Room Temperature Synthesis of Magnetite (Fe_3−δO₄) Nanoparticles by a Simple Reverse Co-Precipitation Method

Magnetite (Fe_3−δO₄) nanoparticles with the size less than 30 nm have been synthesized by using a simple reverse co-precipitation method at room temperature. During the process, ferrous sulfate (FeSO₄·7H₂O) powder was used as an iron precursor, and ammonium hydroxide (NH₄OH) as a precipitating agent. The experiment was carried out in ambient atmosphere without any surfactant added. In this method, the base solution for the precipitation process was adjusted to have a pH value suitable for the formation of the magnetite phase. The iron salt precursor was added into the solution during the synthesis by two different synthesis protocols. The phase, morphology and magnetic characteristic of differently synthesized magnetite particles were characterized by using an X-ray diffraction (XRD), transmission electron microscope (TEM) and vibrating sample magnetometer (VSM). The morphologies of the particles were spherical or irregular in shape depending on the synthesis protocol used. Magnetic measurement shows that the particles are ferromagnetic at room temperature with relatively high saturation magnetization and low hysteresis. The saturation magnetization and magnetic hysteresis of the particles varied with preparation reaction conditions and the resulting oxidation state of the particles.