Study on enhanced microwave absorption characteristics of annealed Fe3O4

Fe3O4 was synthesized by the hydrothermal method in one step. The grain size, morphology, and microwave absorption performances were modified effectively by heat treatment in a vacuum environment at different temperatures. Compared with the Fe3O4 before annealing, the minimum reflection loss value of Fe3O4 after annealing at 850 degrees C reaches - 27.5 dB at a thickness of 1.6 mm, with the effective absorption band reaching 5.68 GHz (10.32 GHz to 16 GHz). This result is due to the emergence of the second-phase Fe2O3 in Fe3O4 after annealing at 850 degrees C. The interfacial coupling between Fe3O4 and Fe2O3 leads to additional polarization. Moreover, the considerable absorption bandwidth resulted from better impedance matching and excellent attenuation performance. Therefore, it has broad application prospects as a microwave absorber.