Hostname: page-component-cd9895bd7-8ctnn Total loading time: 0 Render date: 2024-12-25T11:31:04.212Z Has data issue: false hasContentIssue false
  • English
  • Français

Influence of Nonstoichiometry and the Presence of Maghemite on the Mössbauer Spectrum of Magnetite

Published online by Cambridge University Press:  28 February 2024

G. M. da Costa ,
E. de Grave ,
P. M. A. De Bakker  and
R. E. Vandenberghe
G. M. da Costa
Affiliation:
Laboratory of Magnetism, Department of Subatomic and Radiation Physics, University of Gent, B-9000 Gent, Belgium On leave from Departamento de Química, Universidade Federal de Ouro Preto, Ouro Preto, MG, Brazil
E. de Grave*
Affiliation:
Laboratory of Magnetism, Department of Subatomic and Radiation Physics, University of Gent, B-9000 Gent, Belgium
P. M. A. De Bakker
Affiliation:
Laboratory of Magnetism, Department of Subatomic and Radiation Physics, University of Gent, B-9000 Gent, Belgium
R. E. Vandenberghe
Affiliation:
Laboratory of Magnetism, Department of Subatomic and Radiation Physics, University of Gent, B-9000 Gent, Belgium
*
‡National Fund for Scientific Research, Belgium.
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Several samples of large- and small-particle magnetite (Fe3O4), as well as its thermal decomposition products formed at different temperatures and atmospheres, have been studied extensively by Mössbauer spectroscopy (MS), both with and without an applied field of 6T. Synthetic mixtures of magnetite and poorly- or well-crystallized maghemite have also been studied. Large-particle magnetite (MCD > 200 nm), when heated in air for 12 hours at T < 400°C, transforms to a mixture of well-crystallized hematite and magnetite, the latter one remaining stoichiometric, according to the relative area-ratios obtained from MS. Thermal treatment at 1300°C in a controlled O2 partial pressure, produced a mixture of stoichiometric and nonstoichiometric magnetite, but the latter component seems to be composed of particles with different degrees of nonstoichiometry. The Mössbauer spectra of the decomposition products at T < 200°C in air of small-particle magnetite (MCD ~ 80 nm) could be successfully interpreted as a mixture of magnetite and maghemite, rather than nonstoichiometric magnetite. This suggestion is further supported by the experiments with the synthetic mixtures. It is clearly demonstrated that is not possible, even by applying a strong external field, to separate the contribution of the A-site of magnetite from that of maghemite.

Keywords

MagnetiteMössbauer effectNonstoichiometric magnetite
Type
Research Article
Information
Clays and Clay Minerals , Volume 43 , Issue 6 , December 1995 , pp. 656 - 668
Copyright
Copyright © 1995, The Clay Minerals Society

Footnotes

†

Contribution #SSF95-01-08 from the Department of Subatomic and Radiation Physics, University of Gent.

References

Annersten, H., and Hafner, S. S. 1973. Vacancy distribution in synthetic spinels of the series Fe3O4-γ-Fe2O3. Z. Kristallogr. 137: 321–340.Google Scholar
Aragon, R., Buttrey, D. J., Shepherd, J. P., and Honig, J. M. 1985. Influence of nonstoichiometry on the Verwey transition. Phys. Rev. B 31: 430–436.Google Scholar
Armstrong, J. R., Morrish, A. H., and Sawatzky, G. A. 1966. Mössbauer study of ferric ions in tetrahedral and octahedral sites of a spinel. Phys. Lett. 23: 414–416.Google Scholar
Bate, G., 1975. Oxides for magnetic recording. In Magnetic Oxides, Vol. 2. Craik, D. J., ed. London: John Wiley & Sons, 689–742.Google Scholar
Coey, J. M. D., Morrish, A. H., and Sawatzky, G. A. 1971. A Mössbauer study of conduction in magnetite. J. Physique 32: C1-271–273.Google Scholar
da Costa, G. M., Grave, E. De, Bowen, L. H., Vandenberghe, R. E., and de Bakker, P. M. A. 1994a. The center shift in Mössbauer spectra of maghemite and aluminum maghemites. Clays & Clay Miner. 42: 628–633.Google Scholar
da Costa, G. M., Grave, E. De, de Bakker, P. M. A., and Vandenberghe, R. E. 1994b. Synthesis and characterization of some iron oxides by sol-gel method. J. Solid State Chem. 113: 405–412.Google Scholar
Daniels, J. M., and Rosencwaig, A. 1969. Mössbauer spectroscopy of stoichiometric and nonstoichiometric magnetite. J. Phys. Chem. Solids 30: 1561–1571.Google Scholar
de Bakker, P. M. A., Grave, E. De, Vandenberghe, R. E., Bowen, L. H., Pollard, R. J., and Persoons, R. M. 1991. Mössbauer study of the thermal decomposition of lepidocrocite and characterization of the decomposition products. Phys. Chem. Minerals 18: 131–143.Google Scholar
De Grave, E., Persoons, R. M., Vandenberghe, R. E., and de Bakker, P. M. A. 1993. Mössbauer study of the high-temperature phase of Co-substituted magnetites, Cox-Fe3–xO4. I. x ≤ 0.04. Phys. Rev. B 47: 5881–5893.Google Scholar
Dieckmann, R., and Schmalzried, H. 1977. Defects and cation diffusion in magnetite (I). Ber. Bunsenges. Phys. Chem. 81: 344–347.Google Scholar
Dieckmann, R., 1982. Defects and cation diffusion in magnetite (IV): Nonstoichiometric and point defect structure of magnetite (Fe3-vO4). Ber. Bunsenges. Phys. Chem. 86: 112–118.Google Scholar
Elder, T., 1965. Particle-size effect in oxidation of natural magnetite. J. Appl. Phys. 36: 1012–1013.Google Scholar
Häggström, L., Annersten, H., Ericsson, T., Wäppling, K. W., and Bjarman, S. 1978. Magnetic dipolar and electric quadrupolar effects on the Mössbauer spectra of magnetite above the Verwey transition. Hyperfine Interactions 5: 201–204.Google Scholar
Haley, G., Mullen, J. G., and Honig, J. M. 1989. First order change in hyperfine interaction at the Verwey transition in magnetite. Solid State Comm. 69: 285–287.Google Scholar
Haneda, K., and Morrish, A. H. 1977. Vacancy ordering in γ-Fe2O3 small particles. Solid State Comm. 22: 779–782.Google Scholar
Iida, S., 1980. Structure of Fe3O4 at low temperatures. Phil. Mag. B42: 349–376.Google Scholar
Kakol, Z., and Honig, J. M. 1989. The variation of Verwey transition temperature with oxygen stoichiometry in magnetite. Solid State Comm. 70: 967–969.Google Scholar
Klug, H. P., and Alexander, L. E. 1974. X-Ray Diffraction Procedures for Polycrystalline and Amorphous Materials. New York: John Wiley and Sons.Google Scholar
Mørup, S., Topsøe, H., and Lipka, J. 1976. Modified theory for Mössbauer spectra of superparamagnetic particles: application to Fe3O4. J. Physique 37: C6-287-290.Google Scholar
Mørup, S., and Tronc, E. 1994. Superparamagnetic relaxation of weakly interacting particles. Phys. Rev. Lett. 72: 3278–3281.Google Scholar
Murad, E., and Schwertmann, U. 1993. Temporal stability of a fine-grained magnetite. Clays & Clay Miner. 41: 111–113.Google Scholar
Randani, A., Steinmetz, J., Gleitzer, C., Coey, J. M. D., and Friedt, J. M. 1987. Perturbation de L'echange electronique rapide par les lacunes canoniques dans Fe3-xO4 (x ≤ 0.09). J. Phys. Chem. Solids 48: 217–228.Google Scholar
Sawatzky, G. A., Van der Woude, F., and Morrish, A. H. 1969. Recoilless-fraction ratios for Fe57 in octahedral and tetrahedral sites of a spinel and a garnet. Phys. Rev. 183: 383–386.Google Scholar
Steinthorsson, S., Helgason, Ö., Madsen, M. B., Koch, C. B., Bentzon, M. D., and Mørup, S. 1992. Maghemite in Icelandic basalts. Mineral. Mag. 56: 185–199.Google Scholar
Sugimoto, T., and Matijevic, E. 1980. Formation of uniform spherical magnetite particles by crystallization from ferrous hydroxide gels. J. Colloid Interface Sci. 74: 227–243.Google Scholar
Vandenberghe, R. E., and Grave, E. De. 1989. Mössbauer effect studies of oxidic spinels. In Mössbauer Spectroscopy Applied to Inorganic Chemistry, Vol. 3. Long, G. J., and Grandjean, F., eds. New York: Plenum, 59–182.Google Scholar
Verwey, E. J. W., and Haayman, P. W. 1941. Electronic conductivity and transition point of magnetite (Fe3O4). Physica 8: 979–987.Google Scholar