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Point Defects and Cation Tracer Diffusion in (CrxFe1-x)3-δO4 Spinels

Published online by Cambridge University Press:  16 February 2011

J. TÖpfer  and
R. Dieckmann
J. TÖpfer
Affiliation:
Department of Materials Science and Engineering, Cornell University, Ithaca, NY 14853- 1501, USA
R. Dieckmann
Affiliation:
Department of Materials Science and Engineering, Cornell University, Ithaca, NY 14853- 1501, USA
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Abstract

The cation diffusion in the spinel solid solution (CrxFe1-x)3-δO4 (0 ≤ x ≤ 0.5) was experimentally investigated at 1200 °C as a function of oxygen activity, aO2 (= PO2/P°with P° = 1 bar) and cationic composition, x. Cation tracer diffusion coefficients, DMe' of Me = Co, Cr, Fe and Mn, were determined using the radioactiveisotopes Co-60, Cr-51, Fe-59 and Mn-54. For each cationic composition V-shaped log DMe vs. log aO2 plots were obtained. The observed oxygen activity dependences indicate that the cation diffusion is determined by different point defect species prevailing at high and low oxygen activities, respectively. The observed oxygen activity dependences, in comparison with considerations based on point defect thermodynamics, suggest that cations diffuse via cation vacancies at high aO2' while at low aO2 cation interstitials prevail in the cation diffusion. In addition, new experimental data for tihe deviation from stoichiometry ≤in (CrxFe1-x)3-≤O4 are presented and discussed.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 369: Symposium U – Solid State Ionics IV , 1994 , 319
Copyright
Copyright © Materials Research Society 1995

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References

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