Effects of the SmFeN content on the electromagnetic wave absorbing properties of sandwich-structured YSZ/SmFeN/YSZ composites

In this study, the thermal barrier material Yttria Stabilized Zirconia (YSZ) and the electromagnetic wave (EMW) absorbing agent samarium iron nitrogen (SmFeN) were used to prepare a YSZ/SmFeN/YSZ sandwich-structured composite. The YSZ/SmFeN interface was prepared perpendicular to the directions of EMWs. The EMW attenuation of the composites with different SmFeN contents and their mechanisms were studied using electromagnetic parameters, impedance matching, Cole–Cole circles, and minimum reflection loss (RL_min value). Dielectric loss was the dominant mechanism behind EMW attenuation for the composites. In addition, the dipole orientation of SmFeN and the presence of phase interface induced the dielectric loss. The mechanism of dipole orientation polarization was influenced by SmFeN content; the lesser the SmFeN content in the composite, the higher the ε $\prime$ (real part of dielectric coefficient). The frequency at which ε $\prime$ peaked shifted decreased with increasing SmFeN content. Higher dielectric losses were observed in the frequency band of 4.0–8.0 GHz. The EMW absorption rate showed that the optimum EMW absorption effect was achieved when the thickness ratio of YSZ:SmFeN:YSZ was 1:4:1 and the thickness is 3.325 mm. The corresponding RL_min was −35.3 dB and effective absorption bandwidth was 9.5 GHz (8.3–17.9 GHz).