Structure of V2O5-P2O5 glasses by X-ray and neutron diffraction

The atomic structures of two V2O5-P2O5 glasses and vitreous (v-) V2O5 were investigated by X-ray and neutron diffraction. The V=O double bond is a common characteristic of the VOn units that constitute the structures of the glasses. VO5 square pyramids with elongated bonds of -0.190 nm to the pyramidal base are found for the 50V(2)O(5)-50P(2)O(5) glass. These weaker V-O bonds are balanced in V-O-P bridges by overbonded P-O bonds. The V-(IV) sites, which account for 19.7% and 35.2% of the total V sites in the 73V(2)O(5)-27P(2)O(5) and 50V(2)O(5)-50P(2)O(5) glasses, respectively, form similar pyramids in agreement with the structure of crystalline (VO)(2)P2O7. The short-range structure of v-V2O5 and the 73V(2)O(5)-27P(2)O(5) glass informed of mixtures of VO5 and VO4 pyramids. A significant amount of V center dot center dot center dot O distances >022 nm found for all glasses belong either to linkages V=O center dot center dot center dot V or to three-coordinated O sites. (C) 2011 Elsevier B.V. All rights reserved.