Microwave-assisted solution synthesis, microwave sintering and magnetic properties of cobalt ferrite

A simple, soft, and fast microwave-assisted hydrothermal method was used for the preparation of nanocrystalline cobalt ferrite powders from commercially-available Fe(NO3)3∙9H2O, Co(NO3)2∙6H2O, ammonium hydroxide, and tetrapropylammonium hydroxide (TPAH). The synthesis was conducted in a sealed-vessel microwave reactor specifically designed for synthetic applications, and the resulting products were characterized by XRD, FE-SEM, TEM, and HR-TEM. After a systematic study of the influence of the microwave variables (temperature, reaction time and nature of the bases), highly crystalline CoFe2O4 nanoparticles with a high uniformity in morphology and size, were directly obtained by heating at 130 °C for 20 min using the base TPAH. Dense ceramics of cobalt ferrite were prepared by non-conventional, microwave sintering of synthesized nanopowders at temperatures of 850-900 °C. The magnetic properties of both the nanopowders and the sintered specimens were determined in order to establish their feasibility as a permanent magnet.