New spinel‐structured high‐entropy oxides with high‐ and stable‐infrared radiation properties

Abstract Spinel‐structured high‐entropy oxides (HEOs), the novel materials, have recently attracted great attention for their unexpected properties and extensive applications. In this work, employing a facile scalability process of solid‐state reaction method, we synthesized a new kind of non‐equimolar (Co 2/11 Mn 2/11 Fe 2/11 Cr 2/11 Ni 2/11 Cu 1/11 ) 3 O 4 HEOs powder. However, under the same condition, the raw mixed oxide powders, with equimolar cations and higher configuration entropy, cannot form single‐phase HEOs powder but with the mixture of (Co,Mn,Fe,Cr,Ni,Cu) 3 O 4 and residual CuO powders, ruling out the crucial role of entropy effect in forming single‐phase spinel‐structured HEOs. In addition to (Co 2/11 Mn 2/11 Fe 2/11 Cr 2/11 Ni 2/11 Cu 1/11 ) 3 O 4 powder, various (Co,Mn,Fe,Cr,Ni,Cu) 3 O 4 HEOs powders can be obtained by controlling the Cu cation content in an appropriate range. To explore the application of the spinel‐structured HEOs in high‐temperature infrared field, the infrared radiation properties of the (Co 2/11 Mn 2/11 Fe 2/11 Cr 2/11 Ni 2/11 Cu 1/11 ) 3 O 4 powder were evaluated and exhibited a high‐infrared radiation emissivity of 0.880 in the near‐infrared wavelength range (0.78–2.5 µm) and superior thermal stability. Notably, the infrared radiation emissivity of the HEOs powder was maintained at 0.855 with a slight loss of 2.8% after high‐temperature treatment. This work not only provides a valuable strategy for fabricating high‐ and stable‐infrared radiation properties materials but also expands the great potential application of spinel‐structured HEOs to high‐temperature infrared field, such as energy saving in industrial high‐temperature furnaces.