Rare‐earth compositional screening of high‐entropy diborides for improved oxidation resistance

Abstract Compositional screening is an important strategy to improve the oxidation resistance of high‐entropy diborides (HEB 2 ), yet the related studies are limited. Here, we report a rare‐earth (RE) element compositional screening strategy to improve the oxidation resistance of HEB 2 . To be specific, the single‐phase (Hf 0.28 Zr 0.28 Ta 0.28 RE 0.16 )B 2 (HEB 2 ‐RE) samples with 12 different RE elements are fabricated via ultrafast ultrahigh‐temperature synthesis and spark plasma sintering techniques, and their oxidation resistance is explored by isothermal oxidation tests. The results show that the as‐obtained HEB 2 ‐Sc samples possess the best oxidation resistance among all the as‐fabricated HEB 2 ‐RE samples. Such outstanding oxidation resistance is ascribed to the enhanced viscosity of the generated B 2 O 3 glass originating from the solid solution of (Zr, Me) 0.84 Sc 0.16 O 2 complex oxides, as confirmed by transmission electron microscope observations and first‐principles calculations.