Evaluation of NiFe2O4 ferrite nanocrystalline powder synthesized by a sol-gel auto-combustion method

Nanocrystalline NiFe2O4 ferrite powder was prepared by a sol-gel auto-combustion method from metal nitrates and citric acid. The combustion process is an oxidation-reduction reaction in which the NO3- ion is oxidant and the carboxyl group is reductant. The thermal analysis of nitrate-citrate gels and the phase evolution of as-burnt powder with the different ratios of Fe/Ni and calcined powder were investigated by DTA/TG and XRD techniques respectively. SEM and Hysteresigraph were also used to characterize the microstructure and magnetic properties of the products. The results revealed that the nitrate-citrate gel exhibits a self-propagating combustion behavior. By using this novel auto-combustion method, NiFe2O4 ferrite powder was obtained with crystallite size of 20-40 nm and suitable soft magnetic properties. (c) 2007 Elsevier B.V. All rights reserved.