Nickel ferrite is one of very important material, which is suitable for using in computer peripherals, telecommunications equipments, permanent magnets, electronic and microwave devices. Thus, the study of the behavior of NiFe 2 O 4 in reducing atmosphere is very important. NiFe 2 O 4 is prepared by mixing chemically pure powders of Fe 2 O 3 and NiO in stoichiometric ratios then pressed at 250 kg/cm 2 into cylindrical form of compacts before being fired at 1000, 1100 and 1200 8C for 10 h.
The characteristic of the prepared nickel ferrite have been studied using X-ray diffraction analysis technique, reflected light microscope and porosity measurements. The behavior of nickel ferrite in hydrogen atmosphere at 900-1100 8C has been studied using thermogravimetric techniques. The reduction of NiFe 2 O 4 is not found to proceed to completion at any firing or reduction temperature. The reduction proceeds via a topochemical mode. At firing temperatures 1000 and 1100 8C, the rate is controlled initially by the combined gaseous diffusion interfacial chemical reaction mechanism while at the final stages, the interfacial chemical reaction is predominantly the rate-controlling mechanism. At 1200 8C, initially the rate controlling is the interfacial chemical reaction mechanism while the solid-state diffusion is rate-controlling mechanisms at the final stages.