Pyrochlore-fluorite dual-phase high-entropy ceramic foams with extremely low thermal conductivity from particle-stabilized suspension

Low thermal conductivity is highly desirable for porous ceramics for thermal insulation applications at high temperature. In this work, (La_0.2Nd_0.2Sm_0.2Gd_0.2Yb_0.2)₂Zr₂O₇ high-entropy powders with a pyrochlore-fluorite dual-phase structure were prepared by a solid-state reaction method. (La_0.2Nd_0.2Sm_0.2Gd_0.2Yb_0.2)₂Zr₂O₇ high-entropy ceramic foams were fabricated using a particle-stabilized foaming method. The as-prepared high-entropy ceramic foams exhibit high porosity (87.99%-96.89%) and low thermal conductivity (0.045-0.102 W/(m·K)). The (La_0.2Nd_0.2Sm_0.2Gd_0.2Yb_0.2)₂Zr₂O₇ high-entropy ceramic foam from a 20 wt% suspension sintered at 1500°C has a porosity of 96.89% and a thermal conductivity of 0.045 W/(m·K). The results indicate that pyrochlore-fluorite dual-phase high-entropy ceramic foams from particle-stabilized foams are candidate materials for high-temperature insulation applications.