On the Nonstoichiometry in Rutile-Type ≈SbVO 4

Abstract

Heating equimolar mixtures of Sb 2O 3 and V 2O 5 at 800°C in flowing gas with varying O 2/N 2 ratios produces a continuous nonstoichiometric series of rutile type, i.e., Sb 0.9V 0.9+ x □ 0.2- x O 4, 0 < x < 0.2, and varying amounts of α-Sb 2O 4. Oxidized Sb 0.9V 0.9□ 0.2O 4, a = 4.63, c = 3.03 Å (X ray powder data, XRD), is formed in pure oxygen and exhibits a modulated structure with an approximate supercell: 2 2 a, 2 2 b, 4c (electron diffraction, ED). In pure nitrogen, reduced Sb 0.9V 1.1O 4, a = 4.60, c = 3.08 Å (XRD), with the supercell 2 a, 2 b, 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 Sb 0.9V 1.1O 4 and VO 2 is observed, i.e., Sb 0.9- y V 1.1+ y O 4, 0 < y < 0.7. Vanadium-rich Sb 0.2V 1.8O 4, with a = 4.56, c = 2.99 Å (XRD), exhibits a basic rutilie lattice with diffuse intensity between Bragg spots (ED).