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The change of the Ge–O coordination number in potassium germanate glasses probed by neutron diffraction with high real-space resolution
Ist Teil von
Journal of non-crystalline solids, 1999-06, Vol.248 (1), p.1-10
Ort / Verlag
Amsterdam: Elsevier B.V
Erscheinungsjahr
1999
Quelle
Alma/SFX Local Collection
Beschreibungen/Notizen
Neutron diffraction experiments of high real-space resolution are used for studying the Ge–O coordination numbers and the Ge–O bond lengths in two K
2O–GeO
2 glasses (11 and 20 mol% K
2O). On the long-distance side of the first-neighbour Ge-O peak lying at 175 pm, which is likewise found for vitreous GeO
2, appears a clear shoulder. This feature indicates the existence of GeO
n
units larger than GeO
4 tetrahedra. The shoulder is not resolved as a separate peak which could be attributed to Ge–O bonds of GeO
6 octahedra unambiguously. Hence, it cannot be differentiated between GeO
5 or GeO
6 polyhedra being formed in addition to the GeO
4 tetrahedra. The increase of the Ge–O coordination number complies with the concept of a lack of non-bridging oxygen atoms in alkali germanate glasses up to concentrations of about 20 mol% K
2O where the additional oxygen atoms are incorporated in Ge–O–Ge bridges.