EXAFS AND RDF STUDIES OF TEO2-LI2O GLASSES

Local arrangements around Te atoms in TeO2-Li2O glasses with four diff erent Li2O contents (15, 20, 25, and 30 mol%) are observed by Te K EXA FS spectroscopy and x-ray diffraction by making use of synchrotron rad iation. EXAFS results based on the two-shell fitting method indicate t hat 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 sligh tly from 0.190 to 0.188 nm. Total coordination numbers seem to decreas e slightly with increasing Li2O contents. These results suggest the co ordination states of tellurium atoms are changed from TeO4 trigonal bi pyramids to TeO3+1 polyhedra and TeO3 trigonal pyramids. RDF results a lso 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.