Abstract
The millimeter-wave sintering of aluminum nitride added with various rare-earth oxides was performed under nitrogen atmosphere. Sinterability of aluminum nitride depended on species of rare-earth oxide, and sintering temperature decreased with decreasing the ionic radius of rare-earth. Full densification over 96 %T.D. was attained at 1600°C for 20 min in the Yb2O3-added aluminum nitride sintered by millimeter-wave heating. The main factor for the decrease of sintering temperature was attributed to the species of complex oxide phases, formed between rareearth oxide and aluminum oxides on the outermost surface of aluminum nitride powders. It was also indicated that coexistence of two kinds of complex oxide phases was advantageous to the decrease of sintering temperature in millimeter-wave sintering. Thermal conductivity also changed with added sintering aid, though large dependence was not observed. The highest thermal conductivity of 190 W/(m⋅K) was obtained in the Dy2O3-added aluminum nitride sintered at 1800°C for 60 min. It is considered that the thermal conductivity depends on relative density of sintered aluminum nitride.
