MAX phase solid solutions physical and mechanical properties may be tuned via changes in composition, giving them a range of possible technical applications. In the present study, we extend the MAX phase family by synthesizing (Zr 1Àx Ti x ) 3 AlC 2 quaternary MAX phases and investigating their mechanical properties using density functional theory (DFT). The experimentally determined lattice parameters are in good agreement with the lattice parameters derived by DFT and deviate <0.5% from Vegard's law. Ti 3 AlC 2 has a higher Vickers hardness as compared to Zr 3 AlC 2 , in agreement with the available experimental data. The first (n=1) and second (n=2) members of the family are known as the 211 and 312 MAX phases respectively. A feature of them is the highly symmetric unit cell with atomic layers stacked along the c-direction. Numerous MAX phases were synthesized that shared these metallic and ceramic properties (good machinability, high melting temperature, high thermal shock resistance, high elastic stiffness, high thermal, and electrical conductivity), effectively motivating their technological application. [2][3][4][5] The key for the metallic and ceramic properties is the structure that consists of the stacking of M n+1 X n "ceramic" layer(s) interleaved by an A "metallic" layer.
2-5Ti-based MAX phases such as Ti 3 AlC 2 are of significant technical interest as they have excellent properties combined with a strong oxidation resistance in air due to formation of a passivating Al 2 O 3 outer layer.6 Related MAX phases have been investigated as candidate materials for passive safety protection of nuclear fuel cladding