Dielectric and microwave-absorption properties of SiC nanoparticle/SiBCN composite ceramics

SiC nanoparticles with different contents (5–20 wt%) were mixed with liquid polyborosilazane. The compound was used to prepare SiC nanoparticle/polymer-derived SiBCN ceramics (SiC/PDCs-SiBCN). Thermal gravity tests (25–1400 °C) in air and helium atmosphere were used to investigate the thermal stability of SiC/PDCs-SiBCN. Dielectric and microwave-absorption properties of SiC/PDCs-SiBCN were determined at frequencies of 8.2–12.4 GHz by waveguide method. Results show that the addition of SiC nanoparticles increased the thermal stability of SiBCN ceramics. The permittivity, dielectric loss and absorption coefficient of ceramics increased as an elevated SiC content, resulting from the increase of carrier concentration. To understand the high-temperature dielectric property of SiC/PDCs-SiBCN, the permittivity of SiBCN ceramics with 15 wt% of SiC was measured at temperatures of 293–773 K. The composite ceramics were found to have a visible increase in the permittivity and dielectric loss, indicating their great potential as the high-temperature microwave absorption materials.