Microwave-assisted solution combustion synthesis of Fe3O4 powders

Magnetite (Fe3O4) powders were synthesized by solution combustion method at different fuel to oxidant ratios phi = 0.5, 0.75, 1 and 1.5) using conventional and microwave ignition. The ignition method and fuel content affected the phase evolution, microstructure and magnetic properties of Fe3O4 powders as characterized by X-ray diffractometry, infrared spectroscopy, N-2 adsorption desorption, electron microscopy and vibrating sample magnetometry techniques. Single phase Fe3O4 powders were only obtained using conventional ignition at phi value of 1, while the impurity phases such as alpha-Fe3O4 and FeO together with Fe3O4 phase were formed by microwave ignition. The bulky microstructure of conventionally combusted powders with specific surface area of 71.5 m(2)/g was transformed to disintegrated structure (76.5 m(2)/g) by microwave heating. The microwave combusted powders showed the highest saturation magnetization of 86.5 emu/g at phi value of 0.5 and the lower coercivity than that of conventionally combusted powders at all phi values, due to their larger particles.