Doping effects on mechanical and thermodynamic properties of zirconium carbide systems: a first-principles study

Abstract

Zirconium carbide (ZrCx) is an important high temperature structural material, whose wide engineering applications are limited by carbon vacancies. Doping various impurity elements (O, B, etc) into ZrCx may lead to a significant change in its mechanical properties and thermodynamic properties behaviors. In this paper, based on the density functional theory, the effects of carbon vacancy contents and dopant on mechanical properties and deformation behaviors of zirconium carbide were discussed. With the increase of the carbon vacancy contents, the Young’s modulus, bulk modulus, and shear modulus decrease gradually. When the tensile strain is greater than 0.4, ZrC0.75 has stronger plasticity than ZrC0.875, ZrC0.9375 and ZrC. Furthermore, the mechanical properties of ZrC, ZrC0.75O0.25, ZrC0.75B0.25 and ZrC0.75 were studied. Compared with ZrC0.75, the mechanical properties of ZrC0.75O0.25 and ZrC0.75B0.25 are improved, and the mechanical properties of the systems are improved the most by doping O atoms. Based on the quasi-harmonic approximation, the influence of doping atoms on thermodynamic properties of ZrC0.75O0.25, ZrC0.75B0.25 and ZrC0.75 was also investigated. Doping O and B atoms in ZrC0.75 can improve the thermal conductivity at high temperature, and ZrC0.75B0.25 has the highest thermal conductivity. The results also show that the thermal properties of ZrC0.75 can be improved by doping O and B atoms. With the increase of temperature, ZrC0.75O0.25 has the largest thermal expansion.