Influence of Transition Metals on the Structural Stability and Brittle‐to‐Ductile Transition of YB ₄ High‐Temperature Ceramics

Although YB 4 is regarded as a promising high‐temperature ceramic, its intrinsic brittleness limits engineering application. To solve this problem, we used first‐principles method to study the influence of refractory metals on the structural stability, elastic properties, and brittle‐to‐ductile behavior of YB 4 ceramics. The calculated results show that four TM‐doped YB 4 exhibit thermodynamic stability, while Ta‐doped, W‐doped, and Os‐doped YB 4 are dynamical stability. Note that these doped metals result in the brittle‐to‐ductile transition of YB 4 ceramics with increasing valence electronic density of these doped metals. In particular, Os‐doped YB 4 exhibits ductile behavior, which is demonstrated by the change in B/G ratio and Poisson's ratio. In addition, four TM‐doped YB 4 also exhibit a high bulk modulus in comparison with the parent YB 4 . Naturally, the brittle‐to‐ductile transition of YB 4 ceramics is that the introduction of transition metal weakens the electronic interaction between B and B atoms along the shear direction, which is demonstrated by the bond strength of BB covalent bond. Therefore, we believe that by doping the above refractory metals into YB 4 ceramics while maintaining its high bulk modulus, it is expected to improve the ductility of YB 4 ceramics.