Abstract
AlN ceramics were prepared with a dopant of Y2O3 under a reducing nitrogen atmosphere with carbon at 1900°C for 20 h and 100 h. These ceramics exhibited high thermal conductivity, 220 W/mK and 272 W/mK, respectively. The thermal conductivity value (272 W/mK) of the latter was equivalent to the experimental value of its single crystal (285 W/mK). The oxygen content of the sample was very low, 0.05 mass%. The microstructure was characterized by a high-resolution transmission electron microscope (HR-TEM). The result showed that the former AlN ceramics possessed crystalline Y2O3 and an amorphous intergranular film. The intergranular phase decreased during the isothermal hold period by the migration of a liquid phase that consisted of Y2O3, Al2O3, and AlN. The liquid phase composition was maintained during the sintering process as an amorphous thin film.
