JPH0574551B2 - - Google Patents

Description

[Detailed description of the invention] [Field of application of the invention] The present invention relates to a method for connecting oxide superconductors.

[Conventional technology]

Conventionally, metal materials such as Nb-Ge (eg, Nb ₃ Ge) have been used as superconductors. Since this material is a metal, it has high ductility, malleability, or bendability.
It can be used as a superconducting magnet coil or a power storage coil.

However, this metal superconductor has a small Tc (superconducting critical temperature is hereinafter referred to as Tc) onset;
It was only 23K or less.

On the other hand, when considering industrial applications of superconductors, it is extremely important that this Tc is 100K or higher and that Tco (the temperature at which electrical resistance becomes zero) is 77K or higher.

Recently, copper oxide ceramic materials (hereinafter referred to as oxide superconducting materials or oxide superconductors) have attracted attention as such superconductors. However, this oxide superconductor has the disadvantage that it has poor ductility, malleability, and bendability, and in addition, it is extremely difficult to process and connect it after molding.

[Problem to be solved by the invention]

An object of the present invention is to provide a method for bonding and connecting oxide superconducting materials, which is a problem when applying oxide superconductors, while maintaining superconducting properties.

[Means to solve the problem]

The present invention solves the above-mentioned problems, and provides a method for connecting a first oxide superconductor and a second oxide superconductor, comprising: a powder of a third oxide superconductor; a step of mixing a starting material with a paste to produce a mixture; a step of using the mixture to bring the first oxide superconductor and the second oxide superconductor into close contact at a connection portion; and an oxidizing atmosphere. A method for connecting superconductors, comprising: a step of firing the mixture to impart superconductivity to the connection portion and removing paste from the mixture; and a step of slowly cooling after the step.
The main points are as follows.

As the superconductor used in the present invention,
(A _1-x Bx)yCuzOw x=0~1.0, y=2.0~
4.0 preferably 2.5-3.5, z=1.0-4.0 preferably
Copper oxide ceramics having a molecular structure of 1.5 to 3.5, w=4.0 to 10.0, preferably 6.0 to 8.0 can be used.

In the above molecular formula, A is one or more selected from group a in the periodic table of elements, such as Y (yttrium) or other lanthanoids, and B is one or more selected from elements in group a of the periodic table. Types include, for example, Ba (valium).

In the oxide superconductor used in the present invention, elements other than those mentioned above can be added to A and B.

In the present invention, in order to connect oxide superconductors, materials to become oxide superconductors or their starting materials are mixed or combed into a paste to prepare a mixture, and this mixture is used to connect oxide superconductors. That is.

After the above-mentioned mixture is used to closely connect the oxide superconductors at their joints, this is heated and fired in a high-temperature oxidizing atmosphere, for example, oxygen at a temperature of 700 to 1000°C.

In this firing process, the organic paste is oxidized and combined with oxygen in the atmosphere to become carbon dioxide, moisture, etc. and removed from the connection portion.

In the present invention, as described above, the paste that plays an important role in connecting oxide superconducting materials is removed in the firing process, so it is possible to eliminate the influence of the paste on the superconducting properties after the connection is completed. Therefore, it has the advantage that the selection of the paste and the mixing ratio of the paste and the oxide superconductor powder or its starting material are not so severe.

For the paste, propylene glycol, octyl alcohol, peptyl alcohol, etc. can be used, but there is no particular limitation as long as it can be removed during the baking process.

The purpose of slow cooling after the firing step is to prevent cracks from occurring due to rapid cooling, and to effectively incorporate oxygen into the oxide superconducting material.

"Operation" Powder of oxide superconducting material or its starting material is mixed with paste, this mixture is used to connect oxide superconductors with each other, and further, in the firing process, the oxide superconductor is made to have superconductivity, and By oxidizing and vaporizing the paste, electrical connection between oxide superconductors can be made while maintaining superconductivity.

Examples using the present invention will be shown below.

[Example 1] This example is an example in which linear oxide superconductors are connected using the connection method of the present invention.

In this example, in (A _1-x Bx)yCuzOw,
In order to make A=Y, Y ₂ O ₃ is used as a raw material,
In order to make B = Ba, BaCO ₃ is used as a raw material,
Additionally, CuO was used as a raw material to introduce Cu.

Then, using the above raw materials (Y ₁ Ba ₂ )Cu ₃ O ₆ ~
A starting material for an oxide superconductor having a composition ratio shown by ₈ was prepared.

The above materials are manufactured by Kojundo Kagaku Co., Ltd.
99.9% or more was used.

The blended material was made into tablets by pressurizing it to a pressure of 50 kg/ ^cm2 , then heated to 700℃ for 3 hours, and then heated to 900℃ for 3 hours.
Temporary firing was performed in the air for 10 hours. Furthermore, these are crushed again so that the average particle size is 100μm or less, for example 1~
The thickness was set to about 10 μm.

An oxide superconductor is produced using the starting material produced as described above.

First, in order to form a linear oxide superconductor,
A hollow support made of an organic resin (also referred to as an organic substance) having an air core or a space inside is used, and the inside of this hollow support is filled with a solution obtained by mixing, melting, or gelling an oxide superconducting material or its starting material.

Next, the entire hollow pipe is heated and dried to vaporize and remove the entire liquid component of the solvent. This is heated in oxygen and fired, and the organic resin with an air core or an internal space is vaporized and removed as carbon dioxide, moisture, etc., and the remaining oxide superconducting material is converted into the shape of the internal space of the organic resin. Fire and mold according to the following.

By repeating this oxidation or reduction by heating and baking, a linear oxide superconductor is formed.

In this way, an oxide superconductor formed in a linear shape (which may also be called a rod shape) as shown in FIG. 1A is completed.

Next, a mixture of oxide superconductor powder and paste, which is a mixture for connecting the linear oxide superconductors formed as described above, will be described.

The above-mentioned powder of the oxide superconducting material having an average particle size of 100 μm or less and octyl alcohol to be used as a paste were mixed at a weight ratio of 1:1 to prepare a mixture for connection.

As the paste, propylene glycol, peptyl alcohol, etc. can be used.

Since this paste will be vaporized and removed in a subsequent firing step as described below, the mixing ratio of the oxide superconductor with the starting material is not a very serious issue. That is, in this example, (paste):(powder of starting material for oxide superconductor)=1:1 (weight ratio), but the ratio is not strictly limited to this.

It goes without saying that any paste can be used as long as it oxidizes and vaporizes in the subsequent firing step in an oxidizing atmosphere.

In this example, a pre-fired powder was used as the oxide superconductor powder to be mixed with the above paste. However, its starting material Y ₂ O ₃ ,
BaCO ₃ and CuO may be mixed at the required mixing ratio.

Moreover, this compound can also be prepared by a coprecipitation method instead of from a powder.

As described above, two linear oxide superconductors and a mixture for connecting the oxide superconductors were produced.

Next, as shown in FIG. 1A, in order to connect the first oxide superconductor 1 and the second oxide superconductor 1' at 5, a mixture 2, 2' is added to the joint cross section.
were applied and subsequently interconnected as shown in FIG. 1B.

Note that the surface of this connection portion was made rough by being a non-polished surface.

In this state, firing was performed under the conditions shown below.

Firing atmosphere: In air Firing temperature: 900°C Firing time: 15 hours Annealing rate: 100°C/hr The purpose of firing in air is to perform firing in an oxidizing atmosphere. Moreover, the firing temperature can be 500 to 1000°C. In addition, the initial cooling process is performed to prevent cracks from entering the oxide superconductor and at the same time to efficiently incorporate oxygen, but it goes without saying that the optimum value differs depending on the type and composition ratio of the oxide superconductor. Nor.

In the above baking step, the paste is oxidized and vaporized into carbon dioxide, moisture, etc., and can be removed.

In this way, as shown in FIG. 1B, the linear oxide superconductors 1 and 1' could be connected at the connecting portion 5 while having superconducting properties.

As described above, the first oxide superconductor 1 and the second oxide superconductor 1' were connected at the connecting portion by the mixture 3 made of the powder and paste of the third oxide superconductor.

In the state shown in Figure 1B, a current is passed between both ends 11 and 12 to examine the current-temperature characteristics, and the results are as follows.
It was confirmed that Tc onset was 92K or more and Tco was 77K or more.

[Example 2] In this example, as shown in Fig. 2,
Each side surface of the first oxide superconductor 1 and the second oxide superconductor 1' is used as a connecting portion 5.

The oxide superconductor used in this example was formed into a linear shape similar to that produced in Example 1, and its material composition ratio, manufacturing conditions, etc. were the same as in Example 1. be.

First, two linear oxide superconductors similar to those used in Example 1 and a connection mixture are manufactured using the manufacturing method described in Example 1.

Next, a connection mixture was applied to the connection portions 2 and 2' of the two oxide superconductors 1 and 1' to bring the connection surfaces into close contact. Thereafter, it was oxidized and fired in the same manner as in Example 1.

Then, as shown in FIG. 2B, the respective oxide superconductors 1 and 1' could be connected to each other by the mixture 3 composed of the powder and paste of the oxide superconducting material.

In the state shown in Figure 2 B, between both ends 11 and 12
As a result of checking Tc, Tco got 80K.

"Example 3" This example is an example in which an endless coil was manufactured using an oxide superconductor wire.

Figure 3 shows the outline. This endless coil can be used as a battery for electrical energy generated by solar cells or the like.

The method for manufacturing the oxide superconductor coil 7 in this example (material composition ratio, heating conditions, etc.) is basically the same as that for manufacturing the linear oxide superconductor in Example 1, unless otherwise specified. be.

In Example 1, a linear oxide superconductor was formed using an organic resin hollow pipe having a linear shape, but in this example, an organic resin hollow pipe formed in a coil shape was used. A coiled oxide superconductor was formed using a hollow pipe.

That is, in order to form the coiled oxide superconductor of this example, a coiled hollow pipe made of organic resin is prepared as a support for forming the superconductor, and
Filling this coiled hollow pipe with the same starting material for an oxide superconductor as in Example 1 and further heating it to form an oxide superconductor conforming to the shape of the hollow pipe. As a result, a coiled oxide superconductor is obtained.

Then, connect leads 5 and 6 to the switch 10 to the starting and ending points of the formed superconducting coil 7.
3 and 13', connections are made in the same manner as in the first and second embodiments.

That is, in this example, as in Example 1, octyl alcohol was used as the paste, and this paste and the powder of the oxide superconductor represented by (Y ₁ Ba ₂ )Cu ₃ O ₆ to ₈ were mixed in a weight ratio of 1:1. This mixture was used to bring the joints into close contact, and a firing process was performed under the same conditions as in Example 1 to form the joints 13, 13'.
I made the connection at .

In actual connection, connecting parts 13 and 1 are connected by wire or band-shaped oxide superconductors.
3' was formed.

The endless coil shown in FIG. 3 is an example of a DC input method. This endless coil has an input 8 and an output terminal 9 for electrical energy.

Then, when power is being injected from 8 and 9, the switch is turned off, and after the power injection is completed, the switch 10 is turned on to perform physical storage.

The Tco of the endless coil in this example was 79K in experiments. However, it goes without saying that Tco can be improved by selecting a superconducting material.

In the case of AC-type electrical energy storage devices,
The switch portion shown in FIG. 3 may be removed and all of these may be made of oxide superconductors to form a connected storage device. That is, the winding on the output side of the AC transformer may be an endless coil.

In this example, after forming the coils made of oxide superconductor, a second
It is effective to repeat the process of coating the oxide superconductor material and oxidizing the entire material. In that case, type A or B,
Some or all of the values of X, Y, Z, and W may be changed.

"Example 4" This example uses Yb as A and Ba as B in the material composition ratio (A _1-x Bx)yCuzOw constituting the oxide superconductor in Example 1, and the composition ratio and manufacturing method. This is the case where is completely the same as in Example 1.

In other words, (Yb ₁ Ba ₂ ) Cu ₃ O ₆ to ₈ oxide superconductors are combined into (Yb ₁ Ba ₂ )
A mixture of oxide superconductor powder with a composition ratio of Cu ₃ O ₆ to ₈ and octyl alcohol as a paste in a 1:1 weight ratio was connected and fired at the upper firing limit shown below. This is a simple example.

Firing atmosphere: Air Firing temperature: 900°C Firing time: 15 hours Annealing rate: 100°C/hr In this example, Tco at both ends of the oxide superconductor after connection was measured and was able to be maintained at 81K.

In the above embodiments, only the connection between oxide superconductors was mentioned, but after connecting the oxide superconductors to each other, plating is applied to the outside of the oxide superconductors.
It is also possible to form metals or metal compounds by ion plating or printing, and weld them to the outside.By using this technology, oxide superconductors can be used as part of electrical devices. becomes possible.

In addition, by using copper or a copper compound as the metal or metal compound, its use as a component can be particularly expanded.

In addition, in the above examples, the powder of the oxide superconductor was mixed with the paste to form a mixture used for connecting the oxide superconductors, but the starting material of the oxide superconductor was directly mixed in the paste, A method using this mixture may also be used. However, in such cases, pressurization is generally difficult to maintain, so Tco tends to be low, and lot variations are likely to occur.

For this reason, as shown in Example 1, the method of mixing and pre-calcining the starting materials once and then mixing the finely powdered material into the paste eliminates lot variation and achieves a Tco higher than the liquid nitrogen temperature. It is valid.

Also, when oxide superconductor powder is made by coprecipitation,
Since the particle size is reduced to around 0.1μ, it is effective in obtaining more homogeneous characteristics.

Further, the shape of the oxide superconductor can be any desired shape such as linear, tubular, or band-like.

"Effects" By employing the configuration of the present invention, it became possible to connect oxide superconductors, and it was possible to obtain a technology for easily producing processed products such as superconducting magnets.

The present invention takes advantage of the fact that oxide superconductors require a firing process in an oxidizing atmosphere, and it goes without saying that the present invention can be applied to the connection of oxide superconductors. .

[Brief explanation of drawings]

FIG. 1 shows an example of connection of oxide superconductors using the present invention. FIG. 2 shows an example of connection of oxide superconductors using the present invention. FIG. 3 shows an example of an electricity storage device manufactured using the present invention.

Claims (1)

[Claims] 1. A method for connecting a first oxide superconductor and a second oxide superconductor, comprising mixing powder of a third oxide superconductor or its starting material with a paste. a step of producing a mixture; a step of using the mixture to bring the first oxide superconductor and the second oxide superconductor into close contact with each other at the connection portion; and firing in an oxidizing atmosphere so that the connection portion A method for connecting superconductors, comprising: a step of imparting superconductivity and removing paste from the mixture; and a step of slow cooling after the step. 2 In claim 1, the first and second
and the third oxide superconductor is (A _1-x Bx)
yCuzOw x=0~1.0, y=2.0~4.0 preferably
2.5-3.5, z=1.0-4.0 preferably 1.5-3.5, w=
4.0 to 10.0 preferably 6.0 to 8.0, A is one or more elements of group A of the periodic table of elements, and B is one or more elements of group A of the periodic table of the elements. Connection method. 3. The method of connecting superconductors according to claim 1, wherein the first and second oxide superconductors constituting the connection portion have non-polished surfaces.