Extraordinary Thermal Radiation Suppression Enables High‐Entropy Oxide Ceramics for Ultrahigh‐Temperature Protection up to 2000 K

The escalating energy crisis and the demand for thermal protection under extreme environments require materials that effectively suppress heat transport while maintaining long‐term thermal stability. However, thermal insulation ceramics inherently suffer from the dual challenge of simultaneously inhibiting lattice heat transfer and radiative heat transfer. Here, we establish a synergistic regulation of solid‐state and radiative heat transfer through rare‐earth site compositional screening and entropy engineering. This principle informs the development of a physics‐informed constrained random forest model for predicting wavelength‐dependent infrared radiation properties in the RE 3 TaO 7 system, facilitating efficient screening of candidate compositions. High‐throughput screening of 504 structural variants has led to the identification of 21 candidates with a representative high‐entropy ceramic of (Nd 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Y 0.2 ) 3 TaO 7 that exhibits ultralow near‐infrared transmittance (< 1% over 0.78–2.5 µm), high broadband emissivity (> 0.9 over 2.5–14 µm) and low radiative thermal conductivity of 0.035 W m −1 K −1 at 1273 K. This work makes progress in high‐entropy thermal‐protective ceramics for extreme environments and establishes a general framework for advanced thermal insulation materials.