Thermophysical properties and corrosion behavior against Na2SO4-V2O5 of cerate high-entropy ceramics

A novel high-entropy ceramic (La 0.2 Nd 0.2 Y 0.2 Eu 0.2 Gd 0.2 ) 2 Ce 2 O 7 (RE 2 Ce 2 O 7 ) was synthesized, its thermophysical properties and corrosion behavior against Na 2 SO 4 -V 2 O 5 molten salt were systematically investigated. Owing to the synergistic effect of the high-entropy configuration, RE 2 Ce 2 O 7 exhibits a remarkably low thermal conductivity, characterized by 1.22 W·m −1 ·K −1 at 1200 ℃. The Debye temperature Θ D of RE 2 Ce 2 O 7 is 493 K and the coefficient of thermal expansion (CTE) is 11.4 × 10 −6 K −1 . During corrosion process at 900 ℃ ∼ 1100 ℃, rare-earth ions are precipitated from the lattice and combined with VO 4 3- ions formed rod-shaped REVO 4 phases, while Ce 4+ ions react with O 2- formed CeO 2 . With increasing temperature, REVO 4 grains are coarsened and cover the CeO 2 phase. When the molten salt is exhausted at 1100 ℃, Ce 3+ in REVO 4 is continuously oxidized to Ce 4+ and diffused to the surface, facilitating extensive nucleation and growth of CeO 2 .