JP2010123516A - Method of manufacturing substrate for oxide superconductor, method of manufacturing oxide superconductor, and device for forming cap layer for oxide superconductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten time and to reduce cost which formation of a cap layer takes, thereby to provide a method of manufacturing a substrate for an oxide superconductor which can manufacture an oxide superconductor with sufficient productivity, to provide a method of manufacturing an oxide superconductor, and to provide a device for forming a cap layer for an oxide superconductor used by each manufacturing method. <P>SOLUTION: In the method of manufacturing the substrate for the oxide superconductor, a reactivity DC sputtering method using metal targets 14a, 15a is used as a method of forming cap layer on an IBAD substrate 7. A cap layer to be formed is for example, is a CeO<SB>2</SB>layer. When a cap layer is formed, two or more metal targets 14a, 15a are prepared along a run system 11, and it is desirable to establish the temperature of the IBAD substrate 7 and the oxygen concentration of a gas introduced into a deposition space in a predetermined range. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a base material used for an oxide superconductor, a method for manufacturing an oxide superconductor, and an apparatus for forming a cap layer for an oxide superconductor.

RE-123-based oxide superconductor (REBa ₂ Cu ₃ O _7-X : RE is a rare earth element including Y) is considered as a very promising material for practical use because it exhibits superconductivity at a liquid nitrogen temperature or higher, There is a strong demand for processing this into a wire and using it as a conductor for power supply.
As a conductor used for such a RE-123 oxide superconducting conductor, as shown in FIG. 3, an intermediate layer formed on a tape-like metal substrate 101 by an IBAD (Ion-Beam-Assisted Deposition) method. 102, and a structure in which a cap layer 103 and an oxide superconducting layer 104 are stacked in this order are known (for example, see Patent Document 1).

In this oxide superconducting conductor, the intermediate layer 102 and the cap layer 103 are provided in order to control the crystal orientation of the oxide superconducting layer 104.
That is, the oxide superconductor has an electric anisotropy that it is easy for electricity to flow in the a-axis direction and b-axis direction of its crystal axis, but it is difficult for electricity to flow in the c-axis direction. Therefore, when a conductor is formed using this oxide superconductor, the oxide superconducting layer 104 needs to have the a-axis or b-axis oriented in the direction in which electricity flows and the c-axis oriented in other directions. is there.

Here, the IBAD method is widely known as a technique for forming the intermediate layer 102 used in this kind of oxide superconducting conductor, and the intermediate layer formed by the IBAD method includes a coefficient of thermal expansion, a lattice constant, and the like. For example, MgO, YSZ (yttria-stabilized zirconium), SrTiO _3, or the like has a physical characteristic value that is an intermediate value between the metal substrate 101 and the oxide superconducting layer 104.
Such an intermediate layer 102 functions as a buffer layer that alleviates the difference in physical properties between the metal substrate 101 and the oxide superconducting layer 104. Further, by being formed by the IBAD method, the crystal of the intermediate layer 102 has a high in-plane orientation degree, and functions as an orientation control film that controls the orientation of the cap layer 103. Hereinafter, the orientation mechanism of the intermediate layer 102 formed by the IBAD method will be described.

  As shown in FIG. 4, the intermediate layer forming apparatus based on the IBAD method has a traveling system for traveling the metal substrate 101 in the longitudinal direction thereof, and the surface thereof is inclined with respect to the surface of the metal substrate 1. Target 201, a sputter beam irradiation apparatus 202 that irradiates the target 201 with ions, and an ion source 203 that irradiates the surface of the metal substrate 101 with ions (mixed ions of rare gas ions and oxygen ions) from an oblique direction. These parts are arranged in a vacuum vessel (not shown).

In order to form the intermediate layer 102 on the metal substrate 101 by this intermediate layer forming apparatus, the inside of the vacuum vessel is set to a reduced pressure atmosphere, and the sputter beam irradiation apparatus 202 and the ion source 203 are operated. Thereby, the target 201 is irradiated with ions from the sputter beam irradiation apparatus 202, and the constituent particles of the target 201 are blown off and deposited on the metal substrate 101. At the same time, mixed ions of rare gas ions and oxygen ions are emitted from the ion source 203 and are incident on the surface of the metal substrate 101 at a predetermined incident angle (θ).
In this way, by irradiating ions at a predetermined incident angle while depositing the constituent particles of the target 201 on the surface of the metal substrate 101, the specific crystal axis of the formed sputtered film is in the ion incident direction. The c axis is oriented in a direction perpendicular to the surface of the metal substrate, and the a axis and the b axis are oriented in a certain direction in the plane. For this reason, the intermediate layer 102 formed by the IBAD method has a high degree of in-plane orientation.

On the other hand, the cap layer 103 is epitaxially grown by being formed on the surface of the intermediate layer 102 in which the in-plane crystal axes are oriented as described above, and then grows laterally, so that the crystal grains are self-oriented in the in-plane direction. Composed of a possible material, for example CeO ₂ . Since the cap layer 103 is self-orientated in this way, a higher in-plane orientation degree than that of the intermediate layer 102 can be obtained.
Therefore, when the oxide superconducting layer 104 is formed on the metal substrate 101 via the intermediate layer 102 and the cap layer 103, the oxidation is performed so as to match the crystal orientation of the cap layer 103 having a high degree of in-plane orientation. Since the superconducting layer 104 is epitaxially grown, the oxide superconducting layer 104 having excellent in-plane orientation and a large critical current density can be obtained.
JP 2004-71359 A

By the way, when manufacturing such an oxide superconducting conductor, the cap layer 103 is generally formed by a PLD (Pulsed Laser Deposition) method. Hereinafter, an example of a PLD apparatus that forms the cap layer 103 by the PLD method will be described.
The PLD apparatus 301 shown in FIG. 5 moves the cap layer 103 on the surface of the IBAD substrate 105 in the longitudinal direction while running the tape-shaped substrate (IBAD substrate 105) provided with the intermediate layer 102 by the IBAD method. This is an apparatus for continuous film formation in the direction.

The PLD apparatus 301 includes a traveling system 302 in which the IBAD base material 105 travels a plurality of times along a racetrack-like route, and a CeO ₂ target (oxide target) disposed to face the surface of the intermediate layer 102 of the IBAD base material 105. 303) and a laser light source 304 for irradiating the CeO ₂ target 303 with an excimer laser (pulse laser). In the PLD apparatus 301, is irradiated with excimer laser to CeO ₂ target 303, the active species from CeO ₂ target 303 (atoms, molecules, ions, clusters, etc.) are released and deposited on the intermediate layer 102 surface of IBAD substrate 105 . As a result, a target material deposition layer (CeO ₂ cap layer 103) is formed on the intermediate layer 102.
However, the PLD method used for forming the CeO ₂ cap layer 103 has the following drawbacks.

First, in the PLD method, since an ultraviolet laser having a large absorption coefficient is used as a laser, the target is limited to one that absorbs the ultraviolet laser. For this reason, when the CeO ₂ cap layer 103 is formed, a single metal target cannot be used, and the oxide can only be used as a target. However, since an oxide target such as CeO ₂ is easily broken, it must be handled with care. For example, if the laser output is increased too much to obtain a high film formation rate, the oxide target itself is broken by the laser. There is a problem that there is a high risk of being lost.

Further, in the PLD method, the output of the laser oscillator is limited to about 300 W at the maximum, so it is difficult to increase the film formation rate beyond the current rate. For this reason, for example, when the CeO ₂ cap layer 103 having a thickness of 0.5 μm is formed, the traveling speed of the IBAD base material 105 can be increased only to about 60 m / h, and this causes the production of the oxide superconductor. There is a problem that it is difficult to increase efficiency more than ever.
In addition, since a rare gas used as a laser gas deteriorates with time in a PLD apparatus, it is necessary to suppress the operation time to about several tens of hours, and continuous film formation cannot be performed for a long time. For this reason, there is a problem that it is difficult to make the film thickness of the cap layer 103 longer than before.
Further, the laser oscillator itself is very expensive, and the rare gas used as the laser gas is also extremely expensive. For this reason, if the PLD method is used as a method of forming the cap layer 103, the manufacturing cost of the oxide superconductor is increased.

  When manufacturing an oxide superconducting conductor comprising an oxide superconducting layer, a cap layer, an intermediate layer, and a substrate, the present invention can form a cap layer having a high degree of orientation in a long shape, and a cap. A method for producing a substrate for an oxide superconductor capable of producing an oxide superconductor with high productivity by shortening the time required for forming a layer and reducing the cost, and an oxide superconductor using the same. It is an object of the present invention to provide a manufacturing method and an apparatus for forming a cap layer for an oxide superconducting conductor.

The present invention has the following configuration in order to solve the above problems.
The manufacturing method of the base material for oxide superconducting conductors of the present invention includes a base material, an intermediate layer deposited on the base material by an ion beam assist (IBAD) method, and a cap layer formed on the intermediate layer. In manufacturing a base material for an oxide superconducting conductor in which an oxide superconducting layer is formed on the cap layer, the cap layer is formed by a reactive DC sputtering method using a metal target.
The manufacturing method of the base material for oxide superconducting conductors of this invention is characterized by heating the said base material to 500-800 degreeC, when forming the said cap layer.
In the method for manufacturing a base material for an oxide superconducting conductor according to the present invention, a gas introduced into a film formation space for forming the cap layer is a mixed gas composed of a carrier gas and an oxygen gas, and the oxygen concentration of the mixed gas is 5 to 5. It is characterized by being 50%.

Method of manufacturing an oxide superconducting conductor substrate of the present invention is characterized in that the cap layer and CeO _2.
The method for producing an oxide superconducting conductor of the present invention is characterized in that an oxide superconducting layer is formed on the cap layer obtained as described above.

  An apparatus for forming a cap layer for an oxide superconducting conductor according to the present invention includes an IBAD substrate having an elongated substrate and an intermediate layer deposited on the substrate by an ion beam assist (IBAD) method, and the IBAD An apparatus for forming a cap layer for an oxide superconducting conductor that forms the cap layer of an oxide superconducting conductor comprising a cap layer formed on the intermediate layer of a base material and an oxide superconducting layer formed on the cap layer. A traveling system in which the IBAD substrate travels, a substrate feeding means for feeding out the IBAD substrate, a substrate winding means for winding up the IBAD substrate discharged from the traveling system, and the traveling system A metal target disposed opposite to the intermediate layer surface of the IBAD base material traveling on the power source, a power source for applying a DC voltage to the metal target, and between the IBAD base material and the metal target. , And a gas supply means for supplying a carrier gas and the reactive gas, onto the middle layer of the IBAD substrate, and forming the cap layer by reactive DC sputtering.

The apparatus for forming a cap layer for an oxide superconducting conductor according to the present invention is characterized by having a heating means for heating the IBAD base material forming the cap layer to 500 to 800 ° C.
An apparatus for forming a cap layer for an oxide superconducting conductor according to the present invention is provided with a traveling system that forms an outward path and a return path for traveling of an IBAD base material as the traveling system, and includes at least two of the metal targets. Is disposed opposite to the intermediate layer surface of the IBAD substrate traveling on the forward path, and the other target is disposed opposite to the intermediate layer surface of the IBAD substrate traveling on the return path. It was set up.
In the apparatus for forming a cap layer for an oxide superconducting conductor according to the present invention, a plurality of racetrack-like traveling paths having a forward path and a return path are provided in parallel and spaced apart from each other as a pair as the traveling system. A traveling system is configured, a forward target is installed facing an area where a plurality of the forward paths are arranged side by side, a return target is installed facing an area where a plurality of the backward paths are installed side by side, and the forward path And a heating means capable of heating the base material that travels on the forward path and the base material that travels on the return path.

In the present invention, a base material for an oxide superconducting conductor comprising a cap layer, an intermediate layer, and a base material, and an oxide in which an oxide superconducting layer is formed on the cap layer of the base material for an oxide superconducting conductor. When manufacturing a superconductor, a cap layer is formed by a reactive DC sputtering method.
In the reactive DC sputtering method, the target may be any target that can be sputtered by ion irradiation, and a metal target can be used. Since the metal target is harder to break than the oxide target, it can be easily handled and is less likely to be wasted due to breakage. For this reason, it is advantageous to reduce the manufacturing cost of the oxide superconducting conductor base material and the oxide superconducting conductor by forming the cap layer at a high film formation rate by the DC sputtering method.

  Further, since the direct current power source used in the reactive DC sputtering method can easily supply a high output (about 2 kW to 16 kW) to the sputtering electrode, the sputtering efficiency of the target can be easily increased. For this reason, in the reactive DC sputtering method, a larger film formation rate can be obtained than in the PLD method, and the cap layer can be formed with a sufficient film thickness while the IBAD substrate is traveling at a relatively high speed. . As a result, it is possible to improve the productivity of the oxide superconductor base material and the oxide superconductor.

  In addition, in the reactive DC sputtering method, since the film formation rate is large as described above, the crystal grains can be grown at high speed in the plane direction in the process of selective growth of the sputtered film, so that the in-plane orientation degree is more excellent. A cap layer can be formed. When an oxide superconductor is formed on such a cap layer, the oxide superconducting layer grows epitaxially so as to match the crystal orientation of the cap layer having a high in-plane orientation. A high-density oxide superconducting layer can be obtained.

Furthermore, the reactive DC sputtering method does not use expensive parts such as a laser oscillator, and the gas to be used is Ar or oxygen gas. Therefore, the operating cost and the maintenance cost are low. For this reason, it is advantageous when aiming at the reduction of the manufacturing cost of the base material for oxide superconductors, and an oxide superconductor.
Moreover, this reactive DC sputtering method does not have the problem of gas deterioration like the PLD method, and can be operated for a long time. For this reason, the cap layer can be continuously formed over a long time, and a long cap layer can be easily formed. As a result, it is possible to lengthen the base material for the oxide superconducting conductor and the oxide superconducting conductor.

Embodiments of the present invention will be described below.
<< Oxide superconductor base material and oxide superconductor >>
First, the base material for an oxide superconducting conductor and the oxide superconducting conductor manufactured by the manufacturing method of the present invention will be described.
FIG. 1 shows a schematic longitudinal cross-sectional structure of a base material for an oxide superconducting conductor and an oxide superconducting conductor manufactured by the manufacturing method of the present invention.
As shown in FIG. 1, the base material 1 for oxide superconducting conductors of the present invention includes an IBAD intermediate layer 3 including an intermediate layer 3 formed on a metal base 2 and a cap layer 4 thereon. The oxide superconducting conductor 5 of the present invention has a basic structure in which an oxide superconducting layer 6 is formed on the cap layer 4 of the base material 1 for the oxide superconducting conductor. . Note that the present invention can be applied to a structure in which a diffusion prevention layer, a base layer, and the like are formed on the metal substrate 2 and then the IBAD intermediate layer 3 is formed.
Hereinafter, the material which comprises each said layer is explained in full detail.

<Metal base material>
As a material constituting the metal substrate 2, metals such as Cu, Ni, Ti, Mo, Nb, Ta, W, Mn, Fe, and Ag, which are excellent in strength and heat resistance, or alloys thereof can be used. . Particularly preferred are stainless steel, hastelloy, and other nickel-based alloys that are excellent in corrosion resistance and heat resistance. Alternatively, in addition to these, a ceramic substrate, an amorphous alloy substrate, or the like may be used.

<Intermediate layer>
The intermediate layer 3 is a deposited film formed by the IBAD method, and functions as a buffer layer that alleviates the difference in physical properties (thermal expansion coefficient, lattice constant, etc.) between the metal substrate 2 and the oxide superconducting layer 6. At the same time, it functions as an orientation control film for controlling the orientation of the cap layer 4 formed thereon.
As the material constituting the intermediate layer 3, a material whose physical characteristics show an intermediate value between the metal substrate 2 and the oxide superconducting conductor film 6 is used. Examples of the material of the intermediate layer 3 include yttria-stabilized zirconium (YSZ), MgO, SrTiO ₃ , Gd ₂ Zr ₂ O _{7, and the} like. An appropriate compound having a mold structure or a fluorite structure can be used. Among these, it is preferable to use YSZ, Gd ₂ Zr ₂ O ₇ , or MgO as the material of the intermediate layer 3. In particular, Gd ₂ Zr ₂ O ₇ and MgO are particularly suitable as the material for the intermediate layer because ΔΦ (FWHM: full width at half maximum), which is an index representing the degree of orientation in the IBAD method, can be reduced.

Although the film thickness of the intermediate | middle layer 3 can be selected from the range of 5-2000 nm and the range of 50-1000 nm, for example, it is not restrict | limited to these ranges.
If the film thickness of the intermediate layer 3 exceeds 1000 nm, the deposition time of the IBAD method used as the film formation method of the intermediate layer 3 is relatively low, so that the film formation time of the intermediate layer 3 becomes long. When the thickness of the intermediate layer 3 exceeds 2000 nm, the surface roughness of the intermediate layer 3 increases, and the critical current density of the oxide superconducting conductor 5 may be reduced.
On the other hand, if the film thickness of the intermediate layer 3 is less than 5 nm, it becomes difficult to control the crystal orientation of the intermediate layer itself, and it becomes difficult to control the degree of orientation of the cap layer 4 formed thereon. It becomes difficult to control the degree of orientation of the oxide superconducting layer 6 formed on 4. As a result, the oxide superconducting conductor 5 may have an insufficient critical current.

<Cap layer>
The cap layer 4 has a function of controlling the orientation of the oxide superconducting layer 6 provided thereon, and also diffuses the elements constituting the oxide superconducting layer 6 into the intermediate layer 3 and gas used during film formation. And a function of suppressing the reaction between the intermediate layer 3 and the like.
The cap layer 4 is formed through a process of epitaxial growth with respect to the surface of the intermediate layer 3, and then grain growth (overgrowth) in the lateral direction (plane direction), and crystal grains are selectively grown in the in-plane direction. What is film | membrane is preferable. The cap layer 4 that is selectively grown in this way has a higher in-plane orientation than the intermediate layer 3.
The material constituting the cap layer 4 is not particularly limited as long as it can exhibit such a function. For example, CeO ₂ , Y ₂ O ₃ , Al ₂ O ₃ or the like is preferably used.
When CeO ₂ is used as the constituent material of the cap layer 4, the cap layer 4 does not have to be entirely composed of CeO ₂ , and Ce-M in which part of Ce is substituted with another metal atom or metal ion. -O type oxide may be included.

The appropriate film thickness of the cap layer 4 varies depending on the constituent material. For example, when the cap layer 4 is composed of CeO ₂ , examples thereof include a range of 50 to 5000 nm and a range of 100 to 5000 nm. If the film thickness of the cap layer 4 is out of these ranges, a sufficient degree of orientation may not be obtained.
The manufacturing method of the present invention is characterized in that the cap layer 4 is formed by a reactive DC sputtering method using a metal target. The method for forming the cap layer 4 will be described in detail later.

<Oxide superconducting layer>
As a material for the oxide superconducting layer 6, an RE-123 oxide superconductor (REBa ₂ Cu ₃ O _7-X : RE is a rare earth element such as Y, La, Nd, Sm, Eu, Gd, etc.) is used. it can. Y123 (YBa ₂ Cu ₃ O _7-X ) or Gd123 (GdBa ₂ Cu ₃ O _7-X ) or the like is preferable as the RE-123-based oxide.

<< Base material for oxide superconducting conductor and method for producing oxide superconducting conductor >>
Next, the manufacturing method of the base material for oxide superconductors which concerns on this invention is demonstrated.
First, a long metal base 2 is prepared, and an intermediate layer 3 is formed on the metal base 2 by an IBAD method. Hereinafter, the laminate in which the intermediate layer 3 is formed on the metal substrate 2 is referred to as “IBAD substrate 7”.
Next, the cap layer 4 is formed on the intermediate layer 3 of the IBAD substrate 7 by reactive DC sputtering using a metal target. Hereinafter, a cap layer forming apparatus used for forming the cap layer 4 will be described.

<Cap layer forming device>
FIG. 2 is a schematic perspective view showing a cap layer forming apparatus (capacitor forming apparatus for oxide superconductor) according to an embodiment of the present invention.
A cap layer forming apparatus 10 shown in FIG. 2 is an apparatus capable of continuously forming a cap layer 4 in the running direction on the intermediate layer 3 while running the IBAD substrate 7 in the longitudinal direction.
The cap layer forming apparatus 10 is a film forming apparatus provided in a form accommodated in a vacuum chamber (abbreviated as “A” in FIG. 2), and includes a traveling system 11 on which the IBAD base material 7 travels, and a traveling system 11. (Substrate feeding means) 12 such as a feeding reel for feeding out the IBAD base material 7, (Base material winding means) 13 such as a winding reel for winding up the IBAD base material 7 discharged from the traveling system 11, and an IBAD base A first film forming system 14 and a second film forming system 15 for forming the cap layer 4 on the material 7 and a heater (heating means) 16 for heating the IBAD base material 7 are provided.

  The vacuum chamber A used in this form is a container that partitions the outside from the film formation space, has airtightness, and has pressure resistance because the inside is in a high vacuum state. The vacuum chamber is connected to a gas supply means B for introducing a carrier gas and a reactive gas into the vacuum chamber and an exhaust means C for exhausting the gas in the vacuum chamber. In FIG. And exhaust means C are abbreviated.

The gas supply means B includes a gas supply source that supplies a mixed gas of a carrier gas and a reactive gas, a pipe that connects the gas supply source and the vacuum chamber, a mass flow controller that is provided in the middle of the pipe, and the like. The mixed gas supplied from the supply source is introduced into the vacuum chamber A while the flow rate is adjusted by the mass flow controller.
The carrier gas may be an inert gas and is not particularly limited. For example, argon gas is used.
The reaction gas is appropriately selected according to the composition of the target cap layer. For example, when forming an oxide layer such as a CeO ₂ layer, oxygen gas is used.

When oxygen gas is used as the reaction gas, the proportion (volume ratio) of oxygen gas in the mixed gas is preferably 5 to 50%, and more preferably 10 to 20%.
When the ratio of the reaction gas is less than 5%, the degree of oxidation of the sputtered film formed becomes low, and the cap layer 4 having a desired function may not be obtained. Further, when the proportion of the reactive gas is larger than 50%, the proportion of the carrier gas is reduced accordingly, so that the quality of the plasma to be generated when performing DC sputtering is deteriorated, and the sputtering of each target 14a, 15b is performed. In order to reduce the efficiency and form the cap layer 4 with a sufficient thickness, it is necessary to run the IBAD substrate 7 at a relatively low speed. As a result, the productivity of the oxide superconductor base material 1 may be reduced.

  The exhaust means C includes a vacuum pump, pipes connecting the vacuum pump and the vacuum chamber, valves, and the like. When the vacuum pump is depressurized or the cap layer 4 is formed by operating the vacuum pump, the cap C After forming the layer 4, the gas in the vacuum chamber is evacuated at a predetermined flow rate.

  The delivery reel 12 and the take-up reel 13 are spaced apart from each other. Each of the reels 12 and 13 has an end portion of the long IBAD base material 7 attached thereto. The IBAD base material 7 is wound around the delivery reel 12. In addition, the IBAD base material 7 between the delivery reel 12 and the take-up reel 13 is wound around a first roll 17 and a second roll 18 of the traveling system 11 to be described later (seven rounds in this embodiment). ing.

In the apparatus of the present embodiment, the traveling system 11 includes a first roll 17 and a second roll 18 that are arranged to face each other.
The first roll 17 is provided between the delivery reel 12 and the take-up reel 13, and the second roll 18 is disposed opposite to the first roll 17 so as to be separated from the first roll 17. In this embodiment, the first roll 17 and the second roll 18 are arranged with their rotation center axes in the vertical direction and their roll peripheral surfaces facing sideways, and the peripheral surface of the first roll 17 and the second roll 18. A tape-shaped IBAD base material 7 is wound around the peripheral surface of the intermediate layer 3 so as to circulate while being spaced apart from each other by a plurality of turns. Thus, a plurality of laps (seven laps in the example of FIG. 2) are laid over in a state of being arranged in parallel so that each lap forms a racetrack shape.

  In the traveling system 11 of this example, the IBAD base material 7 delivered from the delivery reel 12 is supplied onto the peripheral surface of the first roll 17 and guided by the first roll 17 and the second roll 18 to each circumference. In FIG. 2, after running a plurality of rounds in a racetrack shape, the take-up reel 13 is wound up. At this time, the compound film (sputtered) of the target material and the reactive gas is applied to the IBAD substrate 7 by the first film forming system 14 and the second film forming system 15 while traveling in a racetrack shape. Film) is formed.

The first film forming system 14 and the second film forming system 15 each form the cap layer 4 on the intermediate layer 3 of the IBAD substrate 7 by using a mixed gas introduced by the gas supply means.
The first film forming system 14 includes an intermediate layer 3 of the IBAD base material 7 that travels along a straight path [forward direction (direction A in FIG. 2)] from the first roll 17 side to the second roll 18 side. A first target (metal target) 14a disposed so as to face the surface; and a first DC power source (not shown) for applying a DC voltage to the first target 14; The membrane system 15 opposes the surface of the intermediate layer 3 of the IBAD base material 7 that travels on a straight path [return direction (B direction in FIG. 2)] from the second roll 18 side to the first roll 17 side. A second target (metal target) 15a arranged in this manner and a second DC power source (not shown) for applying a DC voltage to the second target 15a are provided.
Each of the first target 14 a and the second target 15 a has a rectangular plate shape, and is made of a metal material corresponding to the target metal component of the cap layer 4.

  In each of the film forming systems 14 and 15, when a DC voltage is applied to the first target 14 a and the second target 15 b by each DC power source, and between the first target 14 a and the IBAD substrate 7, and A potential difference is generated between the second target 15a and the IBAD base material 7. As a result, the gas supplied to these spaces is activated (ionization, ionization, excitation, etc.) to generate plasma. Then, carrier gas ions generated in the plasma collide with the targets 14a and 15b, and target materials (sputtered particles) are ejected from the targets 14a and 15b. The sputtered particles sputtered react with the activated reaction gas and deposit on the surface of the IBAD substrate 7 to form a compound film. Here, when the compound film is self-oriented, in the process of depositing on the film formation surface, first, the crystal grains are epitaxially grown with each crystal axis oriented, and then the crystal grains in the lateral direction (plane direction). Grain grows rapidly (overgrowth), and crystal grains become coarse in the in-plane direction and selectively grow. For this reason, the formed sputtered film exhibits a higher in-plane orientation than the crystal structure of the underlying film-forming surface.

  The heater (heating means) 16 is disposed between the first roll 17 and the second roll 18 (inside the traveling system 11), and travels along the forward straight path IBAD base material 7. And the IBAD base material 7 of the return path | route which drive | works the linear path | route of a reverse direction can be directly heated to the target temperature, for example, 500-800 degreeC from those back sides.

Next, the operation of the cap layer forming apparatus will be described.
First, the inside of the vacuum chamber is brought into a predetermined reduced pressure state by the operation of a vacuum pump provided in the exhaust means. Next, a mixed gas of a carrier gas and a reactive gas is supplied into the vacuum chamber using a gas supply means.
Further, the rolls 17 and 18 and the reels 12 and 13 are driven to rotate by the operation of the rotation driving means. As a result, the IBAD base material 7 wound around the delivery reel 12 is sent out on the peripheral surface of the first roll 17. The delivered IBAD base material 7 is wound around a take-up reel 13 after traveling a plurality of rounds of the traveling system 11 in a racetrack shape.

Next, the IBAD base material 7 that travels in the traveling system 11 is heated by the operation of the heater 16.
Here, the heating temperature of the IBAD substrate 7 is preferably 500 to 800 ° C, and more preferably 600 to 700 ° C. By heating the IBAD substrate 7 in this temperature range, the compound film of the target material and the reactive gas can be epitaxially grown on the surface of the intermediate layer 3 at high speed and with high orientation.

  Next, a voltage is applied to the first target 14a and the second target 15b by the first DC power source and the second DC power source. As a result, the gas supplied between the first target 14a and the IBAD substrate 7 and the gas supplied between the second target 15a and the IBAD substrate 7 are activated (ionized), respectively. , Ionization, excitation, etc.) to generate plasma. Then, carrier gas ions generated in the plasma collide with the targets 14a and 15b, and target materials (sputtered particles) are ejected from the targets 14a and 15b. The ejected target material reacts with the activated reaction gas and is deposited on the surface of the intermediate layer 3 of the IBAD substrate 7. Thereby, a compound film (sputtered film) of the target material and the reactive gas can be formed.

Here, in the present embodiment, since the two film forming systems 14 and 15 are provided, the IBAD substrate 7 has two layers of sputtered films on the intermediate layer 3 each time the traveling system 11 travels once. Can be laminated.
Furthermore, the IBAD base material 7 travels the second to seventh laps of the traveling system. The IBAD base material 7 passes through the region facing the first target 14a and the region facing the second target 15a each time it travels around each round, and each time it passes through each region, A compound film (second sputtered film to fourteenth sputtered film) of the substance and the reactive gas is formed. Through the above process, the cap layer 4 is finally formed on the IBAD substrate 7 that has traveled the traveling system 11 as a laminated film of the first sputtered film to the 14th sputtered film.
Then, the IBAD base material 7 on which the cap layer 4 is formed is wound around the take-up reel 13 and collected.
Through the above steps, the oxide superconducting conductor substrate 1 in which the intermediate layer 3 and the cap layer 4 are formed on the metal substrate 2 is obtained.

In the oxide superconducting conductor substrate 1 manufactured as described above, the cap layer 4 has a high in-plane orientation. For this reason, when the oxide superconducting layer 6 is formed on the cap layer 4, the oxide superconducting layer 6 is epitaxially grown so as to match the crystal orientation of the cap layer 4 having a high degree of in-plane orientation. And an oxide superconducting layer 6 having a large critical current density can be obtained.
In the cap layer forming apparatus 10 of this embodiment, since the cap layer 4 is formed on the intermediate layer 3 by the reactive DC sputtering method, the target may be any material that can be sputtered by ion irradiation, and a metal target is used. be able to. Since the metal target is harder to break than the oxide target, it can be easily handled and is less likely to be wasted due to breakage. For this reason, it is advantageous in reducing the manufacturing cost of the base material 1 for oxide superconducting conductors.

Further, the direct current power source used in the reactive DC sputtering method can easily supply a high output (about 2 kW to 16 kW) to the sputtering electrodes (the first target 14a and the second target 15a). Efficiency can be improved easily. For this reason, since this cap layer forming apparatus 10 can obtain a larger film forming rate than the PLD apparatus, the cap layer 4 is formed with a sufficient film thickness while the IBAD base material 7 is traveling at a relatively high speed. can do. As a result, the productivity of the oxide superconducting conductor substrate 1 can be improved.
Further, in the reactive DC sputtering method, since the film formation rate is high in this way, each sputtered film is grown in the plane direction at a high speed in the process in which each sputtered film is self-oriented with respect to the intermediate layer 3. Can be generated. For this reason, it is possible to form the cap layer 4 having a more excellent in-plane orientation.

Furthermore, the cap layer forming apparatus 10 is an apparatus that can be obtained at a lower cost than a laser vapor deposition apparatus because it does not use expensive parts such as a laser oscillator, and the gas used is Ar or oxygen gas, so that the operating cost is high.・ Maintenance costs are low. For this reason, it is advantageous in reducing the manufacturing cost of the base material 1 for oxide superconducting conductors.
Further, the cap layer forming apparatus 10 can be operated for a long time without the problem of gas deterioration unlike the PLD apparatus. For this reason, the cap layer 4 can be continuously formed over a long time, and the cap layer 4 can be easily formed on the long base 2. As a result, the base material 1 for oxide superconducting conductors can be lengthened.

And in the manufacturing method of the oxide superconducting conductor of this invention, the oxide superconductor film | membrane 6 is formed on the cap layer 4 of the base material 1 for oxide superconducting conductors manufactured in this way, and an oxide superconducting conductor is formed. Get 5.
The oxide superconducting layer 6 can be formed by a normal film forming method, but it is preferable to use a PLD method, a CVD method, or the like from the viewpoint of productivity.

Here, in the base material 1 for an oxide superconducting conductor manufactured as described above, the cap layer 4 has a high in-plane orientation degree, so that the crystal orientation of the cap layer 4 having a high in-plane orientation degree is achieved. The oxide superconductor is epitaxially grown so as to match, and the oxide superconductor film 6 having excellent in-plane orientation is formed. As a result, the oxide superconducting conductor 5 having a large critical current density is obtained.
Further, as described above, since the oxide superconducting conductor substrate 1 can be efficiently manufactured at low cost, the oxide superconducting conductor 5 is also constituted by the oxide superconducting conductor substrate 1. The parts can be manufactured efficiently at low cost. As a result, the oxide superconductor 5 can be manufactured with high productivity.
In addition, in the said embodiment, each member which comprises each process of the manufacturing method of the base material 1 for oxide superconducting conductors and the manufacturing method of the oxide superconducting conductor 5, and the formation layer of the cap layer 4 for oxide superconducting conductors is an example. However, it can be appropriately changed without departing from the scope of the present invention.

Specific examples of the present invention will be described below, but the present invention is not limited to these examples.
<Evaluation of Cap Layer Formation Method>
Example 1
First, a Gd ₂ Zr ₂ O ₇ film (GZO intermediate layer) having a thickness of 1 μm was formed on a long tape-shaped Hastelloy metal substrate by the IBAD method. ΔΦ measured by the X-ray diffraction method of this GZO intermediate layer was 15 °.
Next, a CeO ₂ layer (cap layer) having a thickness of 0.2 μm was formed on the GZO intermediate layer using a cap layer forming apparatus shown in FIG. The conditions for forming the CeO ₂ layer are as follows.
Target: cerium metal, number of targets: 1, DC power output: 2 kW, IBAD substrate travel speed: 150 m / h, IBAD substrate temperature: 600 ° C., concentration of oxygen gas contained in mixed gas: 10% . Under the above conditions, a substrate for a superconducting conductor was produced.

(Example 2 to Example 9)
A substrate for a superconducting conductor was produced in the same manner as in Example 1 except that the film formation conditions for the CeO ₂ layer were changed as shown in Table 1.

(Comparative Example 1)
A base material for a superconducting conductor was manufactured in the same manner as in Example 1 except that a CeO ₂ layer having a thickness of 0.5 μm was formed by the PLD method. The conditions for forming the CeO ₂ layer are as follows.
Deposition source: CeO ₂ pellets with a diameter of 3 cm, number of deposition sources: 1, laser: KrF excimer laser, laser output: 0.3 kW, laser density: 3 J / cm ² , laser frequency: 17 Hz, traveling speed of IBAD substrate: 60 m / h, temperature of IBAD substrate: 650 ° C., oxygen gas pressure: about 4 Pa.
(Comparative Example 2)
A substrate for a superconducting conductor was produced in the same manner as in Comparative Example 1 except that the film formation conditions for the CeO ₂ layer were changed as shown in Table 1.

[Evaluation]
About the base material for superconducting conductors manufactured in each Example and each Comparative Example, the thickness of the CeO ₂ layer was measured, and ΔΦ (FWHM: full width at half maximum) was measured by an X-ray diffraction method. Here, ΔΦ serves as an index of the in-plane orientation degree of the sample. The smaller this value, the higher the in-plane orientation degree. The measurement results are shown in Table 1 together with the conditions for forming the CeO ₂ layer.

In Table 1, Examples 2, 5, and 8 having the same cap layer thickness are compared with Comparative Example 1, Examples 3, 6, and 9 are compared with Comparative Example 2, and each is compared to form each example. It can be seen that the cap layer has a higher degree of in-plane orientation than the cap layer formed in each comparative example.
From this, it was found that using a reactive DC sputtering method using a metal target as a method for forming the cap layer, a cap layer having a higher degree of in-plane orientation can be obtained than when the PLD method is used. .

In addition, in the PLD method, a device on the market that has an output of 0.3 kW is the limit at present, and the laser oscillator and the rare gas used for this are expensive, so it is difficult to add a laser light source. For this reason, it is difficult to increase the number of vapor deposition sources.
On the other hand, in the reactive DC sputtering method, the output of the DC power supply and the number of targets can be increased more easily than the above example.
Here, as shown in Table 1, in Examples 4 to 6 in which the number of targets is two, and in Examples 7 to 9 in which the output of the DC power supply is 8 kW, Comparative Example 1 and Comparative Example 2 In addition, the cap layer having the same crystal orientation can be formed with the same film thickness as those of each of the comparative examples while running the IBAD substrate at a high speed.

  That is, when the reactive DC sputtering method is used, the output of the DC power source and the number of targets can be increased, so that the IBAD substrate is driven at a higher speed than when the PLD method is used. The target crystal orientation cap layer can be formed. From this, it was found that the productivity of the base material for a superconducting conductor can be improved by using the reactive DC sputtering method as the cap layer forming method.

<Examination of oxygen concentration in reactive DC sputtering method>
Experimental Example 1 to Experimental Example 9
A superconducting conductor substrate was produced in the same manner as in Example 1 except that when forming the CeO ₂ layer, the oxygen concentration of the mixed gas was changed as shown in Table 2.
[Evaluation]
About the base material for superconducting conductors manufactured in each experimental example, the thickness and in-plane orientation degree (ΔΦ) of the CeO ₂ layer were measured. The results are shown in Table 2 together with the conditions for forming the CeO ₂ layer.

As shown in Table 2, it is assumed that the cap layer formed in Experimental Example 1 in which the oxygen concentration is less than 3% cannot partially form CeO ₂ , and the function as the cap layer cannot be sufficiently obtained. Is done. Further, in Experimental Examples 6 and 7 in which the oxygen concentration was higher than 20%, the formed CeO ₂ layer was thin, and in order to form a cap layer with an appropriate thickness, the traveling speed of the IBAD substrate was further decreased. Must. This is disadvantageous in improving the productivity of the base material for superconducting conductors more than the current level, but an appropriate thickness can be secured up to an oxygen concentration of 50%, and the film thickness is impure at a concentration of 60%. Tended to be minutes. In consideration of the O ₂ concentration, they tend to O ₂ concentration can not be less and CeO ₂ layer itself formed, plane orientation when the O ₂ concentration is too high on the contrary can be estimated to be low.
From these, it was found that the oxygen concentration of the mixed gas is preferably 5 to 50% when the cap layer is formed by the reactive DC sputtering method. Within this range, a range of 10 to 20% seems to be more preferable.

<Examination of substrate temperature when forming cap layer>
Experimental Example 10 to Experimental Example 16
A superconducting conductor substrate was produced in the same manner as in Example 1 except that the temperature of the IBAD substrate was changed as shown in Table 3 when the CeO ₂ layer was formed.
[Evaluation]
About the base material for superconducting conductors manufactured in each experimental example, the thickness and in-plane orientation degree (ΔΦ) of the CeO ₂ layer were measured. The results are shown in Table 3 together with the conditions for forming the CeO ₂ layer.

As shown in Table 3, the cap layers formed in Experimental Examples 10 and 11 in which the temperature of the IBAD substrate was less than 500 ° C. and Experimental Example 16 in which the temperature was higher than 800 ° C. tend to have low in-plane orientation. It is estimated that the function as a cap layer tends to be insufficient. In terms of temperature, it can be estimated that CeO ₂ cannot be formed if it is too low, and that if it is too high, film surface roughness occurs and epitaxial growth cannot be achieved.
From these facts, it was found that the temperature of the IBAD substrate is preferably 500 to 800 ° C. when the cap layer is formed by the reactive DC sputtering method.

It is a schematic longitudinal cross-sectional view which shows the base material for oxide superconductors manufactured by the manufacturing method of this invention, and an oxide superconductor. It is a schematic perspective view which shows the cap layer forming apparatus used with each manufacturing method of the base material for oxide superconductors of this invention, and an oxide superconductor. It is a typical perspective view which shows the general layer structure of an oxide superconductor. It is a schematic diagram which shows the film-forming apparatus which forms an intermediate | middle layer by IBAD method. It is a perspective view which shows the film-forming apparatus which forms a cap layer into a film by PLD method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Base material for oxide superconductor, 2 ... Metal base material, 3 ... Intermediate layer, 4 ... Cap layer, 5 ... Oxide superconductor, 6 ... Oxide superconductor Layer, 7 ... IBAD substrate, 10 ... cap layer forming device (cap layer forming device for oxide superconducting conductor) 11 ... running system, 12 ... feeding reel (substrate feeding means), DESCRIPTION OF SYMBOLS 13 ... Winding reel (base material winding means), 14 ... 1st film-forming system, 14a ... 1st target (metal target), 15 ... 2nd film-forming system, 15a. .. Second target (metal target), 16... Heater (heating means), 17... First roll, 18.

Claims (9)

An oxidation comprising: a base material; an intermediate layer deposited on the base material by an ion beam assist (IBAD) method; and a cap layer formed on the intermediate layer, wherein an oxide superconducting layer is formed on the cap layer When manufacturing base materials for superconducting materials,
A method for producing a base material for an oxide superconducting conductor, wherein the cap layer is formed by a reactive DC sputtering method using a metal target.   The method for producing a base material for an oxide superconducting conductor according to claim 1, wherein the base material is heated to 500 to 800 ° C. when the cap layer is formed.   The gas introduced into the film formation space for forming the cap layer is a mixed gas composed of a carrier gas and an oxygen gas, and the oxygen concentration of the mixed gas is 5 to 50%. The manufacturing method of the base material for oxide superconducting conductors of description. Method of manufacturing an oxide superconducting conductor substrate according to any one of claims 1 to 3, characterized in that the cap layer and CeO _2.   A method for producing an oxide superconducting conductor, comprising forming an oxide superconducting layer on a cap layer obtained by the method according to claim 1. An IBAD substrate having an elongated substrate and an intermediate layer deposited on the substrate by an ion beam assist (IBAD) method; a cap layer formed on the intermediate layer of the IBAD substrate; A device for forming a cap layer for an oxide superconducting conductor that forms the cap layer of an oxide superconducting conductor comprising an oxide superconducting layer formed on a cap layer,
A traveling system in which the IBAD base material travels, a base material feeding means for feeding out the IBAD base material, a base material winding means for winding up the IBAD base material discharged from the traveling system, and a traveling system. A metal target disposed to face the intermediate layer surface of the IBAD substrate;
A power supply for applying a DC voltage to the metal target; and a gas supply means for supplying a carrier gas and a reactive gas between the IBAD substrate and the metal target,
An apparatus for forming a cap layer for an oxide superconducting conductor, wherein the cap layer is formed on the intermediate layer of the IBAD substrate by a reactive DC sputtering method.   The apparatus for forming a cap layer for an oxide superconducting conductor according to claim 6, further comprising a heating means for heating the IBAD base material forming the cap layer to 500 to 800 ° C.   As the traveling system, a traveling system for forming an outward path and a returning path for traveling of the IBAD base material is provided, and at least two of the metal targets are provided, and one of the targets is the intermediate layer of the IBAD base material traveling on the outward path. 8. The apparatus according to claim 6, wherein the other target is disposed opposite to the surface of the intermediate layer of the IBAD base material traveling on the return path. An apparatus for forming a cap layer for an oxide superconducting conductor.   A region in which a plurality of racetrack-shaped traveling paths having a forward path and a return path are provided between the reels as a pair as the traveling system and are arranged side by side apart from each other, and a plurality of the forward paths are arranged side by side A base for traveling in the forward path in a region between the forward path and the return path, and installing a target for the reverse path facing an area where a plurality of the return paths are provided. The apparatus for forming a cap layer for an oxide superconducting conductor according to claim 8, further comprising heating means capable of heating the base material traveling on the return path.

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