Ultra-multicomponent high-entropy (12RE1/12)2Zr2O7 ceramics with enhanced performance and CMAS corrosion resistance

Here, we report a novel ultra-multicomponent (12RE_1/12)₂Zr₂O₇ ceramic with high configuration entropy. The microstructure, mechanical and thermal properties, and molten silicate environment (CaO-MgO-Al₂O₃-SiO₂, CMAS) corrosion behavior of the ceramic were also investigated. The results show that the ceramic possesses excellent sintering resistance, with an average grain growth rate of 0.5 nm h⁻¹. In addition, the ceramic exhibits enhanced mechanical properties, with a hardness of 13.48±0.32 GPa and a fracture toughness of 1.79±0.04 MPa m^1/2. In terms of thermal performance, the ceramic exhibits low thermal conductivity (1.68 W m⁻¹ K⁻¹, 1000°C) and moderate thermal expansion coefficient (CTE, 10.78×10⁻⁶ K⁻¹, 1200°C). The CMAS corrosion experiment shows that the corrosion products are mainly composed of (RE, Ca)-ZrO₂ and apatite-type Ca₂RE₈(SiO₄)₆O₂ structures, in which the content of rare-earth elements is directly proportional to the optical basicity (OB) of its oxide, while it is exactly the opposite in (RE, Ca)-ZrO₂. In addition, the difference in OB is a key factor affecting the corrosion resistance of high-entropy rare-earth zirconates (HE-REZs), as HE-REZ composed of heavy rare-earth elements exhibit better corrosion resistance due to their lower OB value. This study provides a theoretical and experimental basis for the application of HE-REZs in high-temperature CMAS corrosion environments.