Entropy regulation in spinel oxide with narrowed band gap and lattice distortion toward high-temperature infrared radiation

Typical infrared (IR) radiation materials, such as spinel structure with transition metal doping , remain challenges on IR radiation performance and thermal stability. Inspired by manipulatable entropy with desired properties, (Mg 1/5 Co 1/5 Ni 1/5 Cu 1/5 Zn 1/5 )Al 2 O 4 (5MAl 2 O 4 ) with improved infrared radiation property and reduced thermal conductivity has been successfully synthesized. High-entropy strategy significantly narrows the band gap by impurity energy level formation, resulting in an improved 0.91 (0.78–2.5 μm). Simultaneously, 5MAl 2 O 4 emerges site inversion (tetrahedral and octahedral sites) and lattice distortion which benefits the outstanding infrared emissivity of 0.94 (2.5–15 μm, measured at 800 °C). Furthermore, 5MAl 2 O 4 reaches fairly low thermal conductivity of 2.1 W·m −1 ·K −1 , 4–5 times decrease compared with MAl 2 O 4 end members. The remarkable infrared emissivity and low thermal conductivity offer great potential in energy conservation and heat dissipation.