Synthesis and characterization of ternary layered i‐MAX (Mo _2/3 Y _1/3 ) ₂ AlC ceramics fabricated by spark plasma sintering

Abstract In this paper, the i‐MAX phase (Mo _2/3 Y _1/3 ) ₂ AlC ceramic with high purity of 98.29 wt% (1.13 wt% Y ₂ O ₃ and 0.58 wt% Mo ₂ C) and high relative density of 98.59% was successfully synthesized by spark plasma sintering (SPS) at 1500°C with the molar ratio of n (Mo): n (Y): n (Al): n (C) = 4:2:3.3:2.7. The positions of C atoms in the crystal of (Mo _2/3 Y _1/3 ) ₂ AlC were determined. Microstructure and physical and mechanical properties of (Mo _2/3 Y _1/3 ) ₂ AlC ceramic were systematically investigated. It was found that the obtained (Mo _2/3 Y _1/3 ) ₂ AlC ceramic had an average grain size of 32.1 ± 3.1 μm in length and 14.2 ± 1.7 μm in width. In terms of physical properties, the measured thermal expansion coefficient (TEC) of (Mo _2/3 Y _1/3 ) ₂ AlC was 8.99 × 10 ⁻⁶ K ⁻¹ , and the thermal capacity and thermal conductivity at room temperature were 0.43 J·g ⁻¹ ·K ⁻¹ and 13.75 W·m ⁻¹ ·K ⁻¹ , respectively. The room temperature electrical conductivity of (Mo _2/3 Y _1/3 ) ₂ AlC ceramic was measured to be 1.25 × 10 ⁶ Ω ⁻¹ ·m ⁻¹ . In terms of mechanical properties, Vickers hardness under 10 N load was measured as 10.54 ± 0.29 GPa, while flexural strength, fracture toughness, and compressive strength were determined as 260.08 ± 14.18 MPa, 4.51 ± 0.70 MPa·m ^1/2 , and 855 ± 62 MPa, respectively, indicating the promising structural applications.