Glasses from the Ge-rich region [Ge(0.5-0.33x) Ag0.33x Se0.5] of the Ge-Se-Ag phase diagram were synthesised for x = 0.6; 0.7 and 0.8. For comparison a special sample Ge3Se9Ag4 (Ge0.1875 Se0.562 Ag0.25) from the Se-rich region has also been prepared. For the concentrations studied both the X-ray scattering curves as well as the radial electron distribution functions (RDF) were nearly identical. The analysis of the first maximum of the RDF showed that it is composed mainly from GeSe4 tetrahedrons with a bonding distance Ge-Se = 2.37 Å and from AgSe4 tetrahedrons with a bonding distance Ag-Se = 2.63 Å. There is a certain amount of edge-bound tetrahedrons as could be shown by the interpretation of the RDF in the region of 3 Å. The most important conclusion following from the direct analysis of X-ray scattering, consists in that the structure of Ge-Se-Ag glasses is predominantly formed by a GeSe2-like network (corner- and edge-bound tetrahedrons), which is interpenetrated and disrupted by AgSe4 tetrahedrons, which due to stochiometric reasons tend to cluster. That results into corner- and edge-sharing of AgSe4 tetrahedra. These groups then form the migration channels for ionic transport (Ag+).
A contribution to the structure of Ge-Se-Ag glasses
Francesco Rocca
2005
Abstract
Glasses from the Ge-rich region [Ge(0.5-0.33x) Ag0.33x Se0.5] of the Ge-Se-Ag phase diagram were synthesised for x = 0.6; 0.7 and 0.8. For comparison a special sample Ge3Se9Ag4 (Ge0.1875 Se0.562 Ag0.25) from the Se-rich region has also been prepared. For the concentrations studied both the X-ray scattering curves as well as the radial electron distribution functions (RDF) were nearly identical. The analysis of the first maximum of the RDF showed that it is composed mainly from GeSe4 tetrahedrons with a bonding distance Ge-Se = 2.37 Å and from AgSe4 tetrahedrons with a bonding distance Ag-Se = 2.63 Å. There is a certain amount of edge-bound tetrahedrons as could be shown by the interpretation of the RDF in the region of 3 Å. The most important conclusion following from the direct analysis of X-ray scattering, consists in that the structure of Ge-Se-Ag glasses is predominantly formed by a GeSe2-like network (corner- and edge-bound tetrahedrons), which is interpenetrated and disrupted by AgSe4 tetrahedrons, which due to stochiometric reasons tend to cluster. That results into corner- and edge-sharing of AgSe4 tetrahedra. These groups then form the migration channels for ionic transport (Ag+).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
