Extreme-mixing-boosted CMAS corrosion resistance and thermophysical properties in high-entropy rare-earth disilicates

Abstract

Superior calcium-magnesium-alumino-silicate (CMAS) corrosion resistance, along with favorable thermophysical properties, is crucial for high-entropy rare-earth disilicates (HEREDs) to be used as environmental barrier coatings. To achieve this goal, we expand the composition space of HEREDs and develop 9- to 16-cation HEREDs by a laser-driven synthesis technique. Specifically, the intensified sluggish diffusion effect induced by extreme element mixing and the superior stability of the F-type phase in HEREDs are beneficial to reducing the dissolution rate of the formed multicomponent apatite in the CMAS melt, while the inclusion of more elements with great atomic weight differences can induce phase separation, leading to deteriorated corrosion behavior. As a result, the synthesized (Lu, Yb, Tm, Er, Ho, Dy, Gd, Nd, Pr, Ce, La, Eu, Tb, Y)2Si2O7 (14HERED) is found to demonstrate superior CMAS corrosion resistance with a low corrosion rate of 6.7 μm h-1 at 1400 °C for 48 h. Moreover, remarkable thermophysical properties, including superior phase stability over 1600 °C, extremely low room temperature thermal conductivity (1.05 W m-1 K-1), and excellent match of coefficient of thermal expansion (5.4×10-6 K-1) with SiCf/SiC composites (4.5-5.5×10-6 K-1), are observed in the synthesized 14HERED. Our work develops a novel material with remarkable CMAS corrosion resistance and thermophysical properties, showing great promise for the environmental barrier coating application.