JP5597516B2 - Superconducting wire manufacturing method - Google Patents

Description

  The present invention relates to a method of manufacturing a superconducting wire and a superconducting wire, and is suitable for use in technologies applied to devices such as energy storage, transformers, motors, and generators.

  A superconductor such as a Y-based oxide superconductor is maintained in a superconducting state within a condition range defined by a critical temperature, a critical current, and a critical magnetic field. Depending on the usage conditions of the superconductor, heat may be generated when a part of the superconductor is in a normal conducting state, which may cause a quench phenomenon in which the entire superconductor transitions to the normal conducting state. Will burn out. Therefore, in order to prevent burning due to the quench phenomenon of the superconductor, generally, a superconductor is combined with a stabilizer made of a highly conductive metal, and a part of the superconductor is in a normal conducting state during energization. In such a case, the superconductor is stabilized by adopting a configuration that allows a current to flow through the stabilizing material.

  As a method for compounding the stabilizing layer, a method of forming an Ag stabilizing layer by physical vapor deposition such as sputtering or vapor deposition as in Patent Document 1 or a low cost on a deposited Ag stabilizing layer as in Patent Document 2 For example, there is a method of bonding a Cu material with solder.

  When these superconducting wires are used for energy storage, transformers, motors, generators, and other applied equipment, AC loss may occur. For this reason, it has been reported that AC loss can be reduced by thinning a wire to make it a parallel conductor (see Patent Document 3 and Non-Patent Document 1).

JP 2006-236652 A JP 2008-060074 A JP 2007-141688 A

Supercond. Soc. Technol. 20 822-826 (2007)

  In order to reduce the AC loss, it is necessary to make the wire thin and to make it a parallel conductor. For example, in the case of a superconducting cable, the AC loss can be reduced by arranging the wire rod so as to have a shape close to a circle with respect to the cylindrical core member around which the wire rod is wound. In order to efficiently produce a wire, it is required to form a superconductor film on a wide tape material and cut it according to the application, but when the produced superconducting wire is cut, the superconducting layer at the cut surface Will be exposed.

  For this reason, in the exposed state, the crystal structure of the superconducting layer, which is weak against moisture, is disturbed due to the influence of moisture in the atmosphere and the influence of moisture generated when returning from liquid nitrogen temperature to room temperature, resulting in reduced performance. There is a problem of end.

  The present invention has been made in view of such a conventional situation, and an object of the present invention is to provide a method of manufacturing a superconducting wire and a superconducting wire that can reduce AC loss and at the same time prevent deterioration in performance due to moisture. And

In order to solve the above-described problems, a method for producing a superconducting wire according to the present invention is a superconducting wire comprising at least an intermediate layer, a cap layer, an oxide superconducting layer, and a protective layer above a metal substrate. A manufacturing method comprising:
A step of forming an intermediate layer, a step of forming a cap layer, and a step of forming an oxide superconducting layer for forming an oxide superconducting layer on the metal substrate having a predetermined initial width dimension,
A groove forming step for forming a groove for dividing at least the oxide superconducting layer in the width direction of the wire in the longitudinal direction of the wire ;
A protective layer forming step of forming a protective layer so as to cover at least the surface of the oxide superconducting layer;
Cutting in the longitudinal direction of the wire at the cutting position set in the groove, and forming a thin superconducting wire having a width smaller than the initial width,
The aspect ratio of the depth dimension and the width dimension of the groove formed in the groove forming step; (groove depth) / (groove width) is set to 1 or less, and the width dimension of the groove is 20 μm to 1000 μm. set in the range of,
In the cutting step, the protective layer is laminated on the surface of the oxide superconducting layer on the three sides that do not contact the cap layer in the wire cross-sectional direction, and the thickness of the protective layer is generally 1 μm or more in a layer shape The thin superconducting wire is formed as follows.
In the present invention, the depth dimension of the groove formed in the groove forming step may be set in a range of 1 μm to 50 μm.
In the present invention, the depth of the groove formed in the groove forming step can reach the metal base material.
The present invention, the thickness of the protective layer formed in the protective layer forming step is preferably set in a range of 5μ m ~100μm.
According to the present invention, in the cutting step, at least a cutting width dimension for cutting the metal substrate is set to be equal to or smaller than a difference between the width dimension of the groove and twice the thickness of the protective layer. be able to.
The present invention can include a step of laminating a stabilizing layer having good electrical conductivity on the protective layer.
The present invention, the superconducting wire, on a metal substrate, an intermediate layer formed by crystal orientation trimmed, and a cap layer crystal orientation trimmed undergo crystal orientation of the effect of the intermediate layer, It is possible to be a superconducting wire comprising at least an oxide superconducting layer whose crystal orientation is adjusted under the influence of the crystal orientation of the cap layer and a protective layer having good conductivity.

The method for producing a superconducting wire of the present invention includes forming a groove, laminating a protective layer in the groove and the oxide superconducting layer, and cutting the groove inside the groove, so that the protective layer is formed on the upper surface of the oxide superconducting layer and Thinning is possible in a state of being laminated on both side surfaces in the width direction. As a result, it is possible to provide a superconducting wire that is thinned so that the influence of moisture can be efficiently reduced and AC loss can be reduced .

The schematic block diagram which shows an example of the superconducting wire which concerns on this invention. The schematic block diagram which shows an example of the film-forming apparatus for manufacturing the superconducting wire. The flowchart which shows an example of the manufacturing method of the superconducting wire which concerns on this invention. Sectional drawing which shows the process in an example of the manufacturing method of the superconducting wire which concerns on this invention. The flowchart which shows the other example of the manufacturing method of the superconducting wire which concerns on this invention. Sectional drawing which shows the further another example of the manufacturing method of the superconducting wire which concerns on this invention.

Hereinafter, the superconducting wire and the manufacturing method thereof according to the present invention will be described.
FIG. 1 is a schematic perspective view schematically showing an example of a superconducting wire according to the present invention.
A superconducting wire A shown in FIG. 1 is formed on a tape-like base material 10 on a diffusion preventing layer 11, a bed layer 12, an intermediate layer 15, a cap layer 16, an oxide superconducting layer 17, a protective layer 30 and a stabilizing layer ( It is configured as a laminate in which conductive layers 18 are laminated in this order. In the superconducting wire A, the bed layer 12 can be omitted.

In the superconducting wire A of this embodiment, the protective layer 30 extends on the side surface of the laminate so as to cover at least the side surface of the oxide superconducting layer 17. Specifically, the protective layer 30 includes an upper surface and a side surface of the oxide superconducting layer 17 and a cap layer 16 located below the oxide superconducting layer 17 from the upper position to the lower position of the stacked body. The side surface, the side surface of the intermediate layer 15, the side surface of the bed layer 12, and the side surface of the diffusion prevention layer 11 are provided so as to extend from the upper surface of the oxide superconducting layer 17 to the side surface.
Further, in the superconducting wire A, the protective layer 30 is formed from the upper end position of the oxide superconducting layer 17 from the upper side to the lower side of the stacked body, from the oxide superconducting layer 17, the cap layer 16, the intermediate layer 15, and the bed layer. 12, the diffusion preventing layer 11 and the base material 10 may be provided so as to cover all side surfaces. Further, the protective film 30 covers all side surfaces on one side surface in the cross-sectional direction, and on the other side surface. The protective film 30 can cover the side surface excluding the base material 10 so that only the base material 10 is exposed on the side surface.

  The superconducting wire A of this embodiment has a widthwise dimension TA shown in FIG. 1 of 1 mm to 5 mm in order to reduce AC loss when applied to devices such as energy storage, transformers, motors, and generators. It is set to a range of about, and preferably set to a range of about 2.0 mm to 5.0 mm.

If the superconducting wire A has a width-direction dimension that is larger than the upper limit of the above range, thinning is insufficient and AC loss is not sufficiently reduced, and it can be applied to devices such as energy storage, transformers, motors, and generators. When doing so, the size of the device becomes large. If the value is smaller than the lower limit of the above range, an oxide superconducting layer having necessary characteristics cannot be formed, or the number of times of cutting increases, and the rate of critical current deterioration due to superconducting layer breakdown around the cutting increases. This is not preferable.

  The base material (metal base material) 10 applicable to the superconducting wire A of the present embodiment can be used as a base material of a normal superconducting wire, has only to be high strength, and is in a tape shape to make a long cable. It is preferable to use a heat-resistant metal. Examples thereof include various metal materials such as nickel alloys such as silver, platinum, stainless steel, copper, Hastelloy (trade name manufactured by Haynes, USA), or ceramics disposed on these various metal materials. Among various heat resistant metals, nickel alloys are preferable. Especially, if it is a commercial item, Hastelloy is suitable, and any kind of Hastelloy B, C, G, N, W, etc. which have different amounts of components such as molybdenum, chromium, iron and cobalt can be used as Hastelloy. . What is necessary is just to adjust the thickness of the base material 10 suitably according to the objective, and it is 10-500 micrometers normally. The value of the surface roughness Ra of the substrate 10 is set to be 10 nm or less.

The diffusion prevention layer 11 is formed for the purpose of preventing the constituent elements of the base material 10 from diffusing, and silicon nitride (Si ₃ N ₄ ), aluminum oxide (Al ₂ O ₃ ), GZO (Gd ₂ Zr ₂ O _7). Etc.) or rare earth metal oxides.

The bed layer 12 has high heat resistance and is intended to reduce interfacial reactivity, and is used to obtain the orientation of a film disposed thereon. Such a bed layer 12 is disposed as necessary. For example, among rare earth oxides such as yttria (Y ₂ O ₃ ), the composition formula (α ₁ O ₂ ) _2x (β ₂ O ₃ ) _{(1- x 2)} , Er ₂ O ₃ , CeO ₂ , Dy ₂ O ₃ , Er ₂ O ₃ , Eu ₂ O ₃ , Ho ₂ O ₃ , La ₂ O _3, etc. Si ₃ N ₄ ), aluminum oxide (Al ₂ O ₃ , also called “alumina”), and the like.

Thus, by interposing the diffusion preventing layer 11 between the base material 10 and the bed layer 12, when forming other layers such as an intermediate layer 15, a cap layer 16 and an oxide superconducting layer 17 described later, In order to suppress diffusion of a part of the constituent elements of the base material 10 to the oxide superconducting layer 17 side through the bed layer 12 when receiving a thermal history as a result of being necessarily heated or heat-treated. In addition, by adopting a two-layer structure of the diffusion prevention layer and the bed layer 12, element diffusion from the substrate 10 side can be effectively suppressed. As an example in the case of interposing a diffusion preventing layer between the base material 10 and the bed layer 12, a combination using Al ₂ O ₃ as the diffusion preventing layer 11 and Y ₂ O ₃ as the bed layer 12 can be exemplified. .

The intermediate layer 15 may have either a single layer structure or a multilayer structure, and is selected from materials that are biaxially oriented in order to control the crystal orientation of the oxide superconducting layer 17 laminated thereon. Specifically, preferred materials for the intermediate layer 15 are Gd ₂ Zr ₂ O ₇ , MgO, ZrO ₂ —Y ₂ O ₃ (YSZ), SrTiO ₃ , CeO ₂ , Y ₂ O ₃ , Al ₂ O 3, Gd ₂ O. ₃ , metal oxides such as Zr ₂ O ₃ , Ho ₂ O ₃ and Nd ₂ O ₃ can be exemplified.

The cap layer 16 is formed through a process of epitaxial growth on the surface of the intermediate layer 15, and then grain growth (overgrowth) in the lateral direction (plane direction), and crystal grains are selectively grown in the in-plane direction. Are preferred. Such a cap layer 16 has a higher in-plane orientation degree than the intermediate layer 15 made of the metal oxide layer.
The material of the cap layer 16 is not particularly limited as long as it can exhibit the above functions, but specific examples of preferable materials include CeO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , Gd ₂ O ₃ , and Zr _2. Examples thereof include O ₃ , Ho ₂ O ₃ and Nd ₂ O ₃ . When the material of the cap layer is CeO ₂ , the cap layer 16 may include a Ce—M—O-based oxide in which part of Ce is substituted with another metal atom or metal ion.

The CeO ₂ layer as the cap layer 16 can be formed by a PLD method (pulse laser vapor deposition method), a sputtering method, or the like, but it is desirable to use the PLD method in terms of obtaining a high film formation rate. The film formation conditions for the CeO ₂ layer by the PLD method can be performed in an oxygen gas atmosphere at a substrate temperature of about 500 to 1000 ° C. and about 0.6 to 100 Pa.
The film thickness of the CeO ₂ layer may be 50 nm or more, but is preferably 100 nm or more, and more preferably 500 nm or more in order to obtain sufficient orientation. However, if it is too thick, the crystal orientation deteriorates.

The oxide superconducting layer 17 may be a known one, and specifically, a material made of REBa ₂ Cu ₃ O _y (RE represents a rare earth element such as Y, La, Nd, Sm, Er, Gd) is exemplified. it can. Examples of the oxide superconducting layer 17 include Y123 (YBa ₂ Cu ₃ O _7-X ) or Gd123 (GdBa ₂ Cu ₃ O _7-X ). Further, other oxide superconductors, for _{example, Bi 2 Sr 2 Ca n-} 1 Cu n for _{O 4 + 2n + δ} becomes may be used in compositions such as those made of other oxide superconductors having high critical temperatures representative Of course.
The oxide superconducting layer 17 has a thickness of about 0.5 to 5 μm and preferably a uniform thickness.

  The oxide superconducting layer 17 is laminated by a physical vapor deposition method such as sputtering, vacuum vapor deposition, laser vapor deposition, electron beam vapor deposition, chemical vapor deposition (CVD), or coating pyrolysis (MOD). In particular, from the viewpoint of productivity, it is preferable to use a PLD method, a TFA-MOD method (an organic metal deposition method using a trifluoroacetate salt, a coating pyrolysis method), or a CVD method.

  Here, as described above, when the oxide superconducting layer 17 is formed on the cap layer 16 having a good orientation, the oxide superconducting layer 17 laminated on the cap layer 16 also matches the orientation of the cap layer 16. Crystallize as follows. Therefore, the oxide superconducting layer 17 formed on the cap layer 16 is hardly disturbed in crystal orientation, and the thickness of the base material 10 is determined for each crystal grain constituting the oxide superconducting layer 17. The c-axis that hardly allows electricity to flow is oriented, and the a-axis or the b-axis is oriented in the length direction of the substrate 10. Therefore, the obtained oxide superconducting layer 17 is excellent in quantum connectivity at the crystal grain boundary, and hardly deteriorates in the superconducting characteristics at the crystal grain boundary. High critical current density can be obtained.

  The protective layer 30 laminated on the oxide superconducting layer 17 is formed as a layer made of a metal material having good conductivity, such as Ag, and a low contact resistance with the oxide superconducting layer 17. Further, a layer of a highly conductive metal material such as Cu is laminated as a stabilizing layer 18, and the oxide superconducting layer 17 is always in a superconducting state as a laminated structure in which the protective layer 30 and the stabilizing layer 18 are combined. It is possible to function as a bypass through which the current of the oxide superconducting layer 17 commutates when attempting to transition to the conductive state. In addition, the protective layer 30 continuously extends to the side surface of the oxide superconducting layer 17 as described above.

  Then, an insulating layer formed by winding a tape of an insulating material such as polyimide (not shown) covering the entire periphery of these laminates is formed, and an oxide superconducting wire with an insulating coating can be obtained.

FIG. 3 is a flowchart showing an example of a method for manufacturing a superconducting wire according to the present invention.
As shown in FIG. 3, the manufacturing method of the superconducting wire A of this embodiment includes a base material preparation step S01, a diffusion prevention layer formation step S02, a bed layer formation step S03, an intermediate layer formation step S04, and a cap layer. It includes a forming step S05, an oxide superconducting layer forming step S06, a groove forming step S07, a protective layer forming step S08, a cutting step S09, and a stabilizing layer forming step S10.

FIG. 4 is a cross-sectional view showing some steps in the method of manufacturing a superconducting wire according to the present invention.
In the base material preparation step S01 shown in FIG. 3, as described above, a Ni heat resistant substrate represented by Hastelloy as a heat resistant alloy in which Mo, Cr, W, Co or the like is added to the Ni base is prepared as the base material 10. However, at this time, a wire rod having a desired size and shape is obtained by rolling (cold / hot) processing, etc., and at the same time, surface flattening and rolling traces, scratches, and lattice defects are removed as much as possible. It is preferable. For this reason, the surface is made as smooth as possible by a plurality of rolling processes and mechanical polishing.

  In the substrate preparation step S01, as shown in FIG. 4 (a), the number of times of the width dimension TA of the wire A to be manufactured and the width dimension TM of a groove (cutting groove) M to be described later are calculated from this number. A base material 10 having a width dimension T0 that is a sum of multiples obtained by subtracting 1 is prepared. That is, the width T0 of the base material 10 to be prepared is a value obtained by subtracting the groove width TM from the product of the number of fine wires to be manufactured by cutting to the sum of the width dimension TA of the wire A and the width dimension TM of the groove M. . In this embodiment, three thinned oxide superconducting wires A, A, A ′ are manufactured from one substrate 10 prepared in the substrate preparation step S01, that is, the number of wires is 3. This is exemplified.

  In the diffusion preventing layer forming step S02 shown in FIG. 3, since the crystallinity is not questioned, the diffusion preventing layer 11 is formed on the substrate 10 by a film forming method such as a normal sputtering method. At this time, the thickness of the diffusion preventing layer 11 is set to be, for example, 10 to 400 nm. When the thickness of the diffusion preventing layer 12 is less than 10 nm, there is a possibility that the diffusion of the constituent elements of the substrate 10 cannot be sufficiently prevented. On the other hand, when the thickness of the diffusion preventing layer 11 exceeds 400 nm, the internal stress of the diffusion preventing layer 11 increases, and there is a possibility that the whole including the other layers is easily peeled off from the base material 10.

  In the bed layer forming step S03 shown in FIG. 3, the bed layer 12 is formed by a film forming method such as a sputtering method, and the thickness thereof is, for example, 10 to 200 nm.

In the intermediate layer forming step S04 shown in FIG. 3, the intermediate layer 15 is formed by sputtering, vacuum vapor deposition, laser vapor deposition, electron beam vapor deposition, ion beam assisted vapor deposition (hereinafter abbreviated as IBAD method), chemical vapor phase. It can be laminated by a known method such as a physical vapor deposition method such as a growth method (CVD method); a coating pyrolysis method (MOD method); thermal spraying or the like. The intermediate layer 15 is formed with a good crystal orientation (for example, a crystal orientation degree of 15 ° or less) by an ion beam assisted deposition method (IBAD method). As a result, the crystal orientation of the cap layer 16 formed thereon can be set to a good value (for example, a crystal orientation degree of about 5 °), whereby the oxide superconducting layer 17 formed on the cap layer 16 is formed. Therefore, it is possible to exhibit excellent superconducting characteristics with good crystal orientation.
The thickness of the intermediate layer 15 may be appropriately adjusted according to the purpose, but can usually be in the range of 5 to 300 nm.

The IBAD method is a method of orienting crystal axes by irradiating an ion beam at a predetermined angle with respect to an underlying vapor deposition surface during vapor deposition. Usually, an argon (Ar) ion beam is used as the ion beam. For example, the intermediate layer 15 made of Gd ₂ Zr ₂ O ₇ , MgO, or ZrO ₂ —Y ₂ O ₃ (YSZ) reduces the value of ΔΦ (FWHM: full width at half maximum), which is an index representing the degree of crystal orientation in the IBAD method. This is particularly preferable because it can be performed.

As shown in FIG. 2, the ion beam assisted sputtering apparatus 20 in the case of manufacturing the intermediate layer 15 has a target 22 disposed so as to face a film forming region 21 where a tape-shaped substrate or the like is disposed. The sputter ion source source 23 is disposed so as to face the diagonal direction with respect to the assist ion source source so as to face the normal line of the film forming region 21 at a predetermined angle (for example, 45 °) from the diagonal direction. 25 is arranged and configured.
The ion beam assisted sputtering apparatus 20 of this example is a film forming apparatus provided in a form accommodated in a vacuum chamber, and includes a first roll 28 and a second roll 29 on which a tape-like base material 27 is disposed oppositely. A structure in which the film is reciprocally wound a plurality of times and reciprocated in the film formation region 21 can be exemplified.
The ion source sources 23 and 25 applied in this embodiment are configured to include an extraction electrode, a filament, and an introduction tube for Ar gas or the like inside the container, and irradiate ions parallel to the beam from the tip of the container. It can be done.

The vacuum chamber used in the present embodiment is a container that partitions the outside and the film formation space, has airtightness, and has pressure resistance because the inside is in a high vacuum state. The vacuum chamber is connected to a gas supply means for introducing a carrier gas and a reactive gas into the vacuum chamber and an exhaust means for exhausting the gas in the vacuum chamber. In the figure, the supply means and the exhaust means are omitted. Only the arrangement relationship of each device is shown.
The target 12 used here can be a target having a composition suitable for forming the intermediate layer 15 of the above-described material.
By using the ion beam assisted sputtering apparatus 20 having the structure shown in FIG. 2, the IBAD method can be realized and the target intermediate layer 15 can be formed.

In the cap layer forming step S05 shown in FIG. 3, the cap layer 16 made of, for example, CeO _{2 is formed} to a thickness of 500 to 1000 nm by the PLD method (pulse laser deposition method).

In the oxide superconducting layer forming step S06 shown in FIG. 3, physical vapor deposition methods such as sputtering, vacuum vapor deposition, laser vapor deposition, electron beam vapor deposition, chemical vapor deposition (CVD); coating pyrolysis From the viewpoint of productivity, such as (MOD method), the oxide superconducting layer 17 is formed by PLD method, TFA-MOD method (organic metal deposition method using trifluoroacetate, coating pyrolysis method), or CVD method. A film is formed.
The stacked body S having the width T0 shown in FIG. 4A is formed by the steps up to the oxide superconducting layer forming step S06.

  In the groove forming step S07 shown in FIG. 3, in the stacked body S formed by the steps up to the oxide superconducting layer forming step S06, on the upper surface where the oxide superconducting layer 17 exists, as shown in FIG. A groove (cutting groove) M extending in the longitudinal direction of the wire is formed so as to divide at least the oxide superconducting layer in the width direction of the wire. In the example shown in FIG. 4B of the present embodiment, two grooves M are formed by a laser or a rotating blade, but the present invention is not limited to this.

In the groove forming step S07, the aspect ratio of the depth dimension TMb and the width dimension TM of the groove M to be formed; TMb / TM = (groove depth) / (groove width) is set to 1 or less, The width dimension TM of the groove M is preferably set in the range of 20 μm to 1000 μm.
The depth dimension TMb of the groove M is set in a range of 1 μm to 50 μm, and in this embodiment, the depth reaches the surface of the base material 10, but at least a position deeper than the oxide superconducting layer 17 is formed. What is necessary is just to form deeper than the minimum depth dimension, and what is necessary is just to be formed shallower than the maximum depth dimension which is the state which does not cut | disconnect the base material 10, What kind of depth is in this range? But it doesn't matter.
Here, the sufficient thickness of the protective film 30 is set to a thickness that can sufficiently block moisture from the outside that adversely affects the oxide superconducting layer 17.
By setting the width dimension TM of the groove M in the above range, the protective film 30 having a sufficient thickness is formed inside the groove M when the protective film 30 is formed by sputtering in the next protective layer forming step S08. And the oxide superconducting layer 17 can be sufficiently covered.

In the protective layer forming step S08 shown in FIG. 3, the protective layer 30 made of a metal material having a good conductivity, such as Ag, and a low contact resistance with the oxide superconducting layer 17, is made to have a thickness of about 10 μm by sputtering or the like. It is formed. Thereafter, in the protective layer forming step S08, the oxide superconducting layer 17 is subjected to heat treatment for supplying oxygen. The heat treatment conditions are set to 500 to 800 ° C. in an oxygen atmosphere for several tens of hours to several hundreds of hours.
As shown in FIG. 4C, the protective layer 30 is laminated on the surface of the oxide superconducting layer 17. At the same time, the protective layer 30 is also formed on the outer side surface of the stacked body S and the inner side surface of the groove M. .
In this protective layer forming step S08, the thickness T30 of the protective layer laminated on the upper surface of the oxide superconducting layer 17 is set in the range of 5 μm to 100 μm as shown in FIG. The thickness T30a of the protective layer formed on the inner surface of the groove M is set in the range of 5 to 100 μm as shown in FIG. At this time, the width dimension TM of the groove M shown in FIG. 4B and the thickness T30a of the protective layer 30 on the inner surface of the groove M are as follows:
TM ≧ 2 × T30a
The dimension T30b between the protective films 30 in the groove M is set so that

In the cutting step S09 shown in FIG. 3, as shown in FIG. 4D, the thickness dimension (from the width dimension TM of the groove M is smaller than twice the width dimension T30a of the protective layer 30 in the groove M ( Cutting with a laser or a rotating blade so as to obtain a cutting allowance having a width dimension (TC) of the groove M.
This cutting margin TC is set to 10 to 990 μm, and is set so that the protective layer 30 remains sufficiently on the side surface of the superconducting wire A after cutting.
In the cutting step S09, that is, at least the cutting width dimension TC for cutting the substrate 10 is set to be equal to or smaller than the difference between the width dimension TM of the groove M and twice the thickness T30a of the protective layer 30. . That means
TC ≤ TM-2 × T30a
The cutting width dimension TC is set so that

In the width dimension TM of the above-mentioned groove M, the reason why the lower limit of TM is 20 μm is that the limit of the cutting width when cutting this type of superconducting conductor is 10 μm, and the thickness T30a of the protective layer 30 is 5 μm at the minimum. This is because it is desirable to set 20 μm as the lower limit from the relationship of “{(TC) + 2 × (T30a)} ≦ (TM)”. In addition, the upper limit is set to 1000 μm, but if it exceeds this value, it cannot be said that there will be a problem of cutting. However, since the area of the portion to be removed by cutting as a superconducting layer increases, waste is increased. is there.
The maximum thickness of the oxide superconducting layer 17 having a good crystal orientation that can be formed by the film formation method is about 10 μm, and therefore, “(thickness of oxide superconducting layer) <(groove width TM) is always present. Is established. Since there is a relationship of “{(TC) + 2 × (T30a)} ≦ (TM)”, the range of the depth dimension TMb of the groove M also changes as the thickness of the protective film 30 changes. Therefore, it is preferable to satisfy “(thickness of oxide superconducting layer) <(groove width TM)”.
The thickness T30 of the protective layer described above is in the range of 5 μm to 100 μm. The protective layer 30 having a thickness of less than 5 μm tends to be difficult to serve as a protective layer, and the thickness exceeding 100 μm is particularly advantageous in terms of characteristics. Although this does not cause a problem, it is preferable to set the thickness to 100 μm or less in view of cost because the protective layer 30 is wasted.

In the stabilizing layer forming step S10 shown in FIG. 3, a stabilizing layer 18 made of a metal material having good conductivity, such as Ag, and a low contact resistance with the oxide superconducting layer 17 is formed.
In this embodiment, the base material 10 is exposed only on one side surface, but on the opposite side surface, the two superconducting wires A are thinned in which a protective film 30 is provided on the side surface of the base material 10, and the superconducting wire A It was possible to manufacture one superconducting wire A ′ having the oxide superconducting layer 17 having the same width dimension TA as the base material 10 exposed on both sides.

In the superconducting wire A of the present embodiment, the laminated body S is provided on the base material 10 and a groove M for dividing the oxide superconducting layer 17 is provided on the surface thereof, thereby thinning the three superconducting wires A, A, A. 'You can get. Thereby, the oxide superconducting layer 17 is protected by the protective layer 30 made of Ag, and the oxide superconducting layer can be prevented from being exposed.
In this embodiment, the stabilization layer 18 that becomes the conductive layer after cutting is provided. However, as shown in FIG. 5, after the protective layer formation step S08, Cu is formed by the stabilization layer formation step S19. Then, it is also possible to perform a cutting process as cutting process S20.

  Examples of the present invention will be described below based on the embodiments, but the present invention is not limited to the following examples.

<Experimental example 1>
An intermediate layer made of Gd ₂ Zr ₂ O _{7 having a} thickness of 1 μm is formed on the surface of a Hastelloy tape substrate having a thickness of 100 μm and a width of 10 mm by the IBAD method, and the thickness is formed on the IBAD intermediate layer by the PLD method. A 0.5 μm CeO ₂ film and an intermediate layer (cap layer) are formed, and an oxide superconducting layer made of GdBCO (GdBa ₂ Cu ₃ O _7-X ) having a thickness of 1 μm is formed thereon by the PLD method. A laminate of superconducting wires having a cross-sectional structure as shown in FIG.
Thereafter, a groove having a width of 100 μm as shown in FIG. 4B was formed by a laser scribing method at a central portion of the Hastelloy tape having a width of 10 mm (a position 5 mm from the end). The groove was formed over the entire length in the longitudinal direction, and the depth of the groove reached the surface of the Hastelloy tape substrate.
Next, Ag, which is a protective layer, is coated by sputtering to a thickness of 10 μm, and a heat treatment step (oxygen annealing) is performed at 500 ° C. for 10 hours (FIG. 2C), and two YAG lasers are formed along the groove portion. Disconnected. As a result, two superconducting wires A shown in FIG. 6 corresponding to the structure shown in FIG.

<Experimental example 2>
The process up to the heat treatment step for the protective layer was performed by the same method as in (Experimental Example 1) (see FIG. 4C).
Thereafter, a stabilizing layer made of Cu, which is a metal laminate layer, was coated by 100 μm by sputtering. At this time, since it is sufficient to add Cu only to the upper part of the Ag layer, it is not always necessary to add it to the side surface of the Ag layer.
Finally, it cut | disconnected in two with the YAG laser along the groove part. Thereby, the superconducting layer after cutting was covered with Ag, and two superconducting wires with a Cu stabilizing layer were prepared.

<Experimental example 3>
Until the oxide superconducting layer was formed, the oxide superconducting layer was produced by the same method as in Experimental Example 1 (see FIG. 4A). Thereafter, grooves having a width of 100 μm as shown in FIG. 4B were formed by laser scribing at positions 3.3 mm from both ends of the Hastelloy tape having a width of 10 mm. The groove was provided over the entire length in the longitudinal direction, and the depth of the groove reached the surface of the Hastelloy tape substrate.
Next, a protective layer of Ag was coated by a sputtering method to a thickness of 10 μm and subjected to a heat treatment step (FIG. 4C), and cut into three along the groove portion by a YAG laser (FIG. 4D). As a result, as shown in FIG. 4 (e), three superconducting wires A, A, A ′ in which the entire superconducting layer after cutting was covered with Ag were produced.

<Experimental Examples 4 to 15>
In the same manner as in Experimental Example 1, two superconducting wires A were prepared. At this time, when forming the groove, the width dimension and the depth dimension were changed. The results are shown in Tables 1 and 2.

In these experimental examples, the covering state of the laminate of the protective layer located inside the groove was visually observed. As a result of visual observation, an experimental example where it was confirmed that the protective layer was generally 1 μm or more in a layered form was indicated by a mark “◯”, and an experimental example not attached was indicated by a mark “X”. In these experimental examples, the sample was placed in an atmosphere of room temperature and 50% humidity for 1 hour, then cooled with liquid nitrogen, and Ic measurement was performed. The voltage at both ends was 1 μV / cm ² . In addition, when the protective layer does not adhere to the inside of the groove as much as 1 μm or more, there is a possibility that Ic may be lowered.
The results are shown in the table.

From these results, it is desirable that the aspect ratio between the depth dimension and the width dimension of the groove is set in the above range.
Note that, when the results of Examples 13, 14, and 15 are seen, if the protective layer is left about 1 μm on one side, the characteristic does not deteriorate. However, if the protective layer is cut to be less than 1 μm, the characteristic is deteriorated. If the protective layer is scraped off, no problem will occur if a thickness of about 1 μm is left. This is considered to be desirable in order to absorb an error in positioning accuracy because there are problems such as positioning accuracy of the laser to be irradiated.

  A, A '... superconducting wire, 10 ... base material, 12 ... bed layer, 15 ... intermediate layer, 16 ... cap layer, 17 ... oxide superconducting layer (superconducting layer), 30 ... protective layer, 18 ... stabilization layer, M ... groove.

Claims (7)

A method for producing a superconducting wire comprising an intermediate layer, a cap layer, an oxide superconducting layer, and a protective layer provided above a metal substrate,
A step of forming an intermediate layer, a step of forming a cap layer, and a step of forming an oxide superconducting layer for forming an oxide superconducting layer on the metal substrate having a predetermined initial width dimension,
A groove forming step for forming a groove for dividing at least the oxide superconducting layer in the width direction of the wire in the longitudinal direction of the wire ;
A protective layer forming step of forming a protective layer so as to cover at least the surface of the oxide superconducting layer;
And a cutting step of forming the cut the wire length side direction in the set cut position in the groove, thin line of superconducting wire initially a smaller width dimension than the width dimension,
The aspect ratio of the depth dimension and the width dimension of the groove formed in the groove forming step; (groove depth) / (groove width) is set to 1 or less, and the width dimension of the groove is 20 μm to 1000 μm. set in the range of,
In the cutting step, the protective layer is laminated on the surface of the oxide superconducting layer on the three sides that do not contact the cap layer in the wire cross-sectional direction, and the thickness of the protective layer is generally 1 μm or more in a layer shape A method for producing a superconducting wire, comprising forming the superconducting wire of the thin wire .   The method for producing a superconducting wire according to claim 1, wherein a depth dimension of the groove formed in the groove forming step is set in a range of 1 µm to 50 µm. The method for producing a superconducting wire according to claim 1 or 2, wherein the depth of the groove formed in the groove forming step reaches the metal base material. The thickness of the protective layer formed in the protective layer forming step method of manufacturing a superconducting wire according to any one of claims 1 to 3, characterized in that it is set in the range of 5μ m ~100μm. In the cutting step, at least a cutting width dimension for cutting the metal substrate is set to be equal to or smaller than a difference between the width dimension of the groove and twice the thickness of the protective layer. The manufacturing method of the superconducting wire of any one of Claim 1 to 4 . The method for producing a superconducting wire according to any one of claims 1 to 5, further comprising a step of laminating a stabilizing layer having good electrical conductivity on the protective layer. The superconducting wire has an intermediate layer on which a crystal orientation is arranged on a metal substrate, a cap layer in which the crystal orientation is arranged under the influence of the crystal orientation of the intermediate layer, and the cap layer and the crystal orientation of the affected by crystal orientation oxide superconducting layer that has been trimmed from claim 1 and a protective layer is characterized by a superconducting wire comprising provided at least with a good electrical conductivity 6 The manufacturing method of the superconducting wire of any one of Claims 1 .

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