TITLE OF INVENTION
Substrate, Method of Producing Substrate, Superconducting Wire, and Method
of Producing Superconducting Wire
TECHNICAL FIELD
The present invention relates to a substrate, a method of producing a substrate, a
superconducting wire, and a method of producing a superconducting wire.
BACKGROUND ART
Since the discovery of high-temperature superconductors, development in hightemperature
superconducting wire is carried out actively in view of the application to
power apparatus such as a cable, magnet, current-limiting device, and the like. The
high-temperature superconducting wire is roughly classified into two types, i.e. a
bismuth type silver sheath wire and a RE 123 type thin film wire (RE = rare earth
element).
The RE 123 type thin film superconducting wire has raised hopes for a hightemperature
superconducting wire of the next generation based on the advantages of:
(1) the critical current density at the liquid nitrogen temperature (77.3K) exhibits the
performance of approximately lO^A/cm^ that is two orders of magnitude greater as
compared with the bismuth type silver sheath wire; and (2) the critical current density
under magnetic field is high.
As a general structure of a thin film superconducting wire, a thin intermediate
layer of ceramic is formed on a metal substrate, and a superconducting layer is formed
thereon. In order to draw out superior superconducting properties for a thin film
superconducting wire, the crystal orientation of the superconducting layer must be
arranged in three dimensions. To this end, a thin film having high orientation must be
produced for the aforementioned thin film intermediate layer.
Japanese Patent Laying-Open No. 2005-1935 (Patent Literature 1) discloses a
method including the steps of removing an oxide layer located on the surface of an
oriented metal substrate, and epitaxial growth of a thin film such as an intermediate
2
layer and a superconducting layer while maintaining the biaxial orientation of the
oriented metal substrate.
CITATION LIST
PATENT LITERATURE
PTL 1: Japanese Patent Laying-Open No. 2005-1935
SUMMARY OF INVENTION
TECHNICAL PROBLEM
When a superconducting wire is produced using a ferromagnetic body such as
Ni for an oriented metal substrate, as disclosed in Patent Literature 1, and current is
conducted to the obtained superconducting wire, there was a problem that the saturation
magnetization of the substrate is great and the AC loss caused by hysteresis loss is
increased.
Therefore, an object of the present invention is to provide a substrate that allows
the AC loss of a superconducting wire to be reduced, a method of producing a substrate,
a superconducting wire, and a method of producing a superconducting wire.
SOLUTION TO PROBLEM
A substrate of the present invention includes a copper layer, an alloy layer
containing copper and nickel, formed on the copper layer, a nickel layer formed on the
alloy layer, and an intermediate layer formed on the nickel layer. The concentration of
nickel in the alloy layer at the interface between the alloy layer and the nickel layer is
greater than the concentration of nickel in the alloy layer at the interface between the
alloy layer and the copper layer.
Preferably in the substrate of the present invention, the concentration of nickel
in the alloy layer is monotonically decreased from the interface between the alloy layer
and the nickel layer towards the interface between the alloy layer and the copper layer.
A method of producing a substrate of the present invention includes the steps of:
preparing a substrate having a nickel layer formed on a copper layer through plating,
alloying a portion of the nickel layer while leaving a remaining portion of the nickel
layer; and epitaxial-growing an intermediate layer on the nickel layer after the step of
alloying the nickel layer.
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A superconducting wire of the present invention includes a copper layer, an
alloy layer containing copper and nickel, formed on the copper layer, a nickel layer
formed on the alloy layer, an intermediate layer formed on the nickel layer, and a
superconducting layer formed on the intermediate layer. The concentration of nickel
in the alloy layer at the interface between the alloy layer and the nickel layer is greater
than the concentration of nickel in the alloy layer at the interface between the alloy layer
and the copper layer.
Preferably in the superconducting wire of the present invention, the
concentration of nickel in the alloy layer is monotonically decreased from the interface
between the alloy layer and the nickel layer towards the interface between the alloy
layer and the copper layer.
A method of producing a superconducting wire of the present invention includes
the steps of: preparing a substrate having a nickel layer formed on a copper layer
through plating, alloying a portion of the nickel layer while leaving a remaining portion
of the nickel layer; epitaxial-growing an intermediate layer on the nickel layer after the
step of alloying the nickel layer, and forming a superconducting layer on the
intermediate layer.
According to a substrate, a method of producing a substrate, a superconducting
wire, and a method of producing a superconducting wire of the present invention, some
of the nickel in the substrate is alloyed to be rendered non-magnetic. Accordingly, the
hysteresis loss at the substrate is decreased, allowing the AC loss of the
superconducting wire to be reduced.
Preferably in the method of producing a substrate of the present invention, the
step of alloying the nickel layer is carried out under reduced pressure absent of
hydrogen gas.
Preferably in the method of producing a superconducting wire of the present
invention, the step of alloying the nickel layer is carried out under reduced pressure
absent of hydrogen gas.
By carrying out the step of alloying the nickel layer under reduced pressure
absent of hydrogen gas, the oxide layer at the Ni surface is left until just before
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formation of the intermediate layer, and reduced during formation of the intermediate
layer. Accordingly, Ni having favorable matching lattice with the intermediate layer is
exposed at the surface while H2O is present in the proximity of the substrate.
Therefore, oxygen loss of the metal oxide that is the intermediate layer can be
prevented to facilitate orientation.
ADVANTAGEOUS EFFECT OF INVENTION
According to the present invention, a substrate and a superconducting wire that
can reduce AC loss of the superconducting wire can be obtained.
BRIEF DESCRIPTION OF DRAWINGS
Fig. 1 is a schematic sectional view of a substrate according to an embodiment
of the present invention.
Fig. 2 is a schematic sectional view of a superconducting wire according to an
embodiment of the present invention.
Fig. 3 is a schematic sectional view to describe a method of producing a
substrate and a superconducting wire according to an embodiment of the present
invention.
Fig. 4 is a graph representing the nickel concentration in an alloy layer of a
substrate or superconducting wire according to an embodiment of the present invention.
DESCRIPTION OF EMBODIMENTS
Embodiments of the present invention will be described hereinafter with
reference to the drawings. In the drawings, the same or corresponding elements have
the same reference characters allotted, and description thereof will not be repeated.

(Substrate)
Fig. 1 is a schematic sectional view of a substrate 1 according to an embodiment
of the present invention. Referring to Fig. 1, substrate 1 according to an embodiment
of the present invention includes a copper layer (hereinafter, also referred to as "Cu
layer") 2, an alloy layer 3 containing copper and nickel, formed on copper layer 2, a
nickel layer 4 (hereinafter, also referred to as "Ni layer") formed on alloy layer 3, and an
intermediate layer 5 formed on nickel layer 4.
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Substrate 1 may take the shape of a relatively lengthy tape.
(Copper Layer)
Cu layer 2 is suitable for an oriented substrate since Cu atoms are in biaxial
orientation. A "biaxial orientation" includes, not only a complete biaxial orientation,
but also the case where the angle of deviation of the crystal axis is less than or equal to
25°. Moreover, the orientation direction preferably corresponds to the case where the
<100> axis is in a direction perpendicular to the substrate face and the <010> axis is in
the direction of the length of the substrate.
Cu layer 2 can also be stacked on another metal or alloy. For example, Cu
layer 2 can be provided on stainless steel that is a material of high strength (hereinafter,
also referred to as SUS).
Cu layer 2 may take the shape of a relatively lengthy tape.
The thickness of Cu layer 2 is 15 to 18 |im, for example.
(Alloy Layer)
Alloy layer 3 is a non-magnetic metal containing nickel and copper. Preferably,
alloy layer 3 is oriented.
The saturation magnetization of alloy layer 3 is smaller than the saturation
magnetization of simple Ni. Namely, there is the case where the flux density is OT,
and the case where the flux density exceeds OT and is lower than the flux density of
simple Ni.
The magnetism of alloy layer 3 is smaller than the magnetism of simple Ni.
Namely, there is the case where the maximum energy (BHmax) is 0 J/m^, and the case
where the maximum energy exceeds 0 J/m^ and is smaller than the maximum energy of
simple Ni.
Alloy layer 3 has an Ni concentration distribution. Specifically, the
concentration of nickel in the alloy layer at the interface between the alloy layer and the
nickel layer indicated by A in Figs. 1 and 2 is greater than the concentration of nickel in
the alloy layer at the interface between the alloy layer and the copper layer indicated by
B in Figs. 1 and 2.
In alloy layer 3, the concentration of Ni in alloy layer 3 is preferably
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monotonically decreasing from the interface between alloy layer 3 and Ni layer 4
indicated by A in Figs. 1 and 2 towards the interface between alloy layer 3 and Cu layer
2 indicated by B in Figs. 1 and 2.
Monotonic decrease will be described with reference to Fig. 4. In Fig. 4 (a)
representing an example of monotonic decrease, the Ni concentration in alloy layer 3
always decreases from the interface between alloy layer 3 and Ni layer 4 indicated by A
towards the interface between alloy layer 3 and Cu layer 2 indicated by B, as shown in c,
d and e. Referring to Fig. 4 (b) representing another example of monotonic decrease,
the concentration of Ni in alloy layer 3 is the same or decreases from the interface
between alloy layer 3 and Ni layer 4 indicated by A towards the interface between alloy
layer 3 and Cu layer 2 indicated by B, as shown by f In other words, "monotonic
decrease" means that any region where the Ni concentration increases from the interface
between alloy layer 3 and Ni layer 4 indicated by A towards the interface between alloy
layer 3 and Cu layer 2 indicated by B is not included.
Alloy layer 3 has a thickness of 1.0 to 2.1 ^m, for example.
(Nickel Layer)
Ni layer 4 serves to prevent oxidation during formation of intermediate layer 5.
In the case where Cu layer 2 is oriented, Ni layer 4 is also oriented.
Ni layer 3 preferably has a thickness of 0.3 to 1.5 nm.
(Intermediate Layer)
Intermediate layer 5 serves to have superconducting layer 6 formed on its
surface. Intermediate layer 5 is formed of one or more layers. In the case where
intermediate layer 5 is formed of a plurality of layers, each layer constituting
intermediate layer 5 may be made of a substance differing from each other.
For intermediate layer 5, a metal oxide having at least one type of metal element
with a crystal structure of the pyrochlore, fluorite, rock salt or perovskite type is
adopted. Specifically, rare earth element oxide such as Ce02, YSZ (Yttria Stabilized
Zirconia), BZO (BaZrOs), STO (SrTiOs), AI2O3, YAIO3, MgO, Ln-M-0 based
compound (Ln is one or more type of lanthanoid element, M is one or more type of
element selected from Sr, Zr and Ga, and O is oxygen) can be cited. Such oxide
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serves to alleviate the difference in the crystal constant and crystal orientation between
Cu layer 2 that is the oriented metal substrate and superconducting layer 6 formed on
intermediate layer 5, and prevents the flow out of metal atoms from Cu layer 2 towards
superconducting layer 6. Ce02, for example, can be cited for such a material.

(Superconducting Wire)
Fig. 2 is a schematic sectional view of superconducting wire 7 according to an
embodiment of the present invention. Referring to Fig. 2, superconducting wire 7
according to an embodiment of the present invention includes a copper layer 2, an alloy
layer 3 containing copper and nickel, formed on copper layer 2, a nickel layer 4 formed
on alloy layer 3, an intermediate layer 5 formed on nickel layer 4, and a
superconducting layer 6 formed on intermediate layer 5.
Superconducting wire 7 may have the shape of a relatively lengthy tape.
Copper layer 2, alloy layer 3, nickel layer 4, and intermediate layer 5 in
superconducting wire 7 are similar to those adopted for substrate 1.
(Superconducting Layer)
Superconducting layer 6 has the shape of a relatively lengthy tape.
Superconducting layer 6 is a superconductor or the like represented by REBaaCusOy (y
is 6 - 8, more preferably substantially 7; RE implies a rare earth element such as Y
(yttrium), or Gd (gadolinium), Sm (samarium). Ho (holmium)). Preferably,
superconducting layer 6 is formed of GdBCO, for example. GdBCO is represented as
GdBa2Cu30y (y is 6 - 8, more preferably substantially 7).
Superconducting wire 7 may further include a protection layer (not shown)
formed on superconducting layer 6. The protection layer protects superconducting
layer 6, and is the contact region with an external electrode. The protection layer is
not particularly limited as long as it has high conductivity. Preferably, Ag, Au, Pt, Al,
or an alloy thereof is adopted.

(Method of Producing Substrate)
Fig. 3 is a schematic sectional view to describe a method of producing substrate
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1 and superconducting wire 7 according to an embodiment of the present invention.
Referring to Fig. 3, a method of producing substrate 1 according to an embodiment of
the present invention includes the steps of preparing a substrate having formed on Cu
layer 2 shown in Fig. 3 (a) an Ni layer 4 through plating, as shown in Fig. 3 (b);
alloying a portion of Ni layer 4 while leaving the remaining portion of Ni layer 4, as
shown in Fig. 3 (c); and epitaxial-growing an intermediate layer 5 on Ni layer 4, as
shown in Fig. 3 (d), after the step of alloying Ni layer 4. Furthermore, the method of
producing superconducting wire 7 according to an embodiment of the present invention
fiarther includes the step of forming a superconducting layer 6 on intermediate layer 5,
as shown in Fig. 3 (e).
(Step of Forming Nickel Layer)
As shown in Figs. 3 (a) and (b), a substrate is prepared, having Ni layer 4a
formed on Cu layer 2 through plating. The plating method includes, for example, an
electrolytic nickel plating process carried out on Cu layer 2, for example, in a solution
containing nickel chloride, nickel sulfate, or the like.
As shown in Fig. 3 (b), the thickness of Ni layer 4 formed on Cu layer 2 through
plating is preferably 1.3 to 3.6 ^m, more preferably 1.3 to 3.0 |im. In the case where
the thickness is greater than or equal to 1.3 ^m, diffiasion of all the Ni atoms to Cu layer
2 can be suppressed even if heat of approximately 800-1000°C is applied in the step of
alloying a portion of Ni layer 4 while leaving the remaining portion of Ni layer 4, as
will be described afterwards. Accordingly, the fianction of Ni layer 4, not readily
oxidized, and having a favorable matching lattice with intermediate layer 5, can be
exhibited effectively. In the case where the thickness is less than or equal to 3.6 \im,
the Ni constituting Ni layer 4 will readily diffuse to Cu layer 2 in the alloying step to
facilitate alloying effectively.
(Step of Alloying)
As shown in Fig. 3 (c), one portion of Ni layer 4 is alloyed while leaving the
remaining portion of Ni layer 4. By this step, Ni constituting Ni layer 4 and Cu
constituting Cu layer 2 are alloyed to allow an alloy layer 3 including Cu-Ni alloy to be
formed. The magnetism of Cu-Ni alloy is lower than that of simple Ni. Therefore,
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in the case where superconducting wire 7 is produced using substrate 1 including alloy
layer 3, concentration of the magnetic field towards the end region in the width
direction of superconducting wire 7 can be alleviated. Accordingly, the magnetic field
affecting the current flowing through superconducting wire 7 can be reduced, allowing
reduction in AC loss of the superconducting wire.
Furthermore, since a portion including the surface of Ni layer 4 is left,
orientation of Ni layer 4 can be maintained.
The step of alloying nickel layer 4 is preferably carried out under reduced
pressure, absent of hydrogen gas. For the atmosphere gas, Ar, N2, for example, or the
like, can be used. Reduced pressure is of a level lower than the atmospheric pressure,
preferably 0.1 to 10 Pa, for example.
The step of alloying nickel layer 4 is preferably carried out by subjecting Ni
layer 4 to thermal treatment at the temperature of 800-1000°C. If the temperature is
below 800°C, alloying of nickel will not proceed. Sufficient effect in reducing
magnetism cannot be achieved. If the temperature exceeds 1000°C, Ni and Cu will be
completely diffused to be alloyed, causing diffiision of Cu to the surface of the Ni layer.
Since Cu is readily oxidized, the orientation at the surface of Ni layer 4 cannot be
improved.
The step of alloying Ni layer 4 is preferably carried out by subjecting the Ni
layer to thermal treatment at the temperature of 800 to 1000°C for 15 to 25 minutes. If
the duration of thermal treatment is less than 15 minutes, alloying will not proceed
sufficiently. The effect of reducing magnetism cannot be expected. If the duration
exceeds 25 minutes, Ni and Cu will be completely diffused to be alloyed, causing
diffusion of Cu to the surface of the Ni layer. Since Cu is readily oxidized, the
orientation at the surface of Ni layer 4 cannot be improved.
(Step of Epitaxial-growing Intermediate Layer)
As shown in Fig. 3 (d), intermediate layer 5 is deposited on Ni layer 4
epitaxially to obtain substrate 1. The method of forming a thin film oxide qualified as
intermediate layer 5 is not particularly limited as long as the object of the present
invention is not impaired. For example, sputtering, EBD (Electron Beam Deposition),
10
PLD (Pulse Laser Deposition), thermal deposition or the like can be adopted.
For example, by epitaxial-growing a Ce02 thin film as intermediate layer 5 on
biaxial oriented Ni layer 4 having the <100> axis in a direction perpendicular to the
substrate face and the <010> axis in the length direction of the substrate after the
alloying step, a Ce02 thin film having the <100> axis oriented perpendicular to the
substrate face and the <011> axis oriented in the length direction of the substrate is
formed. Thus, a Ce02 thin film having high biaxial orientation can be obtained.
hi the case where the intermediate layer is formed of a plurality of layers, the
orientation can be maintained by depositing the second intermediate layer epitaxially on
the first intermediate layer, for example.

(Method of Producing Superconducting Wire)
Fig. 3 is a schematic sectional view to describe a method of producing substrate
1 and superconducting wire 7 according to an embodiment of the present invention.
Referring to Fig. 3, the method of producing superconducting wire 7 according to an
embodiment of the present invention includes the steps of preparing a substrate having
formed on Cu layer 2 shown in Fig. 3 (a) an Ni layer 4 through plating, as shown in Fig.
3 (b); alloying a portion of Ni layer 4 while leaving the remaining portion of Ni layer 4,
as shown in Fig. 3 (c); epitaxial-growing an intermediate layer 5 on Ni layer 4, as
shown in Fig. 3 (d), after the step of alloying Ni layer 4; and forming a superconducting
layer 6 on intermediate layer 5, as shown in Fig. 3 (e).
The step of forming a nickel layer, the step of alloying, and the step of epitaxialgrowing
an intermediate layer are similar to those in the method of producing a
substrate.

In the case where superconducting layer 6 is formed on intermediate layer 5 of
substrate 1 obtained according to the fourth embodiment, for example, a
superconducting layer 6 of high biaxial orientation can be obtained since intermediate
layer 5 has favorable orientation.
The method of forming a thin oxide film that will become superconducting layer
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6 is not particularly limited as long as the object of the present invention is not impaired.
Preferably, the PLD method, MOD (Metal Organic Deposition), MOCVD (Metal
Organic Chemical Vapor Deposition), and the like can be adopted.
Furthermore, for the purpose of protecting superconducting layer 6, a protection
layer (not shown) can be formed on superconducting layer 6, as necessary. The
method of forming a protection layer preferably includes, but not particularly limited to,
sputtering, EBD, PLD, thermal deposition, MOD, MOCVD, plating, and the like.
EXAMPLE
(Example 1)
First, a substrate having a 18 nm-thick Cu layer on a 100 ^im-thick SUS
substrate was prepared. The substrate including the Cu layer was subjected to
electrolytic nickel plating in a solution containing nickel chloride to form an Ni layer
having a thickness of 2.4 ^m.
The Ni layer was subjected to thermal treatment for 15 minutes using Ar gas
under the atmosphere of 0.1 Pa to 10 Pa in pressure at the thermal treatment
temperature of 850°C-1000°C. Thus, a Cu-Ni alloy layer was formed from the Ni
layer and Cu layer.
Immediately thereafter, sputtering was carried out using a mixture of H2 gas and
Ar gas as the reducing gas (composition: 3 mole % of H2 gas, 97 mole % of Ar gas)
under the atmosphere of 5.2 Pa in pressure and at the substrate temperature of 700°C to
form on the Ni layer a Ce02 thin film to a thickness of 0.15 |im as an intermediate layer.
On that Ce02 thin film, a YSZ thin film was formed to a thickness of 0.26 |im as the
second intermediate layer under the atmosphere of 2.6 Pa in pressure and at the
substrate temperature of 900°C with the mixture gas modified (composition: 0.5
mole % of O2 gas, 99.5 mole % of Ar gas). Finally, a Ce02 thin film was formed to a
thickness of 0.05 ^m as the third intermediate layer on the YSZ layer under the
atmosphere of 2.6 Pa in pressure and at the substrate temperature of 800°C with the
mixture gas modified (composition: 1 mole % of O2 gas, 99 mole % of Ar gas). Thus,
the substrate of Example 1 was obtained.
Then, GdBCO was deposited as the superconducting layer by PLD on the
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intermediate layer. Thus, the superconducting wire of Example 1 was obtained.
(Comparative Example 1)
A substrate and a superconducting wire were obtained in a manner similar to
those of Example 1 set forth above, provided that the Ni layer was not subjected to
thermal treatment.
(Comparative Example 2)
A substrate and a superconducting wire were obtained in a manner similar to
those of Example 1 set forth above, provided that the Ni layer was subjected to thermal
treatment for 30 minutes.
(Measurement Method)
For the substrates of Example 1 and Comparative Examples 1 and 2, the
thickness of each of the Ni layer, Cu-Ni layer (alloy layer), and Cu layer, as well as the
biaxial orientation of the CeOi thin film were measured. Furthermore, the hysteresis
loss was measured for the superconducting wire of Example 1 and Comparative
Examples 1 and 2. The results are shown in Table 1 set forth below.
The thickness of each layer in the substrate was measured by EPMA (Electron
Probe Micro-Analyzer).
With regard to the c-axis orientation of the Ce02 thin film on the substrate, the
X-ray diffraction peak intensity fi"om the (200) plane and (111) plane of the Ce02 thin
film (I (200) and 1(111)) was measured. The c-axis orientation of the Ce02 thin film
was evaluated by the numeric value of (I (200)/(I (200) + 1(111)). A higher numeric
value implies a higher c-axis orientation of the Ce02 thin film qualified as the
intermediate layer, and is preferable. The X-ray diffraction peak intensity from the
(200) plane represents the amount of crystals oriented in the direction where the <100>
axis is perpendicular to the substrate face. The X-ray diffraction peak intensity from
the (111) plane represents the amount of crystals uniaxially oriented in the direction
where the <111> axis is perpendicular to the substrate face.
With regard to the hysteresis loss of the superconducting wire, a magnetic field
was applied in a direction parallel to the tape face of the superconducting wire at room
temperature. The hysteresis loss thereof was measured using a vibrating sample
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magnetometer (VSM).
(Measurement Results)
Table 1
Comparative Comparative ^ , ,
c 1 1 c 1 1 Example 1
Example 1 Example 2
Thermal Treatment Temperature Not Treated 850-1000°C 850-1000°C
Thermal Treatment Duration - 30 minutes 15 minutes
Ni layer 2.4 ^m 0 ^m 1.3 nm
Substrate Structure Cu-Ni layer 0 ^m 3 urn 1 7 um
After Thermal -— ^-^^ ^"-^-^^
Treatment ^" '^y^*" 18^m 17.4 ^m 17.5 um
|SUSlayer ~ 100 ^m 100 ^im 100 um
Hysteresis Loss 53 J/m^ 0 J/m^ 15 J/m^
C-axis orientation of Ce02 thin film
(I(200)/I(200)+I(lll))xl00) I ^^^° I ^Q^" I ^^^^
By subjecting the Ni layer to thermal treatment for 15 minutes as in Example 1,
a Cu-Ni alloy layer of 1.7 ^lm in thickness was formed while leaving an Ni layer of 1.3
|im in thickness. By the results of EPMA analysis, it was confirmed that the Ni
concentration in the alloy layer decreased monotonically from the interface between the
alloy layer and the nickel layer towards the interface between the alloy layer and the
copper layer. The Ce02 thin film had a favorable biaxial orientation since the Cu and
Ni were alloyed only partially, and Cu did not diffuse to the surface of the Ni layer.
Furthermore, the hysteresis loss could be reduced as compared to Comparative
Example 1 not having the Ni layer subjected to thermal treatment.
In Comparative Example 1, Ni and Cu were not alloyed since the Ni layer was
not subjected to thermal treatment. Therefore, the hysteresis loss of the
superconducting wire was considerable.
In Comparative Example 2, Ni and Cu were completely alloyed by the thermal
treatment on the Ni layer carried out for 30 minutes. Therefore, the hysteresis loss of
the superconducting wire was reduced. However, since Cu was difllised to the surface
of the Ni layer, the biaxial orientation of the Ce02 thin film was degraded as compared
to Comparative Example 1 where the Ni layer was not subjected to thermal treatment.
It is to be understood that the embodiments and examples disclosed herein are
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only by way of example, and not to be taken by way of iimitation. The scope of the
present invention is not limited by the description above, but rather by the terms of the
appended claims, and is intended to include any modifications within the scope and
meaning equivalent to the terms of the claims.
REFERENCE SIGNS LIST
1 substrate; 2 copper layer; 3 alloy layer; 4 nickel layer; 5 intermediate layer; 6
superconducting layer; 7 superconducting wire.

WE CLAIMS
1. A substrate (1) comprising:
a copper layer (2),
an alloy layer (3) containing copper and nickel, formed on said copper layer (2),
a nickel layer (4) formed on said alloy layer (3), and
an intermediate layer (5) formed on said nickel layer (4),
wherein a concentration of nickel in said alloy layer (3) at an interface between
said alloy layer (3) and said nickel layer (4) is greater than the concentration of nickel in
said alloy layer (3) at the interface between said alloy layer (3) and said copper layer (2).
2. The substrate (1) according to claim 1, wherein the concentration of nickel
in said alloy layer (3) decreases monotonically from the interface between said alloy
layer (3) and said nickel layer (4) towards the interface between said alloy layer (3) and
said copper layer (2).
3. A method of producing a substrate (1), comprising the steps of:
preparing a substrate having a nickel layer (4) formed on a copper layer (2)
through plating,
alloying a portion of said nickel layer (4) while leaving a remaining portion of
said nickel layer (4), and
epitaxial-growing an intermediate layer (5) on said nickel layer (4) after the step
of alloying said nickel layer (4).
4. The method of producing a substrate (1) according to claim 3, wherein the
step of alloying said nickel layer (4) is carried out under reduced pressure, absent of
hydrogen gas.
5. A superconducting wire (7) comprising:
a copper layer (2),
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an alloy layer (3) containing copper and nickel, formed on said copper layer (2),
a nickel layer (4) formed on said alloy layer (3),
an intermediate layer (5) formed on said nickel layer (4), and
a superconducting layer (6) formed on said intermediate layer (5),
wherein a concentration of nickel in said alloy layer (3) at an interface between
said alloy layer (3) and said nickel layer (4) is greater than the concentration of nickel in
said alloy layer (3) at the interface between said alloy layer (3) and said copper layer (2).
6. The superconducting wire (7) according to claim 5, wherein the
concentration of nickel in said alloy layer (3) decreases monotonically from the
interface between said alloy layer (3) and said nickel layer (4) towards the interface
between said alloy layer (3) and said copper layer (2).
7. A method of producing a superconducting wire (7) comprising the steps of:
preparing a substrate having a nickel layer (4) formed on a copper layer (2)
through plating,
alloying a portion of said nickel layer (4) while leaving a remaining portion of
said nickel layer (4),
epitaxial-growing an intermediate layer (5) on said nickel layer (4) after said
step of alloying said nickel layer (4), and
forming a superconducting layer (6) on said intermediate layer (5).
8. The method of producing a superconducting wire (7) according to claim 7,
wherein the step of alloying said nickel layer (4) is carried out under reduced pressure,
absent of hydrogen gas.