Temperature- and pressure-dependent elastic properties, thermal expansion ratios, and minimum thermal conductivities of ZrC, ZrN, and Zr(C0.5N0.5)

Abstract

We investigated the temperature- and pressure-dependent properties of ZrC, ZrN, and Zr(C0.5N0.5) solid solution using first-principles calculations with Debye-Gruneisen theory. The properties investigated included elastic moduli, thermal expansion coefficients, and thermal conductivities. Equilibrium volumes were determined by obtaining the energy volume (E-V) curves of ZrC, ZrN, and Zr(C0.5N0.5) at different temperatures and external pressures. We adopted quasi-harmonic and quasi-static approximations to examine the influence of temperature and pressure on the elastic properties. Throughout the temperature and pressure ranges studied, the bulk modulus of the ZrN phase was higher than that of the other two phases, whereas its shear and Young's moduli were lower. An increase in nitrogen content resulted in an increase in the thermal expansion coefficient. The hardness, anisotropic properties, and minimum thermal conductivities of Zr(C0.5N0.5) and ZrC were similar, whereas those of the Zr(C0.5N0.5) phase were somewhat larger. Given its elastic properties, anisotropy, hardness, and minimum thermal conductivity, Zr(C0.5N0.5) is the best of the three phases for extreme environmental applications. Our results provide fundamental and useful information on the ZrC, ZrN, and Zr(C0.5N0.5) phases.