Hf3AlN: A Novel Layered Ternary Ceramic with Excellent Damage Tolerance

In this work, bulk Hf3AlN ceramic was synthesized by an in situ reaction/hot pressing method using Hf and AlN as initial materials. The reaction path during the synthesis process was investigated. Hf3AlN was found to form via the reaction of Hf and AlN above 1000 degrees C. Furthermore, physical and mechanical properties of Hf3AlN, such as electrical conductivity, flexural strength, and elastic moduli were also characterized. Similar to typical layered ternary ceramics Ti3SiC2 and Ti3AlC2, Hf3AlN possesses metallic conductivity and excellent damage tolerance, which is also the first one of this type that has ever been reported to crystallize in an orthorhombic structure. It is believed that a typical layered crystal structure and weak inter-layer bondings contribute to the damage tolerance of Hf3AlN. Moreover, the stiffness of Hf3AlN can sustain a temperature as high as 1450 degrees C, being 250 degrees C higher than that of Ti3AlC2, which renders it a promising high-temperature structural material.