METHOD OF MAKING A BORIDED DISPENSER CATHODE

摘要

A method of making a boride dispenser cathode comprising a metallic base material containing an emissive material in the form of a metal oxide which is reduced continuously during operaion of the cathode and the resultant metal diffuses to the surface to form thereat a monoatomic film, comprises the steps of: (A) cleaning the cathode by annealing it in a hydrogen containing atmosphere; (B) depositing boron on the cathode by heating the cathode to a temperature substantially in the range 600 to 700 deg.C in an atmosphere containing a gaseous boron-hydrogen compound or vapour of a boron- hydrogen compound; and (C) forming a boride of the metallic base material by heating the cathode to its operating temperature in a vacuum or a non-reactive atmosphere and maintaining said temperature for a time period.