Superelastic High-Entropy Oxide Ceramic Aerogels for Thermal Superinsulation and Sealing at Extreme Conditions

The lightweight ceramic aerogels are plagued by thermal instability and mechanical degeneration at extreme conditions. In this study, a high-entropy oxide ceramic of (Gd_1/2Lu_1/2)₂(Ti_1/3Zr_1/3Hf_1/3)₂O₇ (GLTZH) is prepared through a molecular synthesis route of pyrolytic solid-solution reactions. The atomic resolution observations visualize the phase transition of polyacetylacetonato metal complexes into a defect-fluorite structured high-entropy oxide after thermal treatment at 200 to 1100 °C. The GLTZH oxide demonstrates exceptional crystallographic stability without severe grain growth, and element segregation appeared under prolonged exposure to extremely high temperature (≈1500 °C). This originates from the intricate coupling mechanism among entropy-driven lattice distortion, high-entropy stabilization, and orbital hybridization effects. Furthermore, GLTZH-based lightweight nanofiber aerogel is constructed through electrospinning and followed by thermal annealing at 1000 °C. This architectured high-entropy ceramic aerogel manifests unprecedented thermomechanical properties, including superelastic compressibility of 98% from -196 to 1500 °C, and thermal superinsulation capacity (24.14 mW·m^-1K^-1 at room temperature, 81.21 mW·m^-1K^-1 at 1000 °C). Due to superior performances beyond most conventional ceramic counterparts, the high-entropy GLTZH paves a new pathway for advanced ceramic aerogel design in thermal insulation across a wide temperature range, such as thermal protection of hypersonic aircraft.