JP2678619B2 - Oxide superconducting wire and its manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a superconducting wire and a method for manufacturing the same, and more particularly to a superconducting wire having an improved critical current density and a method for manufacturing the same.

[Conventional technology]

Conventionally, intermetallic compounds such as Nb ₃ Sn and Nb ₃ Ge have been known as superconducting materials and have been put to practical use. The critical temperature (Tc) for obtaining the superconducting state of these intermetallic compounds was 23 K even for Nb ₃ Ge, which was the highest, and it was necessary to use liquid helium for cooling.

However, in 1987, YBa ₂ Cu ₃ O ₇ _δ-based oxide
It was discovered that Tc was about 90K, which was dramatically higher than that of conventional intermetallic compounds. This Tc temperature is the boiling point of liquid nitrogen
It greatly exceeds 77K, and the oxide superconductor can be cooled by using inexpensive liquid nitrogen without using extremely expensive liquid helium to obtain a superconducting state.

Since the conventional superconducting material is a metal, it is relatively easy to form a wire such as wire drawing. However, since the oxide superconducting material is a ceramic, the ductility is poor and it is very difficult to form a wire. Therefore, a method has been reported in which the oxide superconducting powder is packed in a pipe, pulled up, and then heat treated to form a wire (1987 MRS Spring Meeting, P219-
221).

[Problems to be solved by the invention]

However, the above-mentioned conventional technique has a problem that the contact area between the superconducting powders is small and a high critical current density (Jc) cannot be obtained because the powder is packed into a wire. Further, the oxide superconducting material has a layered perovskite structure,
There is anisotropy in the direction of current flow. However, since the conventional method does not consider this anisotropy at all, the current between particles becomes difficult to flow depending on the direction of the bond between particles, which hinders the increase in Jc.

An object of the present invention is to obtain an oxide superconducting wire having an increased critical current density.

Another object of the present invention is to provide a method for producing an oxide superconducting wire having a high critical current density.

[Means for solving the problem]

The above-mentioned object is achieved by using plate-shaped particles having a C-plane grown as an oxide superconducting material used when producing a wire.

The oxide superconducting wire of the present invention comprises a metal tube extending in the longitudinal direction, and an oxide superconducting material composed of superconducting oxide particles having a perovskite type crystal structure filled in the tube and bonded to each other. However, the superconducting oxide particles have plate-like particles having a dimension in the C-plane direction larger than the dimension in the C-axis direction, and the oxide superconducting material is composed of Y, Ba, Cu, O, rare earths and alkali metals. In the oxide superconducting wire containing at least one of the superconducting oxide particles, and the C-plane of the superconducting oxide particles having a preferred orientation oriented in the longitudinal direction, the superconducting oxide particles contain the plate-like particles in an amount of 50 vol% or more. The oxide superconducting material has a large proportion, and the oxide superconducting material contains at least one of bismuth and thallium.

Plate-like particles are C in the perovskite type crystal structure.
It means a particle having a dimension in the plane direction larger than that in the C-axis direction.

The method for producing an oxide superconducting wire according to the present invention comprises the steps of preparing a metal tube extending in the longitudinal direction, including superconducting oxide particles having a perovskite type crystal structure, and the dimension of the particles in the C-plane direction being the C-axis. Is an oxide superconducting material in which plate-like particles larger than the dimension in the direction are contained in a proportion of more than 50 vol% of the oxide superconducting material powder, and Y, Ba, Cu, O, and rare earths, alkali metals, and bismuth are included. A step of preparing an oxide superconducting material containing at least one selected from the group consisting of thallium, and wire-drawing and / or rolling a composite conductor in which the oxide superconducting material is filled in the tube in the longitudinal direction. Forming a wire and thereby allowing the oxide superconducting material to have a preferred orientation in which the C planes of the particles of the oxide superconducting material powder are oriented in the longitudinal direction; and heat the processed composite conductor to burn the oxide superconducting material. And a step of tying The features.

To form a composite conductor, a method of filling an oxide superconducting material composed of plate-like particles into the inside of a tubular metal material, and a method of filling a raw material powder into the inside of the tubular metal material and then heat-treating the compound superconducting material into a plate shape There is a method of generating particles. In the latter case in particular, the composite conductor may be thinned by wire drawing and / or rolling to orient the plate-like particles while generating the plate-like particles of the oxide superconducting material by heat treatment. A large number of through holes may be provided in the wall of the metal tube in order to sufficiently supply oxygen during the sintering of the plate-like particles.

The oxide superconductor is a composition composed of Y, Ba, Cu and O. The oxide superconductor may be a composition containing Y, Ba, Cu, O, and at least one selected from the group consisting of rare earth elements, alkali metals, bismuth, and thallium.
In an oxide superconducting material of a superconducting wire, plate-like particles having a C-plane having a length in the C-plane direction with respect to the C-axis direction of 2 times or more are oriented toward the longitudinal axis of the wire, and the plate-like particles are oxides. It is preferably 60 vol% or more of the superconducting material.

High-temperature oxide superconducting materials such as complex oxides of barium, yttrium, and copper have a layered crystal structure based on the perovskite type, and electrons easily flow along the layers in the crystal. In addition, since the crystal structure is layered, the crystal particles become a plate shape by appropriately selecting the heat treatment condition at the time of generation and the subsequent pulverization time, and the crystal particles are oriented in the C-axis direction which is a direction perpendicular to the C plane of the plate particles. In comparison, electrons easily flow in the C plane direction. Therefore, when converting such a material into a wire rod, the critical current density of the superconducting wire is increased by orienting the C planes of the plate-like particles in the longitudinal direction of the wire rod. In the state where the tubular metal is filled with the plate-like particles, or in the state where the raw material powder is filled and then heat-treated to produce the plate-like particles, the plate-like particles have no particular orientation and mist in an arbitrary direction. . In the process of drawing this composite conductor, the particles inside are also pulled in the longitudinal direction of the wire and a compressive force is applied in a direction perpendicular to it, so that the C-plane of the plate-shaped particles is oriented in the longitudinal direction. Orient to.

Oxide superconducting agglomerates containing plate-shaped grains on which the C-plane is grown, the firing temperature and time and the time of the crushing process (degree of crushing)
Is produced by appropriately selecting. Since the powder used in the conventional wire formation has not been considered for these conditions, 80 vol% or more is composed of particles whose ratio of the length of the C plane to the length in the C axis direction is less than twice. Was there. Therefore, as described above, the contact area between the superconducting powders in the wire is small, the orientation of the bonds between the particles is random, and a high Jc cannot be obtained. In the present invention, in the C plane with respect to the length in the C axis direction. A high Jc was achieved by using a powder composed of grains having a C-plane grown to have a length of 2 times or more for forming a wire. The powder is patterned by appropriately selecting firing conditions. The firing temperature is 900 ° C or higher and 1050 ° C or lower, preferably 970 ° C or higher and 1025 ° C or lower. The firing time is a short time when the temperature is high in consideration of the temperature, but a long time is required when the temperature is low. When the firing temperature is lower than 900 ° C, the C-plane is difficult to grow, and when the temperature is higher than 1050 ° C, the oxide superconducting phase is changed to another product.

FIG. 9 shows a perovskite type crystal structure of an oxide superconductor. The relationship between the C-axis and the C-plane in the crystal is as shown in the figure. In the powder, the C plane corresponds to the cleavage plane, and the C axis is the direction perpendicular to that plane.

[Action]

The plate-shaped oxide superconducting particles on which the C-plane is grown are arranged so that the C-plane has a preferred orientation in the longitudinal direction of the line by the process for obtaining the line, and after the process, The shape of the plate-like particles before processing and the ratio of the plate-like particles having the specific shape are retained. This is because the oxide superconducting material has almost no ductility and has a plate-like particle whose shape in the C-plane direction is larger than the size in the C-axis direction perpendicular to the C-plane.
It is considered that the dimension in the surface direction contains more than 50 vol% of those having a minimum of 10 μm or more, and is small as a whole of about 10 to 60 μm.

Due to the anisotropy of the crystal system, the superconducting material causes a current to flow almost only in the C-plane direction. Higher critical current density Jc can be obtained compared to the wire made by using the conventional powder because the C plane of this conducting surface is oriented in the direction of current flow and the connection between grains is bonded in the direction in which the current easily flows. It is thought that it is easy to do.

〔Example〕

Example 1 FIG. 1 shows a block diagram of a superconducting wire according to this example.
In the figure, a superconducting material 2 is embedded inside a thinned copper tube 1. Further, in the superconducting material 2, the C-plane of the plate-like particles 21 is oriented in the longitudinal direction of the line.

Such a superconducting wire was produced as follows. As shown in FIG. 2, a superconducting material powder 22 was filled inside a copper tube 11 having an outer diameter of 30 mm and an inner diameter of 20 mm. Superconducting material powder 22
Is barium oxide (BaO), yttrium oxide (Y
₂ O ₃ ) and copper oxide (CuO) were mixed so that the molar ratio of Y, Ba and Cu was 1: 2: 3, and then heat-treated at 950 ° C. for 5 hours to obtain Ba _1.8 Y _1.2 Cu ₃ It is a powder of O ₇ _δ. As a result of observing the particle shape of the powder with an optical microscope, it was found that most of them consisted of plate-like particles having a diameter of 30 to 60 μm and a thickness of 10 to 30 μm. Then, the composite conductor consisting of the copper tube 11 filled with the superconducting material 22 was processed into a thin wire with a diameter of 1 mm by extrusion, and then 950 ° C in Ar.
Was maintained for 5 hours to prepare a superconducting wire (A).

As a result of measuring the resistance value of the obtained superconducting wire (A), the critical temperature was 91K. The critical current density was 95 A / cm ² .

On the other hand, for comparison with this, a predetermined amount of raw material powder was separately mixed and filled inside a copper tube having an outer diameter of 30 mm and an inner diameter of 20 mm,
After extruding a copper pipe and processing it into a fine wire with a diameter of 1 mm by wire drawing, calcination in Ar at 950 ° C for 5 hours and 950 ° C in Ar at 5
The main firing of time was performed. The obtained superconducting wire (B) had a critical temperature of 91 K, which was similar to that of the superconducting wire (A), but the critical current density was as small as 50 A / cm ² . As a result of analyzing the superconducting material in the superconducting wire (B) by X-ray diffraction,
It was found to be a collection of crystal grains of _1.8 Y _1.2 Cu ₃ O ₇ _δ. Most crystal grains have a diameter of 30-60 μm and a thickness of 10-30 μm.
It had a plate shape of m.

In order to investigate the orientation of crystal grains, the cross section parallel to the longitudinal direction of each superconducting wire was observed, and the orientation distribution of crystal grains was measured using an image analyzer. Here, the orientation of the crystal grains is represented by the angle formed by the axis line (long axis line) connecting the two points having the maximum distance on the circumference of the crystal grains with the longitudinal direction of the superconducting wire. FIG. 3 shows the measurement results. In the figure, a curve a is the case of a superconducting wire (A) prepared by filling a copper tube with the superconducting material composed of the plate-like particles first described in this example, and then thinning it, and a curve b is for comparison. This is the case of the superconducting wire (B) manufactured by heat treatment after thinning described later. As is clear from the figure, in the case of the curve b, the particles have no special orientation, whereas in the curve a, the orientation of the particles is biased in the longitudinal direction of the superconducting wire. It is considered that the orientation of the particles occurs in the process of thinning after filling the plate-like particles, which is the cause of increasing the critical current density.

Example 2 Barium oxide (BaO), yttrium oxide (Y ₂ O ₃ ),
Copper oxide (CuO) was mixed under the same conditions as in Example 1 to obtain an outer diameter of 30 m.
It was filled in a copper tube having an inner diameter of 20 mm and a diameter of 20 m. This tube in Ar
Gradually draw wire while heat-treating at 950 ℃ to form a fine wire with a diameter of 1 mm to form a composite conductor, then 950 in Ar.
A superconducting wire (C) was produced by carrying out heat treatment at 5 ° C for 5 hours.
Similarly, a copper tube filled with raw material powder was thinned by extrusion, and then heat-treated twice at 950 ° C. for 5 hours in Ar to produce a superconducting wire (D).

The critical temperature of the obtained superconducting wire is (C), (D)
It was 93K. The critical current density (C) is 105 A / cm ² ,
(D) was 58 A / cm ² , and (C) was larger. As a result of analyzing the superconducting material in the superconducting wire by X-ray diffraction,
It has been found that both (C) and (D) are aggregates of Ba ₂ YCu ₃ O _{7 —} δ crystal grains. The crystal grain size is 30-60μ on the long axis.
The short axis was 10 to 30 μm. When the orientation distribution of the crystal grains was measured by using an image analyzer, the superconducting wire (D) showed no particle orientation similar to the curve b in FIG. 3, but the superconducting wire (C) showed Similar to the curve a, it was recognized that the particles were oriented in the longitudinal direction of the line.

As described above, according to the method of the present invention, it is possible to produce a superconducting wire in which the direction in which the electrons of the plate-like particles easily flow is oriented in the longitudinal direction of the line, so that the critical current density is higher than that in the case of no orientation The effect is that it can be nearly doubled.

It is obvious that this effect can be obtained not only in the example but also in the case of using another superconducting material composed of plate-like particles through which an electric current easily flows, or another metal tube.

Further, the superconducting wire of the present invention has an effect that the critical current density of the oxide superconducting wire can be improved.

Example 3 20 g of Y ₂ O ₃ , BaCO ₃ and CuO, which are commercially available powders, were weighed in total so that the molar ratio of Y, Ba and Cu of these materials was 1: 2: 3, and made by Agate. The mixture was mixed for 1 hour with a raikai machine. The Y ₂ O ₃ powder had a particle size of 2 to 3 μm, the BaCO ₃ powder had a particle size of 2 to 5 μm, and CuO had a particle size of 1 to ₃ μm. The operation of pre-calcining the powder mixture in O ₂ at a temperature of 950 ° C. for 5 hours and then pulverizing the agglomerates generated by the pre-calcination was repeated twice to obtain a powder of an oxide superconducting material. This powder is 30
The pellet was formed into a pellet having a diameter of 1.0 mm and a thickness of 1.0 mm, and the pellet was baked in O ₂ at 975 ° C. for 20 hours to grow the C plane sufficiently. Saga 3
An agglomerate containing 80 vol% or more of grains that are more than double the amount was obtained.
This agglomerate is crushed for 30 minutes with an agate raikai machine, and C
The length in the C-plane direction is more than twice the length in the axial direction,
A superconducting powder having a mesh size of 200 mesh or less, which is composed of plate-like particles having grown C plane, was obtained. As a result of observing an SEM image of the powder, it was found that the powder was composed of plate-like particles having a particle size of 10 to 60 μm. As a result of examining the proportion of the plate-like particles using an image analyzer, the proportion of the plate-like particles whose length in the C-plane direction is twice or more the length in the C-axis direction is about 70 vol% of the powder. It was The result of powder X-ray diffraction of the powder is shown in FIG. It was confirmed from FIG. 4 that the (oon) plane (where n is an integer) was emphasized and that the plate-like grain was a grain in which the C plane grew. Next, the powder is filled into an Ag pipe having an inner diameter of 10 mm at a rate of about 2.7 g / cm ² to form a composite conductor, and the composite conductor is 0.1 mm up to a diameter of 3 mm.
Extruded so that the diameter gradually decreases, and 0.0 for diameters of 3 mm or less.
Extruded so that the diameter decreases by 5 mm, and the outer diameter is 1.2 mm A
A thin wire with a thickness of about 0.1 mm was used. The thin wire was further cold-rolled to obtain a tape-shaped wire having a thickness of 0.1 mm. The tape-shaped wire was fired in an oxygen atmosphere at a temperature of 910 ° C. for 5 hours and then gradually cooled to room temperature to obtain a superconducting wire. As a result of measuring the critical current density (Jc) of this superconducting wire at a temperature of 77 K and without applying an external magnetic field, Jc was 4200 A / cm ² .

Next, the Ag tube of this superconducting wire was removed, and the orientation of the plane in the rolling direction of the oxide superconducting material inside the superconducting wire was examined by X-ray diffraction. As a result, as shown in FIG. It was emphasized that it was found that the C planes of the grains were arranged in the longitudinal direction of the superconducting wire (that is, had the preferential direction). It is considered that this is because the C plane was oriented in the longitudinal direction of the wire in the process of wire drawing and rolling by using a material containing a lot of plate-like particles as the oxide superconducting material.

The reason why Jc in Example 3 was significantly larger than that in Example 1 was that plate-like particles having a length in the C-plane direction twice or more the length in the C-axis direction were contained at about 70 vol%. Due to the use of superconducting powder that is used, and because the plate-like particles have extremely small ductility and a small size of 10 to 60 μm, the shape and shape of the plate-like particles before being processed after being processed into a wire are It is considered that the ratio is maintained, the C-planes of the plate-shaped particles having the special shape are arranged in the longitudinal direction of the line, and the sintering is performed in the oxygen atmosphere.

In order to compare with the above-mentioned Example 3 of the present invention, the same raw material mixture as in Example 3 was used to obtain the oxide superconducting material powder under the same conditions except that the pre-baking temperature was 910 ° C. The powder was molded into pellets in the same manner as in Example 5. This pellet was fired in O ₂ for 910 × 5 hours and then pulverized for 1 hour with an agate raikai machine to obtain a superconducting powder. As a result of observing a photograph of an SEM image of the powder, it was found that the powder was composed of particles having a particle size of about 2 to 20 μm and the particle size and the shape were significantly different from the powder shown in Example 3. . The result of powder X-ray diffraction of the powder is as shown in FIG. 6, and the result of FIG. 6 is different from the case of FIG.

Next, using the powder, a tape-shaped superconducting wire having a thickness of 0.1 mm was obtained by the same operation as in Example 3. J of this superconducting wire
As a result of measuring c at a temperature of 77 K and without applying an external magnetic field, Jc was 400 A / cm ² . Next, the Ag tube of the superconducting wire of this comparative material was removed, and the orientation of the surface of the oxide superconducting material in the rolling direction was examined by X-ray diffraction. The result is shown in FIG.

The X-ray diffraction result of FIG. 7 was different from the X-ray diffraction result of FIG. 5 in the case of Example 3.

Example 4 Using the same raw material mixture as in Example 3, Example 3
By the same operation as described above, an agglomerate containing 80 vol% or more of grains having a length in the C-plane direction that is 3 times or more the length in the C-axis direction was obtained. Next, the crushing time of this agglomerate was changed to obtain a large number of powders in which the abundance ratio of plate-like particles was changed. Using this powder, a tape-shaped superconducting wire was produced under the same manufacturing conditions as in Example 3. The Jc of this superconducting wire was measured at a temperature of 77 K without applying an external magnetic field, and the results shown in FIG. 8 were obtained.

From Fig. 8, Jc of superconducting wire is
It has been found that when it exceeds 50 vol%, preferably 60 vol% or more, a remarkable improvement is obtained. The abundance ratio of the plate-like particles was determined from an SEM image of the powder of the oxide superconducting material using an image analyzer.

Example 5 30.6 g of Y (NO ₃ ) ₃ .2H ₂ O, 41.8 g of Ba (NO ₃ ) ₂ and Cu
(NO ₃₎ the 58.0g of 2 _· 3H ₂ O and 2 of an aqueous solution, to which oxalic acid 100g of triethylamine 120g as one of an aqueous solution, dropwise stirring the latter solution at a rate of 1 / min to the former aqueous solution in the micro switch Yubu pump did. The resulting slurry was subjected to solid-liquid separation to collect solids. 12 solids obtained
After drying at 0 ° C., it was decomposed by heating at 400 ° C. for 3 hours. The obtained solid material was finely pulverized, put in a crucible of magnetic alumina, and fired at 800 ° C. for 3 hours. The step of finely pulverizing the obtained solid material and firing at 900 ° C. for 3 hours was repeated 3 times to obtain a superconducting powder. The powder is hydraulically pressed to a diameter of 30 m.
When the pellet was formed into a pellet having a shape of m and a thickness of 1.5 mm, and the pellet was baked in O ₂ at 950 ° C. for 15 hours to grow the C-plane sufficiently, the length in the C-plane direction was in the C-axis direction. An agglomerate containing 60 vol% or more of plate-like particles having a length four times or more than the length was obtained. The agglomerates were crushed for 30 minutes with an agate raikai machine,
An oxide superconducting powder composed of plate-like particles with a particle size of 200 mesh or less was prepared. The powder is then applied to the wall with an outer diameter of 15 mm and 0.1 mm on the wall.
A 300 m long, 0.5 mm thick Ag mesh tube with a large number of through-holes of diameter is filled at a rate of 2.7 g / cm ³ to make a composite conductor, and the diameter is reduced by about 0.1 mm in each extrusion process. A thin wire with an external diameter of 1 mm was applied. This thin wire was formed into a tape-shaped wire rod having a thickness of 0.2 mm by cold rolling. Next, the tape-shaped wire was fired in an oxygen atmosphere at a temperature of 910 ° C. for 10 hours and then gradually cooled to room temperature to obtain an oxide superconducting wire. Jc value of the superconducting wire was 6600 A / cm ² when measured at liquid nitrogen (77 K) temperature and without applying an external magnetic field.
It was.

Example 6 Commercially available Bi ₂ O ₃ , SrCO ₃ , CaCO ₃ and CuO were weighed out so that the molar ratio of Bi, Sr, Ca and Cu was 1: 1: 1: 2. First SrCO ₃ , C
The aCO ₃ and CuO powders were mixed for 1 hour with an agate raikai machine to obtain a powder mixture. This powder mixture was placed in an alumina crucible and pre-calcined at a temperature of 950 ° C. for 42 hours in the air, and then the weighed Bi ₂ O ₃ powder was added to this pre-calcined material and mixed for 1 hour with a Lycal machine to obtain a powder. . 82 in air
The operation of pre-calcining at a temperature of 0 ° C. for 12 hours and then pulverizing this was repeated twice to obtain a powder. This powder was molded into a pellet with a diameter of 30 mm and a thickness of 1.0 mm, and
By firing for 48 hours at a temperature of 80 ° C and growing the C-plane sufficiently, oxide superconducting lumps containing 80 vol% or more of plate-like grains whose length in the C-plane direction is 5 times or more the length in the C-axis direction I got a thing. The agglomerate is crushed for 30 minutes by using an agate raikai machine, and the length in the C-plane direction is 3 times or more the length in the C-axis direction. A superconducting powder composed of plate-like particles having a grown C-plane was obtained. The powder was filled in an Ag tube having an inner diameter of 6 mm to obtain a composite conductor. This composite conductor was drawn into a thin wire with an outer diameter of 1.2 mm. Next, this thin wire was cold-rolled into a tape-shaped wire having a thickness of 0.1 mm. The tape-shaped wire was fired in an oxygen atmosphere at a temperature of 910 ° C. for 10 hours and then furnace-cooled to room temperature to obtain a superconducting wire. As a result of measuring Jc of this superconducting wire at 77K in a state where an external magnetic field is not applied, the value of Jc is 3800A / cm ²
It was.

Example 7 The same commercially available Y ₂ O ₃ , BaCO ₃ , CuO as in Example 3 was added to Y, Ba and Cu.
Were weighed so that the molar ratio was 1: 2: 3, water was added and ball milling was performed to obtain a uniform powder mixture. The powder mixture was heated to 150 ° C. to evaporate and remove water. When the powder mixture was fired in O ₂ at 975 ° C. for 10 hours to grow the C-plane sufficiently, 70 vol% or more of grains having a length in the C-plane direction that is 3 times or more the length in the C-axis direction were included. A lump of oxide superconducting material was obtained. The lump is made into a powder of 200 mesh or less,
Under the same conditions as in Example 3, an Ag tube having an inner diameter of 20 mm or more was sealed and extruded. After processing, the critical current density was measured for the sample further baked at 900 ° C for 5h in O _2.
Jc = 3 under the condition of K temperature and no external magnetic field applied
It was 800 A / cm ² .

For comparison with Example 7, as a comparative material, the same raw material and the same method as in Example 7 were used to generate a lump having a C-plane grown, and then the lump was crushed to obtain a comparative material powder. . The pulverization time is extended and 70 vol% or more of the pulverized powder is C
The particles were 1.5 times or less the length in the C-plane direction with respect to the axial length. The powder was enclosed in an Ag tube and drawn. After drawing, the critical current density was measured for the sample further baked in 900 ° C x 5h in O ₂ ; Jc = 77K, 0T
It was 1200 A / cm ² .

Example _{8 Y (NO 3) 3 ·} 2H 2 O, Ba (NO 3) 2 and Cu (NO _{3) 2} · 3H
_{Using 2} O as a starting material and using the same method as in Example 5, a fine and uniform powder mixture was obtained. After drying the powder mixture, 90
When it was baked in O ₂ at 0 ° C. for 15 hours to grow the C-plane sufficiently, a lump containing 60 vol% or more of grains having a length in the C-plane direction of 4 times or more was obtained. The agglomerate was made into a powder of 200 mesh or less, enclosed in an Ag tube having an inner diameter of 15 mm, and extruded in the same manner as in Example 5 to obtain the same superconducting wire as in Example 5. The sample that was further heat-treated in 930 ℃ × 5h, O ₂ had a critical temperature of 88K and 77K.
The critical current density at K was 3500 A / cm ² .

Example 9 FIG. 10 is a sectional view of a superconducting wire manufactured as a multifilamentary wire by the same method as in Example 3. (A) is a silver matrix 1 having an outer diameter of 2.7 mm and 271 superconducting wire elements 2 of about 50 μm are embedded therein, and (b) is a silver matrix 1 having an outer diameter of 2.1 mm.
397 of the superconducting wire elements 2 of about 40 μm are embedded therein. These multi-core superconducting wires are about 0.1 m of the third embodiment.
It is possible to repeatedly obtain a method in which a predetermined number of thin wires of m are bundled until the number of wires corresponds to the number of superconducting wires described above and the wires are thinned. When the above-mentioned predetermined number and diameter have been reached, the final heat treatment is performed in the same manner as in the third embodiment.
Thus, electromagnetic stability can be obtained by the extra fine multi-core wire.

〔The invention's effect〕

As described above, according to the present invention, the oxide superconducting material forming the oxide superconducting wire has a preferred orientation that includes plate-like particles and is arranged in the longitudinal direction of the superconducting wire. It was possible to obtain a high superconducting wire.

It is obvious that this effect can be obtained not only in the example but also in the case of using another superconducting material composed of plate-like particles through which an electric current easily flows, or another metal tube.

The superconducting wire according to the present invention is a rotor and stator coil of a rotating machine, an energy storage coil, a fusion device magnet coil, a power transmission and distribution cable, a transformer coil, a particle accelerator coil, an MRI and NMR magnet coil, It can be used as a coil for an electron microscope, a coil for a magnet of an atomic absorption spectrometer, a rotor for a motor of a train, an automobile, an elevator, an escalator, a coil for a stator, and a coil for a magnet of a linear motor car.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a configuration of a superconducting wire of an embodiment of the present invention, FIG. 2 is a perspective view showing a composite conductor before thinning in a process of manufacturing the superconducting wire of the embodiment, and FIG. A graph showing the orientation distribution of the crystal particles in the produced superconducting wire, FIG. 4 is a graph showing the results of examining the orientation of the powder by X-ray diffraction, and FIG. 5 is a graph showing the powder filled in an Ag pipe. FIG. 6 is a graph showing the results of examining the orientation of plate-like particles by X-ray diffraction of a cross section parallel to the longitudinal direction of the superconducting wire obtained by drawing, and FIG. 6 is a graph of the oxide superconducting material of the comparative material. It is a graph which shows the result of having investigated the direction of powder by X-ray diffraction.
The figure shows the orientation of the plate-like particles by X-ray diffraction of a cross section parallel to the longitudinal direction of the superconducting wire obtained by filling the tube made of Ag with the powder of the comparative material under the same conditions as in FIG. Fig. 8 is a graph showing the results of the investigation of Fig. 8 shows the proportion of plate-like particles present in the powder of the oxide superconducting material, which is a raw material for forming the superconducting wire, and the critical current density of the superconducting wire made from the powder ( Fig. 9 is a graph showing the relationship with Jc), Fig. 9 is a model view showing the C plane and C axis of oxide superconducting particles having a perovskite type crystal structure, and Fig. 10 is a cross-sectional view of a multicore superconducting wire. 1 ... Metal tube, 2 ... Superconducting material, 11 ... Copper tube before thinning, 21 ... Plate-shaped particles, 22 ... Non-oriented superconducting material.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeo Yamazaki 4026 Kuji Town, Hitachi City, Hitachi, Ibaraki Prefecture Hitachi, Ltd. Hitachi Research Laboratory (72) Ken Takahashi 4026 Kuji Town, Hitachi City, Hitachi, Ltd. Hitachi Research Co., Ltd. In-house (72) Inventor Tadahiko Miyoshi 4026 Kuji-machi, Hitachi, Hitachi, Ibaraki 4026 Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Nagashiro Kitazawa 4026, Kuji-cho, Hitachi, Ibaraki Hitachi, Ltd. (72) Inventor, Hitachi Nakasawa New Year 2 Stock company, 832, Horiguchi, Katsuta, Ibaraki, Hitachi Ltd., Katsuta Plant, Hitachi (72) Inventor, Yukio Takeda, 1 Horiyamashita, Hadano, Kanagawa, Ltd., Kanagawa Plant, Hitachi, Ltd. (72) Inventor, Takae Nakamura, Ibaraki 4026 Kuji-machi, Hitachi, Ltd. Hitachi Research Laboratory, Hitachi, Ltd. (56) References JP-A-63-279513 (JP, A) JP-A-63-279514 (JP, A) JP-A 1-261230 (JP, A) JP-A 1-258832 (JP, A)

Claims (5)

(57) [Claims] 1. A superconducting material comprising: a metal tube extending in a longitudinal direction; and an oxide superconducting material, which is filled in the tube and is composed of superconducting oxide particles having a perovskite type crystal structure and bonded to each other. The oxide particles have plate-like particles having a dimension in the C-plane direction larger than the dimension in the C-axis direction, and the oxide superconducting material is at least one of Y, Ba, Cu, O, rare earths and alkali metals. And C of the superconducting oxide particles.
In the oxide superconducting wire whose surface has a preferred orientation oriented in the longitudinal direction, the superconducting oxide particles have the plate-like particles in a proportion of greater than 50 vol%, and the oxide superconducting material is bismuth and thallium. An oxide superconducting wire comprising at least one of the above. 2. The oxide superconducting wire according to claim 1, wherein the dimension of the plate-like particles in the C-plane direction is twice or more the dimension in the C-axis direction. 3. A method of manufacturing an oxide superconducting wire, comprising the steps of preparing a metal tube extending in a longitudinal direction, and including superconducting oxide particles having a perovskite type crystal structure, wherein C
It is an oxide superconducting material that contains plate-like particles having a dimension in the plane direction that is at least twice as large as the dimension in the C-axis direction at a ratio of greater than 50 vol% of the oxide superconducting material powder, and Y, Ba, Cu, O, and Preparing an oxide superconducting material containing at least one selected from the group consisting of rare earths, alkali metals, bismuth and thallium, and drawing a composite conductor in which the oxide superconducting material is filled in the tube in the longitudinal direction. And / or rolling into a wire, whereby the oxide superconducting material has a preferred orientation in which the C-plane of the particles of the oxide superconducting material powder is oriented in the longitudinal direction, and the processed composite conductor is heat treated. And a step of sintering the oxide superconducting material. 4. The method for producing an oxide superconducting wire according to claim 3, wherein the metal tube is a tube having a large number of through holes in the wall of the tube. 5. The method for producing an oxide superconducting wire according to claim 3, wherein the oxide superconducting wire has a particle size of 200 mesh or less.