Structural investigations of the vanadium–antimony–oxygen system

The structural properties and thermally induced behaviour of non-stoicheiometric vanadium antimonate and antimony tetroxide which are formed during solid-state reactions between antimony(III) oxide and vanadium(V) oxide in nitrogen have been investigated. The β-Sb2O4 phase which is formed at temperatures exceeding 800 °C as large hexagonal plate-type crystals is more accurately described as a solid solution of ca. 5% vanadium in β-Sb2O4. The formation of this ‘β-Sb2O4’ phase and the conversion of α- into β-Sb2O4 in the presence of vanadium at lower temperatures than those normally required for the transformation is associated with the incorporation of vanadium into the β-Sb2O4 structure. The oxidative decomposition of monophasic vanadium antimonate at temperatures exceeding 800 °C also gives ‘β-Sb2O4’ which, when subjected to continued thermolysis, generates an outgrowth of vanadium antimonate from the hexagonal crystalline faces. It is proposed that this results from the recombination of ‘β-Sb2O4’ with the vanadium(V) oxide formed in the initial reversible decomposition of vanadium antimonate.