Synthesis of novel high-entropy diborides with high-efficiency electromagnetic wave absorption and excellent thermal stability

Abstract

Ceramic materials have obvious advantages in thermal stability, but impedance mismatch limited their ability to attenuate electromagnetic (EM) waves. Herein, a novel series of high-entropy (V_0.2Nb_0.2Zr_0.2Ta_0.2X_0.2)B₂ (X=Mo, Ti, Hf) ceramics were successfully and rapidly synthesized using the ultrafast high-temperature sintering (UHS) method based on joule heating. The results indicated that the effect of high-entropy component control on the magnetic loss of the system was relatively small, but the effect on the dielectric loss was larger. Among them, the HEB-Ti sample demonstrated superior absorbing properties, attributed to its relatively moderate dielectric loss and optimal EM impedance matching. At the same time, because of its relatively moderate attenuation constant, it can achieve the maximum penetration of EM wave and the minimum reflection after absorbing wave. As a result, the minimum reflection loss (RL_min) was as low as –40.7 dB, and the effective absorption band covered the entire low frequency range from 2 to 8 GHz. Its excellent absorption performance was mainly due to the synergistic effect of various dielectric attenuation mechanisms, including defect polarization, dipole polarization, and conduction loss. Furthermore, thermogravimetric (TG) analysis showed that the sample exhibited excellent thermal stability and could withstand up to 550 °C in air and up to 1000 °C in argon gas environment. The relevant work provided meaningful references for the design of new high-performance ceramic wave-absorbing materials.