Hydrothermal synthesis and microwave absorption properties of Fe₃O₄@SnO₂ core–shell structured microspheres

Fe₃O₄@SnO₂ core–shell structured microspheres have been designed and synthesized by a simple hydrothermal method. The transmission electron microscopy and scanning electron microscopy characterization results indicate that SnO₂ nanoparticles were successfully grown on the surface of Fe₃O₄ microspheres with different sizes. The X-ray diffractograms show that the nanocomposites are composed of cubic Fe₃O₄ and tetragonal SnO₂. The magnetic hysteresis measurements reveal the ferromagnetic behavior of the nanocomposites at room temperature. Considering that both Fe₃O₄ and SnO₂ are good microwave absorption materials, we have investigated the microwave absorption properties by a vector network analyzer between 2 and 18 GHz at room temperature. The electromagnetic data demonstrate that the as-synthesized Fe₃O₄@SnO₂ microspheres exhibit extraordinary microwave absorption properties, which may result from the proper electromagnetic match and interface polarization between the Fe₃O₄ cores and SnO₂ shells. Moreover, a possible formation mechanism of Fe₃O₄@SnO₂ microspheres based on the hydrothermal method was also proposed.