Characterization of La-Doped TiO2 Nanopowders by Raman Spectroscopy
M. Šćepanovića, S. Aškrabića, V. Bereca, A. Golubovića, Z. Dohčević-Mitrovića, A. Kremenovićb and Z.V. Popovića
a Center for Solid State Physics and New Materials, Institute of Physics, Pregrevica 118, 11080 Belgrade, Serbia
b Faculty of Mining and Geology, Laboratory for Crystallography, University of Belgrade, Djušina 7, 11000 Belgrade, Serbia
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Titanium dioxide (TiO2) nanopowders doped with 0.65, 1, 2, 3 and 4 wt.% of lanthanum ions (La3+) were synthesized by sol-gel technology. Dependence of structural and morphological characteristics of nanopowders on La3+ content and synthesis conditions is investigated by the Raman spectroscopy. Very intensive modes observed in the Raman spectra of all nanopowder samples are assigned to anatase phase of TiO2. Additional Raman modes of extremely low intensity can be related to the presence of certain amount of highly disordered brookite phase in nanopowders. Dependence of the intensity ratio of the Raman modes which originate from anatase and brookite on doping conditions is specially analyzed. In order to estimate the variation of nanocrystallite size with dopant content, shift and asymmetrical broadening of the most intensive Eg Raman mode of anatase are analyzed by phonon confinement model. The obtained results are compared with the results of X-ray diffraction spectroscopy. Special attention is dedicated to the changes in the Raman spectra of pure and La-doped TiO2 nanopowders observed after high temperature treatment.
DOI: 10.12693/APhysPolA.115.771
PACS numbers: 81.20.Fw, 81.07.Wx, 78.30.-j, 07.05.Tp