JP5195961B2 - Oxide superconducting bulk magnet member - Google Patents

Description

  The present invention relates to an oxide superconducting bulk magnet member.

The oxide superconducting material in which the RE ₂ BaCuO ₅ phase is dispersed in the REBa ₂ Cu ₃ O _7-x (RE is a rare earth element) phase to form a bulk body has a high critical current density (J _c ). Excited by cooling in a magnetic field or pulsed magnetization, it can be used as an oxide superconducting bulk magnet. For example, Patent Document 1 discloses a superconducting magnetic field generator that can use such an oxide superconducting material (oxide superconducting bulk) in a superconducting motor or the like.

  Non-patent document 1 discloses a bulk magnet that can generate a magnetic field of up to about 1.5 T using a cylindrical Sm-based bulk superconductor with a diameter of 36 mm magnetized by cooling in a magnetic field. . Y. Non-Patent Document 2 discloses that Itoh et al. Use Y-based bulk superconducting materials to compare pulse magnetization and magnetization by cooling in a magnetic field. Further, Morita et al. Discloses that a magnetic field of about 4.5 T is generated at 40K using a bulk superconducting material having a diameter of about 60 mm in a superconducting magnet. As described above, regarding the pulse magnetization of the RE-based bulk superconducting material, Patent Document 1 discloses pulse magnetization accompanied by magnetic flux jump, and Non-Patent Document 2, Non-Patent Document 3, and the like include a cooling method. A magnetizing method is disclosed.

Recently, Sawamura et al., In Patent Document 4, disclosed a high magnetic field inside a ring-shaped bulk superconductor (RE ^II Ba ₂ Cu ₃ O _7-x ) having a high critical current density (J _c ) characteristic in a low magnetic field. By arranging superconducting bulk materials consisting of two types of RE systems, cylindrical bulk superconductors (RE ^I Ba ₂ Cu ₃ O _7-x ) with high J _c characteristics, from low magnetic fields to high magnetic fields A superconducting bulk magnet is disclosed that can provide a large trapping field. The superconducting bulk magnet is magnetized under a static magnetic field.

  Patent Document 5 provides a large trapping magnetic field from a low magnetic field to a high magnetic field by arranging superconducting bulk materials composed of two or three types of RE systems having different compositions, that is, different superconducting properties. A superconducting bulk magnet is disclosed (see FIGS. 1, 5 and 8 of Patent Document 5). Specifically, two types (or three types) of superconducting bulk bodies with different critical current density characteristics are used, and a material having a large critical current density with a low magnetic field is arranged at the periphery, and the magnetic field strength is high. By arranging a material having a high magnetic field and a high current density in the central part, it is possible to generate a strong magnetic field as a whole. As a magnetization method, a case where a superconducting magnet is formed by a static magnetic field magnetization method and a case where a superconducting magnet is formed by a pulse magnetization method are described.

  The one described in Patent Document 6 is basically an oxide superconducting bulk magnet having a hollow interior (a plurality of hollow oxide superconducting magnets) in order to save raw materials and produce a lightweight oxide superconducting bulk magnet. It is said that it can be reduced in weight by being hollow. Regarding the magnetization of the superconducting bulk magnet, it is immersed in liquid nitrogen to be in a superconducting state, and a magnetic field is applied from the outside to trap the magnetic flux lines in the superconductor to form a permanent magnet, that is, a static magnet. The magnetic field magnetization method is used. In Patent Document 7, in order to solve the problem of characteristic deterioration due to heat generation in pulse magnetization, the trapped magnetic flux characteristic at the time of pulse magnetization is improved by providing a refrigerant flow path between the superconductors. It is disclosed.

As described above, in the RE-based (RE-Ba-Cu-O-based) oxide bulk body, the magnetic field as a magnet (magnet) is improved as a bulk magnet by improving the configuration of the oxide superconducting bulk body and the magnetization method. Strength has been improved.

JP-A-6-20837 JP-A-6-168823 Japanese Patent Laid-Open No. 10-12429 JP 2001-358007 A JP-A-9-255333 JP 7-2111538 A JP 2006-319000 A

Ikuta et al .; Japan Society of Applied Magnetics Vol.23, No.4-1, (1999) p.885 Y, Itoh et al., Jpn J. Appl. Phys., Vol34, 5574 (1995) Morita et al .; Journal of Applied Magnetics Society of Japan Vol19, No3. (1995) p.744

An oxide bulk body in which the RE ₂ BaCuO ₅ phase (211 phase) is dispersed in the REBa ₂ Cu ₃ O _7-x phase (123 phase) is mainly formed by crystal growth from a seed crystal of several mm square and is in a single crystal form Manufactured as a bulk body. Since the 123 phase during crystal growth is a tetragonal crystal, when the ab plane of a certain crystal is brought into contact by a normal seeding method, it grows while forming a 4-fold symmetrical facet plane in the seeding surface. The superconducting properties of oxide bulk bodies produced by crystal growth in this way generally have a four-fold symmetry inhomogeneity. As a specific example, FIG. 6A shows a trapped magnetic flux distribution magnetized by a static magnetic field on a disk-shaped oxide bulk body. As shown in FIG. 6A, it can be seen that the trapped magnetic flux distribution is deviated from the concentric circle and is distorted symmetrically four times. That is, as described above, an oxide bulk body in which the 211 phase is dispersed in the 123 phase can be a bulk magnet, but has a distorted magnetic flux distribution as shown in FIG. When actually used as a magnet for a superconducting motor, a superconducting generator, etc., there is a problem that efficient driving and power generation cannot be performed.

  Conventionally, as described above, in the superconducting bulk magnet using the RE-Ba-Cu-O-based oxide bulk body, the emphasis has been on improving the magnetic field strength. In this way, magnetic flux distribution (magnetic field strength distribution) of bulk magnets cannot be efficiently driven or generated when incorporated as a magnet of a superconducting motor or superconducting generator that is actually used even if the magnetic field strength is high. ) Is not uniform. Therefore, when such an oxide bulk body is used as a superconducting bulk magnet, it is important not to have such a distorted magnetic flux distribution but to have a uniform magnetic field distribution (for example, concentrically uniform magnetic field distribution). It has become clear that.

On the other hand, in the technique described in Patent Document 5, in order to obtain a strong magnetic field as a superconducting bulk magnet using the RE-Ba-Cu-O-based oxide bulk body as described above, for example, a peripheral portion of the bulk magnet is used. Is composed of a Y-based oxide superconducting bulk body having a large critical current density in a low magnetic field, and the central portion of the bulk magnet is composed of an Nd-based oxide superconducting bulk body having a large critical current density in a high magnetic field. It is. However, it is neither described nor suggested that it is important to obtain a uniform magnetic field as a superconducting bulk magnet, nor is its configuration shown. As a method for obtaining a strong uniform magnetic field, a configuration in which a plurality of ring-shaped grooves are provided in a donut-shaped copper plate and a RE-Ba-Cu-O-based oxide bulk body is embedded in the grooves is shown. The coil magnet is not a bulk magnet but a superconducting coil, and in such a coil magnet, the proportion of the copper plate of the incidental material increases, so the ratio of the generated magnetic field strength to the magnet mass decreases.

  Although the superconducting bulk magnet using the RE-Ba-Cu-O-based oxide bulk body as described above is lighter than an electromagnet using a metal magnet or a coil, Patent Document 6 discloses such an oxidation. In order to make a superconducting bulk magnet that is lighter and can use less raw materials as a superconducting bulk magnet using objects, the central part of the bulk magnet is hollowed out so that superconducting current does not flow in unnecessary parts And a plurality of hollow superconducting bulk bodies are combined. However, there is no description or suggestion that it is important in practical use to make the magnetic flux distribution of the bulk magnet uniform, and the configuration is not shown.

  In addition, as in the technique described in Patent Document 6, it is lighter and the idea of reducing the amount of raw material to be used is to increase the size of the superconducting bulk magnet so that there is no superconductor at the center. Actually, the inner diameter of the hollow portion is actually as large as 46.7% (Example 1, Example 4) or 33.3% (Example 3) with respect to the outer diameter of the bulk magnet. Therefore, such a bulk magnet cannot always make the magnetic flux distribution uniform. In particular, uniform magnetic flux distribution cannot be maintained in an environment where the magnet is used as a rotating body such as a superconducting motor or superconducting generator. Furthermore, although it is described that it has the same performance as a superconducting bulk magnet that is hollow and filled up to the inside, in fact, as a bulk magnet, the internal superconductor also makes a finite contribution, The characteristic (magnetic field strength) is lower than that of a bulk magnet packed up to the inside, and this difference becomes prominent when compared with a strong magnetic field strength, and also appears significantly depending on the magnetization method.

  In order to obtain an oxide superconducting bulk magnet using the RE-Ba-Cu-O-based oxide bulk body as described above, such an oxide bulk body is formed by a static magnetic field magnetization method or a pulse magnetization method. Magnetize. In particular, in the case of simple magnetizing in a device, the pulse magnetizing method is preferable for a superconducting bulk magnet having a strong magnetic field. However, in the pulse magnetization method, there is a problem that when attempting to magnetize a strong magnetic field, the magnetic flux distribution becomes non-uniform and a uniform magnetic flux distribution cannot be obtained. This is due to the following.

The pulse magnetization method is a magnetization method that involves a sudden change in magnetic field. Therefore, the magnetic flux rapidly moves in the superconductor during magnetization, and large heat is generated in the superconductor. For this reason, if the generated heat causes the temperature of the portion to rise and the superconducting property of the portion is lowered, the movement of the magnetic flux is more likely to occur. Such a cycle (heat generation, temperature rise, superconducting characteristic decrease, magnetic flux movement, heat generation) is repeated even if there is a slight nonuniformity in the characteristics of the superconductor to emphasize the nonuniformity of the characteristics. Thus, a non-uniform magnetic flux trapping distribution is obtained. For example, when a general disk-type oxide superconducting bulk magnet member is magnetized to form a bulk magnet, a superconducting current flows concentrically around the disk if the material characteristics are completely uniform. In this case, when the magnetic flux density is taken in the height direction, a conical magnetic flux density distribution is obtained. However, the material characteristics cannot be completely uniform in an actual material, and the conical uniform magnetic flux density distribution cannot be obtained by the pulse magnetization method. When magnetized by the pulse magnetization method, the non-uniformity of the magnetic flux distribution becomes more prominent and more noticeable as the applied magnetic field change rate and magnetic field strength increase, and as the superconductor size increases, J _The higher the _c characteristic, the more likely it is to occur and the more noticeable. Accordingly, since J _c characteristics, the higher the low temperature, it can be said that there is a tendency that the cooling temperature becomes uneven trapped magnetic flux distribution as low.

As described above, Patent Document 5 describes an example in which the magnetic field is magnetized by the pulse magnetizing method. However, it only describes that a superconducting magnet having a strong magnetic field is realized. Is not shown. Further, as described above, Patent Document 6 is only magnetized by the static magnetic field magnetization method, but does not show what the magnetic field uniformity by the pulse magnetization method is. . The structures described in Patent Document 5 and Patent Document 6 are
Even if it is pulse magnetized, it is not structured to obtain a uniform magnetic field with good reproducibility, or it may not be structured to obtain a strong magnetic field uniformly even if pulse magnetized. Further, when the RE-Ba-Cu-O-based oxide bulk body is arranged in a nested manner, it can be pulse-magnetized to form a superconducting bulk magnet having a uniform magnetic field with a strong magnetic field. When used as a magnet of a rotating machine such as a superconducting motor, the bulk oxides placed in the nest are gradually shifted due to centrifugal force and vibration, and it is impossible to maintain a uniform magnetic field with the original strong magnetic field. There's a problem.

  In addition, when a strong magnetic field is obtained by magnetizing by the pulse magnetization method, the magnetic field changes suddenly during magnetization. Therefore, when repeated pulse magnetization is performed, each oxide bulk body arranged in the nesting gradually It may become difficult to maintain a uniform magnetic field with the original strong magnetic field. Furthermore, in order to manufacture such an oxide superconducting bulk magnet member, it is necessary to process and assemble each oxide bulk body placed in the nest with high accuracy, and there is a problem that productivity is low. is there.

In view of the above problems, the present invention is an oxide superconducting bulk magnet member in which a RE ₂ BaCuO ₅ phase dispersed in an REBa ₂ Cu ₃ O _7-x phase is combined, and can be easily manufactured. Oxidation that can stably obtain a symmetrical and uniform magnetic field with a strong magnetic field even if it is repeatedly magnetized by the magnetizing method or used for a magnet of a rotating machine such as a superconducting generator or superconducting motor. An object of the present invention is to provide a superconducting bulk magnet member.

The inventors of the present invention provide an oxide superconducting bulk magnet member in which a RE ₂ BaCuO ₅ phase dispersed in a REBa ₂ Cu ₃ O _7-x phase is combined, and a plurality of the oxide bulk bodies are nested. It was found that the magnetic flux movement can be limited even with a sudden magnetic field change during pulse magnetization, and a uniform magnetic field can be obtained with a strong magnetic field. Further, even in the structure in which at least one gap between adjacent oxide bulk bodies arranged in a nested manner is connected by a joint (a structure having a seam between the oxide bulk bodies), it is strong as described above. It has been found that a uniform magnetic field can be obtained. By adopting such a configuration, even if centrifugal force, vibration, or the like is applied, or pulse magnetization is repeated, each oxide bulk body arranged in the nest does not shift. In addition, such a configuration can be easily produced without requiring a step of nesting each oxide bulk body.
That is, the gist of the present invention is as follows.
(1) REBa ₂ Cu ₃ O _7-x (RE is a rare earth element or a combination thereof. X is the amount of oxygen deficiency and 0 <x ≦ 0.2.) The RE ₂ BaCuO ₅ phase in the phase The oxide superconducting bulk magnet member is a combination of oxide bulk bodies in which particles are dispersed, wherein the oxide bulk bodies are arranged in a nested manner combining shapes including rings, and adjacent to each other in the nested manner. An oxide superconducting bulk magnet member , which is connected at one place by a joint connecting gaps of oxide bulk bodies and has solder in the gaps between the oxide bulk bodies .
(2) The oxide according to (1), wherein a width of a seam connecting the gaps of the bulk oxide body is 0.1 mm or more and 25% or less with respect to a ring circumferential distance of the gaps. Superconducting bulk magnet member.
(3) The maximum portion of the width in the direction perpendicular to the rotational symmetry axis of the ring of the oxide bulk body is more than 1.0 mm and 15.0 mm or less (1) or (2) The oxide superconducting bulk magnet member according to (2).
(4) The oxidation according to any one of (1) to (3), wherein the thickness of the ring of the oxide bulk body in the rotational symmetry axis direction is 1.0 mm or more and 5.0 mm or less. Superconducting bulk magnet member.
(5) The oxide superconducting bulk magnet member according to any one of (1) to (4), wherein the ring of the oxide bulk body is laminated in a rotationally symmetric axial direction.
(6) The axis of rotational symmetry of the ring of each of the stacked oxide bulk bodies is within a range of ± 30 ° with respect to the c _- axis of the REBa ₂ Cu ₃ O _7-x crystal (5 ) Oxide superconducting bulk magnet member.
(7) The oxide superconductivity according to (5) or (6), wherein the a-axis of the REBa ₂ Cu ₃ O _7-x crystal of each of the stacked oxide bulk bodies is shifted. Bulk magnet member.
(8) At least one of the oxide bulk bodies is a ring having a polygonal or circular shape, or a ring having a racetrack shape on the upper surface and the bottom surface. (1) to ( 7 ) The oxide superconducting bulk magnet member according to any one of the above.

  ADVANTAGE OF THE INVENTION According to this invention, the oxide superconducting bulk magnet member which can be magnetized by the pulse magnetization method and can generate | occur | produce a uniform magnetic field stably with a high magnetic field can be provided. Moreover, an oxide superconducting bulk magnet member capable of being magnetized with excellent symmetry and uniformity can be provided. Since an oxide superconducting bulk magnet that generates a high magnetic field can be more easily realized by the pulse magnetization method, a high magnetic field that cannot be obtained by a normal permanent magnet can be generated, and its industrial effect is enormous. In addition, the oxide superconducting bulk magnet member of the present invention is easy to manufacture because it does not require a step of assembling each oxide bulk body arranged in a nest. In particular, when a large number of nested oxide bulk bodies having a relatively large thickness and a large number of layers are stacked, there is a great productivity advantage due to having seams.

A plurality of oxide _{(REBa 2 Cu 3 O 7-} x phase oxide RE ₂ BaCuO ₅ phase dispersed in) the bulk material is a diagram showing a structural example arranged in nested combined shape including a ring. A plurality of oxides (oxides in which the RE ₂ BaCuO ₅ phase is dispersed in the REBa ₂ Cu ₃ O _7-x phase) are arranged in a nested structure combining a shape including a ring, and part of the oxide bulk body It is a figure which shows the structural example connected with the joint. Oxides of placing nest (REBa oxide RE ₂ BaCuO ₅ phase dispersed in ₂ Cu ₃ O _7-x phase) is a diagram showing an example of the shape of the bulk material. An oxide (an oxide in which the RE ₂ BaCuO ₅ phase is dispersed in the REBa ₂ Cu ₃ O _7-x phase) is a structural example in which a plurality of rings of a bulk body are stacked in the rotationally symmetric axis direction. It is a figure which shows a mode that it is laminated | stacked, (b) The state which has the c-axis of 123 phase in the range of +/- 30 degree.

The present inventors have magnetized an oxide superconducting bulk magnet member using a RE-Ba-Cu-O-based oxide bulk body by a pulse magnetization method to have a strong magnetic field, and the magnetic field is symmetric. In order to obtain a uniform oxide superconducting bulk magnet, the structure of restricting the movement of magnetic flux during pulse magnetization is used to reduce the disturbance of superconducting current in the bulk magnet member. It has been found that the movement of magnetic flux during pulse magnetization can be easily limited by adopting a structure in which a plurality of bulk oxides are arranged in a nested manner. Since no current flows between the oxide bulk bodies arranged in the nest, and the superconducting current flows in each oxide bulk, the disturbance of the superconducting current is reduced. That is, an oxide superconducting bulk magnet having a strong magnetic field and a symmetrically uniform magnetic field can be obtained by the pulse magnetization method.

  As shown in FIG. 1, the oxide superconducting bulk magnet member of the present invention has a structure in which RE-Ba-Cu-O-based oxide bulk bodies are arranged in a nested combination in the form of a plurality of rings. is there. By adopting such a nested arrangement structure, when a strong magnet is formed by the pulse magnetization method, the movement of the magnetic flux can be restricted even by a sudden magnetic field change during the pulse magnetization, and a uniform magnetic field can be obtained with a strong magnetic field. It is done.

  In FIG. 1, RE-Ba-Cu-O-based oxide bulk bodies 1 to 3 having three different ring shapes and one columnar (core) RE-Ba-Cu-O-based oxide bulk. The body 4 is arranged in a nested manner. In such an arrangement structure, a gap 8 is provided between each oxide bulk body, and when pulsed magnetization is performed, the magnetic flux distribution during pulse magnetization is such that the magnetic field distribution in each oxide bulk body becomes uniform and symmetric. Will be limited. This can reduce the disturbance of the superconducting current flowing in the bulk magnet member. Therefore, an oxide superconducting bulk magnet having a strong magnetic field and a uniform magnetic field can be obtained.

  Further, in the present invention, the oxide bulk bodies 1 to 4 in FIG. 1 are continuously connected to each other at at least one joint 9 as shown in FIG. Even if such a seam 9 is provided in the gap 8 between each oxide bulk body, the movement of the magnetic flux during pulse magnetization can be limited, and a strong and uniform magnetic field can be obtained. In addition, by adopting such a configuration, even if there is a centrifugal force or vibration that is received when applied as a magnet of a rotating machine such as a superconducting generator or a superconducting motor, each oxide bulk placed in a nesting state The body will not slip. Moreover, even if pulse magnetization is repeated, each oxide bulk body arranged in the nest does not shift.

The example shown in FIG. 2 is an example in which all the gaps from the outer ring to the core portion are connected by the seam 9, but a combination of those having no part of the seam may be used. For example, the gap from the outer periphery of FIG. 2 to the first ring to the third ring may be connected by a seam, and the core portion may be independent. Moreover, the structure that the clearance gap from a 1st ring-a 2nd ring is connected by the joint, and the 3rd ring and the core part are connected may be sufficient. Further, in the case of being independent as described above, each of the RE-Ba-Cu-O-based oxide bulk bodies 1 to 4 arranged in the nesting may be a combination of the same RE component elements, or RE. A plurality of types of RE-Ba-Cu-O-based oxide bulk bodies having different component elements may be combined and placed in a nested manner. In this case, a RE-Ba-Cu-O-based oxide bulk body having different RE component elements is included. For example, RE is a combination of component elements selected from Sm, Eu, Gd, Dy, Y, and Ho, and the RE is arranged as a RE-Ba-Cu-O-based oxide bulk body in which the component elements of RE are different. Can do. In consideration of the _Jc characteristics of the RE-Ba-Cu-O-based oxide bulk body, by changing the composition of RE, it can be designed to improve the characteristics of the oxide superconducting bulk magnet member as a whole.

  Since the gap 8 and the seam 9 as described above can be formed simply by removing the portion that becomes the gap by a processing method such as sandblasting, electric discharge machining, etching, laser machining, water jet machining, or ultrasonic machining. In addition, simple production that does not require a step of incorporating each oxide bulk body into a nest can be performed.

  Further, the width 10 of the seam 9 only needs to be able to fix each of the oxide bulk bodies. If the width 10 is 0.1 mm or more, sufficient mechanical strength to withstand handling can be obtained. The width 10 of the seam 9 is more preferably 25% or less with respect to the ring circumferential distance of the gap of one ring. When there are a plurality of seams 9 in the gap between one ring, the total width of each seam is more preferably 25% or less. If it exceeds 25%, the current during pulse magnetization tends to flow through the seam, so that it may be difficult to obtain a uniform magnetic field.

  Moreover, although the number of the seams 9 shows an example in which there is one seam in the gap of one ring in FIG. 2, it may be two or more. As the circumferential distance of the ring gap increases, the number of seams is preferably increased. However, from the viewpoint of processing efficiency, if the circumferential distance of the ring gap is 300 mm or less, the number of seams is more preferably 20 or less. If the circumferential distance is 900 mm or less, the number of seams is more preferably 40 or less. Further, the number of nested hierarchical levels is 2 or more in order to adopt a nested structure. In the example shown in FIG. 1, since the oxide bulk bodies 1 to 4 including the core and the ring are arranged in a nested manner, the number of layers is four. The same applies to the example of FIG. Here, the larger the oxide superconducting bulk magnet member, the greater the number. Usually, in order to obtain a more uniform magnetic field with a stronger magnetic field by pulse magnetization, 4 or more is desirable, and 5 or more is desirable.

  The shape of the oxide bulk body arranged in the nest is shown in FIG. 1 and FIG. 2 as an example of a circular shape, but may be any shape having a gap that can restrict the movement of magnetic flux during pulse magnetization for the above reasons. The shape may be appropriately selected so that a desired magnetic field distribution can be obtained as an oxide superconducting bulk magnet suitable for each application. For example, examples of the shape of the oxide bulk body include a polygonal shape such as a triangle, a square, a pentagon, a hexagon, a heptagon, an octagon, a circle, a rectangle, an ellipse, and a racetrack. 3A shows a square shape, FIG. 3B shows a hexagonal shape, FIG. 3C shows a racetrack shape, and the joints are omitted. From the viewpoint of practicality, it is more preferable that at least one of the oxide bulk bodies is a ring having a hexagonal or more polygonal shape to a circle, or a ring having a racetrack shape on the top and bottom surfaces. With such a shape, a more uniform magnetic field can be obtained with a stronger magnetic field.

  Further, the width of the ring of the oxide bulk body is the width along the nesting arrangement direction, and is, for example, the width 5 indicated by the double arrow in the example of FIG. The maximum width of the ring width is preferably 15 mm or less, and more preferably 10 mm or less, because the effect of limiting the movement range of the magnetic flux during pulse magnetization is more easily obtained. On the other hand, when the width of the ring is less than 1 mm, the ratio of the gap to the whole oxide superconducting bulk magnet member is large and the ratio of the oxide bulk body is small, so that the obtained magnetic field is weak. Or the processing yield may be lowered. In relation to the preferable ring width as described above, the relationship with the number of layers of the above-described nested structure is as follows.

  In the case where the width of the ring is equally divided as W, assuming that the maximum size of the oxide superconducting bulk magnet member is L (size 6 of the oxide superconducting bulk magnet member in the example of FIG. 1), the number of layers Since N is N = L / 2W, the upper limit of the preferable range of the number of hierarchies is as follows. For L = 500 mm, N = 500 / (2 × 1) = 250, and for L = 100 mm N = 100 / (2 × 1) = 50.

  The thickness (for example, thickness 7 in FIG. 1) of the oxide superconducting bulk magnet member of the present invention is not particularly limited, and is determined according to the structural design of each application. In view of the ease of performing the pulse magnetizing method, the size is preferably 1/2 or more and 1/100 or less with respect to the size L of the oxide superconducting bulk magnet member. From the viewpoint of maintaining mechanical strength that is easy to handle, the thickness is more preferably 1 mm or more. Further, from the viewpoint of the processing time for processing the gap as shown in FIG. 2, the thickness is desirably 5 mm or less. In particular, in the clearance processing of the nested structure by sandblasting, 3.0 mm or less is more desirable. Moreover, it is more preferable that the gap (for example, the gap 8 in FIG. 1) formed between the oxide bulk bodies arranged in the nest is 0.01 mm or more and 2.00 mm or less from the viewpoint of manufacturing efficiency such as workability. . Moreover, from a viewpoint of magnetic field generation efficiency, 0.45 mm or less is more preferable.

Further, it is more preferable that a plurality of cores and rings of the oxide bulk body are laminated in the rotationally symmetric axis direction. For example, a plurality of oxide superconducting bulk magnet members shown in FIG.
A structure in which these layers are laminated provides a stronger magnetic field. FIG. 4 shows an example in which six layers are stacked. Although FIG. 4 shows an example without a nesting core (hollow example), a stronger magnetic field can be generated more stably with the core as shown in FIG. When there is no core part, when used as a magnet of a rotating machine such as a superconducting generator or a superconducting motor, the hollow inner diameter is 30% or less (in area ratio) with respect to the outer diameter of the superconducting magnet. 9% or less), more preferably 20% or less (4% or less in area ratio), and further preferably 10% or less (1% or less in area ratio).

When stacked in this way, the oxide superconducting bulk magnet as a whole is effective in enhancing the symmetry and uniformity of the magnetic field. Since the oxide bulk body has a high probability of including defects having a low current density in the a-axis direction of the seed crystal at the stage of crystal growth, the a or b axis of the REBa ₂ Cu ₃ O _7-x crystal is It is more desirable to arrange the cores and rings of the stacked oxide bulk bodies to be displaced from the upper and lower adjacent cores and rings to be stacked. This deviation is more preferably 5 ° to 40 °. Accordingly, it is possible to prevent the portions having low characteristics from being arranged, and the characteristics of the entire superconducting bulk magnet can be made uniform. Between the stacked oxide bulk bodies (between the stacked layers) obtains the above-described effect, it may be superconductively bonded or normally conductively bonded.

In the present invention, as described above, the ring is a RE-Ba-Cu-O-based oxide bulk body, that is, an oxide bulk in which the RE ₂ BaCuO ₅ phase is dispersed in the REBa ₂ Cu ₃ O _7-x phase. The superconducting current can flow in the ab plane direction of the REBa ₂ Cu ₃ O _7-x phase in the oxide bulk body, and a stronger magnetic field can be obtained. More preferably, the rotational symmetry axis of the core and ring of each oxide bulk body is within ± 30 ° with respect to the crystallographic c _- axis of the REBa ₂ Cu ₃ O _7-x crystal. More desirably, it is within ± 10 °.

Further, it is more desirable to fit a metal ring on the outermost periphery so that each oxide bulk body is not broken by a hoop force generated by a magnetic field after magnetization. With such a configuration, the coefficient of thermal expansion of the metal ring is different from the coefficient of thermal expansion of the oxide bulk body, so that a compressive stress is applied from the metal ring to the oxide bulk body during cooling, and the probability of cracking by the hoop force. Can be reduced. It is desirable that resin, solder, or grease is filled between the metal ring and the oxide bulk body to apply a compressive stress evenly to the oxide bulk body disposed in the nest. For the same reason, it is desirable to fill the gaps between the oxide bulk bodies arranged in the nesting with resin, grease or solder. Examples of the material of the metal ring include copper, aluminum, and stainless steel. During pulse magnetization, a large shielding current flows in a good conductor, so an alloy material such as stainless steel having a high specific resistance is more desirable. Moreover, when fixing semipermanently with a metal ring, it is desirable to fix with curable resin. In order to make the metal ring removable, it may be fixed with solder or grease. When solder is used, it can be removed by heating to its melting point, and when grease is used, it can be removed at room temperature. More preferably, the rotational symmetry axis of the metal ring coincides with the c _- axis of the REBa ₂ Cu ₃ O _7-x crystal.

The RE-Ba-Cu-O-based oxide bulk used in the present invention is a non-superconducting phase in a single-crystal REBa ₂ Cu ₃ O _7-x phase (123 phase) which is a superconductor phase. A certain RE ₂ BaCuO ₅ phase (211 phase) has a finely dispersed structure. Here, the term “single crystal” means that it is not a perfect single crystal, but also includes those having defects that may be practically used such as a low-angle grain boundary. The reason why it is in a single crystal form (pseudo-single crystal) is that the 211 phase is finely dispersed (for example, about 1 μm) in the 123 phase of the single crystal. RE in the REBa ₂ Cu ₃ O _7-x phase (123 phase) and the RE ₂ BaCuO ₅ phase (211 phase) represents a rare earth element, and Y, La, Nd, Sm, Eu, Gd, Dy, Ho, Er, It is a rare earth element composed of Tm, Yb, Lu, or a combination thereof. In addition, the 123 phase containing La, Nd, Sm, Eu, and Gd is out of the 1: 2: 3 stoichiometric composition, and Ba may be partially substituted at the RE site. It shall be contained in 123 phase. In the 211 phase, which is a non-superconducting phase, La and Nd are somewhat different from Y, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu, and the ratio of metal elements is non-chemical. It is known that the composition is stoichiometric or the crystal structure is different, but this case is also included in the 211 phase of the present invention. Further, _x in the REBa ₂ Cu ₃ O _7-x phase is the amount of oxygen deficiency, and 0 <x ≦ 0.2. This is because when x is in such a range, the REBa ₂ Cu ₃ O _7-x phase exhibits superconductivity as a superconductor.

Substitution of the Ba element described above tends to lower the critical temperature. Further, in an environment having a lower oxygen partial pressure, since substitution of Ba element tends to be suppressed, a 0.1 to 1% oxygen atmosphere in which a small amount of oxygen is mixed in argon or nitrogen rather than in the air. Of these, it is desirable to perform crystal growth. Further, by containing silver in RE-Ba-Cu-O based oxide bulk, tend to mechanical strength and J _c characteristics increases, is desirable from that 5-20 wt% Gan'yuru silver . At this time, the 123 phase deviates from the stoichiometric composition of 1: 2: 3, and there is a case where Ag is partially substituted at the Cu site, but it is included in the 123 phase of the present invention.

The 123 phase is a peritectic reaction between the 211 phase and a liquid phase composed of a complex oxide of Ba and Cu.
211 phase + liquid phase (complex oxide of Ba and Cu) → 123 phase. The temperature at which the 123 phase is formed by this peritectic reaction (Tf: 123 phase formation temperature) is substantially related to the ionic radius of the RE element, and Tf also decreases as the ionic radius decreases. Moreover, Tf tends to decrease with the addition of a low oxygen atmosphere and silver.

An oxide bulk body in which a 211 phase is finely dispersed in a single-crystal 123 phase can be formed because unreacted 211 grains are left in the 123 phase when the 123 phase undergoes crystal growth. That is, the oxide bulk body is
211 phase + liquid phase (compound oxide of Ba and Cu) → 123 phase + 211 phase. The fine dispersion of 211 phase of the oxide bulk body in is very important in terms of J _c improved. By adding a trace amount of at least one of Pt, Rh or Ce, the grain growth of the 211 phase in the semi-molten state (a state consisting of the 211 phase and the liquid phase) is suppressed, and as a result, the 211 phase in the material is reduced to about Refine to 1 μm or less. The addition amount is 0.2 to 2.0 mass% for Pt, 0.01 to 0.5 mass% for Rh, and 0.5 to 2.0 mass for Ce from the viewpoint of the amount of the effect of miniaturization and the material cost. The mass% is desirable. The added Pt, Rh, and Ce partially dissolve in the 123 phase. In addition, elements that could not be dissolved form a composite oxide with Ba and Cu and are scattered in the material.

Further, the oxide bulk body needs to have a high critical current density (J _c ) even in a magnetic field. To satisfy this condition, a single-crystal 123 phase that does not include a large-angle grain boundary that is weakly superconductively coupled is effective. In order to have a higher _Jc characteristic, a pinning center for stopping the movement of magnetic flux is effective. What functions as the pinning center is a finely dispersed 211 phase, and it is desirable that many finely dispersed. In addition, the non-superconducting phase such as the 211 phase has an important function of mechanically strengthening the superconductor by being finely dispersed in the 123 phase that is easy to cleave, and as a bulk material.

211 phase ratio of 123 phase, from the viewpoint of J _c properties and mechanical strength, is desirably 5 to 35% by volume. In addition, the bulk oxide generally contains about 5 to 20% by volume of voids (bubbles) of about 50 to 500 μm. When silver is further added, about 10 to 500 μm of silver or A silver compound is contained more than 0 volume% and 25 volume% or less.

  Moreover, the oxygen deficiency of the oxide bulk body after crystal growth is about 0.5, indicating a temperature change of the semiconductor resistivity. This is annealed in each oxygen atmosphere at 350 ° C. to 600 ° C. for about 100 hours in an oxygen atmosphere, so that oxygen is taken into the material and the amount of oxygen vacancies becomes 0.2 or less, showing good superconducting characteristics.

  Since the oxide superconducting bulk magnet member of the present invention exhibits excellent magnetizing performance capable of generating a desired magnetic field distribution, the oxide superconducting magnet system using the oxide superconducting bulk magnet member is As a whole system, a high magnetic field can be easily generated with a lower energy input, and a system excellent in economic efficiency and environmental harmony can be obtained.

Example 1
Reagents having a purity of 99.9% RE ₂ O ₃ (RE is Gd), BaO ₂ , and CuO have a molar ratio of metal elements of Gd: Ba: Cu of 10:14:20 (ie, 123 phase of the final structure: 211 The phases were mixed so that the molar ratio was 3: 1). Further, a mixed powder to which 0.5% by mass of Pt and 10% by mass of Ag ₂ O were added was prepared. Each mixed powder was temporarily calcined at 890 ° C. for 8 hours. The calcined powder was filled in a cylindrical mold having an inner diameter of 82 mm and formed into a disk shape having a thickness of about 33 mm. In addition, Sm ₂ O ₃ and Yb ₂ O ₃ were used to produce Sm-based and Yb-based disk-shaped molded bodies having a thickness of 4 mm by the same method as the molded body. Furthermore, each molded body was compressed at about 100 MPa by an isotropic isostatic press.

These were stacked on the alumina support material in the order of Sm-based, Yb-based, and Gd-based molded body (precursor) from the bottom and placed in the furnace. These precursors were heated in the atmosphere for 15 hours up to 700 ° C. for 160 hours up to 1040 ° C., further heated up to 1170 ° C. over 1 hour, held for 30 minutes, then cooled down to 1030 ° C. over 1 hour and held for 1 hour. did. In the meantime, an Sm-based seed crystal prepared in advance was used, and the seed crystal was placed on the semi-molten precursor. The orientation of the seed crystal was such that the cleaved surface was placed on the precursor so that the c-axis was the normal line of the disc-shaped precursor. Then, it cooled to 1000-985 degreeC in air | atmosphere over 280 hours, and the crystal was grown. Further, it was cooled to room temperature over about 35 hours to obtain a Gd-based oxide superconducting material having an outer diameter of about 63 mm and a thickness of about 28 mm. Further, two samples (for Sample B and Sample C described later) of the same Gd-based oxide superconducting material were prepared in the same manner. These materials had a structure in which a RE ₂ BaCuO ₅ phase of about 1 μm and silver of 50 to 500 μm were dispersed in the REBa ₂ Cu ₃ O _7-x phase.

Further, from the sample B, as an integrated type that was not sliced as a comparative example and was not processed into a ring shape, it was processed only to an outer diameter of 60.0 mm, an inner diameter of 10.5 mm, and a height of 20.0 mm. After the processing, an oxygen annealing treatment was performed, and the oxide superconducting bulk magnet member was formed by placing it in a stainless steel ring having an outer diameter of 64.0 mm and an inner diameter of 60.1 mm and fixing the stainless steel ring with an epoxy resin .

Next, the sample C, and sliced to a thickness of 1.8mm not a or, to prepare a total of 11 sheets of the wafer-shaped superconductor. All of the obtained wafers had a c-axis within ± 10 ° with respect to the normal line. Then, it was processed into the shape of a seamless 5-ring with an outer diameter of 60 mm by sandblasting. Note that the width W of the superconductor is 4.6 mm, and the gap d is 0.5 mm. Then, to prepare a oxides superconducting bulk magnet member. At this time, since it took time to assemble each ring, the time required for assembling and laminating work was 70 minutes.

Relates concentric oxide superconductor bulk body of an outer diameter 60mm and 10 mm, the number of seams per circle around the vertical width to the axis, the axial thickness, axially laminated sheets, presence or absence of Handa, the c-axis For each oxide superconducting bulk magnet member produced by varying the variation and misalignment of the a-axis, the stacking operation time, peak value during static magnetic field magnetization, distribution uniformity and symmetry, peak value during pulse field magnetization Table 1 below shows the uniformity and symmetry of the distribution, and the ratio of the peak magnetic field after performing 100 times of pulse magnetization with respect to the peak value during the first pulse magnetization.

  From the results of Table 1, the oxide superconducting bulk magnet member composed of oxide bulk bodies arranged in a nested manner with seams is excellent as an oxide superconducting bulk magnet obtained by pulse magnetization. Became clear.

1-3 RE-Ba-Cu-O-based oxide bulk material (ring shape)
4 RE-Ba-Cu-O-based oxide bulk material (core)
5 Ring width 6 Oxide superconducting bulk magnet member size 7 Oxide superconducting bulk magnet member thickness 8 Gap 9 Seam 10 Seam width

Claims (8)

REBa ₂ Cu ₃ O _7-x (RE is a rare earth element or a combination thereof. X is the amount of oxygen deficiency and 0 <x ≦ 0.2.) The RE ₂ BaCuO ₅ phase is dispersed in the phase. An oxide superconducting bulk magnet member combining oxide bulk bodies, wherein the oxide bulk bodies are arranged in a nested manner combining shapes including rings, and adjacent oxide bulks arranged in the nested manner An oxide superconducting bulk magnet member, characterized in that it is connected at one point by a joint connecting the gaps of the bodies, and has solder in the gaps between the oxide bulk bodies .   2. The oxide superconducting bulk according to claim 1, wherein a width of a seam connecting gaps of the oxide bulk body is 0.1 mm or more and 25% or less with respect to a ring circumferential distance of the gaps. Magnet member.   The maximum portion of the width in the direction perpendicular to the rotational symmetry axis of the ring of the oxide bulk body is more than 1.0 mm and not more than 15.0 mm. Oxide superconducting bulk magnet member.   The oxide superconductivity according to any one of claims 1 to 3, wherein a thickness of the ring of the oxide bulk body in a rotational symmetry axis direction is 1.0 mm or more and 5.0 mm or less. Bulk magnet member.   The oxide superconducting bulk magnet member according to any one of claims 1 to 4, wherein the ring of the oxide bulk body is laminated in a rotationally symmetric axis direction. The rotation symmetry axis of the ring of each stacked oxide bulk body is within a range of ± 30 ° with respect to the c _- axis of the REBa ₂ Cu ₃ O _7-x crystal. Oxide superconducting bulk magnet member. The oxide superconducting bulk magnet member according to claim 5 or 6, wherein the a-axis of the REBa ₂ Cu ₃ O _7-x crystal of each of the stacked oxide bulk bodies is shifted. The at least one of the oxide bulk bodies is a ring having a polygonal shape or a circular shape, or a ring having a racetrack shape on an upper surface and a bottom surface, according to any one of claims 1 to 7. The oxide superconducting bulk magnet member as described.

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