Six-principal-component high-entropy IVB–VB diborides: Low-temperature synthesis, microwave absorption, and mechanisms

Abstract

Owing to their outstanding performances significantly superior to that of the low- and medium-entropy counterparts, high-entropy diborides attracted extensive attention. Nevertheless, the rising configuration entropy of high-entropy diborides rendered not only the better performances but also the greater formation difficulty due to the strengthened sluggish-diffusion effect. Herein, high-entropy (Hf_0.167Zr_0.167Ti_0.167Ta_0.167Nb_0.167V_0.167)B₂, as the first reported six-principal-component high-entropy IVB–VB transition-metal diborides, was successfully synthesized by a microwave and molten-salt co-assisted thermal-reduction method, under the temperature conditions (1400°C/20 min) remarkably milder than that required by the conventional method for synthesizing high-entropy diborides. More importantly, the as-synthesized high-entropy diboride powders exhibited high composition uniformity, single-crystalline nature and hexagon-platelet-like morphology. Furthermore, the high microwave absorption performance of high-entropy (Hf_0.167Zr_0.167Ti_0.167Ta_0.167Nb_0.167V_0.167)B₂ was demonstrated to be favorable for enhancing its synthesis and self-assembly by producing a unique micro-zone hot-spot effect. This research was predicted to promote the development of synthetic technique and dramatically expand the membership of high-entropy materials.