Preparation and physicochemical properties of ZrO2 and Fe/ZrO2 prepared bya sol-gel technique

Pure ZrO2 and 0.5-5 wt % iron-containing samples have been prepared by a so l-gel technique and thoroughly characterized by several techniques, X-ray d iffraction (XRD), differential thermal analyses (DTA), diffuse reflectance spectroscopy (DRS), scanning and transmission electron microscopies (SEM an d TEM), X-ray photoelectron spectroscopy (XPS), and other complementary tec hniques. Introduction of iron in zirconia produced a phase transition from monoclinic to tetragonal. In contrast to generally reported values of zirco nia band gap (5 eV), the values of the present samples ranged between 2.3 a nd 3.8 eV, determined from DRS,depending on the preparation conditions and on the iron content. Preliminary experiments of adsorption of different spe cies (nitrite, ethylenediaminetetraacetic acid (EDTA), and Cr(VI)) are also presented and the results explained by a correlation with the physicochemi cal properties of the characterized oxides. Oxygen photoadsorption and oxyg en isotopic exchange (OIE) results can be corelated to the photocatalytic a ctivity recently found, showing the potentiality of this technique for the characterization of photocatalysts in order to account for its photoactivit y.