Journal Article

One-step synthesis and electromagnetic absorption properties of high entropy rare earth hexaborides (HE REB6) and high entropy rare earth hexaborides/borates (HE REB6/HE REBO3) composite powders

Zhao, Biao, Xiang, Huimin, Dai, Fu-Zhi, Wu, Shijiang, Zhou, Yanchun, Zhang, Weiming

2021

Overview

Considering the emergence of severe electromagnetic interference problems, it is vital to develop electromagnetic (EM) wave absorbing materials with high dielectric, magnetic loss and optimized impedance matching. However, realizing the synergistic dielectric and magnetic losses in a single phase material is still a challenge. Herein, high entropy (HE) rare earth hexaborides (REB 6 ) powders with coupling of dielectric and magnetic losses were designed and successfully synthesized through a facial one-step boron carbide reduction method, and the effects of high entropy borates intermedia phases on the EM wave absorption properties were investigated. Five HE REB 6 ceramics including (Ce 0.2 Y 0.2 Sm 0.2 Er 0.2 Yb 0.2 )B 6 , (Ce 0.2 Eu 0.2 Sm 0.2 Er 0.2 Yb 0.2 )B 6 , (Ce 0.2 Y 0.2 Eu 0.2 Er 0.2 Yb 0.2 )B 6 , (Ce 0.2 Y 0.2 Sm 0.2 Eu 0.2 Yb 0.2 )B 6 , and (Nd 0.2 Y 0.2 Sm 0.2 Eu 0.2 Yb 0.2 )B 6 possess CsCl-type cubic crystal structure, and their theoretical densities range from 4.84 to 5.25 g/cm 3 . (Ce 0.2 Y 0.2 Sm 0.2 Er 0.2 Yb 0.2 )B 6 powders with the average particle size of 1.86 µm were found to possess the best EM wave absorption properties among these hexaborides. The RL min value of (Ce 0.2 Y 0.2 Sm 0.2 Er 0.2 Yb 0.2 )B 6 reaches −33.4 dB at 11.5 GHz at thickness of 2 mm; meanwhile, the optimized effective absorption bandwidth ( E AB ) is 3.9 GHz from 13.6 to 17.5 GHz with a thickness of 1.5 mm. The introduction of HE REBO 3 (RE = Ce, Y, Sm, Eu, Er, Yb) as intermediate phase will give rise to the mismatching impedance, which will further lead to the reduction of reflection loss. Intriguingly, the HEREB 6 /HEREBO 3 still possess wide effective absorption bandwidth of 4.1 GHz with the relative low thickness of 1.7 mm. Considering the better stability, low density, and good EM wave absorption properties, HE REB 6 ceramics are promising as a new type of EM wave absorbing materials.

• Publisher: Tsinghua University Press,Science and Technology on Advanced Functional Composite Laboratory,Aerospace Research Institute of Materials&Processing Technology,Beijing 100076,China%Henan Key Laboratory of Aeronautical Materials and Application Technology,School of Material Science and Engineering,Zhengzhou University of Aeronautics,Zhengzhou 450046,China%Zibo Firststar New Material Incorporated Co.,Ltd.,Zibo 255000,China
• Subject: Borates / Boron carbide / Ceramics / Characterization and Evaluation of Materials / Chemistry and Materials Science / Composites / Crystal structure / Dielectrics / Earth / Electromagnetic absorption / Electromagnetic interference / electromagnetic wave absorbing properties / Entropy / Erbium / Glass / high entropy rare earth hexaborides (HE REB6) / Impedance matching / Materials Science / Nanotechnology / Natural Materials / one-step synthesis / Properties (attributes) / Reduction / Research Article / Structural Materials / synergistic dielectric and magnetic losses / Thickness / wide effective absorption bandwidth / Ytterbium / Yttrium