One-step synthesis of high-entropy diborides with hierarchy structure and high hardness via aluminum-melt reaction method

Two new high-entropy metal diborides (ZrTiVCr)B2 and (ZrTiVCrMn)B2 were successfully synthesized via a novel aluminum melt reaction method. The high-entropy diboride crystals have a hexagonal structure and possess high compositional uniformity. We unexpectedly found that the Mn elements could significantly change the crystal morphology of (ZrTiVCrMn)B2, resulting in a hierarchically structured nanosheet-assembled nanoplatelet shape. Benefiting from this interesting hierarchical structure and enhanced lattice distortion, the average hardness of the (ZrTiVCrMn)B2 phase is significantly enhanced to 31.44 GPa as compared to that of (ZrTiVCr)B2 for 28.82 GPa. This work will supply a new paradigm for synthesizing high-entropy metal diborides.