Defects and Cation Diffusion in Magnetite (VI): Point Defect Relaxation and Correlation in Cation Tracer Diffusion

1986 ◽  
Vol 90 (7) ◽  
pp. 564-575 ◽  
Author(s):  
R. Dieckmann ◽  
H. Schmalzried
Keyword(s):  
Point Defect ◽  
Tracer Diffusion ◽  
Cation Diffusion ◽  
Defect Relaxation

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

1994 ◽  
Vol 369 ◽  
Author(s):  
J. TÖpfer ◽  
R. Dieckmann
Keyword(s):  
Point Defect ◽  
Tracer Diffusion ◽  
Oxygen Activity ◽  
Spinel Solid Solution ◽  
Low Oxygen ◽  
Cation Diffusion ◽  
Cationic Composition ◽  
Deviation From Stoichiometry ◽  
Tracer Diffusion Coefficients ◽  
Defect Species

AbstractThe 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.

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

1994 ◽  
Vol 369 ◽  
Author(s):  
Sanjeev Aggarwal ◽  
Rudiger Dieckmann
Keyword(s):  
Diffusion Coefficients ◽  
Tracer Diffusion ◽  
Oxygen Activity ◽  
Spinel Solid Solution ◽  
Low Oxygen ◽  
Cation Diffusion ◽  
Deviation From Stoichiometry ◽  
Diffusion Studies ◽  
Tracer Diffusion Coefficients ◽  
Point Defect Structure

AbstractCation 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.

Transient creep of olivine: Point-defect relaxation times

1988 ◽  
Vol 57 (5) ◽  
pp. 779-789 ◽  
Author(s):  
S. J. Mackwell ◽  
D. Dimos ◽  
D. L. Kohlstedt
Keyword(s):  
Point Defect ◽  
Relaxation Times ◽  
Transient Creep ◽  
Defect Relaxation

Anelastic Effects in YBa 2 Cu 3 O 7-δ : A Study of the Point Defect Relaxation Observed for 0.6 < δ < 1

1990 ◽  
Vol 12 (3) ◽  
pp. 281-286 ◽  
Author(s):  
S. de Brion ◽  
J. Y Henry ◽  
R Calemczuk ◽  
E Bonjour
Keyword(s):  
Point Defect ◽  
Defect Relaxation

Point‐Defect Relaxation in Rutile Single Crystals

1963 ◽  
Vol 34 (10) ◽  
pp. 3095-3104 ◽  
Author(s):  
R. D. Carnahan ◽  
J. O. Brittain
Keyword(s):  
Point Defect ◽  
Single Crystals ◽  
Defect Relaxation
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