Sintering of aluminum-nitride in a microwave induced plasma

Abstract

The sintering of aluminum nitride in a microwave induced plasma was investigated. The plasma furnace consisted of a quartz tube inserted into a waveguide connected to a 2450 MHz microwave generator. After evacuating the tube to about 1.33 mbar, nitrogen gas was introduced, generating a steady plasma. Processing parameters such as gas pressure, power level, and time were optimized to yield maximum densification of aluminum nitride. Sintering of pure and doped AlN compacts was performed in the nitrogen plasma at temperatures up to 2000 S C. Undoped specimens reached densities of only 81% theoretical, while densities in excess of 95% theoretical were achieved for yttria doped specimens in less than 15 minutes. Microstructural investigations revealed a smaller grain size in the plasma sintered specimens (about 2μ) than are present in conventionally sintered AlN (about 8μ).