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 (Gd1/2Lu1/2)2(Ti1/3Zr1/3Hf1/3)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.