JPH08106823A - Manufacture of oxide superconductive wire material - Google Patents

Abstract

PURPOSE: To form a superconductivity applied device of superior performances by having all the triaxiality of crystal orientation of a supercooductive material so as to provided with extremely high superconductive critical current density. CONSTITUTION: Powder of Bi2 O3 , SrO, CaO, and CuO of purity 99% or more are mixed so as to have an atomic rate of Bi:Sr:Cu=2:2:1:2. This mixture is put in an aluminum crucible and calcinated in an air flow of, for example, 20% of oxygen and 80% of nitrogen under 800 deg.C for 24 hours. This is pulverized again in a glove in which 100% of nitrogen gas is flown and the POWDER is filled in a silver pipe of 99.99% purity. This is wire-drawn, for example, to an outer diameter of 1.5mm by a drawing bench under being kept at 160 deg.C, for example, and after that, is rolled into, for example, the thickness of 0.07mm under being kept at 160 deg.C. This is cut into 3cm and heat treated in an air flow of 20% of oxygen and 80% of nitrogen. The superconductive material are thus provided with all the triaxiality of crystal orientation so that extremely high superconductive critical current density can be obtained. This is set to superconductive wire material BSCC 1 and silver 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure and a manufacturing method of a superconducting wire using an oxide superconducting material, which is capable of flowing a high superconducting critical current density Jc even in a magnetic field. Regarding

[0002]

2. Description of the Related Art Since the discovery of the first oxide high temperature superconducting material in 1986, more than several tens of oxide superconducting materials have been discovered. Among them, a substance having high stability, relatively easy to synthesize, easy to orient the crystal (align the crystal in a specific direction), and have a high superconducting transport current density (transport Jc) can be obtained. For reasons such as easy

[0003]

[Chemical Formula 2] (Bi _1-X1 Pb _X1 ) ₂ Sr ₂ Can ₁ Cu _n O _{2n + 4} (Chemical _Formula 2) where 0 ≦ X1 ≦ 0.4 n = 1, 2, 3 (hereinafter, The development of high-temperature superconducting wire is underway, centering on the superconducting material represented by the composition formula of BSCC).

As a typical concrete method for producing a high temperature superconducting wire, for example, silver as introduced in Applied Physics, Vol. 62, No. 5, 1993, p. 455. The sheath method can be mentioned.

[0005]

The above prior art does not consider the direction of the silver crystal complexed with the superconducting material BSCC, and as a result, the orientation of the crystal of the superconducting material is sufficiently aligned. Therefore, the superconducting critical current density (J
No sufficiently high c) was obtained.

[0006]

The above object is achieved by aligning the directions of silver crystals to be complexed with BSCC.

In order to make the orientations of silver crystals uniform, the drawing and rolling steps in the step of producing a superconducting wire may be carried out while maintaining the temperature at 100 to 250 ° C. After processing at this temperature, by annealing at a temperature of 400 ° C. or higher, the silver complexed with BSCC has a so-called cubic texture. The cubic texture is, for example, 1 of "Fabric" published by Maruzen Co., Ltd., edited by Shinichi Nagashima.
As described on pages 33 and 185, {100} <0
It is a texture of 01> direction. However, when actually manufacturing the superconducting wire, the BS filled inside the silver tube
The temperature of the heat treatment is at least 700 ° C. or higher, preferably 82 ° C., because the CC powder must be well bonded.
Must be above 0 ° C. The optimum heat treatment temperature at this time varies within a range of several tens of degrees depending on the composition of BSCC and the atmosphere (mainly oxygen partial pressure) at the time of heat treatment.

In silver having a cubic texture, the {100} plane of the crystal is parallel to the rolling plane and the <100> direction is the longitudinal direction of the wire. By controlling the crystal texture of silver in this manner, the superconducting critical current density (Jc) of the superconducting wire which is a composite of silver and BSCC can be increased.

[0009]

When a superconducting wire is manufactured, it is better that the a, b, and c axes of the crystal of the superconducting substance are oriented in the same direction (triaxial orientation). I found that my body was able to do it. Therefore, we devised a method for producing a superconducting wire having a high Jc by orienting the superconducting substance in three axes.

B is used for silver tubes, as has been done conventionally.
In a wire rod manufacturing method in which SCC powder or a precursor powder which becomes BSCC when heat-treated is filled, drawn at room temperature, rolled, and further heat-treated, the crystal orientation of BSCC is not sufficiently aligned, The Jc in a magnetic field of 20T at 0.2K was about tens of thousands of A / cm ^2, and there was a demand for further improvement in practical use.

In the method for producing a superconducting wire according to the present invention,
The silver texture around the superconducting material becomes the cubic texture. In the portion where silver and BSCC are in contact with each other, the crystal orientation of BSCC grows while being influenced by the crystal orientation of silver. Therefore, if silver has a cubic texture, BS
The CC is triaxially oriented, and as a result, a very high Jc can be obtained in the superconducting wire according to the present invention.

Further, instead of pure silver, an alloy of silver and gold having a cubic texture, an alloy of silver and palladium, an alloy of silver and copper, a dispersion strengthening alloy in which MgO is dispersed in a silver matrix phase, and a silver matrix. Even when a dispersion strengthening alloy in which an intermetallic compound is dispersed in a phase is used, the high Jc is similarly high.
Is considered to be obtained.

[0013]

Embodiments of the present invention will be described below.

(Example 1) First, a superconducting substance to be filled in a silver tube was prepared. Bi: Sr: C in atomic ratio
Powders of Bi ₂ O ₃ , SrO, CaO, and CuO having a purity of 99% or more are mixed so that a: Cu = 2: 2: 1: 2. This mixed powder was placed in an alumina crucible and fired at 800 ° C. for 24 hours in a stream of 20% oxygen and 80% nitrogen. This was crushed again in a glove which had been flushed with 100% nitrogen gas, and this powder was powdered with a silver pipe of 99.998% purity (internal diameter 4
mm, outer diameter 6 mm). This was drawn at a draw bench to an outer diameter of 1.5 mm while being kept at 160 ° C., and then rolled to a thickness of 0.07 mm while being kept at 160 ° C. This was cut into a length of 3 cm. This was heat-treated in a stream of 20% oxygen and 80% nitrogen. The temperature conditions for heat treatment are
Room temperature to 800 ° C for 5 hours, 800 ° C to 860 ° C for 2 hours, hold at 860 ° C for 10 minutes, 870 ° C
Up in 30 minutes, hold at 870 ° C for 5 minutes, 800
It cooled to 15 degreeC in 15 hours, and cooled from 800 degreeC to room temperature in 5 hours. The explanatory view of the produced superconducting wire rod sample is shown in FIG. In the figure, 1 is BSCC and 2 is silver.

When the orientation of silver crystals on the surface of the sample after the heat treatment was examined by X-ray diffraction measurement, about 80% of crystal grains {1
It was confirmed that the {00} plane was parallel to the tape surface, and its <100> orientation was parallel to the rolling direction.

Superconducting critical current density Jc of sample after heat treatment
Was measured by the DC four-terminal method. At 4.2K, 5 at zero magnetic field
When a magnetic field of 00,000 A / cm ² , 8 T was applied vertically to the substrate, it was 300,000 A / cm ² .

(Comparative Example 1) The powder of the superconducting material prepared in Example 1 was filled in a silver pipe in the same manner as in Example 1. This was drawn in a room with a room temperature of 25 ° C. to an outer diameter of 1.5 mm with a draw bench, and then rolled to a thickness of 0.07 mm. This was cut into a length of 3 cm. This is 20% oxygen 8
Heat treatment was performed in a 0% nitrogen stream. The temperature condition of the heat treatment was the same as in Example 1.

When the orientation of silver crystals on the surface of the sample after the heat treatment was examined by X-ray diffraction measurement, about 70% of crystal grains {1
It was confirmed that the 10} plane was parallel to the tape surface, and its <112> orientation was parallel to the rolling direction.

Superconducting critical current density Jc of sample after heat treatment
Was measured by the DC four-terminal method. At 4.2K, 1 at zero magnetic field
When a magnetic field of 00,000 A / cm ² , 8 T was applied vertically to the substrate, it was 50,000 A / cm ² .

Comparative Example 2 The silver pipe was filled with the powder of the superconducting material prepared in Example 1 as in Example 1. In a room with a room temperature of 25 ° C, this is 400 for each drawing.
While annealing at ℃ for 1 hour, draw the wire with a draw bench to an outer diameter of 1.5 mm, and then 400 ℃ for each rolling.
While being annealed for 1 hour, it was rolled to a thickness of 0.07 mm. This was cut into a length of 3 cm. This was heat-treated in a stream of 20% oxygen and 80% nitrogen. The temperature conditions for heat treatment are
Same as Example 1.

When the orientation of silver crystals on the surface of the sample after the heat treatment was examined by X-ray diffraction measurement, it was found that the specific crystal planes did not seem to be aligned in a specific direction, and The directions were random.

Superconducting critical current density Jc of sample after heat treatment
Was measured by the DC four-terminal method. At 4.2K, 9 at zero magnetic field
When a magnetic field of 0,000 A / cm ² , 8 T was applied vertically to the substrate, it was 40,000 A / cm ² .

(Comparative Example 3) The powder of the superconducting material prepared in Example 1 was filled in a silver pipe as in Example 1. This is annealed at 400 ° C for 1 hour for each drawing, and drawn at a temperature of 160 ° C with a draw bench to an outer diameter of 1.5 mm, and then at 1 ° C at 400 ° C for each rolling.
While annealing for an hour, at a temperature of 160 ° C, a thickness of 0.
Rolled to 07 mm. This was cut into a length of 3 cm.
This was heat-treated in a stream of 20% oxygen and 80% nitrogen. The temperature condition of the heat treatment was the same as in Example 1.

When the orientation of the silver crystal on the surface of the sample after the heat treatment was examined by X-ray diffraction measurement, it was found that the specific crystal planes did not seem to be aligned in a specific direction, and The directions were random.

Superconducting critical current density Jc of sample after heat treatment
Was measured by the DC four-terminal method. At 4.2K, 8 at zero magnetic field
When a magnetic field of 0,000 A / cm ² , 8 T was applied vertically to the substrate, it was 40,000 A / cm ² .

As can be seen from the above-mentioned Example 1, Comparative Examples 1, 2 and 3, during the production of the superconducting wire, wire drawing,
It can be seen that a high Jc can be obtained by performing the rolling process at a temperature of about 160 ° C. without annealing in the middle.

(Example 2) In the same manner as in Example 1, except that wire drawing and rolling were performed at 100 ° C, 150 ° C, 200 ° C and 25 ° C.
A sample was prepared by performing the test at 0 ° C. and 300 ° C., and the same evaluation as in Example 1 was performed.

The orientation of the silver crystals on the surface of the sample after the heat treatment was examined by X-ray diffraction measurement, and about what extent the {100} planes of the crystal grains were parallel to the tape surface and their <100>
It was investigated whether the azimuth was aligned parallel to the rolling direction. The results are shown in Figure 2. Further, the superconducting critical current density Jc of the sample after the heat treatment was measured by the DC four-terminal method. The results are shown in Fig. 3. The results of Example 1 and Comparative Example 1 are also shown in FIGS. 2 and 3.

From FIGS. 2 and 3, it is understood that the temperature for carrying out the drawing and rolling steps is preferably 100 ° C. or higher and 250 ° C. or lower, and particularly preferably 150 ° C. or higher and 200 ° C. or lower.

(Example 3) First, a superconducting substance to be filled in a silver tube was prepared. Bi: Pb: S in atomic ratio
r: Ca: Cu = 1.84: 0.34: 2: 2.2: 3 so that Bi ₂ O ₃ , PbO, Sr with a purity of 99% or more is obtained.
Mix powders of O, CaO, CuO. This mixed powder was placed in an alumina crucible and fired at 800 ° C. for 24 hours in a stream of 20% oxygen and 80% nitrogen. This was crushed again in a glove flowed with 100% nitrogen gas, and this powder was purified to a purity of 9%.
It was filled in a 9.998% silver pipe (inner diameter 4 mm, outer diameter 6 mm). This was drawn at a draw bench to an outer diameter of 1.5 mm while being kept at 160 ° C., and then rolled to a thickness of 0.07 mm while being kept at 160 ° C. This was cut into a length of 3 cm. This was heat-treated in a stream of 20% oxygen and 80% nitrogen. The temperature condition for heat treatment is from room temperature to 837 ° C.
The temperature was raised over time, the temperature was maintained at 837 ° C. for 100 hours, and the temperature was cooled to room temperature in 10 hours.

When the orientation of silver crystals on the surface of the sample after the heat treatment was examined by X-ray diffraction measurement, about 80% of crystal grains {1
It was confirmed that the {00} plane was parallel to the tape surface, and its <100> orientation was parallel to the rolling direction.

Superconducting critical current density Jc of sample after heat treatment
Was measured by the DC four-terminal method. At 4.2K, 4 at zero magnetic field
When a magnetic field of 00,000 A / cm ² , 8 T was applied vertically to the substrate, it was 250,000 A / cm ² .

(Comparative Example 4) The powder of the superconducting material prepared in Example 3 was filled in a silver pipe in the same manner as in Example 3. This was drawn in a room with a room temperature of 25 ° C. to an outer diameter of 1.5 mm with a draw bench, and then rolled to a thickness of 0.07 mm. This was cut into a length of 3 cm. This is 20% oxygen 8
Heat treatment was performed in a 0% nitrogen stream. The heat treatment temperature conditions were the same as in Example 3.

When the orientation of silver crystals on the surface of the sample after the heat treatment was examined by X-ray diffraction measurement, about 70% of crystal grains {1
It was confirmed that the 10} plane was parallel to the tape surface, and its <112> orientation was parallel to the rolling direction.

Superconducting critical current density Jc of sample after heat treatment
Was measured by the DC four-terminal method. At 4.2K, 2 at zero magnetic field
When a magnetic field of 00,000 A / cm ² , 8 T was applied vertically to the substrate, it was 80,000 A / cm ² .

(Comparative Example 5) The powder of the superconducting material prepared in Example 3 was filled in a silver pipe in the same manner as in Example 3. In a room with a room temperature of 25 ° C, this is 400 for each drawing.
While annealing at ℃ for 1 hour, draw the wire with a draw bench to an outer diameter of 1.5 mm, and then 400 ℃ for each rolling.
While being annealed for 1 hour, it was rolled to a thickness of 0.07 mm. This was cut into a length of 3 cm. This was heat-treated in a stream of 20% oxygen and 80% nitrogen. The temperature conditions for heat treatment are
Same as Example 3.

When the orientation of the silver crystal on the surface of the sample after the heat treatment was examined by X-ray diffraction measurement, it was found that the specific crystal planes did not seem to be aligned in a specific direction, and The directions were random.

Superconducting critical current density Jc of sample after heat treatment
Was measured by the DC four-terminal method. At 4.2K, 1 at zero magnetic field
When a magnetic field of 10,000 A / cm ² and 8 T was applied vertically to the substrate, it was 50,000 A / cm ² .

(Comparative Example 6) The powder of the superconducting material prepared in Example 3 was filled in a silver pipe in the same manner as in Example 3. This is annealed at 400 ° C for 1 hour for each drawing, and drawn at a temperature of 160 ° C with a draw bench to an outer diameter of 1.5 mm, and then at 1 ° C at 400 ° C for each rolling.
While annealing for an hour, at a temperature of 160 ° C, a thickness of 0.
It was rolled to 07 mm. This was cut into a length of 3 cm. This was heat-treated in a stream of 20% oxygen and 80% nitrogen. The heat treatment temperature conditions were the same as in Example 3.

When the orientation of silver crystals on the surface of the sample after the heat treatment was examined by X-ray diffraction measurement, it was found that the specific crystal planes did not seem to be aligned in a specific direction, and The directions were random.

Superconducting critical current density Jc of the sample after heat treatment
Was measured by the DC four-terminal method. At 4.2K, 1 at zero magnetic field
When a magnetic field of 00,000 A / cm ² , 8 T was applied vertically to the substrate, it was 50,000 A / cm ² .

As can be seen from the above-mentioned Example 3, Comparative Examples 4, 5 and 6, during the production of the superconducting wire, wire drawing,
It can be seen that a high Jc can be obtained by performing the rolling process at a temperature of about 160 ° C. without annealing in the middle.

[0043]

According to the present invention, it is possible to obtain a superconducting wire having a high superconducting critical current density, which is operated by cooling by liquid nitrogen as well as by cooling by liquid helium.

[Brief description of drawings]

FIG. 1 is an explanatory view showing the structure of a superconducting wire according to a first embodiment of the present invention.

FIG. 2 is a graph showing the temperature and {100} plane parallel to the tape surface and <10 when drawing and rolling in Example 2 of the present invention.
A characteristic diagram showing the proportion of crystal grains in which the 0> orientation is aligned parallel to the rolling direction.

FIG. 3 is a characteristic diagram showing the relationship between the temperature when drawing and rolling in Example 2 of the present invention and the superconducting critical current density Jc of the sample.

[Explanation of symbols]

 1 ... Superconducting substance, 2 ... Silver.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01F 6/06 ZAA

Claims (4)

[Claims] 1. A silver tube is filled with a powder of an oxide superconducting material, which is drawn at a temperature of 100 ° C. or higher and 200 ° C. or lower, rolled, and further heat-treated at a temperature of 700 ° C. or higher. And a method for producing a superconducting wire. 2. A silver powder is filled with a precursor powder which becomes an oxide superconducting substance by heating, and the precursor powder is heated to 100%.
Drawing and rolling at a temperature between ℃ and 200 ℃,
A method for producing a superconducting wire, further comprising heat treatment at a temperature of 700 ° C. or higher. 3. The method for producing a superconducting wire according to claim 1, wherein a tube made of an alloy containing 50% or more of silver is used instead of the silver tube. 4. The method of claim 1, 2 or 3, the chemical composition of the oxide superconductor material, embedded image _{(Bi 1-X1 Pb X1)} 2 Sr 2 Ca n-1 Cu n O 2n + 4 + _X2 ... (Chemical _formula 1) Here, 0? X1? 0.4-0.5? X2? 0.5 A superconducting wire represented by n = 1,2,3.