Reactive flash spark plasma sintering of high-entropy ultrahigh temperature ceramics

A new Reactive Flash Spark Plasma Sintering (ReaFSPS) method has been developed to synthesize high-entropy ultrahigh temperature ceramics (UHTCs), using (Hf0.2Zr0.2Ta0.2Nb0.2Ti0.2)B2 and (Hf0.2Zr0.2Ta0.2Nb0.2Ti0.2)C as examples. X-ray diffraction, energy dispersive X-ray spectroscopy, and electron backscatter diffraction collectively show the formation of a single high-entropy phase within ~2 min. Notably, adding 3 wt.% of carbon can promote the formation and homogenization of a high-entropy diboride phase without aggressive mechanical alloying, achieving a >99% relative density. This work has established a new rapid and potentially scalable method to use ReaFSPS to synthesize homogenous high-entropy UHTCs from commercial powders of individual constituents.