Structure and magnetic properties of Ni_xZn_1-xFe₂O₄ nanoparticles prepared through co-precipitation method

Nickel zinc ferrites, Ni_xZn_1-xFe₂O₄, nanoparticles have been synthesized using the chemical co-precipitation technique. Effects of synthesis conditions on the crystal structure, crystallite size, lattice parameter, microstructure and magnetic properties of the produced spinel ferrites were investigated by X-ray diffraction analysis (XRD), scanning electron microscope (SEM) and vibrating sample magnetometer (VSM). The results showed that a well crystalline single cubic structure of Ni_0.5Zn_0.5Fe₂O₄ phase was formed through precipitation precursors at pH 10 and annealed for 2 h at 1000 °C, using sodium carbonate to adjust the pH. With the use of NaOH to adjust the pH, mixture of Ni_0.5Zn_0.5Fe₂O₄ and Fe₂O₃ phases were obtained. However, the addition of hydrogen peroxide, to the sodium hydroxide during precipitation, improved the formation of the single phase of Ni-Zn spinel ferrites. Moreover, the addition of two types of surfactants found to enhance the formation of the spinel crystal structure of the ferrites. The change of the Ni molar ratio content (x) from 0.2 to 0.9 had strongly affected the properties of the formed ferrites powders. The lattice parameters found to decline gradually with increasing nickel content and the crystallite size was in the range between 27 and 155 nm. Maximum saturation magnetization (85.4 emu/g) was achieved for the prepared Ni_0.5Zn_0.5Fe₂O₄ phase; annealed at 1200 °C for 2 h using Na₂CO₃ as alkali.