Construction of multiple heterogeneous interface and its effect on microwave absorption of SiBCN ceramics

Iron-containing siliconboron carbonitride (SiBCN) ceramics with multiple heterogeneous interfaces were fabricated using the microstructural design and polymer-derived ceramics (PDC) approach. The characterization results revealed the in-situ generation of nanocrystals, including graphite, belt-like silicon nitride (Si3N4), and silicon carbide (SiC) whiskers, in amorphous SiBCN matrix after annealing. At the same time, these dielectric lossy phases successfully constructed multiple heterogeneous interfaces and three-dimensional network structures. Consequently, the conductivity of the ceramics increased from 4.49 x 10(-9) (annealed at 800 degrees C) to 0.67 x 10(-4) S cm(-1) (annealed at 1600 degrees C). The real part of permittivity improved from 4.57-3.36 (annealed at 800 degrees C) to 10.90-8.38 (annealed at 1600 degrees C) in the frequency range of 2-18 GHz. The formation of multiple heterogeneous interfaces caused interfacial polarization and increased the multiple relaxations, which ultimately led to a superior microwave absorption property with a minimum reflection loss (RLmin) of -34.28 dB and an effective absorption bandwidth (EAB) of 3.76 GHz (8.64-12.4 GHz).