Effects of Al substitution by Si in Ti₃AlC₂ nanolaminate

Recently, a series of high-purity Ti₃(Al_1-xSi_x)C₂ solid solutions with new compositions (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) have been reported with interesting mechanical properties. Here, we have employed density functional theory for Ti₃(Al_1-xSi_x)C₂ solid solutions to calculate a wider range of physical properties including structural, electronic, mechanical, thermal and optical. With the increase of x, a decrease of cell parameters is observed. All elastic constants and moduli increase with x. The Fermi level gradually increases, moving towards and past the upper bound of the pseudogap, when the value of x goes from zero to unity, indicating that the structural stability reduces gradually when the amount of Si increases within the Ti₃(Al_1-xSi_x)C₂ system. In view of Cauchy pressure, Pugh's ratio and Poisson's ratio all compositions of Ti₃(Al_1-xSi_x)C₂ are brittle in nature. Comparatively, low Debye temperature, lattice thermal conductivity and minimum thermal conductivity of Ti₃AlC₂ favor it to be a thermal barrier coating material. High melting temperatures implies that the solid solutions Ti₃(Al_1-xSi_x)C₂ may have potential applications in harsh environments. In the visible region (1.8-3.1 eV), the minimum reflectivity of all compositions for both polarizations is above 45%, which makes them potential coating materials for solar heating reduction.