Preparation, microstructure and properties of reaction-bonded AlN ceramics

AlN ceramics were prepared via a reaction-bonding technique, using Al and AlN powders as the starting materials. The effects of processing parameters and CaO as an additive were investigated. An AlN ceramic sintered at 1800°C with 0.5 wt.% CaO is highly densified and its dielectric constant and dielectric loss tgδ are 9.4 and 0.002 at 1 MHz, respectively. Its electrical resistivity and Vickers hardness are 2.88×1012 Ω cm, 1210 kg/mm2, respectively.