Effects of Behaviors of Aluminum Nitride Ceramics with Rare Earth Oxide Additives

The effects of three types of additives, Y₂O₃, Nd₂O₃ and Er₂O₃ on the behaviors of AlN ceramics were investigated. The experimental results showed that the sintering temperature could be decreased and the mechanical behavior could be improved by adding rare earth oxide in AlN ceramics. The highest strength and fracture toughness of AlN ceramics with 2% Y₂O₃ addition were 311 MPa and 3.5 MPa·m^1/2, respectively. Second phase of AlN ceramics with Y₂O₃ addition was identified as Y₃Al₅O₁₂ formed by the reaction with Al₂O₃, meanwhile that with Nd₂O₃ was identified as NdAlO₃. The fracture behavior of AlN ceramics with Y₂O₃ and Nd₂O₃ were a mixed mode of transgranular fracture and intergranular fracture. Because of the high evaporation rates of Er₂O₃ (1.2 × 10^-5 g·cm^-2), no aluminium erbium oxide was found in the AlN ceramics doped with Er₂O₃. So the dielectric loss tanger(tanδ) and thermal conductivity of AlN ceramics doped with Er₂O₃ were best.