Synthesis of high entropy monoboride (Mo0.25W0.25Cr0.25Ta0.25)B powders with abundant twins from oxides

Abstract High entropy monoborides powders are mainly prepared from metal and boron powders which can be costly. In this study, a novel approach starting from mixed oxides, boron carbide, and graphite was first developed to synthesize quaternary monoboride powders by combining multiple boro/carbothermal reductions (MBCTR). As an exemplar, (Mo 0.25 W 0.25 Cr 0.25 Ta 0.25 )B powders with purity up to 94.3 wt.% were successfully synthesized by heating the mixtures in vacuum at 1650°C for three times, as‐synthesized powders exhibit fine particle size (<1 µm) and uniform elemental distribution. MBCTR not only increased the purity of monoborides but resulted in abundant twins and stacking faults in the final powders. This work has proposed a new and low‐cost strategy of synthesizing high‐purity and fine monoboride powders.