Synthesis and electromagnetic absorption properties of CeO2@Fe composites with core-shell structure

Core-shell structured CeO2@Fe composites composed of a dielectric CeO2 core and ferromagnetic Fe shell were synthesized via a metal organic chemical vapor deposition (MOCVD) method. The phase structure, morphology, magnetic, and electromagnetic (EM) properties of the composites were characterized with modern measurement techniques. According to the results, the rough alpha-Fe shell is homogeneously deposited on the CeO2 surface. The saturation magnetization (M-s) and coercivity (H-c) of the CeO2@Fe composites are 45.1 emu/g and 274.3 Oe, respectively. The EM properties of the composites containing 60, 70, and 80 wt% CeO2@Fe and paraffin wax (PW) were investigated in the frequency range 2-18 GHz. The CeO2@Fe-PW composite with 70 wt% CeO2@Fe exhibits a minimal reflection loss (RL) of -17 dB at 9.6 GHz (thickness of 2.54 mm). The composite with 80 wt% CeO2@Fe shows a broad effective absorption bandwidth (RL <= -10 dB) at 4.24 GHz (thickness of 1.24 mm) and can be exploited for practical applications at 3.12-18.0 GHz by tuning its thickness from 0.97 to 4.0 mm. The excellent microwave absorption performance of the composites is attributed to the synergistic effects of a dielectric loss due to Debye relaxation and interface polarization and a magnetic loss due to natural resonances and exchange resonances. Moreover, the balance between the impedance matching and attenuation constants are benefits for the microwave absorption.