Evidence from HRTEM image processing, XRD and EDS on nanocrystalline iron-doped titanium oxide powders

We investigated nanosized iron-doped TiO2 in the presence of poly(ethylene glycol) (PEG), synthesised by modified sol-gel method, by transmission electron microscopy (TEM), selected area electron diffraction (SAED), high-resolution electron microscopy (HRTEM), HRTEM image processing, energy dispersive X-ray analysis (EDS) and X-ray diffraction (XRD). XRD of as prepared sample showed very broad diffraction maxima of anatase as the dominant phase and an additional maxima ascribed to PEG. The SAED pattern reveals nanocrystalline rings of anatase whereas PEG was barely observed. The presence of PEG in HRTEM image was not observed, while in the Fourier transforms (FT) of HRTEM images the PEG spots were indexed. The Fourier filtered images reveal lattice images of PEG and anatase that constitute the observed grain. The elongation of unit-cell parameter c was found and ascribed to infiltration of PEG and iron into TiO2 anatase lattice. XRD pattern of annealed sample showed again that the anatase is the dominant phase, but the faint lines of rutile and brookite were also detected. PEG was not observed. However, SAED patterns and FT of HRTEM images revealed the Fe2O3 maghemite-q that precipitated during thermal treatment of the as-prepared sample. In both samples, in as-prepared and in annealed, an amorphous phase was observed and its amount determined from HRTEM images. (C) 2001 Elsevier Science B.V. All rights reserved.