Temperature-dependent hardness of zinc-blende structured covalent materials

Abstract

Understanding the temperature-dependent hardness of covalent materials is of fundamental scientific interest and crucial technical importance. Here we propose a temperature-dependent hardness formula for zinc-blende structured covalent materials based on the dislocation theory. Our results indicate that at low temperatures, the Vickers hardness is primarily modulated by Poisson’s ratio and the shear modulus, with the latter playing a dominant role. With an increase in temperature, the governing mechanism for the plastic deformation switches from shuffle-set dislocation control to glide-set dislocation control, and the hardness decreases precipitously at elevated temperatures. Moreover, the intrinsic parameter a3G is revealed for zinc-blende structured covalent materials, which represents the resistance of a material to softening at high temperatures. This temperature-dependent hardness model agrees remarkably well with the experimental data of zinc-blende structured covalent materials. This work not only sheds light on the physical origin of hardness, but also provides a practical guide for the design of superhard materials.