Mechanism of enhanced corrosion resistance against molten CMAS for pyrosilicates by high‐entropy design

Abstract

AbstractMeeting service requirements at temperatures above 1400°C is challenging for the CMAS corrosion resistance of single‐component pyrosilicates. This research presents a high‐entropy design approach for pyrosilicates using ionic radius modulation. This method enhances pyrosilicates’ resistance to CMAS corrosion by regulating the apatite's quantity formed to obstruct CMAS melt infiltration while avoiding excessive reactions. We investigated the corrosion behavior of two types of single‐component pyrosilicates (Lu2Si2O7 and Yb2Si2O7) with a small ionic radius of rare‐earth elements (REEs), three types of β‐type pyrosilicates ((Ho1/4Er1/4Yb1/4Lu1/4)2Si2O7, (Y1/5Ho1/5Er1/5Yb1/5Lu1/5)2Si2O7 and (Y1/6Ho1/6Er1/6Tm1/6Yb1/6Lu1/6)2Si2O7), and one γ‐type pyrosilicate ((Gd1/4Dy1/4Yb1/4Lu1/4)2Si2O7) with a larger average ionic radius of REEs at 1450–1550°C. The analysis of the residual CMAS and apatite compositions showed the differences in the behavior of different REEs in the reaction with CMAS and the conditions required for the reaction to proceed.