Journal of Advanced Ceramics


high-entropy ceramics, high-entropy borides, reactive sintering, spark plasma sintering, Ta3B4-prototyped orthorhombic structure


A new class of high-entropy M3B4 borides of the Ta3B4-prototyped orthorhombic structure has been synthesized in the bulk form for the first time. Specimens with compositions of (V0.2Cr0.2Nb0.2Mo0.2Ta0.2) 3B4 and (V0.2Cr0.2Nb0.2Ta0.2W0.2) 3B4 were fabricated via reactive spark plasma sintering of high-energy-ball-milled elemental boron and metal precursors. The sintered specimens were ~98.7% in relative densities with virtually no oxide contamination, albeit the presence of minor (4-5 vol%) secondary high-entropy M5B6 phases. Despite that Mo3B4 or W3B4 are not stable phase, 20% of Mo3B4 and W3B4 can be stabilized into the high-entropy M3B4 borides. Vickers hardness was measured to be 18.6 and 19.8 GPa at a standard load of 9.8 N. This work has further expanded the family of different structures of high-entropy ceramics reported to date.


Tsinghua University Press