Low-temperature sintering of high-density aluminium nitride ceramics without additives at high pressure

High-density AlN ceramics were fabricated without additives under high pressure (3.15–4.95 GPa) at a low temperature (1300 °C), which is 300–500 °C lower than that for conventional liquid-phase sintering, in a cubic anvil high-pressure and high-temperature apparatus. The relative density of pure AlN ceramics is 94.92% at 1300 °C and 4.75 GPa for 50 min. Grain boundary phases were found in the neck area between AlN grains, indicating that grain growth by solution–precipitation must play some role.