JPH09120719A - Oxide type superconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxide type superconductor which is equipped with at least either of the two material traits, i.e., the trait that superconductive layer with no generation of warp in the base member and with a stable superconductivity is formed, and the trait that little strain is generated in the base member and an enhanced critical current density per overall is obtained. SOLUTION: An orientation-controlled multi-crystalline intermediate thin film 22 is formed on the oversurface of a tape-shaped base member 21 of an oxide type superconductor 20, while a multi-crystalline quick formed intermediate thin film 23 is provided on the undersurface of the base member 21, and an oxide type superconductive layer 24 is installed on the intermediate thin film 22. Thereby the resultant oxide superconductor is equipped with at least either of the two material traits, i.e., the trait that a superconductive layer 24 with no generation of warp in the base member 21 due to a compressive force at the time of formation of the intermediate thin film 22 and with a stable superconductivity is formed and the trait that little strain is generated in the base member 21 at the time of evaporative attachment of the layer 24 even in case the base used 21 has a small thickness and an enhanced critical current density per overall is obtained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an oxide superconducting conductor used in a magnet for a superconducting generator, a magnet for a magnetic levitation train, etc., and has a critical current density per overall (total cross-sectional area of oxide superconducting conductor). The present invention relates to an oxide superconducting conductor having at least one of excellent characteristics and a characteristic that an oxide superconducting layer having stable superconducting characteristics in the length direction of a base material is formed.

[0002]

2. Description of the Related Art Oxide superconductors discovered in recent years are excellent superconductors having a critical temperature exceeding the temperature of liquid nitrogen. At present, this type of oxide superconductor is a practical superconductor. There are various problems to be solved in order to use this. One of the problems is that the critical current density of the oxide superconductor is low.

[0003] The problem that the critical current density of the oxide superconductor is low is largely due to the existence of electrical anisotropy in the crystal itself of the oxide superconductor. It is known that electricity easily flows in the a-axis direction and the b-axis direction of the crystal axis, but hardly flows in the c-axis direction. From such a viewpoint, in order to form an oxide superconductor on a base material and use it as a superconductor, an oxide superconductor having a good crystal orientation is formed on the base material, and It is necessary to orient the a-axis or b-axis of the crystal of the oxide superconductor in the direction in which electricity is to flow, and to orient the c-axis of the oxide superconductor in the other direction.

[0004]

By the way, in order to use an oxide superconductor as a conductor, it is necessary to form an oxide superconducting layer having good crystal orientation on a long base material such as a tape. There is. However, if an oxide superconducting layer is formed directly on a base material such as a metal tape, the metal tape itself is polycrystalline and its crystal structure is significantly different from that of the oxide superconductor. Layers cannot be formed at all. In addition, since the heat treatment performed when forming the oxide superconducting layer causes a diffusion reaction between the metal tape and the oxide superconducting layer, there is a problem that the crystal structure of the oxide superconducting layer is destroyed and the superconducting characteristics are deteriorated. .

Therefore, the present inventors formed a polycrystalline intermediate thin film 2 such as yttrium-stabilized zirconia (YSZ) on a substrate 1 made of a metal tape such as Hastelloy tape as shown in FIG. on crystalline intermediate thin 2, the critical temperature of about 90K among the oxide superconductor to form a Y1Ba ₂ Cu ₃ superconducting layer 3 of Ox system with excellent stability can be used in liquid nitrogen (77K) Therefore, various attempts have been made to manufacture the superconducting conductor 10 having excellent superconducting properties. From such attempts, the present inventors have previously proposed, in order to form an intermediate thin film having excellent crystal orientation, or to obtain a superconducting tape having excellent superconducting properties, Japanese Patent Application No. 3-126836. , Japanese Patent Application No. 3-12683
No. 7, Japanese Patent Application No. 3-2055551, Japanese Patent Application No. 4-1344
Patent applications have been filed in Japanese Patent Application No. 3 and Japanese Patent Application No. 4-293464.

According to the techniques described in these patent applications, when a polycrystalline intermediate thin film is formed on one surface of a base material of a metal tape such as Hastelloy tape by a sputtering apparatus, the surface of the base material film is formed simultaneously with sputtering. A polycrystalline intermediate thin film excellent in crystal orientation can be formed by a method of forming a polycrystalline intermediate thin film while irradiating an ion beam from an oblique direction (ion beam assisted sputtering method). According to this method, the grain boundary tilt angle formed by the a-axis or the b-axis of each crystal lattice of a large number of crystal grains forming the polycrystalline intermediate thin film can be made equal to 30 degrees or less, and the crystal orientation is excellent. A polycrystalline intermediate thin film can be formed. Furthermore, if a YBaCuO-based superconducting layer is formed on the intermediate thin film having excellent orientation by a laser deposition method or the like, the crystal orientation of the oxide superconducting layer will also be excellent, whereby the crystal orientation Excellent, 77K
It is possible to form an oxide superconducting layer having a high critical current density of 10 ⁵ A / cm ² or more.

However, in the method according to the above-mentioned patent application, when a polycrystalline intermediate thin film is formed on one surface of the base material by the ion beam assisted sputtering method, distortion occurs due to compressive stress and the base material warps. When depositing an oxide superconducting layer, it is necessary to keep the surface temperature of the base material constant in order to form an oxide superconducting layer with uniform superconducting properties. It is difficult to uniformly heat the surface of the base material, and the temperature distribution on the surface of the base material becomes uneven. As a result, an oxide superconducting layer with unstable superconducting properties in the length direction of the base material is obtained. was there. Furthermore, in the method according to the above-mentioned patent application, since the oxide superconducting layer obtained has a thickness of several μm, it is thinner than the substrate of a metal tape having a thickness of several hundred μm, and the overall (oxidation) There is a problem that the critical current density per unit superconducting conductor) does not increase. Therefore, in order to improve the critical current density per overall, the thickness of the metal tape as the base material is reduced, and a polycrystalline intermediate thin film is formed on one surface of the base material by the ion beam assisted sputtering method. When an oxide superconducting layer is formed on the crystalline intermediate thin film by a laser deposition method or the like, the base material thermally expands due to a high temperature atmosphere at the time of vapor deposition of the oxide superconducting layer, and distortion such as warpage or twist occurs in the base material, The polycrystalline intermediate thin film formed on the material is also distorted. If such a strain is present in the polycrystalline intermediate thin film, the crystal orientation of the oxide superconducting layer formed on the polycrystalline intermediate thin film becomes poor, and the desired superconducting properties cannot be obtained.

The present invention has been made to solve the above-mentioned problems, and the warping of the base material does not occur due to the compressive stress at the time of forming the polycrystalline intermediate thin film, and the superconducting property in the longitudinal direction of the base material is stable. Characteristic that the oxide superconducting layer is formed, even if a thin tape-shaped substrate is used, the substrate is less likely to be strained by the high temperature atmosphere during vapor deposition of the oxide superconducting layer, An object is to provide an oxide superconducting conductor having at least one of the characteristics that the critical current density per overall is improved.

[0009]

In order to solve the above-mentioned problems, a tape-shaped base material and a large number of crystal grains formed on one surface of the base material are combined. Comprising an orientation-controlled polycrystalline intermediate thin film, a polycrystalline intermediate rapid-forming thin film formed on the other surface of the substrate, and an oxide superconducting layer formed on the orientation-controlled polycrystalline intermediate thin film. It is a thing. In order to solve the above-mentioned problems, the invention according to claim 2 is a tape-shaped base material, and an orientation-controlled polycrystalline intermediate thin film formed on both surfaces of the base material and having a large number of crystal grains bonded to each other, An oxide superconducting layer formed on this orientation-controlled polycrystalline intermediate thin film is provided.

In order to solve the above-mentioned problems, a third aspect of the present invention is a polycrystalline rapid-growth intermediate thin film comprising a tape-shaped base material and a large number of crystal grains bonded to both surfaces of the base material. And an orientation-controlled polycrystalline intermediate thin film formed on one of the polycrystalline accelerated intermediate thin films, and an oxide superconducting layer formed on the orientation-controlled polycrystalline intermediate thin film. It will be.

In order to solve the above-mentioned problems, a fourth aspect of the present invention is a polycrystalline quick-deposited intermediate thin film comprising a tape-shaped base material and a large number of crystal grains formed on both surfaces of the base material. And an orientation-controlled polycrystalline intermediate thin film formed on each of these polycrystalline accelerated intermediate thin films, and an oxide superconducting layer formed on each of these orientation-controlled polycrystalline intermediate thin films.

In order to solve the above-mentioned problems, the invention according to claim 5 is characterized in that each of a large number of crystal grains forming the orientation-controlled polycrystalline intermediate thin film of the oxide superconducting conductor according to any one of claims 1 to 4. The grain boundary tilt angle is 30 degrees or less.
In order to solve the above problems, the invention according to claim 6 is such that the intermediate thin film of the oxide superconducting conductor according to any one of claims 1 to 5 is made of yttrium-stabilized zirconia. In order to solve the above-mentioned problems, the invention according to claim 7
The oxide superconducting conductor according to claim 2 or 4, wherein the orientation-controlled polycrystalline intermediate thin film is formed by an ion beam assisted sputtering method.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of the present invention will be described below with reference to the drawings. FIG. 1 shows a first example of an oxide superconducting conductor according to the present invention. In the oxide superconducting conductor 20 of this example, a large number of crystal grains are bonded on the upper surface of a tape-shaped substrate 21. The orientation-controlled polycrystalline intermediate thin film 22 is formed, and the polycrystalline rapid intermediate thin film 2 is formed on the lower surface of the substrate 21.
3 is formed, and the oxide superconducting layer 24 is formed on the orientation controlling polycrystalline intermediate thin film 22.

As a constituent material of the base material 21, a long metal tape appropriately selected from various metal materials such as stainless steel, copper, or alloys such as nickel alloys such as Hastelloy can be used. The thickness of this base material 21 is
0.01-0.5 mm, preferably 0.02-0.15
mm. When the thickness of the base material 21 exceeds 0.5 mm, it is thicker than the thickness of the oxide superconducting layer 24 described later,
The critical current density per overall (total cross-sectional area of oxide superconducting conductor) may decrease. On the other hand, if the thickness of the base material 21 is less than 0.01 mm, the strength of the base material is significantly reduced, and the reinforcing effect of the superconductor may be lost.

The orientation-controlled polycrystalline intermediate thin film 22 is made up of a large number of fine crystal grains, each of which is a collection of crystals having a cubic crystal structure, joined and integrated with each other through grain boundaries. The c-axis of the crystal axis is oriented substantially at right angles to the upper surface (deposition surface) of the base material 21, and the a-axis and the b-axis of the crystal axes of the respective crystal grains are oriented in the same direction with each other. It is oriented. The a-axis (or b) of the crystal of each grain
Axis), the angle they make (grain boundary tilt angle K) is 30
It is preferable that they are joined and integrated within one degree. The thickness of the orientation control polycrystalline intermediate thin film 22 is 0.1 to 1.0.
μm, preferably 0.3 to 0.7 μm. Even if the thickness of the orientation-controlled polycrystalline intermediate thin film 22 is made thicker than 1.0 μm, the effect cannot be expected to increase any more, which is economically disadvantageous. On the other hand, when the thickness of the orientation-controlled polycrystalline intermediate thin film 22 is less than 0.1 μm, the base material 21 cannot be sufficiently supported because it is too thin, and the base material 21 is distorted by a high temperature atmosphere during vapor deposition of the oxide superconducting layer 24 described later. Is likely to occur, and the elements of the oxide superconducting layer 24 may be diffused to the base material 21 side during the heat treatment, and the composition of the oxide superconducting layer 24 may be destroyed.

The polycrystalline quick-deposited intermediate thin film 23 is formed by joining and integrating a large number of fine crystal grains, each of which is a collection of crystals having a cubic crystal structure, through crystal grain boundaries. The thickness of the polycrystalline quick-deposition intermediate thin film 23 is 0.1 to
The thickness is 1.0 μm, preferably 0.3 to 0.7 μm.
Even if the thickness of the polycrystalline rapid-deposited intermediate thin film 23 exceeds 1.0 μm, the effect cannot be expected to increase any more, which is economically disadvantageous. On the other hand, when the thickness of the polycrystalline quick-deposited intermediate thin film 23 is less than 0.1 μm, the base material 21 cannot be sufficiently supported because it is too thin, and the base material 21 is distorted by a high temperature atmosphere during vapor deposition of the oxide superconducting layer 24 described later. This may occur.

The oxide superconducting layer 24 is formed of Y ₁ Ba ₂ Cu ₃
Ox, Y ₂ Ba ₄ Cu ₈ Ox, Y ₃ Ba ₃ Cu ₆ Ox composition,
(Bi, Pb) ₂ Ca ₂ Sr ₂ Cu ₃ Ox, (Bi, Pb) ₂ C
a ₂ Sr ₃ Cu ₄ Ox composition or Tl ₂ Ba ₂ Ca ₂
Cu ₃ Ox, Tl ₁ Ba ₂ Ca ₂ Cu ₃ Ox, Tl ₁ Ba ₂ Ca ₃
It is made of a superconducting material having a high critical temperature represented by a composition such as Cu ₄ Ox. The oxide superconducting layer 24 has a thickness of about 0.5 to 5 μm.

Next, an apparatus and a manufacturing method for manufacturing the orientation-controlled polycrystalline intermediate thin film 22 and the polycrystalline quick-deposited intermediate thin film 23 will be described. FIG. 2 shows an example of an apparatus for producing the polycrystalline quick-deposited intermediate thin film 23, and the apparatus of this example is a high frequency sputtering apparatus. The apparatus of this example is based on the base material 2
1 is mainly composed of a base material holder 31 that holds 1 and a plate-shaped target 32 that is disposed above the base material holder 31 and faces each other at a predetermined interval. Also, reference numeral 3 in the drawing
Reference numeral 3 denotes a target holder that holds a target 32. The target holder 33 is connected to a high frequency power source 34, and the high frequency power source 34 and the base material holder 31 are grounded. In addition, reference numeral 35 in the drawing denotes a tape-shaped substrate 21 feeding device, and 36 denotes a winding device for the substrate 21, and the feeding device 35 continuously feeds the substrate 21 onto the substrate holder 31, Then, the film is continuously wound by the winding device 36 so that continuous film formation can be performed on the base material 21.

The base material holder 31 and the target holder 33 are housed in a vacuum container (not shown) so that the surroundings of the base material holder 31 and the target holder 33 can be kept in a vacuum atmosphere. Further, an atmosphere gas supply source such as a gas cylinder is connected to the vacuum container, and if necessary, the inside of the vacuum container is in a low pressure state such as vacuum, and an argon gas or other inert gas atmosphere or oxygen is supplied. It can be made to contain an inert gas atmosphere. With the above configuration, plasma can be generated in the space above the base material 21 by operating the high frequency power source 34 after depressurizing the inside of the vacuum container, and the particles of the target 32 are sputtered by the action of this plasma. It can be blown toward the base material 21 side.

The base material holder 31 is constructed with a heater inside, and the base material 2 placed on the base material holder 31.
1 can be heated to a desired temperature as needed. The target 32 is for forming the desired polycrystalline rapid-deposited intermediate thin film 23, and has the same or similar composition as the polycrystalline intermediate thin film of the desired composition. Specifically, as the target 32, M
Zirconia stabilized with gO or Y ₂ O ₃ (YS
Z), MgO, SrTiO ₃ or the like can be used, but the present invention is not limited to these, and a target suitable for the polycrystalline rapid intermediate film 23 to be formed may be used as appropriate.

Next, the case of forming the YSZ polycrystalline rapid intermediate thin film 23 on the substrate 21 by using the apparatus having the above-mentioned structure will be described. In order to form the polycrystalline rapid intermediate thin film 23 on the base material 21, a YSZ target is used and the inside of the vacuum container accommodating the base material 21 is evacuated to a reduced pressure atmosphere. Then, the high frequency power supply 34 is operated.
As a result, the constituent particles of the target 32 are sputtered and fly onto the base material 21. If these particles are deposited over the required time, a polycrystalline rapid-deposited intermediate thin film having a desired thickness can be formed on the base material 21. The a-axis, the b-axis, and the c-axis of the crystal axes of a large number of crystal grains forming the polycrystalline rapid-deposited intermediate thin film 23 thus obtained may be oriented in arbitrary directions or have orientation. Anything is fine.

Next, FIG. 3 shows an example of an apparatus for manufacturing the above-mentioned orientation-controlled polycrystalline intermediate thin film 22. In this apparatus, an ion beam sputtering apparatus is provided with an ion gun for ion beam assist. It is composed. The apparatus of this example includes a base material holder 45 that holds the base material 21, a plate-shaped target 46 that is diagonally above and facing the base material holder 45 with a predetermined interval, and a diagonally above the base material holder 45. The main components are an ion gun 47 facing each other at a predetermined interval and spaced apart from the target 46, and a sputter beam irradiation device 48 disposed obliquely below the target 46 toward the lower surface of the target 46. There is. Reference numeral 49 in the figure denotes a target holder that holds the target 46. Further, reference numeral 55 in the drawing denotes a tape-shaped base material 21 feeding device, and 56 denotes a base material 21 winding device. The base material 21 is continuously fed from the feeding device 55 onto the base material holder 45. Subsequently, the film is wound by the winding device 56 so that continuous film formation can be performed on the base material 21.

The apparatus of this example is housed in a vacuum container (not shown) so that the periphery of the base material 21 can be kept in a vacuum atmosphere. Further, an atmosphere gas supply source such as a gas cylinder is connected to the vacuum vessel, and the inside of the vacuum vessel is kept in a low pressure state such as a vacuum, and an inert gas atmosphere containing argon gas or another inert gas atmosphere or oxygen. The atmosphere can be set.

The substrate holder 45 has a heater inside so that the substrate 21 positioned on the substrate holder 45 can be heated to a desired temperature as needed. An angle adjusting mechanism D is attached to the bottom of the base material holder 45. The angle adjusting mechanism D includes an upper support plate 60 joined to the bottom of the base material holder 45 and the upper support plate 60.
A lower support plate 61 pin-connected to the lower support plate 6 and the lower support plate 6
The base 62 which supports 1 is mainly constituted. The upper support plate 60 and the lower support plate 61 are configured to be rotatable with respect to each other via a pin coupling portion, and the base material holder 4
The tilt angle of 5 can be adjusted. Although the apparatus of this example is provided with the angle adjusting mechanism D for adjusting the angle of the base material holder 45, the angle adjusting mechanism D is attached to the supporting portion of the ion gun 47 to adjust the inclination angle of the ion gun 47 to adjust the ion beam. The incident angle may be adjusted. Further, the angle adjusting mechanism is not limited to the structure of this example, and it goes without saying that various structures can be adopted.

The target 46 is for forming a target orientation-controlled polycrystalline intermediate thin film, and has the same composition as or similar composition to the orientation-controlled polycrystalline intermediate thin film having a desired composition. As the target 46, specifically, zirconia (YSZ) stabilized with MgO or Y ₂ O ₃ , MgO, SrTiO ₃ or the like is used, but the target 46 is not limited to this, and is suitable for the orientation control polycrystalline intermediate thin film to be formed. A target may be used as appropriate.

The ion gun 47 is constructed so that an evaporation source is housed inside the container and an extraction electrode is provided near the evaporation source. Then, a part of the atoms or molecules generated from the evaporation source is ionized, and the ionized particles are controlled by an electric field generated by an extraction electrode and irradiated as an ion beam. There are various methods for ionizing particles, such as a DC discharge method, a high-frequency excitation method, a filament method, and a cluster ion beam method. The filament type is a method in which a tungsten filament is energized and heated to generate thermoelectrons, which are collided with evaporated particles in a high vacuum to be ionized. In the cluster ion beam method, clusters of aggregated molecules coming out of vacuum from a nozzle provided at an opening of a crucible containing raw materials are bombarded with thermal electrons to be ionized and emitted. In this example, the ion gun 47 having the internal structure shown in FIG. 4 is used. The ion gun 47 is configured by providing an extraction electrode 66, a filament 67, and an introduction tube 68 for Ar gas or the like inside a cylindrical container 65, and is capable of irradiating ions from the tip of the container 65 in a beam shape in parallel. Is.

As shown in FIG. 3, the ion gun 47 has its central axis S with respect to the upper surface (deposition surface) of the base material 21 at an incident angle θ (perpendicular line (normal line) of the base material 21 and center line S). The angle is made by the angle) and the two are opposed to each other. The incident angle θ is preferably in the range of 50 to 60 degrees, but most preferably in the range of 55 to 60 degrees. Therefore, the ion gun 47 is the base material 2
The upper surface of No. 1 is arranged so that the ion beam can be irradiated at an incident angle θ. The ion beam applied to the base material 21 by the ion gun 47 is He.
An ion beam of a rare gas such as ⁺ , Ne ⁺ , Ar ⁺ , Xe ⁺ , and Kr ⁺ , or a mixed ion beam of those and oxygen ions may be used. However, in order to arrange the crystal structure of the orientation-controlled polycrystalline intermediate thin film to be formed, a certain amount of atomic weight is required, and considering that the effect becomes too thin with an ion that is too light, Ar ⁺ , Kr ^+, etc. It is preferable to use the above ions. The sputter beam irradiation device 48 has the same configuration as the ion gun 47, and irradiates the target 46 with an ion beam so as to irradiate the target 46.
It is possible to knock out the constituent particles of (1) toward the base material 21.

Next, by using the apparatus having the above-mentioned structure, a YSZ orientation control polycrystalline intermediate thin film 22 is formed on the other surface (the surface on which the polycrystalline rapid intermediate thin film 23 is not formed) of the tape-shaped substrate 21. A case of forming by the ion beam assisted sputtering method will be described. In order to form the orientation-controlled polycrystalline intermediate thin film 22 on the surface of the base material 21 on which the polycrystalline rapid intermediate thin film 23 is not formed, a YSZ target is used and the angle adjusting mechanism D is adjusted to adjust the ion gun 47. The ion beam emitted from the
Irradiation is possible at an angle in the range of 0 to 60 degrees. Next, the inside of the container accommodating the base material 21 is evacuated to create a reduced pressure atmosphere. At this time, the pressure inside the vacuum container is lower than the pressure inside the vacuum container of the high frequency sputtering apparatus shown in FIG. 2 because of the use of the ion beam. Then, the ion gun 47 and the sputter beam irradiation device 48 are operated.

When the target 46 is irradiated with the ion beam from the sputter beam irradiation device 48, the constituent particles of the target 46 are knocked out and fly onto the substrate 21. Then, the constituent particles knocked out from the target 46 are deposited on the base material 21, and at the same time, the mixed ion beam of Ar ions and oxygen ions is irradiated from the ion gun 47 to form the orientation control polycrystalline intermediate thin film 22 having a desired thickness. To do. The incident angle θ at the time of ion irradiation is preferably in the range of 50 to 60 degrees, and most preferably in the range of 55 to 60 degrees. Where θ
Is 90 degrees, the c-axis of the polycrystalline intermediate thin film 22 is the base material 2
Although it is oriented at right angles to the film-forming surface on 1, the substrate 21
Since the (111) plane stands on the film formation surface of, it is not preferable. When θ is 30 degrees, the polycrystalline intermediate thin film 22 does not even have c-axis orientation. If the ion beam irradiation is carried out at an angle within the above-mentioned preferable range, the (100) plane of the crystal of the polycrystalline intermediate thin film 22 will stand.

By performing sputtering while irradiating the ion beam at such an incident angle, the substrate 21
Although the a-axis and the b-axis of the crystal axes of the YSZ orientation control polycrystalline intermediate thin film 22 formed above can be oriented, this is at an appropriate angle with respect to the sputtered particles being deposited. Probably because it was irradiated with an ion beam.

The inventors of the present invention assume the following as a factor for adjusting the crystal orientation of the orientation-controlled polycrystalline intermediate thin film 22. The unit cell of the crystal of the orientation control polycrystalline intermediate thin film 22 of YSZ is a cubic system as shown in FIG.
In this crystal lattice, the substrate normal direction is the <100> axis, and the other <010> axes and the <001> axes are the directions shown in FIG. Considering an ion beam that is incident on these directions obliquely with respect to the substrate normal, in the case where the ion beam is incident on the origin O of FIG. 5 along the diagonal direction of the unit lattice, that is, along the <111> axis, The incident angle is 54.7 degrees.

Here, the incident angle is 50 to 60 as described above.
The best crystal orientation when irradiating with an ion beam within a range of degrees means that when the incident angle of the ion beam coincides with or is around 54.7 degrees,
Ion channeling occurs most effectively and the substrate 21
In the crystal that is being deposited on top, only the atoms that have a positional relationship that matches the angle on the upper surface of the base material 21 tend to remain selectively, and other disordered atomic arrangements cause an ion beam from an oblique direction. It is presumed that, as a result of being sputtered and removed by the sputtering effect of No. 3, only the crystals in which the atoms with good orientation are gathered selectively remain and are deposited. However, among the crystals thus deposited, the ones with disordered atomic arrangement are removed while being deposited by the ion beam, so the deposition rate becomes worse and the deposition rate is slower than that of ordinary sputtering. Become slow.

In FIG. 6, the YSZ orientation control polycrystalline intermediate thin film 22 is formed on one surface of the substrate 21 by the method described above.
The thin film laminated body 25 in which the polycrystalline rapid-transition intermediate | middle thin film 23 was formed on the other surface of the base material 21 is shown. In addition, in FIG.
7 shows a state in which only one layer is formed, but crystal grains 2
It goes without saying that 7 may have a multilayer structure.

The thin film laminate 25 having the above structure is put into practical use by further forming an oxide superconducting layer thereon. Since the orientation control polycrystalline intermediate thin film 22 is formed on the uppermost part of the thin film stack 25,
The oxide superconducting layer formed thereon has excellent crystal orientation, which improves superconducting properties.

Next, an apparatus for producing an oxide superconducting conductor by forming an oxide superconducting layer on the thin film laminate 25 and a method for producing the same will be described. FIG. 7 shows an example of an apparatus for forming an oxide superconducting layer by a film forming method, and FIG. 7 shows a laser vapor deposition apparatus. The laser vapor deposition apparatus 70 of this example has a processing container 71, and the thin film laminate 25 and the target 73 can be installed in a vapor deposition processing chamber 72 inside the processing container 71. That is, the base 74 is provided at the bottom of the vapor deposition processing chamber 72, and the thin film stack 25 can be installed on the upper surface of the base 74.
A target 73 supported by a support holder 73a is provided obliquely above the base 74 in an inclined state. Further, in the figure, reference numeral 75 is a delivery device for the thin film laminate 25, and 76 is a winding device for the thin film laminate 25. The delivery device 75 continuously delivers the thin film laminate 25 onto the base 74, and By winding with the winding device 76, it is possible to continuously form a film on the thin film laminate 25. Further, the processing container 71 has a vacuum exhaust device 77 through the exhaust hole 77a.
It is possible to reduce the pressure of the vapor deposition processing chamber 72 to a predetermined pressure.

The target 73 has the same or similar composition as the oxide superconducting layer to be formed, or
It is composed of a sintered body of a complex oxide or a plate body such as an oxide superconductor containing a large amount of components that easily escape during film formation. Therefore, the target 73 is Y ₁ Ba ₂ Cu ₃ Ox, Y ₂
Ba ₄ Cu ₈ Ox, Y ₃ Ba ₃ Cu ₆ Ox, (Bi, P
b) ₂ Ca ₂ Sr ₂ Cu ₃ Ox, (Bi, Pb) ₂ Ca ₂ Sr ₃
Cu ₄ Ox composition or Tl ₂ Ba ₂ Ca ₂ Cu ₃ O
x, Tl ₁ Ba ₂ Ca ₂ Cu ₃ Ox, Tl ₁ Ba ₂ Ca ₃ Cu ₄ O
Since it is used for forming an oxide superconducting layer having a high critical temperature represented by the composition x, etc., it is preferable to use the same composition or a similar composition. The base 74 has a built-in heater, and is a thin film stack 25.
Can be heated to a desired temperature as needed.

On the other hand, a laser emitting device 78, a first reflecting mirror 79, a condenser lens 80, and a second reflecting mirror 81 are provided on the side of the processing container 71, and a laser beam generated by the laser emitting device 78 is provided. The target 73 can be focused and irradiated through the transparent window 82 attached to the side wall of the processing container 71. The laser emitting device 78 is the target 73.
If it is possible to knock out the constituent particles from
Any of AG laser, CO ₂ laser, excimer laser, etc. may be used.

Next, a method of forming the oxide superconducting layer 24 on the YSZ orientation control polycrystalline intermediate thin film 22 will be described. First, the thin film layered product 25 is placed on the base 74 of the laser deposition device 70 shown in FIG. 7 with the orientation control polycrystalline intermediate thin film 22 side facing up, and the deposition processing chamber 72 is decompressed by the vacuum exhaust device 77. . Here, if necessary, an oxygen gas may be introduced into the vapor deposition processing chamber 72 to create an oxygen atmosphere in the vapor deposition processing chamber 72. Further, the heater of the base 74 may be operated to heat the thin film laminate 25 to a desired temperature.

Next, the laser beam emitted from the laser emitting device 78 is focused and irradiated onto the target 73 in the vapor deposition processing chamber 72. As a result, the constituent particles of the target 73 are scooped out or evaporated and the particles are deposited on the orientation-controlled polycrystalline intermediate thin film 22. Here, during the deposition of the constituent particles, the orientation control polycrystalline intermediate thin film 22 is preliminarily c-axis oriented, and the a-axis and b
Since it is also oriented in the axis, the orientation-controlled polycrystalline intermediate thin film 22
Crystals of the oxide superconducting layer 24 formed above are epitaxially grown and crystallized so that the c-axis, a-axis, and b-axis also match the orientation-controlled polycrystalline intermediate thin film 22. Thereby, the oxide superconducting layer 24 having good crystal orientation is obtained. After the film formation, a heat treatment for adjusting the crystal structure of the oxide superconducting layer 24 may be performed if necessary. When the oxide superconducting layer 24 is formed on the thin film laminate 25 by the method described above,
The oxide superconducting conductor 20 of the first example as shown in FIG. 1 is obtained. The oxide superconducting layer 24 formed on the orientation-controlled polycrystalline intermediate thin film 22 is in a polycrystalline state, and in each of the crystal grains of the oxide superconducting layer 24, the thickness of the base material 21 is different. In this direction, the c-axis, in which electricity is difficult to flow, is oriented, and the a-axis or the b-axis is oriented in the plane direction of the base material 21 to provide good crystal orientation. Therefore, the obtained oxide superconducting layer 24 is excellent in the quantum coupling property at the crystal grain boundaries and the deterioration of the superconducting properties at the crystal grain boundaries is small.
It is easy to pass electricity in the surface direction of the base material 21, and a material having an excellent critical current density can be obtained.

In the oxide superconducting conductor 20 of the first example, the tape-shaped base material 21 is obtained by adopting the above-mentioned constitution.
Even if the thickness of the base material 21 is thin, the base material 21 is supported by the orientation-controlled polycrystalline intermediate thin film 22 and the polycrystalline rapid-growth intermediate thin film 23 on both sides, so that the base material 21 may be supported by the high temperature atmosphere during the deposition of the oxide superconducting layer 24. Distortion is suppressed. This reduces distortion in the orientation control polycrystalline intermediate thin film 22 on the base material 21 and improves the flatness of the surface of the orientation control polycrystalline intermediate thin film 22. The crystal orientation of the oxide superconducting layer 24 is improved, and the critical current density is excellent. Therefore, in the oxide superconducting conductor 20 of the first example,
Since the tape-shaped base material 21 having a small thickness is used, the thickness of the oxide superconducting conductor is reduced, and the critical current density per overall (total cross-sectional area of the oxide superconducting conductor) can be improved, and the current capacity can be improved. It is possible to easily provide a long oxide superconducting conductor having a large size.

Also, the oxide superconducting conductor 2 of the first example
The oxide superconducting layer 24 is 0 because the polycrystalline rapid-growth intermediate thin film 23 formed on the lower surface of the base material 21 functions as an insulating layer.
It suffices to further form an insulating layer only on the side, and when it is used as a magnet or the like, it can be wound as it is without forming an insulating layer. Further, in the case where the grain boundary tilt angle of each of a large number of crystal grains forming the orientation-controlled polycrystalline intermediate thin film 22 is 30 degrees or less, the oxide superconductivity formed on the orientation-controlled polycrystalline intermediate thin film 22. Since the crystal orientation of the layer 24 becomes better, it exhibits more excellent superconducting properties. In the oxide superconducting conductor 20 of the first example described above, the case where the polycrystalline quick-deposited intermediate thin film 23 is formed by high frequency sputtering has been described.
Method, vacuum vapor deposition method, electron beam vapor deposition method, laser vapor deposition method, etc., it is necessary to form a polycrystalline rapid-deposited intermediate thin film by a process in which a compressive stress is applied, and high energy plasma is required to assist, and usually Ar The PVD method is preferable because it is necessary to trap a rare gas such as the above in the film.

Further, the oxide superconducting conductor 2 of the first example described above.
In 0, the case where the intermediate thin film formed on the lower surface of the base material 21 is the polycrystalline accelerated intermediate thin film 23 has been described. However, in place of the polycrystalline accelerated intermediate thin film 23, the orientation control polycrystalline intermediate thin film 22 is used. It may be formed, that is, the orientation controlling polycrystalline intermediate thin films 22, 22 in which a large number of crystal grains are bonded to each other may be formed on both surfaces of the base material 21 as shown in FIG. When the orientation-controlled polycrystalline intermediate thin films 22 and 22 are formed on both surfaces of the base material 21, each orientation-controlled polycrystalline intermediate thin film 22 is preferably formed by an ion beam assisted sputtering method. In the thin film stack 25 in which the orientation control polycrystalline intermediate thin films 22 and 22 are formed on both surfaces of the base material 21 by the ion beam assisted sputtering method as shown in FIG. Since the control polycrystalline intermediate thin films 22 and 22 cancel the compressive stress, it is possible to prevent the base material 21 from warping, and further, the orientation control polycrystalline intermediate thin film 22 is formed on the lower surface (heated surface) of the base material 21. Since it is formed, the base material 31 is prevented from being oxidized. Accordingly, when the oxide superconducting layer 24 is vapor-deposited on the orientation-controlled polycrystalline intermediate thin film 22, the surface of the thin film laminate 25 is easily heated uniformly, and the temperature distribution on the surface of the thin film laminate 25 is hardly uneven. Since the temperature of the thin film stack 25 is stable, the oxide superconducting layer 24 having stable superconducting properties in the longitudinal direction of the base material 21 can be formed. Therefore, the oxide superconducting conductor 20 shown in FIG.
In that case, the warp does not occur in the base material due to the compressive stress during the formation of the orientation-controlled polycrystalline intermediate thin film, and the oxide superconducting layer having stable superconducting characteristics in the length direction of the base material is formed. Even if a thin tape-shaped substrate is used, the substrate is less likely to be distorted by the high temperature atmosphere during vapor deposition of the oxide superconducting layer, and the critical current density per overall is improved. It has the advantage of having both.

FIG. 8 shows a second example of the oxide superconducting conductor according to the present invention. In the oxide superconducting conductor 90 of the second example, polycrystalline quick-acting intermediate thin films 23a and 23b are formed on both surfaces of a tape-shaped substrate 21, and one of these polycrystalline quick-acting intermediate thin films 23a and 23b is formed. An orientation-controlled polycrystalline intermediate thin film 22b is formed on the crystallized rapid intermediate thin film 23b.
And an oxide superconducting layer 24 is formed on the orientation-controlled polycrystalline intermediate thin film 22b.

The polycrystalline rapid-growth intermediate thin films 23a, 23 of this example
b is the polycrystalline intermediate-rate thin film 23 of the first example described above.
A large number of crystal grains are bonded to each other in the same manner as described above, and can be formed by using the high frequency sputtering apparatus of FIG. 2 in substantially the same manner as described above.
Although the a-axis and the b-axis are not particularly oriented in the crystal axis of each crystal grain of b, it is preferable that the c-axis be oriented substantially at right angles to the upper surface (film-forming surface) of the base material 21. . This orientation-controlled polycrystalline intermediate thin film 22b can be formed by using an apparatus equipped with an ion beam assisting ion gun in the ion beam sputtering apparatus of FIG. 3 in a manner similar to the method described above. The difference from that is that it is formed on the polycrystalline rapid-growth intermediate thin film 23b.

The total thickness of the intermediate thin film on the upper side of the base material 21, that is, the total thickness of the orientation-controlled polycrystalline intermediate thin film 22b and the polycrystalline accelerated intermediate thin film 23b is 0.1 to 1.0.
μm. The total thickness of the upper intermediate thin film is 1.0μ
Even if the thickness exceeds m, the effect cannot be expected to increase any more, which is economically disadvantageous. On the other hand, if the total thickness of the upper intermediate thin film is less than 0.1 μm, it is too thin and the base material 21
May not be sufficiently supported, and the substrate 21 may be distorted due to a high temperature atmosphere during the vapor deposition of the oxide superconducting layer 24, which will be described later, and the elements of the oxide superconducting layer 24 may be diffused to the substrate 21 side during the heat treatment. This is because the composition of the oxide superconducting layer 24 may be destroyed. In addition, the thickness of the intermediate thin film on the lower side of the base material 21, that is, the thickness of the polycrystalline rapid accelerating intermediate thin film 23b is 0.1 to 1 for the same reason as the polycrystalline rapid accelerating intermediate thin film 23 of the first example. ．
0 μm.

If the intermediate thin film on the upper side of the base material 21 is composed of two layers of the polycrystalline rapid-deposited thin film 23b and the orientation control polycrystalline thin film 22b as in the second example, the polycrystalline rapid-deposited intermediate thin film 23b is formed. It becomes possible to perform the film forming process in a shorter time than the case where the entire film thickness of the orientation control polycrystalline intermediate thin film 22b and the orientation control polycrystalline intermediate thin film 22b is formed. The reason is the first
When the orientation-controlled polycrystalline intermediate thin film 22 which is the upper intermediate thin film with respect to the base material 21 is formed by sputtering while irradiating the ion beam from an oblique direction as in the example of FIG. This is lower than in the case of forming a polycrystalline rapid-deposited intermediate thin film by beam sputtering or high frequency sputtering. For example, high-frequency sputtering can usually form a film at a rate of about 0.5 μm / hour, but sputtering by irradiating an ion beam from an oblique direction can produce a film thickness of 0.1 μm.
The film forming process is performed at a speed of about m / hour.

Therefore, the oxide superconducting conductor 90 of the second example.
In this case, in particular, since the intermediate thin film is composed of two layers of the polycrystalline quick-deposited thin film and the orientation control polycrystalline thin film, the total thickness of the polycrystalline fast-deposited intermediate thin film 23b and the orientation control polycrystalline intermediate thin film 22b is reduced. Compared with the case where all the orientation-controlled polycrystalline intermediate thin films are used, it takes less time to form the orientation-controlled polycrystalline intermediate thin film, and the polycrystalline rapid-deposited intermediate thin-film portion has a faster film forming speed. Shortened. Further, when the polycrystalline rapid-deposited intermediate thin film 23b and the orientation-controlled polycrystalline intermediate thin film 22b are made of the same material, the bondability between the two thin films 23b and 22b becomes good, and the bonding strength between them becomes sufficiently high.

FIG. 9 shows a third example of the oxide superconducting conductor according to the present invention. The oxide superconducting conductor 100 of the third example is a polycrystalline rapid intermediate thin film 2 in which a large number of crystal grains are bonded on both surfaces of a tape-shaped substrate 21.
3a, 23b are formed, and these polycrystalline rapid intermediate thin films 2 are formed.
Alignment control polycrystalline intermediate thin film 22 on 3a and 23b, respectively.
a and 22b are formed, and oxide superconducting layers 24a and 2b are formed on the orientation control polycrystalline intermediate thin films 22a and 22b, respectively.
4b is formed.

The oxide superconducting conductor 100 of the third example
However, the point different from the oxide superconducting conductor 90 of the second example described above is that the polycrystalline rapid-deposited intermediate thin film 2 on the lower side with respect to the base material.
An orientation control polycrystalline intermediate thin film 22a is also formed on 3a,
Furthermore, the oxide superconducting layer 24a is formed on the orientation control polycrystalline intermediate thin film 22a. The polycrystalline rapid-growth intermediate thin film 23a of this example has a large number of crystal grains bonded in the same manner as the polycrystalline intermediate-speed thin film 23 of the first example described above, and is similar to the method described above. And then Figure 2
Can be formed by using the high-frequency sputtering apparatus, and the a-axis and the b-axis are not specially oriented in the crystal axes of the crystal grains of the polycrystalline rapid-deposited intermediate thin film 23a, but the c-axis is the upper surface of the substrate 21 ( It is preferable that the film is oriented substantially at right angles to the film forming surface). Further, this orientation control polycrystalline intermediate thin film 22a
Can be formed by using an apparatus provided with an ion beam assisting ion gun in the ion beam sputtering apparatus of FIG. 3 in substantially the same manner as described above. The orientation-controlled polycrystalline intermediate thin films 22a and 22b formed on both surfaces of the base material 21 via the polycrystalline accelerated intermediate thin films 23a and 23b are preferably formed by ion beam assisted sputtering. In the thin film stack 25 in which the orientation-controlled polycrystalline intermediate thin films 22a and 22b are formed by the ion beam assisted sputtering method as described above, the orientation-controlled polycrystalline intermediate thin films 22a and 22b on both sides have a compressive stress. Since the compressive stress is canceled out, it is possible to prevent the base material 21 from being warped, and further, the polycrystalline quick-deposited intermediate thin film 23a and the orientation control polycrystalline intermediate thin film 22a are formed on the lower surface (heated surface) of the base material 21. Therefore, the base material 31 is prevented from being oxidized. Accordingly, when the oxide superconducting layers 24a and 24b are vapor-deposited on the orientation control polycrystalline intermediate thin films 22a and 22b, the thin film stack 2 is formed.
5 It becomes easier to heat the surface uniformly, and the temperature distribution on the surface of the thin film laminate 25 is hardly uneven.
Since the temperature of 5 is stable, it is possible to form the oxide superconducting layers 24a and 24b having stable superconducting properties in the longitudinal direction of the base material 21.

The total thickness of the intermediate thin films on the lower side of the base material 21, that is, the total thickness of the orientation-controlled polycrystalline intermediate thin film 22a and the polycrystalline rapid-growth intermediate thin film 23a is the orientation-controlled polycrystalline thin film of the second example. Crystal intermediate thin film 22b and polycrystalline rapid intermediate thin film 2
For the same reason as 3b, the thickness is 0.1 to 1.0 μm. The oxide superconducting layer 24a can be formed by using the laser vapor deposition apparatus shown in FIG. 7 in a manner substantially similar to the method described above, and the thickness thereof is 0.5 as in the oxide superconducting layer 24 of the first example.
Approximately 5 μm.

In the oxide superconducting conductor 100 of the third example, since the oxide superconducting layer is formed on both surfaces of the base material 21 through the intermediate thin film, the overall (oxide superconducting conductor is completely cut off). The critical current density per area is about twice as large as that of the oxide superconducting conductor 20 of the first example and the oxide superconducting conductor 90 of the second example, and the critical current density per overall is large, resulting in a larger current capacity. There is an advantage that a large and long oxide superconducting conductor can be easily provided. Furthermore, the oxide superconducting conductor 10 of the third example
0, in which the orientation control polycrystalline intermediate thin films 22a and 22b are respectively formed by the ion beam assisted sputtering method, the base material 21 does not warp due to the compressive stress during the formation of the orientation controlling polycrystalline intermediate thin films. There is also an advantage in that the oxide superconducting layer having stable superconducting properties in the length direction of the base material 21 is formed.

(Operation of the present invention) In the present invention, the intermediate thin films are formed on both surfaces of the tape-shaped substrate, and the oxide superconducting layer is formed on the orientation-controlled polycrystalline intermediate thin film among these intermediate thin films. As a result, even if the thickness of the tape-shaped base material is thin, the base material is supported by the intermediate thin films on both sides, so that the base material is prevented from being distorted by the high temperature atmosphere during the vapor deposition of the oxide superconducting layer. To be done. This reduces distortion in the intermediate thin film on the substrate and improves the flatness of the surface of the intermediate thin film, so that the crystal orientation of the oxide superconducting layer formed on the orientation-controlled polycrystalline intermediate thin film is good. Becomes

Further, since the intermediate thin film is composed of two layers of the polycrystalline rapid-deposited thin film and the orientation control polycrystalline thin film, the total thickness of the polycrystalline fast-deposited intermediate thin film and the orientation-controlled polycrystalline intermediate thin film is all oriented. Compared with the control polycrystalline intermediate thin film, it takes less time to form the orientation-controlled polycrystalline intermediate thin film, and the polycrystalline rapid-growth intermediate thin film portion has a higher film forming speed, so the film forming time is shortened. . Further, since the oxide superconducting layer formed on the orientation-controlled polycrystalline thin film having the grain boundary tilt angle of 30 degrees or less has a better crystal orientation, it exhibits more excellent superconducting properties. Furthermore, by forming the orientation-controlled polycrystalline intermediate thin films on both sides of the substrate by the ion beam assisted sputtering method, the orientation-controlled polycrystalline intermediate thin films on both sides cancel the compressive stress, but the substrate Can be prevented from warping, and further, since the polycrystalline rapid-deposited intermediate thin film and the orientation control polycrystalline intermediate thin film are formed on the lower surface (heated surface) of the base material, the base material is prevented from being oxidized. . This facilitates uniform heating of the surface of the thin film stack when depositing the oxide superconducting layer on the orientation-controlled polycrystalline intermediate thin film, and there is almost no unevenness in the temperature distribution on the surface of the thin film stack. Temperature stabilizes.

[0054]

【Example】

(Example 1) The high frequency sputtering apparatus having the structure shown in FIG. 2 was used, and the inside of the vacuum container of this apparatus was evacuated by a vacuum pump to reduce the pressure to 1 × 10 ⁻³ Torr. As a base material, width 1
Hastelloy C 0 mm thick, 0.1 mm thick and 10 cm long
276 tape was used. A target made of YSZ (stabilized zirconia) is used, and the sputtering voltage is 300V,
Sputtering current is set to 100 mA and sputtering is set to 1
0.5μ thickness on one surface (lower surface) of substrate
m film-like YSZ polycrystalline rapid intermediate thin film was formed.

Next, using the ion beam sputtering apparatus having the structure shown in FIG. 3, the inside of the vacuum container accommodating this apparatus was evacuated by a vacuum pump to reduce the pressure to 3.0 × 10 ⁻⁴ Torr. A target made of YSZ (stabilized zirconia) was used, and the sputtering voltage was 1000 V and the sputtering current was 10
The other side of the substrate (upper surface) was set to 0 mA, the incident angle of the beam of the ion source was set to 55 degrees, the assist voltage of the ion source was set to 300 V, and the current density of the ion beam was set to ²⁰ μA / cm ^2. Ion irradiation is performed at the same time as sputtering, and a film is formed for 5 hours to obtain a thickness of 0.
A YSZ orientation control polycrystalline intermediate thin film of 5 μm was formed, and FIG.
A thin film laminate similar to the above was obtained. The current density of the ion beam is measured by a current density measuring device grounded near the sample.

Then, a thickness of 1.0 μm was formed on the orientation-controlled polycrystalline intermediate thin film by using a laser vapor deposition apparatus having the structure shown in FIG.
The oxide superconducting layer of 1 was formed, and an oxide superconducting conductor similar to that shown in FIG. 1 was produced. As a target, Y _0.7 Ba _1.7 Cu
_A target made of an oxide superconductor having a composition of _3.0 O _7-x was used. After depressurizing the inside of the vapor deposition processing chamber to 1 × 10 ⁻⁶ Torr, oxygen was introduced into the interior to 2 × 10 ⁻³ Torr, and then laser vapor deposition was performed. An ArF laser with a wavelength of 193 nm was used as a laser for target evaporation. After this film formation, the thin film was heat-treated in an oxygen atmosphere at 400 ° C. for 60 minutes. During the vapor deposition and heat treatment here, no strain was generated in the substrate. The oxide superconducting conductor obtained by the above treatment has a thickness of 102.0 μm and a width of 10 m.
m, 10 cm in length.

The oxide superconducting conductor was cooled, and the critical current density was measured. As a result, the critical current density = 5.1 × 1
0 ⁵ A / cm ² (77 K, 0 T), and critical current density per overall = 5,000 A / cm ² (77
K, 0T) was exhibited, and it was confirmed that extremely excellent superconducting properties were exhibited. Thus, the obtained oxide superconducting conductor does not cause distortion in the above-mentioned base material due to a high temperature atmosphere at the time of vapor deposition of the oxide superconducting layer even if a base material having a thin thickness of 0.1 mm is used, and the criticality per overall It was revealed that the current density was improved.

Example 2 An oxide superconducting conductor was produced in the same manner as in Example 1 except that a Hastelloy tape having a width of 10 mm, a thickness of 0.05 mm and a length of 10 cm was used as the base material. The oxide superconducting conductor here has a thickness of 5
It has a width of 2.0 μm, a width of 10 mm, and a length of 10 cm.
The oxide superconducting conductor was cooled and the critical current density was measured. As a result, the critical current density = 4.8 × 10 ⁵ A / cm ²
(77K, 0T), the critical current density per overall was 9.2 × 10 ³ A / cm ^2, and it was confirmed that extremely excellent superconducting properties were exhibited. Thus, the obtained oxide superconducting conductor does not have distortion in the above-mentioned base material due to a high temperature atmosphere at the time of vapor deposition of the oxide superconducting layer even if a base material having a thin thickness of 0.05 mm is used, and the criticality per overall It was revealed that the current density was improved.

(Comparative Example 1) The same procedure as described above was carried out except that a Hastelloy tape having a width of 10 mm, a thickness of 0.5 mm and a length of 10 cm was used as a base material and no polycrystalline rapid intermediate thin film was formed on the lower surface of the base material. An oxide superconducting conductor was produced in the same manner as in Example 1. The oxide superconducting conductor here has a thickness of 50.
It had a thickness of 1.5 μm, a width of 0.5 mm and a length of 10 cm. The oxide superconducting conductor was cooled, and the critical current density was measured. As a result, the critical current density = 5.2 × 10 ⁵ A /
Although cm ² (77 K, 0 T) was shown, the critical current density per overall was as low as 1.0 × 10 ³ A / cm ² .

(Comparative Example 2) An oxide superconducting conductor was produced in the same manner as in Example 1 except that the polycrystalline quick-deposited intermediate thin film was not formed on the lower surface of the substrate. The oxide superconducting conductor here had a thickness of 101.5 μm, a width of 10 mm, and a length of 10 cm. The oxide superconducting conductor was cooled and the critical current density was measured. As a result, the critical current density = 1.1 ×
It showed 10 ⁴ A / cm ² (77 K, 0 T), which was a low critical current density per overall = 1 × 10 ² A / cm ² . Further, in the oxide superconducting conductor, the base material was distorted by the high temperature atmosphere during the vapor deposition of the oxide superconducting layer.

(Embodiment 3) Using a laser vapor deposition apparatus having the structure shown in FIG. 7, a width of 10 mm, a thickness of 0.2 mm and a length of 10
A 0.5 μm thick film-form YSZ polycrystalline rapid intermediate film was formed on both surfaces of a substrate made of a cm Hastelloy C276 tape. As a target, YSZ (stabilized zirconia) was laser-deposited at room temperature. An ArF laser with a wavelength of 193 nm was used as a laser for target evaporation. Here, it took 10 minutes to form a 0.5 μm-thick polycrystalline rapid intermediate thin film on one side of the substrate, and therefore, time required to form a polycrystalline rapid intermediate thin film on both sides. Was 20 minutes. Next, an ion beam sputtering apparatus having the structure shown in FIG. 3 is used, and this apparatus is housed using a target made of YSZ (stabilized zirconia).
The sputter voltage is set to 1000 V, the sputter current is set to 100 mA, the beam angle of the ion source is set to 55 degrees, the assist voltage of the ion source is set to 300 V, and the current density of the ion beam is set to ²⁰ μA / cm ² , respectively. Of one of the polycrystalline rapid-deposited intermediate thin films formed on both surfaces of the film, a film having a thickness of 0.1 μm was formed by performing an ion beam assisted sputtering method in which ion irradiation is performed simultaneously with sputtering on one of the polycrystalline rapid-deposited intermediate thin films. A YSZ orientation controlled polycrystalline intermediate thin film was formed.

Here, the above-mentioned polycrystalline rapid-deposited intermediate thin film having a thickness of 0.5 μm was deposited in 10 minutes, but the orientation-controlled polycrystalline intermediate thin film was deposited at a thickness of 0.1 μm for 1 hour. Since it was possible, it was revealed that forming a polycrystalline rapid-deposited intermediate thin film by laser vapor deposition can be performed at a speed about 5 times faster than producing an orientation-controlled polycrystalline intermediate thin film by sputtering using ion beam assist. It was

Next, an oxide superconducting layer having a thickness of 1.0 μm was formed on the orientation-controlled polycrystalline intermediate thin film by using the laser deposition apparatus shown in FIG. A similar oxide superconducting conductor was produced. During the heat treatment here, no strain was generated in the base material. The oxide superconducting conductor obtained by the above treatment has a thickness of 202.1 μm and a width of 1
It has a length of 0 mm and a length of 10 cm.

The oxide superconducting conductor was cooled, and the critical current density was measured. As a result, the critical current density = 5.2 × 1.
0 ⁵ A / cm ² (77K, 0T), and critical current density per overall = 2.5 × 10 ³ A / cm ² (77
K, 0T) was exhibited, and it was confirmed that extremely excellent superconducting properties were exhibited. Thus, the obtained oxide superconducting conductor does not have distortion in the base material due to a high temperature atmosphere during vapor deposition of the oxide superconducting layer even when a base material having a thin thickness of 0.2 mm is used. It was revealed that the current density was improved.

(Comparative Example 3) An oxide superconducting conductor was produced in the same manner as in Example 3 except that the polycrystalline quick-deposited intermediate thin film was not formed on the lower surface of the base material. The oxide superconducting conductor here had a thickness of 201.6 μm, a width of 10 mm, and a length of 10 cm. As a result of cooling this oxide superconducting conductor and measuring the critical current density, the critical current density = 2.3 ×
Although 10 ⁴ A / cm ² (77K, 0T) was shown, the critical current density per overall = 1.1 × 10 ² A / cm ²
Was low. Also, this oxide superconducting conductor is
The substrate was distorted due to the high temperature atmosphere during the deposition of the oxide superconducting layer.

(Example 4) In the same manner as in Example 3, polycrystalline quick-deposited intermediate thin films were formed on both surfaces of the substrate. Next, FIG.
Using the ion beam sputtering apparatus having the structure shown in FIG. 3, one of the polycrystalline rapid-deposited intermediate thin films formed on both sides of the substrate in the same manner as in Example 3 was ion-irradiated at the same time as sputtering. Then, a film-forming process was performed for 1 hour to form a YSZ orientation-controlled polycrystalline intermediate thin film having a thickness of 0.1 μm. After that, a YSZ orientation-controlled polycrystalline intermediate thin film having a thickness of 0.1 μm was formed on the other polycrystalline accelerated intermediate thin film in the same manner as described above.

Then, on the orientation-controlled polycrystalline intermediate thin films on both sides of the substrate, an oxide superconducting layer having a thickness of 1.0 μm was formed in the same manner as in Example 1 by using the laser vapor deposition apparatus shown in FIG. To form an oxide superconducting conductor similar to that shown in FIG. During the heat treatment here, no strain was generated in the base material. The oxide superconducting conductor obtained by the above treatment has a thickness of 203.2 μm, a width of 0.5 mm, and a length of 10 cm.
belongs to.

The oxide superconductor was cooled and the critical current density was measured. As a result, the critical current density = 4.8 × 1.
0 ⁵ A / cm ² (77K, 0T), and critical current density per overall = 4.7 × 10 ³ A / cm ² (77
K, 0T) was exhibited, and it was confirmed that extremely excellent superconducting properties were exhibited. Thus, the obtained oxide superconducting conductor does not have distortion in the base material due to a high temperature atmosphere during vapor deposition of the oxide superconducting layer even when a base material having a thin thickness of 0.2 mm is used. It was revealed that the current density was about twice as large as that of the oxide superconducting conductor of Example 3.

Example 5 Hastelloy tape having a width of 10 mm, a thickness of 0.2 mm and a length of 80 cm was used as a base material,
The thickness of the YSZ orientation control polycrystalline intermediate thin film formed on the upper surface of the base material is 0.7 μm, and the thickness on the lower surface of the base material is 0.7 μm.
A thin film laminate was obtained in substantially the same manner as in Example 1 except that the YSZ orientation-controlled polycrystalline intermediate thin film of m was formed by the ion beam assisted sputtering method. Then, an oxide superconducting layer having a thickness of 1.0 μm was formed on one of the orientation-controlled polycrystalline intermediate thin films by using the laser vapor deposition apparatus having the configuration shown in FIG. 7, and an oxide superconducting conductor similar to that shown in FIG. 10 was produced. .

(Comparative Example 4) A laminate was obtained in the same manner as in Example 5 except that the orientation controlling polycrystalline intermediate thin film was not formed on the lower surface of the substrate. Then, an oxide superconducting layer having a thickness of 1.0 μm was formed on the YSZ orientation control polycrystalline intermediate thin film having a thickness of 0.7 μm formed on the upper surface of the base material by using the laser deposition apparatus having the configuration shown in FIG. An oxide superconducting conductor similar to that shown in FIG. 14 was produced.

The thin film laminate obtained in Example 5 and the laminate obtained in Comparative Example 4 were heated at 900 to 950 ° C. and moved at 1 m / h to obtain the surface shape along the width direction. The warp state was investigated by measuring. FIG. 11 shows the profile of the surface shape of the thin film laminate obtained in Example 5. Further, FIG. 12 shows the profile of the surface shape of the laminate obtained in Comparative Example 4. In FIGS. 11 and 12, the horizontal axis represents the length in the width direction (μm), and the vertical axis represents the height in the thickness direction (angstrom).

The curvature radius of the warp can be calculated from the profile of the surface shape by the following equation (I). R = (X ² + Y ² ) / 2Y (I) In the formula I, R is the radius of curvature, X is the length in the width direction (μm) when the height in the profile of the surface shape is the peak, Y Represents the height in the thickness direction (angstrom) when the height in the profile of the surface shape has a peak.

In the thin film laminate of Example 5, X = 4 from FIG.
Since 500 (μm) and Y = | −100,000 | (angstrom), substituting these into the formula I gives R =
It was 964 (cm). On the other hand, in the laminated body of Comparative Example 4, from FIG. 12, X = 4500 (μm), Y = 400,
Since it is 000 (angstrom), when these are substituted into the formula I, R = 25.3 (cm). From this, the thin film laminate obtained in Example 5 (where the orientation-controlled polycrystalline intermediate thin film was formed on both sides of the substrate) was the laminate obtained in Comparative Example 4 (only one side of the substrate was controlled in orientation). It was found that the radius of curvature was larger and the amount of warpage was smaller than that of the one in which the crystalline intermediate thin film was formed).

The oxide superconducting conductors obtained in Example 5 and Comparative Example 4 were Ag-coated on the central portion side of the oxide superconducting conductors by a sputtering device, and Ag electrodes were formed on both end sides. Form and Ag
After the coating, a heat treatment was performed at 500 ° C. for 2 hours in a pure oxygen atmosphere to obtain a measurement sample. Then, these samples were cooled to 77 K with liquid nitrogen, and the critical current (Ic) in each length direction in each sample under the condition of an external magnetic field of 0 T (Tesla).
The result of measurement is shown in FIG. In FIG. 13, the solid line indicates the critical current for each position in the length direction of the oxide superconducting conductor obtained in Example 5, and the broken line indicates the length direction of the oxide superconducting conductor obtained in Comparative Example 4. It shows the critical current for each position.

As is clear from FIG. 13, the oxide superconducting conductor obtained in Comparative Example 4 has a critical current in the length direction of 15 A or less at any position, and the length of the base material is long. It can be seen that an oxide superconducting thin film having poor superconducting properties in the direction is formed. On the other hand, Example 5
The oxide superconducting conductor obtained in the above step has a characteristic that the critical current in the length direction is 18 A or more at any position. Furthermore, the average value of the critical current of the oxide superconducting conductor of this Example 5 is It is found that the oxide superconducting thin film having the superconducting property in the longitudinal direction of the base material is about twice as large as that of Comparative Example 4, and thus the superconducting thin film is formed.

[0076]

As described above, in the oxide superconducting conductor of the present invention, the intermediate thin films are formed on both surfaces of the tape-shaped base material, and the orientation-controlled polycrystalline intermediate thin film is oxidized on these intermediate thin films. Since the superconducting layer is formed, even if the thickness of the tape-shaped substrate is thin, the substrate is supported by the intermediate thin films on both sides. Strain in the material is suppressed. This reduces distortion in the intermediate thin film on the base material and improves the flatness of the surface of the orientation-controlled polycrystalline intermediate thin film, so that the crystal of the oxide superconducting layer formed on the orientation-controlled polycrystalline intermediate thin film is improved. The orientation becomes good, and the critical current density becomes excellent. Therefore, in the oxide superconducting conductor of the present invention, since the tape-shaped base material having a small thickness can be used, the thickness of the oxide superconducting conductor can be reduced, and the overall (the oxide superconducting conductor total cross-sectional area) can be obtained. There is an advantage that the critical current density per unit can be improved, and a long oxide superconducting conductor having a large current capacity can be easily provided. Further, in the oxide superconducting conductor of the present invention, since the intermediate thin films formed on both surfaces of the base material function as an insulating layer, it suffices to further form an insulating layer only on the oxide superconducting layer side, and used as a magnet or the like. In this case, it is possible to roll in as it is without forming an insulating layer.

In particular, in an oxide superconducting conductor in which the intermediate thin film is composed of two layers of a polycrystalline rapid-deposited thin film and an orientation-controlled polycrystalline thin film, the polycrystalline rapid-deposited intermediate thin film and the orientation-controlled polycrystalline intermediate thin film are combined. The film thickness of the orientation-controlled polycrystalline intermediate thin film, which takes a long time to form a film, is smaller than that of the entire film thickness of the orientation-controlled polycrystalline intermediate thin film. The film formation time is shortened.

Further, in an oxide superconducting conductor in which an oxide superconducting layer is formed on both sides of a base material via an intermediate thin film, the critical current density per overall (total cross-sectional area of oxide superconducting conductor) is based on The oxide superconducting conductor has an oxide superconducting layer formed on only one side of the material, which is about twice as much, and the critical current density per overall is large, making it easy to use a long oxide superconducting conductor with a larger current capacity. Has the advantage that it can be provided to. Further, in the case where the grain boundary tilt angle of each of a large number of crystal grains forming the orientation-controlled polycrystalline intermediate thin film is 30 degrees or less, the oxide superconducting layer formed on the orientation-controlled polycrystalline intermediate thin film is Since the crystal orientation becomes better, more excellent superconducting properties are exhibited.

Further, in the case where the orientation control polycrystalline intermediate thin films on both sides of the base material are formed by the ion beam assisted sputtering method, the compressive stress is generated by the orientation control polycrystalline intermediate thin films on both sides although the compressive stress is applied. Since the substrate is prevented from warping because it is canceled out, and the polycrystalline quick-deposited intermediate thin film and the orientation control polycrystalline intermediate thin film are formed on the lower surface (heated surface) of the substrate, Oxidation is prevented. This facilitates uniform heating of the surface of the thin film stack when depositing the oxide superconducting layer on the orientation-controlled polycrystalline intermediate thin film, and there is almost no unevenness in the temperature distribution on the surface of the thin film stack. Since the temperature is stable, it is possible to form an oxide superconducting layer having stable superconducting properties in the length direction of the substrate. Therefore, according to the oxide superconducting conductor of the present invention, the warp does not occur in the base material due to the compressive stress at the time of forming the orientation-controlled polycrystalline intermediate thin film, and the oxide superconducting material having stable superconducting properties in the longitudinal direction of the base material is obtained. Even if a thin tape-shaped base material is used, the base material is less likely to be distorted by the high temperature atmosphere at the time of vapor deposition of the oxide superconducting layer. It is possible to provide an oxide superconducting conductor having at least one of the characteristics that the critical current density is improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first example of an oxide superconducting conductor according to the present invention.

FIG. 2 is a configuration diagram showing an example of a high-frequency sputtering apparatus that is preferably used for manufacturing an oxide superconducting conductor according to the present invention and that forms a polycrystalline rapid-deposited intermediate thin film on a substrate.

FIG. 3 is a configuration diagram showing an example of an ion beam sputtering apparatus that is preferably used for manufacturing an oxide superconducting conductor according to the present invention and forms an orientation-controlled polycrystalline intermediate thin film on a substrate.

FIG. 4 is a cross-sectional view showing an example of an ion gun used in the device shown in FIG.

FIG. 5 is an explanatory diagram showing an angular relationship between an incident angle of an ion beam and a cubic crystal lattice when a film forming process is performed together with ion beam irradiation.

FIG. 6 is a structural diagram showing a thin film laminate of an oxide superconducting conductor according to the present invention.

FIG. 7 is a configuration diagram showing an example of an apparatus for forming an oxide superconducting layer on an orientation-controlled polycrystalline intermediate thin film, which is preferably used for producing an oxide superconducting conductor according to the present invention.

FIG. 8 is a cross-sectional view showing a second example of an oxide superconducting conductor according to the present invention.

FIG. 9 is a sectional view showing a third example of an oxide superconducting conductor according to the present invention.

FIG. 10 is a cross-sectional view showing another example of the oxide superconductor according to the present invention.

FIG. 11 is a profile of the surface shape of the thin film laminate obtained in Example 5.

FIG. 12 is a profile of the surface shape of the laminate obtained in Comparative Example 4.

13 is a graph showing the critical current for each position in the length direction of the oxide superconducting conductors obtained in Example 5 and Comparative Example 4. FIG.

FIG. 14 is a cross-sectional view showing an example of a conventional oxide superconducting conductor.

[Explanation of symbols]

 20, 90, 100 ... Oxide superconducting conductor, 21 ... Base material, 22, 22a, 22b ... Polycrystalline rapid intermediate thin film, 23, 23a, 23b ... Orientation control polycrystalline intermediate thin film, 24, 24a , 24b ... Oxide superconducting layer.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical location H01B 13/00 565 H01L 39/24 Z H01L 39/24 ZAAB ZAA C04B 35/00 ZAA (72) Inventor Mariko Hosaka 1-5-1, Kiba, Koto-ku, Tokyo In Fujikura Co., Ltd. (72) Inventor Nobuyuki Kata 1-5-1, Kiba, Koto-ku, Tokyo In Fujikura, Co. (72) Inventor Kono, Saito Koto, Tokyo 1-5-1, Kiba, ward Fujikura stock company

Claims (7)

[Claims] 1. A tape-shaped base material, an orientation-controlled polycrystalline intermediate thin film formed on one surface of the base material and having a large number of crystal grains bonded to each other, and on the other surface of the base material. An oxide superconducting conductor comprising the formed polycrystalline rapid-moving intermediate thin film and an oxide superconducting layer formed on the orientation-controlled polycrystalline intermediate thin film. 2. A tape-shaped substrate, an orientation-controlled polycrystalline intermediate thin film formed on both surfaces of the substrate and having a large number of crystal grains bonded to each other, and formed on this orientation-controlled polycrystalline intermediate thin film. Oxide superconducting conductor, comprising: 3. A tape-shaped base material, a polycrystalline quick-deposition intermediate thin film formed on both surfaces of this base material and having a large number of crystal grains bonded to each other, and one of these polycrystal rapid-deposition intermediate thin films. An oxide superconducting conductor comprising an orientation-controlled polycrystalline intermediate thin film formed on a crystallized rapid-moving intermediate thin film, and an oxide superconducting layer formed on the orientation-controlled polycrystalline intermediate thin film. 4. A tape-shaped base material, a polycrystalline quick-deposition intermediate thin film formed on both surfaces of this base material and having a large number of crystal grains bonded to each other, and formed on each of these polycrystalline fast-deposition intermediate thin films. An oxide superconducting conductor comprising: an orientation-controlled polycrystalline intermediate thin film; and an oxide superconducting layer formed on each of the orientation-controlled polycrystalline intermediate thin films. 5. The oxide superconductor according to claim 1, wherein a large number of crystal grains forming the orientation-controlled polycrystalline intermediate thin film have a grain boundary inclination angle of 30 degrees or less. Characteristic oxide superconducting conductor. 6. The oxide superconducting conductor according to any one of claims 1 to 5, wherein the intermediate thin film is made of yttrium-stabilized zirconia. 7. The oxide superconducting conductor according to claim 2, wherein the orientation-controlled polycrystalline intermediate thin film is formed by an ion beam assisted sputtering method.