Significantly improved corrosion resistance of high‐entropy rare‐earth silicate multiphase ceramics against molten CMAS

To improve the ability of rare‐earth (RE) silicates to resist molten calcium–magnesium–aluminosilicate (CMAS) at high temperature, a novel high‐entropy (4RE 0.25 ) 2 Si 2 O 7 /(4RE 0.25 ) 2 SiO 5 (RE = Y, Yb, Er, and Sc) multiphase ceramic was prepared by a two‐step process. During sintering, (4RE 0.25 ) 2 SiO 5 can react with SiO 2 at the grain boundaries of (4RE 0.25 ) 2 Si 2 O 7 , which can not only purify the grain boundary but also promote the growth of the original (4RE 0.25 ) 2 Si 2 O 7 grains, thereby significantly improving the ability to resist molten CMAS corrosion at high temperature. After corroding at 1500°C for 48 h, the reaction layer of the multiphase ceramic was only 55 μm thick. Our results confirm that the high‐entropy RE silicate multiphase ceramics represent an effective way to improve the ability to resist molten CMAS corrosion at high temperature.