High entropy rare earth hexaborides/tetraborides (HE REB6/HE REB4) composite powders with enhanced electromagnetic wave absorption performance

The increasing electromagnetic hazards including electromagnetic interference and electromagnetic pollution, which were stemmed from massive usage of electromagnetic technology, have triggered widespread concerns. To cope with this challenge, electromagnetic wave absorbing materials with high performance are greatly needed. Composite construction has been widely applied in electromagnetic (EM) wave absorbing materials to achieve high permittivity, high permeability and impedance matching. However, high-temperature stability, oxidation and corrosion resistance are still unignorable issues. Herein, high entropy hexaborides/tetraborides (HE REB6/HE REB4) composites with synergistic dielectric and magnetic losses were designed and successfully synthesized through a one-step boron carbide reduction method. The five as-prepared (Y0.2Nd0.2Sm0.2Eu0.2Er0.2)B-6/ (Y0.2Nd0.2Sm0.2Eu0.2Er0.2)B-4, (Y0.2Nd0.2Sm0.2 Er0.2Yb0.2)B-6/ (Y0.2Nd0.2Sm0.2Er0.2Yb0.2)B-4, (Y0.2Nd0.2Eu0.2Er0.2Yb0.2)B-6/ (Y0.2Nd0.2Eu0.2Er0.2Yb0.2)B-4, (Nd0.2Sm0.2Eu0.2Er0.2Yb0.2)B-6/ (Nd0.2Sm0.2Eu0.2Er0.2Yb0.2)B-4 and (Y0.2Sm0.2Eu0.2Er0.2Yb0.2)B-6/ (Y0.2Sm0.2Eu0.2Er0.2Yb0.2)B-4 contain two phases of HE REB6 and HE REB4. Among them (Y0.2Nd0.2Sm0.2Eu0.2Er0.2)B-6/ (Y0.2Nd0.2Sm0.2Eu0.2Er0.2)B-4 (HE REB6/ HE REB4-1) and (Y0.2Nd0.2Sm0.2Er0.2Yb0.2)B-6/ (Y0.2Nd0.2Sm0.2Er0.2Yb0.2)B-4 (HE REB6/ HE REB4-2) exhibit excellent EM wave absorption properties. The optimal minimum reflection loss (RLmin) and effective absorption bandwidth (EAB) of HE REB6/HE REB4-1 and HE REB6/HE REB4-2 are -53.3 dB (at 1.7 mm), 4.2 GHz (at 1.5 mm) and -43.5 dB (1.3 mm), 4.2 GHz (1.5 mm), respectively. The combination of conducting HE REB4 with magnetism into HE REB6 as a second phase enhances dielectric and magnetic losses, which lead to enhanced EM wave absorption performance. Considering superior high-temperature stability, oxidation and corrosion resistance of HE REB6 and HE REB4, HE REB6/HE REB4 composite ceramics are promising as a new type of high-performance EM wave absorbing materials. (C) 2021 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.