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

Hematite (alpha-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 x 10(-3) s/cm. On the other hand, the largest particle exhibits weak ferromagnetism and the highest saturation magnetization (M-s) 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. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.