| Numéro |
J. Phys. IV France
Volume 7, Numéro C2, Avril 1997
Proceedings of the 9th International Conference on X-Ray Absorption Fine Structure
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| Page(s) | C2-1145 - C2-1146 | |
| DOI | https://doi.org/10.1051/jp4:19972165 | |
J. Phys. IV France 7 (1997) C2-1145-C2-1146
DOI: 10.1051/jp4:19972165
Structural Analysis of CoO-MgO System by XAFS
T. Yoshida1, T. Tanaka1, H. Yoshida1, T. Funabiki1, S. Yoshida1 and S. Hasegawa21 Department of Molecular Engineering, Kyoto University, Kyoto 606-01, Japan
2 Department of Chemistry, Tokyo Gakugei University, Koganei, Tokyo 184, Japan
Abstract
CoO-MgO samples (CoxMg1-xO : x = mol of Co / (mol of Co + mol of Mg)) were prepared by impregnation of
MgO powder with an aqueous solution of Co(NO3)2, followed by calcination at 773 K. The atomic concentration range of
Co for formation of a solid solution and the state of Co ions dissolving in the samples were investigated mainly by XAFS.
XRD patterns showed that the dominant phase is MgO in the samples of x < 0.3 and the formation of small Co3O4
crystallite occurs in the samples of x > 0.3. For the samples of x>0.5, the dominant phase was Co3O4 and the MgO phase
was not detected by XRD. Co K-edge XANES spectra demonstrated that the octahedral symmetry around Co ions in the
sample of x = 0.02 is distorted in the samples of x≥0.04, indicating the change in the state of dissolved Co ions. Co K-edge
EXAFS spectra revealed that Co ions dissolve into MgO matrix substitutionally in the samples of x <0.04 while the
phase separation due to the formation of the Co3O4 structure occurs in the samples of x≥0.04.
© EDP Sciences 1997