Fourier Electron Density Maps for Nanostructured TiO<sub>2</sub> and TiO<sub>2</sub>-CeO<sub>2</sub> Sol-Gel Solid

Abstract

Sol-gel TiO2 and TiO2–CeO2 materials were synthesized at pH3 using HNO3 as hydrolysis catalysts. Gels were annealed at 473, 673 and 873 K for 4h. X-ray diffraction Rietveld refinement was used to determine the mean crystallite size, TiO2 stoichiometry (titanium deficiency) and Fourier electronic density maps. It has been found that the fractal surface dimension diminishes on TiO2 a nd TiO2–CeO2 surfaces as the annealing temperature increases. The X-ray diffraction patterns showed nanocrystalline anatase phase in the range of 8.9 to 43.6 nm in depending of the annealing temperature. A dependency between the crystallite size and the titanium deficiency [V+Ti4+] per unit cell was found, as lowest is the crystallite highest is the titanium deficiency. Strong differences on the Fourier electron density map were found on TiO2 and TiO2–CeO2 materials. It was concluded that the sol-gel preparation method favors the formation of nanosized TiO2 with high Ti4+ stoichiometry deficiency.