JP5481180B2 - Base material for oxide superconductor and oxide superconductor - Google Patents

Description

  The present invention relates to an oxide superconducting substrate and an oxide superconducting conductor.

The RE-123-based oxide superconductor (REBa ₂ Cu ₃ O _7-n : RE is one of rare earth elements including Y) has excellent superconducting properties at liquid nitrogen temperature or higher, and is extremely promising in practical use. There is a strong demand to process this oxide superconductor into a wire and use it as a power supply conductor.
In order to produce this RE-123 oxide superconducting conductor, it is necessary to form an oxide superconducting layer with good crystal orientation on a substrate with high crystal orientation. This is because this kind of rare earth oxide superconductor crystal has an electric anisotropy that it is easy for electricity to flow in the a-axis and b-axis directions of the crystal axis, but it is difficult for electricity to flow in the c-axis direction. It is necessary to make the crystal orientation good also in the base material which is the base for forming the oxide superconducting layer on the base material.

As a base material used for such an RE-123 oxide superconducting conductor, an intermediate layer 110 is laminated on a tape-like metal base material 100 by an IBAD (Ion Beam Assisted Deposition) method as shown in FIG. The formed structure is known (for example, refer to Patent Document 1).
The intermediate layer 110 formed by the above-described IBAD method is a material whose physical characteristic values such as a coefficient of thermal expansion and a lattice constant indicate intermediate values between the metal substrate 100 and the oxide superconducting layer, for example, MgO, YSZ (yttria stabilized zirconium), SrTiO _{3 and the} like are used. Such an intermediate layer 110 functions as a buffer layer that alleviates the difference in physical properties between the metal substrate 100 and the oxide superconducting layer. Further, the film of the intermediate layer 110 has high crystal orientation by being formed by the IBAD method.

For example, as shown in FIG. 6, the intermediate layer 110 is formed by joining a large number of fine crystal grains 120 having a cubic crystal structure via a grain boundary, and the c-axis of the crystal axis of each crystal grain 120. Are oriented at right angles to the upper surface (film formation surface) of the substrate 100, and the a-axes and b-axes of the crystal axes of each crystal grain 120 are oriented in the same direction in the same direction. The a-axes (or b-axes) of the crystal grains 120 are joined and integrated with an angle formed between them (grain boundary inclination angle K shown in FIG. 7) within 30 degrees.
The higher the in-crystal orientation of the intermediate layer 110, the higher the oxide superconducting layer formed thereon, and the higher the in-plane orientation, the more critical current, critical magnetic field, critical An oxide superconductor having excellent superconducting properties such as temperature can be obtained.
In addition, by stacking an intermediate layer, a cap layer made of a metal oxide, and an oxide superconducting layer on the base material of the metal tape, the crystal orientation of the cap layer is further enhanced than that of the intermediate layer, thereby providing excellent crystal orientation. A technique for forming an oxide superconducting layer is also known (see Patent Document 2).

As described above, obtaining a substrate with a high degree of orientation plays an important role in the production of rare earth oxide superconducting conductors. Therefore, the present inventors have been intensively carrying out research and development, and in the process, IBAD Using this method, we are developing a technology for forming an intermediate layer of MgO that exhibits excellent orientation even at a very thin thickness.
In addition, when the present inventors researched an oxide superconducting conductor having a highly oriented oxide superconducting layer, the present inventors also energetically studied the bed layer that is the base of the intermediate layer formed by the IBAD method. proceeding. This bed layer is for the purpose of further enhancing the crystal orientation of the intermediate layer formed thereon by the IBAD method and at the same time suppressing unnecessary element diffusion from the metal substrate during the heat treatment after the formation of the oxide superconducting layer. Provided.

JP 2004-71359 A JP 2008-130255 A

Currently, the oxide superconducting wire is being lengthened, and the length to Km class is required. In order to lengthen the oxide superconducting wire, it goes without saying that an intermediate layer of MgO by the IBAD method (hereinafter sometimes referred to as “IBAD-MgO”) also needs to be formed on the long wire. . However, it is necessary to control the film formation conditions of the intermediate layer such as IBAD-MgO (for example, the ratio of MgO molecules supplied on the film formation surface to assist beam ions) within a very narrow region. If the beam is not stable, it may be difficult to form a highly oriented MgO film stably from the beginning to the end of the long wire. Therefore, even when the assist ion beam is unstable, it is possible to form an intermediate layer such as highly oriented IBAD-MgO, that is, to develop a bed layer that has a characteristic that promotes a wide range of conditions for forming the intermediate layer. Is needed.
Further, the intermediate layer of the oxide superconducting conductor is not limited to IBAD-MgO, and various intermediate layers have been developed by the IBAD method as described above. Therefore, it is desired to provide a bed layer suitable for them.

  The present invention has been made in view of such conventional circumstances, and has the characteristics of enhancing the crystal orientation of the intermediate layer formed by the IBAD method and promoting the film forming conditions of the intermediate layer to be wide. It is an object of the present invention to provide a base material for an oxide superconductor provided with a bed layer and an oxide superconductor using the same.

In order to solve the above-mentioned problems, the inventors of the present application have made extensive studies on the layer structure serving as the foundation of the intermediate layer formed by the IBAD method. As a result, they have found a material useful as a bed layer and have arrived at the present invention.
Namely, oxide superconductor substrate of the present invention, on a metal _substrate, X 2 _{O 3} oxide (X is Yb, Gd, Ho, shows the La or Sm.) And a Y ₂ O ₃ Metropolitan A bed layer made of a mixed oxide in which two or more selected are mixed, and deposited on the bed layer by an ion beam assist method, MgO, yttria stabilized zirconium (YSZ), Gd ₂ Zr ₂ O ₇ , or And an intermediate layer made of any one of CeO ₂ .
In the base material for an oxide superconducting conductor of the present invention, X of the X ₂ O ₃ oxide is preferably Yb or Gd.
In the base material for an oxide superconducting conductor of the present invention, a diffusion preventing layer is preferably interposed between the metal base material and the bed layer.
The base material for an oxide superconducting conductor of the present invention is preferably applied as a base material for an oxide superconducting conductor in which an oxide superconducting layer is laminated on the intermediate layer via a cap layer.
Furthermore, the present invention is, on the oxide superconductor base materials, provided with a cap layer, provides an oxide superconductor comprising comprising an oxide superconducting layer on the cap layer.

According to the present invention, X ₂ O ₃ oxide (X represents Yb, Gd, Ho, La, or Sm) as a base when an intermediate layer such as IBAD-MgO is formed on a metal substrate. Alternatively, by providing a bed layer made of a mixed oxide in which two or more selected from X ₂ O ₃ oxide and Y ₂ O ₃ are mixed, the crystal orientation of an intermediate layer such as an IBAD-MgO layer can be increased. Can be increased. Further, by providing the bed layer having such a configuration, even when the assist ion beam is unstable, an intermediate layer such as highly oriented IBAD-MgO can be formed. It becomes the base material for oxide superconducting conductors provided with a bed layer that has the property of promoting a wide range. Therefore, the crystal orientation of the intermediate layer of the oxide superconducting conductor substrate of the present invention is good, and the crystal orientation of the oxide superconducting layer is excellent by forming a cap layer or oxide superconducting layer thereon. Therefore, it is possible to provide an oxide superconducting conductor having good superconducting characteristics.

It is a block diagram which shows an example of the base material for oxide superconducting conductors which concerns on this invention. It is a block diagram which shows the other example of the base material for oxide superconductors which concerns on this invention. It is a block diagram which shows an example of the oxide superconductor based on this invention. It is a schematic block diagram which shows an example of the apparatus which forms into a film by the ion beam assist method. It is a schematic block diagram which shows an example of the structure of the ion gun applied to the apparatus shown in FIG. It is a block diagram which shows an example of the intermediate | middle layer formed by the IBAD method on the metal tape. It is a block diagram which shows the crystal grain of the intermediate | middle layer formed by IBAD method. 6 is a (220) pole figure of a CeO ₂ layer formed on an IBAD-MgO layer in Reference Example 1. FIG. 10 is a (220) pole figure of a CeO ₂ layer formed on an IBAD-MgO layer in Reference Example 2. FIG. 10 is a (220) pole figure of a CeO ₂ layer formed on an IBAD-MgO layer in Reference Example 3. FIG.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a configuration diagram showing an example of a laminated structure of a base material A for an oxide superconducting conductor according to the present invention. As shown in FIG. 1, the base material A for oxide superconducting conductors of this embodiment includes a metal base material 21 and an X ₂ O ₃ oxide film (X is Yb, Gd, Ho, La or Sm.), Or a bed layer 22 made of a mixed oxide in which two or more selected from X ₂ O ₃ oxide and Y ₂ O ₃ are mixed, and an ion beam assist method (IBAD method) A layered structure including an intermediate layer 23 formed by the above and a cap layer 24 formed thereon, and an oxide superconducting layer is formed on the cap layer 24 as described later. The oxide superconducting conductor is composed of

  As a material constituting the metal substrate 21, 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 (registered trademark) and other nickel-based alloys which 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. In addition, although the tape-shaped thing is used for the metal base material 21 in this embodiment, it is not limited to this, For example, the thing of various shapes, such as a board | plate material, a wire, and a strip body, can be used.

The bed layer 22 has high heat resistance and is intended to further reduce interfacial reactivity, and functions to obtain the orientation of the intermediate layer 23 disposed thereon. The bed layer 22 is an X ₂ O ₃ oxide (X represents Yb, Gd, Ho, La, or Sm), or two or more selected from the X ₂ O ₃ oxide and Y ₂ O ₃ Can be composed of mixed oxides. Specifically, the material constituting the bed layer 22 is Yb ₂ O ₃ , Gd ₂ O ₃ , Ho ₂ O ₃ , La ₂ O ₃ , Sm ₂ O ₃ , Yb ₂ O ₃ —Gd ₂ O ₃ , Y ₂ O ₃ —Yb ₂ O ₃ , Y ₂ O ₃ —Gd ₂ O ₃ , Yb ₂ O ₃ —Ho ₂ O ₃ , Y ₂ O ₃ —Ho ₂ O ₃ , Gd ₂ O ₃ —Ho ₂ O ₃ , Yb ₂ O ₃ —La ₂ O ₃ , Yb ₂ O ₃ —Sm ₂ O ₃ , Y ₂ O ₃ —Sm ₂ O ₃ , Gd ₂ O ₃ —La ₂ O ₃ , Gd ₂ O ₃ —Sm ₂ O ₃ , _{Y 2 O 3 -La 2 O 3} , Ho 2 O 3 -La 2 O 3, Ho 2 O 3 -Sm 2 O 3, La 2 O 3 -Sm 2 O 3, Yb 2 O 3 -Gd 2 O 3 - _{Y 2 O 3, Yb 2 O} 3 -Gd 2 O 3 -Ho 2 O 3, Yb 2 O 3 -Y 2 O 3 -H o ₂ O ₃ , Gd ₂ O ₃ —Y ₂ O ₃ —Ho ₂ O _{3 and the} like. Here, in the mixed oxide constituting the bed layer 22, the mixing ratio of two or more selected from X ₂ O ₃ oxide and Y ₂ O ₃ is not particularly limited and can be appropriately adjusted.

By using the bed layer 22 made of such an X ₂ O ₃ oxide or a mixed oxide in which two or more selected from the X ₂ O ₃ oxide and the Y ₂ O ₃ are mixed, the bed layer 22 is used. The intermediate layer 23 such as IBAD-MgO to be formed can have a higher orientation. Further, by using the bed layer 22 having such a configuration, the intermediate layer 23 such as IBAD-MgO having high orientation can be formed even when the film forming conditions such as the assist ion beam are not stable in the film forming process for a long time. A film can be formed.
Among the materials constituting the bed layer 22 described above, Yb ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O ₃ —Gd ₂ O ₃ , Y ₂ O ₃ —Yb ₂ O ₃ and Y ₂ O ₃ —Gd ₂ O. ₃ has a high effect of improving the crystal orientation of the intermediate layer 23 such as IBAD-MgO formed thereon and an effect of encouraging the film forming conditions of the intermediate layer 23 to be in a wide range. In particular, Yb ₂ O ₃ , Yb ₂ O ₃ —Gd ₂ O ₃ , Y ₂ O ₃ —Yb ₂ O ₃ functions as an excellent bed layer 22.

The thickness of the bed layer 22 is preferably in the range of 6 to 100 nm, and more preferably in the range of 10 to 70 nm. When the thickness of the bed layer 22 is less than 6 nm, the orientation of the intermediate layer 23 of IBAD-MgO formed thereon may be insufficient. Further, when the bed layer 22 is less than 6 nm, element diffusion from the substrate 21 side is performed in the heat treatment after the formation of the oxide superconducting layer described later in the case where only the bed layer 22 is provided on the substrate 21. There is a risk that the suppression effect will be insufficient. On the other hand, when the thickness of the bed layer 22 exceeds 100 nm, the entire layer thickness including the bed layer 22 and the intermediate layer 23 becomes thick, so that the entire film formation takes time, and the manufacturing cost and the manufacturing efficiency are reduced. It is disadvantageous in terms.
Since the crystal orientation of the bed layer 22 is not particularly limited in the present invention, the bed layer 22 does not need to be formed by a special film formation method, and a conventionally known film formation method can be applied. Examples of the film formation method of the bed layer 22 include an ion beam sputtering method, an electron beam vapor deposition method, a pulse laser vapor deposition method (PLD method), and a chemical vapor deposition method (CVD method).

  The intermediate layer 23 is a vapor-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 21 and an oxide superconducting layer described later. In addition, it functions as an orientation control film for controlling the crystal orientation of the cap layer 24 formed thereon. When the intermediate layer 23 is formed, an ion beam assisted sputtering method is carried out using an ion beam assisted sputtering device, which will be described later.

As the material constituting the intermediate layer 23, a material whose physical characteristics indicate intermediate values between the metal substrate 21 and the oxide superconducting conductor film is used. Examples of the material of the intermediate layer 23 include MgO, yttria-stabilized zirconium (YSZ), Gd ₂ Zr ₂ O ₇ , CeO _{2, and the} like. In addition, pyrochlore structure, rare earth-C structure, perovskite An appropriate compound having a mold structure or a fluorite structure can be used. Among these, it is preferable to use MgO, YSZ, or Gd ₂ Zr ₂ O ₇ as the material of the intermediate layer 23. In particular, MgO or Gd ₂ Zr ₂ O ₇ is particularly suitable as a material for the intermediate layer 23 because it can reduce the value of ΔΦ (FWHM: full width at half maximum), which is an index representing the degree of orientation in the IBAD method. In particular, when MgO is used as the material of the intermediate layer 23, it is preferable that the (100) axis is MgO with 4-fold symmetry with the normal direction of the substrate surface.

The film thickness of the intermediate layer 23 can be in the range of 1 to 1000 nm (1.0 μm), for example, about several nm, but is not limited to these ranges and values. In _particular, X 2 _{O 3} oxide, or _by using the X 2 _{O 3} oxide and _Y 2 bed layer _{22 O 3} 2 or more selected from the consisting of mixed mixed oxide of the intermediate layer 23 Even if the film thickness is reduced, it is possible to obtain a film having a good crystal orientation, and when the intermediate layer 23 is IBAD-MgO, a film having a good crystal orientation can be reliably generated with a film thickness of several nm or more.
When the film thickness of the intermediate layer 23 exceeds 1.0 μm, the deposition time of the IBAD method used as the film formation method of the intermediate layer 23 is relatively low, so that the film formation time of the intermediate layer 23 becomes long and economical. Disadvantageous.
On the other hand, if the thickness of the intermediate layer 23 is less than 1 nm, it becomes difficult to control the crystal orientation of the intermediate layer 23 itself, and it becomes difficult to control the degree of orientation of the cap layer 24 formed thereon, It becomes difficult to control the degree of orientation of the oxide superconducting layer formed on the layer 24. As a result, the oxide superconductor may have an insufficient critical current.

The cap layer 24 has a function of controlling the orientation of the oxide superconducting layer provided on the cap layer 24, diffuses the elements constituting the oxide superconducting layer into the intermediate layer 23, and uses a gas and an intermediate used during film formation. It has a function of suppressing reaction with the layer 23.
In particular, the cap layer 24 undergoes a process of epitaxial growth with respect to the surface of the intermediate layer 23, grain growth (overgrowth) in the lateral direction (plane direction), and selective growth of crystal grains in the in-plane direction. A film that is self-orientated is preferably formed. The cap layer 24 that is selectively grown in this manner can have a higher degree of in-plane orientation than the intermediate layer 23.

The material constituting the cap layer 24 is not particularly limited as long as it can exhibit such a function. For example, CeO ₂ , LaMnO ₃ , SrTiO ₃ , Y ₂ O ₃ , Al ₂ O _{3 and the} like are used. Is preferred.
When CeO ₂ is used as the constituent material of the cap layer 24, the cap layer 24 does not need to be entirely composed of CeO ₂ , and Ce-M in which a 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 24 varies depending on its constituent material. For example, when the cap layer 24 is composed of CeO ₂ , the range of 50 to 5000 nm, more preferably the range of 100 to 5000 nm, etc. may be exemplified. it can. If the film thickness of the cap layer 24 is out of these ranges, a sufficient degree of orientation may not be obtained.
The cap layer 24 can be formed by a pulse laser deposition method (PLD method), a sputtering method, or the like, but it is desirable to use the PLD method from the viewpoint of obtaining a high film formation rate.
In addition, in this embodiment, although the base material A for oxide superconductors which has the cap layer 24 was illustrated, this invention is not limited to this, The structure which does not have the cap layer 24 is also possible.

  Moreover, the base material for oxide superconducting conductors according to the present invention is not limited to the structure shown in FIG. 1, and as shown in FIG. 2, in addition to the configuration shown in FIG. A laminated structure in which a diffusion preventing layer 19 is interposed therebetween may be employed.

The diffusion prevention layer 19 is formed for the purpose of preventing the constituent element diffusion of the metal base material 21,
It is made of silicon nitride (Si ₃ N ₄ ), aluminum oxide (Al ₂ O ₃ , also referred to as “alumina”), rare earth metal oxide, or the like, and has a thickness of, for example, 10 to 400 nm.
When the thickness of the diffusion preventing layer 19 is less than 10 nm, there is a possibility that the diffusion of the constituent elements of the metal substrate 21 cannot be sufficiently prevented. On the other hand, when the thickness of the diffusion preventing layer 19 exceeds 400 nm, the internal stress of the diffusion preventing layer 19 increases, and thereby, each layer constituting the base material B for oxide superconducting conductor is easily separated from the metal base material 21. There is a risk of becoming.
Further, since the crystallinity of the diffusion preventing layer 19 is not particularly limited, it may be formed by a film forming method such as a normal sputtering method.

As described above, the two-layer structure of the diffusion prevention layer 19 and the bed layer 22 is inevitably required when another layer such as the intermediate layer 23 or an oxide superconducting layer described later is formed on the bed layer 22. This is to prevent diffusion of a part of the constituent elements of the metal base material 21 to the oxide superconducting layer side through the bed layer 22 when receiving a heat history as a result of being heated or heat-treated. By adopting a two-layer structure of the layer 19 and the bed layer 22, element diffusion from the metal substrate 21 side can be effectively suppressed.
In the present invention, the laminated structure interposed between the metal substrate 21 and the intermediate layer 23 is not limited to the two-layer structure of the diffusion prevention layer 19 and the bed layer 22.

FIG. 3 shows an example of the oxide superconducting conductor according to the present invention. The oxide superconducting conductor 30 of this embodiment is formed on the oxide superconducting layer on the cap layer 24 of the base material B for oxide superconducting conductor. 37 and a stabilization layer 38 are formed.
As a material of the oxide superconducting layer 37, an RE-123 oxide superconductor (REBa ₂ Cu ₃ O _7-n : RE is a rare earth element such as Y, La, Nd, Sm, Eu, Gd) is used. it can. Among the RE-123-based oxides, Y123 (YBa ₂ Cu ₃ O _7-n ) or Gd123 (GdBa ₂ Cu ₃ O _7-n ) can be preferably used, but other oxide superconductors such as Of course, it is also possible to use a material made of another oxide superconductor having a high critical temperature typified by a composition of (Bi, Pb) ₂ Ca ₂ Sr ₃ Cu ₄ O _x .
The oxide superconducting layer 37 has a thickness of about 0.5 to 5 μm and preferably a uniform thickness. The oxide superconducting layer 37 can be formed by a film forming method such as a PLD method, a sputtering method, or a TFA-MOD method (an organic metal deposition method using trifluoroacetate, a coating pyrolysis method). The film quality of the oxide superconducting layer 37 is preferably uniform, and the c-axis, a-axis, and b-axis of the crystal of the oxide superconducting layer 37 are epitaxially grown and crystallized so as to match the crystal of the cap layer 24. Thus, the crystal orientation is excellent.

  The stabilizing layer 38 is formed for the purpose of stabilizing the superconducting characteristics of the oxide superconducting layer 37, and is made of a highly conductive metal material such as Ag, an Ag alloy, or Cu. In the present embodiment, the oxide superconducting conductor 30 having the stabilization layer 38 is exemplified. However, the present invention is not limited to this, and a configuration without the stabilization layer 38 is also possible.

Next, the manufacturing method of the base material for oxide superconducting conductors having the above structure will be described.
First, a long metal base 21 such as a tape made of the above-mentioned material is prepared, and an ion beam sputtering method, an electron beam vapor deposition method, a pulsed laser vapor deposition method (PLD method), a chemical is formed on the metal base material 21. A diffusion prevention layer 19 such as Al ₂ O ₃ or Y ₂ O ₃ is formed by a film forming method such as a vapor deposition method (CVD method).
Next, an X ₂ O ₃ oxide or an X ₂ O film is formed by a film forming method such as an ion beam sputtering method, an electron beam evaporation method, a pulse laser evaporation method (PLD method), or a chemical vapor deposition method (CVD method). _A bed layer 22 made of a mixed oxide in which two or more selected from _three oxides and Y ₂ O ₃ are mixed is formed.
Next, an intermediate layer 23 such as MgO is formed by the IBAD method. Further, the cap layer 4 is formed on the intermediate layer 23 by a reactive DC sputtering method using a metal target.
In the description of this embodiment, the case where the intermediate layer 23 is formed by an ion beam assist sputtering apparatus and an ion beam assist method (IBAD method) using the ion beam assist sputtering apparatus will be described below.

First, a film forming apparatus using the IBAD method used in this embodiment will be described.
FIG. 4 shows an example of an apparatus for producing an intermediate layer (IBAD-MgO or the like) by the IBAD method. The apparatus of this example has a configuration in which an ion gun for ion beam assist is provided in a sputtering apparatus. .
This film forming apparatus includes a base material holder 51 that holds a base material A on which a bed layer 22 is formed on a metal base material 21, and a plate-like shape that is disposed diagonally above the base material holder 51 at a predetermined interval. The target 52 is opposed to the base holder 51 obliquely above the base holder 51 at a predetermined interval and is spaced apart from the target 52, and the sputter is disposed below the target 52 toward the lower surface of the target 52. The beam irradiation device 54 is mainly configured. Reference numeral 55 in the drawing denotes a target holder that holds the target 52.
The apparatus shown in FIG. 4 is housed in a vacuum container (not shown) so that the periphery of the substrate A can be maintained in a vacuum atmosphere. Further, an atmospheric gas supply source such as a gas cylinder is connected to the vacuum container, the inside of the vacuum container is in a low pressure state such as a vacuum, and an inert gas containing argon gas or other inert gas atmosphere or oxygen The atmosphere can be changed.

When a long metal tape is used as the base material A (metal base material 21), a metal tape feeding device and a winding device are provided inside the vacuum container, and the base material holder 51 is continuously provided from the feeding device. It is preferable that the substrate A is fed out and then wound up by a winding device so that a polycrystalline thin film can be continuously formed on the tape-like substrate.
The base material holder 51 includes a heater inside, and the base material A positioned on the base material holder 51 can be heated to a desired temperature. In addition, an angle adjustment mechanism that can adjust the horizontal angle of the substrate holder 51 is attached to the bottom of the substrate holder 51. An angle adjustment mechanism may be attached to the ion gun 53 to adjust the tilt angle of the ion gun 53 to adjust the ion irradiation angle.

The target 52 is for forming the target intermediate layer 23, and has the same composition as the polycrystalline thin film having the target composition or an approximate composition. Specifically, MgO, GZO, or the like is used as the target 52, but is not limited thereto, and a target that matches the polycrystalline thin film to be formed may be used.
The ion gun 53 is configured such that a gas to be ionized is introduced into a container and a lead electrode is provided on the front surface. And it is an apparatus which ionizes one part of the atom or molecule | numerator of gas, and irradiates the ionized particle | grain as an ion beam controlled by the electric field generated with the extraction electrode. There are various types of ionization of gas, such as a high frequency excitation method and a filament type. The filament type is a method in which a tungsten filament is energized and heated to generate thermoelectrons and collide with gas molecules in a high vacuum to be ionized. The high-frequency excitation method ionizes gas molecules in a high vacuum by polarization with a high-frequency electric field.
In the present embodiment, an ion gun 53 having an internal structure shown in FIG. 5 is used. The ion gun 53 includes an extraction electrode 57, a filament 58, and an introduction tube 59 for Ar gas or the like inside a cylindrical container 56, and can irradiate ions in parallel in a beam shape from the tip of the container 56. It is.

As shown in FIG. 4, the ion gun 53 is opposed to the upper surface of the base material A (the upper surface of the bed layer 22 on the metal base material 21; the film formation surface) with an inclination angle θ. Yes. The inclination angle θ is preferably in the range of 30 to 60 degrees, but in the case of MgO, around 45 degrees is particularly preferable. Accordingly, the ion gun 53 is arranged so as to irradiate ions with an inclination angle θ with respect to the upper surface of the substrate A. The ions irradiated onto the base material A after the bed layer is formed by the ion gun 53 are ions of rare gases such as He ⁺ , Ne ⁺ , Ar ⁺ , Xe ⁺ , Kr ⁺ , or mixed ions of these and oxygen ions. Good.
The sputter beam irradiation device 54 has the same configuration as that of the ion gun 53, and can irradiate the target 52 with ions to knock out the constituent particles of the target 52. In the device of the present invention, since it is important that the constituent particles of the target 52 can be knocked out, a voltage is applied to the target 52 with a high-frequency coil or the like so that the constituent particles of the target 52 can be knocked out. The sputter beam irradiation device 54 may be omitted.

Next, the case where the intermediate layer 23 of MgO is formed on the bed layer 22 on the metal substrate 21 using the apparatus having the above-described configuration will be described. In order to form the intermediate layer 23 on the bed layer 22 on the metal substrate 21, an MgO target is used and ions irradiated from the ion gun 53 are adjusted on the upper surface of the substrate holder 51 by adjusting the angle adjustment mechanism. It will be able to irradiate at an angle of around degrees. Next, the inside of the container containing the substrate is evacuated to form a reduced pressure atmosphere. Then, the ion gun 53 and the sputter beam irradiation device 54 are operated.
When the target 52 is irradiated with ions from the sputtering beam irradiation device 54, the constituent particles of the target 52 are knocked out and fly onto the bed layer 22. Then, the constituent particles knocked out from the target 52 are deposited on the bed layer 22 and at the same time, a mixed ion of Ar ions and oxygen ions is irradiated from the ion gun 53. For example, when forming MgO, the irradiation angle θ at the time of ion irradiation can be set to a range of about 45 degrees.

By the above method, an IBAD-MgO layer can be formed on the bed layer 22 with a good crystal orientation even if it is thin. In this embodiment, _X 2 _{O 3} oxide is a good base for the generation of IBAD-MgO layer, _or, two or more selected from X 2 _{O 3} oxide and _Y 2 _{O 3} are mixed Since the bed layer 22 made of the mixed oxide is provided, an IBAD-MgO layer having sufficient crystal orientation can be formed even with a very thin film thickness of about several nm to 50 nm.

It should be noted that a cap layer 24 such as CeO _{2 is formed} on the IBAD-MgO layer (intermediate layer 23) by a normal film formation method so that the surface of the IBAD-MgO intermediate layer 23 having excellent crystal orientation is formed. On the other hand, the film is grown through the process of epitaxial growth, grain growth (overgrowth) in the lateral direction (plane direction), and selective growth of crystal grains in the in-plane direction. The cap layer 24 having an inner orientation degree can be obtained.

In the structure of this embodiment therefore, X ₂ O ₃ oxide, or, X ₂ O ₃ by providing the oxide and Y ₂ O ₃ bed layer 22 2 or more selected consists mixed mixed oxide from Thus, even with the IBAD-MgO intermediate layer 23 having a film thickness of only a few nm to 20 nm, a cap layer 24 such as CeO ₂ having good crystal orientation can be formed thereon.
Moreover, in the oxide superconducting conductor formed using the base materials A and B for the oxide superconducting conductor, the total thickness of the film formed on the metal base material 21 can be suppressed. The film formation time in manufacturing can be reduced, which contributes to reduction in manufacturing cost.

According to the present invention, X ₂ O ₃ oxide (X represents Yb, Gd, Ho, La, or Sm) as a base when an intermediate layer such as IBAD-MgO is formed on a metal substrate. Alternatively, by providing a bed layer made of a mixed oxide in which two or more selected from X ₂ O ₃ oxide and Y ₂ O ₃ are mixed, the crystal orientation of an intermediate layer such as an IBAD-MgO layer can be increased. Can be increased. Further, by providing the bed layer having such a configuration, even when the assist ion beam is unstable, an intermediate layer such as highly oriented IBAD-MgO can be formed. It becomes the base material for oxide superconducting conductors provided with a bed layer that has the property of promoting a wide range. Therefore, the crystal orientation of the intermediate layer of the oxide superconducting conductor substrate of the present invention is good, and the crystal orientation of the oxide superconducting layer is excellent by forming a cap layer or oxide superconducting layer thereon. Therefore, it is possible to provide an oxide superconducting conductor having good superconducting characteristics.

EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further in detail, this invention is not limited to these Examples.
( Reference Examples 1-5, Examples 6-14 , and Comparative Examples 1-7)
On a long tape-shaped Hastelloy (registered trademark) metal substrate having a width of 1 cm, an Al ₂ O ₃ diffusion prevention layer was formed by sputtering. The film formation temperature of the Al ₂ O ₃ layer was room temperature and the film thickness was 100 nm.
Next, on the Al ₂ O ₃ diffusion prevention layer, the materials shown in Tables 1 and 2 were formed as a bed layer with a film thickness shown in the same table by ion beam sputtering.
Subsequently, each sample having a diffusion prevention layer and a bed layer formed on a metal substrate is irradiated with assist beam ions at an incident angle of 45 ° using an MgO target by the IBAD method. The target particles were knocked out by irradiation with an ion beam, and a four-fold symmetric IBAD-MgO intermediate layer was formed on the bed layer of each sample. The intermediate layer of IBAD-MgO was formed with a film thickness of 5 nm and an assist ion gun current value of 900 mA.

Next, in order to perform X-ray positive electrode point measurement of MgO (220) on these samples, an MgO layer having a thickness of 200 nm is formed on the IBAD-MgO intermediate layer by ion beam sputtering. The epitaxial film was formed. For each of the obtained samples, X-ray positive electrode point measurement of MgO (220) was performed, and the in-plane orientation degree ΔΦ of the uppermost epitaxially grown MgO layer was measured. The results are shown in Tables 1 and 2.
For each sample in which a diffusion prevention layer, a bed layer, and an IBAD-MgO intermediate layer were sequentially formed on the metal substrate prepared above, a pulsed laser deposition method (PLD) was formed on the IBAD-MgO intermediate layer. Method), a 450 nm CeO ₂ cap layer was formed at 800 ° C. Then, a X-ray positive pole measurement of CeO 2 ₍₂₂₀₎ of the cap layer was measured in-plane orientation degree .DELTA..PHI. The results are shown in Tables 1 and 2. Also, it is shown in Figures 8-10 a _CeO 2 (220) pole figure of the cap layer of Reference Example 1-3. In Table 1, “x” indicates non-orientation.

8 to 10 and Tables 1 and 2, in Reference Examples 1 to 5 and Examples 6 to 14 according to the present invention, X ₂ O ₃ oxide, or X ₂ O ₃ oxide and Y ₂ O are used. by providing a bed layer 2 species selected from ₂ consists mixed mixed oxide, an intermediate layer of crystalline orientation of good IBAD-MgO was obtained. In Reference Examples 1 to 5 and Examples 6 to 14 , CeO ₂ having a good crystal orientation was obtained by directly forming CeO ₂ on the intermediate layer of 4-fold symmetrical IBAD-MgO having a thickness of only 5 nm. _Two cap layers were obtained. Therefore, if an oxide superconducting layer is formed on this cap layer, the crystal orientation of the oxide superconducting layer can be improved so as to follow the crystal orientation of the cap layer. It is clear that an oxide superconducting layer can be formed and an oxide superconducting conductor having good superconducting properties can be provided.

( Reference Examples 15 to 17 and Comparative Example 8)
In the same manner as in Reference Examples 1 to 5, Examples 6 to 14 and Comparative Examples 1 to 7, Al ₂ O ₃ diffusion prevention layer (film thickness 100 nm), Table 3 on Hastelloy (registered trademark) metal substrate A sample in which a bed layer of the above material and thickness was sequentially formed was prepared. Next, on the bed layer of each sample, except that the current value of the assist ion gun was reduced by 30%, in the same manner as in Reference Examples 1 to 5, Examples 6 to 14 and Comparative Examples 1 to 7, A 4-fold symmetrical IBAD-MgO intermediate layer was formed to a thickness of 5 nm.
For each of the obtained samples, the in-plane orientation degree ΔΦ of the epitaxially grown MgO layer and the in-plane of the CeO ₂ cap layer in the same manner as in Reference Examples 1 to 5, Examples 6 to 14 and Comparative Examples 1 to 7. The degree of orientation ΔΦ was measured. The results are shown in Table 3.

From the results in Table 3, in Reference Examples 15 to 17 according to the present invention, even when the current value of the assist ion gun is reduced by 30% and the film formation conditions are deteriorated, IBAD-MgO having a good crystal orientation is obtained. An intermediate layer was obtained. Therefore, according to the present invention, it is apparent that a substrate for an oxide superconductor provided with a bed layer having a characteristic that promotes a wide range of film forming conditions for the intermediate layer can be provided.
In Reference Examples 15 to 17, a CeO ₂ cap layer with good crystal orientation was obtained by directly forming CeO ₂ on the intermediate layer of 4-fold symmetric IBAD-MgO having a thickness of only 5 nm. It was. Therefore, if an oxide superconducting layer is formed on this cap layer, the crystal orientation of the oxide superconducting layer can be improved so as to follow the crystal orientation of the cap layer. It is clear that an oxide superconducting layer can be formed and an oxide superconducting conductor having good superconducting properties can be provided.

  A, B: base material for oxide superconductor, 19: anti-diffusion layer, 21: metal base material, 22 ... bed layer, 23 ... intermediate layer, 24 ... cap layer, 30 ... oxide superconductor, 37 ... oxide Superconducting layer, 38 ... stabilizing layer, 52 ... target, 53 ... ion gun.

Claims (5)

On a metal _substrate, X 2 _{O 3} oxide (X is, Yb, Gd, Ho, shows the La or Sm.) And from Y ₂ O ₃ Metropolitan mixed oxides of two or more are mixed is selected from And an intermediate layer made of any one of MgO, yttria-stabilized zirconium (YSZ), Gd ₂ Zr ₂ O ₇ , and CeO _{2 formed} on the bed layer by an ion beam assist method. A base material for oxide superconducting conductors. The base for an oxide superconducting conductor according to claim 1, wherein X of the X ₂ O ₃ oxide is Yb or Gd.   The base material for an oxide superconducting conductor according to claim 1 or 2, wherein a diffusion preventing layer is interposed between the metal base material and the bed layer.   The oxide superconductor according to any one of claims 1 to 3, wherein an oxide superconducting layer is laminated on the intermediate layer via a cap layer and applied as a base material of an oxide superconducting conductor. Conductor base material. On the oxide superconductor base materials according to claim 1, comprising a cap layer, an oxide superconductor, characterized in that it comprises an oxide superconducting layer on the cap layer .

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