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 elec tron microscopy (TEM), selected area electron diffraction (SAED), high-reso lution electron microscopy (HRTEM), HRTEM image processing, energy dispersi ve X-ray analysis (EDS) and X-ray diffraction (XRD). XRD of as prepared sam ple showed very broad diffraction maxima of anatase as the dominant phase a nd an additional maxima ascribed to PEG. The SAED pattern reveals nanocryst alline rings of anatase whereas PEG was barely observed. The presence of PE G 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 s howed 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 precip itated during thermal treatment of the as-prepared sample. In both samples, in as-prepared and in annealed, an amorphous phase was observed and its am ount determined from HRTEM images. (C) 2001 Elsevier Science B.V. All right s reserved.