Rare-earth zirconates against environmental silicate corrosion in jet engines

Environmental silicate deposits are among the most critical factors driving high-temperature degradation of thermal barrier ceramics, yet the intrinsic corrosion mechanisms remain insufficiently understood. Rare-earth zirconates (RE₂Zr₂O₇) have emerged as promising next-generation candidates, but their resistance to molten silicate attack varies widely with the choice of rare earths. Here, we systematically investigate 15 RE₂Zr₂O₇ compositions based on La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Er, Tm, Yb, Lu, and Sc. High-temperature wetting and long-term corrosion experiments at 1300 °C reveal a multivariate dependence of molten silicate spreading and degradation on RE ionic radius, which we examine in terms of lattice energy, RE–O bond ionicity, optical basicity, apatite formation enthalpy, and RE content in fluorite products. Two distinct corrosion modes can be identified: exemplified by exhibits dissolution-controlled interfaces lacking protective barriers (e.g., Tm zirconates) and precipitation-controlled interfaces composed of either dense RE/Ca-apatite/fluorite (e.g., La zirconates) or Sc-garnet layers (Sc zirconates) that act as protective barriers. These results elucidate the fundamental role of rare-earth chemistry in CMAS reactivity and provide mechanistic guidance for designing compositionally optimized (high-entropy) zirconates with superior environmental durability for advanced aero-engine and gas turbine applications.