High temperature dielectric and microwave absorption properties of polymer derived sicn ceramic in X band

Polymer derived SiCN ceramic (PDC-SiCN) composed of SiC and Si₃N₄ was obtained through pyrolysis of a kind of polysilazane at 1700 °C in N₂. The high temperature relative complex permittivities of PDC-SiCN were measured at temperatures from room temperature to 600 °C in the X band (8.2-12.4 GHz). The average real permittivity, imaginary permittivity and loss tangent of PDC-SiCN were 12.2, 5.8 and 0.47 at room temperature, and increased to 14.4, 9.3 and 0.64, respectively. The microwave absorption property of PDC-SiCN was calculated using metal back-panel model. The average reflectivity of sample in X band with sample thickness o f 2.05 mm at room temperature was -12.8 dB, and increased to -8.6 dB at 600 °C. The decrease of the microwave absorption property was attributed to the impedance mismatch between air and sample with the increasing temperatures.