Coprecipitation Synthesis of Fe-doped ZnO Powders with Enhanced Microwave Absorption Properties

In this work, the Fe-doped ZnO powders have been synthesized by a facile chemical coprecipitation method. The structure, morphology and magnetic properties of the as-prepared powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectrum (EDS), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM). The results showed that the Fe ions were well incorporated into the crystal lattice of ZnO and had a valence state of +3. The magnetization curves indicated the Fe-doped ZnO presented the ferromagnetic behavior at room temperature. Moreover, the electromagnetic (EM) parameters and microwave absorption properties of Fe-doped ZnO/paraffin wax in the frequency range of 2-18 GHz were explored. The minimum reoflection loss reached -38.4 dB at 6.6 GHz, and the reflection loss less than -10.0 dB was 4.0 GHz (from 11.0 GHz to 15.0 GHz) with a thickness of only 2.5 mm. Significantly, the enhanced microwave absorption of the as-prepared powders could be achieved by doping with Fe3+ ions or varying the thickness of the absorbers. The mechanism of microwave absorption were attributed to the good impedance matching, the dielectric loss resulted from the crystal lattice defects and the magnetic loss originated from the natural resonance. It is believed that the Fe-doped ZnO powders could be used as potential microwave absorbers.