JPH06168661A - Manufacture of impregnation type cathode - Google Patents

Abstract

PURPOSE:To obtain an excellent electron emitting characteristic by mixing high melting point heat resistant metal powder and an emitter agent together in a dry system, sealing this in a capsule after press molding, putting an atmosphere under hydrogen, inactive gas, vacuum or the like when it is processed and sintered by a hot hydrostatic pressure pressurizing method, and specifying a temperature and time. CONSTITUTION:Barium carbonate, calcium carbonate and aluminum oxide being a raw material of an emitter agent are mixed together in a mole ratio of 4:1:1, and it is heated to 1100 deg.C in the atmosphere, and a barium aluminate compound is formed. Next, this emitter agent 10g and tungsten powder 100g are mixed together in a dry system, and rubber press molding is carried out, and a column shape is formed. Afterwards, an obtained compact 11 is housed in a Pyrex glass container 12, and alumina powder 13 is filled here, and the inside is put under vacuum. Afterwards, a glass container 14 obtained by sealing this is put in a processing furnace 15 for hot hydrostatic pressure pressurization, and is sintered for about ten minutes at a processing temperature 1400 deg.C to 1900 deg.C higher than a processing temperature of a pressurization method. In this way, violent reaction when it is made dense is restrained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an impregnated cathode such as a picture tube of a display device which requires a high emission current density.

[0002]

2. Description of the Related Art Impregnated cathodes are devised to further improve the electron emission characteristics of oxide cathodes. As the impregnated cathode, the impregnated replenishment type in which a tungsten (hereinafter referred to as W) porous substrate is impregnated with an electron emitting substance (hereinafter referred to as an emitter agent) is mainly used at present, and for example, USP 4,165,473. No. and USP 3,358,1
It is introduced in detail in No. 78 etc.

In recent years, the inventor has proposed a hot isostatic press (Hot Isostatic P) as an improved version of this impregnation replenishment type.
Manufacturing of a powder-sintered impregnated cathode by a pressing method (hereinafter referred to as HIP) (JP-A-3-55539, USP).
No. 5,096,450).

[0004]

By the way, the above-mentioned HI
The powder-sintered impregnation type cathode by the P method is obtained by dry-mixing high melting point heat-resistant metal powder and an emitter material and press-molding, then vacuum-sealing this molded body, and finally HIP-treating the capsule. It is characterized by being manufactured by sintering.

According to this manufacturing method, by using the HIP method, there is an advantage that the step of sintering the substrate and the step of impregnating the emitter agent can be performed at the same time. Due to insufficient progress of the densification of the base material of the impregnated cathode due to sintering of metal powders, the adhesion between the base metal and the emitter agent is low, which results in barium oxidation in the base metal and the emitter agent during operation of the cathode. There is a problem in that the progress of the thermal decomposition reaction with the substance is delayed and the electron emission characteristics of the impregnated cathode are poor.

On the contrary, when the HIP processing temperature is set high,
The densification of the impregnated cathode base material progresses, and the adhesion between the base metal and the emitter agent increases. As a result, good electron emission characteristics can be obtained.

However, in order to sufficiently densify the impregnated-type cathode base material only by HIP treatment, it is necessary to expose it to a high-pressure atmosphere for a long time (for example, several hours) at a high temperature (for example, about 1500 ° C.). Therefore, during the densification, a reaction between the emitter agent and the W powder remarkably occurs, the emitter agent is excessively consumed, and the initial characteristics are good, but the life is shortened.

Further, there has been a problem that the strength of the impregnated-type cathode base material is remarkably increased due to the progress of densification, which makes it difficult to process into pellets after the HIP treatment.

[0009]

Therefore, in the impregnated cathode of the present invention, a step of dry-mixing W powder and an emitter agent, a step of press-molding the mixed powder, and then encapsulating the molded body,
In a method for manufacturing an impregnated cathode, which comprises a step of HIP-treating a capsule and sintering a mixed powder, a temperature of 800 ° C. or higher 135
A step of sintering the mixed powder by HIP treatment at a HIP treatment temperature of 0 ° C. or lower, and Ir, Os—Ru, W—Sc ₂ O ₃
14 above the HIP processing temperature in a hydrogen, inert gas or vacuum atmosphere during the process of forming a metal film such as
The heat treatment is performed at a temperature of 00 ° C. or higher and 1900 ° C. or lower.

[0010]

[Function] According to the above configuration, 800 ° C. or higher and 1350 ° C.
By performing the HIP treatment for a short time in a relatively low temperature region described below and sintering the mixed powder, it is possible to prevent a significant reaction between the W powder and the emitter agent during the progress of densification.

After the HIP treatment, the temperature is higher than the HIP treatment temperature of 1400 ° C. in hydrogen, an inert gas or a vacuum atmosphere.
Only by heating for a short time at a temperature of 1900 ° C. or lower, the impregnation type cathode base material is densified, and at the same time, the adhesion between the W powder, which is the base metal, and the emitter agent is increased. The electron emission characteristics can be obtained.

At this time, as compared with the conventional method in which the impregnation type cathode base material is densified by HIPing in a high temperature and high pressure atmosphere for a long time, the impregnation type is heated at high temperature for a short time. Since the cathode is densified, the consumption of the emitter agent can be suppressed as much as possible. Therefore, a long-life impregnated cathode can be obtained.

Further, after the HIP processing step, the densification of the impregnated-type cathode base material has not progressed comparatively, so that it is easy to perform the pelletizing process of the cathode between the HIP processing step and the subsequent heat treatment. Can be done.

After that, by performing heat treatment in hydrogen, an inert gas or a vacuum atmosphere, densification of the impregnated cathode progresses more than before the heat treatment, and an impregnated cathode pellet having good emission characteristics is obtained. To be

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a flow chart of the manufacturing process of the impregnated cathode of the present invention.

First, a mixed powder prepared by mixing barium carbonate (BaCO ₃ ), calcium carbonate (CaCO ₃ ), and aluminum oxide (Al ₂ O ₃ ) which are raw materials of the emitter material in a molar ratio of 4: 1: 1, was prepared into the atmosphere. Converted to barium aluminate compound by heating in medium at 1100 ° C.

Next, 10 g of the emitter agent converted into a barium aluminate compound and 100 g of W powder are dry-mixed in step 1 of FIG. 1, and subsequently, in step 2, rubber press molding is performed at a pressure of about 2 ton / cm ^2. , To form a cylindrical shape. The emitter agent is not limited to the barium aluminate compound, and oxides such as BaO, CaO, and Al ₂ O ₃ may be mixed with the W powder in a predetermined ratio.

Next, as shown in FIG. 2, after the molded body 11 is accommodated in a Pyrex glass (registered trademark) container 12, A is placed in the Pyrex glass (registered trademark) container 12.
1 ₂ O ₃ 13 is filled and the inside is evacuated to complete the encapsulation step 3.

Next, a vacuum sealed Pyrex glass (registered trademark) container 14 is housed in a HIP processing furnace 15 as shown in FIG. 3 and subjected to HIP processing according to the temperature rising / pressurization schedule shown in FIG. I got a union. HIP processing condition is 1
It is an argon gas atmosphere under 000 ° C.-10 minutes-1500 atm. This step is the HIP processing step 4.

Further, this sintered body was processed into a predetermined shape in a machining (pelletizing) step 5. The sintered body processed into a predetermined shape was subjected to a heat treatment in a hydrogen stream according to the temperature rising schedule shown in FIG. Heat treatment condition is 1800 ° C-3
Minutes, hydrogen atmosphere. This step is the heat treatment step 6
Is. After the heat treatment step, the pellet surface polishing treatment and the surface cleaning treatment are performed in step 7, and finally, in step 8, an Ir film is formed on the surface of the pellet by sputtering to a thickness of 5000 angstroms, and the next assembling step 9 is performed. Sent to. Table 1 shows electron emission characteristics and lifetime characteristics of various combinations of the HIP processing temperature and the heat processing temperature of the present invention in comparison with the prior art. The symbols are ◎>○> △ in the order of excellent characteristics.

[0021]

[Table 1]

Although it is within the range of HIP processing conditions,
If the IP treatment temperature is less than 800 ° C, it is not good because it does not have the strength for processing into a predetermined shape in the subsequent machining step, and if it exceeds 1350 ° C, the W during sintering is increased.
And the reaction of the emitter agent proceeds remarkably, and the emitter agent is excessively consumed, which is not good. Therefore, the range of HIP processing conditions needs to be 800 ° C. or higher and 1350 ° C. or lower.
Above all, the preferable range of the HIP treatment temperature is 900 ° C. or higher and 1100 ° C. or lower.

Next, within the range of heat treatment conditions after the HIP treatment, if the heat treatment temperature is less than 1400 ° C., the impregnation type cathode base material is insufficiently densified, and if it exceeds 1900 ° C., W Is not good because the reaction with the emitter agent proceeds remarkably and the emitter agent is excessively consumed. Therefore, the range of the heat treatment temperature is preferably 1400 ° C or higher and 1900 ° C or lower, and particularly preferably 1550 ° C or higher and 1800 ° C or lower.

The atmosphere for this heat treatment is effective in an inert gas such as hydrogen or argon, or in a vacuum, but of these, a hydrogen atmosphere in which deterioration of the emitter agent does not easily occur when heated to a high temperature is most preferable.

Although the Ir film was formed in step 8,
s-Ru, may be formed a metal film such as W-Sc ₂ O _3.

[0026]

As described above, 800 ° C. or more and 1350 or more
℃ and a step of sintering the mixed powder by HIP treatment following the HIP treatment temperature, Ir, Os-Ru, during the step of performing a metal film such as W-Sc ₂ O _3, hydrogen, inert gases or, 1400 ° C, which is higher than the HIP processing temperature in a vacuum atmosphere
By heating at a temperature of 1900 ° C. or less, W and the emitter agent react significantly, the densification of the impregnated cathode base material proceeds without excessively consuming the emitter agent, and the W powder as the base metal and the emitter Adhesion with the agent is increased, which makes it possible to obtain an impregnated cathode having good initial characteristics and long-life electron emission characteristics.

Further, after the HIP processing step at the above processing temperature, the densification of the base material of the impregnated type cathode has not progressed relatively, so that the pelletizing process of the cathode can be easily performed.

[Brief description of drawings]

FIG. 1 is a flow chart of a manufacturing process of an impregnated cathode according to the present invention.

FIG. 2 is a sectional view for explaining the encapsulation process of the present invention.

FIG. 3 is a sectional view for explaining a HIP processing step of the present invention.

FIG. 4 is a program showing an example of HIP processing conditions of the present invention.

FIG. 5 is a program showing an example of heat treatment conditions of the present invention.

[Explanation of symbols]

 1 Dry Mixing Process 2 Press Molding Process 3 Encapsulation Process 4 HIP Treatment Process 5 Machining Process 6 Heat Treatment Process 8 Ir Sputter Film Forming Process 11 Molded Body 12 Pyrex Glass Container 13 Alumina Powder 14 Vacuum Pyrex Glass Container 15 HIP processing furnace

Claims (4)

[Claims] 1. A step of dry-mixing W powder and an electron emitting substance containing a compound of Ba, a step of press-molding the mixed powder and encapsulating a molded body, and sintering the mixed powder by HIP treatment of the capsule. In a method for manufacturing an impregnated cathode including a step, after the step of sintering the mixed powder by HIP treatment,
A method for manufacturing an impregnated cathode, comprising a step of performing heat treatment at a temperature higher than the treatment temperature. 2. The method for producing an impregnated cathode according to claim 1, wherein the atmosphere for the heat treatment is hydrogen, an inert gas, or a vacuum. 3. The HIP processing temperature is 800 ° C. or higher and 1350 ° C.
The heat treatment temperature after the HIP treatment is 1400 ° C.
The method for producing an impregnated cathode according to claim 1, wherein the temperature is 1900 ° C. or lower. 4. The step of heat treatment is Ir, Os-Ru, W.
Method for producing impregnated cathode according to claim 1, characterized in that before the step of forming a metal film such as -sc ₂ O _3.