V3.047O7, a new high-pressure oxide with the simpsonite structure

Reaction between alpha-V2O5 and NaN3 has been studied at pressures from 5.0 to 6.0 GPa and temperatures from 600 to 800A degrees C using Toroid high-pressure chambers. A new oxide, V3.047O7 (VO2.297), isostructural with simpsonite, Al4Ta3O13(OH), has been detected in samples with the initial composition 0.2NaN(3) center dot V2O5 after high-temperature, high-pressure processing at p = 5.0 GPa and t = 800A degrees C for 2 min. The crystal structure of the oxide has been refined by the Rietveld method using X-ray powder diffraction data: a = 7.35136(2) , c = 4.51462(2) , V = 211.294(1) (3), Z = 2, sp. gr. P3. Each vanadium atom in this structure is coordinated by six oxygens in the form of a [VO6] octahedron. The synthesized oxide is a second compound with the simpsonite structure. We have measured the infrared transmission and Raman spectra of V3.047O7. Electrical measurements have demonstrated that the material is a semiconductor.