Influences of Precursors Molar Ratio and Basic Agent on Processing of Nickel–Zinc Ferrite Nanopowders by a Sol-Gel Auto-Combustion Method

In the present investigation, nickel-zinc ferrite nanocrystalline powder has been prepared by a sol-gel auto-combustion technique using a gel including citric acid as a reductant and nitrates as oxidants. The results showed that the nitrate citrate gels exhibit a self- propagating behavior after ignition in air. The effects of Fe/(Ni, Zn) molar ratio and the kind of the basic agent on the thermal decomposition of the gels, and phase constitution, crystallite size, and morphology of the resultant powders were investigated by differential thermal analysis, thermo gravimetric analysis, X-ray diffraction, and transmission electron microscopy techniques. The results also revealed that in the presence of ammonia as a pH adjusting agent and Fe/(Ni, Zn) molar ratio of 2, the smallest crystallite size of nickel-zinc ferrite as 27 nm could be obtained directly after auto-combustion without the postcalcination process.