一、前言六硼化镧(LaB_6)的熔点高、硬度大、热和化学稳定,并且具有电子逸出功小、发射率大(电流密度大)、效率高、抗中毒性能好、寿命长、耐离子轰击和适应性强等优点,是一种性能优良的热阴极材料。例如,在回旋加速器中用 LaB_6来代替 Ta 作阴极,寿命由原来的12小时提高到150—180小时。又如,在各类电子显微镜中采用 LaB_6 作阴 I. Introduction LaB 6 has the advantages of high melting point, high hardness, thermal and chemical stability, small electron emission power, high emissivity (high current density), high efficiency, good anti-poisoning performance, long service life, Ion bombardment and strong adaptability advantages, is a good performance of the hot cathode material. For example, using LaB_6 instead of Ta as the cathode in a cyclotron increases the lifetime from the original 12 hours to 150-180 hours. In another example, the use of LaB_6 as cathode in various types of electron microscope