Controllable phase transformation for enhancing electromagnetic wave attenuation in the SiBCN polymer-derived ceramics

Strong attenuation capability and good impedance matching are necessary conditions for high-performance electromagnetic wave (EMW) attenuation materials, which are difficult to balance in the polymer-derived ceramics (PDCs) preparation process. In this work, the dielectric loss phase and wave-transparent phase are simultaneously obtained in SiBCN ceramics, endowing a strong EMW absorbing capability. The results show that the transformation of Si 3 N 4 to SiC could be controlled to achieve coexistence in SiBCN ceramics. The Si 3 N 4 improves the impedance matching characteristics, while SiC and the corresponding heterogeneous interfaces enhance the polarization loss capability. Furthermore, the graphite strips construct a three-dimensional conductive network to improve the conductive loss capability. As a result, the minimum reflection loss reaches -54.24   dB at 15.04   GHz, and the effective absorption bandwidth is 7.48   GHz with a thickness of 1.72   mm, covering the whole Ku band. The excellent EMW absorption capability of SiBCN ceramics can be attributed to the synergistic function of Si 3 N 4 and SiC, which provides a novel strategy for the preparation of ultra-thin and strong EMW attenuating materials with broadband.