Abstract:The ion implanting method has been taken for implanting lanthanum ions into the surface layer of molybdenum wires in order to study the function of carbide layer on the surface of La₂O₃-Mo cathode in the emission. The function mechanism has been discussed by using XPS and AES methods. The results show that the carbide layer mainly acts as a reduction reagent to produce metallic lanthanum. Moreover, it can store the activator substance and carry them to the surface. Based on the research results, the carbonization technique has been changed. By applying the new technique, the lifetime of the La₂O₃-Mo cathode has been improved from 14 h to more than 1 000 h—the minimum lifetime for practical uses.

Key words:   carbide layer; La₂O₃-Mo cathode; reduction; lifetime