EXAFS and XANES studies of local order in oxide glasses: Manganese impurity defects and vanadium low symmetry complexes

The local order in oxide glasses has been studied by means of the EXAFS and XANES techniques. It has been established that manganese impurity defects enter the germanium phosphate glasses in a two-valent state in the form of MnO₆ octahedra with a Mn-O distance of 2.05 Å. In the vanadium phosphate glasses low symmetry complexes of V atoms are present. In these complexes the shorter bond length corresponds well with the double V-O distance in V₂O₅ whereas the average distance of the four O atoms placed in a plane is 0.15 Å longer than the corresponding distance in the crystalline V₂O₅. Besides, VO₄ tetrahedra with a V-O distance of 1.75 Å are present.