JPS59180931A - Cathode body structure for electron tube - Google Patents

Abstract

PURPOSE:To maintain improved stability of electron emission for a long time and to increase the strength of the cathode body structure, by dispersing in a carrier of Mo an oxide or carbide and a dispersion reinforcing agent so that the same form groups of lines, or trains, along the direction of the length with certain train lengths and by bringing the state of the dispersion within specified ranges. CONSTITUTION:An oxide or carbide of one element selected from the group of Ce, Hf, Tb, and so on and a dispersion reinforcing agent including Al, etc. are added to a carrier of Mo and adapted so that each of the added substances is aligned along the direction of the length and a plurality of lines, or trains, of those substances are formed there. On the outermost surface is formed a carbide layer. The content of the oxide or carbide is 1-5wt%, both the grain size and the intergranular distance are less than 2mum, the train length is more than 2.5mum, the train-to-train distance both lengthwise and sidewise are more than 2mum, while the contents of Al, K, and Si are respectively 10-200, 10-300, and 10-200ppm and the thickness of the carbide layer is 1-10% of the total thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] The present invention relates to a cathode assembly for an electron tube, and more particularly to a cathode assembly for an electron tube that has good electron emission characteristics and high high-temperature strength.

[Technical background of the invention and its problems]

The microwave generation source of various microwave electron tubes, such as magnetrons, generally has a cathode structure in the form of a filament, which is made by processing fine wires of a sintered body made of tungsten (W) with thorium oxide and metal oxides dispersed into a spiral shape. It is widely used. When in use, the cathode structure is energized and heated to a high temperature (1500
~1900'C) to emit thermoelectrons.

Now, such a cathode structure is manufactured by applying a powder metallurgy method. That is, a green compact of mixed powder of each component is sintered in, for example, a hydrogen stream to form a sintered body, and this is rolled several times to stretch the crystal grains of each component into a fibrous shape. The wires are arranged and further passed through a wire drawing process to successively reduce the diameter to obtain a thin wire with a predetermined wire diameter. Finally, this thin wire is spirally wound into a filament to form a cathode structure having a predetermined shape.

In this process, a predetermined amount of metal oxides or other compounding components are mixed into a matrix of high melting point metals, each having a certain length in the axial direction of the thin wire, that is, along the processing direction. They will form rows of books and be dispersed. At this time, each row is configured such that a certain compounded component is completely bare at a certain distance and aligned in the axial direction, and there is no possibility that fine powder of other compounded components is mixed in this row.

The length of such a sequence is usually called the alignment length.

On the other hand, the cathode structure has stable electron emission during lighting, high mechanical strength at high temperatures, and no deformation due to its own weight.
Characteristics such as excellent resistance to deformation or cutting due to external forces such as vibration are required.

However, with the development of industry, the characteristics required of the cathode structure have become stricter, and as a result, there is a strong desire to develop a cathode structure that is capable of stable electron emission over a longer period of time and has even better high-temperature strength. It is rare.

[Purpose of the invention]

An object of the present invention is to provide a cathode structure that satisfies the above requirements, has excellent long-term electron emission stability, and has high high-temperature strength.

[Summary of the invention]

The present inventors have conducted intensive research on the type and amount of each component to be dispersed, the state of dispersion, and the correlation with the above characteristics in a cathode structure with Mo as a matrix. Based on the knowledge that this is a characteristic determining factor, we have developed the cathode structure of the present invention.

That is, the cathode structure of the present invention contains cerium (Ce), yttrium (Y), and strontium (
Sr), Calcilla A (Ca), Zil ml = Lam (Z
r), an oxide or carbide of at least one element selected from the group of hafnium (Hf), titanium (Tt), terbium (Tb), and A7. K and S
The dispersion reinforcing agent containing i is contained in a plurality of row groups aligned along the axial direction, and
1゛! ! A cathode structure for an electron tube in which a carbonized layer is formed, the content of oxide or carbide is 1 to 5% by weight, the particle size and the distance between particles are both 2 μm or less,
The alignment length is 2.5 μm or more, the interval between each row in the axial direction and the interval between each row in the direction perpendicular to the axial direction are both 2 μm or more, and the content of Al, K, and St is 10~2001)pm, 10~'30 respectively
0 ppm, 10-20 Qp+pQ, and the thickness of the carbonized layer is 1-10% of the total thickness.

In the cathode structure of the present invention, Mo is the carrier.

And in MO, first of all, Ce, Y, Sr, C
An oxide or carbide of one or more elements of a, ZrHf+Ti, and Tb is dispersed. The total content of these oxides or carbides in the Mo support is 1 to 5 parts by weight. If this content is less than 1% by weight, the electron emission efficiency decreases and practicality is likely to be lost, and if it exceeds 5% by weight, there will be disadvantages such as a sudden decrease in processability. Become.

Furthermore, a predetermined amount of a fractional reinforcing agent containing An, K, and St is dispersed in the Mo carrier. These mainly contribute to improving the high temperature strength characteristics of the cathode structure. In the present invention, Al
is 10-200 ppm, K is 10-300 ppm
, Si must be dispersed at 10 to 200 ppm, and if any of these components is missing, or if the amount of each component deviates from the above numerical range, in any case the cathode It becomes difficult to improve the high temperature strength properties of the structure.

In the cathode structure of the present invention, the compound or carbide and the dispersion strengthening agent are arranged in a plurality of row groups along the axial direction with a certain alignment length, as described above, in the Mo carrier. are formed and dispersed. The greatest feature of the present invention is that this dispersion state has been specified.

First, the state of dispersion of oxides or carbides will be explained.

The grain size of each component arranged in the axial direction within each row is less than 2 μm.
Further, the distance between particles is also 2 μm or less. If the particle size exceeds 2 μm or the distance between fine particles exceeds 2 μm, the high temperature strength decreases.

Each row is composed of only the respective components, and a plurality of them are arranged in the axial direction with a certain alignment length. In the present invention, first, this alignment length is 2.5 degrees or more. If this length is smaller than 2.5 μm, the high temperature strength will be lowered and breakage will be more likely to occur between the rows. Also,
The distance between each row in the axial direction is 2 μm or more, and the distance between other rows adjacent in the direction perpendicular to the axial direction is 2 μm or more.
It is necessary that the number is greater than or equal to m. If any one of the above-mentioned conditions is missing, high-temperature strength tends to decrease.

Next, the content of the dispersion strengthening agent will be explained.

If the content of each dispersion strengthening agent is less than the lower limit of the above-mentioned range, the effect as a dispersion strengthening agent is hardly recognized and the high temperature strength is reduced.

In addition, if each exceeds the upper limit of the above range (
The flexibility decreases, and when processed into a spiral shape, wire breaks and cracks occur, and the high-temperature strength tends to decrease as well.

The cathode structure of the present invention is constructed by forming a carbonized layer of a predetermined thickness on the surface of a material having the above-described structure. The thickness of the carbonized layer must be set within a range of 1 to 10 times the thickness of the cathode structure; if it is less than 1%, the stability of electron emission will decrease; Since the mechanical strength of the cathode structure is reduced, it becomes easily damaged by external forces such as vibration, and furthermore, the shape of the carbonized layer is distorted by rush current at the initial stage of operation, resulting in a significant deterioration of electron emission characteristics.

The cathode groove body of the present invention is manufactured, for example, as follows.

First, A40s, A11c4, Al(NO
3) 3, KCj? .

Kx Si Os or the like is added while adding water to form a slurry, which is stirred and then dried. The amount of each dispersion enhancer used at this time is such that when the cathode assembly is manufactured, the above-mentioned amount of All r K r St is dispersed in the cathode assembly.

This is then heated in a hydrogen stream. Usually the temperature is 80
0-1100'C, heating time 2-4 hours. In this process, each component is reduced, resulting in G, A4, K.

Mo powder is obtained in Si-doped form.

Thereafter, a predetermined amount of fine powder of either oxide or carbide is added to the Mo powder, mixed, and molded to form a green compact.

The green compact is sintered in a hydrogen stream. Sintering temperature is usually 170
The temperature is 0 to 1900°C and the sintering time is 4 to 10 hours. In this process, a sintered body having a specific gravity of 9.4 to 9.7 is obtained.

Next, this sintered body is passed through a rolling-drawing process to form a wire rod of a predetermined wire diameter. In this process, the structure of the sintered body becomes highly dispersed. An area reduction ratio of 60 is preferable.

The obtained wire is processed into a coil shape to form a cathode structure having a predetermined shape. Finally, this is heat treated in a hydrocarbon atmosphere such as toluene or benzene to form a carbonized layer of a predetermined thickness on the surface of the structure. Usually, treatment at a temperature of 1500 to 2000°C for 5 to 30 minutes is sufficient.

[Embodiments of the invention]

The fine powder of MoO2 with an average particle size of 3 μm was analyzed in advance to confirm its purity.Kl'cls, KCA! , to 2 SiO molybdenum powder weight to A6. While adding water, 10°50, 150, and 350 ppm, respectively, in terms of Si, were added to form a slurry, thoroughly stirred, mixed, and then dried with steam. The mixed powder was heated in a hydrogen stream for 10
The mixture was heated and reduced at 00'C for 4 hours. Approximately 3.5 in average particle size
M in μm.

A powder was obtained. Double iB% of ZrO2 powder with a particle size of 0.4 μm or less was added to this Mo powder and mixed for about 6 hours. This green compact was heated to 18% in a hydrogen stream.
Sintering was performed at 50°C for 8 hours. A sintered body with a specific gravity of 9.4 was obtained. The cross-sectional shape of the sintered body is 12 x 12 mm, and the length is 65 mm.
It was my friend.

This sintered body was rolled and drawn into a thin wire with a wire diameter of 0.2y+mφ.

The obtained thin wire was secondary processed into a coil shape according to a conventional method, and the coil was heated to 1700°C in a benzene atmosphere to perform carbonization treatment, and the coil surface was coated with a thickness of 10 μ7 rL (5
%) of carbonized layer was formed.

This cathode assembly was assembled into a power tube (diode) and lit for continuous reading, and the electron emission characteristics at that time were measured.

For comparison, a similar test was conducted on a conventional structure (tungsten containing thorium 182ide).

The horizontal axis shows the continuous lighting time, and the vertical axis shows the relative value of the electron emission characteristics (ratio between the characteristics of the structure of the present invention and the characteristics of the conventional structure).
It is shown in Figure 1, which represents the

Furthermore, the rate of change in the coil spacing when the coil was heated to 1800°C was measured, and the results are shown in FIG. For comparison, similar measurements were also performed on the conventional wire used in the electron emission characteristic test, and the results are also included.

As is clear from FIG. 1, the cathode structure of the present invention exhibits extremely stable electron emission characteristics over a long period of time compared to conventional cathode structures. Moreover, as is clear from FIG. 2, its high temperature strength is high.

〔Effect of the invention〕

The cathode structure of the present invention has significantly improved stability of electron emission characteristics and high temperature strength as compared to conventional cathode structures, and has great industrial value.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the continuous lighting time and the relative value of electron emission characteristics, and FIG. 2 is a curve showing the rate of change in the coil spacing in the coils of the wire used in the examples. curve a
The curve represents the present invention, and the curve represents the conventional (tungsten containing thorium oxide). Completed 1 Jυj (hr) Continued from page 1 0 Inventor Tatsuo Shimizu 72 Horiyomachi, Saiwai-ku, Kawasaki City, Tokyo Shibaura Electric Co., Ltd. Horikawacho Factory

Claims (1)

[Claims] Cerium, yttrium, strontium, calcium, and zirconium in a molybdenum carrier. A plurality of oxides or carbides of at least one element selected from the group of hafnium, titanium, and terbium, and a dispersion strengthening agent containing aluminum, potassium, and silicon are arranged along the axial direction. A cathode structure for an electron tube comprising a group of rows of oxides or carbides and a carbonized layer formed on the outermost surface, the content of oxides or carbides being 1 to 5% by weight. Particle size and interparticle distance are both 2 μm or less, alignment length is 2.5
μm or more, the distance between each row in the axial direction and l1il
The spacing between each row in the direction perpendicular to the fl length direction is 2 μm or more, and aluminum 9. The content of potassium and silicon is 10 to 200 ppm, 1.0 to 300 ppm, respectively.
10 to 200 ppm, and further, the thickness of the carbonized layer is 1 to 10% of the total thickness.