JP5889094B2 - Superconducting wire and method of manufacturing superconducting wire - Google Patents

Description

  The present invention relates to a superconducting wire and a method of manufacturing a superconducting wire.

  Conventionally, a superconducting wire provided with a superconducting layer mainly composed of an oxide superconductor in which the a-axis direction or the b-axis direction of the crystal axis is parallel to the longitudinal direction of the substrate on one surface side in the thickness direction of the tape-like substrate has been provided. Known (for example, Patent Document 1).

JP-A-3-279203

However, when the a-axis direction or the b-axis direction of the crystal axis in the oxide superconductor is parallel to the longitudinal direction of the substrate, the irreversible strain εirr is high (good), but the superconducting wire is distorted to the irreversible strain εirr (irreversible). The critical current Ic is greatly reduced during strain.
In particular, a superconducting coil wound with a superconducting wire is used in a state where the superconducting wire is distorted, so that a high critical current Ic is required at the time of irreversible strain. This is because if the critical current Ic is greatly reduced during irreversible strain, the amount of current that can be passed through the superconducting layer is limited when the superconducting coil is used.

  The present invention has been made in view of the above facts, and an object of the present invention is to provide a superconducting wire and a method of manufacturing the superconducting wire that can suppress a decrease in the critical current Ic during irreversible strain.

The above-described problems of the present invention have been solved by the following means.
<1> A tape-shaped substrate and an RE-based superconductor (RE: rare earth element) that is provided on one surface side of the substrate in the thickness direction and in which the a-axis direction or the b-axis direction of the crystal axis intersects the longitudinal direction of the substrate And at least one oxide layer mainly composed of a crystalline oxide in which the Miller index <100> direction or the Miller index <010> direction intersects the longitudinal direction, the substrate and the substrate have a, and an intermediate layer provided between the superconducting layer, wherein the angle α between the longitudinal direction and the a-axis direction or the b axis direction, is less than 45 degrees, the superconducting wire is 13 degrees or more .
< 2 > The superconducting wire according to < 1 >, wherein the angle α is 18 degrees or more.
< 3 > The superconducting wire according to < 1 > or <2> , wherein the angle α is 36 degrees or less.
< 4 > The superconducting wire according to any one of < 1 > to < 3 >, wherein the angle α is 32 degrees or less.
< 5 > The superconducting wire according to any one of <1> to < 4 >, wherein an angle formed by the c-axis direction of the crystal axis and the thickness direction is 5 degrees or less.

  ADVANTAGE OF THE INVENTION According to this invention, the superconducting wire which can suppress the fall of critical current Ic at the time of irreversible strain, and the manufacturing method of a superconducting wire were able to be provided.

FIG. 1 is a diagram showing a laminated structure of superconducting wires according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of the layer configuration of the intermediate layer 20 when the intermediate layer 20 of the superconducting wire substrate 2 has a multilayer structure. FIG. 3 is an explanatory diagram showing an example of the laminated structure of the superconducting wire 1 when the angle α is 45 degrees, in terms of the unit cell and the Miller index of the material that is the main component of each layer, and (A) shows each layer of the superconducting wire Is the figure which looked at the thickness direction of the tape board | substrate, (B) is the figure which looked at each layer of the superconducting wire from the width direction of the tape board | substrate. FIG. 4 is an explanatory diagram showing an example of a laminated structure of superconducting wires when the angle α is less than 45 degrees, in terms of a unit cell and a Miller index, which are the main components of each layer, and (A) shows each layer of the superconducting wire. Is the figure which looked at from the thickness direction of the tape substrate, and (B) is the figure which looked at each layer of the superconducting wire 1 from the width direction of the tape substrate. FIG. 5 is an explanatory diagram showing an example different from FIG. 4 of the laminated structure of the superconducting wire when the angle α is less than 45 degrees, expressed by the unit cell and the Miller index of the material that is the main component of each layer. ) Is a view of each layer of the superconducting wire as viewed from the thickness direction of the tape substrate, and (B) is a view of each layer of the superconducting wire as viewed from the width direction of the tape substrate. FIG. 6 is an explanatory diagram showing an example different from FIGS. 4 and 5 of the laminated structure of the superconducting wire in the case where the angle α is less than 45 degrees, by the unit cell and the Miller index of the material that is the main component of each layer. (A) is the figure which looked at each layer of the superconducting wire from the thickness direction of the tape substrate, (B) is the figure which looked at each layer of the superconducting wire from the width direction of the tape substrate. FIG. 7 is a diagram illustrating the relationship between the assist beam irradiation direction and the substrate. FIG. 8 is a graph plotting the relationship between the angle α (°) and εirr (%). FIG. 9 is a graph plotting the relationship between the angle α (°) and Ic (εirr) / Ic0. FIG. 10 is an explanatory view showing an example of a laminated structure of superconducting wires when the angle α is 0 degrees, expressed by a unit cell and a Miller index of a material that is the main component of each layer, and (A) shows each layer of the superconducting wires. It is the figure seen from the thickness direction of the tape board | substrate, (B) is the figure which looked at each layer of the superconducting wire from the width direction of the tape board | substrate.

  Hereinafter, a superconducting thin film according to an embodiment of the present invention will be specifically described with reference to a superconducting wire as an example with reference to the accompanying drawings. In the drawings, members (components) having the same or corresponding functions are denoted by the same reference numerals and description thereof is omitted as appropriate.

<< Schematic configuration of superconducting wire >>
FIG. 1 is a view showing a laminated structure of superconducting wires 1 according to an embodiment of the present invention.
As shown in FIG. 1, the superconducting wire 1 has a laminated structure in which an intermediate layer 20, a superconducting layer 30, and a protective layer 40 are sequentially formed on a substrate 10. Further, the substrate 10 and the intermediate layer 20 in FIG. 1 constitute the superconducting wire base material 2.

The substrate 10 is a tape-like substrate (hereinafter referred to as a tape substrate 10) extending in the arrow L direction (longitudinal direction) in the figure, and one surface in the thickness direction is a film formation surface (main surface). The tape substrate 10 is made of a low magnetic non-oriented metal base material or non-oriented ceramic base material. As the material of the metal substrate, for example, metals such as Co, Cu, Ni, Ti, Mo, Nb, Ta, W, Mn, Fe, Ag, and Cr, which are excellent in strength and heat resistance, or alloys thereof are used. It is done. Particularly preferred are stainless steel, Hastelloy (registered trademark), and other nickel-based alloys that are excellent in corrosion resistance and heat resistance. Various ceramics may be arranged on these various metal materials. Moreover, as a material of the ceramic substrate, for example, MgO, SrTiO ₃ , yttrium-stabilized zirconia, or the like is used.

  The intermediate layer 20 is a layer provided between the tape substrate 10 and the superconducting layer 30 in order to achieve high biaxial orientation in the superconducting layer 30. Such an intermediate layer 20 has, for example, physical values such as a coefficient of thermal expansion and a lattice constant that are intermediate values between the substrate 10 and the superconductor constituting the superconducting layer 30. Further, the intermediate layer 20 may have a single layer structure or a multilayer structure. However, regardless of whether the intermediate layer 20 has a single layer structure or a multilayer structure, the intermediate layer 20 has at least one layer mainly composed of an oxide. Here, the “main body” described above and hereinafter represents the component contained in the layer in the largest amount among the components constituting the layer. An example of a specific layer configuration when the intermediate layer 20 has a multilayer structure is shown in FIG.

  As shown in FIG. 2, the intermediate layer 20, which is an example of a multilayer structure, has a configuration in which a bed layer 22, a forced alignment layer 24, an LMO layer 26, and a cap layer 28 are sequentially stacked.

The bed layer 22 is formed on the tape substrate 10 (one surface in the thickness direction T) and is a layer for preventing the constituent elements of the tape substrate 10 from diffusing. As the constituent material of the bed layer 22, Gd ₂ Zr ₂ O _7-λ (-1 <λ <1, hereinafter referred to as GZO), YAlO ₃ (yttrium aluminate), YSZ (yttria stabilized zirconia), Y ₂ O ₃ , Gd ₂ O ₃ , Al ₂ O ₃ , B ₂ O ₃ , Sc ₂ O ₃ , Cr ₂ O ₃ , REZrO, CeO ₂ , PrO ₂ , RE ₂ O _{3 and the} like can be used. Here, RE represents a single rare earth element or a plurality of rare earth elements. The bed layer 22 may have other functions such as improving the biaxial orientation of the forced alignment layer 24 together with the diffusion preventing function. In order to have a function of improving the biaxial orientation, it is preferable to use GZO, CeO ₂ , PrO ₂ or the like as a constituent material of the bed layer 22. “Biaxial orientation” means that the c-axis orientation and a-axis in-plane orientation of the crystals in the layer are high.

  The thickness of the bed layer 22 is not particularly limited, but is 10 nm or more from the viewpoint of suppressing a decrease in the function of the bed layer 22 (suppression of diffusion of metal elements from the substrate 10 and improvement of orientation of the forced alignment layer). It is preferable that the thickness is 500 nm or less from the viewpoint of suppressing warpage of the substrate 10. In particular, the thickness is more preferably 100 nm or less from the viewpoint of reducing the thickness due to a request for cost or the like.

  The forced alignment layer 24 is formed on the bed layer 22 and has biaxial orientation, and is a layer for aligning the crystals of the superconducting layer 30 in a certain direction. The forced alignment layer 24 is mainly composed of a crystalline material such as NbO or MgO. Moreover, the same material as the bed layer 22, for example, GZO can also be used.

  Although the film thickness of the forced alignment layer 24 is not specifically limited, For example, they are 1 nm or more and 20 nm or less.

  The term “forced alignment layer” refers to a biaxially oriented layer formed by the IBAD method, and whether or not it is a forced alignment layer formed by the IBAD method is determined by X-ray diffraction measurement. Thus, it can be specified by analyzing whether the bed layer 22 is non-oriented and whether the layer to be the forced alignment layer 24 has biaxial orientation.

The LMO layer 26 is disposed between the forced alignment layer 24 and the cap layer 28 and has a function of improving the lattice matching of the cap layer 28. Such an LMO layer 26 is an oxide layer made of a crystalline material whose composition formula is represented by LaMnMO _{3 + λ} (λ is an oxygen non-stoichiometric amount). Although the value of λ is not particularly limited, for example, −1 <λ <1.

  The thickness of the LMO layer 26 is not particularly limited, but is preferably 100 nm or less from the viewpoint of suppressing the surface roughness of the LMO layer 26, and is preferably 4 nm or more from the viewpoint of manufacturing. A specific value is 30 nm.

The cap layer 28 is formed on the LMO layer 26 and is a layer for protecting the LMO layer 26 and further improving lattice matching with the superconducting layer 30. Specifically, it is composed of a fluorite crystal structure containing a rare earth element and having self-orientation. This fluorite-type crystal structure is at least one selected from, for example, CeO ₂ and PrO ₂ . The cap layer 28 only needs to mainly include a fluorite-type crystal structure, and may further contain impurities.

  The film thickness of the cap layer 28 is not particularly limited, but is preferably 50 nm or more, and more preferably 300 nm or more in order to obtain sufficient orientation. However, if it exceeds 600 nm, the film formation time increases, so it is preferable to set it to 600 nm or less.

  The above intermediate layer 20 can be omitted. Further, the intermediate layer 20 may have a single layer structure instead of the multilayer structure as shown in FIG. Further, even in the case of a multilayer structure, the intermediate layer 20 shown in FIG. 2 is an example, and any one of the bed layer 22, the forced alignment layer 24, the LMO layer 26, and the cap layer 28 may be omitted. In addition, new layers may be added.

Next, the superconducting layer 30 shown in FIG. 1 is provided (deposited) on the surface of the intermediate layer 20 on one surface side in the thickness direction T of the tape substrate 10, and the composition formula is represented by REBa ₂ Cu ₃ O _7-λ . Mainly based on RE superconductors. RE in the RE-based superconductor is a single rare earth element or a plurality of rare earth elements such as Y, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu, and among these, the Ba site And Y is preferable because substitution is difficult to occur. Further, λ is an oxygen nonstoichiometric amount, for example, 0 or more and 1 or less, and is preferably closer to 0 from the viewpoint that the superconducting transition temperature is high. The oxygen non-stoichiometric amount may be less than 0, that is, take a negative value when high-pressure oxygen annealing or the like is performed using an apparatus such as an autoclave.

  The film thickness of the superconducting layer 30 is not particularly limited, but is, for example, not less than 500 nm and not more than 3000 nm.

  In principle, the RE superconductor, which is the main component of the superconducting layer 30, has an orthorhombic crystal structure. In this crystal structure, the RE-based superconductor has a-axis, b-axis, and c-axis (axis length: a <b <c) as crystal axes. However, depending on the oxygen deficiency λ of the RE superconductor, there may be a tetragonal crystal structure. In this case, the RE superconductor has an a axis and a c axis as crystal axes (a <c). These a-axis, b-axis, and c-axis can also be expressed by Miller index <100>, Miller index <010>, and <001>.

  In the present embodiment, the RE-based superconductor that is the main component of the superconducting layer 30 has the crystallographic axis a-axis direction or b-axis direction intersecting the longitudinal direction L of the tape substrate 10. This is because, compared with the case where the a-axis direction or the b-axis direction is parallel to the longitudinal direction L of the tape substrate 10, the decrease in the critical current Ic is suppressed during irreversible strain.

  In addition, the angle α formed by the a-axis direction or b-axis direction of the RE-based superconductor and the longitudinal direction L is preferably less than 45 degrees. This is because, when the angle α is less than 45 degrees, the arrangement of the intermediate layer 20 (the direction of the Miller index) must be devised more than when the angle α is less than 45 degrees. It is.

Specifically, when the angle α is 45 degrees, the Miller index <100> direction or the Miller index <010> direction of the oxide that is the main component of each layer of the intermediate layer 20 is the longitudinal direction depending on the stacked structure of the intermediate layer 20 Even if parallel to L, the intersection of the a-axis or b-axis of the RE-based superconductor with the longitudinal direction L can be realized.
However, when the angle α is less than 45 degrees, if the Miller index <100> direction or the Miller index <010> direction of the oxide that is the main component of each layer of the intermediate layer 20 is parallel to the longitudinal direction L, the RE-based superconductor It is difficult to cross the longitudinal direction L with the a-axis or b-axis.
The reason why the oxide axial direction is expressed in Miller index not in the a-axis / b-axis notation is that most of the oxides that are main components of the intermediate layer 20 are cubic crystals, This is because it is difficult to distinguish the b-axis.

This will be described more specifically with reference to FIGS.
FIG. 3 is an explanatory diagram showing an example of the laminated structure of the superconducting wire 1 when the angle α is 45 degrees, in terms of the unit cell and the Miller index of the material that is the main component of each layer. It is the figure which looked at each layer from the thickness direction T of the tape board | substrate 10, (B) is the figure which looked at each layer of the superconducting wire 1 from the width direction of the tape board | substrate 10. FIG.
FIG. 4 is an explanatory diagram showing an example of the laminated structure of the superconducting wire 1 when the angle α is less than 45 degrees, in terms of the unit cell and the Miller index of the material that is the main component of each layer, and (A) is the superconducting wire 1. Is a view of each layer of FIG. 1 as viewed from the thickness direction T of the tape substrate 10, and (B) is a view of the layers of the superconducting wire 1 as viewed from the width direction of the tape substrate 10.
FIG. 5 is an explanatory diagram showing an example different from FIG. 4 of the laminated structure of the superconducting wire 1 in the case where the angle α is less than 45 degrees, in terms of the unit cell and the Miller index of the material that is the main component of each layer. (A) is a view of each layer of the superconducting wire 1 as viewed from the thickness direction T of the tape substrate 10, and (B) is a view of each layer of the superconducting wire 1 as viewed from the width direction of the tape substrate 10.
FIG. 6 is an explanatory diagram showing an example of the laminated structure of the superconducting wire 1 in the case where the angle α is less than 45 degrees, in terms of the unit cell and the Miller index of the material that is the main component of each layer. (A) is the figure which looked at each layer of superconducting wire 1 from thickness direction T of tape substrate 10, and (B) is the figure which looked at each layer of superconducting wire 1 from the width direction of tape substrate 10.
FIG. 10 is an explanatory view showing an example of a laminated structure of superconducting wires when the angle α is 0 degrees, expressed by a unit cell and a Miller index of a material that is the main component of each layer, and (A) shows each layer of the superconducting wires. It is the figure seen from the thickness direction of the tape board | substrate, (B) is the figure which looked at each layer of the superconducting wire from the width direction of the tape board | substrate.
In addition, the upper figure of each figure shows the tape substrate 10 side of the superconducting wire 1, and the lower figure of each figure shows the superconducting layer 30 side of the superconducting wire 1.

As shown in FIG. 3, the intermediate layer 20 has a forced alignment layer 24 mainly composed of MgO and a cap layer 28 mainly composed of CeO ₂ , and the LMO layer 26 is interposed between the forced alignment layer 24 and the cap layer 28. If not, even if the Miller index <100> direction or the Miller index <010> direction of the oxide (MgO and CeO ₂ ) that is the main component of each layer of the intermediate layer 20 is parallel to the longitudinal direction L, the superconducting layer 30 The a-axis direction or b-axis direction of the main RE-based superconductor (REBa ₂ Cu ₃ O _7-λ ) intersects the longitudinal direction L, and the a-axis direction or b-axis direction and the longitudinal direction L of the RE-based superconductor. Is 45 degrees.
On the other hand, as shown in FIG. 4, when the intermediate layer 20 includes a forced alignment layer 24 mainly composed of MgO, an LMO layer 26 mainly composed of LMO, and a cap layer 28 mainly composed of CeO ₂ , The Miller index <100> direction or the Miller index <010> direction of the main oxide of each layer of the layer 20 intersects the longitudinal direction L (the angle between the MgO Miller index <010> direction and the longitudinal direction L is β The a-axis direction or the b-axis direction of the RE-based superconductor (REBa ₂ Cu ₃ O _7-λ ) that is the main body of the superconducting layer 30 intersects the longitudinal direction L, and the a-axis direction or the b-axis direction. And the longitudinal direction L is the same as the angle β formed by the MgO Miller index <010> direction and the longitudinal direction L, and is less than 45 degrees.

However, as in FIG. 3, the intermediate layer 20 has a forced alignment layer 24 mainly composed of MgO and a cap layer 28 mainly composed of CeO ₂ , and the LMO layer 26 is interposed between the forced alignment layer 24 and the cap layer 28. 5, the Miller index <100> direction or the Miller index <010> direction of the oxide (MgO and CeO ₂ ) that is the main component of each layer of the intermediate layer 20 is the longitudinal direction, as shown in FIG. RE-based superconductor (REBa ₂ Cu ₃ O _7-λ ) that is the main component of the superconducting layer 30 by crossing L (the angle between the MgO Miller index <010> direction and the longitudinal direction L is β). The a-axis direction or b-axis direction intersects the longitudinal direction L, and the angle α formed by the a-axis direction or b-axis direction and the longitudinal direction L is an angle of 45 ° −β.

Further, as shown in FIG. 6, a forced alignment layer 24 mainly composed of GZO and a cap layer 28 mainly composed of CeO ₂ are included, and no LMO layer 26 is formed between the forced alignment layer 24 and the cap layer 28. In this case, the Miller index <100> direction or the Miller index <010> direction of the oxide (GZO and CeO ₂ ) that is the main component of each layer of the intermediate layer 20 intersects the longitudinal direction L (MgO mirror index <010> direction and longitudinal direction). By making β an angle formed with the direction L, the a-axis direction or the b-axis direction of the RE-based superconductor (REBa ₂ Cu ₃ O _7-λ ) that is the main component of the superconducting layer 30 intersects the longitudinal direction L. And the angle α formed by the a-axis direction or the b-axis direction and the longitudinal direction L.

As shown in FIG. 10, the intermediate layer 20 includes a forced alignment layer 24 mainly composed of MgO, an LMO layer 26 mainly composed of LMO, and a cap layer 28 mainly composed of CeO ₂ . As shown in FIG. 5, when the mirror index <100> direction or the mirror index <010> direction of the oxide that is the main component of the forced alignment layer 24 of the intermediate layer 20 is not intersected with the longitudinal direction L, the RE that is the main component of the superconducting layer 30 The a-axis direction or the b-axis direction of the system superconductor (REBa ₂ Cu ₃ O _7-λ ) is parallel to the longitudinal direction L.

  As described above, in order to make the angle α less than 45 degrees, the Miller index <100> direction or the Miller index <010> direction intersects the longitudinal direction of the intermediate layer 20 compared to the case where the angle α is 45 degrees. It is necessary to include at least one oxide layer mainly composed of crystalline oxide.

  Further, the angle α is preferably 13 degrees or more. This is because, when the angle α is 13 degrees or more, the decrease in the critical current Ic is rapidly suppressed at the time of irreversible strain as the angle becomes larger than when the angle α is less than 13 degrees.

  Further, the angle α is preferably 18 degrees or more. This is because when the angle α is 18 degrees or more, the decrease in the critical current Ic is more suppressed during irreversible strain than when the angle α is less than 18 degrees.

  By the way, when the angle α is increased as described above, the critical current Ic (εirr) during irreversible strain increases, but conversely, the value of the irreversible strain εirr decreases. When the value of the irreversible strain εirr is low, a high magnetic field cannot be generated due to the hoop stress. Therefore, when the superconducting wire 1 according to the present embodiment is used particularly for a superconducting coil or the like, it is required to achieve both a high critical current Ic and a high irreversible strain εirr.

  Therefore, the angle α is preferably 36 degrees or less. This is because if the angle α is 36 degrees or less, the value of the irreversible strain εirr increases rapidly as the angle α becomes lower than when the angle α exceeds 36 degrees.

  The angle α is preferably 32 degrees or less. This is because if the angle α is 32 degrees or less, the value of the irreversible strain εirr becomes higher as the angle α is lower than when the angle α is larger than 32 degrees.

  Further, the angle formed by the c-axis direction of the crystal axis and the thickness direction T is preferably 5 degrees or less, and more preferably, the c-axis direction of the crystal axis and the thickness direction T are parallel. This is because the current component flowing in the longitudinal direction L of the superconducting layer 30 can be increased.

<< Manufacturing method of superconducting wire >>
Next, the manufacturing method of the superconducting wire which concerns on embodiment of this invention is demonstrated.

When the angle α formed by the a-axis direction or the b-axis direction and the longitudinal direction L of the RE-based superconductor (REBa ₂ Cu ₃ O _7-λ ) which is the main body of the superconducting layer 30 is 45 degrees, it is shown in FIG. Thus, the intermediate layer 20 having the forced alignment layer 24 mainly composed of MgO and the cap layer 28 mainly composed of CeO ₂ and not having the LMO layer 26 between the forced alignment layer 24 and the cap layer 28 is formed. That's fine.

When the angle α formed between the a-axis direction or the b-axis direction and the longitudinal direction L of the RE-based superconductor (REBa ₂ Cu ₃ O _7-λ ) which is the main body of the superconducting layer 30 is less than 45 degrees, for example, FIG. And when manufacturing the superconducting wire shown in FIG. 4, there are the following manufacturing methods.

  First, the step of preparing the tape substrate 10 described above is performed.

  Next, a step of forming the bed layer 22 on one surface of the tape substrate 10 in the thickness direction T is performed.

  Examples of the method for forming the bed layer 22 include a MOD method, a PLD method, a CVD method, a MOCVD method, and a sputtering method. Among these, it is preferable to use a sputtering method from the viewpoint of easy manufacture.

Next, a step of forming the forced alignment layer 24 is performed.
Examples of the method for forming the forced alignment layer 24 (oxide layer) include a method of forming a film by an IBAD method in an atmosphere of an inert gas (argon), oxygen, or a mixed gas of an inert gas (argon) and oxygen. . When the forced alignment layer 24 is formed, the surface component of the tape substrate 10 in the direction in which the assist ion beam is irradiated intersects with the vector in the short direction of the tape substrate 10 while irradiating the assist ion beam. Then, vapor deposition particles ejected from a vapor deposition source (MgO or the like) by RF sputtering (or ion beam sputtering) are deposited on the film formation surface.
Specifically, as shown in FIG. 7, the vector in the thickness direction T (normal direction) of the tape substrate 10 is X, the vector in the direction in which the tape substrate 10 is irradiated with the assist ion beam is Y, and the vector Y When the substrate surface component is Y ′ and the short direction (width direction) vector of the tape substrate 10 is Z, the angle δ formed by the vector Z and the vector Y ′ is preferably more than 0 degree and less than 45 degrees. When forming the superconducting wire shown in FIGS. 4 to 6 and setting the angle δ shown in FIG. 7 to form the forced alignment layer 24, the angle β and the angle α correspond to the angle δ in the case of FIG. In the case of 5, the angle β corresponds to the angle δ, the angle α corresponds to the angle (45 degrees−δ), and in the case of FIG. 6, the angle β corresponds to the angle (45 degrees−δ), and the angle α corresponds to the angle δ. Corresponding to
The angle γ formed by the vector X and the vector Y is preferably 40 degrees or more and 60 degrees or less. This is because the forced alignment layer 24 is suitable for highly biaxial alignment.

  If the formation method of the forced alignment layer 24 is devised in this way, FIGS. 4 to 6 (GZO is the forced alignment layer in FIG. 6), the Miller index <100 of the oxide that is the main component of the forced alignment layer 24. > Direction or Miller index <010> direction intersects with the longitudinal direction L, and the Miller index <100> of the material mainly used for the LMO layer 26, the cap layer 28 and the superconducting layer 30 formed after the forced alignment layer 24 The direction or Miller index <010> direction intersects the longitudinal direction L.

Next, a process of forming the LMO layer 26, the cap layer 28, and the superconducting layer 30 is performed.
Examples of a method for forming each of these layers include film formation by a PLD method or an RF sputtering method performed while heating the tape substrate 10.

  The superconducting wire 1 which concerns on embodiment of this invention is obtained by passing through the above manufacturing process.

  Although the present invention has been described in detail with respect to specific embodiments, the present invention is not limited to such embodiments, and various other embodiments are possible within the scope of the present invention. It is clear to the contractor.

  Hereinafter, the superconducting wire and the method of manufacturing the superconducting wire according to the present invention will be described with reference to examples, but the present invention is not limited to these examples.

<< Example 1-1 >>
In Example 1-1, a superconducting wire having a laminated structure of superconducting layer / CeO ₂ / LMO / IBAD-MgO / GZO / Hastelloy metal substrate as shown in FIG. 4 was produced. In FIG. 4, the description of GZO is omitted.

Specifically, a Hastelloy metal substrate as the tape substrate 10 was introduced into a sputtering apparatus and evacuated to 1 × 10 ⁻³ Pa. Then, the bed layer 22 made of GZO was formed by sputtering at a temperature of about 150 ° C. with a wire transport speed of 30 m / h and a film thickness of 100 nm using GZO as an evaporation source.

The tape substrate 10 on which the bed layer 22 made of GZO was formed was introduced into an IBAD apparatus and evacuated to 1 × 10 ⁻³ Pa. Then, the forced alignment layer 24 made of MgO was formed at a temperature of about 150 ° C. with a wire conveyance speed of 80 m / h and a film thickness of 3 nm by using IBAD method using MgO as a deposition source.
The assist beam irradiation direction was adjusted so that the angle γ formed by the vector X and the vector Y shown in FIG. 7 was about 45 degrees and the angle δ formed by the vector Z and the vector Y ′ was 5 degrees. At this time, the assist ion beam device is installed at an angle of 5 degrees from the width direction of the tape substrate 10 toward the traveling direction side of the wire conveyance.

Next, the tape substrate 10 on which the forced alignment layer 24 was formed was introduced into a sputtering apparatus and evacuated to 1 × 10 ⁻³ Pa. Then, an LMO layer 26 made of LMO was formed with a film thickness of 15 nm by RF sputtering using LMO as an evaporation source.
Specifically, the LMO film was deposited by RF sputtering in an Ar gas atmosphere at a temperature of about 850 ° C. and a pressure of about 0.5 Pa under the conditions of a sputtering output of about 200 W and a wire conveyance speed of 40 m / h.

Next, the tape substrate 10 on which the LMO layer 26 was formed was introduced into a sputtering apparatus and evacuated to 1 × 10 ⁻³ Pa. Then, the CeO ₂ as an evaporation source, a cap layer 28 made of CeO ₂ by RF sputtering, was formed in a thickness of 500 nm.
Specifically, the CeO ₂ film was vapor-deposited by the RF sputtering method in a mixed gas atmosphere of Ar and oxygen at a temperature of about 700 ° C. and about 0.3 Pa, under the conditions of a sputtering output of about 800 W and a wire conveyance speed of 7 m / h. .

Finally, the tape substrate 10 on which the cap layer 28 is formed is introduced into an MOCVD apparatus, and a superconducting layer 30 made of YBCO is formed by MOCVD using YBa ₂ Cu ₃ O _7-λ (hereinafter referred to as YBCO) as an evaporation source. The film was formed with a film thickness of 1000 nm.
Specifically, the deposition of the YBCO film by the MOCVD method was performed under the conditions of a temperature of about 800 ° C. and an O ₂ gas atmosphere at a wire conveyance speed of 10 to 500 m / h or less.

As described above, the angle β formed by the Miller index <010> direction of MgO and the longitudinal direction L becomes 5 degrees, and the a-axis direction or b-axis direction of YBCO intersects the longitudinal direction L, and the a-axis direction or b-axis of YBCO A superconducting wire according to Example 1-1 was obtained in which the angle α formed by the direction and the longitudinal direction L was 5 degrees.
The angles β and α were confirmed by measuring the XRD pole figure of the CeO ₂ layer as the cap layer and the XRD pole point of the superconducting layer. Specifically, the pole figure of the (111) plane of CeO ₂ was measured. Moreover, the pole figure of the (103) plane of YBCO was measured.

<< Examples 1-2 to 1-9 >>
Next, in Examples 1-2 to 1-9, a superconducting wire having a laminated structure of a superconducting layer / CeO ₂ / LMO / IBAD-MgO / GZO / Hastelloy metal substrate was produced in the same manner as in Example 1-1. did. However, in Examples 1-2 to 1-9, the angle δ formed by the vector Z and the vector Y ′ was adjusted to be 13, 18, 22.5, 28, 32, 36, 40, and 45 degrees, respectively. As a result, the angles β formed between the Miller index <010> direction of MgO and the longitudinal direction L become 13, 18, 22.5, 28, 32, 36, 40, and 45 degrees, respectively, and the a-axis direction or b-axis of YBCO The direction intersects the longitudinal direction L, and the angle α between the a-axis direction or the b-axis direction of the YBCO and the longitudinal direction L is 13, 18, 22.5, 28, 32, 36, 40, 45 degrees, respectively. Superconducting wires according to Examples 1-2 to 1-9 were obtained.

<< Comparative Example 1 >>
Next, in Comparative Example 1, a superconducting wire having a laminated structure of superconducting layer / CeO ₂ / LMO / IBAD-MgO / GZO / Hastelloy metal substrate was produced in the same manner as in Example 1-1. However, in Comparative Example 1, the angle δ formed by the vector Z and the vector Y ′ was adjusted to be 0 degree. Thereby, the angle β formed between the Miller index <010> direction of MgO and the longitudinal direction L is 0 degree, and the angle α formed between the a-axis direction or the b-axis direction and the longitudinal direction L is also 0 degree. Such a superconducting wire was obtained (see FIG. 10).

<< Example 2-1 >>
Next, in Example 2-1, a superconducting wire having a laminated structure of superconducting layer / CeO ₂ / IBAD-GZO / Hastelloy substrate as shown in FIG. 6 was produced.

Specifically, a Hastelloy metal substrate as the tape substrate 10 was introduced into an IBAD apparatus and evacuated to 1 × 10 ⁻³ Pa. Then, a forced alignment layer 24 made of GZO (IBAD-GZO) was formed at a temperature of 200 ° C. with a wire conveyance speed of 5 m / h and a film thickness of 1000 nm by IBAD method using GZO as an evaporation source. The assist beam irradiation direction was adjusted so that the angle γ between the vector X and the vector Y shown in FIG. 7 was about 55 degrees and the angle δ between the vector Z and the vector Y ′ was 45 degrees. At this time, the assist ion beam device is installed at an angle of 45 degrees from the width direction of the tape substrate 10 toward the traveling direction.

Next, the tape substrate 10 on which the forced alignment layer 24 was formed was introduced into a sputtering apparatus and evacuated to 1 × 10 ⁻³ Pa. Then, the CeO ₂ as an evaporation source, a cap layer 28 made of CeO ₂ by RF sputtering, was formed in a thickness of 500 nm. Specifically, the CeO ₂ film was vapor-deposited by the RF sputtering method in a mixed gas atmosphere of Ar and oxygen at a temperature of about 700 ° C. and about 0.3 Pa, under the conditions of a sputtering output of about 800 W and a wire conveyance speed of 7 m / h. .

Finally, the tape substrate 10 on which the cap layer 28 was formed was introduced into an MOCVD apparatus, and a superconducting layer 30 made of YBCO was formed with a film thickness of 1000 nm by MOCVD using YBCO as an evaporation source.
Specifically, the deposition of the YBCO film by the MOCVD method was performed under the conditions of a temperature of about 800 ° C. and an O ₂ gas atmosphere at a wire conveyance speed of 10 to 500 m / h or less.

  As described above, the angle β formed by the mirror index <010> direction of IBAD-GZO and the longitudinal direction L becomes 5 degrees, the a-axis direction or b-axis direction of YBCO intersects the longitudinal direction L, and the a-axis direction of YBCO or A superconducting wire according to Example 2-1 was obtained in which the angle α formed by the b-axis direction and the longitudinal direction L was 45 degrees.

<< Examples 2-2 to 2-9 >>
In Examples 2-2 to 2-9, a superconducting wire having a structure of a superconducting layer / CeO ₂ / IBAD-GZO / Hastelloy metal substrate was produced in the same manner as in Example 2-1. However, in Examples 2-2 to 2-9, the angle δ formed by the vector Z and the vector Y ′ was adjusted to be 40, 36, 32, 28, 22.5, 18, 13, and 5 degrees, respectively. As a result, the angles β formed between the Miller index <010> direction of MgO and the longitudinal direction L become 13, 18, 22.5, 28, 32, 36, 40, and 45 degrees, respectively, and the a-axis direction or b-axis of YBCO Example 2 in which the direction intersects the longitudinal direction L, and the angles α formed by the a-axis direction or the b-axis direction and the longitudinal direction L are 40, 36, 32, 28, 22.5, 18, 13, and 5 degrees, respectively. Superconducting wires according to −2 to 2-9 were obtained.

<< Comparative Example 2 >>
Next, in Comparative Example 2, a superconducting wire having a superconducting layer / CeO ₂ / IBAD-GZO / Hastelloy substrate structure was produced in the same manner as in Example 2-1. However, in Comparative Example 2, the angle δ formed by the vector Z and the vector Y ′ was adjusted to be 0 degree. As a result, the angle β between the Miller index <010> direction of MgO and the longitudinal direction L is 45 degrees, and the angle α between the a-axis direction of YBCO or the b-axis direction and the longitudinal direction L is 0 degrees. A superconducting wire according to 2 was obtained.

<Example 3>
Next, in Example 3-1, a superconducting wire having a laminated structure of superconducting layer / CeO ₂ / IBAD-MgO / GZO / Hastelloy metal substrate as shown in FIG. 5 was produced. In FIG. 5, the description of GZO is omitted.

Specifically, a Hastelloy metal substrate as the tape substrate 10 was introduced into a sputtering apparatus and evacuated to 1 × 10 ⁻³ Pa. Then, the bed layer 22 made of GZO was formed by sputtering at a temperature of about 150 ° C. with a wire transport speed of 30 m / h and a film thickness of 100 nm using GZO as an evaporation source.

The tape substrate 10 on which the bed layer 22 made of GZO was formed was introduced into an IBAD apparatus and evacuated to 1 × 10 ⁻³ Pa. Then, the forced alignment layer 24 made of MgO was formed at a temperature of about 150 ° C. with a wire conveyance speed of 80 m / h and a film thickness of 3 nm by using IBAD method using MgO as a deposition source. The assist beam irradiation direction was adjusted so that the angle γ formed by the vector X and the vector Y shown in FIG. 7 was about 45 degrees and the angle δ formed by the vector Z and the vector Y ′ was 40 degrees. At this time, the assist ion beam device is installed at an inclination of 40 degrees from the width direction of the tape substrate 10 toward the traveling direction.

Next, the tape substrate 10 on which the forced alignment layer 24 was formed was introduced into a sputtering apparatus and evacuated to 1 × 10 ⁻³ Pa. Then, the CeO ₂ as an evaporation source, a cap layer 28 made of CeO ₂ by RF sputtering, was formed in a thickness of 500 nm.
Specifically, the CeO ₂ film was vapor-deposited by the RF sputtering method in a mixed gas atmosphere of Ar and oxygen at a temperature of about 700 ° C. and about 0.3 Pa, under the conditions of a sputtering output of about 800 W and a wire conveyance speed of 7 m / h. .

Finally, the tape substrate 10 on which the cap layer 28 was formed was introduced into an MOCVD apparatus, and a superconducting layer 30 made of YBCO was formed with a film thickness of 1000 nm by MOCVD using YBCO as an evaporation source.
Specifically, the deposition of the YBCO film by the MOCVD method was performed under the conditions of a temperature of about 800 ° C. and an O ₂ gas atmosphere at a wire conveyance speed of 10 to 500 m / h or less.

Thus, the angle β formed by the mirror index <010> direction of IBAD-MgO and the longitudinal direction L is 40 degrees, the a-axis direction or b-axis direction of YBCO intersects the longitudinal direction L, and the a-axis direction of YBCO or A superconducting wire according to Example 2-1 was obtained in which the angle α formed by the b-axis direction and the longitudinal direction L was 5 degrees.

<< Examples 3-2 to 3-9 >>
In Examples 3-2 to 3-9, a superconducting wire having a structure of superconducting layer / CeO ₂ / IBAD-MgO / GZO / Hastelloy metal substrate was produced in the same manner as in Example 3-1. However, in Examples 3-2 to 3-9, the angle δ formed by the vector Z and the vector Y ′ was adjusted to 32, 27, 22.5, 17, 13, 9, 5, and 0 degrees, respectively. As a result, the angles β formed between the Miller index <010> direction of MgO and the longitudinal direction L are 32, 27, 22.5, 17, 13, 9, 5, and 0 degrees, respectively, and the a-axis direction or the b-axis of YBCO The direction intersects the longitudinal direction L, and the angle α between the ab direction or the b-axis direction of the YBCO and the longitudinal direction L is 13, 18, 22.5, 28, 32, 36, 40, 45 degrees, respectively. Superconducting wires according to Examples 3-2 to 3-9 were obtained.

<< Comparative Example 3 >>
Next, in Comparative Example 3, a superconducting wire having a structure of superconducting layer / CeO ₂ / IBAD-MgO / GZO / Hastelloy metal substrate was produced in the same manner as in Example 3-1. However, in Comparative Example 3, the angle δ formed by the vector Z and the vector Y ′ was adjusted to be 45 degrees. As a result, the angle β between the Miller index <010> direction of MgO and the longitudinal direction L is 45 degrees, and the angle α between the a-axis direction of YBCO or the b-axis direction and the longitudinal direction L is 0 degrees. 3 was obtained.

<< Evaluation >>
The Ic-strain characteristics were measured for the superconducting wires of each Example and Comparative Example, and εirr (%) was evaluated. Further, the Ic value when ε (strain) = εirr (%) is defined as Ic (εirr), and Ic (εirr) is evaluated and divided by Ic0 when before strain (ε (strain) = 0). The calculated value was obtained. At this time, the length of the sample superconducting wire was 4 cm, the voltage terminal was 1 cm, and the Ic-strain characteristics were measured while pulling in the longitudinal direction of the superconducting wire. A strain gauge was directly attached to the superconducting wire, and the strain was measured at liquid nitrogen temperature.
Here, the Ic-strain characteristic was measured as follows. First, Ic (Ic0) without distortion was measured. Next, by applying a load, Ic measurement and strain measurement were performed in a strain applied state. Thereafter, the load was removed, and Ic measurement was performed again with no load, and it was checked whether it was the same as the first measured Ic0. Furthermore, after increasing the load and performing Ic measurement and strain measurement, the load was unloaded, Ic measurement was performed without a load, and it was examined whether it was the same as Ic0 measured first. Thus, after applying the load and measuring, the process of unloading the load was repeated, and Ic-strain characteristics were obtained by gradually increasing the load.
The minimum strain when the Ic value measured without load after unloading was smaller than the Ic0 measured first was defined as εirr.

  Table 1 summarizes the evaluation results of each εirr (%) and Ic (εirr) / Ic0. FIG. 8 is a graph plotting the relationship between the angle α (°) and εirr (%) based on the evaluation result. Furthermore, FIG. 9 shows a graph in which the relationship between the angle α (°) and Ic (εirr) / Ic0 is plotted based on the evaluation result.

  From the evaluation results shown in Table 1 and FIG. 9, if the a-axis direction or b-axis direction of YBCO intersects the longitudinal direction L of the tape substrate 10, in other words, if the angle α is greater than 0 degrees, Ic (εirr) / Ic0 was found to be high. That is, it was found that a superconducting wire capable of suppressing a decrease in the critical current Ic (εirr) during irreversible strain was obtained.

  Further, it has been found that the angle α is preferably 13 degrees or more. This is because if the angle α is 13 degrees or more, Ic (εirr) / Ic0 increases abruptly as the angle becomes larger than when the angle α is less than 13 degrees.

  Further, it has been found that the angle α is preferably 18 degrees or more. This is because if the angle α is 18 degrees or more, Ic (εirr) / Ic0 is higher than that when the angle α is less than 18 degrees.

  Moreover, it turned out that it is preferable that the angle (alpha) is 36 degrees or less from the evaluation result shown in the above Table 1 and FIG. This is because if the angle α is 36 degrees or less, εirr increases rapidly as the angle decreases as compared to the angle α exceeding 36 degrees.

  Moreover, it turned out that it is preferable that the angle (alpha) is 32 degrees or less. This is because if the angle α is 32 degrees or less, the value of the irreversible strain εirr becomes higher as the angle α is lower than when the angle α is larger than 32 degrees.

1 Superconducting wire 10 Tape substrate (substrate)
20 Intermediate layer 24 Forced orientation layer (oxide layer)
26 LMO layer (oxide layer)
28 Cap layer (oxide layer)
30 Superconducting layer

Claims (5)

A tape-shaped substrate;
A superconducting layer mainly composed of an RE-based superconductor (RE: rare earth element) provided on one surface side in the thickness direction of the substrate and having an a-axis direction or a b-axis direction of a crystal axis intersecting a longitudinal direction of the substrate;
Including at least one oxide layer mainly composed of crystalline oxide whose Miller index <100> direction or Miller index <010> direction intersects the longitudinal direction, and is provided between the substrate and the superconducting layer. Intermediate layer,
I have a,
An angle α formed by the a-axis direction or the b-axis direction and the longitudinal direction is less than 45 degrees and is 13 degrees or more . The angle α is 18 degrees or more.
The superconducting wire according to claim 1 . The angle α is 36 degrees or less.
The superconducting wire according to claim 1 or 2 . The angle α is 32 degrees or less.
Superconducting wire according to any one of claims 1 to 3. The angle formed by the c-axis direction of the crystal axis and the thickness direction is 5 degrees or less.
The superconducting wire according to any one of claims 1 to 4 .