JP2011048914A - Superconducting wire rod and manufacturing method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a superconducting wire rod having highly superconductive properties in a magnetic field, and to provide a manufacturing method of the same. <P>SOLUTION: The superconducting wire rod 1 is so constructed that an yttrium-based superconducting layer 13 is formed on a metal substrate 11 through a medium layer 12 where the yttrium-based superconducting layer includes a lanthanoid element. When a composition of yttrium in the superconducting layer be Y and a composition of the lanthanoid element be L, a composition ratio L/(L + Y) is set to be 0.01 to 0.40. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a superconducting wire used for superconducting equipment such as a superconducting cable and a superconducting magnet, and a manufacturing method thereof, and more particularly, to a Y-based superconducting wire and a manufacturing method thereof.

Conventionally, RE-based superconductors (RE: rare earth elements) are known as a type of high-temperature superconductor that exhibits superconductivity at a liquid nitrogen temperature (77 K) or higher. In particular, an yttrium-based superconductor represented by the chemical formula YBa ₂ Cu ₃ O _7-y (hereinafter, Y-based superconductor or YBCO) is representative.
A superconducting wire using a Y-based superconductor (hereinafter referred to as a Y-based superconducting wire) is generally an intermediate layer on a tape-shaped metal substrate, a layer composed of a Y-based superconductor (hereinafter referred to as a Y-based superconducting layer), a stabilization layer. Have a laminated structure formed in order. This Y-based superconducting wire is formed, for example, by forming a biaxially oriented intermediate layer by an IBAD (Ion Beam Assist Deposition) method on a low magnetic non-oriented metal substrate (for example, Hastelloy (registered trademark)). It is manufactured by forming a Y-based superconducting layer on the layer by a pulsed laser deposition (PLD) or metal organic chemical vapor deposition (MOCVD) method (for example, Patent Documents 1 and 2).

JP 2006-233266 A Special table 2004-536218 gazette

As described above, in the Y-based superconducting wire, YBCO that is the second type superconductor is used for the superconducting layer. When a magnetic field is applied to the second type superconductor, the magnetic field is divided into a string-like quantized magnetic flux, and the quantized magnetic flux enters the superconductor. Although the quantized magnetic flux that has entered the superconductor is stationary when no current flows, the Lorentz force acts when the current flows, so that the quantized magnetic flux starts to move inside the superconductor. When the quantized magnetic flux moves through the superconductor, an induced electromotive force (electric resistance) is generated, so that the zero resistance state (superconducting state) is broken.
Here, it is known that if there are impurities or lattice defects in the superconductor, the quantized magnetic flux does not move and is restrained even if a current flows (so-called pinning effect). That is, in the Y-based superconducting wire, the quantized magnetic flux in the superconducting layer does not move if the restraining force due to the pinning effect (hereinafter referred to as pinning force) is greater than the Lorentz force acting when the current flows, When the external magnetic field increases and the Lorentz force becomes greater than the pinning force, it moves.

Therefore, for a Y-based superconducting wire used for a superconducting cable in which a high current flows and a magnetic field is generated, characteristics in the magnetic field (for example, critical current density characteristics (Jc characteristics)) are important requirements. That is, a Y-based superconducting wire having a high pinning effect is required for superconducting cable applications.
An object of this invention is to provide the superconducting wire which has a high superconducting characteristic in a magnetic field, and its manufacturing method.

Invention of Claim 1 was made | formed in order to achieve the said objective, Comprising: The superconducting wire in which an yttrium-type superconducting layer is formed on the metal substrate through the intermediate | middle layer,
The yttrium-based superconducting layer is configured to contain a lanthanoid element, and when the composition of yttrium in the superconducting layer is Y and the composition of the lanthanoid element is L, the composition ratio L / (L + Y) is 0.01 to It is 0.40.

  The invention according to claim 2 is the superconducting wire according to claim 1, wherein the composition ratio L / (L + Y) is 0.10 to 0.40.

  The invention according to claim 3 is the superconducting wire according to claim 2, wherein the composition ratio L / (L + Y) is 0.20 to 0.30.

  According to a fourth aspect of the present invention, in the superconducting wire according to any one of the first to third aspects, the lanthanoid element contains at least Gd.

The invention according to claim 5 is the superconducting wire according to claim 4, wherein the lanthanoid element is substantially only Gd.
Here, “substantially Gd only” means that a lanthanoid element other than Gd is included unexpectedly. Since lanthanoid elements are difficult to strictly separate, a case where lanthanoid elements other than Gd are mixed in the order of ppm is regarded as “substantially only Gd”.

  The invention described in claim 6 is characterized in that, in the superconducting wire according to claim 4, Gd and Sm are included as the lanthanoid elements.

The invention according to claim 7 is a method for producing a superconducting wire, in which an yttrium-based superconducting layer is formed on the surface of a tape base material having an intermediate layer formed on a metal substrate by metal organic vapor phase epitaxy. ,
As a raw material solution for forming the yttrium-based superconducting layer, when the composition of yttrium is Y and the composition of the lanthanoid element is L, the composition ratio L / (L + Y) is in the range of 0.01 to 0.40. Prepare the organic compound raw materials of yttrium and lanthanoid elements in advance so that the organic compound raw materials of barium and copper are added to this in a predetermined ratio and dissolved in the solvent,
The raw material solution is introduced into a vaporizer to generate a raw material gas, and the generated raw material gas is deposited on the surface of the tape base material in a reaction furnace.

The invention according to claim 8 is a method for producing a superconducting wire material, in which an yttrium-based superconducting layer is formed on the surface of a tape base material having an intermediate layer formed on a metal substrate by metal organic vapor phase epitaxy. ,
As a raw material solution for forming the yttrium-based superconducting layer, yttrium, a lanthanoid element, barium, and a copper organic compound raw material dissolved in a solvent,
When the composition of yttrium is Y and the composition of the lanthanoid element is L, each raw material solution is adjusted so that the composition ratio L / (L + Y) is 0.01 to 0.40 and barium and copper are in a predetermined ratio. A raw material gas is generated by introducing into a vaporizer, and the generated raw material gas is deposited on the surface of the tape substrate in a reaction furnace.

Hereinafter, the background to the completion of the present invention will be described.
As described above, it is known that the pinning effect is enhanced by appropriately introducing impurities and defects into the Y-based superconducting layer, and the critical current density characteristics (hereinafter referred to as Jc characteristics) in a magnetic field can be improved. Therefore, the present inventors have repeatedly studied paying attention to a method of adding impurities in the Y-based superconducting layer in order to realize a high pinning effect.

  FIG. 7 is a diagram showing the crystal structure of YBCO. As shown in FIG. 7, YBCO has a crystal structure in which Y (yttrium) and Ba (barium) are regularly arranged. In such a crystal structure, even if Y is replaced by a lanthanoid element (hereinafter referred to as an L element), the same crystal structure is taken, and thus it is known that the same becomes a superconductor (the RE oxide superconductor described above). . From this, it was estimated that when the superconducting layer made of YBCO was formed, the pinning effect could be expressed without degrading the superconducting characteristics by adding an L-based element as an impurity.

  Here, it is considered that if the L-based element added as an impurity dissolves (substitutes) with Y, the regular crystal structure of YBCO is maintained, so that the superconducting characteristics do not deteriorate. However, if the L-based element is dissolved in Ba, the regular crystal structure is destroyed, so that the superconducting characteristics are deteriorated. Therefore, it was decided to select an element that hardly dissolves with Ba among the L-based elements.

FIG. 8 is a diagram showing the relationship between the ionic radius ratio of Y and L elements and Ba and the solid solution-non-solid solution relationship. The ion radius of Ba ²⁺ is 1.34１．３.
As shown in FIG. 8, Gd (gadolinium), Sm (samarium) and the like have an ionic radius closer to Ba than Y, but are insoluble in Ba. On the other hand, since Nd (neodymium) and La (lanthanum) are dissolved in Ba, they are inappropriate as impurity elements added to YBCO.

From the above, superconducting characteristics (particularly superconducting characteristics in a magnetic field) are improved after selecting an L-based element that is difficult to dissolve in Ba (for example, Gd or Sm) as an impurity element to be added to YBCO. The amount of impurities (composition ratio of L-based elements) to be determined was experimentally determined and defined in the present invention.
Since the superconducting wire according to the present invention does not depend on the manufacturing method in principle, it can be applied when the superconducting layer is formed by the MOCVD method or the sintering method. The present inventors control the composition ratio between yttrium and a lanthanoid element when forming a superconducting layer by MOCVD, thereby generating a pin by the action of an L element, that is, high Jc characteristics in a magnetic field. A superconducting wire that shows

  According to the present invention, a superconducting wire having high superconducting properties in a magnetic field is provided. Therefore, by applying the superconducting wire according to the present invention, it is possible to increase the current of the superconducting cable.

It is a figure which shows the laminated structure of the superconducting wire which concerns on embodiment. It is a figure which shows schematic structure of the general MOCVD apparatus for forming into a film on a elongate tape base material. It is a figure which shows the Jc characteristic in the magnetic field of the superconducting wire which concerns on Example 1. FIG. It is a figure shown about the magnetic field incident angle at the time of measuring a Jc characteristic. It is a figure which shows the Jc characteristic in the non-magnetic field of the superconducting wire which concerns on Example 2 (77K, 0T). It is a figure which shows the Jc characteristic in the magnetic field (77K, 3T) of the superconducting wire which concerns on Example 2. FIG. It is a figure which shows the crystal structure of YBCO. It is a figure which shows the ionic radius ratio of Y and L type | system | group element, and Ba, and the relationship of solid solution-non-solid solution.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 is a view showing a laminated structure of superconducting wires according to this embodiment.
As shown in FIG. 1, the Y-based superconducting wire 1 has a laminated structure in which an intermediate layer 12, a superconducting layer 13, and a stabilizing layer 14 are formed in this order on a tape-like metal substrate 11.
In the present embodiment, the metal substrate 11 is a low-magnetic non-oriented metal substrate (for example, Hastelloy (registered trademark)). The intermediate layer 12 includes a biaxially oriented layer (for example, yttria stabilized zirconia) for orienting the crystals of the superconducting layer 13 in a certain direction. This biaxial alignment layer is formed by, for example, the IBAD method.
The superconducting layer 13 is a Y-based superconducting layer made of a Y-based superconductor, and is formed by, for example, the MOCVD method. On the upper surface of the superconducting layer 13, a stabilizing layer 14 made of silver is formed by sputtering, for example.

  In this embodiment, the L-based element Gd is added as an impurity to the Y-based superconductor constituting the superconducting layer 13. The amount of Gd is adjusted so that the composition ratio Gd / (Gd + Y) of Y and Gd satisfies 0.01 to 0.40 (molar ratio). By forming the superconducting layer 13 by MOCVD, the composition ratio of Y and Gd can be controlled relatively easily.

FIG. 2 is a diagram showing a schematic configuration of a general MOCVD apparatus for forming a film on a long tape base material. As shown in FIG. 2, the MOCVD apparatus 100 includes a raw material supply unit 101, a vaporizer 102, a reaction furnace 103, and a base material transport unit 104.
The raw material supply unit 101 supplies a raw material solution and a carrier gas such as Ar to the vaporizer 102. The vaporizer 102 sprays the raw material solution into the supplied carrier gas to generate the raw material gas. The generated source gas is introduced into the reaction furnace 103 through an introduction pipe.
The reaction furnace 103 deposits the introduced source gas on the surface of the tape substrate 110 to form a superconducting layer. The substrate conveyance unit 104 moves the tape substrate 110 at a predetermined speed in the reaction furnace 103. That is, the superconducting layer 13 is formed while moving the tape substrate 110. The temperature of the tape base 110 is controlled by a heater (not shown).

The superconducting layer 13 of the superconducting wire 1 according to the embodiment can be formed by the MOCVD apparatus 100 shown in FIG. As the tape base 110, for example, a film in which an alignment intermediate layer 12 is formed by an IBAD method on a non-oriented metal substrate (for example, Hastelloy) 11 having a thickness of 100 μm, a width of 10 mm, and a length of 200 m is used.
In the raw material solution, an organic compound raw material of Y and Gd (for example, a tetramethylheptanedionate compound) is used in advance so that the composition ratio Gd / (Gd + Y) of Y and Gd is in the range of 0.01 to 0.40. The organic compound raw materials of Ba and Cu are added to this at a desired ratio and dissolved in THF (tetrahydrofuran) as a solvent.

The raw material solution having the above-described configuration is supplied from the raw material supply unit 101 to the vaporizer 102 to generate a raw material gas. The tape base material 110 is heated at 700 to 900 ° C. while the tape base material 110 is conveyed into the reaction furnace 103 at a predetermined speed. Then, a source gas is jetted onto the surface of the tape substrate 110, and YBCO to which Gd is added as an impurity is formed.
Here, the composition ratio of the organic compound raw materials of Y and Gd is maintained up to the product. That is, if the composition ratio Gd / (Gd + Y) of the organic compound raw material of Y and Gd is 0.25 to 0.30, the composition ratio Gd / (Gd + Y) of Y and Gd in YBCO added with Gd as a product is also 0.25 to 0.30.

[Example 1]
In Example 1, the critical current density characteristic (Jc characteristic) when the composition ratio Gd / (Gd + Y) of Y and Gd in the superconducting layer 13 was set to 0.35 was examined.
FIG. 3 is a graph showing the Jc characteristic in the magnetic field of the superconducting wire according to the first embodiment. In FIG. 3, the horizontal axis represents the magnetic field incident angle θ with respect to the superconducting layer 13 in FIG. The measurement temperature is 77K and the applied magnetic field is 3T (Tesla).
As shown in FIG. 3, the Jc characteristic of the Gd-added YBCO according to Example 1 is higher than the Jc characteristic of the Gd-free YBCO according to the comparative example regardless of the direction of the applied magnetic field. . In particular, the improvement in current value at a magnetic field incident angle of 90 ° was about 50%.

[Example 2]
In Example 2, the Jc characteristic when the composition ratio of Y and Gd was changed was examined. When the composition ratio Gd / (Gd + Y) = 0 of Y and Gd, Gd-free YBCO is obtained, and when Gd / (Gd + Y) = 1, GdBCO is obtained.
FIG. 5 is a diagram showing the Jc characteristic of the superconducting wire according to Example 2 in a non-magnetic field (77K, 0T), and FIG. 6 shows the Jc characteristic of the superconducting wire according to Example 2 in a magnetic field (77K, 3T). FIG.
As shown in FIG. 5, there was a tendency that the composition ratio Gd / (Gd + Y) of Y and Gd had a peak in the vicinity of 0.22 in the absence of a magnetic field. Further, as shown in FIG. 6, in the magnetic field, the peak position shifted to around 0.28, but almost the same tendency was obtained.
From this, it was found that the Jc characteristics can be improved even in a magnetic field by controlling the composition ratio of Y and Gd within a certain range. Specifically, the composition ratio Gd / (Gd + Y) of Y and Gd was set to 0.01 to 0.40, whereby the Jc characteristics could be improved as compared with the case where no Gd was added (Gd / (Gd + Y) = 0). Moreover, high Jc characteristics can be realized by setting the composition ratio Gd / (Gd + Y) of Y and Gd to 0.10 to 0.40, and even higher Jc characteristics can be realized by setting it to 0.20 to 0.30. It was.

In the embodiment, the Y-based superconducting layer 13 includes an L-based element, and the composition ratio L / (L + Y) of Y and L-based element (Gd in the embodiment) in the superconducting layer is 0.01 to 0.00. 40.
The composition ratio L / (L + Y) between Y and the L-based element is preferably in the range of 0.10 to 0.40, and more preferably in the range of 0.20 to 0.30.
Thus, by adjusting the composition of Y and L elements in the Y-based superconducting layer, it is possible to provide a superconducting wire having high superconducting characteristics (particularly Jc characteristics) in a magnetic field. And by applying such a superconducting wire, it is possible to increase the current of the superconducting cable.

As mentioned above, although the invention made by this inventor was concretely demonstrated based on embodiment, this invention is not limited to the said embodiment, It can change in the range which does not deviate from the summary.
In the above embodiment, the L-based element to be added is substantially only Gd. However, it is sufficient that at least Gd is included, and it is configured to include Gd and other L-based elements (excluding Nd and La). It may be.
The reason why it contains at least Gd is that it is insoluble in Ba and is less likely to break the crystal structure, and it is inexpensive among L-based elements and can suppress the production cost of superconducting wires. For the same reason, the L-based element to be added may include Gd and Sm.

Further, as the metal substrate 11 of the superconducting wire 1, a metal (for example, Ni—W) oriented by orientation heat treatment in a reducing atmosphere may be used instead of the non-oriented substrate. In this case, an intermediate layer 12 for preventing the diffusion of Ni or the like from the metal substrate 11 or improving the orientation is formed on the metal substrate 11 by, for example, sputtering or ion beam evaporation.
That is, the present invention relates to the composition of the Y-based superconducting layer constituting the superconducting wire, and the combination of the metal substrate and the intermediate layer is not particularly limited.

In the MOCVD apparatus 100 according to the embodiment, the raw material solution is mixed in advance in the raw material supply unit 101 and accommodated in one raw material container, but each of the Gd, Y, Ba, and Cu raw material containers is provided separately. It is good also as a structure.
Specifically, as a raw material solution for forming the Y-based superconducting layer 13, organic compound raw materials of Gd, Y, Ba, and Cu, which are dissolved alone in THF, are stored in separate raw material containers. These are flow-adjusted by a liquid mass flow controller so as to have a desired ratio, merged, and then supplied to the vaporizer. At this time, the flow rate is adjusted so that the composition ratio Gd / (Gd + Y) of Y and Gd is 0.01 to 0.40. And the source gas produced | generated with the vaporizer is vapor-deposited on the surface of the said tape base material in a reaction furnace.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 Superconducting wire 11 Metal substrate 12 Intermediate layer 13 Y-based superconducting layer 14 Stabilization layer

Claims (8)

A superconducting wire in which an yttrium-based superconducting layer is formed on a metal substrate via an intermediate layer,
The yttrium-based superconducting layer is configured to contain a lanthanoid element, and when the composition of yttrium in the superconducting layer is Y and the composition of the lanthanoid element is L, the composition ratio L / (L + Y) is 0.01 to A superconducting wire characterized by 0.40.   The superconducting wire according to claim 1, wherein the composition ratio L / (L + Y) is 0.10 to 0.40.   The superconducting wire according to claim 2, wherein the composition ratio L / (L + Y) is 0.20 to 0.30.   The superconducting wire according to any one of claims 1 to 3, wherein the lanthanoid element contains at least Gd.   The superconducting wire according to claim 4, wherein the lanthanoid element is substantially only Gd.   The superconducting wire according to claim 4, wherein the lanthanoid element includes Gd and Sm. A method for producing a superconducting wire, in which an yttrium-based superconducting layer is formed by metal organic vapor phase epitaxy on the surface of a tape base material in which an intermediate layer is formed on a metal substrate,
As a raw material solution for forming the yttrium-based superconducting layer, when the composition of yttrium is Y and the composition of the lanthanoid element is L, the composition ratio L / (L + Y) is in the range of 0.01 to 0.40. Prepare the organic compound raw materials of yttrium and lanthanoid elements in advance so that the organic compound raw materials of barium and copper are added to this in a predetermined ratio and dissolved in the solvent,
A method for producing a superconducting wire, comprising introducing a raw material solution into a vaporizer to generate a raw material gas, and depositing the generated raw material gas on the surface of the tape base material in a reaction furnace. A method for producing a superconducting wire, in which an yttrium-based superconducting layer is formed by metal organic vapor phase epitaxy on the surface of a tape base material in which an intermediate layer is formed on a metal substrate,
As a raw material solution for forming the yttrium-based superconducting layer, yttrium, a lanthanoid element, barium, and a copper organic compound raw material dissolved in a solvent,
When the composition of yttrium is Y and the composition of the lanthanoid element is L, each raw material solution is adjusted so that the composition ratio L / (L + Y) is 0.01 to 0.40 and barium and copper are in a predetermined ratio. A method for producing a superconducting wire, comprising introducing a vaporizer into a raw material gas, and depositing the generated raw material gas on a surface of the tape base material in a reaction furnace.

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