Mechanochemically activated synthesis of nanostructured NiFe2O4

Powdery NiFe2O4 has been obtained by mechanothermal treatment. Nickel and iron hydroxides are used as initial compounds. For comparison the initial compounds are calcinated without mechanical treatment (samples obtained by direct heating). The characterization of the samples is carried out by XRD analysis and Mossbauer spectroscopy. It is established that single phase NiFe2O4 is formed after mechanical activation (5 h) and calcination at 773 K. The ferrite synthesized at this temperature contains a smaller quantity of Fe3+ ions in tetrahedral position (31%) than is the case of conventional nickel ferrite (50%). The number of tetrahedrally coordinated iron ions increases with enhancement of the synthesis temperature, approaching the distribution of the tetrahedral and octahedral positions typical of conventional NiFe2O4. The samples obtained by direct heating contain unreacted NiO and α-Fe2O3 even after calcinations at 1073 K.