JP2012214329A - Superconductive bulk body and method for manufacturing the same, and superconductive bulk magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a superconductive bulk magnet high in magnetic field intensity.SOLUTION: The superconductive bulk magnet is provided by making a superconductive bulk body including a central part (14) of a cylindrical synthetic crystal obtained by removing an upper part (12) and a lower part (13) of a cylindrical synthetic crystal (11) synthesized by a seed crystal fusion method, and making the superconductive bulk body capture the magnetic field.

Description

  The present invention relates to a superconducting bulk body having a high magnetic field capturing ability, a method for producing the same, and a superconducting bulk magnet having a high magnetic field strength.

  Superconducting magnets that generate a much higher magnetic field than permanent magnets have been developed and applied to medical magnetic tomography (MRI) and magnetic levitation trains. As a superconducting magnet, an electromagnet type superconducting coil magnet in which a superconducting wire is wound in a coil shape is generally used. Recently, a RE-Ba-Cu-O bulk body (RE is a high-temperature superconductor). , Y, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu represents one or more elements selected from the group consisting of, and a magnetic field is captured as a magnet. Development of superconducting bulk magnets to function is also progressing. Superconducting bulk magnets are much more compact than superconducting coil magnets and are suitable for applications that generate a large magnetic field in a relatively small space. Further, since it is essentially operated in the permanent current mode, there is an advantage that once it is excited, a magnetic field is continuously generated as long as it is cooled.

  In order to obtain a high-performance magnet, the trapping magnetic field may be increased, but the magnitude of the trapping magnetic field is proportional to the size of the current loop as well as the critical current. Therefore, to improve the performance of the superconducting bulk magnet, it is necessary to improve the critical current by controlling the structure and increase the size of the sample. However, it is not sufficient to simply increase the size of the sample, and it is necessary to realize an increase in size with a structure having no weak bond such as a large-angle grain boundary or a crack.

For this reason, by growing a crystal having a c-axis orientation over the entire sample by a seed crystal melting method, the size is increased with a structure having no large-angle grain boundaries or cracks (see Non-Patent Document 1). ). In the seed crystal melting method, for example, when it is desired to obtain a RE-Ba-Cu-O-based bulk body, a seed crystal is placed on the upper surface of the RE-Ba-Cu-O-based cylindrical pellet to grow a crystal. As the seed crystal, a crystal having a high melting point such as NdBa ₂ Cu ₃ O ₇ is used. When a seed crystal is used, a crystal that inherits the orientation of the seed crystal grows, so that the orientation can be controlled and a c-axis oriented crystal can be obtained.

Superconducting Web21, 2002 (8), 16-18

However, a superconducting bulk magnet with significantly improved properties as a magnet can be obtained even if a superconducting bulk body obtained by the seed crystal melting method in this way captures a strong magnetic field to produce a superconducting magnet. I couldn't. In addition, the superconducting bulk magnet has characteristic unevenness in the surface, and a uniform and reliable superconducting bulk magnet could not be obtained.
Therefore, the present inventors have solved such a problem of the prior art, provided a superconducting bulk body having a high magnetic field capturing ability, and provided a superconducting bulk magnet having a high magnetic field strength using the superconducting bulk body. The study was advanced as a purpose. In addition, the inventors of the present invention have also studied for the purpose of providing a uniform and reliable superconducting bulk magnet by suppressing characteristic unevenness in the surface of the superconducting bulk magnet. Furthermore, the present inventors have also studied for the purpose of providing a simple method for producing a superconducting bulk body used when producing such a superconducting bulk magnet.

  As a result of diligent studies to solve the above-described problems of the prior art, the present inventors have removed the upper and lower portions of the cylindrical synthetic crystal obtained by the seed crystal melting method to remove the central portion of the cylindrical synthetic crystal. It was found that a superconducting bulk body having a high magnetic field capturing ability can be produced by taking out and stacking in the direction of the central axis. It was also found that a superconducting bulk magnet having a high magnetic field strength can be produced by using the superconducting bulk material thus produced. Based on these findings, the following present invention has been provided as means for solving the problems of the prior art.

[1] A superconducting bulk body including a RE-Ba-Cu-O-based columnar crystal piece,
RE represents one or more elements selected from the group consisting of Y, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu;
A superconducting bulk body in which the upper and lower surfaces of the RE-Ba-Cu-O-based columnar crystal piece satisfy the following formulas (1) and (2).
Formula (1): 0.93 ≦ X ≦ 1.07
(In the above formula, X represents the X value in the superconducting phase composition formula RE _x Ba ₂ Cu ₃ O _y (y is 6.8 to 7.0).)
Formula (2): θc ≦ 6 °
(In the above equation, θc represents the angle formed by the c-axis closest to the c-axis among the main axes of the crystal observed on the upper surface or the lower surface, and when the main axis of the crystal is not observed in the region, the equation (2) Is not satisfied.)
[2] The RE-Ba-Cu-O-based columnar crystal piece is a columnar synthetic crystal central portion obtained by removing the upper and lower portions of the columnar synthetic crystal synthesized by the seed crystal melting method, or the columnar shape. The superconducting bulk material according to [1], which is a cylindrical synthetic crystal cut piece obtained by cutting the central portion of the synthetic crystal in a direction perpendicular to the central axis.
[3] A superconducting bulk body including a stack in which at least two or more RE-Ba-Cu-O columnar crystal pieces according to [1] or [2] are stacked in the central axis direction.
[4] The superposition according to [3], wherein the stack is stacked such that the RE-Ba-Cu-O-based columnar crystal pieces are displaced in a crystal orientation in a plane perpendicular to a central axis. Conductive bulk body.
[5] The superconducting bulk body according to any one of [1] to [4], wherein a hole is formed in the columnar crystal piece, and a heat conductive member is inserted into the hole.
[6] The superconducting bulk material according to [5], wherein a resin or a metal is impregnated between the inner wall of the hole and the outer surface of the thermally conductive member.
[7] The superconducting bulk body according to any one of [1] to [6], wherein an outer surface of the columnar crystal piece is impregnated with a resin or a metal.
[8] The superconducting bulk body according to any one of [1] to [7], further including a fastener that compresses the cylindrical crystal piece from the outside of the cylindrical crystal piece.
[9] The superconducting bulk body according to [8], wherein the fastener is made of a shape memory alloy.
[10] A superconducting bulk magnet using the superconducting bulk body according to any one of [1] to [9].

[11] A method for producing a superconducting bulk material including a columnar crystal piece, comprising the following step 1.
<Step 1>
The upper and lower parts of the cylindrical synthetic crystal synthesized by the seed crystal melting method are removed to obtain the central part of the cylindrical synthetic crystal, or the central part of the cylindrical synthetic crystal is cut in a direction perpendicular to the central axis to obtain a circle. A step of obtaining a columnar synthetic crystal cut piece.
[12] The method for producing a superconducting bulk material according to [11], which includes the following step 2 after the step 1.
<Process 2>
A step of stacking any two or more of the columnar synthetic crystal central portion and the columnar synthetic crystal cut pieces obtained in step 1 in a central axis direction to form a stack.
[13] The columnar synthetic crystal is a RE-Ba-Cu-O-based columnar synthetic crystal, and the columnar crystal piece is a RE-Ba-Cu-O-based columnar crystal piece, [11] or [ 12] (the RE is one or two selected from the group consisting of Y, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu) Represents more than one kind of element).
[14] The superconducting bulk material according to any one of [11] to [13], wherein in the step 1, the thickness of the upper part and the lower part removed from the cylindrical synthetic crystal is 0.1 mm or more, respectively. Manufacturing method.
[15] In the step 1, the cylindrical synthetic crystal is obtained by growing a crystal by placing a seed crystal on the upper surface of a cylindrical pellet, and removing the upper part of the cylindrical synthetic crystal after removing the upper part thereof. The method for producing a superconducting bulk body according to any one of [11] to [14], wherein the composition on the upper surface of the center of the crystal satisfies the following formula (1).
Formula (1): 0.93 <= X <= 1.07%
(In the above formula, X represents the X value in the superconducting phase composition formula RE _x Ba ₂ Cu ₃ O _y (y is 6.8 to 7.0).)
[16] In the step 1, the cylindrical synthetic crystal is obtained by growing a crystal by placing a seed crystal on the upper surface of a cylindrical pellet, and removing the upper part of the cylindrical synthetic crystal after removing the upper part thereof. The method for producing a superconducting bulk material according to any one of [13] to [15], wherein the element content in the upper surface of the crystal central part satisfies the following formula (3).
Formula (3): | M _RES (center upper surface) −M _RES (pellet) | ≦ 7 atomic%
(In the above formula, M _RES (center top surface) is the content of RE ^S _i element in the top surface of the cylindrical synthetic crystal center (the number of RE ^S _i elements relative to the total number of RE elements). M _RES (pellet) is the content of RE ^S _i element in the cylindrical pellet (the number of atoms of RE ^S _i element relative to the number of atoms of all RE elements, and the unit is atomic%) The RE ^S element is one or two selected from the group consisting of Y, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu contained in the seed crystal. It represents or more elements, i is representative of the type of RE ^S element.)
[17] In the step 1, the columnar synthetic crystal is obtained by growing a crystal by placing a seed crystal on the upper surface of a columnar pellet, and removing the lower portion of the columnar synthetic crystal from the surface after the lower portion is removed. The method for producing a superconducting bulk body according to any one of [10] to [16], wherein a region having a thickness of 1 mm satisfies the following formula (2).
Formula (2): θc ≦ 6 °
(In the above equation, θc represents the angle formed by the c-axis and the principal axis of the crystal that is observed on the upper surface or the lower surface, and when the main axis of the crystal is not observed in the region, the equation ( 2) shall not be satisfied.)
[18] The method for producing a superconducting bulk body according to any one of [10] to [17], wherein the thickness of the upper portion removed from the cylindrical synthetic crystal is 1 to 5 mm.
[19] The method for producing a superconducting bulk body according to any one of [10] to [18], wherein a thickness of a lower portion to be removed from the cylindrical synthetic crystal is 1 to 15 mm.
[20] A superconducting bulk body produced by the production method according to any one of [10] to [19].

  The superconducting bulk material of the present invention has an advantageous effect that it has a high magnetic field capturing ability and is useful for producing a superconducting bulk magnet. In addition, the superconducting bulk magnet of the present invention has an advantageous effect that the magnetic field strength is high, and also has a feature that it is possible to obtain a uniform and reliable magnet by suppressing characteristic unevenness in the magnet surface. . Furthermore, according to the manufacturing method of the present invention, there is an advantageous effect that the above superconducting bulk body can be easily manufactured.

It is a perspective view which shows preparation and cutting | disconnection of a column-shaped synthetic crystal center part. It is a perspective view which shows the direction which stacks a columnar crystal piece. It is a perspective view which shows how to stack a cylindrical crystal piece. It is a perspective view which shows the reinforcement aspect of the stacked body by a heat conductive member. It is a perspective view which shows another reinforcement aspect of the stacked body by a heat conductive member. It is a perspective view which shows another reinforcement aspect of the stack by a heat conductive member. It is a perspective view which shows another reinforcement aspect of the stack by a heat conductive member. It is a perspective view which shows the reinforcement aspect of the stacked body by a fastener. It is a perspective view which shows another reinforcement aspect of the stacked body by a fastener. It is a perspective view which shows another reinforcement aspect of the stacked body by a fastener. It is a perspective view which shows another reinforcement aspect of the stacked body by a fastener. It is sectional drawing which shows another reinforcement aspect of the stacked body by a fastener. It is a graph which shows the relationship between x value and critical current density Jc. It is a graph which shows the relationship between x value and critical current density Jc. It is a graph which shows the relationship between the angle (theta) which c-axis makes, and critical current density Jc.

  Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments and specific examples of the present invention, but the present invention is not limited to such embodiments and specific examples. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

[Superconducting bulk material]
(Basic structure)
The superconducting bulk body of the present invention is a superconducting bulk body including RE-Ba-Cu-O-based columnar crystal pieces.
The RE-Ba-Cu-O-based columnar crystal piece is composed of at least each element of RE, Ba, Cu, and O. Here, RE represents one or more elements selected from the group consisting of Y, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu, and has superconductivity. Selected as shown. When it is one kind of element, for example, Y, Gd, Dy, and Ho can be given as preferable examples. When RE is two or more kinds of elements, for example, a combination of Nd, Eu, and Gd can be cited as a preferred example, and a combination of Nd, Eu, and Gd, and a combination of Sm, Eu, and Gd are cited as more preferable examples. Can do. A typical columnar crystal piece is formed inside the superconducting phase of REBa ₂ Cu ₃ O _y (y is usually 6.8 to 7.0, for example, 6.95), and the non-reactive layer of RE ₂ BaCuO ₅ . It has a composite structure in which the superconducting phase is finely dispersed. The fine RE ₂ BaCuO ₅ phase acts as a pinning center, increasing the critical current density of the superconducting bulk material. The columnar crystal piece may contain elements other than RE, Ba, Cu, and O to the extent that they do not contradict the purpose of the present invention, but it is preferable that such elements are not contained. The elemental compositions of the stacked cylindrical crystal pieces may be the same or different from each other, but are preferably the same.

(Explanation of Formula (1))
Each RE-Ba-Cu-O-based columnar crystal piece constituting the superconducting bulk material of the present invention satisfies the relationship of the following formula (1) on the upper surface and the lower surface.
Formula (1): 0.93 ≦ X ≦ 1.07
In the above formula, X represents the X value in the superconducting phase composition formula RE _x Ba ₂ Cu ₃ O _y (y is 6.8 to 7.0).

It is more preferable that the upper surface and the lower surface satisfy the following formula (1-1),
Formula (1-1): 0.95 ≦ X ≦ 1.05
More preferably, the following formula (1-2) is satisfied,
Formula (1-2): 0.98 ≦ X ≦ 1.02
It is even more preferable that the following formula (1-3) is satisfied.
Formula (1-3): 0.99 ≦ X ≦ 1.01
By producing a superconducting bulk body using cylindrical crystal pieces that satisfy the formula (1), a superconducting bulk body having a high magnetic field capturing ability can be obtained, and a superconducting bulk magnet having a high magnetic field strength can be produced. be able to.

  The X value in Formula (1) can be measured by elemental analysis using an electron beam probe microanalyzer or the like.

(Explanation of Formula (2))
Each RE-Ba-Cu-O-based columnar crystal piece constituting the superconducting bulk body of the present invention satisfies the following formula (2) on its upper and lower surfaces.
Formula (2): θc ≦ 6 °
In the above equation, θc represents an angle formed by the c-axis closest to the c-axis among the main axes of the crystal observed on the upper surface or the lower surface, and when the main axis of the crystal is not observed in the region, the equation (2) is expressed. It shall not be satisfied. θc is more preferably 5 ° or less, further preferably 2 ° or less, and still more preferably 1 ° or less. By producing a superconducting bulk body using columnar crystal pieces satisfying the formula (2), a superconducting bulk body having a high magnetic field capturing ability can be obtained, and a superconducting bulk magnet having a high magnetic field strength can be produced. be able to.

[Manufacturing method of superconducting bulk material]
(Basic process)
Next, a method for producing the superconducting bulk material of the present invention will be described. The manufacturing method of the present invention described below is a preferable manufacturing method for manufacturing the superconducting bulk body of the present invention, and the superconducting bulk body of the present invention is limited to that manufactured by the manufacturing method of the present invention. It is not something. Moreover, the manufacturing method of this invention can be applied also to manufacture of superconducting bulk bodies other than the RE-Ba-Cu-O type | system | group superconducting bulk body of this invention.

The production method of the present invention includes at least the following two steps.
<Step 1>
The upper and lower parts of the cylindrical synthetic crystal synthesized by the seed crystal melting method are removed to obtain the central part of the cylindrical synthetic crystal, or the central part of the cylindrical synthetic crystal is cut in a direction perpendicular to the central axis to obtain a circle. A step of obtaining a columnar synthetic crystal cut piece.
<Process 2>
A step of stacking any two or more of the columnar synthetic crystal central portion and the columnar synthetic crystal cut pieces obtained in step 1 in a central axis direction to form a stack.

  In step 1, only a central part of the columnar synthetic crystal may be obtained, and in step 2, they may be stacked in the central axis direction to form a laminate. Further, in step 1, only a plurality of cylindrical synthetic crystal cut pieces may be obtained, and in step 2, they may be stacked in the central axis direction to form a laminate. Further, in step 1, one or more columnar synthetic crystal central portions and one or more columnar synthetic crystal cut pieces may be obtained, and in step 2, they may be stacked in the central axis direction to form a laminate. The production method of the present invention includes all these aspects.

(Seed crystal melting method)
The seed crystal melting method is usually carried out by placing a cylindrical pellet on a support substrate so that the central axis is in the vertical direction, and placing the seed crystal in the center of the upper surface of the cylindrical pellet. The supporting substrate has a size capable of stably installing cylindrical pellets, and an Al ₂ O ₃ plate or the like can be used. A powder having an appropriate elemental composition can be present between the support substrate and the columnar pellet according to the type of crystal to be grown. For example, when YBa ₂ Cu ₃ O _{7 is} to be crystal-grown, Y ₂ O ₃ powder or BaCuO ₂ powder may be present.

(Cylindrical pellet)
The cylindrical pellet used in the present invention is preferably a RE ^P —Ba—Cu—O-based cylindrical pellet composed of each element of RE ^P , Ba, Cu, and O. RE ^P here represents Y, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and one or more kinds of element selected from the group consisting of Lu. Elemental composition of RE ^P selected here, it is preferable to match the elemental composition of the PE of RE-Ba-Cu-O-based columnar crystal plates trying to obtain in the present invention.

  The cylindrical pellet used in the present invention needs to have a size that allows a seed crystal to be directly placed on the upper surface thereof. For this reason, it is preferable that the diameter of an upper surface and a lower surface is 5 mm or more, and it is more preferable that it is 10 mm or more. The height is preferably 5 mm or more, more preferably 10 mm or more, more preferably 25 mm or less, and even more preferably 20 mm or less.

  The columnar pellet can be manufactured by, for example, pressing and molding a raw material powder. At this time, pressure molding may be performed after mixing plural kinds of powders having different elemental compositions. Further, Pt or the like may be added and mixed before pressure molding. When these are added, the addition amount is preferably 0.1% by weight or less, and more preferably 1.5% by weight or less. The pressurization can be performed using, for example, a hydrostatic pressure. It is preferable that the molded body after the pressure molding is used for the seed crystal melting method after preliminary sintering.

(Seed crystal)
The seed crystal used for the production of the superconducting bulk material of the present invention is preferably a RE ^S —Ba—Cu—O based seed crystal composed of each element of RE ^S , Ba, Cu, and O. Here, RE ^S is one or more elements selected from the group consisting of Y, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu. Nd, Sm, and Gd are preferable. The seed crystal preferably has the same crystal structure as the crystal to be grown and has a high melting point. For example, when you are trying to crystal growth the YBa ₂ Cu ₃ O _7, it is preferable to use the NdBa ₂ Cu ₃ O ₇ and SmBa ₂ Cu ₃ O ₇ as a seed crystal.

  The size of the seed crystal used for manufacturing the superconducting bulk material of the present invention may be any size that can be directly installed on the upper surface of the cylindrical pellet. The size of the lower surface of the seed crystal contacting the upper surface of the pellet is preferably 1 mm square or more, more preferably 2 mm square or more, and preferably 10 mm square or less, preferably 5 mm square or less. Is more preferable. The thickness is not particularly limited, but is usually selected within a range of 2 to 5 mm.

(Crystal growth)
Crystal growth is performed by placing a cylindrical pellet on a support substrate so that the central axis is in the vertical direction, placing a seed crystal in the center of the upper surface of the cylindrical pellet, and heating it to a high temperature. By heating to a high temperature, a crystal whose orientation is controlled so as to inherit the crystal orientation of the seed crystal grows around the contact surface with the seed crystal. The temperature at the time of crystal growth can be set to 900 to 1100 ° C., for example, and is preferably set to 950 to 1050 ° C. After crystal growth, oxygen annealing treatment or the like can be performed as necessary. The growth of this crystal can usually be performed in the atmosphere.
About the material and process used for the above seed crystal melting method, you may substitute to a well-known material and process. Moreover, you may add a well-known material and process further as needed.

(Removal of upper and lower parts)
As shown in FIG. 1, the cylindrical synthetic crystal 11 obtained by the seed crystal melting method then removes the upper portion 12 and the lower portion 13 to form a cylindrical synthetic crystal central portion 14. The removal of the upper part and the lower part may be performed at the same time, or one of them may be sequentially performed first. In the present invention, the upper portion and the lower portion are removed so that a cylindrical synthetic crystal central portion is obtained after the removal. Usually, the upper part and the lower part of the cylindrical synthetic crystal are each removed with an equal thickness. The thickness removed at the top and bottom may be the same or different. Usually, it is often preferable to remove the lower part slightly thicker, but the reverse may be possible.

  The specific method of removal is not particularly limited. It may be removed by slicing or electric discharge machining using a slice cutter, diamond cutter, or the like, or may be removed by using a combination of an abrasive or a polishing sheet.

  The upper part of the cylindrical synthetic crystal is preferably removed so that the composition at the upper surface of the central part of the cylindrical synthetic crystal obtained after the removal satisfies the above formula (1). At this time, it is preferable to measure the X value of the upper surface of the cylindrical synthetic crystal and determine the removal thickness of the upper portion of the cylindrical synthetic crystal so as to satisfy the formula (1) based on the measurement result. For example, after crystal growth by the seed crystal melting method, the seed crystal is removed from the upper surface of the cylindrical synthetic crystal, the upper surface is lightly polished or washed, and then the X value is measured. Based on the measurement result The top removal thickness can be determined and removed. Alternatively, removal and measurement may be repeated until expression (1) is satisfied. Usually, by unifying the material, the manufacturing apparatus, and the manufacturing conditions to some extent, the thickness to be removed at the top can be determined to some extent accurately by one measurement. Such measurement and removal can also be automated by computer control. Also on the lower surface, the removal thickness can be determined and removed in the same manner as the upper surface. Usually, by removing the lower surface so as to satisfy Equation (2) described later, a lower surface that also satisfies Equation (1) is obtained.

When removing the upper part from a viewpoint different from the formula (1), the upper part is removed so that the element content in the upper surface of the central portion of the cylindrical synthetic crystal obtained after the removal satisfies the following formula (3). It is preferable.
Formula (3): | M _RES (center upper surface) −M _RES (pellet) | ≦ 7 atomic%
In the above formula, M _RES (center upper surface) is the content of RE ^S _i element on the upper surface of the central portion of the cylindrical synthetic crystal (the number of atoms of RE ^S _i element relative to the number of atoms of all RE elements, and the unit is atomic% M _RES (pellet) is the content of the RE ^S _i element in the cylindrical pellet (the number of atoms of the RE ^S _i element relative to the total number of atoms of the RE element, and the unit is atomic%). I represents the type of the RE ^S element.

Formula (3) indicates that the RE element composition of the upper surface of the central portion of the cylindrical synthetic crystal and the cylindrical pellet are substantially the same. The value of | M _RES (center upper surface) −M _RES (pellet) | is more preferably 5 atomic% or less, further preferably 2 atomic% or less, and even more preferably 1 atomic% or less. preferable. If a superconducting bulk body is produced using a columnar crystal piece satisfying the formula (3), a superconducting bulk body having a high magnetic field capturing ability can be obtained, and further a superconducting bulk magnet having a high magnetic field strength can be produced. Can do. The value of M _RES (pellet) can also be obtained by calculating from the elemental composition of the powder blended when producing the pellet.

Equation (3) even if the removal of the upper so as to satisfy the measures the RE ^S elemental content of the upper surface of the columnar synthetic crystalline, columnar synthetic crystalline to satisfy equation (3) based on the measurement result It is preferred to determine the removal thickness of the top of the. For example, to remove the seed crystal from the upper surface of the columnar synthetic crystals after crystal growth by the seed crystal melting method, measures the RE ^S element concentration after washing or polishing lightly top, based on the measurement result The upper removal thickness can be determined and removed. Alternatively, removal and measurement may be repeated until expression (3) is satisfied. Usually, the thickness to be removed in one measurement can be determined to some extent accurately by matching the material, the manufacturing apparatus, and the manufacturing conditions to some extent. Such measurement and removal can also be automated by computer control. Also on the lower surface, the removal thickness can be determined and removed in the same manner as the upper surface. Usually, the lower surface satisfying the formula (3) is obtained by removing the lower surface so as to satisfy the later-described formula (2).

The lower part of the cylindrical synthetic crystal is preferably removed so that the central part of the cylindrical synthetic crystal obtained after the removal satisfies the above formula (2).
In the present invention, it is preferable to observe the crystal axis of the lower surface of the cylindrical synthetic crystal and determine the removal thickness of the lower portion of the cylindrical synthetic crystal so as to satisfy the formula (2) based on the observation result. For example, after crystal growth by the seed crystal melting method, the bottom surface of the bulk crystal is lightly polished and washed, then the crystal axis is observed, and the removal thickness at the bottom is determined based on the observation results. can do. Alternatively, removal and measurement may be repeated until expression (2) is satisfied. Usually, the thickness to be removed in one measurement can be determined to some extent accurately by matching the material, the manufacturing apparatus, and the manufacturing conditions to some extent. Such measurement and removal can also be automated by computer control. Also on the upper surface, the removal thickness can be determined and removed similarly to the lower surface. Usually, by removing the upper surface so as to satisfy the above equation (1), an upper surface that also satisfies the equation (2) can be obtained.

The removal thickness of the upper part of the bulk crystal is usually 0.1 mm or more, preferably 0.2 mm or more, and more preferably 0.5 mm or more. Further, the removal thickness of the upper part of the bulk crystal is usually 10 mm or less, and preferably 5 mm or less.
The removal thickness of the bulk crystal lower part is usually 1 mm or more, preferably 2 mm or more, and more preferably 5 mm or more. Moreover, the removal thickness of the bulk crystal lower part is usually 20 mm or less, preferably 15 mm or less, and more preferably 10 mm or less.

(Cut)
As shown in FIG. 1, the cylindrical synthetic crystal central portion 14 obtained by removing the upper and lower portions is further cut in a direction perpendicular to the central axis to cut cylindrical synthetic crystal pieces 15 and 16. It is good. This step is performed only when it is desired to use a cylindrical synthetic crystal cut piece when a subsequent stack is produced. The cutting can be performed by means usually used when cutting a cylindrical synthetic crystal obtained by a seed crystal melting method. For example, it can be cut by a diamond cutter or electric discharge machining. The thickness of the cylindrical synthetic crystal cut piece obtained after cutting is not particularly limited, but it is preferable that the thickness be within the range of the preferable thickness of the cylindrical crystal piece used for stacking as described later.

(Production of stacks)
The stack is produced by stacking two or more columnar crystal pieces selected from the group consisting of a plurality of columnar synthetic crystal central portions and a plurality of columnar synthetic crystal cut pieces in the central axis direction. The central axis here means the central axis 21 of the cylindrical crystal piece shown in FIG. 2, and stacking in the direction of the central axis means that the upper surface of one cylindrical crystal piece 22 is the lower surface of another cylindrical crystal piece 23. It means to overlap so that. When stacking, as shown in FIG. 2, it is preferable to stack so that the central axis of each columnar crystal piece is located on the same line. The number of columnar crystal pieces to be stacked is not particularly limited as long as it is two or more. Moreover, the shape of each columnar crystal piece to be stacked may be the same or different. Preferred is a case where the diameters of the stacked columnar crystal pieces are all the same, and a superconducting bulk body that is columnar and easy to handle can be obtained.
The thickness of the center of the cylindrical synthetic crystal or the cylindrical synthetic crystal cut pieces (hereinafter collectively referred to as cylindrical crystal pieces) to be stacked is preferably 1 mm or more, more preferably 2 mm or more, and more preferably 5 mm or more. More preferably. Further, the thickness of the stacked columnar crystal pieces is preferably 20 mm or less, more preferably 15 mm or less, and further preferably 10 mm or less. The thickness of each columnar crystal piece to be stacked may be the same or different.

When producing a stack, it is preferable to stack so that crystal orientations in a plane perpendicular to the central axis of the columnar crystal pieces are shifted from each other. Specifically, it is preferable that at least two of the columnar crystal pieces constituting the stack are stacked such that crystal orientations in a plane perpendicular to the central axis are shifted from each other, and as many columnar crystals as possible constitute the stack. It is more preferable to stack the pieces so that the crystal orientations of the pieces are shifted from each other. Whether or not the crystal orientation is deviated can be easily determined by observing the sector boundary on the upper surface of the columnar crystal piece. That is, a sector boundary corresponding to the shape of the seed crystal is observed in the columnar crystal piece derived from the crystal synthesized by the seed crystal melting method. The sector boundary here includes a sub boundary associated with crystal growth called a facet line. For example, when synthesized using a NdBa ₂ Cu ₃ O _y single crystal as a seed crystal, the sector boundary 31 is observed so that the upper surface of the columnar crystal piece is divided into four equal parts as shown in FIG. The sector boundaries are preferably stacked so that they do not overlap when viewed from the central axis direction of the cylindrical stack. For that purpose, a method of stacking while rotating around the central axis of the columnar crystal piece can be employed. For example, when stacking n columnar crystal pieces of the same type, if they are stacked while being rotated by (90 ° / n) °, the sector boundary will not overlap, and the sector boundary will appear when viewed from the central axis direction. Dally will be evenly distributed in the circumferential direction. For example, when stacking three cylindrical crystal pieces, it is preferable to stack while rotating by 30 °, and when stacking four cylindrical crystal pieces, it is preferable to stack while rotating by 22.5 °. preferable. At this time, n columnar crystal pieces may be stacked so as to be clockwise or counterclockwise in order, or may be stacked randomly. FIG. 3 illustrates an example in which three columnar crystal pieces 32, 33, and 34 are stacked while being rotated counterclockwise by 30 degrees. In this way, when viewed from the central axis direction, sector boundaries are not unevenly distributed and evenly distributed in the circumferential direction. Thus, a uniform and reliable magnet can be provided.

  When trapping a magnetic field in a superconducting bulk body made of stacks as described above, it is necessary to cool with liquid nitrogen or the like, and when a magnetic field is applied in a superconducting state, a strong Lorentz force is generated in the outer circumferential direction. To work. Therefore, the stack constituting the superconducting bulk body needs to be able to withstand temperature change, Lorentz force and the like. Therefore, in the present invention, it is preferable to perform reinforcement as described below.

(Reinforcement with heat conductive material)
In the present invention, the hole can be reinforced by forming a hole in the columnar crystal piece and inserting and fixing the heat conductive member into the hole.
The critical current density of the RE-Ba-Cu-O-based superconducting bulk material is dramatically improved as the temperature decreases. For this reason, operating at lower temperatures is advantageous for magnet applications. However, since the specific heat decreases as the temperature decreases, the thermal stability as superconductivity decreases, and the temperature of the superconductor tends to increase with a slight heat generation. For this reason, a quench phenomenon in which superconductivity is suddenly broken by a small external disturbance may occur. In addition, in the magnetization process, the magnetic flux moves as the magnetic flux is rearranged in the superconductor, and the quenching phenomenon may occur due to the rapid increase in temperature caused by the generated heat. In order to deal with the problem due to such a rapid temperature fluctuation, a heat conductive member is inserted into the hole formed in the cylindrical crystal piece, and the heat generated in the cylindrical crystal piece is passed through the heat conductive member. The heat-resistant variability of the columnar crystal piece is reinforced by releasing it outside the columnar crystal piece.

  The heat conductive member is a material having higher heat conductivity than the RE-Ba-Cu-O-based crystal constituting the columnar crystal piece, and the columnar crystal piece continuously without interruption in the columnar crystal piece. It is preferable to have a structure that communicates with the outside. The heat conductive member is preferably made of metal. Examples of the metal include aluminum, copper, silver, and gold, and aluminum or copper is preferably used. If a material having a higher strength than the RE-Ba-Cu-O-based crystal constituting the columnar crystal piece is selected, the structure of the columnar crystal piece is reinforced to suppress the deviation between the columnar crystal pieces. It is also preferable because it can be used.

  It is preferable that the hole formed in the columnar crystal piece corresponds to the shape of the heat conductive member. For example, as shown in FIG. 4, the aspect which inserted the heat conductive member 43 in the through-hole 42 provided in parallel with the central axis of the column-shaped columnar crystal piece 41 can be mentioned. Moreover, as shown in FIG. 5, the aspect which inserted the heat conductive member 53 in the through-hole 52 provided so that it might extend in the diagonal direction with respect to the central axis of the column-shaped columnar crystal piece 51 may be mentioned. it can. In the embodiment shown in FIGS. 4 and 5, an example is given in which the number of through holes and the number of thermally conductive members is two, but the number may be three or more. In consideration of the fact that the plane perpendicular to the central axis of the columnar crystal piece is divided into four by the sector boundary, it is also preferable to employ a number that is a multiple of four, such as four or eight. As another embodiment, as shown in FIG. 6, there may be mentioned an embodiment in which a heat conductive member 63 is inserted into a hole 62 provided so as to extend spirally around the central axis of the columnar crystal piece 61. it can. At this time, it is preferable not to increase the number of spiral stages because the heat conduction path for releasing the local heat generated in the bulk body to the outside is shortened. In addition, it is preferable that the number of steps is not so large from the viewpoint of suppressing the strength reduction of the bulk body. Specifically, the number of stages is preferably 3 or less, more preferably 2 or less. In any of the embodiments such as FIGS. 4 to 6, the plurality of holes and the heat conductive member are preferably provided at positions symmetrical with respect to the central axis of the cylindrical columnar crystal piece.

  When the hole formed in the columnar crystal piece is a through hole, it is preferable that the hole be formed as a through hole leading from the upper surface to the lower surface of the columnar crystal piece as shown in FIGS. The hole formed in the columnar crystal piece is not necessarily a through hole, and may be, for example, a hole communicating only with the upper surface or a hole communicating only with the lower surface. FIG. 7 shows a mode in which a heat conductive member 73 is inserted into a hole 72 provided so as to communicate only with the lower surface of the columnar crystal piece 71. Here, the heat conductive member 73 extends to the inside of the heat radiating plate 74 that is installed on the lower surface of the columnar crystal piece 71 and has high heat conductivity, so that the heat is more easily released. The heat sink can be replaced with a cooling mechanism having a function of actively lowering the temperature. Thus, the structure which the heat | fever generate | occur | produced in a cylindrical crystal piece conducts to a fixed direction can also be mentioned as a preferable aspect.

The inner diameter of the hole formed in the columnar crystal piece and the cross-sectional diameter of the heat conductive member are preferably 0.01 mm or more, more preferably 0.5 mm or more, and 5 mm or less. Preferably, it is more preferably 2 mm or less. The hole can be formed using a known means such as a drill.
When inserting a thermally conductive member into a hole provided in a columnar crystal piece, a known technique described in Japanese Patent No. 3858221 is appropriately selected and applied to the present invention with necessary modifications. be able to.

(Reinforcement by impregnation treatment)
As another reinforcing method for the columnar crystal piece, a method of impregnating with resin or metal can also be mentioned.
Cracks and fine scratches may be present on the outer surface of the RE-Ba-Cu-O-based columnar crystal piece constituting the columnar crystal piece. If such cracks and scratches are left untreated, cracks may expand due to external forces such as thermal expansion and Lorentz force during cooling, and the functions and mechanical properties of the superconducting bulk material and superconducting bulk magnet may be impaired. In addition, RE-Ba-Cu-O-based crystals have a property of being easily deteriorated by reacting with moisture in the air. Therefore, by impregnating the outer surface of the columnar crystal piece with resin or metal, deterioration of mechanical properties can be prevented and deterioration due to reaction with moisture can be suppressed. When a heat conductive member is inserted into the hole formed in the columnar crystal piece, it is extremely preferable to impregnate a resin or metal between the inner wall of the hole and the outer surface of the heat conductive member. By performing such an impregnation treatment, local heat generated in the columnar crystal piece can be quickly conducted to the heat conductive member through the impregnation portion.

  An example of the resin used for the impregnation treatment is a thermosetting resin. For example, an epoxy resin, a phenol resin, a polyimide resin, a polyimide amide resin, a polyethersulfone resin, and the like that are thermally cured by heating to a relatively low temperature (for example, 50 ° C. or more) can be given. These resins can be easily impregnated by heating and applying them to columnar crystal pieces. Two or more kinds of resins may be used, and the second resin may be applied so as to cover the first resin after impregnation. Examples of the first resin include the thermosetting resins exemplified above, and examples of the second resin include a mixture of these thermosetting resins and fluororesins.

  The metal used for the impregnation treatment is a single metal or an alloy. When the RE-Ba-Cu-O-based columnar crystal piece constituting the columnar crystal piece is heated above a certain temperature, the bonded oxygen is dissipated and does not exhibit superconducting properties. Adopt alloy. For example, Bi-Pb-Sn-Cd-In alloy, Bi-Pb-Sn-In alloy, Bi-Pb-Sn-Cd alloy, Bi-Pb-Sn-Sb alloy, Bi-Sn-In alloy, Bi-Pb -Cd alloy, Bi-Pb-Sn alloy, Bi-Sn-Cd alloy, Bi-Pb alloy, Bi-Sn alloy, Bi, In, Sn, etc. can be mentioned. The impregnation treatment can be performed by, for example, a method of bringing a columnar crystal piece held in a reduced-pressure atmosphere into contact with a molten metal simple substance or alloy, a method of impregnation while applying pressure, or the like.

  For reinforcement by impregnation treatment, known techniques described in Japanese Patent Application Laid-Open Nos. 2008-177245, 2006-321668, and 3090658 are appropriately selected, and necessary modifications are made to the present invention. Can be applied.

(Reinforcement with fasteners)
As another reinforcing method for the columnar crystal piece, a method of attaching a fastener for compressing the columnar crystal piece from the outside to the columnar crystal piece can be mentioned.
The fastener applies a compressive stress to protect the columnar crystal piece against the Lorentz force acting in the outer circumferential direction of the columnar crystal piece, or relative to the plurality of columnar crystal pieces constituting the columnar crystal piece. It is preferable to apply a compressive stress so that the positional relationship does not change. Specifically, compressive stress is applied from the peripheral surface of the cylindrical crystal piece toward the central axis of the cylindrical crystal piece, or a plurality of cylindrical crystals are formed from the upper and lower surfaces of the cylindrical crystal piece. It is preferable to apply a compressive stress so as to sandwich the piece. By using a fastener, a superconducting bulk body with a higher magnetic field capturing ability can be produced.

  As a preferable mode, for example, as shown in a perspective view in FIG. 8, a mode in which an encircling belt 82 for applying a compressive stress from the side peripheral surface of the cylindrical crystal piece 81 toward the central axis can be provided. In addition, as shown in a perspective view in FIG. 9, an embodiment in which a plurality of surrounding belts 92 and 93 that apply compressive stress from the side peripheral surface of the columnar crystal piece 91 toward the central axis can be cited. Furthermore, as shown in a perspective view in FIG. 10, an embodiment in which a plurality of surrounding wires 102 for applying compressive stress from the side peripheral surface of the columnar crystal piece 101 toward the central axis can be cited. Furthermore, as shown in a perspective view in FIG. 11, an embodiment in which one surrounding wire 112 that applies a compressive stress from the side peripheral surface of the columnar crystal piece 111 toward the central axis is installed in a spiral shape can be cited. Further, as shown in a cross-sectional view in FIG. 12, a part of the upper surface of the cylindrical crystal piece 121 is arranged on the upper side of the surrounding belt 122 for applying a compressive stress A from the side peripheral surface of the cylindrical crystal piece 121 to the central axis. An aspect in which the upper extension 123 and the lower extension 124 covering a part of the lower surface of the columnar crystal piece 121 from the peripheral portion are extended to apply the compressive stress B in the central axis direction can also be mentioned. .

  The fastener is particularly preferably made of a shape memory alloy. If the shape memory alloy used in the present invention is heat-treated for shape memory, the shape before deformation is irreversible by heating above a specific temperature even if it is deformed to be installed on a cylindrical crystal piece. This alloy has the property of recovering automatically. If a go-belt or go-go wire made of a shape memory alloy is placed on the columnar crystal piece and then heated to a specific temperature or higher, the shape before deformation can be restored and a compressive stress can be applied to the columnar crystal piece. In the present invention, for example, Ag-Cd alloy, Au-Cd alloy, Cu-Al-Ni alloy, Cu-Sn alloy, Cu-Zn alloy, Fe-Pt alloy, Mn-Cu alloy, Fe-Mn-Si alloy, Pt alloy, Co—Ni—Al alloy, Co—Ni—Ga alloy, Ni—Fe—Ga alloy, Ti—Pd alloy, Ni—Ti alloy and the like can be used as preferable shape memory alloys. Among these, it is preferable to use an Fe-based shape memory alloy.

In the present invention, a metal ring or the like may be installed so as to be sandwiched between a clamp made of a shape memory alloy and a columnar crystal piece. If a metal ring is installed, the compressive stress from the fastener will be applied to the cylindrical crystal piece via the ring, so the compressive stress is applied more uniformly to the cylindrical crystal piece. be able to.
It is particularly preferable to apply such reinforcement by a fastener to a stacked body in which a plurality of columnar crystal pieces are stacked. If the stack is reinforced with fasteners, it is possible to effectively prevent the relative positional relationship between the cylindrical crystal pieces stacked in the axial direction from being shifted, thereby increasing the magnetic field capturing ability. Can be maintained. Such an effect can be further enhanced by combining with the above-described reinforcement by the heat conductive member and the reinforcement by the impregnation treatment.

[Superconducting bulk magnet]
By using the superconducting bulk material of the present invention, a superconducting bulk magnet having a high magnetic field strength can be produced. In order to capture the magnetic field in the superconducting bulk body, first, a magnetic field is applied to the superconducting bulk body and cooled with liquid nitrogen or the like. Thereafter, after the superconducting bulk body is sufficiently cooled, the external magnetic field is removed to capture the magnetic field in the superconducting bulk body. As for the details of the method for producing a superconducting bulk magnet from a superconducting bulk body, a known method can be appropriately selected and used. Specifically, examples described later can be referred to.

  The superconducting bulk magnet of the present invention is characterized by high magnetic field strength. For this reason, if the superconducting bulk magnet of the present invention is used, a strong magnetic field can be realized at a pinpoint, and magnetic field control with high directivity becomes possible. In addition, the superconducting bulk magnet of the present invention can be a uniform and highly reliable magnet while suppressing uneven magnetic characteristics in the magnet surface as described above. Moreover, it can be set as the magnet which was excellent in heat conductivity and was excellent also in the tolerance with respect to generation | occurrence | production of local heat. Furthermore, it is possible to obtain a strong magnet having high mechanical characteristics.

  Since it has such characteristics, the superconducting bulk magnet of the present invention can be effectively applied to various uses. For example, it can be applied to diagnostic / medical fields such as a magnetic induction type drug delivery system, NRI, and NMR, and can also be applied to the electronics field such as a magnetron sputtering apparatus. Furthermore, the present invention can be applied to the environmental field such as a magnetic separation device for the purpose of water purification, and can also be applied to the electric field such as a superconducting motor, a generator, and a flywheel system. In addition, application in a wide range of technical fields is expected.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

Example 1
YBa ₂ Cu ₃ O _y and Y ₂ BaCuO ₅ powders were prepared, weighed so that the weight ratio of these compounds was 10: 4, 0.5 wt% Pt was added, and then mixed well. Thereafter, it was molded into a pellet having a diameter of 45 mm and a thickness of 20 mm under a hydrostatic pressure of 2000 MPa. The pellet was heated in air at 900 ° C. for 1 hour and pre-sintered.
Next, on the Al ₂ O ₃ plate having a diameter of 50 mm and a thickness of 2 mm, a Y ₂ O ₃ powder formed into a pellet shape having a diameter of 45 mm and a thickness of 2 mm is first placed, and then the BaCuO ₂ powder is further reduced in diameter. What was molded into a pellet shape of 45 mm and a thickness of 10 mm was placed. On top of that, a calcined Y-Ba-Cu-O sintered body was installed.
Thereafter, a set of precursors on an Al ₂ O ₃ plate is installed in an electric furnace in the atmosphere, and NdBa ₂ Cu ₃ O _y is 2 mm square and 1 mm thick at the center of the Y-Ba-Cu-O sintered body. A single crystal was placed as a seed. Thereafter, the electric furnace was heated to 1100 ° C. at a rate of 50 ° C./h, held for 1 hour, cooled to 1050 ° C. for 1 hour, and then gradually cooled to 950 ° C. at a rate of 0.2 ° C./h. After furnace cooling was performed. The sample taken out from the furnace had a diameter of 30 mm and a height of 15 mm. Finally, an oxygen annealing treatment was performed at 400 ° C. for 100 hours in a 100% oxygen stream to obtain a cylindrical synthetic crystal. In this state, the superconducting critical temperature was measured, and a value of 90K was obtained. Furthermore, when the trapping magnetic field characteristics were measured with a Hall element under liquid nitrogen cooling (77 K) using a Fe—Nd—B magnet having a surface magnetic field of 0.4 T, a value of 0.21 T was obtained as the peak magnetic field.
Next, two Y-Ba-Cu-O columnar synthetic crystals are produced in the same manner, and are cooled with liquid nitrogen (77K) using an Fe-Nd-B magnet having a surface magnetic field of 0.4T. When the trapping magnetic field characteristics were measured with a Hall element, trapping magnetic fields of 0.20 T and 0.19 T were obtained, respectively. From these two cylindrical synthetic crystals, the upper part where the seeds were placed was separated into 2.5 mm and the lower part 5 mm, and two cylindrical synthetic crystal central parts with a thickness of 7.5 mm were prepared, and two cylindrical synthetic crystals were prepared. A superconducting bulk body made of a stack having a height of 15 mm was produced by applying glycerin between the central portions of the crystals and then superposing them. When the trapped magnetic field characteristics were measured with a Hall element under liquid nitrogen cooling (77 K) using a Fe—Nd—B magnet having a surface magnetic field of 0.4 T, a value of 0.32 T was obtained. Further, when the trapped magnetic field characteristics were measured in the same manner for one of the two cylindrical synthetic crystals having a thickness of 7.5 mm, a value of 0.21 T was obtained.

(Example 2)
In the same manner as in Example 1, three Y-Ba-Cu-O-based cylindrical synthetic crystals having a diameter of 30 mm and a height of 15 mm were synthesized. When the trapped magnetic field characteristics were measured with a Hall element under liquid nitrogen cooling (77K) using a Fe-Nd-B magnet having a surface magnetic field of 0.4T, the peak magnetic fields were 0.20T, 0.21T, and 0.19T. A value was obtained. From these three cylindrical synthetic crystals, the upper 3 mm and the lower 7 mm where the seeds are placed are separated, and three central cylindrical synthetic crystals with a thickness of 5 mm are prepared. Glycerin is placed between the central cylindrical synthetic crystals. A superconducting bulk body consisting of a stack of 15 mm in height was produced by superimposing three coatings. When the trapped magnetic field characteristics were measured with a Hall element under liquid nitrogen cooling (77 K) using a Fe—Nd—B magnet having a surface magnetic field of 0.4 T, a value of 0.34 T was obtained. Further, when the trapped magnetic field characteristics were measured in the same manner for one of the three prepared cylindrical synthetic crystals having a thickness of 5 mm, a value of 0.18 T was obtained.

(Example 3)
In the same manner as in Example 1, three Y-Ba-Cu-O-based cylindrical synthetic crystals having a diameter of 30 mm and a height of 15 mm were synthesized. When the trapped magnetic field characteristics were measured with a Hall element under liquid nitrogen cooling (77K) using a Fe-Nd-B magnet having a surface magnetic field of 0.4T, the peak magnetic fields were 0.18T, 0.21T, and 0.19T. A value was obtained. From these three cylindrical synthetic crystals, the upper 2.5 mm and the lower 5 mm where the seeds were placed were separated, and three central cylindrical synthetic crystals with a thickness of 7.5 mm were prepared. Glycerin was applied in between, and three were superposed to produce a superconducting bulk body consisting of a stack of 22.5 mm in height. When the trapped magnetic field characteristics were measured with a Hall element under liquid nitrogen cooling (77 K) using a Fe—Nd—B magnet having a surface magnetic field of 0.4 T, a value of 0.38 T was obtained.

Example 4
(Nd, Eu, Gd) Ba ₂ Cu ₃ O _y and (Nd, Eu, Gd) ₂ BaCuO ₅ powders having a mixing ratio of Nd, Eu and Gd of 1: 1: 1 were prepared, and the weight ratio of these compounds Was weighed so as to be 4: 1, 0.5 wt% Pt was added, and then mixed well. Thereafter, it was molded into pellets having a diameter of 50 mm and a thickness of 20 mm under a hydrostatic pressure of 2000 MPa. The pellet was heated in air at 900 ° C. for 1 hour and pre-sintered.
Next, on an Al ₂ O ₃ plate having a diameter of 50 mm and a thickness of 2 mm, first, Nd ₂ O ₃ powder formed into a pellet shape having a diameter of 45 mm and a thickness of 2 mm is placed, and further BaCuO ₂ powder is added. The one formed into a pellet shape having a diameter of 45 mm and a thickness of 10 mm was placed. In addition, the prepared (Nd, Eu, Gd) -Ba-Cu-O sintered body was installed.
Thereafter, the above precursor structure is installed together with the Al ₂ O ₃ plate in an electric furnace adjusted to an atmosphere of 1% O ₂ + 99% Ar, and the (Nd, Eu, Gd) -Ba-Cu-O sintered body is An NdBa ₂ Cu ₃ O _y single crystal having a diameter of ₂ mm and a thickness of 1 mm was placed in the center as a seed. After being installed in the electric furnace, the electric furnace is heated to 1100 ° C. at a rate of 50 ° C./h, held for 1 hour, cooled to 1050 ° C. for 1 hour, and then to 950 ° C. at a rate of 0.2 ° C./h. Slow cooling followed by furnace cooling. The sample taken out from the furnace had a diameter of 30 mm and a height of 15 mm. Finally, an oxygen annealing treatment was performed at 300 ° C. for 200 hours in a 100% oxygen stream to obtain a cylindrical synthetic crystal. In this state, the superconducting critical temperature was measured, and a value of 95K was obtained. When the trapped magnetic field characteristics were measured with a Hall element under liquid nitrogen cooling (77 K) using a Fe—Nd—B magnet having a surface magnetic field of 0.5 T, a value of 0.31 T was obtained as the peak magnetic field.
Next, in the same manner, two (Nd, Eu, Gd) -Ba-Cu-O-based cylindrical synthetic crystals are produced, and liquid nitrogen is used using a Fe-Nd-B magnet having a surface magnetic field of 0.5 T. When the trapped magnetic field characteristics were measured with a Hall element under cooling (77 K), trapped magnetic fields of 0.29 T and 0.30 T were obtained, respectively. From these two cylindrical synthetic crystals, the upper 2.5 mm and the lower 5 mm where the seeds are placed are separated, and two central cylindrical synthetic crystals having a thickness of 7.5 mm are prepared. Glycerin was applied in between, and two were superposed to produce a superconducting bulk body having a height of 15 mm. When the trapping magnetic field characteristics were measured with a Hall element under liquid nitrogen cooling (77 K) using a Fe—Nd—B magnet having a surface magnetic field of 0.5 T, a value of 0.40 T was obtained. Further, when the captured magnetic field characteristics were measured in the same manner for one of the two cylindrical synthetic crystals having a thickness of 7.5 mm, the value of 0.31 T was obtained.

(Example 5)
In the same manner as in Example 1, three Y-Ba-Cu-O-based cylindrical synthetic crystals having a diameter of 30 mm and a height of 15 mm were synthesized.
The cylindrical synthetic crystal was attached to the tip of the cold head of the refrigerator with vacuum grease, and was placed in a superconducting coil having a central magnetic field of 5 T and a bore diameter of 50 mm, and was placed without applying a magnetic field. Then, after applying a magnetic field of 5T, cooling to 50K by cooling with a refrigerator and measuring the captured magnetic field characteristics with a Hall element in a state where the external magnetic field was zero, the peak magnetic field was 2.5T, 2.4T, A value of 2.6T was obtained.
From these three columnar synthetic crystals, the upper part where the seeds are placed is separated into 3 mm and the lower part 7 mm, and three cylindrical synthetic crystal central parts having a thickness of 5 mm are prepared, and glycerin is provided between the cylindrical synthetic crystal central parts. A superconducting bulk body having a height of 15 mm was produced by superimposing three pieces. At this time, it was set so that the subboundaries accompanying crystal growth called the facets of the bulk body to be overlapped overlap.
The superconducting bulk body composed of the three central parts of the synthetic crystal constructed as described above is attached to the tip of the cold head of the refrigerator by vacuum grease and installed in a superconducting coil having a central magnetic field of 5T. And installed without applying a magnetic field. Thereafter, in a state where a magnetic field of 5T was applied, cooling to 50K was performed by cooling the refrigerator, and the captured magnetic field characteristics were measured with a Hall element in a state where the external magnetic field was zero. As a result, a value of 3.84 T was obtained as the peak magnetic field.
Next, three cylindrical synthetic crystals with exactly the same thickness of 5 mm are formed in a cylindrical shape so that the subboundaries associated with crystal growth called facet lines in the central portion of the cylindrical synthetic crystals are inclined by 30 ° from each other. Glycerin was applied between the central portions of the synthetic crystals, and a superconducting bulk body consisting of a stack having a height of 15 mm was prepared by superimposing three pieces. The superconducting bulk body composed of the three central parts of the synthetic crystal constructed as described above is attached to the tip of the cold head of the refrigerator by vacuum grease and installed in a superconducting coil having a central magnetic field of 5T. And installed without applying a magnetic field. Thereafter, in a state where a magnetic field of 5T was applied, cooling to 50K was performed by cooling the refrigerator, and the captured magnetic field characteristics were measured with a Hall element in a state where the external magnetic field was zero. As a result, a value of 4.12 T was obtained as the peak magnetic field.

(Example 6)
YBa ₂ Cu ₃ O _y and Y ₂ BaCuO ₅ powders were prepared, weighed so that the weight ratio of these compounds was 10: 4, 0.5 wt% Pt was added, and then mixed well. Thereafter, it was molded into a pellet having a diameter of 45 mm and a thickness of 20 mm under a hydrostatic pressure of 2000 MPa. The pellet was heated in air at 900 ° C. for 1 hour and pre-sintered. Next, six artificial holes having a diameter of 2 mm were formed at equal intervals along a circumference of 20 mm from the center of the sintered body by a carbide drill in the central axis direction.
First, Y ₂ O ₃ powder formed into a 45 mm diameter and 2 mm thick pellet is placed on an Al ₂ O ₃ plate having a diameter of 50 mm and a thickness of 2 mm, and then BaCuO ₂ powder is further added to a 45 mm diameter and thickness. A 10-mm pellet was molded. On top of that, a Y-Ba-Cu-O sintered body that was calcined and provided with six artificial holes was installed.
Thereafter, a set of precursors on an Al ₂ O ₃ plate is installed in an electric furnace in the atmosphere, and NdBa ₂ Cu ₃ O _y is 2 mm square and 1 mm thick at the center of the Y-Ba-Cu-O sintered body. A single crystal was placed as a seed. Thereafter, the electric furnace was heated to 1100 ° C. at a rate of 50 ° C./h, held for 1 hour, cooled to 1050 ° C. for 1 hour, and then gradually cooled to 950 ° C. at a rate of 0.2 ° C./h. Furnace cooling was performed. The sample taken out from the furnace had a diameter of 30 mm and a height of 15 mm. Further, although the artificial holes had a diameter of about 1.5 mm, it was confirmed that they were distributed at equal intervals on a concentric circle having a diameter of about 15 mm. Finally, an oxygen annealing treatment was performed at 400 ° C. for 100 hours in a 100% oxygen stream to obtain a cylindrical synthetic crystal. In this state, the superconducting critical temperature was measured, and a value of 90K was obtained. Furthermore, when the trapping magnetic field characteristics were measured with a Hall element under liquid nitrogen cooling (77 K) using a Fe—Nd—B magnet having a surface magnetic field of 0.4 T, a value of 0.21 T was obtained as the peak magnetic field.
Next, two bulk Y-Ba-Cu-O columnar synthetic crystals having six artificial holes having a final diameter of 1.5 mm were prepared by the same method, and the surface magnetic field was 0.4 T Fe--. When the trapping magnetic field characteristics were measured with a Hall element under liquid nitrogen cooling (77 K) using an Nd-B magnet, trapping magnetic fields of 0.20 T and 0.19 T were obtained, respectively. From these two cylindrical synthetic crystals, the upper 2.5 mm and the lower 5 mm where the seeds were placed were cut off, and two cylindrical synthetic crystal central parts having a thickness of 7.5 mm were prepared. Next, six aluminum rods having a diameter of 1.4 mm and a length of 15 mm were inserted into the artificial hole, and the two holes were combined vertically so as to penetrate the central part of the two cylindrical synthetic crystals. After that, the Pb—Bi—Sn alloy was heated to 200 ° C. and then deaerated with a vacuum pump, thereby vacuum impregnating the central portion of the cylindrical synthetic crystal. This alloy filled the void between the aluminum and the artificial hole in the central portion of the cylindrical synthetic crystal by this treatment, and confirmed that the two central portions of the cylindrical synthetic crystal were firmly bonded. Next, when the captured magnetic field characteristics were measured with a Hall element under liquid nitrogen cooling (77 K) using a Fe—Nd—B magnet having a surface magnetic field of 0.4 T, a value of 0.34 T was obtained.

(Example 7)
A superconducting bulk body composed of a stack of 15 mm in height, in which glycerin is applied between two central synthetic crystal cylinders having a thickness of 7.5 mm used in Example 1 and two are stacked. The following excitation process was performed.
The superconducting bulk was attached to the tip of the cold head of the refrigerator by vacuum grease. At this time, an aluminum disk (having a diameter of 30 mm and the thickness of both ends changed from 4 mm to 1 mm) with a taper of 3 mm so that the central axis is inclined from the central axis of the applied magnetic field is first And a superconducting bulk material was deposited thereon.
Then, it installed in the state which applied the magnetic field in the superconducting coil whose central magnetic field is 5T. Thereafter, in a state where a magnetic field of 5T was applied, the external magnetic field was set to zero by cooling to 50K by cooling with a refrigerator. At this time, the center portion of the two cylindrical synthetic crystals was shifted up and down. This is thought to be because the position of the central portion of the cylindrical synthetic crystal is shifted due to the electromagnetic force acting during excitation because the coupling between the central portions of the two cylindrical synthetic crystals is insufficient. In this state, the captured magnetic field characteristics were measured with a Hall element. As a result, a value of 2.84 T was obtained as the peak magnetic field.
Next, after providing the six artificial holes synthesized in Example 6, the superconductivity composed of two cylindrical synthetic crystal central portions firmly bonded by vacuum impregnation with an aluminum rod and a Pb—Bi—Sn alloy. The same excitation treatment was performed on the bulk body. As a result, no deviation occurred at the center of the cylindrical synthetic crystal, and a high value of 3.9 T was obtained for the trapping magnetic field.

(Example 8)
After the six artificial holes synthesized in Example 6 were provided, it was composed of a stack composed of two cylindrical synthetic crystal central parts firmly bonded by vacuum impregnation with an aluminum rod and a Pb—Bi—Sn alloy. The following excitation treatment was applied to the superconducting bulk material.
The superconducting bulk was attached to the tip of the cold head of the refrigerator by vacuum grease. At this time, an aluminum disk (having a diameter of 30 mm and the thickness of both ends changed from 4 mm to 1 mm) with a taper of 3 mm so that the central axis is inclined from the central axis of the applied magnetic field is first And a superconducting bulk material was deposited thereon.
Then, it installed in the state which applied the magnetic field in the superconducting coil whose central magnetic field is 10T. Thereafter, in a state where a magnetic field of 10T was applied, the external magnetic field was set to zero by cooling to 30 K by cooling with a refrigerator.
At this time, the center portion of the two cylindrical synthetic crystals was shifted up and down. This is thought to be because the position of the central portion of the cylindrical synthetic crystal is shifted due to the electromagnetic force acting during excitation because the coupling between the central portions of the two cylindrical synthetic crystals is insufficient. In this state, the captured magnetic field characteristics were measured with a Hall element. As a result, a value of 4.4 T was obtained as the peak magnetic field.
Next, in the same manner as in Example 6, after six artificial holes were provided, the central part of two cylindrical synthetic crystals firmly bonded by vacuum impregnation with an aluminum rod and a Pb—Bi—Sn alloy were used. A superconducting bulk body composed of the stacks was prepared.
Next, after expanding the ring made of Fe-28Mn-6Si-5Cr alloy, which is a kind of iron-based shape memory alloy having an inner diameter of 29 mm and a thickness of 3 mm, at room temperature so that the inner diameter becomes 30.5 mm, It arranged on the side periphery of the superconducting bulk body, and it heated at 200 degreeC. By this treatment, the ring contracted due to the shape memory effect of the alloy, and the superconducting bulk magnet was firmly fastened.
A superconducting bulk body tightened and strengthened with an iron-based shape memory alloy was attached to the tip of the cold head of the refrigerator with vacuum grease. At this time, an aluminum disk (having a diameter of 30 mm and the thickness of both ends changed from 4 mm to 1 mm) with a taper of 3 mm so that the central axis is inclined from the central axis of the applied magnetic field is first And a superconducting bulk magnet was attached on the substrate.
Thereafter, a superconducting bulk body reinforced with an iron-based shape memory alloy was placed in a superconducting coil having a central magnetic field of 10 T without applying a magnetic field. Thereafter, in a state where a magnetic field of 10T was applied, the external magnetic field was set to zero by cooling to 30 K by cooling with a refrigerator.
At this time, the position of the central portion of the cylindrical synthetic crystal was not displaced at all by the electromagnetic force that was applied during excitation, and the state of being installed was maintained. Furthermore, as a result of measuring the trapping magnetic field characteristics with the Hall element in this state, a value of 9.44 T was obtained as the peak magnetic field.

Example 9
A superconducting bulk body composed of a stack of 15 mm in height, in which glycerin is applied between two central synthetic crystal cylinders having a thickness of 7.5 mm used in Example 1 and two are stacked. The following excitation process was performed.
The superconducting bulk was attached to the tip of the cold head of the refrigerator by vacuum grease. At this time, an aluminum disk (having a diameter of 30 mm and the thickness of both ends changed from 4 mm to 1 mm) with a taper of 3 mm so that the central axis is inclined from the central axis of the applied magnetic field is first And a superconducting bulk material was deposited thereon.
Then, it installed in the state which applied the magnetic field in the superconducting coil whose central magnetic field is 5T. Thereafter, in a state where a magnetic field of 5T was applied, the external magnetic field was set to zero by cooling to 50K by cooling with a refrigerator.
At this time, the center portion of the two cylindrical synthetic crystals was shifted up and down. This is thought to be because the position of the central portion of the cylindrical synthetic crystal is shifted due to the electromagnetic force acting during excitation because the coupling between the central portions of the two cylindrical synthetic crystals is insufficient. In this state, the captured magnetic field characteristics were measured with a Hall element. As a result, a value of 2.84 T was obtained as the peak magnetic field.
Next, a superconducting bulk body made of a stack having a height of 15 mm was prepared by superimposing two cylindrical synthetic crystal central portions produced by the same method as in Example 1.
Next, after expanding the ring made of Fe-28Mn-6Si-5Cr alloy, which is a kind of iron-based shape memory alloy having an inner diameter of 29 mm and a thickness of 3 mm, at room temperature so that the inner diameter becomes 30.5 mm, It arranged on the side periphery of the superconducting bulk body, and it heated at 300 degreeC. By this treatment, the ring contracted due to the shape memory effect of the alloy, and the superconducting bulk body was firmly fastened.
A superconducting bulk body fastened by an iron-based shape memory alloy ring was attached to the tip of the cold head of the refrigerator by vacuum grease. At this time, an aluminum disk (having a diameter of 30 mm and the thickness of both ends changed from 4 mm to 1 mm) with a taper of 3 mm so that the central axis is inclined from the central axis of the applied magnetic field is first And a superconducting bulk material was deposited thereon. Then, it installed in the state which applied the magnetic field in the superconducting coil whose central magnetic field is 5T. Thereafter, in a state where a magnetic field of 5T was applied, the external magnetic field was set to zero by cooling to 50K by cooling with a refrigerator.
At this time, the position of the central portion of the cylindrical synthetic crystal was not displaced at all by the electromagnetic force that was applied during excitation, and the state of being installed was maintained. Furthermore, as a result of measuring the captured magnetic field characteristics with the Hall element in this state, a value of 3.7 T was obtained as the peak magnetic field.

  Each of the circular synthetic crystal intermediates constituting the stack of superconducting bulk materials produced in all the examples described above satisfies the expressions (1) and (2).

(Test Example 1)
By adjusting the manufacturing conditions of Example 1, a superconducting bulk body in which the composition of the superconducting phase on the upper surface was changed was manufactured, and the characteristics were examined and compared. Specifically, superconducting bulk body lower surface of the superconducting phase is YBa ₂ Cu ₃ O _y, superconducting phases of the upper surface is a _{Y x Ba 2 Cu 3 O y} , the Y _x Ba ₂ Cu ₃ O and x values of _y will produce a sample that is 0.9,0.95,1.0,1.05,1.10,1.20, measuring the critical current density (Jc) and critical temperature (Tc) did. The relationship between x value and critical temperature (Tc) is shown in Table 1, and the relationship between x value and critical current density (Jc) is shown in FIG.

(Test Example 2)
A test similar to Test Example 1 was performed using NdBa ₂ Cu ₃ O _y instead of YBa ₂ Cu ₃ O _y . That is, the superconducting phase on the lower surface of the superconducting bulk body is NdBa ₂ Cu ₃ O _y , the superconducting phase on the upper surface is Nd _x Ba ₂ Cu ₃ O _y , and _{x of the} Nd _x Ba ₂ Cu ₃ O _y Samples having values of 0.9, 0.95, 1.0, 1.05, 1.10, and 1.20 were manufactured, and critical temperature (Tc) and critical current density (Jc) were measured. The relationship between the x value and the critical temperature (Tc) is shown in Table 2, and the relationship between the x value and the critical current density (Jc) is shown in FIG.

(Test Example 3)
By adjusting the materials used in Example 1 and the manufacturing conditions, a superconducting bulk body in which the angle between the c-axis closest to the c-axis among the main axes of the crystal observed on the lower surface was changed was manufactured. The characteristics were investigated and compared. Specifically, the angles formed between the c-axis and the principal axis of the crystal observed on the lower surface of the superconducting bulk body are 0 °, 2 °, 5 °, 8 °, and 10 °. Samples were manufactured and the critical current density (Jc) was measured. FIG. 15 shows the relationship between the angle θ formed with the c-axis and the critical current density (Jc).

The results of Test Example 1 and Test Example 2 show that a superconducting bulk body having an X value of the superconducting phase RE _x Ba ₂ Cu ₃ O _{y on} the upper surface of 0.93 to 1.07 achieved a high critical current density. It shows that. The result of Test Example 3 shows that the superconducting bulk material in which the angle between the c-axis closest to the c-axis and the c-axis of the main axis of the crystal observed on the lower surface achieves a high critical current density. It shows that.

  Since the superconducting bulk magnet produced using the superconducting bulk material of the present invention has high magnetic field strength, magnetic field control with high directivity can be performed by using this magnet. In addition, the superconducting bulk magnet of the present invention can be made uniform and highly reliable by suppressing uneven magnetic characteristics in the magnet surface, and also has good thermal conductivity, high mechanical characteristics, and robustness. It can also be a simple magnet. Therefore, the superconducting bulk magnet of the present invention can be widely used in a wide range of industries including the diagnostic / medical field, the electronics field, the environmental field, and the electrical field.

DESCRIPTION OF SYMBOLS 11 Cylindrical synthetic crystal 12 Upper part 13 Lower 14 Cylindrical synthetic crystal center part 15, 16 Cylindrical synthetic crystal cut piece 21 Center axis 22, 23 Cylindrical crystal piece 31 Sector boundary 32, 33, 34 Cylindrical crystal piece 41, 51, 61, 71 Cylindrical crystal pieces 42, 52, 62, 72 Through holes 43, 53, 63, 73 Thermally conductive members 74 Heat sinks 81, 91, 101, 111, 121 Cylindrical crystal pieces 82, 92, 122 Go belt 102, 112 Go wire 123 Upper extension 124 Lower extension 125 Center line

Claims (20)

A superconducting bulk body including RE-Ba-Cu-O columnar crystal pieces,
RE represents one or more elements selected from the group consisting of Y, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu;
A superconducting bulk body in which the upper and lower surfaces of the RE-Ba-Cu-O-based columnar crystal piece satisfy the following formulas (1) and (2).
Formula (1): 0.93 ≦ X ≦ 1.07
(In the above formula, X represents the X value in the superconducting phase composition formula RE _x Ba ₂ Cu ₃ O _y (y is 6.8 to 7.0).)
Formula (2): θc ≦ 6 °
(In the above equation, θc represents the angle formed by the c-axis closest to the c-axis among the main axes of the crystal observed on the upper surface or the lower surface, and when the main axis of the crystal is not observed in the region, the equation (2) Is not satisfied.)   The RE-Ba-Cu-O-based columnar crystal piece is a columnar synthetic crystal central portion obtained by removing an upper portion and a lower portion of a columnar synthetic crystal synthesized by a seed crystal melting method, or the columnar synthetic crystal center The superconducting bulk material according to claim 1, which is a cylindrical synthetic crystal cut piece obtained by cutting the portion in a direction perpendicular to the central axis.   A superconducting bulk body comprising a stack in which at least two of the RE-Ba-Cu-O columnar crystal pieces according to claim 1 or 2 are stacked in a central axis direction.   4. The superconducting bulk body according to claim 3, wherein the stack is stacked so that the RE-Ba-Cu—O-based columnar crystal pieces are shifted in crystal orientation in a plane perpendicular to a central axis. 5. .   The superconducting bulk body according to any one of claims 1 to 4, wherein a hole is formed in the columnar crystal piece, and a heat conductive member is inserted into the hole.   The superconducting bulk material according to claim 5, wherein a resin or a metal is impregnated between an inner wall of the hole and an outer surface of the thermally conductive member.   The superconducting bulk body according to any one of claims 1 to 6, wherein an outer surface of the columnar crystal piece is impregnated with a resin or a metal.   The superconducting bulk body according to any one of claims 1 to 7, further comprising a fastener that compresses the cylindrical crystal piece from the outside of the cylindrical crystal piece.   The superconducting bulk body according to claim 8, wherein the fastener is made of a shape memory alloy.   The superconducting bulk magnet using the superconducting bulk body as described in any one of Claims 1-9. A method for producing a superconducting bulk material including cylindrical crystal pieces, comprising the following step 1.
<Step 1>
The upper and lower parts of the cylindrical synthetic crystal synthesized by the seed crystal melting method are removed to obtain the central part of the cylindrical synthetic crystal, or the central part of the cylindrical synthetic crystal is cut in a direction perpendicular to the central axis to obtain a circle. A step of obtaining a columnar synthetic crystal cut piece. The method for producing a superconducting bulk material according to claim 11, comprising the following step 2 after the step 1.
<Process 2>
A step of stacking any two or more of the columnar synthetic crystal central portion and the columnar synthetic crystal cut pieces obtained in step 1 in a central axis direction to form a stack.   The columnar synthetic crystal is a RE-Ba-Cu-O-based columnar synthetic crystal, and the columnar crystal piece is a RE-Ba-Cu-O-based columnar crystal piece. A method for producing a superconducting bulk material (RE is one or more elements selected from the group consisting of Y, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu. To express).   The method for producing a superconducting bulk body according to any one of claims 11 to 13, wherein in the step 1, the thicknesses of the upper part and the lower part removed from the cylindrical synthetic crystal are each 0.1 mm or more. In the step 1, the columnar synthetic crystal is obtained by growing a crystal by placing a seed crystal on the upper surface of a columnar pellet, and removing the upper part of the columnar synthetic crystal after removing the upper part thereof. The manufacturing method of the superconductor bulk body as described in any one of Claims 11-14 performed so that the composition in the upper surface of may satisfy | fill following formula (1).
Formula (1): 0.93 <= X <= 1.07%
(In the above formula, X represents the X value in the superconducting phase composition formula RE _x Ba ₂ Cu ₃ O _y (y is 6.8 to 7.0).) In the step 1, the columnar synthetic crystal is obtained by growing a crystal by placing a seed crystal on the upper surface of a columnar pellet, and removing the upper part of the columnar synthetic crystal after removing the upper part thereof. The manufacturing method of the superconductor bulk body as described in any one of Claims 13-15 performed so that the element content rate in the upper surface of may satisfy | fill following formula (3).
Formula (3): | M _RES (center upper surface) −M _RES (pellet) | ≦ 7 atomic%
(In the above formula, M _RES (center top surface) is the content of RE ^S _i element in the top surface of the cylindrical synthetic crystal center (the number of RE ^S _i elements relative to the total number of RE elements). M _RES (pellet) is the content of RE ^S _i element in the cylindrical pellet (the number of atoms of RE ^S _i element relative to the number of atoms of all RE elements, and the unit is atomic%) The RE ^S element is one or two selected from the group consisting of Y, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu contained in the seed crystal. It represents or more elements, i is representative of the type of RE ^S element.) In the step 1, the cylindrical synthetic crystal is obtained by growing a crystal by placing a seed crystal on the upper surface of a cylindrical pellet, and removing the lower portion of the cylindrical synthetic crystal from the surface after removing the lower portion to a thickness of 0.1 mm The method for producing a superconducting bulk body according to any one of claims 10 to 16, which is performed so that the region of the above satisfies the following formula (2).
Formula (2): θc ≦ 6 °
(In the above equation, θc represents the angle formed by the c-axis and the principal axis of the crystal that is observed on the upper surface or the lower surface, and when the main axis of the crystal is not observed in the region, the equation ( 2) shall not be satisfied.)   The manufacturing method of the superconductor bulk body as described in any one of Claims 10-17 whose upper part thickness removed from the said cylindrical synthetic crystal is 1-5 mm.   The method for producing a superconducting bulk body according to any one of claims 10 to 18, wherein a thickness of a lower portion to be removed from the cylindrical synthetic crystal is 1 to 15 mm.   The superconducting bulk body manufactured by the manufacturing method as described in any one of Claims 10-19.

Images