Low thermal conductivity and enhanced thermal cycling performance of (Sm0.2Gd0.2Dy0.2Er0.2Yb0.2)2Zr2O7 coating

Abstract In this work, the thermal performance of the high‐entropy (Sm 0.2 Gd 0.2 Dy 0.2 Er 0.2 Yb 0.2 ) 2 Zr 2 O 7 (HEFO) coating was evaluated. The as‐sprayed HEFO coating exhibited a significantly lower initial thermal conductivity of <0.80 W·m −1 ·K −1 , almost half of that of the conventional yttria‐stabilized zirconia (YSZ) coating (∼1.2 W·m −1 ·K −1 ). When subjected to prolonged sintering at 1300°C for 40 h, the thermal conductivity of the HEFO coating gradually increased to ∼1.1 W·m −1 ·K −1 at 1200°C. Moreover, the HEFO coating demonstrated a thermal expansion coefficient of approximately 11 × 10 −6 K −1 , which aligns with that of YSZ coatings. The HEFO coating showed improved durability during thermal cycling tests at 1100°C in air, and its lifetime was 919 cycles. The improvement can be attributed to the excellent phase stability and chemical compatibility.