Novel (Yb_0.2Tm_0.2Lu_0.2Sc_0.2Gd_0.2)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 (Yb_0.2Tm_0.2Lu_0.2Sc_0.2Gd_0.2)₂Si₂O₇ ((5RE_0.2)₂Si₂O₇) was synthesized through solid-phase sintering. Experimental results reveal that (5RE_0.2)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, (5RE_0.2)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-13AlO_1.5-45SiO₂ (CMAS) at 1500 ℃ for 48 h, it forms a protective apatite Ca₂RE₈(SiO₄)₆O₂ layer, preventing CMAS penetration. Overall, the development of (5RE_0.2)₂Si₂O₇ offers a promising alternative for future EBCs advancements, owing to its favorable comprehensive performance.