Novel high entropy (Y0.2Sm0.2Gd0.2Er0.2Ho0.2)3NbO7 nanofibers with ultralow thermal conductivity

Abstract Thermal insulation materials can provide thermal protection in extreme environments. Ceramic fibers have played an important role in the thermal protection field at high temperatures due to the advantages of low density, high strength, low thermal conductivity, and excellent thermal stability. In this work, high entropy (Y 0.2 Sm 0.2 Gd 0.2 Er 0.2 Ho 0.2 ) 3 NbO 7 (5RE 3 NbO 7 ) nanofibers were fabricated by electrospinning and subsequent calcination. Defective fluorite‐structured 5RE 3 NbO 7 nanofibers were obtained when heated at 900°C. The research indicates that 5RE 3 NbO 7 nanofiber based porous ceramics present an ultralow thermal conductivity (0.0992 W/m·K, porosity of 78.18%), good thermal stability, and high spectral reflectance, which establish the foundation for applications in thermal insulation.