EXAFS Study of Densified GeO2 Glasses

Glasses of composition GeO2 and Li2O-3GeO2 were compressed up to 30 GPa at temperatures from 300 to 773K where sixfold coordination of Ge is stable. Densification of 10 and 15 % was achieved for GeO2 and Li2O-3GeO2 glasses, respectively. Ge EXAFS measurements of Li2O-3GeO2 glasses retrieved from high pressure indicated that the coordination number of Ge is 4. The second and third neighbor distances (Ge-Ge1 and Ge-Ge2) determined by EXAFS show that the densification mechanism is explained by more distorted packing of GeO4 tetrahedra than that in ambient glass. Coordination change by compression in the present Li2O-3GeO2 and GeO2 glasses is reversible. The quenchability of the sixfold coordination of Ge in germanate glass is discussed.