engleski

Microstructural properties of hydrothermally synthesized iron/titanium oxide nanoparticles

Iron/titanium oxide nanoparticles with initial molar ratio Fe/(Fe+Ti)  0.5 were hydrothermally synthesized at 180oC in aqueous ammonia solution (pH = 9). The titanium and iron precursors were TiCl4 and FeCl3, respectively. The amount of doped iron strongly affected structural properties as well as degree of dispersion of iron in Fe-Ti-O system. Anatase was the dominant phase in the iron/titanium oxide samples with Fe/(Fe+Ti)  0.25. The iron/titanium oxide sample with Fe/(Fe+Ti) = 0.5 contained no anatase. The average crystallite size of the anatase phase in iron/titanium oxide samples decreased with the increase of iron doping. The appearance of the small diffraction lines of hematite in the product with 10 mol% of iron indicates that the solid solubility limit of Fe3+ ions in the TiO2 lattice has been reached. However, the results of precise unit-cell parameters measurement, obtained using both Rietveld and Le Bail refinements of the powder diffraction patterns with added silicon as an internal standard, show that the unit-cell volume of anatase increase with the increase of iron content up to 15 mol%. Iron that could not be incorporated in the TiO2 lattice separated in the form of hematite (α-Fe2O3) as shown using Mössbauer spectroscopy and XRD. The diffuse reflectance spectra were used for band gap energy calculations (Fig. 1). The band gap energy of undoped TiO2 sample was 3.1 eV (Fig. 1), whereas the band gap energy of Fe-Ti-O samples doped with up to 10 % showed blue shift (3.3 eV). The significant red shift (from 3.3 to 2.4 eV) was observed for the highly iron doped TiO2 samples (from 10 to 50 % of doped iron).

Iron/titanium oxide nanoparticles ; hydrothermal synthesis ; XRD ; Mossbauer spectroscopy ; band gap

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