JPH01105409A - Oxide superconductive wire and manufacture thereof - Google Patents

Abstract

PURPOSE:To make a superconductive wire with a high critical current density obtainable by making an oxide superconductive material contain plate-formed particles and have a dominant orientation arranged toward the longitudinal direction of the superconductive wire. CONSTITUTION:A superconductive wire has a longitudinally extended metal tube 1 and an oxide superconductive material 2 consisting of superconductive oxide particles 21 which are filled up into the tube 1 and connected each other. The superconductive oxide particles 21 contain 50vol.% or more plate-formed particles which have the dimension in C-surface direction being larger than that in C-axis direction. The superconductive material 2 has a dominant orientation in which C-surfaces of the oxide particles are arranged longitudinally. Here, the plate-formed particle has the perovskite crystal structure in which the dimension in C-surface direction is larger than that in C-axis direction. Thereby, the oxide superconductive wire which has an increased critical current density can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a superconducting wire and a method for manufacturing the same, and particularly to a superconducting wire with improved critical current density and a method for manufacturing the same.

[Conventional technology]

Conventionally, intermetallic compounds such as Nb5Sn and NbaGe have been known as superconducting materials and have been put into practical use. These intermetallic compounds have a critical temperature (T
c) was only 230 even for the highest NbBGe, and it was necessary to use liquid helium for cooling.

However, in 1987, YBa2Cug07-
It has been discovered that δ-based oxides have a Tc of approximately 900, which is dramatically higher than that of conventional intermetallic compounds. The temperature of this Tc is much higher than 77°K, which is the boiling point of liquid nitrogen, so the oxide superconductor can be cooled with inexpensive liquid nitrogen without using extremely expensive liquid helium, and the superconducting state can be achieved. Obtainable.

Since conventional superconducting materials are metals, it is relatively easy to draw them into wire rods, but since the oxide superconducting materials are ceramics, they have poor ductility and are extremely difficult to turn into wire rods.

Therefore, a method has been reported in which the oxide superconducting powder is packed into a pipe, stretched, and then heat-treated to form a wire (1987 MRS Spring M
eeting, P 219-221).

[Problem to be solved by the invention]

However, the above-mentioned conventional technology has the problem that since the powder is packed into a wire, the contact area between the superconducting powders is small and a high critical current density (Jc) cannot be obtained. Furthermore, the oxide superconducting material has a layered perovskite structure,
There is anisotropy in the direction of current flow. However, in the conventional method, this anisotropy is not considered at all, so depending on the direction of the bonds between particles, it becomes difficult for current to flow between particles, resulting in high Jc.
This is hindering the development of

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

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

[Means to solve the problem]

The above object is achieved by using plate-like particles in which C-planes are grown in the oxide superconducting material used when producing the wire.

The oxide superconducting wire of the present invention includes a metal tube extending in the longitudinal direction, and an oxide superconducting material made of superconducting oxide particles having a perovskite crystal structure filled in the tube and bonded to each other. The superconducting oxide particles include plate-like particles whose dimensions in the C-plane direction are larger than those in the C-axis direction.
The superconducting material has a preferential orientation in which the C-planes of the oxide grains are aligned in the longitudinal direction.

A plate-shaped particle means a particle in which the dimension in the C-plane direction is larger than the dimension in the C-axis direction in a perovskite crystal structure.

The method for manufacturing an oxide superconducting wire of the present invention includes the step of preparing a metal tube extending in the longitudinal direction and the step of forming a superconducting powder having a perovskite crystal structure, wherein the size of the grains in the C-plane direction is C.
a step of preparing an oxide superconducting material containing plate-like particles larger than the axial dimension in a proportion greater than 50 voQ%, and longitudinally wire-drawing a composite conductor in which the tube is filled with the oxide superconducting material. or rolling to form a wire so that the oxide superconducting material has a preferential orientation in which the C-plane of the particles of the oxide superconducting material powder faces in the longitudinal direction, and heat-treating the processed composite conductor to form an oxide sintering the superconducting material.

To form a composite conductor, there are two methods: filling the inside of a tubular metal material with an oxide superconducting material consisting of plate-shaped particles, and a method of filling the inside of the tubular metal material with raw material powder and then heat-treating it to form a plate-shaped compound superconducting material. There are ways to generate particles. Particularly in the latter case, while producing plate-like particles of the oxide superconducting material through heat treatment, the composite conductor may be thinned by wire drawing and/or rolling to orient the plate-like particles. A large number of through holes may be provided in the wall of the metal tube to ensure a sufficient supply of oxygen during sintering of the plate-shaped particles.

The oxide superconductor is a composition consisting of Y, Ba, Cu, and O. Oxide superconductor is Y + B a g Cut
The composition may be composed of at least one selected from the group consisting of Ol, rare earth elements, alkali metals, bismuth, and thallium. The oxide superconducting material for superconducting wire is
plate-like particles having a C-plane whose length in the C-plane direction is at least twice as long as the C-axis direction are oriented toward the longitudinal axis of the wire;
It is preferable that the plate-like particles account for 60 von % or more of the oxide superconducting material.

Oxide high-temperature superconducting materials, such as composite oxides of barium, yttrium, and copper, have a layered crystal structure based on a perovskite type, and electrons can easily flow along the layers within the crystal.

In addition, since the crystal structure is layered, the crystal particles can become plate-shaped by appropriately selecting the heat treatment conditions during generation and the subsequent grinding time, and the crystal particles can be formed into plate-shaped particles in the C-axis direction, which is perpendicular to the C-plane of the plate-shaped particles. In comparison, electrons flow more easily in the C-plane direction. Therefore, when forming such a material into a wire, the critical current density of the superconducting wire is increased by orienting the zero plane of the plate-like particles toward the longitudinal direction of the wire. When the inside of a tubular metal is filled with plate-shaped particles, or when plate-shaped particles are generated by heat treatment after being filled with raw material powder, the plate-shaped particles have no particular orientation and are oriented in any direction. . In the process of wire drawing this composite conductor, the internal particles are also pulled in the longitudinal direction of the wire and compressed in a direction perpendicular to it, so the plate-like particles are oriented with their 0 faces facing the longitudinal direction. do.

An oxide superconducting lump containing plate-like grains grown on the 0-plane is
It is produced by appropriately selecting the firing temperature and time and the grinding time (degree of grinding).

Conventional powders used for making wire rods did not take these conditions into account, so 80voQ% or more
It consisted of particles in which the ratio of the length of the zero plane to the length in the C-axis direction was less than twice. Therefore, as mentioned above, the contact area between the superconducting powders within the wire is small, and the bonding direction between the particles is random, making it impossible to obtain a high Jc. In the present invention, a high Jc is achieved by using powder made of grains grown on the 0-face, in which the length of the 0-face is at least twice the length in the C-axis direction, to form a wire rod. The powder can be obtained by appropriately selecting firing conditions. Firing temperature is 900°C or higher and 1050°C or lower, preferably 970°C or higher and 1025°C
It is as follows. The firing time depends on the temperature; if the temperature is high, a short time is sufficient, but if the temperature is low, a long time is required.

If the firing temperature is lower than 900°C, it is difficult for the 0-plane to grow, and if the firing temperature is higher than 1050°C, the oxide superconducting phase changes into other products.

FIG. 9 shows a perovskite crystal structure of an oxide superconductor. The relationship between the C axis and the 0 plane in the crystal is as shown in the figure. In the powder, the 0 plane corresponds to the arm opening plane, and the C axis is perpendicular to that plane.

[Effect]

The plate-shaped oxide superconducting particles grown with the 0-plane are arranged so that they have a preferential orientation in which the 0-plane is oriented in the longitudinal direction of the wire by processing to obtain a wire, and the 0-plane is oriented in the longitudinal direction of the wire. The shape of the plate-like particles and the proportion of the plate-like particles with this specific shape are maintained. This is because the oxide superconducting material is almost ductile, and the plate-like particles have a shape in which the dimension in the C-plane direction is larger than the dimension in the C-axis direction perpendicular to the 0-plane, and the size of the plate-shaped particles is 10 to 60 μm. This is probably due to the small size.

In this superconducting material, current flows almost only in the C-plane direction due to the anisotropy of the crystal system. The reason why a higher critical current density Jc can be obtained compared to wire rods made using conventional powder is that the 0 plane of this conductive plane is oriented in the direction of current flow, and the connections between grains and holes are bonded in a direction that facilitates current flow. This is probably because it is easy to do.

〔Example〕

Example 1 FIG. 1 shows a configuration 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 zero plane of the plate-like particles 21 is oriented in the longitudinal direction of the wire.

Such a superconducting wire was produced as follows. Second
As shown in the figure, outer diameter 30mm, inner diameter 2゜IIIfl
The inside of the copper tube 11 was filled with superconducting material powder 22. The superconducting material powder 22 contains barium oxide (Bad), yttrium oxide (YzO, +), and copper oxide (CaO).
Baz obtained by mixing Ba and Cu in a molar ratio of 1:2:3 and then heat-treating at 950'C for 5 hours,
aYz, 2Cus07-δ powder. As a result of observing the particle shape of the powder with an optical microscope, most of the particles had a diameter of 30 to 60.
It was found that the particles were composed of plate-like particles with a thickness of 10 to 30 μm. Next, 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 processing, and then held at 950° C. for 5 hours in Ar to form a superconducting wire (
A) was produced.

As a result of measuring the resistance value of the obtained superconducting wire (A), the critical temperature was found to be 91. Also, the critical current density is 95A/d
Met.

On the other hand, in order to compare with this, a predetermined amount of raw material powder was mixed and filled inside a copper tube with an outer diameter of 30 mm and an inner diameter of 20 mm, and the steel tube was extruded and processed into a thin wire with a diameter of 1 mm by wire drawing. Preliminary firing was performed at 950° C. for 5 hours in Ar, and main firing was performed at 950° C. for 5 hours in Ar. The critical temperature of the superconducting wire (B) obtained was 91, and the critical temperature of the superconducting wire (A) was 91.
However, the critical current density was as small as 50 A/d. As a result of analyzing the superconducting material in the superconducting wire (B) by X-ray diffraction, Ba1. sYt,zCua07-
It turned out to be a collection of δ crystal grains. Most of the crystal grains were plate-shaped with a diameter of 30 to 60 μm and a thickness of 10 to 30 μm.

In order to examine the orientation of crystal grains, a 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 analysis device. Here, the orientation of the crystal grains is
It is expressed as the angle between the longitudinal direction of the superconducting wire and the axis (long axis) connecting the two points at the maximum distance on the circumference of the crystal grain. Figure 3 shows the measurement results. In the figure, curve a is for a superconducting wire (A) prepared by filling a copper tube with the superconducting material made of plate-like particles described first in this example and then thinning the wire, and curve a is for comparison. This is the case of the superconducting wire (B) produced by thinning and then heat treatment, which will be described later. As is clear from the figure, in the case of the curved line, the particles have no particular orientation, whereas in the case of the curved line, the particle orientation is biased in the longitudinal direction of the superconducting wire. It is thought that orientation of the particles occurs during the thinning process after filling the plate-like particles, and this is the cause of the increase in critical current density.

Example 2 Barium oxide (BaO), yttrium oxide (Y2O8
) and copper oxide (CuO) were mixed under the same conditions as in Example 1 and filled into a steel pipe with an outer diameter of 30 mm and an inner diameter of 20 mm. This tube was gradually wire-drawn while being heat-treated at 950°C in Ar, processed into a fine wire with a diameter of 1 mm to form a composite conductor, and then further heat-treated at 950°C in Ar for 5 hours to make it superconducting. Line (C) was produced. Similarly, a steel pipe filled with raw material powder was thinned by extrusion processing, and then heat treated twice for 5 hours at 950°C in Ar, and superconducting wire (D
) was created.

The critical temperature of the obtained superconducting wire is 9 for both (C) and (D).
It was at 30. The critical current density (C) is 105A/(
1#, (D) was larger than 58A/cJ1', (C) (7). Results of analyzing the superconducting material in the superconducting wire by X-ray diffraction + (C) and (D) both BazYCus07
It turned out to be a collection of -δ crystal grains. The size of the crystal grains is 30-60 μm for the long axis and 10-30 μm for the short axis.
Met. When the orientation distribution of crystal grains was measured using an image analysis device, no grain orientation was observed for the superconducting wire (D), similar to the curve shown in Figure 3, but for the superconducting wire (C), no grain orientation was observed. Similar to curve a, it was observed that the particles tended to be oriented in the longitudinal direction of the line.

As explained above, according to the method of the present invention, it is possible to fabricate a superconducting wire in which the direction in which the electrons of the plate-like particles tend to flow is oriented in the longitudinal direction of the wire, so that the critical current density can be lowered compared to a case without orientation. It has the effect of nearly doubling the size.

It is clear that this effect can be obtained not only in the embodiment but also when other superconducting materials made of plate-shaped particles through which current flows easily in the plane or other metal tubes are used.

Furthermore, the superconducting wire of the present invention has the effect of improving the critical current density of the oxide superconducting wire.

Example 3 Commercially available powders of Y2O5, BaC0a, and CuO were prepared in such a manner that the molar ratio of Y, Ba, and Cu of these materials was 1:2, respectively.
A total of 20 g was weighed so as to give a ratio of :3, and mixed for 1 hour using an agate laikai machine. The particle size of Y2O3 powder is 2-3
μm, B a COx powder particle size is 2-5 μm, CuO
was 1 to 3 μm. The powder mixture was heated to 950 °C in 02
The procedure of pre-calcining at a temperature of 50° C. for 5 hours and then pulverizing the lumps produced by this pre-calcining was repeated twice to obtain a powder of oxide superconducting material. This powder was molded into pellets with a diameter of 30 mm and a thickness of 1.0 mm using a hydraulic press.
After firing in 02 for 20 hours at 75°C to fully grow the 0-plane, a lump containing 80vOQ% or more of grains whose length in the C-plane direction is 3 times or more the length in the C-axis direction was obtained. Obtained. This lump is crushed for 30 minutes using an agate grinder to produce a superconducting powder of 200 mesh or less, consisting of plate-shaped particles with 0-sided growth and a length in the C-plane direction that is at least twice the length in the C-axis direction. I got it. As a result of observing a SEM image of the powder, it was found that the powder consisted of plate-like particles with a particle size of 10 to 60 μm. As a result of examining the proportion of plate-like particles using an image analysis device, the length in the C-plane direction was 2 times the length in the C-axis direction.
The proportion of plate-like particles, which is more than twice as large as that of the powder, is approximately 70 vol.
It was 1%. The results of powder X-ray diffraction of the powder are shown in FIG. From Figure 4, (o o n) plane (where n is an integer)
was emphasized, and it was confirmed that the plate-like grains were grains in which the 0 side had grown. Next, the powder was filled into an Ag tube with an inner diameter of 10 mm at a rate of about 2.7 g/cJ to make a composite conductor.
This composite conductor is extruded so that the diameter decreases by Q up to 3mm in diameter and 1mm increments, and 0.05m when the diameter is less than 3mm.
Extruded so that the diameter decreases by m increments, and the outer diameter is 1.2 m.
The thin wire was made of mAg material and had a thickness of about 0.1 mm.

This thin wire was further cold rolled to obtain a tape-shaped wire rod with a thickness of 0.1 mm. The tape-shaped wire rod was heated at 910° C. in an oxygen atmosphere.
After firing for 5 hours at a temperature of .degree. C., the wire was slowly cooled to room temperature to obtain a superconducting wire. The critical current density (Jc) of this superconducting wire is 7
As a result of measurement at a temperature of 7°C and without applying an external magnetic field, Jc was 4200 A/d.

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 shown in Figure 5 (o on). It was found that the planes were emphasized and the zero planes of the grains were arranged in the longitudinal direction of the superconducting wire (that is, they had a preferred direction). This is considered to be because the zero plane was oriented in the longitudinal direction of the wire during the wire drawing and rolling processes due to the use of a material containing many plate-like particles as the oxide superconducting material.

The reason why JC was significantly larger in Example 3 than in Example 1 is that about 70 vofi of plate-like particles whose length in the C-opening direction is twice or more than the length in the C-axis direction are contained. Because superconducting powder is used, and the plate-like particles have extremely low ductility and small dimensions of 10 to 60 μm, the shape of the plate-like particles before processing remains unchanged even after being processed into a wire rod. This is thought to be due to the fact that the ratio is maintained, that the 0 faces of the specially shaped plate-like particles are aligned in the longitudinal direction of the wire, and that the particles are sintered in an oxygen atmosphere.

For comparison with Example 3 of the present invention, an oxide superconducting material powder was obtained from the same raw material mixture as in Example 3 under the same conditions except that the preliminary firing temperature was 910°C. The powder was formed into pellets in the same manner as in Example 5. The pellets were fired at 910°C for 5 hours in 02, and then ground in an agate mill for 1 hour to obtain superconducting powder. S of the powder
As a result of observing the EM image, the particle size of the powder was 2 to 20μ.
It was found that the powder consisted of particles of approximately 1.0 m in diameter, and was significantly different in particle size and shape compared to the powder shown in Example 3.

The results of powder X-ray diffraction of the powder are shown in Figure 6, and the results in Figure 6 are different from those in Figure 4 (Oon
) aspects were not emphasized.

Next, using the powder, a tape-shaped superconducting wire with a thickness of O, i mm was obtained by the same operation as in Example 3.

As a result of measuring the Jc of this superconducting wire at a temperature of 77°C and without applying an external magnetic field, the Jc was 400A/a.
#Met. 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 results are shown in FIG.

The X-ray diffraction results in FIG. 7 were different from the X-ray diffraction results shown in FIG. 5 for Example 3.

Example 4 Using the same raw material mixture as in Example 3 and performing the same operations as in Example 3, a lump containing 80 vol% or more of grains whose length in the C-plane direction is three times or more than the length in the C-axis direction was produced. I got something. Next, by changing the grinding time of this lump, a large number of powders with varying proportions of plate-like particles were obtained. A tape-shaped superconducting wire was produced using this powder under the same manufacturing conditions as in Example 3. The Jc of this superconducting wire was measured at a temperature of 77 and without applying an external magnetic field, and the results shown in FIG. 8 were obtained.

From FIG. 8, Jc of the superconducting wire is preferably 60 vol when the proportion of plate-like particles exceeds 50 vol (1%).
% or more, it was found that there was a significant improvement. 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 analysis device.

Example 5 30.6 g of Y(NOa)s・2Hz and 13a(N
41.8 g of Oa)2 and Cu(NOa)2.3
58.0 g of H2O was used as an aqueous solution of 2 fl, and 100 g of oxalic acid and 120 g of triethylamine were used as an aqueous solution of IQ, and the latter aqueous solution was added dropwise to the former aqueous solution at a rate of 1127 w1n and stirred using a microtube pump. The resulting slurry was subjected to solid-liquid separation to collect solid matter. The obtained solid was dried at 120°C and then thermally decomposed at 400°C for 3 hours. The obtained solid was finely ground, placed in a magnetic alumina crucible, and fired at 800°C for 3 hours. The process of finely pulverizing the obtained solid material and firing it at 900° C. for 3 hours was repeated three times to obtain a superconducting powder. The powder was molded into pellets with a diameter of 30 mm and a thickness of 1.5 mm using a hydraulic press, and the pellets were heated at 950°C for 15 hours.
By firing in 0.02 to fully grow the 0-plane, a lump containing 60 voQ% or more of plate-like grains whose length in the C-plane direction was 4 times or more longer than the length in the C-axis direction was obtained. The agglomerate was pulverized for 30 minutes using an agate machine to produce an oxide superconducting powder consisting of plate-like particles with a particle size of 200 mesh or less. The powder was then molded into a tube having a length of 300 mm and a wall thickness of 0.5 m with an outer diameter of 15 mm and a number of through holes of 0.1 mm diameter in the wall.
A composite conductor was prepared by filling an Ag mesh tube with a diameter of 2.7 g/a#, and the composite conductor was processed to reduce its diameter by approximately 0.1 mm in each extrusion process to obtain a thin wire with an external diameter of 1 mm. This thin wire was formed into a tape-shaped wire rod with a thickness of 0.2 mm by cold rolling. Next, the tape-shaped wire was fired at a temperature of 910° C. for 10 hours in an oxygen atmosphere, and then slowly cooled to room temperature to obtain an oxide superconducting wire. When the Jc of the superconducting wire was measured at liquid nitrogen (77K) temperature and without applying an external magnetic field, the Jc value was 6600 A/cJ.

Example 6 Commercially available B 120s, S rcOs, CaC0a and C
The molar ratio of u0irBi, Sr, Ca and Cu is 1:1:
It was weighed so that the ratio was 1:2. First S r COs,
Ca COa and CuO powders were mixed in an agate Laikai machine for 1 hour to obtain a powder mixture.

This powder mixture was placed in an aluminum crucible and heated to 950°C in the atmosphere.
After pre-calcining for 42 hours at a temperature of °C, Bit' was weighed.
3 powder was added to this pre-calcined product and mixed for 1 hour using a Lycal machine to obtain a powder. The powder was heated in air at a temperature of 820°C for 1
The operation of pre-calcining for 2 hours and then pulverizing this was repeated twice to obtain a powder.

This powder was molded into pellets with a diameter of 30 mm and a thickness of 1.0 mm, and the pellets were heated at a temperature of 880°C in the atmosphere for 48 hours.
By firing for a long time and sufficiently growing the 0-plane, an oxide superconducting lump containing 80 voQ% 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 was obtained.

The lumps were crushed for 30 minutes using an agate-made Laikai machine, and then
The length in the C-plane direction is more than three times the length in the axial direction,
A superconducting powder consisting of plate-like particles with the 0-face grown was obtained. The powder was filled into an Ag tube having an inner diameter of 6IIIll 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 is cold rolled to a thickness of 0.1 m.
It was made into a tape-shaped wire rod of m. The tape-shaped wire rod was fired in an oxygen atmosphere at a temperature of 910° C. for 10 hours, and then cooled in a furnace to room temperature to obtain a superconducting wire. The JcO value of this superconducting wire was measured at 77 with no external magnetic field being applied, and the JcO value was 38.00 A/d.

Example 7 Commercially available (7) YzOs, B a CO similar to Example 3
a.

CuO was weighed out so that the molar ratio of Y, Ba and Cu was 1:2:3, water was added, and a uniform powder mixture was obtained by ball milling. The powder mixture is heated to 150°C;
The water was evaporated and removed. The powder mixture was heated at 975°C x 10
h. After firing in 02 and sufficiently growing the 0 side,
A lump of oxide superconducting material was obtained which contained 7°vOΩ% or more of grains whose length in the C-plane direction was three times or more the length in the C-axis direction.

This lump was made into a powder of 200 mesh or less, and sealed in an Ag tube with an inner diameter of 20 mm or more under the same conditions as in Example 3.

Extrusion processing was performed. After processing, further 900℃×5h,
The critical current density of the sample fired in 0.02 was measured and found to be J c = 3800 Ald at a temperature of 77° C. and under conditions where no external magnetic field was applied.

In order to compare with Example 7, a lump with the zero side grown was produced using the same raw materials and the same method as in Example 7, and then the lump was crushed to obtain a comparative powder. . The time of the pulverization treatment was lengthened, and more than '70voQ% of the powder after pulverization was made into particles whose length in the C-plane direction was 1.5 times or less than the length in the C-axis direction.

The powder was sealed in an Ag tube and drawn. After drawing, critical current density was measured for the sample which was further fired at 900°C for 5 hours in Ox, and it was found that Jc=1200A/aj?77 under OT conditions. Met.

Example 8 Y (N 0x)a ・2 HzO, B a (N 0
3) A fine and uniform powder mixture was obtained using the same method as in Example 5 using 2 and Cu(N 08)z·3 H2O as starting materials.

After drying the powder mixture, it was heated at 900°C for 15 hours.

By firing in 02 and sufficiently growing the 0 plane, a lump containing 60 vol % or more of grains whose length in the C-plane direction was 4 times or more was obtained. The lump was made into a powder of 200 mesh or less, sealed in an Al tube with 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. This was further heated at 930°C for 5 hours.

The sample heat-treated in 02 had a critical temperature of 88K.

The critical current density at 77K was 3500 A/a#.

Example 9 FIG. 10 is a cross-sectional view of a superconducting wire manufactured into a multifilamentary wire by the same method as in Example 3. (a) shows two superconducting wire elements 2 of approximately 50 μm in a silver matrix 1 with an outer diameter of 2.7 mm.
(b) is a superconducting wire element 2 with a diameter of about 40 μm in a silver matrix 1 with an outer diameter of 2 and 1 mm.
It has 397 embedded lines. These multicore superconducting wires can be obtained by repeating the method of Example 3, in which a predetermined number of thin wires of about 0.1 mm are bundled and thinned until the number corresponds to the above-mentioned superconducting wire. .

When the aforementioned predetermined number and diameter are reached, final heat treatment is performed in the same manner as in Example 3. In this way, electromagnetic stability can be obtained by using the ultra-fine multifilamentary wire.

〔Effect of the invention〕

As explained above, according to the present invention, the oxide superconducting material constituting the oxide superconducting wire contains plate-like particles and has a preferential orientation oriented toward the longitudinal direction of the superconducting wire, thereby increasing the critical current density. We were able to obtain high-performance superconducting wire.

Note that this effect is applicable not only to the embodiments but also to other superconducting materials made of plate-shaped particles in which current easily flows in the plane.

It is clear that the results can also be obtained using other metal tubes.

The superconducting wire according to the present invention includes coils for rotors and stators of rotating machines, coils for energy storage, coils for nuclear fusion device magnets, cables for power transmission and distribution, coils for transformers, coils for particle accelerators, coils for MHI and NMR magnets, Coils for electron microscopes, magnet coils for atomic absorption spectrometers, trains,
Rotors of electric motors for automobiles, elevators, and escalators,
It can be used as a stator coil or a magnet coil for linear motor cars.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the structure of a superconducting wire according to an embodiment of the present invention, Fig. 2 is a perspective view showing the composite conductor before thinning in the process of manufacturing the superconducting wire of the same embodiment, and Fig. 3 4 is a graph showing the orientation distribution of crystal grains in the superconducting wire that was produced, FIG. 4 is a graph showing the results of examining the orientation of the powder by X-ray diffraction, and 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 a superconducting wire obtained by drawing, and FIG. 7 is a graph showing the results of examining the orientation of the powder by X-ray diffraction.
The figure shows the orientation of plate-like particles by X-ray diffraction on a cross section parallel to the longitudinal direction of a superconducting wire obtained by filling an AgH tube with powder of the comparative material and drawing it under the same conditions as in Figure 5. This is a graph showing the results of the investigation, and Figure 8 shows the ratio of plate-shaped particles present in the powder of oxide superconducting material, which is the raw material for making superconducting wire, and the critical current density (Jc) of superconducting wire made from the powder. ), and FIG. 9 is a graph showing the relationship between the 0 face and C
FIG. 10 is a cross-sectional view of a multicore superconducting wire. DESCRIPTION OF SYMBOLS 1...Metal tube, 2...Superconducting material, 11...Steel pipe before thinning, 21...Plate-shaped particles, 22...Unoriented superconductor (ku)'o (5 (b)

Claims (17)

[Claims] 1. An oxide superconducting wire comprising a metal tube extending in the longitudinal direction, and an oxide superconducting material made of superconducting oxide grains with a perovskite crystal structure filled in the tube and bonded to each other. , the superconducting oxide grains have a proportion of plate-like particles whose dimensions in the C-plane direction are larger than those in the C-axis direction in a proportion greater than 50 vol%, and the superconducting material has a structure in which the C-planes of the oxide grains are oriented in the longitudinal direction. Oxide superconducting wire with aligned preferred orientations. 2. An oxide superconducting wire according to claim 1, wherein the oxide superconducting material is an oxide consisting of Y, Ba, Cu, and O. 3. In claim 1, the oxide superconducting material is a superconducting wire that is an oxide consisting of Y, Ba, Cu, O, and at least one selected from the group consisting of rare earths, alkali metals, bismuth, and thallium. . 4. In any one of claims 1 to 3, plate-like particles whose dimension in the C-plane direction is twice or more larger than the dimension in the C-axis direction are present in a proportion greater than 50 vol% of the oxide superconducting material. Oxide superconducting wire. 5. Claim 4: The oxide superconducting wire according to claim 4, wherein plate-like particles whose dimension in the C-plane direction is twice or more larger than the dimension in the C-axis direction are present in a proportion greater than 60 vol% of the oxide superconducting material. 6. Critical current density at critical temperature is 90A/cm^2
The oxide superconducting wire according to any one of claims 1 to 5 above. 7. The oxide superconducting wire according to any one of claims 1 to 6, which has a critical current density of 3500 to 6600 A/cm^2 at 77°K, which is the boiling point of liquid nitrogen. 8. A method for producing an oxide superconducting wire, the method comprising: preparing a metal tube extending in the longitudinal direction; and superconducting oxide grains having a perovskite crystal structure, the dimensions of which in the C-plane direction are in the C-axis direction. A step of preparing an oxide superconducting material containing plate-like particles larger than 50 vol% in a proportion larger than the method described above, and longitudinally drawing and/or rolling a composite conductor in which the tube is filled with the oxide superconducting material. A step of processing the oxide superconducting material into a wire so that the oxide superconducting material has a preferential orientation in which the C-plane of the grains of the oxide superconducting material powder faces in the longitudinal direction; and heat-treating the processed composite conductor to form the oxide superconducting material. A method for manufacturing an oxide superconducting wire, comprising the step of sintering. 9. The method for producing an oxide superconducting wire according to claim 8, wherein the oxide superconducting material is an oxide consisting of Y, Ba, Cu, and O. 10. In claim 8, the oxide superconducting material is a superconducting wire that is an oxide consisting of Y, Ba, Cu, O, and at least one selected from the group consisting of rare earths, alkali metals, bismuth, and thallium. manufacturing method. 11. In any one of claims 8 to 10, the powder has plate-like particles whose dimension in the C-plane direction is twice or more larger than the dimension in the C-axis direction, which is 50V of oxide superconducting material powder.
A method for producing an oxide superconducting wire, the powder being present in a proportion greater than ol%. 12. In any one of claims 8 to 11, the powder has plate-like particles whose dimension in the C-plane direction is twice or more larger than the dimension in the C-axis direction, which is 60V of oxide superconducting material powder.
A method for producing an oxide superconducting wire, the powder being present in a proportion greater than ol%. 13. 13. The method for manufacturing an oxide superconducting wire according to any one of claims 8 to 12, wherein the metal tube has a large number of through holes in its wall. 14. The method for manufacturing an oxide superconducting wire according to any one of claims 8 to 13, wherein the processed composite conductor is heat-treated in an oxygen atmosphere. 15. The method for manufacturing an oxide superconducting wire according to any one of claims 8 to 15, wherein the oxide superconducting material powder has a particle size of 200 mesh or less. 16. The desired shape and ratio of the plate-like particles contained in the oxide superconducting material powder can be determined by selecting the firing temperature for producing the oxide superconducting material from 900 to 1050°C, the firing time and/or the obtained oxide superconducting material. The method for producing an oxide superconducting wire according to any one of claims 8 to 16, which is obtained by controlling the degree of pulverization of the oxide superconducting wire. 17. Rotor and stator coils for rotating machines, energy storage coils, plasma vessel coils for nuclear fusion devices,
Power transmission and distribution cables, transformer coils, particle accelerator coils, MRI magnet coils, NMR magnet coils, electron microscope coils, atomic absorption spectrometer magnet coils,
The first claim is a magnet coil for a linear motor car, and a rotor and stator coil for electric motors of various transportation facilities.
Various devices comprising the oxide superconducting wire according to any one of items 1 to 17.