Iron Substitution in Soil and Synthetic Anatase

U. Schwertmann, J. Friedl, G. Pfab and A. U. Gehring
Lehrstuhl für Bodenkunde, Technische Universität München, D-80350 Freising-Weihenstephan

Abstract: IronIII for TiIV substitution in the structure of pedogenic and synthetic anatase of up to Fe/(Ti+Fe) 0.1 mol/mol was indicated by an increase in unit cell size as measured by XRD line shifts. Mössbauer- and electron paramagnetic resonance spectra at both, 298 K and 4.2 K supported this by the presence of signals typical for octahedrally coordinated FeIII in a diamagnetic matrix. Charge compensation was achieved by structural OH, as indicated by FTIR bands at 3360 and 960 cm-1, which were absent in pure anatase and which disappeared on heating. The weight loss on heating amounted to ca. 0.5 mol H2O/mol Fe. At 600°C structural Fe was ejected, the unit cell size decreased to that of pure anatase, and pseudobrookite, Fe2TiO5, was formed.

Key Words: Anatase • Crystal chemistry • EPR • Fe substitution • FTIR • Mössbauer • OH—O-substitution • Pseudobrookite • TA • TEM • XRD

Clays and Clay Minerals; October 1995 v. 43; no. 5; p. 599-606; DOI: 10.1346/CCMN.1995.0430509
© 1995, The Clay Minerals Society
Clay Minerals Society (www.clays.org)