Predictions of the structures and properties of the substituted layered ternary compound series (Zr_1−xT_x)₃Al₃C₅ (T  =  Hf, Nb, and V) through first-principles studies

The (Zr_1−xT_x)₃Al₃C₅ (T  =  Hf, Nb, and V) series can be potential candidates to extend the domain of MAX phases. In this work, the structures and properties of (Zr_1−xT_x)₃Al₃C₅ (T  =  Hf, Nb, and V) are studied using first-principles calculations. The obtained structural parameters are in good accordance with previously reported data in the literature. Based on the phase stability investigations, the potentially stable layered (Zr_1−xT_x)₃Al₃C₅ (T  =  Hf, Nb, and V) solid solutions are proposed, which confirms that Zr₃Al₃C₅ and Hf₃Al₃C₅ can be synthesized. The substitution, especially with group VB transitional metals, endows layered (Zr_1−xT_x)₃Al₃C₅ series with greatly enhanced mechanical and thermal properties. It is indicated that the bulk modulus B of all the three systems increase with increasing substitution concentration x. A significant increase in the ratio of bulk modulus to shear modulus, B/G, is found with increasing V concentration, which corresponds to the improved ductility. Moreover, solid solutions with V substitution, (Zr_1−xV_x)₃Al₃C₅, yield a larger effect on thermal conductivity with respect to x, indicating flexible modulation of the thermal conductivity of (Zr_1−xV_x)₃Al₃C₅ by V substitution can be achieved, which may promote them as promising coating materials. The intrinsic mechanism involved in the enhancements of the mechanical and thermal properties were elucidated through thorough electronic band structure analysis. The difference in the electronic structure and bonding between Zr and T in (Zr_1−xT_x)₃Al₃C₅ compounds are shown to account for the abnormal variations in their properties. (paper)