JPH09295873A - Production of oxide superconductive conductor and oxide superconductive conductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an oxide superconductive conductor enabling the normal continuous growth of a crystal of oxide superconductor and the growth of the crystal of oxide superconductor while keeping excellent crystal orientation and to obtain the oxide superconductive conductor excellent in mechanical strength and critical current density under magnetic field. SOLUTION: Raw material powder mainly consisting of powdery oxide superconductive material is shaped, sintering the resultant shaped material to produce a raw sintered rod 21, and melting and solidifying the obtained raw sintered rod 21 by melt-solidification to produce an oxide superconductive conductor. This production method includes at least a process adding 3-10wt.% of silver powder and 0.5-1wt.% of platinum powder to the raw material powder. The oxide superconductive conductor, which is produced by shaping and sintering the raw material powder mainly consisting of the powdery oxide superconductive material and melting and solidifying the obtained rod 21, contains 3-10wt.% of silver and 0.5-1wt.% of platinum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an oxide superconducting conductor used in a superconducting current lead wire for supplying power to a superconducting device immersed in a cryogenic refrigerant, and an oxide superconducting conductor. is there.

[0002]

2. Description of the Related Art Generally, superconducting devices such as an AC superconducting coil and a superconducting transformer are used by being immersed in a cryogenic refrigerant such as liquid helium, and a superconducting wire derived from those devices is used in a refrigerant. Connected to a current lead led from an external power supply. As the current lead wire, it is said that it is desirable to use a superconducting wire rather than a normal conducting wire. Therefore, use of a Y-Ba-Cu-O-based superconducting conductor as a superconducting current lead wire has been considered.

[0003] As a conventional method for manufacturing this type of Y-Ba-Cu-O-based superconductor, first, Y-Ba-Cu-O is used.
The raw material sintered rod is prepared by molding and then sintering the raw material superconducting material powder, and then the raw material sintered rod is melt-solidified by a melt-solidification method. As the melting and solidifying method here, an annular electric furnace is used, and the raw material sintering rod is introduced into the electric furnace from the upper end side, and the raw material sintering rod is gradually pulled up to form a raw material sintering rod. The melted portion formed partially is gradually moved from the upper end portion side to the lower end portion side, and the portion led out from the electric furnace is cooled and solidified, and the solidified portion is made of the Y-Ba-Cu-O-based superconductor. It had formed crystals.

[0004]

By the way, Y-Ba-Cu obtained by the above-mentioned method for producing an oxide superconducting conductor is described.
The -O-based superconducting conductor is unsatisfactory in terms of critical current density (Jc) and mechanical strength. In order to solve these problems, in order to solve these problems, the raw material powder containing the oxide superconducting material powder as the main component is added with Ag powder or A method of adding Pt powder has been considered. However, when Ag powder is added, irrespective of the amount of addition, abnormal solidified matter 12 is generated below the melting portion 9 of the raw material sintering rod 7, as shown in FIG.
Further, the abnormal solidified matter 12 becomes larger as the melt solidification method proceeds (as time passes), and the normal Y-B
The continuous growth of crystals of the a-Cu-O-based superconductor is hindered,
The crystal orientation of the obtained oxide superconductor is lowered, and the critical current density is low. Incidentally, reference numeral 11 in FIG.
Is a growth interface located at the boundary between the fusion zone 9 and the solidification zone 10.

When Pt powder is added, an abnormal coagulated substance similar to that shown in FIG. 4 is produced regardless of the amount of Pt powder added, and the critical current density decreases due to the abnormal coagulated substance. There was a drawback. Therefore, Y-Ba-Cu-O obtained by the above-mentioned method for producing an oxide superconducting conductor is obtained.
The system oxide superconductor has a problem that the critical current density is low under a magnetic field.

The present invention has been made in view of the above circumstances, and it is possible to normally carry out continuous growth of crystals of an oxide superconductor, while maintaining excellent crystal orientation and maintaining the crystal of the oxide superconductor. It is intended to provide a method for producing an oxide superconducting conductor capable of growing GaN, and an oxide superconducting conductor obtained by the method, which has excellent mechanical strength and excellent critical current density under a magnetic field.

[0007]

According to the first aspect of the present invention,
A method for producing an oxide superconducting conductor by molding a raw material powder containing an oxide superconducting material powder as a main component, sintering the raw material powder to form a raw material sintering rod, and melting and solidifying the raw material sintering rod by a melt solidification method. In the raw material powder, silver powder 3 to 1
A method for manufacturing an oxide superconducting conductor, which comprises at least a step of adding 0% by weight and 0.5 to 1% by weight of platinum powder, respectively, is a means for solving the above problems. Also,
The invention according to claim 2 is an oxide superconducting conductor obtained by melting and solidifying a raw material sintering rod obtained by molding and sintering a raw material powder containing oxide superconducting material powder as a main component. 3-10 wt% silver and 0.5-1 platinum in the rod
The oxide superconducting conductor is characterized in that each of them is contained in an amount of 1% by weight.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION An example in which the method for producing an oxide superconducting conductor according to the present invention is applied to a method for producing a Y-Ba-Cu-O based superconducting conductor will be described below. First, YBa ₂ Cu ₃ O _7-x (hereinafter abbreviated as Y123) powder as an oxide superconducting material powder is added to Y ₂ BaCuO ₅ (hereinafter abbreviated as Y211).
Powder, silver powder, and platinum powder are added and mixed to prepare a raw material powder. The mixing ratio of the Y123 powder and the Y211 powder here is about 10 mol: 1 to 5 mol, preferably 1 mol.
0 mol: about 3 to 5 mol, more preferably 10 mol: 4
It is about a mole. When the amount of Y211 powder added exceeds 5 mol, continuous growth of Y123 crystals is hindered, which is not preferable. When the amount of Y211 powder added is less than 1 mol,
It is not preferable because the amount of magnetic flux pinning that causes the high critical current density (Jc) is small.

If only one of silver powder and platinum powder is added to the raw material powder, the surface of the obtained melt-solidified rod becomes rough, or an abnormal solidified substance is formed under the fused part of the raw material sintered rod. Occurs, the continuous growth of Y123 crystals is hindered, and the crystal orientation of Y123 deteriorates. The addition amount of silver powder in the raw material powder is 3 to 10% by weight, preferably 5 to 10% by weight. When the addition amount of the silver powder is less than 3% by weight, abnormal coagulated matter is easily generated,
On the other hand, if the amount of the silver powder exceeds 10% by weight, the distribution of the silver powder in the solidified portion becomes non-uniform, and in particular, the silver powder tends to gather at the center of the solidified portion, and the Y-Ba obtained thereby is obtained.
The current path of the -Cu-O-based superconducting conductor is narrowed, and the superconducting characteristics are undesirably reduced.

The content of platinum powder in the raw material powder is
0.5 to 1% by weight. If the amount of the platinum powder is less than 0.5% by weight, an abnormal solidified product is likely to be generated, which is not preferable. On the other hand, when the amount of platinum powder added exceeds 1% by weight, when the raw material sintered rod is melted and solidified, massive Y123 crystals are easily crystallized in the melted portion which is a liquid phase, and Y123 formed in the solidified portion is easily crystallized. It is not preferable because it lowers the crystal orientation of the crystals.

Then, the mixed raw material powder is compression molded by a room temperature isostatic pressing method (CIP) or the like to prepare a rod-shaped starting material, and the rod-shaped starting material is heated in an oxygen atmosphere at a temperature of 900 to 930 ° C. Then, the raw material sintered rod is manufactured by heating and sintering for about 8 to 24 hours. Then
A raw material sintered rod is melted and solidified by a melt solidification method to produce a melt-solidified rod.

FIG. 1 is a schematic configuration diagram for explaining an electric furnace used in the melting and solidifying method here. The electric furnace 20 has an annular shape, and a hole 23 for passing the produced raw material sintering rod 21 is provided in the center of the electric furnace 20, and a heating means 25 is provided around the hole 23. The raw material sintering rod 21 passed through the hole 23 can be partially heated and melted. The peak temperature of the heating means 25 is set to a temperature higher than the melting point of the raw material sintering rod 21. Further, the temperature distribution in the electric furnace 20 is preferably a temperature gradient necessary for growing the crystal of Y123, for example, the raw material sintering rod 21.
When the melting point of is 950 ° C., it is set to about 160 ° C./cm.

In order to melt and solidify the raw material sintering rod 21 using such an annular electric furnace 20, the raw material sintering rod 21 is introduced into the hole 23 of the electric furnace 20 from the upper end 27 side, The shaft 2 along the longitudinal direction of the raw material sintering rod 21
By gradually pulling up while rotating around 6 as a center, the molten portion 9 partially formed in the raw material sintering rod 21 was gradually moved from the upper end side to the lower end side and was led out from the hole 23. When the portion is cooled and solidified, crystals of Y123 are formed in the solidified portion 10. Here, the growth rate of the Y123 crystal in the solidified portion is limited by the pulling rate of the raw material sintering rod 21 and is set to about 1 to 3 mm /.

Then, the melted and solidified rod is annealed in an oxygen atmosphere at a temperature of 450 to 500 ° C. for about 48 to 150 hours. Thereafter, when the melt-solidified rod is cooled to room temperature, the intended Y-Ba-Cu-O-based superconductor is obtained. This Y-Ba-Cu-O-based superconducting conductor is
3 to 10% by weight of silver and 0.5 to 1% by weight of platinum are contained, respectively. Y-Ba- manufactured as described above
The Cu-O-based superconducting conductor can be suitably used as a superconducting current lead wire for supplying power to a superconducting device immersed in a cryogenic refrigerant.

In the method of manufacturing the Y-Ba-Cu-O-based superconducting conductor of this example, 3 to 10% by weight of silver powder and 0.5 to 1 of platinum powder are contained in the raw material powder containing Y123 powder as the main component.
When the raw material sintered rod 21 formed by sintering the raw material powder after molding is melted and solidified by the melt solidification method, an abnormal solidified matter is generated under the melted portion 9 by adding the respective weight%. It is possible to prevent non-uniform distribution of the silver powder in the solidified portion or the solidified portion, to normally perform continuous growth of Y123 crystals, and to maintain the crystal orientation of the oxide superconductor while maintaining excellent crystal orientation. Can grow. Further, in the Y-Ba-Cu-O-based superconducting conductor manufactured as described above, 3 to 10% by weight of silver and 0.5 to 5% of platinum are used.
Since it contains 1% by weight, it has excellent mechanical strength as compared with a Y-Ba-Cu-O-based superconducting conductor containing only one of silver and platinum, and has a crystal orientation of Y123. Excellent and excellent in critical current density under magnetic field.

In the example of the method for producing the oxide superconducting conductor, when the raw material sintered rod is melted and solidified, the melted portion partially formed on the raw material sintered rod is changed from the upper end side to the lower end side. Although the case of adopting the one-way melting and solidifying method in which the melting portion is gradually moved to the above is not limited to this, the melting portion may be gradually moved from the lower end side to the upper end side, or the melting portion is moved to the upper end side. A two-way melt solidification method may be employed in which the melted portion is gradually moved from the lower end side to the lower end side after being gradually moved from the part side to the lower end side. In the example of the method for manufacturing the oxide superconducting conductor described above, the case of manufacturing the Y-Ba-Cu-O-based superconducting conductor has been described. However, the AB-Cu-O-based (where A is La, Ce, Y, Sc, Yb, etc. 1 of the IIIa group elements of the periodic table
The same can be applied to the case of producing a superconducting conductor of the type (1) or more, and B represents one or more elements of Group IIa of the periodic table such as Sr and Ba.

[0017]

Example (Experimental Example 1) YBa ₂ Cu ₃ O _7-x (Y123) powder and Y ₂ B
aCuO ₅ (Y211) powder in a ratio of 10 mol: 3 mol, Ag powder 0 to 10 wt%, Pt powder 0 to 0.5
Raw powder mixed with wt% (Sample Nos. 1 to 4)
Was prepared. The composition of the raw material powder here is shown in Table 1 below.

[0018]

[Table 1]

Then, the mixed raw material powder was compression-molded by a room temperature isostatic pressing method at a molding pressure of 2000 kg / cm ² to produce a rod-shaped starting material. These rod-shaped starting materials were sintered in an oxygen atmosphere at 900 ° C. for 8 hours to prepare raw material sintered rods. Next, these raw material sintered rods were melted and solidified by the unidirectional melting and solidifying method to prepare a melted and solidified rod. In the unidirectional melting and solidification method here, an annular electric furnace was used, the peak temperature of the electric furnace was set to 1000 ° C., and the temperature gradient was 160 ° C./cm at 950 ° C. Further, when the raw material sintered rod is melted and solidified, the raw material sintered body is passed through the electric furnace while being rotated around an axis along the longitudinal direction, and YBa ₂ Cu ₃ O _7-x (Y1
The crystal of 23) was grown at a growth rate of 1 mm / h. Next, the melted and solidified rod was annealed at a temperature of 500 ° C. in an oxygen atmosphere for about 48 hours and then cooled. The size of the melting and solidifying rod obtained here has a diameter of 2 to 3 mm,
The length was 20 to 100 mm.

Next, the appearance of the obtained melt-solidified rod was examined. The result is shown in FIG. 2 shows the sample No. It is a figure which shows the external appearance of the fusion solidification rod obtained using the raw material powder of 1-4, FIG.2 (a) is Pt, Ag powder, and neither Pt powder nor sample sample No. 1
Melted and solidified rod produced by using the raw material powder of No. 3, and (b) is sample No. in which only 0.5 wt% of Pt powder is added. Two
Melted and solidified rod manufactured by using the raw material powder of No. 1, (c) is sample No. 10 in which only 10% by weight of Ag powder is added. Melt-solidifying rod manufactured using the raw material powder of No. 3, (d) is A
Sample No. 10 to which both 10% by weight of g powder and 0.5% by weight of Pt powder were added. 4 is a melting and solidifying rod produced by using the raw material powder of No. 4.

As is clear from the results shown in FIG.
The melt-solidification rod to which neither g powder nor Pt powder is added, or the melt-solidification rod to which only one of Ag powder and Pt powder is added has a rough surface and has an undesired abnormal solidification substance under the melting portion. , Y123 continuous growth was hindered. On the other hand, the melt-solidified rod to which both Pt powder and Ag powder are added has a dense surface and no abnormal solidified material is observed, and it can be seen that Y123 crystals can be continuously grown.

Experimental Example 2 YBa ₂ Cu ₃ O _7-x (Y12
3) The ratio of powder to Y ₂ BaCuO ₅ (Y211) powder is 10
Mol: 3 mol of powder mixed with 3 wt% of Ag powder and 0.5 to 3 wt% of Pt powder (Sample N
o. 5-7) were prepared. The composition of the raw material powder here is shown in Table 2 below. Then, using the mixed raw material powders, a melting and solidifying rod was produced in the same manner as in Experimental Example 1 described above.

[0023]

[Table 2]

Next, the crystal structure of the obtained melt-solidified rod was examined by using an optical microscope. The result is shown in FIG.
Shown in FIG. 3 shows sample No. It is a photograph which shows the growth interface of the solidification | melting solidification rod obtained using 5-7 raw material powder, and the crystal structure of a solidification part. 3A is the sample No. (B) Sample No. 5, a melting and solidifying rod produced using the raw material powder of No. 5 (C) Sample No. 6, a melt-solidifying rod manufactured using the raw material powder of No. 6 7 is a melting and solidifying rod produced by using the raw material powder of No. 7.

As is clear from the results shown in FIG. In the melting and solidifying rod manufactured using the raw material powder of No. 7, lumpy Y123 crystals are crystallized in the melting part which is a liquid phase, and the crystal orientation of the Y123 crystals formed in the solidifying part is lowered. I understand. From this result, when Ag powder is added to the raw material powder, the addition amount of Pt powder should be 0.5 to 1% by weight.
It can be seen that it is effective in preventing the crystals of 3 from being crystallized.

Experimental Example 3 YBa ₂ Cu ₃ O _7-x (Y12
3) The ratio of powder to Y ₂ BaCuO ₅ (Y211) powder is 10
3 to 10% by weight of YBaCuO powder and 3 to 10% by weight of Ag and 0.5 to 1% by weight of Pt.
Raw material powders (Sample Nos. 8 to 17) mixed with each other were prepared. The composition of the raw material powder here is shown in Table 3 below. Then, using the mixed raw material powder, YBa ₂ Cu ₃ O _7-x (Y 1
23) Crystal growth rate of 1 mm / h or 3 mm / h
A molten and solidified rod was produced in the same manner as in Experimental Example 1 except that the rod was grown in 1. After growth, the melt-solidification rod was slowly cooled to measure the critical current temperature. Next, by the DC four-terminal method, a critical current (I
c) and the critical current density (Jc) were measured. Table 3 shows the results.
Shown along with.

[0027]

[Table 3]

As is clear from the results shown in Table 3, P
It can be seen that a high critical current density (Jc) can be obtained by adding a specific amount of t powder and Ag powder.

[0029]

As described above, according to the method for producing an oxide superconducting conductor of the present invention, 3 to 10% by weight of silver powder and 0 of platinum powder are contained in the raw material powder containing the oxide superconducting material powder as the main component. By adding 0.5 to 1% by weight respectively,
When the raw material sintering rod formed by sintering this raw material powder is melted and solidified by the melt solidification method, abnormal solidified matter is generated under the melted portion and the distribution of silver powder in the solidified portion is not uniform. It is possible to prevent the oxide superconductor from becoming uniform, to normally perform continuous growth of the oxide superconductor crystal, and to grow the oxide superconductor crystal while maintaining excellent crystal orientation. Further, the oxide superconducting conductor of the present invention contained 3 to 10% by weight of silver and 0.5 to 1% by weight of platinum, respectively, so that only one of silver and platinum was included. Compared to oxide superconductors, mechanical strength is excellent, and the crystal orientation of oxide superconductors is excellent, critical current density is excellent under magnetic field, and power is supplied to superconducting devices immersed in cryogenic refrigerant. It can be suitably used as a superconducting current lead wire or the like.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram for explaining an example of an electric furnace used for melting and solidifying a raw material sintered rod in a method for producing an oxide superconducting conductor of the present invention.

2 is a sample No. of Experimental example 1. FIG. It is a figure which shows the external appearance of the fusion solidification rod obtained using 1-4 raw material powders.

3 is a sample No. of Experimental Example 2. It is a photograph which shows the growth interface of the solidification | melting solidification rod obtained using 5-7 raw material powder, and the crystal structure of a solidification part.

FIG. 4 is a diagram showing an appearance of a Y—Ba—Cu—O-based superconducting conductor manufactured by a conventional method for manufacturing an oxide superconducting conductor.

[Explanation of symbols]

9 ... Melting part, 10 ... Solidification part, 11 ... Growth interface, 20 ...
..Electric furnace, 21 ... Raw material sintering rod, 23 ... Hole, 25 ...
-Heating means, 26 ... Shaft, 27 ... Upper end.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Saito 1-5-1, Kiba, Koto-ku, Tokyo Fujikura Ltd. (72) Inventor Mikio Nakagawa 1-1-5, Kiba, Koto-ku, Tokyo Shareholders Inside Fujikura (72) Inventor Satoshi Kono 1-5-1 Kiba, Koto-ku, Tokyo Stock Company Inside Fujikura (72) Inventor Shigeo Nagaya 1 of 20 Kitakanzan, Otakamachi, Nagoya, Aichi Electric Power Co., Ltd. Electric Power Technology Research Institute (72) Inventor Takaaki Shimonosono 20-1 Kitakousan, Otaka-cho, Midori-ku, Nagoya, Aichi Chubu Electric Power Co., Inc.

Claims (2)

[Claims] 1. A raw material powder containing an oxide superconducting material powder as a main component is molded and then sintered to form a raw material sintered rod, and the raw material sintered rod is melted and solidified by a melt solidification method to form an oxide superconducting material. A method for producing an oxide superconducting conductor, comprising at least a step of adding 3 to 10% by weight of silver powder and 0.5 to 1% by weight of platinum powder in the raw material powder. 2. An oxide superconducting conductor obtained by molding and sintering a raw material powder containing an oxide superconducting material powder as a main component, the raw material sintering rod being melted and solidified, wherein: An oxide superconducting conductor containing 3 to 10% by weight of silver and 0.5 to 1% by weight of platinum, respectively.