Crystal Orientation Engineering of Oxidation Resistance of TaB ₂

ABSTRACT Transition metal diborides (TMB 2 ) possess excellent properties but suffer from rapid oxidation at elevated temperatures, severely limiting their applications. Here, we demonstrate crystal orientation engineering as an effective strategy to enhance oxidation resistance while retaining intrinsic characteristics. The polycrystalline TaB 2 films with strong (001) and (100) preferred orientations were synthesized via substrate‐bias‐controlled deposition. Air annealing revealed that (001)‐oriented TaB 2 films exhibit significantly improved oxidation resistance over (100)‐oriented films. First‐principles calculations show that the TaB 2 (001) surface has higher oxygen adsorption energy and a larger diffusion barrier, attributed to the alternating boron–metal layer stacking along [001]. Moreover, (001)‐oriented films maintain higher hardness and shear strength at both room temperature and 600°C. These findings establish orientation control as a promising pathway to simultaneously optimize oxidation resistance and mechanical robustness in TMB 2 , offering guidance for the design of protective coatings for high‐temperature applications.