Letter | Published:

Electron–optical observations of ordered FeNi in the Estherville meteorite

Abstract

Scott and Clarke1, using optical techniques, have recently reported the presence of ordered FeNi (taenite) with the tetragonal Llo structure (AuCu) in over 40 meteorites. The ordered phase occurs in 10–60 µm diameter regions and in 1–5 µm wide rims of clear taenite containing 48–57% Ni (refs 1, 2). In contrast with disordered γ Fe-Ni, the ordered taenite is optically anisotropic. The X-ray diffraction pattern and Mössbauer spectrum of ordered FeNi 3–5 are also similar to that of tetragonal FeNi synthesised using high flux neutron irradiation at 300 ° C of a disordered FeNi alloy in the presence of a magnetic field. Although Mössbauer and X-ray diffraction studies6,7 have been used to detect superstructure in bulk samples, these techniques cannot spatially locate the ordered phase within the microstructure. The present study uses various electron–optical techniques, including transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) and electron probe microanalysis (EPMA) to characterise and to resolve the ordered FeNi phase spatially. In addition, the first TEM evidence (both electron diffraction patterns and centred dark field (CDF) images) for superstructure in clear taenite, is presented.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

References

  1. 1

    Scott, E.R.D. & Clarke, R.S., Nature 281, 360–362 (1979).

  2. 2

    Taylor, G. J. & Heymann, D. Geochim. cosmochim. Acta. 35, 175–188 (1971).

  3. 3

    Petersen, J. R., Aydin, M. & Knudsen, J. M. Phys. Lett. 62A, 192–194 (1977).

  4. 4

    Albertsen, J.R., Jensen, G.B. & Knudsen, J.M. Nature 273, 453–454 (1978).

  5. 5

    Albertsen, J. R., Aydin, M. & Knudsen, J.M. Phys. Scr. 17, 467–472 (1978).

  6. 6

    Pauleve, J., Dautreppe, D., Laugier, J. & Néel, L. J. Phys. 23, 841–843 (1962).

  7. 7

    Gros, Y. & Pauleve, J. J. Phys. 31, 459–470 (1970).

  8. 8

    Nord, G. L. Jr. & James, O.B. Proc. 9th Lunar Sci. Conf. 821–839 (1978).

  9. 9

    Edington, J. W. Practical Electron Microscopy in Materials Science (Van Nostrand, New York, 1976).

  10. 10

    Danon, J. et al. Nature 277, 283–284 (1979).

  11. 11

    Jago, R. A. Nature 279, 413–415 (1979).

Download references

Author information

Rights and permissions

Reprints and Permissions

About this article

Further reading

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.