ON THE NONSTOICHIOMETRY IN RUTILE-TYPE APPROXIMATE-TO-SBVO4

Heating equimolar mixtures of Sb2O3 and V2O5 at 800 degrees C in flowing gas with varying O-2/N-2 ratios produces a continuous nonstoichiometric series of rutile type, i.e., Sb(0.9)V(0.9+x)square(0.2-x)O(4), 0 < x < 0.2, and varying amounts of alpha-Sb2O4. Oxidized Sb(0.9)V(0.9)square(0.2)O(4), a = 4.63, c = 3.03 Angstrom (X ray powder data, XRD), is formed in pure oxygen and exhibits a modulated structure with an approximate supercell: 2 root 2a, 2 root 2b, 4c (electron diffraction, ED). In pure nitrogen, reduced Sb0.9V1.1O4, a = 4.60, c = 3.08 Angstrom (XRD), with the supercell root 2a, root 2b, 2c (ED), is produced. Heating at intermediate partial pressures of oxygen give phases with the basic rutile cell a = b, c (XRD, ED). The formulation of this series is supported by data obtained by Fourier transform infrared spectroscopy. Under reducing conditions (in pure nitrogen), a solid solution series of Sb0.9V1.1O4 and VO2 is observed, i.e., Sb0.9-yV1.1+yO4, 0 < y < 0.7. Vanadium-rich Sb0.2V1.8O4, with a = 4.55, c = 2.99 Angstrom (XRD), exhibits a basic rutile lattice with diffuse intensity between Bragg spots (ED). (C) 1995 Academic Press, Inc.