Year: 2008
Type: article
Abstract: Powders of α-(Al 1- x Fe x ) 2 O 3 solid solutions prepared by the calcination in air of the corresponding γ-(Al 1- x Fe x ) 2 O 3 powders were studied by several techniques including X-ray diffraction, field-emission-gun scanning electron microscopy, transmission Mössbauer spectroscopy, integral low-energy electron Mössbauer spectroscopy (ILEEMS), and Fe K-edge X-ray absorption near-edge structure (XANES) measurements. The asymmetry of the characteristic Mössbauer doublet representing Fe 3+ ions substituting for Al 3+ ions in the corundum lattice of α-(Al 1- x Fe x ) 2 O 3 solid solutions was resolved and explained for the first time by using two additional subspectra, i.e., a broad second doublet characteristic of a very distorted octahedral site for Fe 3+ and a singlet attributable to α-Fe, suggesting the presence of metallic iron nanoclusters consisting of only a few number of atoms within the solid solution grains. ILEEMS studies showed that the Fe nanoclusters are evenly distributed among the surface layers and the cores of the grains. Fe K-edge XANES measurements further confirmed the occurrence of metallic iron. The proportion of Fe nanoclusters increases when the total iron content is decreased, as does the proportion of distorted octahedral site, suggesting that they are located around the iron nanoclusters. The formation of the metallic Fe nanoclusters in the α-(Al 1- x Fe x ) 2 O 3 grains is thought to be a consequence of the γ → α phase transition which implies structural rearrangement on both the cationic and anionic sublattices.
DOI: 10.1021/jp8032098
Institutions: Universidade Federal de Ouro Preto, Università di Camerino, Centre National de la Recherche Scientifique, Université Toulouse III - Paul Sabatier, Institut National Polytechnique de Toulouse, European Synchrotron Radiation Facility, Ghent University, Centre Interuniversitaire de Recherche et d’Ingénierie des Matériaux
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W1974354635