The effects of trace elements on the crystal properties of TiO 2

Abstract

The effects of trace element doping of TiO 2 on the crystal growth and on the anatase-to-rutile phase transformation of TiO 2 were investigated. The co-precipitation process, from sulfate solution, of doped (Cr, Fe, V, Nb, Si, P) TiO 2 was also studied. The heating temperatures were 473, 673, 873, 993, 1133 K and a higher temperature needed to achieve a rutile content of 98–99%. Traces of reduced titanium were found in freshly calcined anatase by X-ray diffraction. Pure anatase structure was found in 85% of the samples heated below 1000 K. Anatase-to-rutile transformation was accelerated by the mmol% content of Nb, Cr, Si, and Fe in TiO 2. Interaction of co-precipitated or impregnated cations was found critical in the phase transformation process. Nb retarded the crystal growth during calcination. Sulfate ions minimized the specific surface area of TiO 2 heated at low temperatures. These results of doped TiO 2 serve to promote the development of new high-technology TiO 2 products for photocatalytic purposes.