Microwave Assisted Iron Oxide Nanoparticles—Structural and Magnetic Properties

Microwave energy is used as an alternative source of high temperature treatment for synthesis and sintering. Till 1990s, the main focus was on the thermal effects caused by microwave heating. After 1990s reports began to emerge on the effects called microwave effects, including changes in material´s structure and so on. We here report the effects of microwave assisted sol-gel method on structural and magnetic properties of iron oxide nanoparticles (NPs). Microwave power (MP) is varied as 136, 264, 440, 616, and 800 W. The MPs used in this paper are among the lowest for the synthesis of NPs. X-ray diffractometer result of NPs with 136-W MP shows amorphous behavior with paramagnetic properties. Magnetite NPs are observed with MPs of 264-440 W. Magnetite phase tends to transform to maghemite phase with the appearance of characteristic (310) peak at MPs of 616-800 W. Scanning electron microscope results show NPs with diameter ~20 nm for MPs of 264 and 440 W. Relatively larger diameters ~50 nm are observed with MPs of 616 and 800 W. Variations in phase and size of iron oxide NPs strongly affect magnetic properties from superparamagnetic to ferromagnetic. It is observed that microwave assisted synthesis can be fast, low cost, and low energy consumption method to synthesize NPs with uniform shape and size distribution along with strengthened magnetic properties as compared with the conventional high-temperature annealing process.