Effects of heat treatment on the properties of powder injection molded AlN ceramics

The effects of two different heat-treatment atmospheres, nitrogen atmosphere and reducing nitrogen atmosphere with carbon, on the properties of Y2O3-doped aluminum nitride (AlN) ceramics were investigated. The AlN powder as a raw material was synthesized by self-propagating high-temperature synthesis (SHS) and compacts were fabricated by employing powder injection molding technique. The polymer-wax binder consisted of 60 wt.% paraffin wax (PW), 35 wt.% polypropylene (PP), and 5 wt.% stearic acid (SA). After the removal of binder, specimens were sintered at 1850°C in nitrogen atmosphere under atmospheric pressure. To improve the thermal conductivity, sintered samples were reheated. The result reveals that the heat-treatment atmosphere has significant effect on the properties and secondary phase of AlN ceramics. The thermal conductivity and density of AlN ceramics reheated in nitrogen gas are 180 W·m−1·K−1 and 3.28 g·cm−3 and the secondary phase is yttrium aluminate. For the sample reheated in reducing nitrogen atmosphere with carbon, the thermal conductivity and density are 173 W·m−1·K−1 and 3.23 g·cm−3, respectively, and the secondary phase is YN.