Abstract
A series of alkali germanate glasses exhibiting the germanate anomaly, have been investigated using O K-edge XANES. The XANES spectra exhibit sharp pre-edge features that can be attributed to O 1s transitions to O 2p states hybridized with Ge 3d and 4s/p states. These pre-edge features can be used to distinguish between oxygens associated with Ge atoms in 4-, 5- or 6-fold coordination in the glasses. For the 10 mol% K2O-GeO2 composition, which has been studied extensively by neutron scattering, the XANES spectra clearly show the presence of oxygen atoms associated with both 4-fold Ge and 5-fold Ge polyhedra. No 6-fold Ge is observed in any of the glasses except at high alkali contents (~40 mol%).
