Aluminium nitride by plasma spraying of an Al₂O₃-C-Sm₂O₃ system

Increasing demand for high performance ceramic dielectric substrate materials has led to the use of AIN due to its high thermal conductivity, low dielectric constant and co-efficient of thermal expansion (CTE) compatibility with that of silicon. This paper reports on a thermal plasma spraying process which enhanced the reactivity of an Al₂O₃-C-Sm₂O₃ system so that subsequent heating at 1400°C was sufficient to fully convert it to hexagonal AIN spherical particles with a particle size of about 2.45 μm. It was thought that the increase in reactivity was due both to the formation of the integrated composite powder by plasma spraying, which reduced the overall endothermic heat required for the nitridation reaction, and the liquid phase sintering effect of SmAlO₃ during the process.