Nanocrystalline high-entropy hexaboride ceramics enable remarkable performance as thermionic emission cathodes  

作　　者：Mengdong Ma Xinyu Yang Hong Meng Zhisheng Zhao Julong He Yanhui Chu 

机构地区：[1]School of Materials Science and Engineering,South China University of Technology,Guangzhou 510641,China [2]Center for High Pressure Science(CHiPS),State Key Laboratory of Metastable Materials Science and Technology,Yanshan University,Qinhuangdao 066004,China [3]School of Materials Science and Engineering,Hefei University of Technology,Hefei 230009,China

出　　处：《Fundamental Research》2023年第6期979-987,共9页自然科学基础研究（英文版）

基　　金：the National Key Research and Development Program of China(2021YFA0715801);the National Natural Science Foundation of China(51972116 and 52122204);the China Postdoctoral Science Foundation(2021M691051).

摘　　要：The development of high-entropy borides with combined structural and functional performance holds untold scientific and technological potential,yet relevant studies have been rarely reported.In this work,we report nanocrystalline(La_(0.25)Ce_(0.25)Nd_(0.25)Eu_(0.25))B6 high-entropy rare-earth hexaboride(HEReB6-1)ceramics fabricated through the high-pressure sintering of self-synthesized nanopowders for the first time.The as-fabricated samples exhibited a highly dense(96.3%)nanocrystalline(94 nm)microstructure with major(001)fiber textures and good grain boundaries without any impurities,resulting in a remarkable mechanical,electrical,and thermionic emission performance.The results showed that the samples possessed outstanding comprehensive mechanical properties and a high electrical resistivity from room temperature to high temperatures;these were greater than the average values of corresponding binary rare-earth hexaborides,such as a Vickers hardness of 23.4±0.6 GPa and a fracture toughness of 3.0±0.4 MPa•m^(1/2)at room temperature.More importantly,they showed high emission current densities at elevated temperatures,which were higher than the average values of the corresponding binary rare-earth hexaborides.For instance,the maximum emission current density reached 48.3 A•cm^(−2)at 1873 K.Such superior performance makes the nanocrystalline HEReB6-1 ceramics highly suitable for potential applications in thermionic emission cathodes.

关 键 词：High-entropy ceramics HEXABORIDES NANOCRYSTALLINE Mechanical properties Thermionic emission 

分 类 号：TQ174[化学工程—陶瓷工业]