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

Abstract

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, (Mg1/5Co1/5Ni1/5Cu1/5Zn1/5)Al2O4 (5MAl2O4) 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, 5MAl2O4 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, 5MAl2O4 reaches fairly low thermal conductivity of 2.1 W·m−1·K−1, 4–5 times decrease compared with MAl2O4 end members. The remarkable infrared emissivity and low thermal conductivity offer great potential in energy conservation and heat dissipation.