Flexible dual-phase rare-earth zirconate high-entropy ceramic nanofibrous membranes for superior thermal insulation

Ceramic fibers are potential lightweight materials for high-temperature insulation due to their excellent high-temperature stability and low thermal conductivity. However, the grain growth at high temperatures leads to the loss of flexibility and decreases in the thermal insulation performances of the ceramic fibers. Herein, we prepared flexible (La_0.2Nd_0.2Sm_0.2Gd_0.2Yb_0.2)₂Zr₂O₇ (LNSGY) high-entropy ceramic nanofibrous membranes using polyacetylacetone rare-earth zirconium precursors by electrospinning method. According to the XRD and TEM analyses, the LNSGY nanofibrous membranes exhibited dual phases of defective fluorite and ordered pyrochlore structures. The grain size of the LNSGY fibers increased from 15.4 to 40.8 nm at heat treatments increasing from 800 to 1200°C; the slow grain growth in high-entropy ceramic nanofibrous membranes contributed to the good flexibility. The fiber morphology was continuous and well distributed with diameters less than 500 nm. The thermal conductivity at room temperature was 0.0339 W/(m K). In addition, the high-entropy ceramic nanofibrous membranes exhibited tensile strength and thermal stability at high temperatures. These performances provide further applications for high-entropy ceramic nanofibrous membranes as high-temperature insulation materials.