JPH0741394A - Production of large-size single crystal or oxide superconductor - Google Patents

Abstract

PURPOSE:To obtain a large-size single crystal of oxide superconductor with a high reproducibility by stacking pellets of Y or rare earth element compds. and pellets of other rare earth metal element compds. in a specified order and heattreating the resultant. CONSTITUTION:The crystal of oxide superconductor expressed by the formula (R is Y or rare earth metal element) is produced by the following method. First, R compd., Ba compd., and Cu compd. are weighed to satisfy R:Ba:Cu included in the region defined by 55:10:35, 40:40:20, 10:60:30, and 10:25:65. Then, at least one compd. of these compds. are selected, mixed, and burnt or molten, and then mixed with the remaining compds. to form pellets. The obtd. pellets are stacked in the order from top to bottom such as Sm, Eu, Gd, Dy, Y, Ho, and Er. The obtd. stacked body is heated at 1000-1300 deg.C to form a R2Ba1Cu1O6 phase and a liquid phase, and then slowly cooled down to room temp.

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 a large single crystal composed of an oxide superconductor, more specifically, R ₁ Ba ₂ Cu which exhibits superconducting characteristics with a high critical current density even under a strong magnetic field. _{The present} invention relates to a method for producing a large single crystal oxide superconductor represented by ₃ O _7-x (R is a mixture of one or two or more elements selected from the group consisting of Y and rare earth metal elements).

[0002]

_2. Description of the Related Art R ₁ Ba ₂ Cu ₃ O _7-x (R
Is 1 selected from the group consisting of Y and rare earth metal elements
The following two methods are widely known as a method for producing a crystal composed of an oxide superconductor represented by (1) or a mixture of two or more elements).

First, as a seed crystal, Y ₁ Ba ₂ C is used.
u ₃ O higher decomposition temperature than the _{7-x M 1 Ba 2 Cu} 3 O 7-x
(M is one element selected from the group consisting of Sm, Eu, Gd and Dy), a single crystal is prepared, and then Y ₂ B
A powder of Y ₁ Ba ₂ Cu ₃ O _7-x containing an excess of a ₁ Cu ₁ O ₅ was melted at about 1450 ° C., and then poured into a copper plate and rapidly cooled to form a Y ₂ O ₃ phase and a liquid phase. Of the precursor M ₁ B prepared in advance, after being kept at 1100 ° C. for 20 minutes and then cooled to a temperature below the decomposition temperature of the seed crystal.
a ₂ Cu ₃ O _7-x single crystal cleaved surface is gradually cooled while being in contact with this precursor to grow in one direction,
It is a method of obtaining a relatively large single crystal of Y ₁ Ba ₂ Cu ₃ O _7-x .

The other one is Y ₁ Ba as a seed crystal.
M ₁ Ba ₂ Cu ₃ O, which has a higher decomposition temperature than ₂ Cu ₃ O _7-x
A single crystal of _7-x (M is one element selected from the group consisting of Sm, Eu, Gd and Dy) is prepared. Then
_{(Y 1-y Yb y)} 2 Ba 1 Cu 1 O 5 containing excess (Y
_1-y Yb _y) after melting the powder _{1 Ba 2 Cu 3 O 7-} x at about 1450 ° C., by quenching poured into copperplate, Y
_A precursor composed of a ₂ O ₃ phase and a liquid phase is prepared. Next, by changing y in the above composition, several similar precursors were prepared,
Pellets consisting of these precursors were sequentially stacked so that the one with the smaller y value was on the top, held at 1100 ° C for 20 minutes, and then cooled to below the decomposition temperature of the seed crystal, and the cleavage plane of the seed crystal was precursor. It is unidirectionally grown by slow cooling in a state in contact with the _{body, (Y 1-y Yb y} ) 1 Ba 2 Cu 3 O
It is a method to obtain a relatively large single crystal of _7-x .

Namely, this method is, Y _1-y was partially replace Y in _{Yb Yb y Ba 2 Cu 3 O} 7-x (0 ≦ y <
1) shows that as the amount of substitution increases, Y ₁ Ba ₂ C
It utilizes the property that the crystallization temperature is lower than that of u ₃ O _7-x .

However, the above-mentioned conventional manufacturing method has the following drawbacks. That is, according to the former method, in order to obtain a larger Y ₁ Ba ₂ Cu ₃ O _7-x single crystal, a larger M ₁ Ba ₂ Cu ₃ O _{7-x is used.}
The condition is to use a single crystal (seed crystal), but it is extremely difficult to produce a large-sized M ₁ Ba ₂ Cu ₃ O _7-x. Therefore, the size should be limited during actual operation. Since it was unavoidable, the manufactured Y ₁ Ba ₂ Cu ₃ O
The size of the _7-x crystals was also limited.

If a similar process is performed using a large precursor in order to produce a large single crystal, the crystal base point is generated even at a place other than the contact of the seed crystal, and as a result, polycrystallization is avoided. I couldn't do it.

On the other hand, according to the latter method, (Y _1-y Yb
With respect to _y ) ₁ Ba ₂ Cu ₃ O _7-x , there was a problem that it was difficult to make a difference in the crystallization temperature between the samples in which y was changed, and the crystal base points were randomly generated.

[0009]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and R ₁ composed of a larger single crystal.
Reproducibly producing an oxide superconductor represented by Ba ₂ Cu ₃ O _7-x (R is one or a mixture of two or more elements selected from the group consisting of Y and rare earth metal elements). An object of the present invention is to provide a method for producing a large single crystal of an oxide superconductor that can be manufactured.

[0010]

Means for Solving the Problems As a result of intensive studies for achieving the above-mentioned object, the present inventors constructed pellets using Y or a rare earth element compound mixed at a predetermined ratio as a raw material, and the pellets, It is possible to find that a large single crystal of an oxide superconductor can be obtained by stacking and heat-treating a pellet formed using another rare earth metal element compound as a raw material in a specific order, and provide the method of the present invention. It was

That is, according to the present invention, firstly, the general formula R ₁
Production of a crystal composed of an oxide superconductor represented by Ba ₂ Cu ₃ O _7-x (R is one or a mixture of two or more elements selected from the group consisting of Y and a rare earth metal element) The present invention provides a method for producing a large single crystal oxide superconductor characterized by including the following steps (1) to (5).

(1) An R compound, a Ba compound, and a Cu compound are mixed in a molar ratio of R, Ba, and Cu (R: Ba:
Cu) is (55:10:35), (40:40:20), (10:60:
30), a step of weighing so as to be included in the area surrounded by (10:25:65).

(2) At least one of the compounds of (1) above
After taking out one or more and mixing, baking or melting,
Mixing this with the rest of the compound and pelletizing.

(3) In the pellets prepared as in (2) above, Sm, Eu, and
A step of selecting at least three kinds of elements of Gd, Dy, Y, Ho, Er, and Yb, and preparing at least three or more of the selected elements individually or as a mixture.

(4) When at least three kinds of pellets obtained in (3) above are composed of a single R, Sm, Eu, Gd, Dy, Y, Ho, Er, Yb are ordered from the top. In the case where R is a mixture, the composition ratio of R is multiplied by the “calibration numerical value” shown in Table 1, and the larger the numerical value, the higher the step.

[0016]

[Table 1]

(5) The laminated body obtained in (4) is heated to 1000 ° C to 1300 ° C.
R ₂ Ba ₁ Cu ₁ O in the laminate by heating to
After forming the phase ₅ and the liquid phase, the step of gradually cooling to room temperature.

The present invention is secondly based on the general formula R ₁ Ba ₂ Cu ₃
A method for producing a crystal comprising an oxide superconductor represented by O _7-x (R is a mixture of one or two or more elements selected from the group consisting of Y and a rare earth metal element) In the step (2), when mixed with the remaining compound, 0.05 to 5% by weight of Pt is further added and mixed, and the above-mentioned first oxide superconductor large single crystal is produced. It provides a method.

Thirdly, in the present invention, the step of gradual cooling to room temperature in the step (5), R, B, which has been prepared in advance,
In the molar ratio of a and Cu, (R: Ba: Cu) is (55:
10:35), (40:40:20), (10:60:30), (10: 2)
5:65) R ₁ Ba ₂ as contained in the area surrounded by
The above-mentioned first or second large-sized oxide superconductor single-crystal, which is a step of bringing Cu ₃ O _7-x- based oxide superconductor single crystal or oriented crystal into contact with the pellet and gradually cooling to room temperature. A method for producing a crystal is provided.

Fourthly, in the present invention, in the step (5) of gradually cooling to room temperature, the laminate is gradually cooled to room temperature with a temperature gradient from the upper end to the lower end of the laminate. The present invention provides a method for producing a large single-crystal oxide superconductor according to any one of the first to third aspects, which is a step.

Fifth, the present invention is characterized in that the step of forming the pellet in the step (2) is a step of forming into a conical shape with a top end cut.
The present invention provides a method for producing a large single crystal oxide superconductor according to any of 1.

[0022]

According to the method of the present invention, R ₂ Ba ₁ Cu ₁ O ₅ becomes R
_{1 Ba 2 Cu 3 O 7-} x that are finely dispersed in made from large crystal than to obtain an oxide superconductor of _{R 1 Ba 2 Cu 3 O 7} -x is, R in the starting material powder , Ba, and Cu elements must be present in a predetermined ratio, and in the method of the present invention, the molar ratio of (R: Ba: Cu) is set to (5
5:10:35), (40:40:20), (10:60:30), (1
0:25:65).

That is, in (55:10:35), if R is mixed in a ratio larger than this value, or if Ba is mixed in a ratio smaller than this value, the 123 phase in the crystal will not proceed, 40:40:20), R or Ba
If the ratio is larger than this value, the growth of 123 phase in the crystal is not promoted, and if (10:60:30) is mixed with Ba larger than this value, the precipitation of impurities is increased. Then the characteristics deteriorate and (10: 2
5:65), if Cu is mixed in a ratio larger than this value, the liquid phase component increases and the shape cannot be maintained when melted.

R ₂ Ba ₁ Cu ₁ O was prepared by the melting method.
₅ is _{R 1 Ba 2 Cu 3 O 7} -x was finely dispersed in R ₁
In obtaining an oxide superconductor of Ba ₂ Cu ₃ O _7-x , by adding Pt as an additive in an amount of 0.05 to 5% by weight, the R ₂ Ba ₁ Cu ₁ O ₅ phase becomes smaller and the critical current density It will contribute to improvement.

Further, according to the method of the present invention, R ₂ Ba ₁ Cu
₁ O ₅ is _{R 1 Ba 2 Cu 3 O 7} -x made from large crystal than those finely dispersed in _{R 1 Ba 2 Cu 3 O 7} -x oxide superconductor single crystals to reproducibly obtain well- Will be able to. This is because three or more compounds having greatly different crystallization temperatures are used as the R compound, and it is possible to suppress disorderly generation of crystal base points from an unnecessary portion.

Further, R ₁ B obtained by the method of the present invention
a ₂ Cu ₃ O _7-x oxide consisting large single crystal _{superconductors, R 1 Ba 2 Cu 3 O} 7-x was finely dispersed in R ₂
Ba ₁ Cu ₁ O ₅ has a high critical current density because it acts as the center of the magnetic flux pinning.

Furthermore, since the magnetization of the oxide superconductor depends on the size of its crystal, the oxide superconductor obtained by the method of the present invention has a large magnetization, for example, a magnetic shield or a magnetic repulsion force is used. The characteristics related to the magnetic bearing and the like are greatly improved.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited by the following examples.

[0029]

Example 1 An example of a method for producing a large single crystal oxide superconductor of the present invention is shown below.

First, Eu ₂ O ₃ , BaCO ₃ and Cu
Eu: Ba: Cu = 18: 2 in molar ratio of each raw material powder of O
Weigh and mix to a ratio of 4:34, then 850
The powder was obtained by firing at ~ 900 ° C for 30 hours. Next, the obtained fired powder was pelletized by a conventionally commonly used molding method (φ50 mm, thickness 20 mm).

Next, the pellets were placed in a firing furnace.
First, the temperature was raised to 1100 to 1200 ° C., kept in this temperature range for 20 minutes, and then lowered to 1000 ° C. at a temperature dropping rate of 1 ° C./min. This was then gradually cooled to room temperature at a cooling rate of 3 ° C. / min to obtain a polycrystal _{Eu 1 Ba 2 Cu 3 O 7} -x , resulting _{Eu 1 Ba 2 Cu 3 O 7} -x polycrystal A single crystal was cut out from the body and used as a seed crystal.

On the other hand, as a separate step, Dy ₂ O ₃ , BaC
The raw material powders of O ₃ and CuO were mixed in a molar ratio of Dy: B.
After weighing so that the ratio of a: Cu = 18: 24: 34,
BaCO ₃ and CuO were fired at 850 to 900 ° C. for 30 hours to obtain a fired powder, and the obtained fired powder, the Dy ₂ O ₃ powder and 0.5 wt% Pt were added and mixed. Then, this mixed powder was fired, and the fired powder obtained was pelletized by a molding method generally used conventionally (φ75
mm, thickness 20 mm). Further, pellets having a diameter of 75 mm and a thickness of 20 mm were produced in the same manner as above except that Y ₂ O ₃ and Ho ₂ O ₃ were used as the R compound instead of Dy ₂ O ₃ .

Next, the three types of pellets produced as described above were applied to Dy ₁ Ba ₂ Cu ₃ O _7-x 1, Y _{1 from the top.}
Ba ₂ Cu ₃ O _7-x 2 and Ho ₁ Ba ₂ Cu ₃ O _7-x 3 were stacked in this order (Fig. 1), and this laminate was placed in a firing furnace.
First, the temperature was raised to 1100 ° C. in 1 hour, held at 1100 ° C. for 20 minutes, and then lowered to 1080 ° C. at a temperature lowering rate of 1 ° C./min. Then, the seed crystal prepared above is brought into contact with the upper end of the laminated body in the above order, the upper end side of this laminated body is brought to a high temperature state, and a temperature gradient of 10 ° C / cm is provided between the upper and lower end surfaces of the laminated body. The temperature was gradually cooled to room temperature at a temperature decrease rate of 3 ° C./min while controlling so that the temperature was controlled.

The oxide superconductor thus produced was composed of a large single crystal having a substantially uniform crystal orientation, and its critical current density was 2.5 × 10 ⁴ A / cm ² . In addition, the magnetic repulsive force with a magnet (repulsive force at a distance of 0.1 mm using a magnet with a maximum magnetic flux density of about 2.5 kG and an outer diameter of 40 mm), which is an important characteristic for application, was 0.6 k.
It was gf. This is about 1.5 times as much as that produced by the conventional method, which is extremely excellent.

[0035]

Example 2 Another example of the method for producing a large single crystal oxide superconductor of the present invention is shown below.

First, the raw material powders of Sm ₂ O ₃ , BaO and CuO are mixed in a molar ratio of Sm: Ba: Cu = 20: 25: 35.
Were weighed and mixed in such a manner that the ratio was maintained, and held at 1450 ° C. for 20 minutes, then poured into a copper plate and rapidly cooled, and this was crushed to obtain a fired powder. Then, the obtained fired powder is molded into a shape shown in FIG. 2 by a molding method which is generally used conventionally.
That is, a cone having a top diameter of 30 mm, a bottom diameter of 50 mm, and a thickness of 20 mm was cut off to form a shape.

Further, by the same method as described above except that Y ₂ O ₃ was used instead of Sm ₂ O ₃ as the R compound.
A conical crystal having an upper end φ50 mm, a lower end φ75 mm, and a thickness of 20 mm was cut off to prepare a crystal body. Further, by using the same method as described above except using Ho ₂ O ₃ instead of Sm ₂ O ₃ as the R compound, the upper end φ75 mm, the lower end φ100 mm, and the thickness
A 20 mm conical upper part was cut out to prepare a crystal body.
Furthermore, instead of Sm ₂ O ₃ as the R compound, Yb ₂
A crystal having an upper end diameter of 100 mm, a lower end diameter of 100 mm and a thickness of 20 mm was produced by the same method as described above except that O ₃ was used.

Next, the four kinds of crystal bodies produced as described above were processed from the top with Sm ₁ Ba ₂ Cu ₃ O _7-x 4, Y ₁ B.
a ₂ Cu ₃ O _7-x 2, Ho ₁ Ba ₂ Cu ₃ O _7-x 3, Y
b ₁ Ba ₂ Cu ₃ O _7-x 5 were stacked in this order (Fig. 3), and the temperature was first raised to 1100 ° C in 1 hour in a firing furnace, then 1100 ° C.
After holding for 20 minutes at that temperature, the temperature was lowered to 1080 ° C. at a temperature decreasing rate of 1 ° C./min. Next, the upper end side of the laminated body stacked in the above order is brought to a high temperature state, and the upper and lower end surfaces of the laminated body are placed between the upper and lower end surfaces, and
It was gradually cooled to room temperature at a temperature decreasing rate of 3 ° C / min while controlling so that the temperature gradient of ° C / cm was blocked.

The oxide superconductor thus produced was composed of a large single crystal having almost uniform crystal orientation, and its critical current density was 2 × 10 ⁴ A / cm ² .
The magnetic repulsive force was measured in the same manner as in Example 1 after grinding the obtained oxide superconductor into a cylindrical shape having a diameter of 75 mm and a thickness of 60 mm, and it was 0.5 kgf. This is about 1.3 times higher than that produced by the conventional method, which is extremely excellent.

[0040]

Example 3 Another example of the method for producing a large single crystal of an oxide superconductor according to the present invention will be described below.

First, raw material powders of Sm ₂ O ₃ , Dy ₂ O ₃ , BaO and CuO were mixed in a molar ratio of Sm: Dy: B.
A: Cu = 15: 5: 25: 35 were weighed and mixed so as to have a ratio, held at 1450 ° C. for 20 minutes, poured into a copper plate and rapidly cooled, and crushed to obtain a fired powder. Next, the obtained fired powder was pelletized to a diameter of 75 mm and a thickness of 20 mm by a conventionally-used molding method (referred to as "pellet A").

In addition, Y ₂ O ₃ , Ho ₂ O ₃ and Er
₂ O ₃ , BaO and CuO raw material powders were weighed and mixed in the same manner as above except that the molar ratio of Y: Ho: Er: Ba: Cu was 5: 5: 5: 25: 35. By the same method, pellets having a diameter of 75 mm and a thickness of 20 mm (referred to as "pellet B") were obtained.

Furthermore, Y ₂ O ₃ , Ho ₂ O ₃ , Er
The ₂ O _3, each raw material powder BaO and CuO, Y in the molar ratio: Ho: Er: Ba: Cu = 1: 1: 13: 25: except that weighed and mixed in a 35 ratio of the above By the same method, pellets having a diameter of 75 mm and a thickness of 20 mm (referred to as "pellet C") were obtained.

Next, the three types of pellets produced as described above were used as "pellet A", "pellet B", and
Stacked in the order of "pellet C". The order of stacking the pellets A to C was determined by the size of the value calculated by the following calculation. -"Pellet A": 15 x 60 + 5 x 10 = 950- "Pellet B": 5 x 0 + 5 x -10 + 5 x -30 = -200 ・ "Pellet C": 1 x 0 + 1 x -10 + 13 x -30 = -400 Next, the pellets piled up in the above order are first heated to 1100 ° C for 1 hour in a firing furnace, and then heated at 1100 ° C for 20
After holding for 1 minute, the temperature was lowered to 1080 ° C. at a temperature decreasing rate of 1 ° C./min. Then, the pellets piled up in the above order are heated to a high temperature, and the temperature gradient of 3 ° C / min is controlled at room temperature while controlling the temperature gradient of 10 ° C / cm between the upper and lower ends of the pellets. Slowly cooled to.

The oxide superconductor thus produced was composed of a large single crystal having a substantially uniform crystal orientation, and its critical current density was 2.3 × 10 ⁴ A / cm ² . In addition, the obtained oxide superconductor is 75 mm in diameter and 60 mm in thickness.
After grinding into a columnar shape, the magnetic repulsive force was measured in the same manner as in Example 1 and found to be 0.48 kgf. This is about 1.2 times that produced by the conventional method,
It is extremely excellent.

[0046]

Comparative Example 1 First, Y ₂ O ₃ , BaCO ₃ and CuO
Each raw material powder of Y: Ba: Cu = 18: 24: 34 in molar ratio
Were weighed and mixed so that the ratio was. Then Ba
CO ₃ and CuO were calcined at 850 to 900 ° C. for 30 hours, the obtained calcined powder, Y ₂ O ₃ and 0.5 wt% Pt were added and mixed, and then calcined. Then, the obtained fired powder is subjected to φ by a molding method generally used conventionally.
Pellet molding was performed to a thickness of 75 mm and a thickness of 60 mm.

Next, the pellets produced as described above are first heated to 1100 ° C. in 1 hour in a firing furnace and kept at 1100 ° C. for 20 minutes, and then heated to 1080 ° C. at 1 ° C./min.
The temperature was lowered at the cooling rate of. Next, a seed crystal of Sm ₁ Ba ₂ Cu ₃ O _7-x prepared in advance is brought into contact with the upper end of the pellet to bring the upper end of the pellet into a high temperature state, and the upper and lower end surfaces of the pellet are placed at 10 ° C. 3 ℃ / min while controlling so that a temperature gradient of 1 / cm is constructed.
The temperature was gradually decreased to room temperature at the cooling rate.

The oxide superconductor manufactured in this manner was composed of a crystal having an almost uniform crystal orientation at its upper end portion (about 1/3 of the whole), but some of the remaining portion had some. The base point of the crystal nucleus of was generated, and it became polycrystal. The critical current density is 2 × 10 ⁴
An A / cm ^2, was measured for magnetic repulsive force in the same manner as in Example 1, was 0.4 kgf.

[0049]

Comparative Example 2 First, (Y_1-yY_by)₂Ba₁Cu₁O_Five
And (Y_1-yY_by)₂Ba₂Cu₃O _7-xThe molar ratio with
1: 0.4, and the value of y while maintaining this ratio
Mix the mixture weighed to 0, 0, 3, 0, 6 respectively.
Melt separately at about 1450 ° C and then pour the melt onto a copper plate.
Then, it was rapidly cooled and crushed to obtain a fired powder. Then
The fired powder obtained was
Pellets were formed into a diameter of 75 mm and a thickness of 20 mm by the shaping method.

Next, the pellets produced as described above were stacked so that the one with the smaller y value was on the top, and the temperature was first raised to 1100 ° C. in 1 hour in a firing furnace, and the pellets were heated at 1100 ° C.
After holding for 20 minutes, the temperature was lowered to 1080 ° C. at a temperature decreasing rate of 1 ° C./min. Next, Sm ₁ B prepared in advance
A seed crystal of a ₂ Cu ₃ O _7-x was brought into contact with the upper end of the pellet to bring the upper end of the pellet into a high temperature state so that a temperature gradient of 10 ° C / cm was blocked between the upper and lower end faces of the pellet. The temperature was gradually cooled to room temperature at a temperature decrease rate of 3 ° C./min while controlling the temperature.

The oxide superconductor produced in this manner was composed of crystals having an almost uniform crystal orientation at the upper end portion (about 1/2 of the whole), but some were left over. The base point of the crystal nucleus of was generated, and it became polycrystal. The critical current density is 2.2 × 10
⁴ is A / cm ^2, was measured for magnetic repulsive force in the same manner as in Example 1, was 0.42Kgf.

[0052]

As a result of the development of the method of the present invention, it has become possible to reproducibly produce an oxide superconductor of R ₁ Ba ₂ Cu ₃ O _7-x composed of a larger single crystal. The oxide superconductor produced by the method of the present invention is excellent in characteristics such as critical current density and magnetic repulsion.

[Brief description of drawings]

FIG. 1 is a side view showing an example of a laminated structure of crystals according to the method of the present invention.

FIG. 2 is a side view showing the shape of a crystal body produced by the method of the present invention.

FIG. 3 is a side view showing another example of the stacking mode of the crystal bodies according to the method of the present invention.

[Explanation of symbols]

1 ... Dy ₁ Ba ₂ Cu ₃ O _7-x 2 ... Y ₁ Ba ₂ Cu ₃ O _7-x 3 ... Ho ₁ Ba ₂ Cu ₃ O _7-x 4 ... Sm ₁ Ba ₂ Cu ₃ O _{7 -x} 5 ... Yb ₁ Ba ₂ Cu ₃ O _7-x

Front Page Continuation (72) Inventor Shigeo Nagaya 1-20 Kitakanyama, Otaka-cho, Midori-ku, Nagoya-shi, Aichi Chubu Electric Power Co., Inc. Electric Power Technology Laboratory (72) Inventor Naoki Hirano Otaka, Midori-ku, Nagoya-shi, Aichi No. 20 Kitakanyama, Choji Electric Power Research Laboratory, Chubu Electric Power Co., Inc.

Claims (5)

[Claims] 1. A compound represented by the general formula R ₁ Ba ₂ Cu ₃ O _7-x (R is
Y and a mixture of one or more elements selected from the group consisting of rare earth metal elements), the method for producing a crystal comprising an oxide superconductor represented by the following (1) to (5) ) The method for producing a large single crystal of an oxide superconductor characterized by comprising the steps of: (1) R compound, Ba compound and Cu compound
In the molar ratio of Ba and Cu, (R: Ba: Cu) is (5
5:10:35), (40:40:20), (10:60:30), (1
0:25:65) Weighing process so that it is contained within the area surrounded by. (2) A step of taking out and mixing at least one or more of the compounds of the above (1), firing or melting them, and then mixing this with the remaining compounds to form pellets. (3) In the pellet prepared as in (2) above, Sm, Eu, Gd, Dy,
A step of selecting at least three kinds of elements among Y, Ho, Er, and Yb, and manufacturing at least three or more of the selected elements individually or as a mixture. (4) When at least three types of pellets obtained in (3) above are composed of a single R, Sm, E
u, Gd, Dy, Y, Ho, Er, Yb in this order, R
When is a mixture, the step of multiplying the composition ratio of R by the “calibration numerical value” shown in Table 1 and stacking the higher numerical value. [Table 1] (5) The layered product obtained in (4) is heated to 1000 ° C to 1300 ° C to form a phase of R ₂ Ba ₁ Cu ₁ O ₅ and a liquid phase in the layered product, and then gradually heated to room temperature. The process of cooling. 2. The oxide superconductor according to claim 1, wherein 0.05 to 5% by weight of Pt is further added and mixed when mixing with the remaining compound in the step (2). A method for manufacturing a large single crystal. 3. In the step (5) of gradually cooling to room temperature, the (R: Ba: Cu) (R: Ba: Cu) is (55:10:35) in a molar ratio of R, Ba, and Cu that is prepared in advance. ),(Four
0:40:20), (10:60:30), (10:25:65) R ₁ Ba ₂ Cu ₃ O _7-x oxide superconductor single crystal contained in the region surrounded by The method for producing a large single crystal oxide superconductor according to claim 1 or 2, which is a step of bringing oriented crystals into contact with the pellets and gradually cooling to room temperature. 4. The step of gradually cooling to room temperature in the step (5) is a step of gradually cooling to room temperature with a temperature gradient from the upper end to the lower end of the laminate to room temperature. The method for producing a large single crystal oxide superconductor according to any one of claims 1 to 3. 5. The oxide according to claim 1, wherein the step of forming the pellet in the step (2) is a step of forming into a conical shape with a top end cut. Manufacturing method of large single crystal superconductor.