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Physics and Chemistry of Minerals

, Volume 25, Issue 5, pp 323–327 | Cite as

Quantitative determination of iron oxidation states in minerals using Fe L 2,3 -edge electron energy-loss near-edge structure spectroscopy

  • P. A. van Aken
  • B. Liebscher
  • V. J. Styrsa
ORIGINAL PAPER

Abstract 

The Fe L2,3-edge spectra for a range of natural minerals and synthetic solid solutions have been measured using the technique of parallel electron energy-loss spectroscopy (PEELS) recorded in a transmission electron microscope (TEM). The Fe L 2,3 -edges of the minerals are characterised by two white-line features and exhibit electron energy-loss near-edge structure (ELNES) characteristic of Fe valence state. For divalent iron, the Fe L 3 -edge spectra are dominated by a sharp peak (white-line) at ca. 707.8 eV, followed by a broader and less intense peak at ca. 710.5 eV. The ELNES on the Fe L 3 -edge of trivalent iron consists of a white-line with its maximum at ca. 709.5 eV and a preceeding peak at ca. 708.0 eV. Mineral solid solutions that contain both Fe2+ and Fe3+ exhibit an Fe L 3 -edge shape that is composed of Fe L 3 -edges from the respective Fe2+- and Fe3+-bearing end members. The integral Fe L 2,3 -edge white-line intensity ratios I(L 3 )/I(L 2 ) show clear differences for Fe2+ and Fe3+. We demonstrate the feasibility of quantification of the ferrous/ferric ratio in minerals by determining the integral Fe L 2,3 -edge white-line intensity ratios I(L 3 )/I(L 2 ) as a function of the ferric iron concentration resulting in an universal curve within the experimental errors. The application of the universal curve combined with the high spatial resolution using the PEELS/TEM allows the quantification of the ferric iron concentration on a scale down to 10 nm, which is illustrated from a sample of ilmenite containing hematite exsolution lamellae that shows different Fe L 2,3 -edge shapes consistent with variations in the Fe2+-Fe3+ ratio over distances of ca. 100 nm.

Keywords

Hematite Ilmenite Ferric Iron Trivalent Iron Universal Curve 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 1998

Authors and Affiliations

  • P. A. van Aken
    • 1
  • B. Liebscher
    • 2
  • V. J. Styrsa
    • 1
  1. 1.Institut für Mineralogie, Technische Hochschule Darmstadt, Schnittspahnstraße 9, D-64287 Darmstadt, GermanyDE
  2. 2.Institut für Mineralogie, Universität Frankfurt, Senckenberganlage 28, D-60054 Frankfurt, GermanyDE

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