Cation occupancy sites in synthetic Co-doped magnetites as determined with X-ray absorption (XAS) and Mossbauer spectroscopies

In the present work, cobalt-doped magnetites, prepared by the co-precipitation method, were mainly studied by Xray absorption and Mossbauer spectroscopies. From the chemical analysis, it was observed that the continuous increase of Co2+ is followed by a simultaneous decrease of the Fe2+ contents, in the spinel structure. Room temperature Mossbauer parameters indicate that samples are formed by single crystallographic phases of pure magnetite or its Co-substituted analogs. Basing on the inversion of intensities of the Mossbauer lines 1 (leftmost, in the negative Doppler velocity scale) and 2, it is assumed that the Co-substitution occurs essentially, if not only, at octahedral sites of the spinel structure. XAS results obtained at Co K-edge confirm that the Co-substitution occurs preferentially at octahedral coordination sites. (C) 2004 Elsevier B.V. All rights reserved.