Ce元素固溶掺杂对LaB6阴极材料电子逸出功的影响

Effect of Ce Solid Solution Doping on Work Function of LaB6 Cathode Material

摘要:

大功率电推进技术的发展对低电子逸出功LaB6阴极材料的需求非常迫切。为此，本文采用稀土金属Ce元素固溶掺杂改性LaB6以降低其电子逸出功的策略，先通过熔盐法制备出La1-xCexB6固溶体纳米粉体（x=0.2，0.4，0.6，0.8），后经热压烧结得到La1-xCexB6阴极材料。利用XRD、SEM等技术表征了La1-xCexB6阴极材料的组成结构，并研究了Ce元素固溶掺杂对LaB6阴极材料电子逸出功的影响。结果表明所制备的La1-xCexB6阴极材料为单相固溶体，致密度高，相对密度介于98.49%~98.98%之间。相对于未掺杂LaB6阴极材料，La1-xCexB6阴极材料的电子逸出功更低，且随着Ce掺杂含量增加先减小后增大，整体介于1.85eV~2.54eV之间，其中La0.6Ce0.4B6阴极材料的电子逸出功最低，仅为1.85eV。固溶掺杂Ce元素是降低LaB6阴极材料电子逸出功的有效途径。

Abstract:

The development of high-power space electric propulsion technology has a very urgent requirement of LaB6 cathode material with low work function. In this paper, rare earth Ce was selected as doping element to reduce work function of LaB6. Firstly, La1-xCexB6 solid solution nanopowders（x=0.2, 0.4, 0.6, 0.8）were prepared by a molten salt route, and then they were used as raw materials to fabricate La1-xCexB6 cathode materials by hot pressing sintering. XRD and SEM technology were used to investigate microstructures of La1-xCexB6 cathode materials. The effect of Ce doping on work function of LaB6 cathode material was studied. Results show that the La1-xCexB6 cathode materials fabricated by hot pressing sintering of La1-xCexB6 nanopowders are single phase solid solution, their relative densities range from 98.49%~98.98%. The work functions of La1-xCexB6 cathode materials are between 1.85 eV and 2.54 eV, all lower than that of LaB6 without Ce doping. Besides, work function of La1-xCexB6 cathode materials decreases at first and then increases with Ce content increasing. La0.6Ce0.4B6 cathode material has the lowest work function of 1.85 eV. Solid solution doping of rare earth Ce is an effective way to reduce work function of LaB6 cathode material.