A method for the preparation of the oxide cathode of an electrical discharge roehre to the invention and prepared in accordance with this method the present invention to its discharge roehre

摘要

642,755. Cathode materials and processing. PHILIPS ELECTRICAL, Ltd. Nov. 10, 1947, No. 29854. Convention date, Nov. 13, 1946. [Class 39 (i)] In the manufacture of oxide cathodes, a carrier is coated, before being placed in the discharge tube, with one or more alkaline earth metals, and with a protective metal layer, e.g. copper, which will form with the first layer a eutectic during the subsequent oxidizing process wherein the carrier is heated to about 800‹ C. during oxidation and final activation in a vacuum. Barium and strontium in proportions of 3 : 2 are vaporized in a vacuum on to a nickel cap to produce a layer a few microns thick. A copper layer, 2 microns thick, is then formed by vaporization, or deposition in a rare gas, and the cathode is heated in oxygen at 0.015 mms. slowly to 800‹ C. to form an oxide layer containing copper. After a few minutes the oxygen is pumped out and the temperature maintained at 820 C. for 24 hours. It is stated that, during operation, copper is in part vaporized on to other parts of the discharge tube and in part absorbed below the oxide layer.