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

Abstract The atomic structures of two V 2 O 5 –P 2 O 5 glasses and vitreous (v-) V 2 O 5 were investigated by X-ray and neutron diffraction. The V=O double bond is a common characteristic of the VO n units that constitute the structures of the glasses. VO 5 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 P 2 O 7 . The short-range structure of v-V 2 O 5 and the 73V 2 O 5 -27P 2 O 5 glass is formed of mixtures of VO 5 and VO 4 pyramids. A significant amount of V···O distances > 0.22 nm found for all glasses belong either to linkages V=O···V or to three-coordinated O sites.