Structural and spectroscopic studies of iron (III) doped titania powders prepared by sol-gel synthesis and hydrothermal processing

Iron-doped titania powders, of microfine dimensions and iron loadings of up to 5.64 wt.% were prepared by a sol-gel route. Gels, obtained by hydrolysis of titanium alkoxide in an aqueous solution of iron (II) chloride, were subjected to thermal treatment by heating in air or hydrothermal processing in an autoclave. The evolution of the crystalline component was determined by X-ray powder diffraction, and the local environment of the dopant was probed by electron spin resonance spectroscopy. Mossbauer spectroscopy was used to determine the oxidation state of the dopant. Over the iron-loading regime studied here, the anatase-rutile transition is inhibited at low dopant levels with respect to undoped titania. The effect becomes less pronounced as iron-loading is increased. Indeed the crystalline composition of the powders as a function of firing temperature is dependent not only on iron loading level but also on its dispersion within the titania matrix. This response is discussed in the context of the solution-based synthetic routes employed here. (C) 2003 Elsevier Ltd. All rights reserved.