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 G e K-edge EXAFS spectroscopy using synchrotron radiation. The average n earest-neighbor Ge-O interatomic distances ranged between 0.173 and 0. 178 nm depending on the P2O5 content. The interatomic distances and co ordination 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-c oordinate Ge atoms (N-6) were estimated on the basis of the observed G e-O distances and ionic radii, and the observed results support the pa rtial change of coordination numbers from four to six.