Thermal conductivity of micro hot-pressed AlN ceramics fabricated using a conventional MoSi₂ heating element furnace

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 A1 ₅Y₃O₁₂, 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°C 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 130 Wm^-1'K^-1 was attributed to the purification of the AlN lattice, the elimination of some secondary phases, and the grain boundary phase distribution.