Blocking effect in Nb-engineered high-entropy oxides with strengthened grain boundary corrosion resistance

Lanthanum-cerium oxide derived high-entropy ceramics have been verified to be promising thermal barrier coatings (TBCs) materials for the protection of hot-end components in high-performance aero-engines/gas tur -bines. However, the dissatisfactory hot corrosion resistance of TBCs to Na2SO4 + V2O5 molten salt from fuel exhaust is identified as a crucial bottleneck. Herein, a stabilization element Nb is introduced into typical high-entropy cerates to strengthen the corrosion resistance. When corroded, it favors an intermittent generation of spindle-shaped corrosion products at grain boundary and effectively blocks the further penetration of corrosion medium. Compared with other constituent elements, Nb in the as-designed material presents a weak adsorption energy (-0.43 eV) with the final reaction intermediate of corrosion medium (VO43-). It yields an anchoring effect to stabilize the pristine crystal structure. What's more, the differential charge density of Ce is highly influenced by Nb, leading to a strong interaction with VO43-. With Ce tightly adsorbed around the corrosion products, it cooperatively hinders the further infiltration of molten salts. These findings provide an interesting insight into the rational design of superior corrosion-resistant high-entropy TBCs.