ANOMALOUS SCATTERING AND EXAFS STUDY OF GEO2 - P2O5 GLASS SYSTEM

Analyses of the local atomic arrangements around Ge atoms were carried out on GeO2-P2O5 glasses with three different P2O5 contents (11.4, 20.5 and 24.4 mol%) with the anomalous X-ray scattering method and the Ge K-edge EXAFS spectroscopy using synchrotron radiation. The average nearest-neighbor Ge-O interatomic distances ranged between 0.173 and 0.178 nm depending on the P2O5 content. The interatomic distances and coordination numbers obtained by the anomalous scattering method and by the EXAFS analysis are in agreement. EXAFS results based on two-shell fitting indicate that some Ge atoms change their coordination numbers from four to six depending on the P2O5 content. The fractions of six-coordinate Ge atoms (N-6) were estimated on the basis of the observed Ge-O distances and ionic radii, and the observed results support the partial change of coordination numbers from four to six.