Effects of Samarium Oxide Addition on the Phase Composition, Microstructure, and Electrical Resistivity of Aluminum Nitride Ceramics

The phase composition, microstructure, and electrical resistivity of hot-pressed AlN ceramics with 0–4.8 wt% Sm₂O₃ additive were investigated. The phase composition was approximately consistent with that estimated from the Sm₂O₃–Al₂O₃ phase diagram using the amount of added Sm₂O₃ and oxygen content of the AlN raw material. When sintered at more than 1800°C, the AlN ceramics with 1.0–2.9 wt% Sm₂O₃ additive contained an Sm-β-alumina phase wetting the grain boundaries, and their electrical resistivity considerably decreased to 10¹⁰–10¹²Ω·cm. This resistivity decrease was caused by the continuity of the Sm-β-alumina phase with a resistivity lower than that of bulk AlN.