Synthesis and characterization of high entropy (TiVNbTaM)₂AlC (M = Zr, Hf) ceramics

The high-entropy design of MAX phases is expected to confer superior properties, but its study was hindered by the complex synthesis method and limited purity of samples. In this work, two noteworthy types of high-entropy MAX phase structural ceramics, high-entropy (TiVNbTaM)₂AlC (M = Zr, Hf), were designed and prepared by the in-situ synthesis using spark plasma sintering (SPS). The microstructure and lattice parameters of sintered samples were determined. Compared with the single-component MAX phases, the highly pure high-entropy (TiVNbTaZr)₂AlC sample had good physical and mechanical properties, including electrical conductivity of 0.96×10⁶ Ω⁻¹·m⁻¹, thermal expansion coefficient of 3.65×10⁻⁶ K⁻¹, thermal conductivity of 8.98 W·m⁻¹·K⁻¹, Vickers hardness of 9.80 GPa, flexural strength of 507 MPa, fracture toughness of 5.62 MPa·m^1/2, and compressive strength of 1364 MPa, which exhibited the remarkable hardening-strengthening effect.