Structural and morphological characterization of FeCo 2O 4 and CoFe 2O 4 spinels prepared by a coprecipitation method

Abstract

Due to the importance of cation distribution in the physical properties of spinels, a structural and morphological study of the FeCo 2O 4 and CoFe 2O 4 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 CoFe 2O 4 was chemically heterogeneous. At 1170 K, a single homogeneous CoFe 2O 4 spinel is obtained (average grain size ≈1 μm, inversion degree λ≈0.76±0.02). FeCo 2O 4 could only be prepared by heating at ≈1170 K (average grain size ≈0.5 μm and λ approximately equal or slightly larger than 0.50, depending on heating time). At lower temperatures Co- and Fe-rich spinel phases are segregated.