TWO-LAYER DISPENSED CATHODE AND METHOD OF ITS MANUFACTURING Russian patent published in 2020 - IPC H01J9/04 

FIELD: electronic equipment.

SUBSTANCE: invention relates to electronic engineering, particularly to dispensed cathodes (DC) of microwave electronic devices with increased service life and reliability. Two-layer porous sponge with different layer density is installed in end part of dispensed cathode made in the form of housing from refractory metal (molybdenum). Primary emitting layer of sponge with density of 78–80 % consists of tungsten powder with grain of 1–2 mcm or mixture of powders (20 % of osmium, iridium or rhenium and 80 % of tungsten with grain of 1–2 mcm) and impregnated with an active substance of the composition having an evaporation rate lower than the rate of evaporation of the feed layer (e.g. 5BaO3CaO2Al₂O₃). Feeding layer of sponge with density of 60–65 % consists of tungsten powder with grain of 4–8 mcm and impregnated with active substance having evaporation rate higher than evaporation rate of main layer (for example, with composition 3BaO0.5CaOAl₂O₃). Outside the sponge is coated with metal or mixture of platinum group metals (for example, film composition Os+Ir+Al). Besides, the technical result is achieved by the fact that in the method of producing a dispensed cathode, which includes forming a housing from refractory metal and a tungsten sponge, compositions for preparing layers of a refractory matrix are initially prepared: a main emitting layer, which has powder of tungsten with grain of 1–2 mcm or mixture of powders (20–50 % of osmium, iridium or rhenium and 80–50 % of tungsten with grain of 1–2 mcm), and an uptake layer of tungsten powder with grain of 4–8 mcm. First, the main layer is pressed in a mold for making double-layer cathodes at a pressure which provides density of 78–80 %, after which the backing layer is pressed therein at pressure which provides density of 60–65 %. After sintering of the obtained two-layer jaw, first the impregnating layer is impregnated with an active substance having an evaporation rate higher than the rate of evaporation of the active substance of the main layer. Then the main layer of the sponge is impregnated with an active substance having an evaporation rate lower than the rate of evaporation of the active substance of the feeding layer. After that, double-layer sponge is processed mechanically and fixed in molybdenum housing by means of soldering, its mechanical conditioning is performed together with housing and metal film or mixture of platinum group metals is applied on emitting surface.

EFFECT: increased durability of a dispensed cathode.

4 cl