Improving CMAS corrosion resistance of RE2Si2O7 by non-equimolar component design

Abstract

Rare-earth disilicates (RE₂Si₂O₇) environmental barrier coatings (EBCs) face severe degradation from molten calcium-magnesium-aluminosilicate (CMAS) deposits in high-temperature environments. This study proposes a strategy to improve the CMAS corrosion resistance of RE₂Si₂O₇ through the design of non-equimolar rare-earth elements. Four kinds of (nRE_xi)₂Si₂O₇ ((Yb_0.8Er_0.1Y_0.1)₂Si₂O₇, (Yb_0.8Er_0.1Tm_0.1)₂Si₂O₇, (Yb_0.7Er_0.1Tm_0.1Y_0.1)₂Si₂O₇, (Yb_0.7Er_0.1Tm_0.1Ho_0.1)₂Si₂O₇) were synthesized via solid-state reactions and subjected to CMAS corrosion at 1400 ℃ for 4 and 25 h. All compositions retained the thermodynamically stable β-phase up to 1600 ℃. The CMAS corrosion results indicated that compared to Yb₂Si₂O₇, the multi-rare-earth composition design significantly improves the formation of apatite products, and the continuous product layer is an effective barrier against CMAS penetration. The corrosion resistance against CMAS was significantly influenced by both the types of RE^3 + cations and their stoichiometric proportions in (nRE_xi)₂Si₂O₇. After corrosion for 25 h, (Yb_0.8Er_0.1Tm_0.1)₂Si₂O₇ demonstrated exceptional performance, forming a dense, continuous apatite layer that suppressed CMAS infiltration. The corrosion mechanism involved RE³⁺ dissolution, apatite precipitation, and Ca/Si ratio evolution. The non- equimolar multiple rare-earth doping enhanced lattice stability and reduced distortion optimizing the thermodynamic-kinetic balance, providing an effective method for modulating the corrosion properties of rare-earth silicates used as EBCs.