Control of hematite nanoparticle size and shape by the chemical precipitation method

Hematite (α-Fe2O3) nanoparticles were synthesized from the ferrihydrite precursor via a simple chemical precipitation method with trace amounts of Fe(II) as the catalyst under nitrogen atmosphere. The characteristic of the synthesized hematite particles were evaluated by XRD, FT-IR, and FE-SEM. The magnetic and electrical properties were studied by a vibrating sample magnetometer (VSM) and an electrometer, respectively. The synthesized products were of a single phase of the hexagonal structure hematite without any other impurities. The physical morphology of the synthesized hematite appears to be composed of a large number of very small particles appearing as the “raspberry shape”. The particle size of the synthesized hematite can be successfully controlled at 50–150 nm, appearing as three different morphologies: the spherical-like, the cubic-like, and the ellipsoidal shape, through adjusting the synthesis conditions. The smallest particle possesses the highest electrical conductivity of 5.2 × 10− 3 s/cm. On the other hand, the largest particle exhibits weak ferromagnetism and the highest saturation magnetization (Ms) of 1.94 emu/g, is higher than that of the smaller particle, which possesses the super-paramagnetic behavior. Furthermore, the different particle shapes are shown here to critically affect the electrical and magnetic properties of the nanoparticles.