Crystallochemical Characterization of Magnetic Spinels Prepared from Aqueous Solution

Author Info

Stephen Mann, University of Bath
Nicholas H.C. Sparks, University of Bath
Suzanne B. Couling, University of Bath
Miranda C. Larcombe, University of Bath
Richard B. Frankel, California Polytechnic State University - San Luis ObispoFollow

Recommended Citation

Postprint version. Published in Journal of the Chemical Society. Faraday transactions, Volume 85, January 1, 1989, pages 3033-3044.

The definitive version is available at https://doi.org/10.1039/F19898503033.

Abstract

The crystallochemical characterization of magnetic spinels prepared from aqueous solution has been studied primarily by electron microscopy and ⁵⁷Fe Mossbauer spectroscopy. Two synthetic routes have been investigated : method 1 ; partial oxidation of Fe" solutions in the presence of NO; at 100 C , and method 2; reaction of hydrated Ferrr oxide (ferrihydrite) with Fe" ions at room temperature, pH = 7, 8 and 9. Both routes gave small (10-60 nm) irregular magnetite (Fe,O,) particles that were readily oxidised to maghemite (y-Fe,O,). The reaction proceeded via a green-rust intermediate and anions such as inorganic phosphate (Pi) and SO,,- reduced the rate of transformation. Spinel formation at room temperature was severely inhibited by Pi levels of 1 mol%, whereas 20-30 mol % Pi was required for retardation of crystallization at 100 "C. Intermediate levels (5-10 mol %) resulted in morphological enhancement of the octahedral crystal habit. A similar effect was observed in the presence of SO^2-₄ and at neutral pH in method 2.

Disciplines

Physics

Copyright

1989 Royal Society of Chemistry.