Microwave sintering of a combustion synthesized AIN powder

We report our preliminary study on microwave sintering of a combustion synthesized AIN powder. The combustion synthesis method was previously developed by Chung et al. at National Cheng Kung University, and is characterized by simple processing, fast production, low cost, high product purity, and being capable of mass production. The AIN product obtained from this synthesis method was ground to have average particle sizes of 0.9μm (AIN-1) and 3.0 μm (AIN-2) for sintering experiments. Yttrium oxide was added to the AIN powder as sintering aid. The microwave sintering experiments were carried out at the Microwave Processing and Engineering Center in the Pennsylvania State University. The samples were sintered by microwave at 2.45 GHz in a multi-mode cavity. The power used ranged from 200W to 1 kW, and the sintering temperature ranged from 1600°C to 2000°C. The AIN-1 powder was sintered to ∼99% of theoretical density at a sintering temperature of 1800°C with a soaking time of 30 min and a Y₂O₃ content of 3-5 wt%. The AIN-2 powder was less sinterable than AIN-1 and 97.3% of theoretical density was obtained at a sintering temperature of 2000°C with a soaking time of 30 min and a Y₂O₃ content of 5 wt%. The thermal conductivities reached 122 and 132 W/m K for the specimens made from AIN-1 and AIN-2, respectively, when 5 wt% of Y₂O₃ was added. Effects of several important parameters on the thermal conductivity were discussed.