Role of configurational entropy in enhancing CMAS corrosion resistance of rare-earth zirconates

To investigate the influencing factors of CMAS corrosion resistance in rare-earth zirconates, seven low-, medium-, and high-entropy rare-earth zirconates RExZO (RE = Y, Ho, Dy, Er, Gd, Yb, Tm; x = 1-7) were prepared, and their CMAS corrosion behaviors at 1 300 ℃ were systematically studied. Results indicate that rare-earth zirconate materials undergo dissolution damage upon contact with CMAS at high temperatures, accompanied by the formation of a new apatite phase. The high-entropy structure facilitated the development of a dense reaction layer composed of apatite and fluorite phases through a “dissolution-reprecipitation” mechanism, significantly reducing the maximum infiltration depth from 80.6 μm for RE1ZO to 30.9 μm for RE7ZO (a 61.7% reduction). Influenced by ionic radius variations, dissolved rare-earth elements exhibited gradient diffusion into the apatite and fluorite phases. Correlation analyses reveal a significant positive relationship between corrosion depth and optical basicity difference, while showing significant negative correlations with configurational entropy and atomic size disorder. First-principles calculations and XPS results further confirm that high configurational entropy reduces the Gibbs free energy and oxygen vacancy concentration of rare-earth zirconates while enhancing elemental binding energy, thereby improving structural stability. Based on these findings, an optimization strategy for designing CMAS-resistant rare-earth zirconates is proposed: priority should be given to material combinations featuring low optical basicity difference, high configurational entropy, and high atomic size disorder.