Enhanced microwave absorbing properties of Y₂O₃ modified PDC SiCN ceramics with heterogeneous amorphous interface

Polymer derived SiCN ceramics (PDC SiCN) are the key high-temperature matrix materials for structural and stealth integrated ceramic matrix composites (CMC). However, low crystallization degree and homogeneous microstructure of PDC SiCN ceramics results in the lack of effective microwave attenuation mechanism. Hence, a new kind of nonmagnetic metal oxide (Y₂O₃) was in-situ formed in SiCN ceramics to enhance the conductivity loss as well as the polarization loss. Y₂O₃ modified PDC SiCN ceramics (SiCN-Y₂O₃ ceramics) were fabricated by pyrolysis polysilazane with different Y(NO₃)₃ content at 900 ºC. For the SiCN-Y₂O₃ ceramic, Y₂O₃ nanoparticles were dispersed in SiCN ceramic uniformly forming a large number of Y₂O₃-SiCN heterogeneous amorphous interface, defects and dipole polarization to enhance its microwave absorbing properties. Due to the multiple polarization loss mechanism, SiCN-Y₂O₃ ceramic with 10 wt% Y(NO₃)₃ content achieved excellent microwave absorption performance at a wide thickness range with the microwave absorbing efficiency more than 90% in the whole X band, and the RC_min could reach − 50.2 dB at the thickness of 3.5 mm.