Electrical, dielectric and microwave-absorption properties of polymer derived SiC ceramics in X band

• The porous SiC ceramics were fabricated by pyrolysis of a polycarbosilane precursor.
• The high temperature direct-current electrical conductivity and dielectric properties at X band were investigated.
• The relative complex permittivity of SiC ceramics increase with increase of annealing temperature.
• Porous SiC ceramics show good microwave absorption properties.

Porous silicon carbide ceramics were successfully fabricated by pyrolysis of a polycarbosilane precursor. The direct-current electrical conductivity, dielectric and microwave absorption properties over the frequency range of 8.2–12.4 GHz (X band) were investigated. Polymer derived silicon carbide is composed of SiC nano-crystals and free carbon nanodomains. The high-temperature direct-current conductivities of samples indicate the transformation of amorphous semiconductor into polycrystalline semiconductor with the increase of the annealing temperature. After annealed at 1500 °C, the real permittivity, imaginary permittivity and the loss tangent increase from 3.6, 0.17 and 0.05 to 8.49, 10.01 and 1.18, respectively. The increases of the relative complex permittivity and loss tangent are ascribed to the appearance of SiC nano-crystals and free carbon nanodomains. The average reflectivity of the polymer derived SiC ceramics annealed at 1400 °C is −9.9 dB, which exhibits a promising prospect as microwave absorbing materials.