title: Preparation and topotactical oxidation of ScVO3 with bixbyte structure: a low-temperature route to stabilize the new defect fluorite ScVO(3.5) metastable phase.
abstract: ScVO3 has been prepared by controlled reduction of a ScVO4 precursor under an H2/N2 flow at 1250 degrees C. The crystal structure of this material has been studied at room temperature by Rietveld refinement of high-resolution neutron powder diffraction (NPD) data. Sc3+ and V3+ are distributed at random over the metal sites of a C-M2O3 bixbyite-type structure, space group Ia3, a = 9.6182(1) Angstroms. The thermal analysis of ScVO3 in an air flow shows two subsequent oxidation processes, with a final reversal to ScVO4 above 600 degrees C. An intermediate phase of composition ScVO(3.5), containing V4+ cations, can be isolated by isothermal annealing at 350 degrees C in air. This metastable phase has been identified by X-ray diffraction (XRD) as a fluorite-type oxide (space group Fm3m, a = 4.947(2) Angstroms), also showing a random distribution of Sc and V cations over the metal positions. The Rietveld refinement of the ScVO(3.5) structure from powder XRD data in a fluorite structural model yields abnormally high thermal factors for the oxygen atoms, suggesting oxygen mobility in this metastable material.
authors.affiliation: Instituto de Ciencia de Materiales, CSIC, Cantoblanco, 28049 Madrid, Spain.
authors.forename: José Antonio
authors.initials: JA
authors.lastname: Alonso
authors.forename: María Teresa
authors.initials: MT
authors.lastname: Casais
authors.forename: María Jesús
authors.initials: MJ
authors.lastname: Martínez-Lope