METAL CATHODE FOR ELECTRON TUBE

摘要

PURPOSE: A metal cathode is provided to reduce the manufacturing cost and obtain a high density current by lowering the work function of the surface of the cathode in a less complicated manner. CONSTITUTION: A metal cathode comprises a heater; a sleeve embedded with the heater; a metal emitter disposed on the top of the sleeve and made of a binary alloy containing a platinum(Pt) and alkali earth metal; and a top layer made of only a platinum and formed on the metal emitter. The binary alloy contains Pt and Pt5Ba. The surface of the binary alloy is treated by an aqua regia solution so as to remove only Pt5Ba from the binary alloy, thereby making it possible to form the top layer made of only a platinum. The alkali earth metal is one or more metals selected from a group consisting of a barium, strontium, calcium and a magnesium.