Solid-state reaction synthesis of NiFe2O4 nanoparticles by optimizing the synthetic conditions

Abstract

Nickel ferrite (NiFe2O4) nanoparticles were synthesized via solid-state reaction. The precursors obtained by grinding the mixture of FeSO4·7H2O, NiSO4·6H2O, NaOH and dispersant (NaCl) sufficiently at room temperature were calcined under various synthetic conditions in order to get NiFe2O4 spinel nanoparticles. The effects of the synthetic parameters, namely preparation technique, dispersant content, calcination temperature and heat preservation time, on particle size and morphology have been investigated in detail to find the optimized parameters. X-ray diffraction (XRD), thermogravimetry (TG) and differential thermal analysis (DTA), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) were employed to characterize the precursors and as-synthesized particles. The results indicate that structural morphology varies between needle and sphere with changing preparation technique. Proper content of NaCl as a dispersant is beneficial to obtain uniform particles with a narrow size distribution. The particle morphology changes gradually from sphere to polygon with the increase in calcination temperature. Grain growth is enhanced by prolonging heat preservation time. Room temperature magnetization results reveal a ferromagnetic behavior of the as-synthesized NiFe2O4 nanoparticles. The saturation magnetization is enhanced with the increase in grain size for less surface effect. The coercivity is decreased for larger grain size because of magnetization reversal. The solid-state reaction technique is considered to be a convenient, inexpensive and effective preparation method of NiFe2O4 in high yield.