High-entropy (YErYbLu)₂SiO₅ ceramic aerogel: A potential ceramic insulator with low thermal conductivity

Conventional oxide aerogels have limitations in terms of structural damage and phase transformation at high temperatures. A novel high-entropy (YErYbLu)₂SiO₅ ceramic aerogel was synthesized by a combination of the sol-gel process, supercritical drying, and high-temperature calcination. The successful synthesis of a high-entropy (YErYbLu)₂SiO₅ ceramic aerogel in a single phase after calcination at 1250 °C was confirmed by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The high-entropy ceramic aerogel (YErYbLu)₂SiO₅ still shows excellent structural and phase stability after annealing at 1400 °C. The structurally reconstructed samples (RSO) exhibit low densities ranging from 1.79 to 3.28 g/cm³, room-temperature thermal conductivities between 0.109 and 0.253 W·m^-1 K^-1, and fracture toughness values ranging from 0.61 to 9.70 MPa. Notably, the lowest thermal conductivity is less than 1/10 of that of the corresponding dense crystalline ceramics. Furthermore, the RSO has a low coefficient of thermal expansion within the temperature range of 360–1200 °C (ranging from 5.84 × 10⁻⁶ °C⁻¹ to 7.36 × 10⁻⁶ °C⁻¹). The RSO exhibits high residual strength retention after thermal shock testing. These properties position the high-entropy (YErYbLu)₂SiO₅ ceramic aerogel as a promising candidate for nano-thermal insulation as a porous ceramic material that undergoes structural reconstruction.