Dielectric properties of Si3N4–SiCN composite ceramics in X-band |
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Authors: | Quan Li Xiaowei Yin Liyun Feng |
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Affiliation: | Science and Technology on Thermostructural Composite Materials Laboratory, Northwestern Polytechnical University, Xi’an 710072, China |
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Abstract: | Si3N4–SiCN composite ceramics were successfully fabricated through precursor infiltration pyrolysis (PIP) method using polysilazane as precursor and porous Si3N4 as preform. After annealed at temperatures varying from 900 °C to 1400 °C, the phase composition of SiCN ceramics, electrical conductivity and dielectric properties of Si3N4–SiCN composite ceramics over the frequency range of 8.2–12.4 GHz (X-band) were investigated. With the increase of annealing temperature, the content of amorphous SiCN decreases and that of N-doped SiC nano-crystals increases, which leads to the increase of electrical conductivity. After annealed at 1400 °C, the average real and imaginary permittivities of Si3N4–SiCN composite ceramics are increased from 3.7 and 4.68 × 10?3 to 8.9 and 1.8, respectively. The permittivities of Si3N4–SiCN composite ceramics show a typical ternary polarization relaxation, which are ascribed to the electric dipole and grain boundary relaxation of N-doped SiC nano-crystals, and dielectric polarization relaxation of the in situ formed graphite. The Si3N4–SiCN composite ceramics exhibit a promising prospect as microwave absorbing materials. |
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