High temperature stability of maghemite (γ‐Fe2O3)
- 1 March 1984
- journal article
- Published by American Geophysical Union (AGU) in Geophysical Research Letters
- Vol. 11 (3) , 161-164
- https://doi.org/10.1029/gl011i003p00161
Abstract
The temperature stability of acicular maghemite (γ‐Fe2O3) was studied between 20°C and 600°C by x‐ray diffraction and magnetic measurements. Synthetic monodomain maghemite was found to be stable with respect to hematite (α‐Fe2O3) at temperatures as high as 500°C, inverting to α‐Fe2O3 between 510‐660°C. However, a complete inversion of the γ to α form for the sample was not achieved even at 660°C, the final product was a two‐phase mixture, with 65% of the original γ‐Fe2O3 unchanged. Two conclusions are made: (a) the absence of maghemite in a natural sample cannot be proven if heating has been restricted to moderate temperatures (300°‐400°C) and (b) the true Curie point of pure maghemite is close to 645°C.Keywords
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