Synthesis, microstructure and properties of ternary layered i-MAX (Mo2/3M1/3)2AlC (M = Sc and Lu) ceramics fabricated by spark plasma sintering

Recently, a new i-MAX phase with in-plane chemical order has been discovered. In this study, the i-MAX phase (Mo2/3Sc1/3)2AlC and (Mo2/3Lu1/3)2AlC ceramics were synthesized by spark plasma sintering (SPS) with purity up to 96.45 wt% and 95.46 wt%, respectively. Relative densities were up to 98.29 % (M = Sc) and 98.23 % (M = Lu). Microstructure, physical and mechanical properties of (Mo2/3M1/3)2AlC (M = Sc and Lu) ceramics were systematically investigated. Grain sizes of (Mo2/3M1/3)2AlC (M = Sc and Lu) were also counted. The measured coefficients of thermal expansion (CTE) were 8.95 x 10-6 K-1 (M = Sc) and 8.97 x 10-6 K-1 (M = Lu), from 25 degrees C to 1200 degrees C. Regarding mechanical properties, the Vickers hardness of (Mo2/3Lu1/3)2AlC was much higher than that of (Mo2/3Sc1/3)2AlC, while the differences in flexural strength, fracture toughness and compressive strength were small. It indicates that both ceramics have good application prospects.