JPH0221532A - Oxide cathode for electron tube - Google Patents

Abstract

PURPOSE:To make it possible to obtain an oxide cathode for electron tube of an even electron emitting capacity without unevenness between lots by adding a specific amount of barium strontium carbonate to coated particles covered with nickel. CONSTITUTION:To coated particles(CP) 1 made by covering the particle surfaces of a barium strontium carbonate which is an electron emitting substance with several to a dozen mum of nickel, 1% to 50% of barium strontium carbonate particles 2 are added. As a result, after the cathode is resolved, sufficient barium strontium carbonate 12 can be exposed on the cathode surface. Consequently, anti-gas-poisoning property and a stability between production lots can be obtained.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an oxide cathode for an electron tube.

[Conventional technology]

Conventionally, coated particle cathodes (hereinafter referred to as CPC), in which coated particles (hereinafter referred to as CP) in which barium strontium carbonate particles are coated with nickel to a thickness of several to ten-odd microns, are coated on a nickel substrate. It is possible to obtain a large amount of electron emission compared to an oxide cathode.

CP is obtained by bubbling nickel gas obtained by reducing nickel carbonate into a solution of barium strontium carbonate and amyl acetate while stirring.

After the CP is applied to a nickel substrate, it is cathodically decomposed in vacuum, ie, heated to about 900 to 1000°C. By heating, barium strontium carbonate is decomposed into carbon dioxide gas and barium strontium oxide.6 The generated carbon dioxide gas breaks through the covering nickel layer and is released.

Therefore, in the CPC after cathodic decomposition, barium strontium oxide is partially covered with a nickel layer and arranged on a nickel substrate.

[Problem to be solved by the invention]

In the conventional CPC described above, part of the surface of barium strontium oxide particles that emit electrons is coated with nickel. Therefore, compared to an oxide cathode, it has a smaller effective surface area that can emit electrons, so it has the disadvantage of being susceptible to gas voisoning.

Furthermore, due to problems in manufacturing CP, it is difficult to control the thickness of the nickel coating. This makes it difficult to secure the above-mentioned effective surface area capable of emitting electrons without variation between lots, and there is a drawback that it is difficult to obtain a CPC with uniform electron emitting ability.

SUMMARY OF THE INVENTION An object of the present invention is to provide an oxide cathode for an electron tube that has uniform electron emission ability without lot-to-lot variation.

[Means to solve the problem]

The present invention provides an oxide cathode for an electron tube in which an electron emitting material is coated on a nickel substrate. % barium strontium carbonate particles are added.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a partial sectional view of an embodiment of the present invention before the cathode is disassembled.

As shown in FIG. 1, 1 is CP, and the surface of barium strontium carbonate particles is coated with nickel. 2 is barium strontium carbonate particles, relative to the total coating weight,
It accounts for 20%. 3 is a nickel substrate, and nickel contains about 0.1% of an activator such as zirconium or magnesium. Note that the coated material is shown enlarged relative to the cathode substrate.

FIG. 2 is a partial cross-section of an embodiment of the present invention after the cathode is disassembled.

As shown in FIG. 2, 11 is CP after cathode decomposition, and a part of the surface of barium strontium oxide particles is coated with nickel. 12 is barium strontium oxide. 3 is a nickel substrate.

On the surface of the cathode after cathode decomposition, barium strontium oxide particles whose surfaces are partially coated with nickel and barium strontium oxide particles whose surfaces are not coated with nickel coexist. The amount of barium strontium carbonate particles not coated with nickel is suitably 1% to 50% of the total coating weight. This is because if the amount added is less than 1%, it is difficult to ensure electron emission ability with little variation between lots, and gas voisoning resistance is not improved. On the other hand, if it exceeds 50%, high electron density operation at high temperatures cannot be achieved.

In practice, the cathode operating temperature is determined by the emission current density and lifetime required of the cathode, and from these, the amount of barium strontium carbonate to be added can be determined in the range of 1% to 50%.

〔Effect of the invention〕

As explained above, the present invention provides CP with 1% to 50%
By adding barium strontium carbonate particles, sufficient barium strontium oxide can be exposed on the cathode surface after cathode decomposition, so it has excellent gas voisoning resistance and stable electron emission characteristics can be obtained from production lot to production lot. There is an effect that can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of an embodiment of the present invention before the cathode is disassembled, and FIG. 2 is a partial sectional view of the embodiment of the present invention after the cathode is disassembled. 1... CP (coated particle), 2... Barium strontium carbonate, 3... Nickel substrate, 1
1...CP (coated particle), 12...
Barium strontium oxide.

Claims (1)

[Claims] In an oxide cathode for an electron tube in which an electron emitting material is coated on a nickel substrate, the electron emitting material is coated with 1% of nickel on the surface of barium strontium carbonate particles with a thickness of several microns to more than ten microns.
An oxide cathode for an electron tube, characterized in that barium strontium carbonate particles are added in an amount of 50% to 50%.