Quantitative Determination of Aluminum-Substituted Goethite-Hematite Mixtures by Mössbauer Spectroscopy

D. D. Amarasiriwardena, E. DeGrave1, L. H. Bowen2 and S. B. Weed
Department of Chemistry
Department of Soil Science, North Carolina State University, Raleigh, North Carolina 27695
1 Permanent address: Laboratory for Magnetism, Proeftuinstraat 86, B-9000 Gent, Belgium.
2 To whom reprint requests should be sent.

Abstract: Mixtures of synthetic Al-substituted goethite (α-Fe0.814Al0.186OOH) and hematite (α-Fe1.658Al0.342O3) (75, 50, 25, 3% hematite by weight) were studied by Mössbauer spectroscopy to evaluate the use of that technique for quantitative analysis. Mössbauer spectra for these mixtures, obtained in the temperature range 12–130 K, were better fitted by a distribution of magnetic fields than by two magnetic sextets. Spectra at 80 K were equally as good as those from lower temperature to determine the hematitegoethite ratio. The recoil-free fractions of the individual components were about equal at any fixed temperature, but thickness effects caused as much as 30% error in the determination of the ratio of components in mixtures.

Key Words: Aluminum • Goethite • Hematite • Mössbauer spectroscopy • Quantitative mineralogy

Clays and Clay Minerals; June 1986 v. 34; no. 3; p. 250-256; DOI: 10.1346/CCMN.1986.0340304
© 1986, The Clay Minerals Society
Clay Minerals Society (www.clays.org)