JPH0360135B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a heated cathode in which an amorphous emitter layer made of a material containing a metal oxide with excellent electron emissivity is deposited on a cathode substrate.

As shown in Figure 1, heated cathodes conventionally used in vacuum tubes, discharge tubes, electron guns, etc. have a small work function and are resistant to wear due to ion bombardment in order to have good electron emission performance and ion impact resistance. A so-called oxide cathode is formed by fixing a material made of metal oxides such as oxides of rare alkaline earth metal elements, oxides of alkali metal elements, or oxides of rare earth elements on the cathode substrate 2 as an emitter layer 3. It is widely used. For example, in the case of alkaline earth metal elements such as barium (Ba), strontium (Sr), and calcium (Ca), from the viewpoint of handling and storage, it is necessary to use single or binary elements that can be maintained in a stable state in the air. Carbonate {BaCO ₃ , (Ba・Sr)
CO ₃ , (Ba・Sr・Ca)CO ₃ etc.} in the form of cathode substrate 2
The above carbonate is heated to a thermal decomposition temperature (1000 to 1300
decompose by raising the temperature to
Oxides {BaO, (Ba・Sr)O, (Ba・
Sr.Ca)O, etc.} was sintered on the cathode substrate 2 to form the emitter layer 3.

However, the emitter layer 3 of the heating cathode 1 described above
Because it has a structure in which metal oxide particles are simply physically bonded, it has poor mechanical strength, and even though it uses materials that are resistant to ion bombardment, it tends to spatter due to electrons and ions. As a result, the life of an electron tube incorporating this kind of electrode 1 has been shortened. Further, since the emitter layer 3 is porous, the many irregularities on its surface cause spark generation due to electric field concentration at high voltage.

Further, the above-described emitter layer forming method has problems such as the need to separately prepare a step of decomposing carbonate to form an oxide, and a high-frequency heating device and a power supply device used in this step.

The present invention has been made to solve the above problems, and includes oxides of alkaline earth metal elements, oxides of alkali metal elements, and rare earth metal elements, which are emitter materials with a small work function and less wear due to ion bombardment. One or more metal oxides selected from the oxide group of elements are introduced into the cathode in a state that can fully demonstrate the characteristics of the emitter material, and it has excellent electron emission and spatter resistance, and does not generate sparks even when high voltage is applied. An object of the present invention is to provide a method for manufacturing a heated cathode that is easy to manufacture, which makes it possible to provide a heated cathode that does not generate , and also does not require a high-temperature heating process and therefore does not require a special device for high-temperature heating. purpose.

That is, in the method for producing a heated cathode of the present invention, one or more organic metals selected from the group consisting of alkoxides and carboxylates of metals containing an alkaline earth metal element, an alkali metal element, or a rare earth element is placed on a cathode substrate. By depositing a material containing the organic metal and heating it at a temperature above the decomposition temperature and below the crystallization temperature of the organic metal, the organic metal is decomposed to form oxides of alkaline earth metal elements and oxides of alkali metal elements. The main feature is that an amorphous emitter layer containing one or more metal oxides selected from the group consisting of rare earth element oxides and rare earth element oxides is formed on the cathode substrate.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 2 is an enlarged sectional view showing the structure of an emitter layer deposited on a cathode substrate of a heated cathode according to an embodiment of the present invention.
2 is a cathode substrate, and 3 is an amorphous emitter layer formed on the cathode substrate 2. The cathode substrate 2 is made of a conventionally used cathode material such as iron (Fe), nickel (Ni), chromium (Cr), dungsten (W) or an alloy thereof, and the emitter layer 3 is made of a rare earth element. It is formed from lanthanum chromate (LaCrO ₃ ), which is a metal oxide containing oxides.

This emitter layer 3 is made of chromium propionate.
1.7% by weight and 3.6% by weight of lanthanum propionate
and butyl acetate or butyl alcohol 84.7% by weight
and 10% by weight of cetyl alcohol to form a liquid, which is deposited on the cathode substrate 2 and heated, thereby decomposing the alkoxides of chromium and lanthanum to form chromium (Cr) and lanthanum (La). An amorphous adhesion layer made of lanthanum chromate (LaCrO ₃ ), which is a composite metal oxide, is formed on the cathode substrate 2.
However, the thermal decomposition temperature of the organic metal mentioned above is
A temperature of 100° C. or higher and lower than the crystallization temperature is sufficient, and the working temperature (400 to 600° C.) in the sealing process of an electron tube incorporating the heated cathode of the present invention can be utilized. The emitter layer of lanthanum chromate (LaCrO ₃ ) formed by the above structural method has a high melting point of 2500° C. or higher, and is amorphous, so it has excellent ion impact resistance.

The metal oxide material forming the emitter layer is
Not limited to the above lanthanum chromate,
Other typical examples include BaO, MgO,
SrO etc. (oxides of alkaline earth metal elements),
Cs ₂ O, Na ₂ O, K ₂ O, etc. (oxides of alkali metal elements), CeO ₂ , Y ₂ O ₃ , Gd ₂ O _3, etc. (oxides of rare earth elements), BaO, SrO, etc. (alkali earth (composite oxides of metal elements), BaO, La ₂ O _3, etc. (composite oxides of alkaline earth metal elements and rare earth elements), CsO, LaO, etc. (composite oxides of alkali metal elements and rare earth elements),
Examples include BaO, Al ₂ O ₃ , etc. (complex oxides of alkaline earth metal elements and non-emitter metal elements). These metal oxides include, for example, a mixture of 2 to 10% by weight of barium octylate, 5% by weight of turpentine oil, 75 to 83% by weight of kerosene, and 10% by weight of cetyl alcohol (for BaO layer formation, liquid), barium lauryl oxide, Mixture of 2 to 10% by weight of octyl alcohol, 65 to 77% of octyl alcohol, 1 to 5% of glycerol stearate and 20% of decyl alcohol (for BaO layer formation, paste form), 10% of magnesium caprate and butyl alcohol 81.5
Mixed with 8% by weight of stearyl alcohol and 0.5% by weight of propyl cellulose (for MgO layer formation, liquid), 1.65% by weight of barium butyrate, 1.17% by weight of strontium propionate, 94.18% by weight of butyl alcohol, and 3% by weight of cetyl alcohol. (For BaO/SrO layer formation, liquid), 3% by weight of barium butyrate, 8% by weight of lanthanum butyrate, 75% by weight of butyl alcohol, and 10% by weight of cetyl alcohol.
and 4% by weight of stearic acid (BaO・
(for Al ₂ O ₃ layer formation, liquid) or 4% barium octylate, 5% aluminum butyrate, 60% octyl alcohol, 20% kerosene, 5% lauryl alcohol, 5% cetyl alcohol, and glycerol stair rate 1
% by weight (for forming _three layers of BaO/Al ₂ O, in paste form) and deposited on the cathode substrate 2 by spraying, dipping, coating, printing, or other means, and applying it during the manufacturing process of the electron tube. It is obtained by decomposing the organic metal using temperature (400 to 600°C), and is deposited on the cathode substrate 2.

As explained above, according to the present invention, a compound selected from the group consisting of alkoxides and carboxylates of metals containing alkaline earth metal elements, alkali metal elements, or rare earth elements, which have a small work function and less wear due to ion bombardment. By thermally decomposing a material containing one or more organic metals at a temperature above its decomposition temperature and below its crystallization temperature and depositing it on the cathode substrate as an amorphous emitter layer, a dense material with strong interparticle bonding strength is created. Since an emitter layer can be obtained, which has excellent electron emission properties and spatter resistance, and the surface of the emitter layer is uniform and smooth, a heated cathode that does not generate sparks even at high voltages can be obtained.

Furthermore, according to the manufacturing method of the present invention, the metal alkoxides or carboxylates can be decomposed into metal oxides at the working temperature in the manufacturing process of electron tubes, so there is no need for a high-temperature heating process or special heating. No equipment or power supply is required, so the heated cathode can be manufactured easily.

[Brief explanation of drawings]

Figure 1 is an enlarged sectional view showing the structure of an emitter layer formed on the cathode substrate of a conventional heated cathode;
The figure is an enlarged sectional view showing the structure of an emitter layer formed on a cathode substrate of a heated cathode according to an embodiment of the present invention. 1... heating cathode, 2... cathode substrate, 3... emitter layer.

Claims (1)

[Claims] 1. A material containing one or more organic metals selected from the group consisting of alkoxides and carboxylates of metals containing alkaline earth metal elements, alkali metal elements, or rare earth elements is deposited on the cathode substrate. let me,
By heating this at a temperature higher than the decomposition temperature of the organic metal and lower than the crystallization temperature, the organic metal is decomposed to form oxides of alkaline earth metal elements, oxides of alkali metal elements, and oxides of rare earth elements. A method for manufacturing a heated cathode, comprising forming an amorphous emitter layer containing one or more metal oxides selected from the group consisting of: on the cathode substrate. 2 1 to 50% by weight of one or more organic metals selected from the group of alkoxides and carboxylates of metals containing alkaline earth metal elements, alkali metal elements, or rare earth elements, and alcohols, esters, aldehydes, carboxylic acids, and ketones. 5 to 95% by weight of one or more organic solvents selected from the group of hydrocarbons and terpenes, and a higher boiling point substance such as a higher alcohol,
Glyceride, polyhydric alcohol with a boiling point of 150°C or higher and 400°C or lower, paraffin, vaseline, lanolin, rosin, cellulose-based polymer compounds, carboxylic acids with 8 or more carbon atoms, polyester, polyaldehyde,
One or more substances selected from the group of polyalcohols, polyethers, polyamide polymers, amino acids, and glycidol are mixed to form a liquid or paste, and this is deposited on the cathode substrate to decompose the organic metal. The organic metal is decomposed by heating at a temperature higher than the crystallization temperature and lower than the crystallization temperature to produce one or more types selected from the group consisting of oxides of alkaline earth metal elements, oxides of alkali metal elements, and oxides of rare earth elements. 2. The method of manufacturing a heated cathode according to claim 1, further comprising forming an amorphous emitter layer containing a metal oxide on the cathode substrate.