High infrared emissivity of SiC-AlN ceramics at room temperature

SiC-AlN ceramics were fabricated by pressureless sintering with B4C-C as sintering additives. The effects of AlN contents on infrared emissivity, thermal conductivity and electrical properties of SiC ceramics were investigated. The improvement of total emissivity is slight before 3 wt%AlN, but impressive after 3 wt%AlN. The significant increase of the emissivity for AlN content higher than 3 wt% could be explained via DFT calculation, that the impurity energy level formed by N atom doping into 4H-SiC and the lattice distortion are mainly responsible for it. Besides, the highest total emissivity is 0.775 when the content of AlN is 5 wt%. Additionally, more AlN solid solution results in a decrease in thermal conductivity and an enhancement in electrical resistivity. There is always a compromise among the three properties of SiC-AlN ceramics.