AlN samples doped with sub-micron Y2O3 and CaO powders as sintering additives obtained using the micro hot-pressed (MHPed) sintering method in a MoSi2 heating element furnace were investigated. The minor amounts of secondary phases were identified as Al5Y3O12, CaYAl3O7, and CaAl4O7, which are related to the low sintering temperature as well as the removal of oxygen-related defects in the system. Relative densities of over 96% of the theoretical value were obtained after sintering at 1600 oC for 8 h, indicating that an adequate amount of additives and the use of the micro hot-pressed (MHPed) sintering process help improve the densification and thermal conductivity of AlN ceramics. The high thermal conductivity of 130Wm−1K−1 was attributed to the purification of the AlN lattice, the elimination of some secondary phases, and the grain boundary phase distribution.

Keywords: Aluminum nitride, Sub-micron, Micro hot-pressed, Thermal conductivity, MoSi2 heating element