Preparation and characterization of spinel nickel ferrite obtained by the soft mechanochemically assisted synthesis

Nickel ferrite, NiFe2O4 has been prepared by a soft mechanochemical route from mixture of (1) Ni(OH)2 and α-Fe2O3 and (2) Ni(OH)2 and Fe(OH)3 powders in a planetary ball mill for varying duration. Soft mechanochemical reaction leading to formation of the NiFe2O4 spinel phase was followed by X-ray diffraction, Raman and infrared spectroscopy, TGA, scanning and transmission microscopy. The spinel phase formation was first observed after 4 h of milling and its formation was completed after 25 h in the both cases. The synthesized NiFe2O4 ferrite has a nanocrystalline structure with a crystallite size of about 20 and 10 nm respectively for the cases (1) and (2). The final grain size in the system (1) is about twice as large as that in the system (2), what is a consequence of different reaction paths in these two processing routes. There are five Raman and four IR active modes. Mössbauer spectroscopy studies implied on the possible cation distribution between the tetrahedral and octahedral sites in formed NiFe2O4 spinel structure. We were able to estimate the degree of inversion at most 0.82 in the case (1) and 0.66 in the case (2).