α-V1.08P0.92O5 at 22°C

Abstract

Abstract. oc-Vl.os(1)Po.9205, tetragonal, P4/n; a = 6.011 (4), c=4.452 (4) A; Z=2, Dealt=3"39 gcm -3, 147 independent reflexions. The structure was refined by full-matrix least-squares methods, R=0.076, with scintillation counter-measured intensities and monochromatized Mo K~ radiation. The composition was determined by varying the occupancy of the tetrahedral site. The vanadyl bond length is 1.578 (9) /k. Unlike stoichiometric 0c-VPO5 no evidence of positional disorder was found.Introduction. Crystals were grown in a Pt crucible in an attempt to produce large single crystals by the Czochralski procedure. The present crystals grew at the interface with the crucible and at the surface of the charge. Crystals offl-VPO5 and some as yet unidentified crystals were found near the centre of the crucible.A crystal with dimensions 0.5 × 0.5 × 0.05 mm was used for data collection with a Syntex P] diffractometer. The data, corrected for Lorentz-polarization and absorption, were used together with the parameters of disordered ~-VPO5 (Jordan & Calvo, 1973)to refine the structure. Convergence of the least-squares refinement yielded an R of 0.12 with residual peaks in the difference Fourier map that indicated that the compound was non-stoichiometric. Subsequent refinements, with weights set as w-1 = 0.9 + 0.20F+ 0.005F 2, and with the extinction parameter varied indicated that 8 (1)% of the tetrahedral sites were occupied by V.

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

“…The VO 4 were expected to behave such as the VO 4 or PO 4 in a special form [16] of α-VOPO 4 , thus, VO 4 with four overbonded uniform bonds. Hence, the VO 5 units must exist as VO 5 + 1 with V=O and V···O bonds and underbonded V-O bonds.…”

“…Numerous structures of related crystals of the VPG system are reported [16,[20][21][22][23][24][25][26][27][28]. Some of the structural parameters are listed in Table 1.…”

“…The results are related to the VPG model from Calvo and Jordan [15]. This model is based on the structure of a crystal [16] where 8% of the PO 4 units (Q 0 ) of α-VOPO 4 are replaced for VO 4 tetrahedra which adopt exactly the site geometry of the PO 4 . This behavior is suggested to be valid also for the VPG of x N 0.5.…”

Catalytic Properties of Silver Vanadium Phosphates in n‐Butane Oxidation – Considerations on the Impact of the [VxOy] Substructure

“…The highly active and selective (VO) 2 P 2 O 7 catalyst has the optical basicity K = 0.49 [33]. Since Ag + ions (K = 1.25 for [20,22,36,38,39].…”

The Mechanism of Alkane Selective Oxidation by the M1 Phase of Mo–V–Nb–Te Mixed Metal Oxides: Suggestions for Improved Catalysts

“…[18,19] This opens the possibility that the V +5 sites responsible for alkane and furan activation may come from the small amounts of VOPO4. [20] As a result, we considered three phases of VOPO4: αΙ, [21] αΙΙ, [22] and the proposed X1-phase. [23,24] We found that…”