The dielectric and microwave absorption properties of polymer-derived SiCN ceramics

The polymer-derived SiCN ceramics were synthesized at different annealing temperature (900 ∼ 1400 °C). The XRD, SEM, FT-IR, Raman and XPS were used to analyze the phase composition and microstructure. The result indicated that the crystallization degree and content of free carbon gradually improved with the increase of annealing temperature. The resistivity, dielectric and microwave absorption properties of the samples were studied at 2 ∼ 18 GHz. The resistivity decreased gradually as the annealing temperature rose. The dielectric constant of sample decreased with the increase of frequency in 1 ∼ 5 MHz. The existence of free carbon could improve the dielectric properties of polymer-derived SiCN ceramics at high frequency. The reflectance of the sample synthesized at 1100 °C was below −10 dB (> 90% absorption) in a wide frequency range of 6 ∼ 16 GHz and the maximum value of dielectric loss angle tangent was about 0.6 at 16 GHz.