JP3155333B2 - Method for producing oxide superconductor having high critical current density - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a novel REBaCuO-based oxide superconductor, and more particularly to a method for producing an oxide superconductor having a high critical current density. Where R
E represents a rare earth element selected from the group consisting of Y, Sm, Eu, Gd, Dy, Ho, Er, and Yb.

[0002]

The REBaCuO-based oxide bulk superconductor has been conventionally known as MTG (Melt Textured Groove).
wth) method (S. Jin et al. Appl. Phys. Lett. Vol 52 No.207 1988
P2974). An example of manufacturing by the MTG method will be described. First, the raw material powder is prepared and molded so as to have a REBa ₂ Cu ₃ O _x composition. The molded body is partially melted and gradually cooled under a temperature gradient to grow a superconducting phase. Thereafter, annealing is performed in an oxygen-enriched atmosphere to add oxygen to the superconducting phase. In this method, RE ₂ B
The aCuO ₅ phase (hereinafter referred to as 211 phase) is not intentionally dispersed, and the critical current density is about 4,000 A / cm ² at 77K, 1T (tesla), which is sufficiently high for practical use. I can't say.

On the other hand, recently, MPMG (Melt Powder Melt Gr
owth) method (H. Fujimoto et al. Proc. of ISS'89 Springer-Verl
ag 1990 P285) was developed, and the critical current density was 77K,
At 1T, it exceeded 10,000 A / cm ² .
An example of manufacturing with MPMG will be described below. First, raw material powders, for example, Y ₂ O ₃ , BaCO ₃ , and CuO are mixed at a predetermined ratio. This may be calcined and pulverized. Further, this powder is heated to a temperature at which the RE ₂ O ₃ phase and the liquid phase coexist, for example, 1
The mixture is heated to 400 ° C. to partially melt the mixed powder (M). Furthermore, it is solidified by cooling. Then crush (P)
Mix and press mold. The molded body is heated to a temperature at which the 211 phase and the liquid phase coexist, for example, 1100 ° C., and is partially melted (M). Thereafter, the superconductor is cooled to a temperature at which the 123 phase which is a superconducting phase is generated, and gradually cooled at a temperature of, for example, 1 ° C./h to generate and grow (G) the 123 phase, thereby producing a superconductor.

[0004] The high critical current density is defined by YBa ₂ Cu
_This was achieved by finely dispersing 211 phases in a ₃ O _x phase (hereinafter referred to as 123 phases). Furthermore, it has been reported that the smaller the size of the 211 phase, the higher the critical current density (M. Murakami et al., Proc. Of M ² S HTSC III Conf.
erence 1991). Therefore, as one means for obtaining a high critical current density, it is important to disperse 211 phases into 123 phases and further reduce the size of 211 phases.

On the other hand, the magnetic levitation force of the superconductor is:
As the critical current density increases and the superconducting crystal becomes larger, it becomes higher (M. Murakami et al., Japanese Journal of Applied
Physics Vol.29 No.11 1990 L1991), it is important to have a high critical current density in order to obtain a high magnetic levitation force. However, as described above, in the MTG method, a superconductor can be manufactured in a relatively simple and small number of steps, but the critical current density is relatively low. Further, although the critical current density is high in the MPMG method, there is a problem that the manufacturing process becomes complicated. Thus,
The present invention provides a method for producing a REBaCuO-based oxide superconductor having a critical current density higher than the critical current density of the superconductor obtained by the MTG method with a simpler and less manufacturing process than the MPMG method. It is.

[0006]

Means for Solving the Problems The present inventors have made RE ₂ C
u ₂ O ₅ (RE is Y, Sm, Eu, Gd, Dy, Ho,
A rare earth element selected from the group consisting of Er and Yb), BaO ₂ , and CuO as raw materials, and mixing and molding, and the molded body is 950 to 1 in which a 211 phase and a liquid phase coexist.
It is heated at a temperature of 250 ° C., and the superconducting phase 12
A superconductor manufactured by gradually cooling and generating a 123 phase by cooling slowly around a temperature at which three phases are formed is a conventional combination of other raw materials, that is, RE ₂ O ₃ , Ba.
O ₂ , CuO, or RE ₂ BaCuO ₅ , REBa
₂ Cu ₃ O _x , or RE ₂ O ₃ , BaCuO ₂ , C
It has been found that the size of the 211 phase dispersed in the 123 phase is smaller than that of a superconductor manufactured in the same manner as described above using uO or the like as a raw material, and that the critical current density and the magnetic levitation force can be further improved. The present invention has been accomplished. Further, when the above raw materials are mixed, rhodium is added in an amount of 0.01 to 2% by weight, or cerium oxide is added to C.
When 0.1 to ₂ % by weight of eO2 is added and the superconductor is manufactured by the above method, the size of the 211 phase dispersed in 123 phases is further larger than that of the superconductor manufactured without adding the additive. It has also been found that the critical current density is smaller and higher.

That is, the method for producing a REBaCuO-based oxide superconductor according to the present invention is a method for producing RE ₂ Cu ₂ O ₅ (RE is a rare earth element selected from the group consisting of Y, Sm, Eu, Gd, Dy, Ho, Er and Yb). ), Using BaO ₂ and CuO as raw materials, mixing and molding, and further performing a heat treatment to partially melt them, and then gradually cooling them at a rate of 0.2 to 20 ° C./h to grow a superconducting phase. That is, it is characterized. REBa which is another invention of the present invention
The method for producing a CuO-based oxide superconductor is described in RE ₂ Cu ₂ O
₅ (RE is Y, Sm, Eu, Gd, Dy, Ho, Er,
Yb represents a rare earth element selected from the group of Yb), Ba
In a method of producing a REBaCuO-based oxide superconductor in which a superconducting phase is grown by mixing and molding an oxide and a Cu oxide as raw materials, and further performing a heat treatment, rhodium is added to the raw materials in an amount of 0.01 to 2% by weight. To do so. Further, the method for producing a REBaCuO-based oxide superconductor according to another invention of the present invention is characterized in that RE ₂ Cu ₂ O ₅ (RE is Y, Sm, Eu, G
a rare earth element selected from the group consisting of d, Dy, Ho, Er, and Yb), Ba oxide, and Cu oxide as raw materials, mixed and molded, and further subjected to heat treatment to form a REBaCuO-based REBaCuO-based material. In the method for manufacturing an oxide superconductor, cerium oxide is added as a raw material in an amount of 0.1 to ₂ % by weight as cerium oxide (CeO2).

An example of the procedure of the method for manufacturing a superconductor according to the present invention will be described below. Accordingly, the present invention will be described in detail.

(Process) First, as a first step of manufacturing a REBaCuO-based superconductor, a molded body before partial melting is manufactured. As RE,
At least one type is selected from Y, Sm, Eu, Gd, Dy, Ho, Er, and Yb. RE ₂ C as raw material powder
A combination of u ₂ O ₅ , BaO ₂ , and CuO is used. These raw material powders are mixed in a predetermined ratio,
A mixed powder made of uO is prepared. At this time, as a method of further improving the critical current density, 0.1 to 2% by weight of platinum or a platinum compound is added, or rhodium is added to 0.02% by weight.
1 to 2% by weight, or 0.1 to cerium oxide
It is also possible to add 2% by weight. As the platinum compound, for example, Pt ₂ Ba ₄ CuO ₉ is used. Further, as the cerium oxide, for example, CeO ₂ , CeB
aO ₃ is used.

(Step) Further, the mixed powder is molded into a desired shape to produce a molded body.

(Process) The molded body is formed in the range of 950 to 1250 generated by the 211 phase.
Heating to the range of ° C. and holding at that temperature for 15 to 90 minutes,
From that temperature, the temperature at which the 123 phase starts to be formed from the 211 phase and the liquid phase, for example, when RE is Y and in air, it is cooled to 1000 ° C. at a cooling rate of 10 to 1000 ° C./h. 0.2 to 20 ° C / h up to 950 ° C
Slowly cool at a cooling rate of. During the slow cooling, for example, the shaped body can be slowly cooled under a temperature gradient of 1 ° C./cm or more so as to maximize the temperature at one end.

(Step) Thereafter, it is possible to cool at an arbitrary cooling rate from 850 to 950 ° C. to room temperature. If necessary, in order to sufficiently add oxygen to the manufactured superconductor, 2 to 50 ° C. in a temperature range of 650 to 300 ° C. in an oxygen-enriched atmosphere.
Hold for 0 hours, or maximum 650 ° C, minimum 300
Cool in a temperature range of 2C for 2 to 500 hours. Thereafter, cooling can be performed at any cooling rate. Thus, as raw materials, RE ₂ Cu ₂ O ₅ , Ba oxide, and
REBaCu with high critical current density using Cu oxide
An O-based oxide superconductor could be manufactured.

FIG. 1 shows RE ₂ Cu ₂ O ₅ (where RE =
Y), polarizing micrographs of a superconductor structure manufactured according to the present invention using BaO ₂ and CuO as raw materials, and FIGS. 2 to 4 are conventional microstructures other than those described in Examples for comparison. It is a polarization microscope photograph of the superconductor structure manufactured without using this invention using a raw material. The size of the 211 phase dispersed in the 123 phase shown in FIG.
Superconductor 1 manufactured from the conventional raw material shown in FIGS.
Obviously, it is smaller than that dispersed in the 23 phases.

FIGS. 5 to 7 show the Y ₂ Cu ₂ O ₅ , Ba
It is a polarization microscope photograph of the superconductor structure manufactured according to the present invention by adding 0.5% by weight of platinum, rhodium, and cerium oxide to O ₂ and CuO raw material powder, respectively. The size of the 211 phase dispersed in the superconductor 123 phase manufactured by adding each of the additives shown in FIGS. 5 to 7 is different from that of the superconductor manufactured without adding the additive shown in FIG. 12
Clearly, it is as small as that which is dispersed in three phases. Therefore, in the superconductor obtained by the present invention, the size of the 211 phase dispersed in the 123 phases is smaller than that of the superconductor not according to the present invention. Therefore, it is clear that the critical current density and the magnetic levitation force also increase. Moreover, the superconductor can be obtained by a simple manufacturing process, and the present invention is effective.

[0015]

EXAMPLES Example 1 Y ₂ Cu ₂ O ₅ , BaO ₂ and CuO were used as starting materials,
Mixing is performed so that the ratio of Y: Ba: Cu is 1.8: 2.4: 3.4. It is further molded and then at 1030 ° C for 20
After heating for 2 minutes and cooling to 1000 ° C in 2 minutes, 890 ° C
The mixture is gradually cooled at a rate of 1 ° C./h until the furnace is cooled. Further, a superconductor was manufactured by heating at 600 ° C. for 1 hour in an oxygen gas stream of 1 atm and then cooling the furnace. FIG. 1 is a polarization microscope photograph of the superconductor crystal thus obtained.

Comparative Examples 1 to 3 Separately, Y ₂ BaCuO ₅ and YB
a ₂ Cu ₃ O _x (Comparative Example 1), Y ₂ BaCuO ₅ and Ba
CuO ₂ and CuO (Comparative Example 2), Y ₂ O ₃ and BaCuO
₂ and CuO (Comparative Example 3), a superconductor was manufactured in the same manner as in Example 1. FIG. 2 (Comparative Example 1), FIG. 3 (Comparative Example 2), and FIG. 4 (Comparative Example 3) are polarization microscope photographs of the structures of three superconductors obtained by using conventional starting materials. As is apparent from a comparison of these, Y ₂ BaC dispersed in the crystal of the superconductor according to the present invention shown in FIG.
The size of uO ₅ was smaller than the size of the superconductor manufactured using the conventional starting materials of Comparative Examples 1 to 3 shown in FIGS.

Example 2 A superconductor was manufactured in the same manner as in Example 1. The starting materials are the same as in Example 1. Y ₂ Cu ₂ O ₅ , BaO ₂ , CuO
Table 1 shows the critical current densities of the superconductors obtained by using the starting material in the magnetization measurement at 77 K and 1 T (tesla).

Comparative Examples 4 to 6 Superconductors were produced in the same manner as in Comparative Examples 1 to 3. As starting materials, Y ₂ BaCuO ₅ and YBa ₂ C similar to Comparative Examples 1 to 3 were used.
u ₃ O _x (Comparative Example 4), Y ₂ BaCuO ₅ and BaCuO
₂ and CuO (Comparative Example 5), Y ₂ O ₃ , BaCuO ₂ and C
uO (Comparative Example 6) was used. 77 of the obtained superconductor
Table 1 shows the critical current density in the magnetization measurement at K, 1T (tesla).

Example 3 A superconductor pellet was produced in the same manner as in Example 1. The pellet size is about 16 mm in diameter and about 7 mm in height. The magnetic levitation force of these pellets was measured using a permanent magnet having a diameter of 12 mm and a surface magnetic flux density of 0.4 T. As shown in Table 2, pellets using Y ₂ Cu ₂ O ₅ , BaO ₂ , and CuO as starting materials were obtained. Was higher than that of pellets produced from other conventional starting materials (Comparative Examples 7 to 9).

Comparative Examples 7 to 9 Superconductor pellets were produced in the same manner as in Comparative Examples 1 to 3. As starting materials, Y ₂ BaCuO ₅ and Y as in Comparative Examples 1 to 3 were used.
Ba ₂ Cu ₃ O _x (Comparative Example 7), Y ₂ BaCuO ₅ and B
aCuO ₂ and CuO (Comparative Example 8), Y ₂ O ₃ and BaCu
O ₂ and using CuO (Comparative Example 9). The pellet size is about 16 mm in diameter and about 7 mm in height. The magnetic levitation force of these pellets was measured using a permanent magnet having a diameter of 12 mm and a surface magnetic flux density of 0.4 T. Table 2 shows the results.

Examples 4 to 10 Sm ₂ C containing RE other than Y instead of Y ₂ Cu ₂ O ₅
u ₂ O ₅ (Example 4), Eu ₂ Cu ₂ O ₅ (Example 5), Gd ₂ Cu ₂ O ₅ (Example 6), Dy ₂ Cu ₂ O
₅ (Example 7), Ho ₂ Cu ₂ O ₅ (Example 8), Er
_A superconductor was manufactured in the same manner as in Example 1 using ₂ Cu ₂ O ₅ (Example 9) and Yb ₂ Cu ₂ O ₅ (Example 10). Table 3 shows the critical current density of the obtained superconductor obtained by magnetization measurement at 77 K and 1 T. The effects were observed in all RE systems.

Examples 11 to 13 A superconductor was prepared in the same manner as in Example 1 except that platinum (Example 11), rhodium (Example 12) and cerium oxide (Example 13) were each added to the raw material at 0.5% by weight. Manufactured. Table 4 shows the results of measuring the critical current density of the obtained superconductor by the same method as in Examples 4 to 10. It is clear that when these were added, the critical current density was considerably improved as compared with the case where they were not added.

Table 1 Starting material and critical current density Starting material Critical current density (77 K, 1 T) (A / cm 2) Example 2 Y ₂ Cu ₂ O ₅ + BaO ₂ + CuO 11, 500 Comparative Example 4 Y ₂ BaCuO ₅ + YBa ₂ Cu ₃ O _x 8,000 Comparative Example 5 Y ₂ BaCuO ₅ + BaCuO ₂ + CuO 7,800 Comparative Example 6 Y ₂ O ₃ + BaCuO ₂ + CuO 6,000

Table 2 Starting materials and magnetic levitation force Starting materials Magnetic levitation force (Kgf) Example 3 Y ₂ Cu ₂ O ₅ + BaO ₂ + CuO 0. 72 Comparative Example _{7 Y 2 BaCuO 5 + YBa 2} Cu 3 O x 0.28 Comparative Example _{8 Y 2 BaCuO 5 + BaCuO 2} + CuO 0.26 Comparative Example _{9 Y 2 O 3 + BaCuO 2} + CuO 0. 27

Table 3 Substitution Substance and Critical Current Density Y Substitution Material Magnetic Field Current Density (77 K, 1 T) (A / cm 2) Example 4 Sm 11,000 Example 5 Eu 10,500 Example 6 Gd 10,000 Example 7 Dy 10,500 Example 8 Ho 11,000 Example 9 Er 10,000 Example 10 Yb 9,500

Table 4 Additives and Critical Current Density Additive (addition amount 0.5% by weight) Critical current density (77 K, 1 T) (A / cm 2) Example 11 Platinum 17,500 Example 12 Rhodium 18,000 Execution Example 13 Cerium oxide 16,500

[0027]

As apparent from the above, according to the present invention, an oxide superconductor having a small crystal size and a high critical current density and a high magnetic levitation force can be manufactured by a simple manufacturing process.

[Brief description of the drawings]

FIG. 1 is a photomicrograph of a crystal of a superconductor made from an oxide of Y ₂ Cu ₂ O ₅ , Ba and Cu according to the present invention.

FIG. 2 is a micrograph of a crystal of a superconductor made of Y ₂ BaCuO ₅ and YBa ₂ Cu ₃ O _x .

FIG. 3 is a micrograph of a superconductor crystal made of Y ₂ BaCuO ₅ , BaCuO ₂ and CuO.

FIG. 4 is a micrograph of a superconductor crystal made of Y ₂ O ₃ , BaCuO _2, and CuO.

FIG. 5 is a micrograph of a superconductor crystal obtained by adding platinum to a raw material according to the present invention.

FIG. 6 is a micrograph of a superconductor crystal obtained by adding rhodium to a raw material according to the present invention.

FIG. 7 is a micrograph of a superconductor crystal obtained by adding cerium oxide to a raw material according to the present invention.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akihiro Kondo 1-14-3 Shinonome, Shinonome, Koto-ku, Tokyo Within the Superconductivity Engineering Laboratory, International Superconducting Technology Research Center (72) Inventor Hiroyuki Fujimoto Tokyo 1-14-3 Shinonome, Koto-ku, Tokyo International Research Institute for Superconducting Technology, Superconductivity Engineering Research Laboratory (72) Masato Murakami 1-14-3, Shinonome, Shinonome, Koto-ku, Tokyo International Research Center for Superconducting Technology Inside the Superconducting Engineering Laboratory (72) Naomi Koshizuka, Inventor 1-14-3 Shinonome, Koto-ku, Tokyo International Superconducting Technology Research Center Inside the Superconducting Engineering Laboratory (72) Inventor Shoji Tanaka Tokyo 1-14-3 Shinonome, Koto-ku International Research Institute for Superconducting Technology, Superconductivity Engineering Laboratory (56) References JP JP-A-1-160825 (JP, A) JP-A-1-93461 (JP, A) JP-A-2-204322 (JP, A) JP-A-3-141512 (JP, A) JP-A-63-291857 (JP) , A) (58) Fields surveyed (Int. Cl. ⁷ , DB name) C01G 1/00-3/00

Claims (5)

(57) [Claims] 1. RE ₂ Cu ₂ O ₅ (RE is Y, Sm, E
a rare earth element selected from the group consisting of u, Gd, Dy, Ho, Er, and Yb) , BaO ₂ , and CuO as raw materials, followed by mixing and molding, followed by heat treatment.
After partial melting, slowly cool at a rate of 0.2-20 ° C / h
Wherein the growing superconducting phase Te, REBaC
A method for producing a uO-based oxide superconductor. 2. The REBaCuO-based oxide superconductor according to claim 1, wherein said partial melting temperature is 950 to 1250 ° C.
How to make the body. 3. adding from 0.1 to 2% by weight of platinum or platinum compounds as a platinum material, any of claim 1 or 2
For producing REBaCuO-based oxide superconductors
Law. 4. RE ₂ Cu ₂ O ₅ (RE is Y, Sm, E
u, Gd, Dy, Ho, Er, Yb
Rare earth element), Ba oxide, and Cu oxide
Using the product as a raw material,
REBaCuO-based oxide to grow superconducting phase
In a method for manufacturing a superconductor , rhodium is used as a raw material in an amount of 0.0
REBaCu, characterized by being added in an amount of 1 to 2% by weight.
A method for producing an O-based oxide superconductor. 5. RE ₂ Cu ₂ O ₅ (RE is Y, Sm, E
u, Gd, Dy, Ho, Er, Yb
Rare earth element), Ba oxide, and Cu oxide
Using the product as a raw material,
REBaCuO-based oxide to grow superconducting phase
The method of manufacturing a superconductor, characterized by adding 0.1 to 2% by weight of the raw material cerium oxide as cerium oxide (CeO _2), REBaCuO-based oxide superconductor
How to make the body.