摘要
二元单晶稀土六硼化物(REB_(6))具有丰富的物理性质,其中单晶LaB_(6)具有优异的电子发射特性,影响二元REB_(6)发射性能的物理机理及其他二元REB_(6)是否具有良好的发射特性,需要进一步研究.本文采用基于密度泛函理论的第一性原理计算对典型二元单晶REB_(6)(RE=La,Ce,Pr,Nd,Sm,Gd)的电子结构、功函数进行了理论分析,并对区熔法制备的高质量单晶REB_(6)的热发射性能进行了测试.电子结构计算结果表明,二元REB_(6)费米能级附近具有很高的态密度,宽域分布的稀土元素的d电子决定了REB_(6)优异发射性能的电子态,局域分布的f轨道对发射性能不利.功函数理论计算表明具有d态价电子的二元REB_(6)(RE=La,Ce,Gd)具有较低功函数.热发射测试结果表明,以上单晶REB_(6)(100)晶面功函数热发射测试值与理论计算值基本相符.最终理论计算结合实验结果表明,LaB_(6)和CeB_(6)具有良好的热发射和场发射性能,GdB_(6)具有良好的场发射性能.
Binary rare earth hexaborides(REB_(6)) have different rare earth elements with different valence electron distributions,which lead to different strange physical properties and different emission properties.However,in the electron emission properties,whether PrB_(6),NdB_(6),SmB_(6)and GdB_(6) all have excellent emission properties remains to be further studied,and the physical mechanism affecting their emission properties needs investigating.In this paper,the electronic structures,work functions of typical binary single crystal REB_(6)(LaB_(6),CeB_(6),PrB_(6),NdB_(6),SmB_(6),GdB_(6))are studied by first principles calculations.The single crystal REB_(6) are prepared by optical zone melting method,and their thermionic electron emission properties are tested experimentally.The theoretical calculation results show that the typical binary REB_(6) have large densities of states near the Fermi level.The d-orbitals with broad distributions in conduction bands are beneficial to electron emission.The localized f-orbital electrons in valence bands are not conducive to their electron emission.The theoretical calculations of work functions of typical binary single crystal REB_(6)(100)surface are consistent with the analyses of their electronic structures.The theoretical calculation values of work functions are ordered as GdB_(6)(2.27 eV)<CeB_(6)(2.36 eV)<LaB_(6)(2.40 eV)<PrB_(6)(2.58 eV)<SmB_(6)(2.63 eV)<NdB_(6)(2.91 eV).The experimental test results of thermionic electron emission of single crystal show that the experimental thermionic electron properties are consistent with the theoretical ones.The LaB_(6) and CeB_(6) both have good thermionic and field emission properties,and the GdB_(6) has excellent field emission properties.
作者
刘洪亮
郭志迎
袁晓峰
高倩倩
段欣雨
张忻
张久兴
Liu Hong-Liang;Guo Zhi-Ying;Yuan Xiao-Feng;Gao Qian-Qian;Duan Xin-Yu;Zhang Xin;Zhang Jiu-Xing(School of Materials Science and Engineering,Anyang Institute of Technology,Anyang 455000,China;Key Laboratory of Advanced Functional Materials,Ministry of Education,College of Materials Science and Engineering,Beijing University of Technology,Beijing 100124,China)
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2022年第9期349-355,共7页
Acta Physica Sinica
基金
安阳工学院博士启动基金(批准号:BSJ2021004)
安阳市科技攻关项目(批准号:2021C01GX007)
国家自然科学基金(批准号:11804005)资助的课题。
