2274.     MICHEL, A., AND POUILLARD, E.  [New Family of Cubic Iron Sesquioxides.]  Compt. rend., vol. 228, 1949, pp. 680-681; Bull. soc. chim. France, 1949, p. 152; Chem. Abs., vol. 43, 1949, p. 8934.

        Mixed crystals of cubic (Fe_1-xAl_x)₂O₃ were obtained by oxidation of magnetite, x(Al₂O₃) (1-x)Fe₂O₃.FeO, in which Fe⁺⁺⁺ ions are partly substituted by Al⁺⁺⁺ ions.  The limit of solution is near to 10% Al₂O₃ at room temperature.  The parameter of the lattice decreases from 8.324 Å. for cubic Fe₂O₃ to the value 8.20 Å. continuously.  The solubility of Al₂O₃ increases at higher temperature.  The content of Al₂O₃ stabilizes the cubic form.  The temperature of quick transformation from the cubic form into the rhombohedral form is 200° for pure Fe₂O₃, 610° for the substitution x=0.03, and 650° for the substitution x=0.07.  A stabilized cubic mixture with 32% Al₂O₃ was obtained by quenching from 600°; its Curie point was 410°.  No modification in the stability of cubic Fe₂O₃ was obtained by Cr₂O₃, since it is insoluble in Fe₂O₃.