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Non-Stoichiometry and Cation Tracer Diffusion Studies in the Magnetite-UlvÖSpinel Solution, (Fe,Ti)3-δO4

Published online by Cambridge University Press:  16 February 2011

Sanjeev Aggarwal  and
Rudiger Dieckmann
Sanjeev Aggarwal
Affiliation:
Cornell University, Department of Materials Science and Engineering, Bard Hall, Ithaca, NY 14853-1501
Rudiger Dieckmann
Affiliation:
Cornell University, Department of Materials Science and Engineering, Bard Hall, Ithaca, NY 14853-1501
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Abstract

Cation diffusion in the spinel solid solution (Fe1-xTix)3-δO4 (0≤ x ≤ 0.3) was investigated at 1200 ºC as a function of oxygen activity, aO2 and cationic composition, x. At different cationic compositions, cation tracer diffusion coefficients, D*Me of Me = Fe and Ti were measured as a function of oxygen activity. Plots of log DMe vs. loga0 show V-shaped curves, indicating that different types of point defects prevail at high anc low oxygen activities. Thermogravimetric experiments were conducted, using a high resolution microbalance, to determine the deviation from stoichiometry in (Fe1-xTix)3-δO4 at 1200 °C. δversus log aO2 curves are S-shaped. An analysis of the oxygen activity dependences of thecation diffusion coefficients and the deviation from stoichiometry with regardto the point defect structure suggests that at high oxygen activities cation vacancies are the predominant defects governing the deviation from stoichiometry and the diffusion ofcations. At low oxygen activities, and at small values of x, cation interstitials determine the deviation from stoichiometry, while they dominate for 0 ≤ x ≤ 0.3 inthe cation diffusion.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 369: Symposium U – Solid State Ionics IV , 1994 , 307
Copyright
Copyright © Materials Research Society 1995

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