Structural and morphological characterization of FeCo2O4 and CoFe2O4 spinels prepared by a coprecipitation method

Due to the importance of cation distribution in the physical properties of spinels, a structural and morphological study of the FeCo2O4 and CoFe2O4 spinels prepared by a low-temperature coprecipitation method has been undertaken. Only spinel phases are observed after annealing at 570 K. However, up to 770 K the sample with global composition CoFe2O4 was chemically heterogeneous. At 1170 K, a single homogeneous CoFe2O4 spinel is obtained (average grain size approximate to 1 mum, inversion degree lambda approximate to 0.76 +/- 0.02). FeCo2O4 could only be prepared by heating at approximate to 1170 K (average grain size approximate to 0.5 pm and; lambda approximately equal or slightly larger than 0.50, depending on heating time). At lower temperatures Co- and Fe-rich spinel phases are segregated. (C) 2003 Editions scientifiques et medicales Elsevier SAS. All rights reserved.