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The Influence of Aluminum on Iron Oxides: XIV. Al-Substituted Magnetite Synthesized at Ambient Temperatures

Published online by Cambridge University Press:  02 April 2024

U. Schwertmann  and
E. Murad
U. Schwertmann
Affiliation:
Lehrstuhl für Bodenkunde, Technische Universität München, D-8050 Freising-Weihenstephan, Federal Republic of Germany
E. Murad
Affiliation:
Lehrstuhl für Bodenkunde, Technische Universität München, D-8050 Freising-Weihenstephan, Federal Republic of Germany
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Abstract

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Mixtures of magnetite and goethite were formed by the slow oxidation of mixed FeCl2-AlCl3 solutions in an alkaline environment at room temperature. The compositions of the products ranged from almost exclusively magnetite in Al-free systems to goethite only at Al/(Al + Fe) ≈ 0.3. The magnetic phase consisted of a partly oxidized (Fe2+/Fe3+ < 0.5), Al-substituted magnetite. The unit-cell edge length a of the magnetite decreased with increasing Al(Al ≈ 0–0.37 per formula unit, corresponding to 0–14 mole % Al) and decreasing Fe2+ in the structure as described by the empirical relationship α(A) = 8.3455 + 0.0693 Fe2+ - 0.0789 Al. A correlation between the experimentally determined a and that calculated from the unit-cell edge lengths of end-member magnetite, maghemite, and hercynite was highly significant (r = .96) although shifted by about 0.01 Å. Mössbauer spectra showed Al to have entered preferentially the tetrahedral rather than the octahedral sites at low Al substitutions (<0.15 per formula unit), perhaps because of steric reasons. With increasing Al substitution the crystal size of magnetite decreased and structural strain increased, indicating that the structure had a limited capability to incorporate Al under these synthesis conditions. The capacity of the goethite structure to tolerate more Al may explain why goethite replaced magnetite at higher Al concentrations.

Keywords

AluminumGoethiteIron oxideMagnetiteMössbauer spectroscopyX-ray powder diffraction
Type
Research Article
Information
Clays and Clay Minerals , Volume 38 , Issue 2 , April 1990 , pp. 196 - 202
Copyright
Copyright © 1990, The Clay Minerals Society

References

Annersten, H. and Hafner, S. S., 1973 Vacancy distribution in synthetic spinels of the series Fe3O4-γ-Fe2O3 Z. Kris-tallogr. 137 321 – 340.Google Scholar
Bauminger, R., Cohen, S. G., Marinov, A., Ofer, S. and Segal, E., 1961 Study of the low-temperature transition in magnetite and the internal fields acting on iron nuclei in some spinel ferrites, using Mössbauer absorption Phys. Rev. 122 1447 – 1450.CrossRefGoogle Scholar
Coey, J. M. D. Morrish, A. H. and Sawatzky, G. A., 1971 A Mössbauer study of conduction in magnetite J. Physique 32C1 271 – 273.Google Scholar
Dehe, G., Scidel, B., Melzer, K. and Michalk, C., 1975 Determination of a cation distribution model of the spinel system Fe3-xAlxO4 Phys. Stat. Sol. 31 439 – 447.CrossRefGoogle Scholar
Fey, M. V. and Dixon, J. B., 1981 Synthesis and properties of poorly crystalline hydrated aluminous goethites Clays & Clay Minerals 29 91 – 100.CrossRefGoogle Scholar
Golden, D. C., 1978 Physical and chemical properties of aluminum-substituted goethite North Carolina Ph.D. thesis, Department of Soil Science, North Carolina State University, Raleigh.Google Scholar
Hill, R.J., 1984 X-ray powder diffraction profile refinement of synthetic hercynite Amer. Mineral. 69 937 – 942.Google Scholar
Klug, H. P. and Alexander, L. E., 1974 X-ray Diffraction Procedures for Polycrystalline and Amorphous Materials New York Wiley.Google Scholar
Michel, A. and Pouillard, E., 1949 Sur une nouvelle famille de sesquioxydes de fer cubiques Acad. Sci. Paris, Compt. Rend. 228 680 – 681.Google Scholar
Murad, E. and Bowen, L. H., 1987 Magnetic ordering in Al-rich goethites: Influence of crystallinity. Amer. Minerai. 72 194 – 200.Google Scholar
Murad, E. and Schwertmann, U., 1986 Influence of Al substitution and crystal size on the room-temperature Mössbauer spectrum of hematite Clays & Clay Minerals 34 1 – 6.CrossRefGoogle Scholar
Rosenberg, M., Deppe, P., Janssen, H. U., Brabers, V. A. M. Li, F. S. and Dey, S., 1985 A Mössbauer study of Al and Ga substituted magnetite J. Appl. Phys. 57 3740 – 3742.CrossRefGoogle Scholar
Schulze, D. G., 1984 The influence of aluminum on iron oxides. VIII. Unit-cell dimensions of Al-substituted goethites and estimation of Al from them Clays & Clay Minerals 32 36 – 44.CrossRefGoogle Scholar
Schulze, D. G. and Schwertmann, U., 1987 The influence of aluminum on iron oxides. XIII. Properties of goethites synthesized in 0.3 M KOH at 25°C Clay Miner. 22 83 – 92.CrossRefGoogle Scholar
Schwertmann, U., Stucki, J. W., Goodman, B. A. and Schwertmann, U., 1988 Some properties of soil and synthetic iron oxides Iron in Soils and Clay Minerals Dordrecht/Boston D. Reidel 203 – 250.CrossRefGoogle Scholar
Schwertmann, U. and Fechter, H., 1984 The influence of aluminum on iron oxides. XI. Aluminum-substituted mag-hemite in soil and its formation Soil Sci. Soc. Amer. J. 48 1462 – 1463.CrossRefGoogle Scholar
Schwertmannn, U., Fitzpatrick, R. W., Taylor, R. M. and Lewis, D. G., 1979 The influence of aluminum on iron oxides. II. Preparation and properties of Al-substituted hematites Clays & Clay Minerals 27 105 – 112.CrossRefGoogle Scholar
Schwertmann, U. and Wolska, E. (1990) The influence of aluminum on iron oxides. XV. Al-for-Fe substitution in synthetic lepidocrocite: Clays & Clay Minerals 38, (in press).Google Scholar
Taylor, R. M. and Schwertmann, U., 1978 The influence of aluminum on iron oxides. I. The influence of Al on Fe oxide formation from the Fe(II) system Clays & Clay Minerals 26 373 – 383.CrossRefGoogle Scholar