JPH02243557A - Production of oxide superconductor and wiry material thereof - Google Patents

Abstract

PURPOSE:To readily produce an oxide superconductor excellent in superconductive characteristics in a short time by calcining a mixture of a Y oxide with a Ba carbonate and Cu oxide, homogeneously dispersing the resultant powder and Y2O3 powder having a specific particle diameter and sintering the obtained mixture. CONSTITUTION:A Y oxide, such as Y2O3, is mixed with Ba carbonate, such as BaCO3, and a Cu oxide, such as CuO, in an optional proportion. The resultant mixture is subsequently calcined to afford a calcined body, which is then pulverized to afford powder. The obtained powder and Y2O3 powder having <=0.5mum particle diameter are homogeneously dispersed to provide sample powder. The resultant sample powder is subsequently sintered or sealed in a metallic pipe, which is then subjected to drawing working and heat-treated. Thereby, an oxide superconductor excellent in superconductive characteristics and wiry materials thereof with hardly any nonsuperconductive phase in crystals are obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an oxide superconductor and a method for producing its wire, and in particular, to an oxide superconductor having excellent superconducting properties and having few non-superconducting phases in its crystals. The present invention also relates to an oxide superconductor and a method for manufacturing the wire, which can be easily manufactured in a relatively short period of time.

[Prior Art and Problems to be Solved by the Invention] In recent years, many research institutes have attempted to make oxide superconductors into wires for the purpose of making cables, coils, etc. In order to manufacture such an oxide superconducting wire, it is first necessary to manufacture a high quality oxide superconducting crystal with excellent superconducting properties.

A powder mixing method is generally well known as a method for producing an oxide superconductor having high quality crystals. In this method, for example, when producing YBa 2 Cu 307-8 crystal, an oxide superconductor is obtained by mixing, firing, and sintering raw material oxide powders such as Y203 and Ba co 3 ° Cu O. .

However, in this powder mixing method, Cu
Since non-superconducting phases such as O, Ba Cu 02, etc. precipitate at grain boundaries, YBa 2 of the obtained oxide superconductor
When superconducting current flows through Cu 307-6 crystal,
The current is cut off at the grain boundaries, and as a result, the critical current density Jc of the oxide superconductor as a whole becomes, for example, at77
In addition, OT has a very small value of several 100 A/c-j, and compared to at77 required for practical wires, OT has a value of several 10'
The value of A/cd or more is far away.

In addition, as a method for obtaining a higher Jc value than the powder mixing method described above, there is a method in which raw material oxide powder such as Y203, Ba CO3, CuO, etc. is sealed in a metal tube and the crystals are given orientation by applying pressure. However, even with this method, Jc is as low as at77 and several thousand A/cd in OT, so it is not practical.

Therefore, the so-called rapid cooling unidirectional solidification method was devised, which uses the unidirectional solidification method as its basic concept and attempts to align the crystal axes. This method uses, for example, YBa 2 Cu
After putting the calcined powder of 307-& into a PT crucible and heating it to about 1400°C to make it into a molten state, 2. By cooling, a molded body in which a liquid phase exists is created, and this molded body is reheated to about 1200°C, and then slowly cooled from about 1000°C to 950°C to form relatively large crystals. After it is produced, it is gradually crystallized using an arbitrary temperature gradient to align the crystal axes. The oxide superconductor produced by this method is Jc
has obtained a high value of IOA/C1i or higher for at77 in OT.

However, the crystals of oxide superconductors obtained by this method still contain Y2B, a non-superconducting phase with a grain size of several μm.
a A large amount of Cu 05 remains. Furthermore, as mentioned above, it is necessary to create a temperature gradient and gradually crystallize.
There are also problems such as increased manufacturing time.

Therefore, the object of the present invention is to provide an oxide superconductor and its wire which can be easily produced in a short time and have excellent superconducting properties and a small amount of non-superconducting phase in the crystal. An object of the present invention is to provide a method for manufacturing a wire rod.

[Means to solve the problem]

The method for manufacturing an oxide superconductor adopted by the present invention in order to achieve the above object is to mix Y oxide, B, carbonate, and Cu oxide in arbitrary proportions and sinter the powder, and The structural feature is that a sample powder obtained by uniformly dispersing Y2O3 powder having a diameter of 0.5 μm or less is fired. In addition, the method for manufacturing the wire rod is to uniformly mix and sinter Y oxide, B, carbonate, and Cu oxide in any proportion, and Y2O powder with a particle size of 0.5 μm or less. The structural feature is that the sample powder obtained by dispersing the powder is enclosed in a metal tube, and the metal tube is subjected to wire drawing and heat treatment.

[Effect]

According to the method for producing an oxide superconductor and its wire of the present invention, Y oxide (e.g. Y203), Ba carbonate (e.g. Ba CO3) and Cu oxide (e.g. Cu
Ba Cu contained in the powder obtained by mixing and firing O)
02, CuO and Y with a particle size of 0.5 a m or less
2O3 powder and rY203 +4Ba CuO2+ 2
Cu O→2 YBa 2 Cu 3 o7-1i
React as shown in J to form YBa 2 Cu3 o7. Since crystals are generated, the generation of non-superconducting phases can be significantly suppressed, and a high critical current density Jc can be obtained.

〔Example〕

Next, an embodiment embodying the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention. FIG. 1 is a time chart showing an example of a heat pattern when a sample powder is heat-treated according to an embodiment of the present invention. FIG. 2 is a time chart showing a critical current of an oxide superconducting wire manufactured by the method of this embodiment. The density characteristic diagram, FIG. 3, is a correlation diagram between the superconducting transition temperature of the oxide superconducting wire, y2o, and the mesh diameter of the powder sorting filter.

In this example, first, Y2O3, BaCO3 and Cu
After mixing powders of O (each with a purity of 99.9%), they were fired at 930°C for 10 hours in an oxygen atmosphere, and this fired body was ground in a ball mill to form a fine mixed powder, from which only particles with a particle size of 1 μm or less were mixed. were selected.

Next, the powder of y2o was ground into a fine powder using a ball mill in the same manner as above, and the inner particle size was 0.1 μm.
Only the following particles were selected: Then, the fine mixed powder (Y203 + Ba CO3 + Cu O
) and the fine powder (Y2
03) and /cffl, 4. in IOT. It showed a high value of OX 10' A/d. Furthermore, when the superconducting transition temperature Tc end of this wire was measured, a value of 90.2 was obtained.

Therefore, it can be seen that the oxide superconducting wire manufactured by the method of this example has excellent superconducting properties.

Weight of (Y, 0.+ BaC0, + CuO) + (YA
) in such a way that it is evenly dispersed in a proportion of the weight of
This is used as a sample powder, and the sample powder has an outer diameter of 5, an inner diameter of 3,
After enclosing it in a 5 m metal tube (a silver one was used here) and drawing it so that the outer diameter of the metal tube was 0.8W, it was drawn in an oxygen atmosphere as shown in Figure 1. A Y-Ba-Cu-0 wire rod was obtained by heat treatment using a heat pattern.

4 of the Y-Ba-Cu-0 wire produced in this way
FIG. 2 shows the measurement results of the critical current density Jc at 77.3 in a magnetic field by the terminal electrical resistance measurement method.

According to this, Jc is 3.5X10'A in OT, then
The above fine mixed powder (Y203 + Ba C03 + Cu
O) and the above-mentioned fine powder (Y203) are determined by the weight of (Y, Q, + BaC0, + CuO) + (Y,
0. ), Jc (at77.3K)
showed values of 2.1×10′ A/cii in OT, 1.8×10′ A10f in IOT, and 85.8 for Tcend. According to this, the value is slightly lower than when the above-mentioned blending ratio is 5%, but it sufficiently satisfies the value required for a practical wire material.

Finally, in the structure of the present invention, the reason why the particle size of the Y2O3 powder that forms the sample powder together with the mixed powder consisting of Y oxide, Ba carbonate, and Cu oxide is limited to 0.5 μm or less is explained below. This will be explained with reference to FIG.

Here, FIG. 3 shows the above Y20. Powder is pulverized into fine powder using a ball mill, and the mesh size of a filter is used to select the particle size of the fine powder. It is a drawing showing the relationship with superconducting transition temperature Tc end.

According to this, when the mesh diameter of the filter is 0.8 μm or less, Tcend above the liquid nitrogen temperature (77.3 K)
was obtained, but in the case beyond that, Tc end was 7
This is because Tc end is high even when the mesh diameter is 0.8 μm or less, especially when it is 0.5 μm or less.

〔Effect of the invention〕

According to the present invention, a powder obtained by mixing and firing Y oxide, Ba carbonate, and Cu oxide in an arbitrary ratio and a powder having a particle size of 0
．． A method for producing an oxide superconductor and Y oxide, characterized by firing a sample powder obtained by uniformly dispersing Y2O and powder having a particle size of 5 μm or less.

A sample powder obtained by uniformly dispersing a powder obtained by mixing and firing B1 carbonate and Cu oxide in an arbitrary ratio and Y, O2 powder with a particle size of 0.5 μm or less is sealed in a metal tube. A method for manufacturing an oxide superconducting wire is provided, which is characterized by drawing and heat-treating a perilla metal tube, thereby obtaining an oxide superconductor and its wire with excellent superconducting properties and a small amount of non-superconducting phase.

Furthermore, since the production method of the present invention basically uses a powder mixing method, it is easier to produce an oxide with excellent superconducting properties in a relatively short time compared to methods such as rapid cooling and unidirectional solidification. Superconductors and their wires can be manufactured.

[Brief explanation of drawings]

FIG. 1 is a time chart showing an example of a heat pattern when heat-treating sample powder according to embodiments of the present invention;
FIG. 2 is a critical current density characteristic diagram of the oxide superconducting wire manufactured by the method of this example. Figure 3 shows the superconducting transition temperature and Y of the oxide superconducting wire.
FIG. 2 is a diagram showing the relationship between the amount of phase and the mesh diameter of a filter for sorting 2O3 powder.

Claims (2)

[Claims] (1) Sample powder obtained by uniformly dispersing a powder obtained by mixing and firing Y oxide, Ba carbonate, and Cu oxide in arbitrary proportions and Y_2O_3 powder with a particle size of 0.5 μm or less A method for producing an oxide superconductor, comprising firing. (2) Sample powder obtained by uniformly dispersing a powder obtained by mixing and firing Y oxide, Ba carbonate, and Cu oxide in arbitrary proportions and Y_2O_3 powder with a particle size of 0.5 μm or less 1. A method for manufacturing an oxide superconducting wire, the method comprising: enclosing the metal tube in a metal tube, and subjecting the metal tube to wire drawing and heat treatment.