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57Fe Mössbauer Effect Study of Al-Substituted Lepidocrocites

Published online by Cambridge University Press:  28 February 2024

E. De Grave ,
G. M. da Costa ,
L. H. Bowen ,
U. Schwertmann  and
R. E. Vandenberghe
E. De Grave
Affiliation:
Department of Subatomic and Radiation Physics, University of Gent, B-9000 Gent, Belgium
G. M. da Costa
Affiliation:
Department of Subatomic and Radiation Physics, University of Gent, B-9000 Gent, Belgium
L. H. Bowen
Affiliation:
Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27965-8204, USA
U. Schwertmann
Affiliation:
Lehrstuhl für Bodenkunde, Technische Universität München, D-85354 Freising-Weihenstephan, Germany
R. E. Vandenberghe
Affiliation:
Department of Subatomic and Radiation Physics, University of Gent, B-9000 Gent, Belgium
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Abstract

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Seven Al-containing lepidocrocite samples, γ-Fe1−xAlxOOH, prepared from FeCl2/Al(N03)3 solutions with initial Al/(Al + Fe) mole ratios Ci of 0.0025, 0.01, 0.025, 0.05, 0.075, 0.10 and 0.15 mol/mol, were examined by means of Mössbauer spectroscopy at room temperature (RT) and at various temperatures in the range of 8 to 80 K. The spectra at RT and 80°K consist of broadened quadrupole doublets and were analyzed in terms of a single doublet and of a model-independent quadrupole-splitting distribution, the latter yielding the best fit. The observed variations of the quadrupole-splitting parameters with increasing Ci are inconclusive as to whether the Al cations are substituting into the structure. The temperature at which the onset of magnetic ordering is reflected in the spectra, was measured by the thermoscan method with zero source velocity. A gradual shift from 50 K for Ci = 0.0025 mol/mol to 44 K for Ci = 0.10 mol/mol was observed for that temperature. As compared to earlier studies of Al-free γ-FeOOH samples with similar morphological characteristics, the fractional doublet area in the mixed sextet-doublet spectra at 35 K is significantly higher for the present lepidocrocites. This observation is ascribed to the substitution of Al cations into the lepidocrocite structure. A similar conclusion is inferred from the variation with Ci of the maximum-probability hyperfine field derived from the spectra recorded at 8 K and fitted with a model-independent hyperfine-field distribution. The magnetic results suggest that for the sample corresponding to Ci = 0.15 mol/mol, not all of the initially present Al has been incorporated into the structure.

Keywords

Al SubstitutionLepidocrociteMössbauer Spectra
Type
Research Article
Information
Clays and Clay Minerals , Volume 44 , Issue 2 , April 1996 , pp. 214 - 219
Copyright
Copyright © 1996, The Clay Minerals Society

Footnotes

†

Contribution No. SSF95-01-06 from the Department of Subatomic and Radiation Physics, University of Gent, Belgium.

‡

Research Director, National Fund for Scientific Research, Belgium

§

On leave from Departamento de Quimica, Universidade Federal de Ouro Preto, Ouro Preto, MG, Brazil.

References

Amarasiriwardena, D.D., De Grave, E., Bowen, L.H. and Weed, S.B.. 1986. Quantitative determination of aluminum-substituted goethite-hematite mixtures by Mössbauer spectroscopy. Clays & Clay Miner 34: 250–256.CrossRefGoogle Scholar
Bocquet, S., Pollard, R.J. and Cashion, J.D.. 1992. Dynamic magnetic phenomena in fine-particle goethite. Phys Rev B 46: 11657–11664.CrossRefGoogle ScholarPubMed
Bowen, L.H., De Grave, E. and Vandenberghe, R.E.. 1993. Mössbauer effect studies of magnetic soils and sediments. In: Long, G.J., Grandjean, F., editors. Mössbauer spectroscopy applied to magnetism and materials science. Vol. 1. New York: Plenum Press. 115–159.CrossRefGoogle Scholar
Bowen, L.H., De Grave, E. and Bryan, A.M.. 1994. Mössbauer studies in external field of well-crystallized Al-maghemites made from hematite. Hyperfine Interact 94: 1977–1982.CrossRefGoogle Scholar
Chambaere, D. and De Grave, E.. 1984. On the Néel temperature of β-FeOOH: structural dependence and its implications. J Magn Magn Mater 42: 263–268.CrossRefGoogle Scholar
De Grave, E., Bowen, L.H. and Weed, S.B.. 1982. Mössbauer study of aluminum-substituted hematites. J Magn Magn Mater 27: 98–108.CrossRefGoogle Scholar
De Grave, E., Persoons, R.M., Chambaere, D.G., Vandenberghe, R.E. and Bowen, L.H.. 1986. An 57Fe Mössbauer effect study of poorly crystalline γ-FeOOH. Phys Chem Minerals 13: 61–67.CrossRefGoogle Scholar
Le Caër, G. and Dubois, J.M.. 1979. Evaluation of hyperfine parameter distributions from overlapped Mössbauer spectra of amorphous alloys. J Phys E: Sci Instrum 12: 1083–1090.CrossRefGoogle Scholar
Mørup, S. and Topsøe, H.. 1976. Mössbauer studies of thermal excitations in magnetically ordered microcrystals. Appl Phys 11: 63–66.CrossRefGoogle Scholar
Mørup, S. and Tronc, E.. 1994. Superparamagnetic relaxation of weakly interacting particles. Phys Rev Lett 72: 3278–3281.CrossRefGoogle ScholarPubMed
Murad, E. and Schwertmann, U.. 1983. The influence of aluminium substitution and crystallinity on the Mössbauer spectra of goethite. Clay Miner 18: 301–312.CrossRefGoogle Scholar
Murad, E. and Schwertmann, U.. 1984. The influence of crystallinity on the Mössbauer spectrum of lepidocrocite. Mineral Mag 48: 507–511.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 Miner 38: 209–212.CrossRefGoogle Scholar
Vandenberghe, R.E., De Grave, E. and de Bakker, P.M.A.. 1994. On the methodology of the analysis of Mössbauer spectra. Hyperfine Interact 83: 29–49.CrossRefGoogle Scholar
Wivel, C.O. and Mørup, S.. 1981. Improved computational procedure for evaluation of overlapping hyperfine parameter distributions in Mössbauer spectra. J Phys E: Sci Instrum 14: 605–610.CrossRefGoogle Scholar