GB311705A - Process for the manufacture of oxide cathodes for discharge tubes - Google Patents

Abstract

311,705. Vereinigte Gl³hlampen und Electricitõts Akt.-Ges. May 14, 1928, [Convention date]. Vacuum tubes.-Deposition of an alkaline earth oxide on the unoxidized core of a cathode is effected by the simultaneous production in the evacuated container of the alkaline earth metal and the necessary oxygen, the cathode being afterwards heated to a temperature of from 1000‹ to 1500‹C. As material for the core, a refractory metal, such as tungsten, molybdenum or tantalum, is employed. In carrying out the invention, a compound or mixture which will produce, on heating, the required metal, or a mixture of metals, and also one which will evolve oxygen are applied, before assembly, to the side of the anode facing the cathode. After assembly and evacuation, heat is applied to the anode, the evolved metal vapour and oxygen combining to form oxide which is deposited on the cathode. For the production of the metal, a mixture of oxide and magnesium may be employed and, for the oxygen, manganese or barium peroxide or a mixture of these compounds. The materials for these purposes must be such as to evolve no deleterious vapours at the working temperature. The process is applicable to cores, such as platinum or platinum-iridium, which do not form oxides, or to an alloy of platinum and nickel. Preferably, a tungsten core is employed on which barium oxide is deposited.