Entropy‐Driven Ultra‐Broadband High‐Temperature Electromagnetic Absorption in Spinel Oxides up to 1000°C

ABSTRACT Ultra‐broadband high‐temperature electromagnetic (EM) ceramic absorbers are extensively desired for next‐generation radar stealth technologies; however, current absorbers are far from satisfactory. Here, we employ an entropy‐driven strategy to develop an innovative (Co, Ba, Fe, Mg, Cr, Ni, Sr, Ca, Mn)Fe 2 O 4 high‐entropy spinel oxide absorber, which possesses an ultrabroad effective absorption bandwidth (EAB) of 13.1 GHz at room temperature (RT), along with a wide‐temperature EAB retention of ∼100% up to 1000°C. This ultrabroad high‐temperature EM absorption performance mainly stems from the highly stable impedance matching enabled by the entropy‐driven sustenance of oxygen vacancy concentration at elevated temperatures, as well as the entropy‐driven amplification of EM dissipation via an atomic‐interface polarization loss. This work not only presents a promising EM absorber for future high‐temperature applications, but, more importantly, provides a key mechanistic insight that can be a guide for exploring high‐entropy ceramic absorbers with enhanced absorption performance.