Effect of AlN addition on the thermal conductivity of pressureless sintered SiC ceramics

Dense silicon carbide ceramics with 0.5-10 wt% AlN additions were pressureless densified by two steps sintering using B₄C and C as sintering additives. The effects of AlN content on density, microstructure and thermal conductivity of SiC-AlN composites were investigated. SiC ceramics can be well densified in the presence of AlN. The phonon scattering mechanism and the Klemens-Callaway theory were used to calculate the thermal conductivity evolution of SiC ceramics result from the dissolved Al and N atoms. The main reason for the degradation of thermal conductivities is the point defect scattering dominated by the differences in size and interatomic forces between impurity and host atoms.