Synthesis of aluminum nitride sintered bodies using the direct nitridation of Al compacts

For the purpose of simplifying processes and low impurities, the synthesis of aluminum nitride sintered bodies was tried using direct nitridation of aluminum compacts with 5 wt% of yttria in near-net shape, followed by sintering at 1900°C. To prevent changes in the compact shape, nitridation was performed at nominal temperatures below the melting point of Al, and under nitrogen pressures 0.5 MPa. After nitridation, the generated AlN compacts reached 70% of the theoretical density. Densities of 94% of the theoretical density were achieved by pressureless sintering at 1900°C for 8 h in nitrogen atmosphere, and the thermal conductivity was 155 W/mK. The effects of the oxygen content of AlN sintered body and the structure of the AlN compact on the thermal conductivity are discussed.