Crystal structure and theoretical elastic property of two new ternary ceramics Hf3Al4C6 and Hf2Al4C5

Two new ternary aluminum carbides, Hf3Al4C6 and Hf2Al4C5, were identified and their crystal structure was determined by a combination of X-ray diffraction, Z-contrast scanning transmission electron microscopy and density-function calculations. Theoretical second-order elastic constants, bulk modulus, shear modulus and Young’s modulus of Hf3Al4C6 and Hf2Al4C5, as well as Hf3Al3C5, Hf2Al3C4, HfC and Al4C3, were calculated and compared. These new carbides show promisingly high elastic stiffness.