Novel (Yb0.2Tm0.2Lu0.2Sc0.2Gd0.2)2Si2O7: Exploring its potential for comprehensive performance in environmental barrier coatings

Aiming to meet the growing demand for high-performance environmental barrier coatings (EBCs), a novel high-entropy material (Yb0.2Tm0.2Lu0.2Sc0.2Gd0.2)2Si2O7 ((5RE0.2)2Si2O7) was synthesized through solid-phase sintering. Experimental results reveal that (5RE0.2)2Si2O7 maintains a stable monoclinic phase up to 1550°C and exhibits a coefficient of thermal expansion (CTE) from 1.96×10-6 K-1 to 3.95×10-6 K-1 between 300 °C and 1300 °C, matching well with Si, a commonly used EBC undercoat material. Moreover, (5RE0.2)2Si2O7 displays remarkably low thermal conductivity (1.146 W·m-1·K -1 at 1100 ℃), even approximately 45.85% lower than that of the most widely used thermal barrier coatings material YSZ at 1000 ℃. When exposed to molten 33CaO-9MgO-13AlO1.5-45SiO2 (CMAS) at 1500 ℃ for 48 h, it forms a protective apatite Ca2RE8(SiO4)6O2 layer, preventing CMAS penetration. Overall, the development of (5RE0.2)2Si2O7 offers a promising alternative for future EBCs advancements, owing to its favorable comprehensive performance.