Silicon carbide is widely used as an important structural material. It is known for its extreme hardness, high temperature antioxygenic properties and good tribological properties. Moreover, SiC is also an intrinsic semiconductor. SiC can react with A1N and form an extensive solid solution at temperatures between 1800 to 2100 deg C, and has excellent mechanical properties. However, in this article, we study the influence of the microstructure and the dielectric properties of SiC ceramics. SiC-AIN solid-solution ceramics were prepared by hot-pressed sintering using Y_2O_3 as the sintering additive. The size of SiC and AlN powders were 0.6 mu m and 1.06pm respectively. The content of A1N starting powders was 14vol percent. The hot-processing sintered SiC-AIN multiphase ceramics have reached high density at 1950 deg C in Ar atmosphere under 30MPa.The hot-processed ceramics were subjected to thermal treatments in a range of temperatures between 1100 deg C and 1600 C for 3hr. The grain size increased with the annealing temperature. X-ray diffraction profiles show that phase relationships. Scanning electron microscopy (SEM)) was used to determine fracture surface and the local compositions. Dielectric permittivities and dissipation factor of SiC-AIN composites were investigated with the varieties of annealing temperature and the content of A1N particles. Dielectric constants (epsilon) and Dielectric loss tangents (tan8) were measured within the microwave frequency range from 40Hz to 10MHz.
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