THE CRYSTAL-STRUCTURE OF SB0.92V0.92O4, DETERMINED BY NEUTRON AND DUAL WAVELENGTH X-RAY-POWDER DIFFRACTION

A phase of approximate composition SbVO4 has been reported in the literature as a key component in new catalysts for the ammoxidation of propane to acrylonitrile. Sb0.92V0.92O4 was prepared by heating equimolar amounts of Sb2O3 and V2O5 in air at 1073 K for 2 hr. The chemical composition was determined by thermogravimetry and energy dispersive X-ray microanalysis. The crystal structure at 293 K was determined, from three powder diffraction data sets recorded with CuKα1, MoKα, and 1.040(1)-Å neutron radiation, using the Rietveld method. Crystal data: Sb0.92V0.92O4, Z = 1, a = 4.625(4), c = 3.040(2) Å, tetragonal space group P 42/mnm, Mr = 222.87, Dcalc = 5.69 g/cm3. All three data sets yield a cation deficient rutile structure and final profile R-values of 3.5, 6.3, and 3.5%. Bond valence sums, calculated from the experimentally determined bond lengths, indicate the oxidation states tobe Sb5+ and V3+/V4+, leading to theformula Sb5+0.92V3+0.28V4+0.64□0.16O4 (the square denotes metal ion vacancies). Bond valence calculations also suggest that OSb2□ is the most favorable configuration for an oxygen associated with a metal vacancy. © 1993 Academic Press, Inc.