing Li2O contents, while distances between tellurium atom and oxygen atoms in equatorial (eq) sites change slightly from 0.190 to 0.188 nm. Total coordination numbers seem to decrease slightly with increasing Li2O contents. These results suggest the coordination states of tellurium atoms are changed from TeO4 trigonal bipyramids to TeO3+1 polyhedra and TeO3 trigonal pyramids. RDF results also suggest the change of coordination states of tellurium atoms. TeO3+1 polyhedra in glasses are considered to be connected at the vertices with Te-O-eq(ax)-Te or Te-O-ax(ax)-Te linkage as seen in crystalline alpha-Li2Te2O5.