An investigation of phases in the titanium-antimony-oxygen system

Abstract

The nature of solid phases formed in the titanium-antimony-oxygen system by the calcination of precipitates in air has been investigated by powder X-ray diffraction, electron microscopy, Mössbauer spectroscopy, thermal analysis, and temperature programmed reduction techniques. The amorphous solids formed by mild temperature dehydration are converted to crystalline, and frequently multiphasic, materials when calcined at temperatures exceeding ca. 500 °C. The nature of the crystalline materials depends on the relative concentrations of the titanium and antimony cations in the initial precipitates and the calcination temperature. Antimony(V) in monophasic low-antimony content solids induces the structural transformation of the anatase form of titanium dioxide to the rutile modification at a lower temperature than is normally expected. Materials containing an excess of ca. 30% antimony and heated at temperatures exceeding ca. 500 °C are usually multiphasic and contain an antimony-containing rutile related phase. Evidence has been found for the occurrence of the mixed oxide of composition Sb 3Ti 2O 10 in some multiphasic materials. Titanium-antimony oxides calcined at high temperatures in air may be described as solid solutions of low concentrations of antimony(V) in rutile titanium(IV) oxide. The tolerance of rutile titanium dioxide for the incorporation of antimony depends on the temperature and duration of thermal treatment.