High‐Entropy Engineering for Broadband Infrared Radiation

Abstract Developing high‐performance infrared (IR) radiation materials with desired broadband emissivity, excellent thermal stability, and scalable fabrication processes is highly desirable for energy‐saving applications and heat dissipation. However, it remains a grand challenge to concurrently meet these requirements in existing IR radiation materials. Herein, a high‐entropy (HE) approach is employed to advance the IR radiation performance of spinel oxide. This strategy efficiently narrows the bandgap due to the enhanced electron transitions and the introduction of oxygen vacancies (O v ), variable‐valence behavior, and orbital hybridization. In addition, the lattice distortion effect lowers the symmetry of lattice vibration. Therefore, the resulting HE spinel oxide exhibits near‐blackbody radiation performance, with its emissivity approximately three times higher than that of the binary spinel oxide. Moreover, the entropy‐dominating phase stabilization effect contributes to impressive thermal stability (stable at 1300 °C for 100 h). This makes it suitable for high‐temperature thermal radiation applications, such as energy conservation in industrial high‐temperature furnaces. More importantly, the HE spinel oxide can be readily spray‐coated on various substrates. And the coating on stainless steel reaches an outstanding emissivity of 0.943 in the 0.78−16 µm wavelength range. All these merits render the HE approach competitive for the development of high‐emissivity and thermally stable thermal radiation materials.