Preparation of nickel ferrite from thermolysis of nickel tris(malonato)ferrate(III) heptahydrate precursor

The thermal decomposition of nickel tris(malonato)ferrate(III) heptahydrate precursor, Ni3[Fe(CH2C2O4)3]2·7H2O has been investigated from ambient temperature to 1073 K in static air atmosphere using various physico-chemical techniques, i.e. TG–DTG–DSC, XRD, Mossbauer and IR spectroscopy. The precursor undergoes dehydration and decomposition simultaneously to yield nickel malonate and iron(II)malonate intermediates at 513 K. At higher temperature (593 K) these intermediate species decompose to NiO and α-Fe2O3, respectively. Finally, nickel ferrite, NiFe2O4 has been obtained as a result of solid-state reaction between Fe2O3 and NiO at a temperature (673 K) much lower than that of the conventional ceramic method. SEM analysis of the final thermolysis product reveals the formation of nickel ferrite nanoparticles with an average particle size of 40 nm. Magnetic studies show that these particles possess a saturation magnetization and Curie temperature of 2970 G and 843 K, respectively. Lower magnitude of these parameters as compared to the bulk values may be attributed to the ultrafine nature of the ferrite particles.