| Autor: |
Laarj, M., Kacim, S., Gillot, B. |
| Zdroj: |
Journal of Solid State Chemistry; August 1996, Vol. 125 Issue: 1 p67-74, 8p |
| Abstrakt: |
Submicrometer MnxCoFe2−xO4(0 ≤x< 1) spinel particles with a spherical shape were prepared at low temperature from oxalic precursors. Because of their small crystallite size (about 50 nm), these ferrite particles can be oxidized below 400°C giving cubic deficient spinels having both Mn3+and Mn4+ions because of oxido-reduction phenomena. Information about the valence state of the manganese and cobalt ions and cation distribution between tetrahedral (A) and octahedral (B) sites are derived from lattice parameter variation, IR spectroscopy, thermogravimetric analysis, and electrical conductivity. A kinetics study of the oxidation of Mn3+ions shows that oxidation proceeds by cation diffusion through a topotactic reaction with a constant chemical diffusion coefficient forx< 0.60 and variable abovex= 0.80 and an activation energy close to 115 kJ mol−1but, however, depending on manganese substitution content. |
| Databáze: |
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| Externí odkaz: |
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