JP2020055711A - Oxide superconducting bulk conductor - Google Patents

Abstract

To provide an oxide superconducting bulk conductor using a rare earth oxide superconducting bulk body containing a composition of RE-Ba-Cu-O, which is hardly damaged even when cooled to a critical temperature Tor lower.SOLUTION: The oxide superconducting bulk conductor of the present invention is provided with: an oxide superconducting bulk body of a rod-like or plate-like shape, the bulk body having the structure where an REBaCuOphase is dispersed in a phase having an aligned crystal orientation and a composition of REBaCuO(in which RE is one or more elements selected from the group consisting of Y, La, Nd, Sm, Eu, GD, Dy, Ho, Er, Tm, Yb and Lu, in which 6.8≤y≤7.2); one or more reinforcing members stacked in the longitudinal direction on at least one surface of the oxide superconducting bulk body; and an anti-peeling member fixing the oxide superconducting bulk body to the reinforcing member in the direction where the reinforcing member is superimposed on the oxide superconducting bulk body.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an oxide superconducting bulk conductor using a bulk oxide superconducting body.

Currently, copper is most often used as a conductor for conducting electricity. This is because the resistivity at room temperature is almost the same as that of silver, the lowest as compared with other materials, and it is relatively inexpensive. As a method of lowering the specific resistance of the conductor, there is a method of cooling the conductor. In the case of copper, when cooled to liquid nitrogen temperature (77 K), the specific resistance becomes about 2.5 × 10 ⁻⁹ Ωm, which is about 1/7 of the specific resistance at room temperature. The form of the copper conductor includes a linear or tape-shaped wire, and a plate or rod-shaped bus bar (conductor bar). Copper wires are used for cables, coils of electromagnets, field windings of synchronous motors, and the like. On the other hand, copper busbars are used for branch conductors of switchboards and control boards, conductors of induction motors, and the like. As a conductor for a large-capacity current, a copper bus bar is often more efficient than a copper wire.

Superconductive material, although the need to cool below a critical temperature T _c is an electrical resistance is substantially zero, an ideal conductor. Metal-based superconducting materials, low critical temperature T _c, not led to widespread the need for cooling to cryogenic temperatures. For this reason, when the critical temperature _Tc is as high as the liquid nitrogen temperature or higher and an oxide superconducting material having a relatively small cooling burden is put into practical use, it is expected that the oxide superconducting material will be widely used. As the material form of the oxide superconductor, there are a wire and a bulk bulk. The oxide superconducting wire can be applied to an application field in which a copper wire is used. On the other hand, if a plate-shaped or rod-shaped conductor is cut out from an oxide superconducting bulk material, it can be applied to an application field in which a copper bus bar is used. Here, a conductor using an oxide superconducting bulk material cut into a plate shape or a rod shape from an oxide superconducting bulk material is referred to as an oxide superconducting bulk conductor.

The oxide superconducting bulk material used for the oxide superconductive bulk conductor, high critical temperature T _c, the superconducting bulk material can flow a large current, i.e. critical current density J _c is higher superconducting bulk material is desirable. RE-Ba-Cu-O-based oxide superconductor (RE is one or two selected from the group consisting of Y, La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu. The critical temperature _Tc is as high as about 90K. However, the bulk material of the RE-Ba-Cu-O-based oxide superconductor produced by a sintering method, which is a general oxide production method, is a polycrystalline superconducting bulk material composed of many crystal grains. oxide when superconductive bulk material is polycrystalline, since a large number of grain boundaries existing therein inhibit superconducting current, the critical current density J _c is 1.0 × 10 3 ^{a /} cm ² at 77K Below, which is a low value.

To improve the critical current density J _c, for example, as disclosed in Patent Document 1 below, it is melted crystal growth processes have been developed. By applying such a melt crystal growth process, RE ₁ Ba ₂ Cu ₃ O _{y in which} the crystal orientation is uniform ( _{y in the} formula satisfies 6.8 ≦ y ≦ 7.1). An oxide superconducting bulk material having a structure in which ₂ BaCuO ₅ is finely dispersed can be obtained. The RE ₂ BaCuO ₅ phase finely dispersed therein has a function of pinning lines of magnetic force. Such oxide superconducting bulk material shows in a magnetic field of 1T temperature is 77K, that the critical current density _{J c} is 1.0 × ¹⁰ 4 A / cm ² or more, a high characteristic even in a magnetic field. Here, “having a uniform crystal orientation” has the same meaning as being a single crystal having no large-angle grain boundaries therein.

JP-A-2-153803

  As described above, a conductor such as a copper bus bar can be manufactured by cutting a bulk body into a plate shape or a rod shape from an oxide superconducting bulk material. However, the oxide superconducting material is a brittle material, and there has been a problem that a thin and long cut oxide superconducting bulk is easily broken as it is. Furthermore, even if the oxide superconducting bulk body cut into a long and thin shape is simply integrated with a high-strength member by soldering, resin or the like to form an oxide superconducting bulk conductor, there is a problem of warpage or peeling. In other words, when a high-strength member is bonded and integrated only to one surface of the bulk oxide superconductor to form an oxide superconductor bulk conductor, the heat shrinkage in the longitudinal direction between the bulk oxide superconductor and the high-strength member during cooling is reduced. The difference in the rates causes the bulk of the oxide superconducting body to warp. On the other hand, when a high-strength member is bonded and integrated on both surfaces of the oxide superconducting bulk body to form an oxide superconducting bulk conductor, the warpage due to the difference in heat shrinkage is offset, but the oxide superconducting bulk body and Peeling is likely to occur on the bonding surface between high-strength members. Such a problem of warpage and peeling may be solved by using a high-strength member having the same heat shrinkage as that of the oxide superconducting bulk body, but if it is not a general-purpose member, it becomes expensive and practical. is not.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide RE—Ba—Cu—O (RE is Y, La, Nd, Sm, Eu, Gd, Dy). , Ho, Er, Tm, Yb, and Lu), the critical temperature T of the oxide superconducting bulk conductor using a rare earth-based oxide superconducting bulk material containing a composition of at least one element selected from the group consisting of It is an object of the present invention to provide an oxide superconducting bulk conductor that is hardly damaged even when cooled to _C or less.

The oxide superconducting bulk conductor of the present invention is as follows.
(1) The composition formula is RE ₁ Ba ₂ Cu ₃ O _y (where RE is selected from the group consisting of Y, La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu. One or two or more elements, y satisfies 6.8 ≦ y ≦ 7.2), and in the RE ₁ Ba ₂ Cu ₃ O _y phase having a uniform crystal orientation, An oxide superconducting bulk having a rod-shaped or plate-shaped bulk having a structure in which a RE ₂ BaCuO ₅ phase represented by a composition formula of RE ₂ BaCuO ₅ is dispersed, and at least a longitudinal direction of the oxide superconducting bulk. One or more reinforcing members stacked on one surface, and a separation preventing member that fixes the oxide superconducting bulk member and the reinforcing member in a direction in which the reinforcing member is stacked on the oxide superconducting bulk member. An oxide superconducting bar characterized by the following: Click conductor.
(2) Among the longitudinal surfaces of the oxide superconducting bulk body, a reinforcing member is further provided on the surface on the opposite side to the surface on which the reinforcing member is superimposed, The oxide superconducting bulk conductor according to (1).
(3) The reinforcing member is a metal plate of a good electrical conductor, and the bulk oxide superconductor adhered to the metal plate has a silver coating on a surface thereof. The oxide superconducting bulk conductor according to (1) or (2), wherein the metal superconductor is bonded with a solder or a silver paste.
(4) The bulk oxide superconductor according to any one of (1) to (3), wherein the thickness of the bulk oxide superconductor is 100 μm or more.

According to the present invention can be provided in rare earth-based oxide superconducting bulk conductor having the composition RE-Ba-Cu-O, the damaged hard oxide superconducting bulk conductor be cooled below the critical temperature T _C .

It is a conceptual diagram showing an example of an oxide superconducting bulk conductor concerning an embodiment of the present invention. It is a key map showing another example of an oxide superconducting bulk conductor concerning an embodiment of the present invention. It is a key map showing an example of an exfoliation prevention member in an oxide superconducting bulk conductor concerning one embodiment of the present invention. It is a key map showing an example of an exfoliation prevention member in an oxide superconducting bulk conductor concerning one embodiment of the present invention. It is a key map showing an example of an exfoliation prevention member in an oxide superconducting bulk conductor concerning one embodiment of the present invention. It is a key map showing an example of an exfoliation prevention member in an oxide superconducting bulk conductor concerning one embodiment of the present invention. It is a key map showing an example of an exfoliation prevention member in an oxide superconducting bulk conductor concerning one embodiment of the present invention. It is a key map showing an example of an exfoliation prevention member in an oxide superconducting bulk conductor concerning one embodiment of the present invention. It is a key map showing an example of an exfoliation prevention member in an oxide superconducting bulk conductor concerning one embodiment of the present invention. It is a key map showing the conventional example of bus bar conductor connection. It is a key map showing this example of this embodiment of bus bar conductor connection. It is a key map showing another example of an oxide superconducting bulk conductor concerning an embodiment of the present invention. It is a conceptual diagram which shows another example of the peeling prevention member in the oxide superconducting bulk conductor which concerns on embodiment of this invention. It is a conceptual diagram which shows another example of the peeling prevention member in the oxide superconducting bulk conductor which concerns on embodiment of this invention. It is a key map showing another example of an oxide superconducting bulk conductor concerning an embodiment of the present invention. FIG. 4 is a view showing a measurement result of a trapped magnetic field distribution of a bulk oxide superconducting material in Example 1 of the present invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The ratios and dimensions of the components in the drawings do not represent the actual ratios and dimensions of the components. Further, in this specification and the drawings, a plurality of components having substantially the same function and configuration may be distinguished from each other by adding different alphabets after the same reference numeral. However, when it is not necessary to particularly distinguish each of a plurality of components having substantially the same functional configuration, only the same reference numeral is assigned.

<Overview of superconducting bulk body>
The oxide superconducting bulk body having a uniform crystal orientation (hereinafter, also referred to as “superconducting bulk body”) used in the present embodiment is a RE—Ba—Cu—O-based oxide superconductor. More specifically, the oxide superconducting bulk body having a uniform crystal orientation used in the present embodiment includes a single-crystal RE ₁ Ba ₂ Cu ₃ O _7-x phase (123 phase) and a RE ₂ BaCuO ₅ phase (123 phase). Non-superconducting phase represented by a non-superconducting phase (hereinafter, also referred to as a “QMG material”). In particular, it is desirable that the bulk oxide superconductor according to the present embodiment has a structure in which a non-superconducting phase having a diameter of 20 μm or less is finely dispersed. Here, “having a uniform crystal orientation” means a single crystal state that does not include a large-angle grain boundary, which is a grain boundary at which the superconducting current is significantly reduced. Further, the term “single crystal” does not only indicate a perfect single crystal, but also includes a single crystal having a defect such as a small-angle grain boundary that is inconvenient for practical use. The large angle grain boundary refers to, for example, a grain boundary in which the crystal orientation angle of a region adjacent to the grain boundary is larger than 15 °. In addition, the small-angle grain boundary refers to, for example, a grain boundary in which the crystal orientation angle of a region adjacent to the grain boundary is 15 ° or less. The constituent element RE in the 123 phase and the 211 phase is selected from at least one or more selected from the group consisting of Y and rare earth elements. However, when Ce, Pr, Pm and Tb are contained as a rare earth element, Ce, Pr, Pm and Tb are excluded from the RE because they do not become superconductors. That is, the constituent elements RE in the 123 phase and the 211 phase are selected from rare earth elements including La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu, Y, and combinations of these elements. However, the 123 phase containing at least one of La, Nd, Sm, Eu, and Gd deviates from the stoichiometric composition of 1: 2: 3, and may be in a state in which Ba is partially substituted at the RE site. is there. Also, 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-stoichiometric. It is known that they have stoichiometric compositions or have different crystal structures.

  The aforementioned substitution of Ba element tends to lower the critical temperature. In an environment having a lower oxygen partial pressure, the substitution of Ba element tends to be suppressed.

  Such a single crystal oxide superconducting bulk body is not formed by sintering, which is a general method for producing ceramics, but is formed by raising the formed body to a melting temperature higher than the sintering temperature as described in detail below. It is manufactured by a molten crystal growth method in which after heating to a semi-molten state, crystals are grown during slow cooling.

The 123 phase is generated by a peritectic reaction between the 211 phase and a liquid phase composed of a composite oxide of Ba and Cu as described below.
211 phase + liquid phase (composite 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 the Tf also decreases as the ionic radius of the RE element decreases. Further, Tf tends to decrease with a low oxygen atmosphere and the addition of Ag.

The material in which the 211 phase is finely dispersed in the single crystal 123 phase is formed because unreacted 211 grains are left in the 123 phase when the 123 phase grows. That is, the bulk material is generated by the following reaction.
211 phase + liquid phase (composite oxide of Ba and Cu) → 123 phase + 211 phase

Fine dispersion of QMG 211 phase in the material, in view of the critical current density J _c improved, is extremely important. The QMG material may contain a trace amount of at least one of Pt, Rh and Ce in addition to the above-mentioned constituent elements. By containing at least one of Pt, Rh or Ce in a trace amount, the grain growth of the 211 phase in a semi-molten state (ie, a state composed of the 211 phase and the liquid phase) is suppressed, and as a result, the QMG material The grain size of the 211 phase in the inside can be reduced to about 1 μm. It is preferable that the content of these elements is contained in such an amount that a miniaturization effect appears. From the viewpoint of material cost, the content of these elements is, for example, 0.2 to 2.0% by mass of Pt, 0.01 to 0.5% by mass of Rh, and 0.5 to 100% of Ce, respectively. Preferably it is 2.0% by mass. More preferably, the content of Pt is 0.4 to 0.8% by mass, the content of Rh is 0.05 to 0.4% by mass, and the content of Ce is 0.1 to 0.3%. % By mass. When a plurality of Pt, Rh or Ce is used, the total amount of Pt, Rh or Ce contained is preferably 0.1% by mass or more based on the mass of the oxide superconducting bulk material. 0 mass% or less, more preferably 0.2 mass% or more and 1.5 mass% or less. Pt, Rh and Ce contained in the QMG material partially dissolve in the 123 phase. Further, of Pt, Rh, and Ce contained in the QMG material, a residue that could not form a solid solution forms a composite oxide with Ba and Cu, and is scattered throughout the material. The QMG material has a four-fold rotationally symmetric crystal structure as a whole bulk body.

Here, 211 phase ratio of 123 phase, from the viewpoint of properties and mechanical strength of the critical current density _{J c,} for example, it is desirable that 5 to 35% by volume. More preferably, the content is 15% by volume or more and 30% by volume or less. Further, it is general that a void (bubble) of about 50 to 500 μm exists in about 5 to 20% by volume in the superconducting bulk body. Further, it is possible to further add Ag to the superconducting bulk body in addition to the above elements. When Ag is further added, the superconducting bulk body contains more than 0% by volume to 25% by volume or less of Ag or an Ag compound having a particle size of about 1 to 500 μm depending on the amount of Ag added.

  Further, the bulk body after crystal growth exhibits a temperature change in resistivity as a semiconductor or an insulating material when the oxygen deficiency (x) is about 0.5 to 0.8. By annealing the bulk body after such crystal growth in an oxygen atmosphere at a temperature of 623 K to 873 K for about 100 hours in accordance with each RE system, oxygen is taken into the superconducting bulk body, and the amount of oxygen deficiency ( x) is 0.2 or less, that is, the amount of oxygen y (= 7−x) is 6.8 or more, indicating good superconducting properties. At this time, a twin structure is generated in the superconducting phase. However, such a twin structure is also referred to as “single crystal” in this specification.

  Further, in order to utilize such an oxide superconducting bulk body as an oxide superconducting bulk conductor, the oxide superconducting bulk body after crystal growth is processed into a predetermined shape such as a rod shape or a plate shape, and then, as described above. It is required to perform oxygen annealing of the bulk oxide superconductor.

<Detailed description of oxide superconducting bulk conductor according to this embodiment>
Hereinafter, an oxide superconducting bulk conductor according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a conceptual diagram illustrating an example of the oxide superconducting bulk conductor according to the present embodiment. The oxide superconducting bulk conductor 1 according to the present embodiment has a composition formula of RE ₁ Ba ₂ Cu ₃ O _y (where RE is Y, La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm. , Yb, and Lu, one or more elements selected from the group consisting of 6.8 ≦ y ≦ 7.2), and in the RE ₁ Ba ₂ Cu ₃ O _y phase having a uniform crystal orientation. , 1 on at least one side of the longitudinal (x-axis direction) of the _RE 2 BaCuO oxide phase was cut into elongated plate-like or rod from dispersed organizations ₅ bulk superconductor 10 the composition formula of _RE 2 BaCuO ₅ The above reinforcing members 20 are arranged in an overlapping manner. The oxide superconducting bulk body 10 used for the oxide superconducting bulk conductor 1 is not particularly limited in cross-sectional shape as long as it is cut into an elongated plate or rod shape, but the cross-sectional shape is rectangular or square. The shape is preferable because it can be easily overlapped with the reinforcing member 20. Furthermore, the oxide superconducting bulk conductor 1 is provided with a separation preventing member 30 for fixing the oxide superconducting bulk body 10 and the reinforcing member 20 in the overlapping direction (z-axis direction). That is, the separation preventing member 30 fixes the oxide superconducting bulk body 10 and the reinforcing member 20 in a direction perpendicular to the surface on which the reinforcing member 20 is stacked. The peeling prevention member 30 has a ring surrounding the stacked body in which the bulk oxide superconducting body 10 and the reinforcing member 20 are stacked. Then, the laminate is fitted into the hollow portion of the peeling prevention member 30. Although the oxide superconducting bulk body 10 has a brittle material and an elongated shape, it is hardly broken because both sides are fixed by the peeling prevention member 30 together with the high-strength reinforcing member 20 laminated on at least one surface. Furthermore, the separation preventing member 30 fixes the oxide superconducting bulk body 10 and the reinforcing member 20 in the overlapping direction, but does not fix it in the longitudinal direction. Even if the heat shrinkage in the longitudinal direction of 20 differs, the bulk of the oxide superconducting body 10 and the reinforcing member 20 are slightly displaced from each other in the longitudinal direction at the time of cooling, and warpage or peeling is unlikely to occur. Here, the thickness of oxide superconducting bulk body 10 used for oxide superconducting bulk conductor 1 is preferably at least 100 μm. As the conductor of the oxide superconducting material, there is also a superconducting tape wire formed by forming the same material on a tape-shaped metal substrate, but the thickness of the superconducting portion is about 1 μm. Since the thickness of the portion is completely different from the thickness of the bulk oxide superconducting body 10, its properties and behavior are also greatly different. Also, it is difficult to cut a conductor thinner than 100 μm from the bulk oxide superconductor 10, which is different from an oxide superconducting tape wire formed on a metal substrate from the beginning.

  FIG. 2 is a conceptual diagram showing another example of the oxide superconducting bulk conductor according to the present embodiment. In FIG. 2, reinforcing members 20 are arranged on both surfaces of the bulk oxide superconductor body 10 facing each other in the longitudinal direction. Furthermore, the oxide superconducting bulk conductor 1A is provided with an anti-peeling member 30 for fixing the oxide superconducting bulk body 10 and the reinforcing member 20 in the overlapping direction. The oxide superconducting bulk body 10 is fixed to both sides by the high-strength reinforcing member 20 and the peel-prevention member 30 irrespective of the brittle material and elongated shape, so that it is less likely to be damaged than in the case of single-sided reinforcement. Furthermore, the peeling prevention member 30 fixes the oxide superconducting bulk body 10 and the reinforcing member 20 in the overlapping direction, but does not fix it in the longitudinal direction. Even if the heat shrinkage in the longitudinal direction of 20 differs, the bulk of the oxide superconducting body 10 and the reinforcing member 20 are slightly displaced from each other in the longitudinal direction at the time of cooling, and warpage or peeling is unlikely to occur.

  The reinforcing member 20 may be a metal such as copper, a copper alloy, aluminum, or an aluminum alloy, or a mechanically high-strength member such as glass fiber reinforced plastic (GFRP) or carbon fiber reinforced plastic (CFRP). The oxide superconducting bulk body 10 is fixed by the high-strength reinforcing member 20 and the separation preventing member 30 irrespective of the brittle material and elongated shape, so that it is not easily broken. Furthermore, the separation preventing member 30 fixes the oxide superconducting bulk body 10 and the reinforcing member 20 in the overlapping direction, but does not fix it in the longitudinal direction. Even if the heat shrinkage in the longitudinal direction of the oxide superconducting bulk 20 differs, the bulk of the oxide superconducting bulk 10 and the reinforcing member 20 are slightly displaced from each other in the longitudinal direction at the time of cooling. Is not damaged. There is no restriction on the thickness of the reinforcing member 20, but if it is too thin, the effect of reinforcing is reduced, so the thickness of the reinforcing member 20 is preferably 0.5 mm or more. If the thickness is too large, the conductor becomes bulky, so the thickness of the reinforcing member 20 is preferably equal to or less than twice the thickness of the bulk oxide superconducting body 10.

In the description of FIGS. 1 and 2, an example has been given so far in which the oxide superconducting bulk body 10 and the reinforcing member 20 are not particularly adhered but are fixed only by the peeling preventing member 30. The bulk of the oxide superconducting body 10 and the reinforcing member 20 may be integrated by bonding with solder, resin, or the like. As shown in FIG. 1, when the reinforcing member 20 is stacked only on one side of the bulk oxide superconducting body 10 and the bulk superconducting oxide body 10 and the reinforcing member 20 are bonded and integrated, no displacement occurs between them. In addition, warpage during cooling due to a difference in thermal shrinkage between the bulk oxide superconducting body 10 and the reinforcing member 20 cannot be prevented even by fixing with the peeling preventing member 30. However, peeling due to warpage between the bulk oxide superconductor 10 and the reinforcing member 20 can be prevented. As shown in FIG. 2, when the reinforcing members 20 are stacked on both sides of the oxide superconducting bulk body 10 and the oxide superconducting bulk body 10 and the reinforcing member 20 are bonded and integrated, the two members may be shifted from each other. Even without this, warpage during cooling due to the difference in thermal shrinkage between the oxide superconducting bulk body 10 and the reinforcing member 20 is unlikely to occur, and conversely, peeling between the oxide superconducting bulk body 10 and the reinforcing member 20 tends to occur. However, since the bulk oxide superconducting body 10 and the reinforcing member 20 are fixed in the overlapping direction by the separation preventing member 30, separation can be effectively prevented. Further, when the reinforcing member 20 is made of a good conductor of electricity such as copper or aluminum and is bonded and integrated with the oxide superconducting bulk body 10 by soldering, silver paste, or the like, the electrical connection between the oxide superconducting bulk body 10 and the reinforcing member 20 becomes electric. Connected. Thus, even if the oxide superconducting bulk body 10 is broken, the reinforcing member 20, which is a good conductor of electricity, has a current bypass function. As a result, even when the bulk oxide superconducting body 10 is damaged, the bulk superconducting oxide conductor according to the present embodiment does not completely lose its function as a conductor. Therefore, the effect of increasing the function of protecting equipment connected to the oxide superconducting bulk conductor is obtained. When soldering between the bulk oxide superconducting body 10 and the reinforcing member 20, it is preferable to provide a silver coating on the surface of the bulk oxide superconducting body 10 because the electrical contact resistance is significantly reduced. Here, a good conductor of electricity has a similar electrical resistivity to copper or aluminum, and preferably has a resistivity of 1 × 10 ⁻⁷ Ωm or less near room temperature.

  As the separation preventing member 30, any member may be used as long as it fixes the oxide superconducting bulk body 10 and the reinforcing member 20 in the overlapping direction, and the forming method and shape are not limited. FIGS. 3 to 9 show examples of the separation preventing member viewed from the longitudinal direction of the oxide superconducting bulk conductor provided with the reinforcing members on both sides. FIG. 3 shows an example in which the peeling prevention member is integrally molded. FIG. 4 shows an example in which components of a plurality of peeling prevention members are combined to form a hollow structure. Compared to the case where the oxide superconducting bulk body 10 and the reinforcing member 20 are fitted into the integral hollow structure separation preventing member 30 shown in FIG. 3, as shown in FIG. The combined structure including the member component 301 and the peel preventing member component 302 facilitates fitting. In the case of combining a plurality of peel preventing member parts, for example, as shown in FIG. 5, for example, the peel preventing member part 301 and the peel preventing member part 302 may be fixed by bolts 303 to form a peel preventing member 30B, or As shown in FIG. 6, it may be bonded with an adhesive 304 such as solder or resin. FIG. 7 shows an example in which the peel preventing member 30C has a U-shaped structure. That is, the peel preventing member 30C has a structure in which a part of the ring is omitted. In the case of the U-shaped exfoliation prevention member 30C, the oxide superconducting bulk body 10 and the reinforcing member 20 are disengaged from the exfoliation prevention member 30C by fitting the exfoliation prevention members 30C adjacent to each other in the longitudinal direction in opposite directions. Can be difficult. The separation preventing member 30D shown in FIG. 8 is an example in which a weir 306 is provided on a separation preventing member 305 having a U-shaped structure so that the bulk oxide superconducting body 10 and the reinforcing member 20 do not easily come off from the separation preventing member 30D. FIG. 9 shows an example in which a thin tape-shaped peeling prevention member 307 is wound.

  The thermal contraction rate of the peeling prevention member 30 is the same as or larger than the overall thermal contraction rate in the direction in which the bulk oxide superconducting body 10 and the reinforcing member 20 are overlapped. A compressive stress acts on the reinforcing member 10 and the reinforcing member 20 to increase the fixing force, which is preferable. Although there is no limitation on the number of separation preventing members 30 in one oxide superconducting bulk conductor 1, for example, as shown in FIG. It is preferable to provide a total of two locations, one at each end. When the length of the stacked body to be one oxide superconducting bulk conductor is long, the number may be appropriately increased, for example, by providing a peel prevention member 30 at the center. The peel prevention member 30 may be a metal such as copper, copper alloy, aluminum, or aluminum alloy, or a mechanically high-strength member such as glass fiber reinforced plastic (GFRP) or carbon fiber reinforced plastic (CFRP). On the other hand, in the case of a tape-shaped peeling prevention member, even a thin metal or resin tape can be made to have high strength by forming a multilayer winding. The peel preventing member 30 may be bonded to the oxide superconducting bulk body 10 or the reinforcing member 20 with solder, resin, or the like. However, when the oxide superconducting bulk body 10 and the reinforcing member 20 are not bonded to each other, When fixing to either the longitudinal surface of the oxide superconducting bulk body 10 or the longitudinal surface of the reinforcing member 20 alone, the oxide superconducting bulk body 10 and the reinforcing member 20 may be displaced from each other during cooling. It is preferable because it becomes possible.

  Next, referring to FIGS. 10 and 11, a conventional example of busbar conductor connection and an example of the present invention will be compared. FIG. 10 shows a case where a copper terminal A and a copper terminal B are connected by a conventional copper busbar conductor 2. FIG. 11 shows a case where the copper terminal A and the copper terminal B are connected by the oxide superconducting bulk conductor 1 according to the present invention. In both cases, the copper terminal A and the copper terminal B are electrically connected by soldering or the like, but in the case of the oxide superconducting bulk conductor 1 according to the present invention, for example, the oxide superconducting bulk body 10 The copper terminal A and the copper terminal B are soldered. In this case, the peel prevention member 30 is attached at a position avoiding the soldering surface. As compared with the case where the copper terminal A and the copper terminal B are connected by the conventional copper busbar conductor 2 of FIG. 10, the copper terminal A and the copper terminal B are connected by the oxide superconducting bulk conductor 1 as in the present invention of FIG. When tied, the electrical resistance of the oxide superconducting bulk conductor 1 is smaller than the electrical resistance of the copper busbar conductor 2, so that when the same current flows, it is possible to make the whole compact. Joule heat generation during energization is greatly reduced.

  FIG. 12 is a conceptual diagram showing another example of the oxide superconducting bulk conductor according to the present embodiment. In FIG. 12, the reinforcing members are superposed and arranged on both surfaces facing each other in the longitudinal direction of the oxide superconducting bulk conductor 1 </ b> E. However, unlike the example of FIG. 2, the reinforcing member 20 </ b> A on one side is shorter. With this structure, as shown in FIG. 11, when the copper terminals at points A and B are connected by the oxide superconducting bulk conductor 1E, the copper terminals at points A and B are connected to the oxide superconducting conductor. The bulk body 10 can be directly soldered. In FIG. 12, the reinforcing member 20A on one side is shortened, and one surface of the end portion of the oxide superconducting bulk body 10 can be directly connected to an external terminal. The structure may be such that both ends of the bulk material superconducting body 10 can be directly connected to external terminals. Further, even in the case of the oxide superconducting bulk conductor 1A in which the reinforcing members 20 on both sides have the same length as shown in FIG. 2, the reinforcing member 20 is a good electric conductor, and If the reinforcing member 20 is electrically connected with solder or the like, the oxide superconducting bulk conductor 1 </ b> A may be connected to the copper terminals at the points A and B via the reinforcing member 20.

  FIG. 13 is a conceptual diagram showing another example of the oxide superconducting bulk conductor 1 according to the present embodiment. In FIG. 13, a recess is provided in a part of the bulk oxide superconducting body 10 </ b> A and the reinforcing member 20 </ b> B in accordance with the size of the peel preventing member 30, and by fitting the peel preventing member 30 into the recess, The structure is such that the peel prevention member 30 does not protrude. In FIG. 14, the length of the reinforcing member 20C is shorter than that of the bulk oxide superconducting body 10, and a U-shaped peeling prevention member 30D is provided at the end of the bulk of the oxide superconducting body 10. It does not protrude. Even in the case where the peeling prevention member 30D has a U-shape as shown in FIG. 14, the reinforcing member 20C and the peeling prevention member 30D have a structure in which the reinforcing member 20C partially overlaps. Peeling from the oxide superconducting bulk body 10 can be prevented.

FIG. 15 is a conceptual diagram showing another example of the oxide superconducting bulk conductor according to the present embodiment. In FIG. 15, one reinforcing member 20 is placed on each side of each of the plurality of oxide superconducting bulk bodies 10 in the Z-axis direction, and is fixed by the plurality of separation preventing members 30. The length of the practical oxide superconducting bulk conductor 1H is about several centimeters to 1 m, and the reinforcing member 30 such as copper or FRP (fiber reinforced plastic) can be manufactured industrially as a single unit. Meanwhile, the oxide bulk superconductor 10 with high critical current density J _c, to be produced by the crystal growth process, the length is about 10 cm, in order to long oxide superconductive bulk conductor. 1H Therefore, a plurality of bulk oxide superconducting bodies 10 will be used. In that case, as shown in FIG. 15, it is preferable to provide at least one exfoliation preventing member 30 in each oxide superconducting bulk body 10 because it is sufficiently fixed.

  As above, various examples of the oxide superconducting bulk conductor according to the embodiment of the present invention have been described.

  The oxide superconducting bulk conductor according to the present embodiment is not limited to the examples shown in FIGS. In other words, the oxide superconducting bulk body, the reinforcing member is placed on at least one surface in the longitudinal direction of the oxide superconducting bulk body, is provided, provided with a peeling prevention member that fixes the oxide superconducting bulk body and the reinforcing member in the overlapping direction The form of the oxide superconducting bulk conductor is not particularly limited as long as the oxide superconducting bulk conductor is used.

  Hereinafter, embodiments of the present invention will be specifically described with reference to examples. The embodiments described below are merely examples of the present invention, and the present invention is not limited to the following examples.

(Example 1)
Example In this example, the effectiveness of the oxide superconducting bulk conductor according to the present embodiment will be described with reference to FIG. FIG. 16A shows an oxide superconducting bulk conductor having only a rod-shaped oxide superconducting bulk body without a reinforcing member. FIG. 16B shows an oxide superconducting bulk conductor provided with a reinforcing member on one side, and FIG. 16C shows an oxide superconducting bulk conductor provided with a reinforcing member on one side. 16 (b) and 16 (c), since there is no separation preventing member, the oxide superconducting bulk body and the reinforcing member are integrated by soldering. FIG. 16D shows an oxide superconducting bulk conductor in which a one-side reinforcing member is provided with a peel-off preventing member, and FIG. 16E shows an oxide superconducting bulk conductor in which both-side reinforcing members are provided with a peel-off preventing member. In both figures, the bulk superconducting oxide body and the reinforcing member are not integrated because of the presence of the separation preventing member. Here, the oxide superconducting bulk conductor shown in FIG. 16A is sample A, the oxide superconducting bulk conductor shown in FIG. 16B is sample B, and the oxide superconducting bulk conductor shown in FIG. Is referred to as Sample C, the oxide superconducting bulk conductor illustrated in FIG. 16D is referred to as Sample D, and the oxide superconducting bulk conductor illustrated in FIG.

  First, a method for manufacturing a bulk oxide superconducting body, which is a base material from which rod-shaped bulk oxide superconducting bodies constituting Samples A to E are cut, will be described. A commercially available powder of each oxide of gadolinium (Gd), barium (Ba), and copper (Cu) having a purity of 99.9% by mass was obtained by adding Gd: Ba: Cu = 1.6: 2.3: 3. The mixture was weighed at a molar ratio of 3, and 1% by mass of cerium oxide and 10% by mass of silver oxide in terms of silver were added thereto. The weighed powder was sufficiently kneaded for 2 hours, and then calcined in the atmosphere at 1173K for 8 hours. Next, the calcined powder was formed into a disk shape using a mold. The molded body is heated to 1423K to be in a molten state, held for 30 minutes, seeded in the course of cooling, and gradually cooled in a temperature region of 1278K to 1252K over 100 hours to grow a crystal, and has a diameter of 60 mm and a height of 60 mm. A 20 mm single crystal oxide superconducting bulk body was obtained. Then, an elongated rod-shaped sample having a length of 50 mm, a width of 3 mm and a thickness of 1 mm was cut out from the single-crystal oxide superconducting bulk material having a diameter of 60 mm so that the c-axis of the crystal became parallel to the 1-mm long side. . The elongated rod-shaped sample was formed by depositing silver on the surface to a thickness of about 2 μm and then heat-treated at 673 K for 100 hours in an oxygen stream.

  For sample A, this elongated rod-shaped sample was used as an oxide superconducting bulk conductor. For sample B, a copper plate having a length of 50 mm, a width of 3 mm, and a thickness of 1 mm was adhered to one side of the bulk oxide superconductor by soldering as a reinforcing member. For sample C, a copper plate having a length of 50 mm, a width of 3 mm, and a thickness of 1 mm was bonded to both sides of the bulk oxide superconductor by soldering as a reinforcing member. For sample D, a copper plate as a reinforcing member was superimposed on one side of the bulk oxide superconducting body, and fitted to two copper peel preventing members having a hollow size of 3 mm × 2 mm. For sample E, a copper plate superposed on both sides of the bulk oxide superconducting body as a reinforcing member was fitted to two copper peel preventing members having a hollow size of 3 mm × 3 mm. As described above, in Samples D and E, the bulk oxide superconductor and the reinforcing member are not integrated (not bonded) because of the presence of the separation preventing member. Further, in the present embodiment, the separation preventing members are merely fitted, and no particular bonding is performed.

  Five samples A to E were prepared, and a cooling test from room temperature to liquid nitrogen temperature was repeated 10 times. For sample A, one out of five pieces was damaged during the handling of the cooling repetition test. However, for samples B to E having the reinforcing member, the oxide superconducting bulk conductor was damaged during the handling of the cooling repetition test. Did not. Sample B was warped during cooling due to the difference in the thermal shrinkage in the longitudinal direction between the bulk oxide superconductor and the reinforcing member during cooling. In the first cooling, no peeling was observed because the entire sample was warped, but after cooling was repeated 10 times, peeling occurred between the oxide superconducting bulk body and the reinforcing member in 4 out of 5 samples. . For sample C, there was no warping of the entire sample, but after the first cooling, exfoliation occurred between two of the five bulk oxide superconductors and the reinforcing member. After the fifth cooling, peeling occurred in all five samples, and the degree of peeling increased as cooling was repeated. With respect to Sample D, no warping or peeling of the entire sample occurred even after cooling, and there was no particular abnormality even after cooling 10 times. Regarding the sample E, the entire sample did not warp or peel even when cooled, and there was no particular abnormality even after cooling 10 times.

Therefore, from this result, the oxide superconducting bulk conductor, the reinforcing member is placed on at least one surface in the longitudinal direction of the oxide superconducting bulk body, and oxidized in the direction in which the oxide superconducting bulk body and the reinforcing member overlap. by the arrangement comprises a peeling preventing member for fixing the object superconducting bulk body and the reinforcing member, in the rare earth-based oxide superconducting bulk conductor comprising the composition of RE-Ba-Cu-O, below the critical temperature T _C An oxide superconducting bulk conductor that is not easily damaged even when cooled can be provided.

  As described above, the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to such examples. It is apparent that those skilled in the art to which the present invention pertains can conceive various changes or modifications within the scope of the technical idea described in the claims. It is understood that these also belong to the technical scope of the present invention.

1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H Oxide superconducting bulk conductor 2 Copper bus bar 10, 10A Oxide superconducting bulk
20, 20A, 20B, 20C Reinforcement member 30, 30A, 30B, 30C, 30D, 305, 307 Peeling prevention member 301, 302 Peeling prevention member part 303 Bolt 304 Adhesive 306 Weir

Claims (4)

The composition formula is RE ₁ Ba ₂ Cu ₃ O _y (where RE is one selected from the group consisting of Y, La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu. Or two or more elements, and y satisfies 6.8 ≦ y ≦ 7.2), and the composition formula is expressed in the RE ₁ Ba ₂ Cu ₃ O _y phase having a uniform crystal orientation. and has a structure _{in which RE} 2 BaCuO ₅ phase represented by RE ₂ BaCuO ₅ are dispersed, and the oxide superconductive bulk body having a rod-like or plate-like shape,
One or more reinforcing members stacked on at least one surface in the longitudinal direction of the bulk oxide superconductor,
An oxide superconducting bulk conductor, comprising: a direction in which the reinforcing member is superimposed on the oxide superconducting bulk body, and a separation preventing member that fixes the oxide superconducting bulk body and the reinforcing member. .   2. The longitudinal direction surface of the oxide superconducting bulk body, further comprising a reinforcing member disposed on the surface opposite to the surface on which the reinforcing member is superimposed. 3. 3. The oxide superconducting bulk conductor according to claim 1. The reinforcing member is a metal plate of a good electrical conductor,
The oxide superconducting bulk body bonded to the metal plate has a silver coating on its surface,
The oxide superconducting bulk conductor according to claim 1, wherein the oxide superconducting bulk body and the metal plate are adhered with solder or silver paste.   The bulk oxide superconducting conductor according to any one of claims 1 to 3, wherein a thickness of the bulk oxide superconducting body is 100 µm or more.

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