掺杂和复合稀土六硼化物的研究进展

Research Progress on Doped and Composite Rare Earth Hexaboride

稀土六硼化物(rare earth hexaboride,REB_(6))作为热电子发射阴极材料已经应用于各种电子发射器件中,技术的发展对REB_(6)单晶阴极材料的电子发射和力学性能提出了更高的要求.掺杂稀土元素能改善发射性能,加入过渡族金属二硼化物(transition metal boride,TMB_(2))形成共晶复合材料可以提高力学性能.采用区域熔炼法制备的掺杂REB_(6)单晶和REB_(6)与TMB_(2)定向凝固共晶复合材料都是极具应用前景的大尺寸阴极材料.首先,总结了二元REB_(6)的晶体结构和热发射性能,包括晶体取向和稀土元素对REB_(6)单晶热发射性能的影响.然后,综述了掺杂和复合REB_(6)的研究进展,重点总结了材料的性能,从实验和计算结果出发探讨了影响性能的因素.

As thermionic emission cathode material,rare earth hexaboride(REB_(6))has been used in various electron emitting devices.As technologies have developed,the requirements for the electron emission and mechanical properties of REB_(6) single crystal cathode materials have increased.Doping with rare earth elements can improve the emission properties of the material.The mechanical properties of REB_(6) single crystal can be effectively improved by adding high elastic modulus transition metal boride(TMB_(2))into REB_(6) to form the REB_(6) matrix-TMB_(2) fiber directionally solidified eutectic composite.Therefore,both doped REB_(6) single crystal and REB_(6)-TMB_(2) directionally solidified eutectic composite,which are prepared by floating zone melting,are large-size cathode materials with great application prospects.In this paper,the crystal structure of REB_(6) was presented and its influence on the properties was discussed.Then,the thermionic emission properties of binary REB_(6) single crystal were summarized,including the effects of crystal orientation and rare earth elements on the thermionic emission properties.The research progress of doped and composite of REB_(6) were reviewed,the properties of the materials were summarized,and the factors affecting the properties were discussed.