JPH04144025A - Impregnation type cathode and its manufacture - Google Patents

Abstract

PURPOSE:To prevent the occurrence of grid emission by press-forming a porous sintered body of a high melting point metal into a form having a recess part in the bottom, and storing an electron emission substance with which the porous sintered body is fusion-impregnated, in a space formed with the recess part and a cup. CONSTITUTION:A cup assembly is composed of a cathode substrate 1 whose bottom part has a recessed form, an Mo-made cup 2, and an electron emission substance storing space part 3 impregnated with an electron emission substance. The cup assembly is manufactured by pressing a W pellett, whose bottom part is formed in a recessed form, in the cup 2, then fusion-impregnation is made with the electron emission substance from the upper surface of the W pellet, and finally a surplus electron emission substance on the surface of the W pellet is dissolvedly removed. This restrains the occurrence of grid emission and obtains an impregnation type cathode having sufficient life.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an impregnated cathode used in an electron tube and a method for manufacturing the same, and particularly relates to an impregnated cathode that can stably ensure a long life and its manufacturing method. Regarding the method.

[Prior Art] Impregnated cathodes used in electron tubes as high current density cathodes are usually made of tungsten (W), molybdenum (M
The cathode substrate is made by impregnating a porous sintered body of a high-melting point metal such as barium-calcium-aluminate (BaO-Ca041.O,) with an electron-emitting substance such as tantalum (Ta), MO, etc. A cup made of melting point metal, Ta,
The cathode sleeve is made of a high melting point metal such as Mo, and the cathode base, cup, and cathode sleeve are assembled by welding, and a single layer film of osmilum (Os), iridium (rr), ruthenium (Ru), etc. is coated on the surface of the cathode base. Alternatively, it is formed by covering with an alloy layer film.

However, with this configuration, the operating temperature is as high as about 1000°C, which poses a major obstacle to practical use.As a method of lowering the operating temperature, for example, as described in JP-A-61-13526, the above-mentioned Os, Ir, In place of a single layer film or alloy layer film such as Ru, scandium (Sc)
Methods of coating oxides have been proposed.

This method lowers the cathode operating temperature by about 15
The temperature can be lowered by 0 to 200°C. However, in this case, in order to obtain a predetermined electron emitting ability, a larger amount of free Ba is required than in the past, and there is a problem that the consumption of the electron emitting material impregnated within the porous sintered body increases. As a means of achieving this, a method has been adopted in which the porosity of the porous sintered body is made larger than before.

[Problems to be Solved by the Invention] However, in the case of the above-mentioned conventional technology, although it exhibits a sufficiently satisfactory electron emitting ability at the initial stage of operation, the consumption of the electron emitting material is large and the grid emission resulting from the vapor deposition of the electron emitting material is high. This leads to an increase in the amount of carbon dioxide, and also has the problem that a sufficient lifespan cannot be obtained.

SUMMARY OF THE INVENTION An object of the present invention is to provide an impregnated cathode that solves the above-mentioned problems of the prior art, suppresses the occurrence of grid emissions, and has a sufficiently satisfactory lifespan, and a method for manufacturing the same.

[Means for Solving the Problems] The above object is to provide an impregnated cathode comprising a cathode substrate in which a porous sintered body of a high-melting point metal is impregnated with an electron-emitting substance, a cup made of a high-melting point metal, and a sleeve made of a high-melting point metal. In the above, the porous sintered body of the high melting point metal is press-molded to have a concave bottom part, and the space formed by the concave bottom part of the porous sintered body and the cup is melted and impregnated with the electrons. The impregnated cathode has a structure in which a released substance is stored, and in its manufacture, a high melting point metal porous body with a concave bottom press-molded is inserted into a high melting point metal cup, or the porous body is After creating a cup assembly by integrally molding the body with a high melting point metal cup material, the surface of the assembly is melted and impregnated with an electron-emitting substance to form a concave bottom part of the porous sintered body and the cup. This can be achieved by employing a manufacturing method in which the electron-emitting substance is stored in a space.

[Operation] By using the impregnated cathode with the above configuration, the electron emitting substance consumed in the porous sintered body during the operation is successively replenished by diffusion from the space storage section, so that a long life can be ensured. can.

Furthermore, by adopting the configuration in which the space storage section is provided, there is no need to increase the porosity of the porous sintered body as in the case of the prior art, and it is possible to suppress evaporation of excess electron-emitting material. As a result, the generation of grid emissions can also be suppressed.

[Example] Hereinafter, the impregnated cathode of the present invention and the method for manufacturing the same will be specifically explained with reference to Examples.

Figure 1 shows an impregnated cathode of the present invention with a porosity of 25%, the bottom of which was press-molded into a concave shape and sintered in a reducing atmosphere.
A cross-sectional view showing a W porous sintered body (W pellet), for example, a=1.2 mm, b=0.5 mm%c==0.6
mm, d=0.4 mm, e=o, 1 mm.

FIG. 2 is a cross-sectional view showing the configuration of a cup assembly made using the above-mentioned porous sintered body, including a cathode base 1 with a concave bottom, a cup 2 made by A○, and an electron-emitting material impregnated with an electron-emitting material. It is shown that it consists of a storage space part 3.

To create the cup assembly, after press-fitting the above-mentioned W pellet with a concave bottom into two MO inner cups, an electron-emitting substance (BaO-CaO, Al, O,) is applied to the W pellet from the top surface of the W pellet.
This was carried out by melting and impregnating an amount twice or more of the allowable amount of pores in the pellet, and then dissolving and removing the excess electron-emitting substance on the surface of the W pellet.

M about the cup assembly created in this way.

Disassemble the cup 2 and observe the concave bottom part of the cathode base 1.
As a result of analysis, it was confirmed that a predetermined ratio of electron-emitting substances was stored. In addition, the W pellets are integrally molded with a Mo plate processed into a cup area! - Exactly the same situation was observed when two-piece assembly was used.

Furthermore, as a result of carrying out a life test by mounting the cathode prepared as described above in an electron tube, it was possible to obtain an electron tube with a lifespan of more than 50,000 hours, compared to the lifespan of about 45,000 hours for conventional cathodes. did it.

[Effects of the Invention] As described above, by using the impregnated cathode and its manufacturing method as the cathode and manufacturing method of the present invention, the problems of the prior art can be solved and grid emissions can be reduced. It has been possible to provide an impregnated cathode that suppresses the occurrence of cathode rays and has a satisfactory lifespan, and a method for manufacturing the same.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the W porous sintered body used in the impregnated cathode of the present invention, and FIG. 2 is a sectional view showing the configuration of a cup assembly made using the porous sintered body shown in FIG. 1. . l...Cathode base, 2...Mo cup, 3...
・Electron-emitting substance storage space 7-a [Figure 1

Claims (1)

[Scope of Claims] 1. An impregnated cathode comprising a cathode substrate in which a porous sintered body of a high-melting point metal is impregnated with an electron-emitting substance, a cup made of a high-melting point metal, and a sleeve made of a high-melting point metal; The porous sintered body of metal is press-molded to have a concave bottom, and the electron emitting substance melted and impregnated is stored in the space formed by the concave bottom part of the porous sintered body and the cup. An impregnated cathode characterized by a 2. In manufacturing an impregnated cathode consisting of a cathode substrate made of a porous sintered body of high melting point metal impregnated with an electron-emitting substance, a cup made of high melting point metal, and a sleeve made of high melting point metal, the bottom part is press-formed into a concave shape. After inserting the high melting point metal porous body into a high melting point metal cup or integrally molding the porous body with a high melting point metal cup material to create a cup assembly,
An impregnated cathode characterized in that an electron-emitting substance is melted and impregnated from the surface of the assembly, and the electron-emitting substance is stored in a space formed by the concave bottom portion of the porous sintered body and the cup. manufacturing method.