| 摘要 |
The invention concerns solid solutions of oxides of iron and of a divalent metal other than cobalt Co2+ or, alternatively, of iron and of more than one divalent metal, including cobalt. Besides Co, the divalent metals may be Ni, Cu, Mn, Zn, Mg and Cd. Such solutions are prepared by precipitating a mixed oxalate containing iron and the other divalent metal or metals desired. This mixed oxalate is decomposed by heating it in open air at a progressively increasing temperature until carbon is eliminated but without forming rhomboedric oxide alpha -Fe2O3. The pyrolyzed product is treated by hydrogen and steam at an elevated temperature to obtain a substituted magnetite, and this magnetite is oxidized in air at such a temperature as to avoid formation of alpha -Fe2O3.
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