Spraying of Aluminum Nitride-Alumina-Yttria Mixtures in Nitrogen

This study investigates the feasibility of spraying aluminum nitride-alumina-yttria mixtures in a nitrogen plasma ambient. Coatings consisting of h-AlN, c-AlN, Al₅O₆N, and γ-Al₂O₃ with small amounts of α-Al₂O₃ and aluminum-yttrium oxide phases were produced. Although using the Y₂O₃ additives significantly affected the process and microstructure, it did not achieve the high thermal conductivity desired in as-sprayed coatings. However, a high thermal conductivity (>90 W/m·K) AlN coating was fabricated by increasing the AlN content and enhancing sintering during heat treatment.