JP3771012B2 - Oxide superconducting conductor - Google Patents

Description

【００４７】
実施例１〜２は、臨界電流値、臨界電流密度の値が良好である。また、図７のＸ線回折の結果において、拡散防止層が基材の上方に向けてｃ軸配向していることが確認され、図８のＸ線極点図の結果では、拡散防止層の結晶配向性が優れていることが確認される。更に、図９のＸ線極点図の結果では、酸化物超電導層の結晶配向性が優れていることを示している。
従って、拡散防止層の結晶配向性が高いために、酸化物超電導層の結晶配向性も高くなり、臨界電流値、臨界電流密度の値が良好になったものと思われる。
【００４８】
また、比較例１では、超電導特性が大きく劣化している。図１０のＸ線極点図の結果からは酸化物超電導層の結晶配向性が高いことが示される。
しかし、拡散防止層が形成されていないために、図１１のエネルギー分散型Ｘ線分析の結果から、酸化物超電導層から配向制御多結晶中間薄膜へＢａ原子の拡散が起きていることが明らかであり、酸化物超電導層の結晶構造が崩れたことによる超電導特性の劣化が起きたものと考えられる。
【００４９】
なお、本発明の技術範囲は上記実施の形態に限定されるものではなく、本発明の趣旨を逸脱しない範囲において種々の変更を加えることが可能である。例えば、上述の実施の形態においては、拡散防止層としてＹ₂Ｏ₃とＣｅＯ₂の例を示したが、これに限定されるものではなく、結晶構造が立方晶系であり、その格子定数が、配向制御多結晶中間薄膜を形成する結晶の格子状数に近いものであれば、どのようなものでも可能である。
【００５０】
【発明の効果】
以上、詳細に説明したように、本発明の酸化物超電導導体は、配向制御多結晶中間薄膜と酸化物超電導層との間に、拡散防止層が形成されたものであるので、酸化物超電導層からの元素の拡散が起こらず、結晶構造が崩れることがないので、良好な超電導特性を示すことができる。
また、本発明の酸化物超電導導体は、その拡散防止層がＹ₂Ｏ₃とＣｅＯ₂の少なくとも一つからなり、拡散防止層の結晶配向性が優れ、それに伴って酸化物超電導層の結晶配向性が優れるので、良能な超電導特性を示すことができる。
【図面の簡単な説明】
【図１】 本発明の実施の形態である酸化物超電導導体を示す斜視断面図である。
【図２】 本発明の実施の形態である酸化物超電導導体を製造するための装置であって、配向制御多結晶中間薄膜を形成するためのイオンビームスパッタ装置を示す構成図である。
【図３】 図２に示す装置に用いられるイオンガンを示す構成図である。
【図４】 本発明の実施の形態である酸化物超電導導体を製造するための装置であって、拡散防止層と酸化物超電導層とを形成するためのレーザ蒸着装置を示す構成図である。
【図５】 本発明の実施の形態である酸化物超電導導体を製造するための装置であって、拡散防止層を形成するための高周波スパッタリング装置を示す構成図である。
【図６】 本発明の実施の形態である酸化物超電導導体を製造するための装置であって、酸化物超電導層を形成するためのレーザ蒸着装置を示す構成図である。
【図７】 実施例で得られた酸化物超電導導体の拡散防止層のＸ線回折の結果を示す図であって、（ａ）は実施例１の測定結果を示す図であり、（ｂ）は実施例２の測定結果を示す図である。
【図８】 実施例で得られた酸化物超電導導体の拡散防止層のＸ線極点図であって、（ａ）は実施例１の測定結果を示す図であり、（ｂ）は実施例２の測定結果を示す図である。
【図９】 実施例で得られた酸化物超電導導体の酸化物超電導層のＸ線極点図であって、（ａ）は実施例１を示す図であり、（ｂ）は実施例２を示す図である。
【図１０】 比較例１で得られた酸化物超電導導体の酸化物超電導層のＸ線極点図を示す図である。
【図１１】 比較例１で得られた酸化物超電導導体の断面を分析した結果を示す図であって、（ａ）は酸化物超電導層の配向制御多結晶中間薄膜との界面付近のエネルギー分散型Ｘ線分析結果を示す図であり、（ａ）は配向制御多結晶中間薄膜の酸化物超電導層との界面付近のエネルギー分散型Ｘ線分析結果を示す図である。
【図１２】 従来の酸化物超電導導体を示す斜視断面図である。
【符号の説明】
２０ 酸化物超電導導体
２１ 基材
２２ 配向制御多結晶中間薄膜
２３ 拡散防止層
２４ 酸化物超電導層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an oxide superconductor.
[0002]
[Prior art]
An oxide superconductor discovered in recent years is an excellent superconductor exhibiting a critical temperature higher than the liquid nitrogen temperature. However, there are various problems in using this oxide superconductor. One problem is that the critical current density of oxide superconductors is low.
[0003]
This problem is largely due to the presence of electrical anisotropy in the crystal of the oxide superconductor, and the oxide superconductor easily conducts electricity in the a-axis direction and the b-axis direction of its crystal axis. However, it is difficult for electricity to flow in the c-axis direction. Therefore, in order to form an oxide superconductor on a substrate and use it as a superconductor, an oxide superconductor with good crystal orientation is formed on the substrate, and the oxide is directed in the direction in which electricity flows. It is necessary to orient the a-axis or b-axis of the superconductor crystal and the c-axis in the other direction.
[0004]
As described above, in order to use an oxide superconductor as a conductor, it is necessary to form an oxide superconducting layer with good crystal orientation on a long substrate such as a tape. However, when the oxide superconducting layer is directly formed on the base material of the metal tape, the metal tape itself is polycrystalline and its crystal structure is greatly different from that of the oxide superconductor. Cannot be formed.
[0005]
Therefore, the present inventors formed an orientation control polycrystalline intermediate thin film 2 such as yttrium-stabilized zirconia (YSZ) on a base material 1 made of a metal tape such as a Hastelloy tape as shown in FIG. On the polycrystalline intermediate thin film 2, the critical temperature is about 90K among oxide superconductors, and Y has excellent stability.₁Ba₂Cu_ThreeVarious attempts have been made to produce the oxide superconducting conductor 10 having excellent superconducting characteristics by forming the Ox-based superconducting layer 3.
Among such attempts, the present inventors have previously described Japanese Patent Application No. 3-126836, Japanese Patent Application No. 3-126837, Japanese Patent Application No. 3-205551, Japanese Patent Application No. 4-13443, and Japanese Patent Application No. Hei. Patent applications are filed in Japanese Patent No. 4-293464.
[0006]
According to the techniques described in these patent applications, when forming an orientation-controlled polycrystalline intermediate thin film on one side of a metal tape base material by a sputtering apparatus, an ion beam is applied from the oblique direction of the base film forming surface simultaneously with sputtering. An orientation-controlled polycrystalline intermediate thin film excellent in crystal orientation can be formed by a method of forming an orientation-controlled polycrystalline intermediate thin film while irradiating (ion beam assisted sputtering method).
According to this method, the grain boundary tilt angle formed by the a-axis or b-axis of each crystal lattice of a large number of crystal grains forming the orientation-controlled polycrystalline intermediate thin film can be adjusted to 30 degrees or less, and the crystal orientation can be improved. An excellent orientation controlled polycrystalline intermediate thin film can be formed. Furthermore, if a YBaCuO-based superconducting layer is formed on this intermediate thin film by a laser vapor deposition method or the like, the oxide superconducting layer has excellent crystal orientation and an oxide superconducting layer having a high critical current density. Can be formed.
[0007]
[Problems to be solved by the invention]
However, in the oxide superconducting conductor as described above, it is necessary to heat the base material having the orientation controlled polycrystalline intermediate thin film when forming the oxide superconducting layer.₂O_ThreeIn the case where a zirconia (YSZ) film stabilized by the above method is used, the Ba atoms in the oxide superconducting layer are aligned at the interface between the orientation control polycrystalline intermediate thin film and the oxide superconducting layer by this heating. A phenomenon of diffusion into the crystal intermediate thin film occurs.
Specifically, in the vicinity of the interface between the oxide superconducting layer and the orientation-controlled polycrystalline intermediate thin film, a region in which Ba atoms do not exist is generated. On the other hand, near the interface between the orientation-controlled polycrystalline intermediate thin film and the oxide superconducting layer. The diffused Ba atom is ZrO in YSZ.₂Reacts with BaZrO_ThreeA phase mainly composed of (BZO) is formed.
For this reason, the crystal structure of a part of the oxide superconducting layer collapses, and there is a problem that deterioration of superconducting characteristics cannot be prevented.
[0008]
  The present invention has been made in order to solve the above-described problems, and prevents the Ba atoms of the oxide superconducting layer from diffusing into the orientation-controlled polycrystalline intermediate thin film.ofAn object of the present invention is to provide an oxide superconducting conductor having excellent superconducting properties by preventing collapse.
[0009]
[Means for Solving the Problems]
  In order to achieve the above object, the following configuration was adopted.
  The oxide superconducting conductor according to claim 1 is formed on a surface of a tape-like base material and a plurality of crystal grains bonded to each other, and each grain boundary inclination angle of the plurality of crystal grains. Is 30 degrees or lessConsists of YSZAn orientation control polycrystalline intermediate thin film, a diffusion prevention layer formed on the orientation control polycrystalline intermediate thin film, and formed on the diffusion prevention layerIncluding BaIt has no oxide superconducting layer.In the diffusion preventing layer, a large number of fine crystal grains having a cubic structure are joined and integrated with each other through a crystal grain boundary, and the c-axis of each fine crystal grain is relative to the upper surface of the substrate. The a-axis and the b-axis are oriented in the same plane and oriented in-plane, and the a-axis or b-axis is joined and integrated within an angle of 30 degrees. The c axis of the diffusion prevention layer is aligned with the c axis direction of the orientation control polycrystalline intermediate thin film, and the a axis and b axis of the diffusion prevention layer are aligned with the a axis of the orientation control polycrystalline intermediate thin film and Oriented in alignment with the b-axis directionIt is characterized by that.
  The oxide superconductor according to claim 2 is the oxide superconductor according to claim 1, wherein the diffusion preventing layer is Y.₂O₃And CeO₂It consists of at least one of these.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In FIG. 1, an oxide superconducting conductor 20 has an orientation control polycrystalline intermediate thin film 22 formed by bonding a large number of crystal grains on the upper surface of a tape-like substrate 21, and the orientation control polycrystalline intermediate thin film 22 is formed on the orientation control polycrystalline intermediate thin film 22. A diffusion prevention layer 23 is formed, and an oxide superconducting layer 24 is formed on the diffusion prevention layer 23.
[0011]
As a constituent material of the base material 21, a long metal tape such as a nickel alloy such as stainless steel, copper, or hastelloy can be used. The base material 21 has a thickness of 0.01 to 0.5 mm, preferably 0.02 to 0.15 mm.
If the thickness of the base material 21 exceeds 0.5 mm, it is thicker than the thickness of the oxide superconducting layer 24, and the critical current density per overall (total cross-sectional area of the oxide superconducting conductor) is reduced. On the other hand, when the thickness of the base material 21 is less than 0.01 mm, the strength of the base material is lowered, and the reinforcing effect of the oxide superconducting conductor 20 is lost.
[0012]
The orientation-controlled polycrystalline intermediate thin film 22 is formed by joining and integrating a large number of fine crystal grains in which crystals having a cubic crystal structure are joined together via a crystal grain boundary, and c of the crystal axis of each crystal grain. The axes are oriented substantially perpendicular to the upper surface (film formation surface) of the substrate 21, and the a-axis and the b-axis of each crystal grain are oriented in the same plane in the same direction. . It is preferable that the a-axis (or b-axis) of the crystals of each crystal grain be joined and integrated with an angle formed between them (grain boundary inclination angle K) within 30 degrees. The orientation controlled polycrystalline intermediate thin film 22 has a thickness of 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 1.0 μm or more, film formation becomes difficult, and an increase in the effect cannot be expected.
On the other hand, if the thickness of the orientation-controlled polycrystalline intermediate thin film 22 is less than 0.1 μm, the diffusion preventing layer 23 may not be sufficiently supported because it is too thin.
The constituent materials for this orientation-controlled polycrystalline intermediate thin film include MgO, YSZ, SrTiO._ThreeEtc. can be used.
[0013]
  The diffusion prevention layer 23 is a collection of crystals having a cubic crystal structure.Fine grainAre joined and integrated with each other through crystal grain boundaries.Fine grainThe c-axis of the crystal axis is oriented substantially perpendicular to the upper surface (film formation surface) of the substrate 21,Fine grainThe a-axis and the b-axis of the crystal axes are oriented in the same direction in the same direction. eachFine grainThe a-axis (or b-axis) of the crystal is preferably joined and integrated with the angle (grain boundary inclination angle K) formed by them within 30 degrees. The thickness of the diffusion preventing layer is 0.01 to 1 μm, preferably 0.05 to 0.5 μm. Even if the thickness of the diffusion preventing layer is 1 μm or more, it becomes difficult to form a film, and an increase in the effect cannot be expected.
  In the present invention, when the thickness of the diffusion preventing layer is less than 0.01 μm, Ba atoms in the oxide superconducting layer 24 diffuse into the orientation control polycrystalline intermediate thin film 22 and the crystal structure of the oxide superconducting layer 24 is destroyed. It becomes clear from the experiments of those skilled in the art, and the critical current density of the oxide superconducting conductor 20 is lowered.
  If the lattice constant of the crystal forming the diffusion prevention layer 23 is close to the lattice constant of the crystal forming the orientation controlled polycrystalline intermediate thin film, the constituent material of the diffusion prevention layer 23 is c of the crystal of the diffusion prevention layer 23. The axes are aligned in alignment with the c-axis direction of the crystal of the orientation-controlled polycrystalline intermediate thin film 22, and the a-axis and b-axis of the crystal of the diffusion prevention layer 23 are aligned with the a-axis and b of the crystal of the orientation-controlled polycrystalline intermediate thin film 22. This is preferable in that it can be aligned in alignment with the axial direction.
  Therefore, for example, when a YSZ film is formed as the orientation-controlled polycrystalline intermediate thin film 22, the lattice constant of YSZ is 5.139, so that the lattice constant is 10.604.₂O₃And CeO whose lattice constant is 5.411₂By using this, it is possible to form the diffusion prevention layer 23 having excellent crystal orientation.
  The diffusion prevention layer 23 is Y₂O₃Or CeO₂Is not limited to one layer of Y, Y₂O₃And CeO₂With two layers and Y₂O₃And CeO₂And a mixed layer.
[0014]
  The oxide superconducting layer 24 isY ₁ B a ₂ Cu ₃ O _x , Y ₂ B a ₄ Cu ₈ O _x , Y ₃ B a ₃ Cu ₆ O _x The composition, or Tl ₂ Ba ₂ Ca ₂ Cu ₃ O x , Tl ₁ Ba ₂ Ca ₂ Cu ₃ O _x , Tl ₁ Ba ₂ Ca ₃ Cu ₄ O _x CompositionIt is made of a superconducting material with a high critical temperature represented by The oxide superconducting layer 24 has a thickness of about 0.5 to 5 μm.
[0015]
The apparatus for forming the orientation controlled polycrystalline intermediate thin film 22 is an ion beam sputtering apparatus shown in FIG. 2 provided with an ion beam assist ion gun.
The apparatus of this example is mainly configured by a base material holder 45 that holds the base material 21, a plate-like target 46, an ion gun 47, and a sputter beam irradiation device 48. In the figure, reference numeral 49 denotes a target holder, 55 denotes a feeding device for the tape-like base material 21, 56 denotes a winding device for the base material 21, and the base material 21 is fed from the feeding device 55 onto the base material holder 45. The film can be continuously formed on the substrate 21 by winding with the winding device 56.
[0016]
Moreover, the apparatus of this example is accommodated in a vacuum container (not shown), and the periphery of the base material 21 can be maintained in a vacuum atmosphere. An atmosphere gas supply source such as a gas cylinder is connected to the vacuum vessel, and the inside of the vacuum vessel is set to a low pressure state such as a vacuum and an inert gas atmosphere such as argon gas or an inert gas atmosphere containing oxygen. It can be done.
[0017]
The base material holder 45 includes a heater inside, and can heat the base material 21 as necessary. Further, the base material holder 45 is provided with an angle adjustment mechanism D composed of an upper support plate 60, a lower support plate 61, and a base 62.
Note that the angle adjustment mechanism D may be attached to the support portion of the ion gun 47 to adjust the tilt angle of the ion gun 47 and adjust the incident angle of the ion beam.
[0018]
The target 46 is used to form a target orientation controlled polycrystalline intermediate thin film, and the target 46 has the same composition as that of the orientation controlled polycrystalline intermediate thin film having the target composition or an approximate composition. Specifically, MgO or Y₂O_ThreeStabilized zirconia (YSZ), MgO, SrTiO_ThreeHowever, the present invention is not limited to this, and a target suitable for the orientation controlled polycrystalline intermediate thin film to be formed may be used as appropriate.
[0019]
In FIG. 3, the ion gun 47 is configured to include an extraction electrode 66, a filament 67, and an introduction tube 68 for Ar gas or the like inside a cylindrical container 65, and ions are collimated in a beam shape from the tip of the container 65. It can be irradiated.
[0020]
  As shown in FIG. 2, the ion gun 47 has its central axis S with respect to the upper surface (film formation surface) of the substrate 21 and an incident angle θ (an angle formed between the normal (normal) of the substrate 21 and the center line S). So they are inclined and face each other. The incident angle θ is preferably in the range of 50 to 60 degrees, and most preferably in the range of 55 to 60 degrees.
  The ion beam applied to the substrate 21 by the ion gun 47 is He.⁺, Ne⁺, Ar⁺, Xe⁺, Kr⁺An ion beam of a rare gas such as, or a mixed ion beam of them 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 atomic weight is required, and Ar⁺, Kr⁺It is preferable to use ions such as
  The sputter beam irradiation device 48 has the same configuration as the ion gun 47, and can irradiate the target 46 with the ion beam and knock out the constituent particles of the target 46 toward the substrate 21.
[0021]
The case where the YSZ orientation-controlled polycrystalline intermediate thin film 22 is formed on the surface of the tape-shaped substrate 21 using the apparatus having the above-described configuration will be described.
A YSZ target is used as the target 46, and an ion beam from the ion gun 47 can be irradiated on the upper surface of the substrate 21 at an angle in the range of 50 to 60 degrees. Next, the inside of the container containing the base material 21 is depressurized.
[0022]
The target 46 is irradiated with an ion beam from the sputter beam irradiation device 48, the constituent particles of the target 46 are knocked out, and the constituent particles hit from the target 46 are deposited on the substrate 21, and at the same time, Ar ions and By irradiating a mixed ion beam of oxygen ions, an orientation-controlled polycrystalline intermediate thin film 22 having a desired thickness is formed, and a thin film stack 25 is obtained.
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.
By performing sputtering while irradiating an ion beam at such an incident angle, the a-axis and b-axis of the YSZ orientation control polycrystalline intermediate thin film 22 formed on the substrate 21 can be aligned. it can.
[0023]
An apparatus for forming the oxide superconducting conductor 20 by forming the diffusion preventing layer 23 and the oxide superconducting layer 24 on the thin film laminate 25 uses a laser deposition apparatus shown in FIG.
The laser vapor deposition apparatus 70 of this example has a processing vessel 71. In the vapor deposition chamber 72 inside the processing vessel 71, the thin film stack 25, a diffusion prevention layer target 73a, and an oxide superconducting layer target 73b. With. That is, a base 74 is provided in the vapor deposition chamber 72, and the thin film laminate 25 can be installed on the upper surface of the base 74, and the diffusion prevention layer and the oxide superconductor supported by the support holder 73. Layer targets 73a, 73b are provided. In the figure, reference numeral 75 denotes a delivery device for the thin film laminate 25, and 76 denotes a winding device for the thin film laminate 25. Further, the processing container 71 is connected to the vacuum exhaust device 77 through the exhaust hole 77a and can be depressurized to a predetermined pressure.
[0024]
  The target 73a of the diffusion preventing layer is composed of a plate body such as a composite oxide sintered body containing a composition that is equivalent or close to that of the diffusion preventing layer 23 to be formed or a component that easily escapes during film formation. It has become.
  Therefore, the target 73a of the diffusion prevention layer is Y₂O₃And CeO₂Therefore, it is preferable to use a layer having the same or similar composition.
  The oxide superconducting layer target 73b has a composition equivalent to or close to that of the oxide superconducting layer 24 to be formed, or a composite oxide sintered body or oxide containing many components that easily escape during film formation. It consists of a plate such as a superconductor.
  Therefore, the target 73b of the oxide superconducting layer isY ₁ B a ₂ Cu ₃ O _x , Y ₂ B a ₄ Cu ₈ O _x , Y ₃ B a ₃ Cu ₆ O _x The composition, or Tl ₂ Ba ₂ Ca ₂ Cu ₃ O _x , Tl ₁ Ba ₂ Ca ₂ Cu ₃ O _x , Tl ₁ Ba ₂ Ca ₃ Cu ₄ O _x CompositionTherefore, it is preferable to use the same or similar composition.
[0025]
The base 74 has a built-in heater so that the thin film stack 25 can be heated. On the other hand, a laser light emitting device 78, a first reflecting mirror 79, a condensing 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 light emitting device 78 is transmitted through a transparent window. The target 73 can be focused and irradiated via 82. As long as the laser light emitting device 78 can knock out the constituent particles from the targets 73a and 73b, a YAG laser, CO₂Any laser or excimer laser may be used.
[0026]
On the YSZ orientation-controlled polycrystalline intermediate thin film 22,₂O_ThreeIn order to form the diffusion preventive layer 23, the thin film stack 25 is placed on the base 74 with the orientation-controllable polycrystalline intermediate thin film 22 side up, and the diffusion preventive layer target 73a is Y.₂O_ThreeThe target is set and the vapor deposition chamber 72 is depressurized. Here, the thin film laminate 25 may be heated by operating the heater of the base 74.
Next, the laser beam is focused and irradiated onto the target 73 a of the diffusion prevention layer while the thin film stack 25 is being wound by the winder 76. As a result, the constituent particles of the target 73 a are extracted or evaporated, and the particles are deposited on the orientation-controlled polycrystalline intermediate thin film 22. Here, since the crystal grains of the orientation controlled polycrystalline intermediate thin film 22 are preliminarily c-axis oriented during the deposition of the constituent particles and are also oriented along the a axis and the b axis, they are formed on the orientation controlled polycrystalline intermediate thin film 22. The c-axis, a-axis, and b-axis of the crystal of the diffusion preventing layer 23 are epitaxially grown and crystallized so as to match the orientation-controlled polycrystalline intermediate thin film 22. As a result, Y with good crystal orientation₂O_ThreeThe diffusion preventing layer 23 is obtained.
[0027]
Next, Y₂O_ThreeY on the anti-diffusion layer 23₁Ba₂Cu_ThreeO_XIn order to form the oxide superconducting layer 24 of Y, Y₂O_ThreeThe thin film laminate 25 having the diffusion prevention layer 23 formed thereon and wound by the winder 76 is placed on the base 74 with the diffusion prevention layer 23 side up, and the target Y is used as the target 73b of the oxide superconducting layer.₁Ba₂Cu_ThreeO_XThe target is set and the vapor deposition chamber 72 is depressurized. Here, the vapor deposition chamber 72 may be an oxygen atmosphere. Further, the thin film laminate 25 may be heated by operating the heater of the base 74.
[0028]
  The laser beam is focused and irradiated onto the target 73b of the oxide superconducting layer while the thin film stack 25 with the diffusion preventing layer 23 is sent out from the winder 76. As a result, the constituent particles of the target 73 b are extracted or evaporated, and the particles are deposited on the diffusion preventing layer 23. Here, during the deposition of the constituent particles, the diffusion preventing layer 23Fine grainIs pre-c-axis oriented, and is also oriented along the a-axis and b-axis, so that the c-axis, a-axis, and b-axis of the oxide superconducting layer 24 are epitaxially grown and crystallized so that the diffusion preventing layer 23 is also aligned. To do. As a result, Y with good crystal orientation₁Ba₂Cu₃O_XThe oxide superconducting layer 24 is obtained. Note that heat treatment for adjusting the crystal structure of the oxide superconducting layer 24 may be performed as necessary after film formation.
  When the oxide superconducting layer 24 is formed on the diffusion preventing layer 23 by the above-described method, an oxide superconducting conductor 20 as shown in FIG. 1 is obtained.
  The oxide superconducting layer 24 formed on the diffusion preventing layer 23 is in a polycrystalline state. In each of the crystal grains of the oxide superconducting layer 24, electricity is supplied in the thickness direction of the base material 21. The c-axis that is difficult to flow is oriented, and the crystal orientation is good because the a-axis or the b-axis is oriented in the plane direction of the substrate 21. Therefore, the obtained oxide superconducting layer 24 is excellent in quantum connectivity at the crystal grain boundary and has little deterioration in superconducting characteristics at the crystal grain boundary, so that electricity can easily flow in the plane direction of the base material 21 and has an excellent critical current density. Can be obtained.
[0029]
As another method for manufacturing the oxide superconducting conductor 20 by forming the diffusion prevention layer 23 and the oxide superconducting layer 24 on the thin film laminate 25, the following apparatus and manufacturing method are used. Also good.
[0030]
FIG. 5 shows a high-frequency sputtering apparatus for forming the diffusion prevention layer 23.
The apparatus of this example is mainly composed of a holder 31 that holds the thin film laminate 25 and a plate-like target 32. Reference numeral 33 in the figure denotes a target holder. The target holder 33 is connected to a high-frequency power source 34, and the high-frequency power source 34 and the above-described holder 31 are grounded. In the figure, reference numeral 35 denotes a feeding device for the tape-like thin film laminate 25, and 36 denotes a winding device for the thin film laminate 25.
[0031]
The holder 31 and the target holder 33 are housed in a vacuum container (not shown) so that the periphery of the holder 31 and the target holder 33 can be maintained in a vacuum atmosphere. Furthermore, the vacuum vessel can be in a low pressure state such as a vacuum and an inert gas atmosphere such as an argon gas or an inert gas atmosphere containing oxygen as necessary.
With the above configuration, plasma can be generated in the upper space of the thin film stack 25 by operating the high frequency power supply 34 after reducing the pressure inside the vacuum vessel, and the particles of the target 32 are sputtered by the action of the plasma. Thus, it can be blown toward the thin film laminate 25 side.
[0032]
The holder 31 includes a heater inside so that the thin film stack 25 can be heated.
The target 32 is composed of a plate body such as a composite oxide sintered body containing a composition equivalent to or close to that of the diffusion preventing layer 23 to be formed, or containing many components that are easily escaped during film formation. Therefore, the target 32 of the diffusion preventing layer is Y₂O_ThreeAnd CeO₂Therefore, it is preferable to use a layer having the same or similar composition.
[0033]
On the YSZ orientation control polycrystalline intermediate thin film 22 using the apparatus having the above structure,₂O_ThreeIn order to form the diffusion preventing layer 23 of Y,₂O_ThreeThe inside of the vacuum vessel in which the thin film laminate 25 is housed is used as a reduced pressure atmosphere. Then, the high frequency power supply 34 is operated, and the constituent particles of the target 32 are sputtered and fly onto the thin film stack 25. If this particle is deposited for a required time, a desired thickness of Y on the YSZ orientation-controlled polycrystalline intermediate thin film 22 is obtained.₂O_ThreeThe diffusion preventing layer 23 can be formed.
[0034]
Next, an apparatus and a method for manufacturing the oxide superconducting conductor 20 by forming the oxide superconducting layer 24 on the diffusion preventing layer 23 will be described.
FIG. 6 shows a laser deposition apparatus for forming an oxide superconducting layer by a film forming method.
In this figure, the same reference numerals are assigned to the components shown in FIG. 4 described above, and the description thereof is omitted.
The laser vapor deposition apparatus 91 of this example can install the thin film stack 26 having the diffusion prevention layer 23 and the target 90 in the vapor deposition chamber 72 inside the processing vessel 71.
[0035]
  The target 90 has a composition equivalent to or close to that of the oxide superconducting layer to be formed, or a composite oxide sintered body or a plate body such as an oxide superconductor containing many components that easily escape during film formation. It is made up of.
  Therefore, the target 90 isY ₁ B a ₂ Cu ₃ O _x , Y ₂ B a ₄ Cu ₈ O _x , Y ₃ B a ₃ Cu ₆ O x The composition, or Tl ₂ Ba ₂ Ca ₂ Cu ₃ O _x , Tl ₁ Ba ₂ Ca ₂ Cu ₃ O _x , Tl ₁ Ba ₂ Ca ₃ Cu ₄ O _x CompositionSince it is used to form an oxide superconducting layer having a high critical temperature represented by
[0036]
Next, Y₂O_ThreeY on the anti-diffusion layer 23₁Ba₂Cu_ThreeO_XIn order to form the oxide superconducting layer 24, the thin film laminate 26 having the diffusion preventing layer is placed on the base 74, and the target 90 is Y₁Ba₂Cu_ThreeO_XThe target is set and the vapor deposition chamber 72 is depressurized. Here, the vapor deposition chamber 72 may be an oxygen atmosphere as necessary. Alternatively, the thin film stack 26 may be heated by operating the heater of the base 74.
[0037]
Next, the target 90 is focused and irradiated with a laser beam. As a result, the constituent particles of the target 90 are extracted or evaporated, and the particles are deposited on the diffusion preventing layer 23. Note that heat treatment for adjusting the crystal structure of the oxide superconducting layer 24 may be performed as necessary after film formation.
When the oxide superconducting layer 24 is formed on the diffusion preventing layer 23 by the above-described method, an oxide superconducting conductor 20 as shown in FIG. 1 is obtained.
[0038]
In the above-described oxide superconducting conductor, diffusion of Ba atoms in the oxide superconducting layer is prevented by forming the diffusion preventing layer between the orientation controlled polycrystalline intermediate thin film and the oxide superconducting layer. An oxide superconducting conductor having an excellent critical current density can be obtained without destroying the crystal structure of the superconducting layer.
Further, even if the amount of heat received by the oxide superconducting layer increases during the formation of the oxide superconducting layer, Ba atoms do not diffuse, and the heating temperature during the formation of the oxide superconducting layer can be increased, or the film formation time can be reduced. The thickness of the oxide superconductive layer can be set freely.
[0039]
In the oxide superconductor described above, the orientation-controlled polycrystalline intermediate thin film is formed so as to be crystallized. Therefore, when the diffusion prevention layer is formed on the orientation-controlled polycrystalline intermediate thin film, diffusion is performed. The prevention layer is formed by epitaxial growth, and a diffusion prevention layer having excellent crystal orientation can be obtained.
Furthermore, since the oxide superconducting layer is epitaxially grown on the diffusion preventing layer having excellent crystal orientation, an oxide superconducting layer having excellent crystal orientation can be obtained.
In this case, the diffusion preventing layer is Y₂O_ThreeAnd CeO₂If it consists of one of these, the diffusion prevention layer excellent in crystal orientation can be formed.
[0040]
Furthermore, in the above-described oxide superconducting conductor, when the diffusion prevention layer is formed by a laser vapor deposition method, the oxide superconducting layer can be formed continuously in one apparatus at the same time, thus simplifying the manufacturing process. The manufacturing cost of the oxide superconducting conductor can be reduced.
In addition, a long oxide superconductor can be easily manufactured.
[0041]
Furthermore, in the above-described oxide superconductor, when the diffusion prevention layer is formed by the RF sputtering method, a large area diffusion prevention layer can be formed, and a plurality of tapes can be formed by one film formation. Since the film can be formed, the manufacturing time of the oxide superconducting conductor can be greatly shortened.
[0042]
【Example】
(Example 1)
A base material of Hastelloy C276 tape having a width of 10 mm, a thickness of 0.2 mm, and a length of 10 cm is installed in the ion beam sputtering apparatus shown in FIG.^-FourThe target is made of YSZ (stabilized zirconia), the sputtering voltage is 1000 V, the sputtering current is 100 mA, the ion beam incident angle is 55 degrees, and the ion source assist voltage is 300 V. The ion beam current density is 20 μA / cm.^-2The film was processed for 6 hours by performing ion source irradiation at the same time as sputtering on the surface of the base material to form a 0.7 μm-thick YSZ orientation controlled polycrystalline intermediate thin film in which the crystal orientation was controlled. . The current density of the ion beam is based on the measured numerical value of a current density measuring device installed near the sample.
Next, using a laser deposition apparatus shown in FIG.₂O_ThreeA diffusion prevention layer of Y, and further Y₂O_ThreeAn oxide superconducting layer having a thickness of 0.6 μm was formed on the diffusion preventing layer.
First, the inside of the vacuum vessel of the laser deposition apparatus is depressurized to 20 mtorr, the base material temperature is set to 550 to 600 ° C., and Y is used as a target.₂O_ThreeUsing a product made by laser deposition, a 0.4μm thick Y₂O_ThreeA diffusion prevention layer was formed. A Kr-F laser with a wavelength of 248 nm was used as the target evaporation laser. The laser frequency is 100 Hz and the laser irradiation energy is 400 mJ.
Next, Y as target_0.7Ba_1.7Cu_3.0O_7-3A target made of an oxide superconductor having a composition of^-FiveAfter reducing the pressure to Toll, oxygen was introduced into the interior to give 2.0 × 10^-3Laser deposition was performed after setting the thickness of the substrate to be 1.0 m / hr and the substrate temperature to 700 to 750 ° C. After this film formation, the thin film was heat-treated at 500 ° C. for 120 minutes in an oxygen atmosphere. As described above, an oxide superconducting conductor having a thickness of about 0.2 mm, a width of 10 mm, and a length of 10 cm was obtained.
[0043]
(Example 2)
In the same manner as in Example 1, after forming a YSZ orientation controlled polycrystalline intermediate thin film in which crystals were controlled on the tape substrate, the YSZ orientation controlled polycrystalline intermediate thin film was used using the high-frequency sputtering apparatus shown in FIG. CeO on top₂An anti-diffusion layer was formed.
The inside of the vacuum vessel of the high frequency sputtering apparatus is 7.7 × 10^-3Depressurize to tall and use CeO as target₂A 0.25 μm thick CeO film was formed on the upper surface of the YSZ-oriented polycrystalline intermediate thin film by setting the sputtering output to 300 W and the substrate temperature to 600 ° C.₂A diffusion prevention layer was formed.
Next, using the laser deposition apparatus shown in FIG.₂An oxide superconducting layer having a thickness of 0.6 μm was formed on the diffusion preventing layer. Y as target_0.7Ba_1.7Cu_3.0O_7-3A target made of an oxide superconductor having a composition of^-6After reducing the pressure to Toll, oxygen was introduced into the interior to give 2.0 × 10^-3Laser deposition was performed after setting the thickness of the substrate to be 1.0 m / hr and the substrate temperature to 700 to 750 ° C. A Kr-F laser with a wavelength of 248 nm was used as the target evaporation laser. After this film formation, the thin film was heat-treated at 500 ° C. for 120 minutes in an oxygen atmosphere. As described above, an oxide superconducting conductor having a thickness of about 0.2 mm, a width of 10 mm, and a length of 10 cm was obtained.
[0044]
(Comparative Example 1)
An oxide superconducting conductor having a thickness of about 0.2 mm, a width of 10 mm, and a length of 10 cm was obtained in the same manner as in Example 2 except that the diffusion prevention layer was not formed.
[0045]
Table 1 shows the values of the critical current value and the critical current density measured under conditions of 77K and 0T after the oxide superconductors obtained in Examples 1 and 2 and Comparative Example 1 were cooled with liquid nitrogen.
Moreover, the measurement result of the X-ray diffraction of the diffusion prevention layer of the oxide superconductor formed in Examples 1 and 2 is shown in FIG. 7, and the X-ray pole figure is shown in FIG.
Furthermore, pole figures of the oxide superconducting layers obtained in Examples and Comparative Examples are shown in FIGS.
[0046]
[Table 1]

[0047]
Examples 1 and 2 have good critical current values and critical current density values. Moreover, in the result of the X-ray diffraction of FIG. 7, it is confirmed that the diffusion preventing layer is c-axis oriented toward the upper side of the substrate, and the result of the X-ray pole figure of FIG. It is confirmed that the orientation is excellent. Furthermore, the result of the X-ray pole figure of FIG. 9 shows that the crystal orientation of the oxide superconducting layer is excellent.
Therefore, it is considered that since the crystal orientation of the diffusion preventing layer is high, the crystal orientation of the oxide superconducting layer is also high, and the critical current value and the critical current density are improved.
[0048]
Further, in Comparative Example 1, the superconducting characteristics are greatly deteriorated. The result of the X-ray pole figure of FIG. 10 shows that the oxide superconducting layer has high crystal orientation.
However, since no diffusion prevention layer is formed, it is clear from the results of the energy dispersive X-ray analysis in FIG. 11 that Ba atoms are diffused from the oxide superconducting layer to the orientation controlled polycrystalline intermediate thin film. It is considered that the superconducting characteristics were deteriorated due to the collapse of the crystal structure of the oxide superconducting layer.
[0049]
The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, Y is used as the diffusion preventing layer.₂O_ThreeAnd CeO₂However, the present invention is not limited to this example, and the crystal structure is cubic, and the lattice constant is close to the number of lattices of crystals forming the orientation controlled polycrystalline intermediate thin film. Anything is possible.
[0050]
【The invention's effect】
As described above in detail, the oxide superconducting conductor of the present invention has a diffusion prevention layer formed between the orientation-controlled polycrystalline intermediate thin film and the oxide superconducting layer. Since no element diffusion occurs from the crystal structure and the crystal structure does not collapse, good superconducting characteristics can be exhibited.
Further, the oxide superconducting conductor of the present invention has a diffusion prevention layer of Y₂O_ThreeAnd CeO₂Since the crystal orientation of the diffusion preventing layer is excellent and the crystal superconductivity of the oxide superconducting layer is excellent accordingly, it is possible to show a good superconducting characteristic.
[Brief description of the drawings]
FIG. 1 is a perspective sectional view showing an oxide superconducting conductor according to an embodiment of the present invention.
FIG. 2 is a configuration diagram showing an ion beam sputtering apparatus for forming an orientation-controlled polycrystalline intermediate thin film, which is an apparatus for manufacturing an oxide superconducting conductor according to an embodiment of the present invention.
FIG. 3 is a configuration diagram showing an ion gun used in the apparatus shown in FIG. 2;
FIG. 4 is a configuration diagram showing a laser vapor deposition apparatus for forming an oxide superconducting conductor according to an embodiment of the present invention, and forming a diffusion prevention layer and an oxide superconducting layer.
FIG. 5 is a configuration diagram showing a high-frequency sputtering apparatus for forming an oxide superconducting conductor according to an embodiment of the present invention and for forming a diffusion prevention layer.
FIG. 6 is a configuration diagram showing a laser vapor deposition apparatus for forming an oxide superconducting layer, which is an apparatus for manufacturing an oxide superconducting conductor according to an embodiment of the present invention.
7 is a diagram showing the result of X-ray diffraction of the diffusion preventing layer of the oxide superconducting conductor obtained in Example, (a) is a diagram showing the measurement result of Example 1, (b) These are figures which show the measurement result of Example 2. FIG.
8 is an X-ray pole figure of the diffusion preventing layer of the oxide superconducting conductor obtained in Example, where (a) is a diagram showing the measurement results of Example 1, and (b) is Example 2. FIG. It is a figure which shows the measurement result.
FIG. 9 is an X-ray pole figure of an oxide superconducting layer of an oxide superconducting conductor obtained in Example, where (a) shows Example 1 and (b) shows Example 2. FIG.
10 is an X-ray pole figure of an oxide superconducting layer of an oxide superconducting conductor obtained in Comparative Example 1. FIG.
FIG. 11 is a diagram showing a result of analyzing a cross section of the oxide superconducting conductor obtained in Comparative Example 1, wherein (a) shows energy dispersion in the vicinity of the interface between the oxide superconducting layer and the orientation-controlled polycrystalline intermediate thin film. It is a figure which shows a type | mold X-ray-analysis result, (a) is a figure which shows the energy dispersion type | mold X-ray-analysis result of the interface vicinity with the oxide superconducting layer of an orientation control polycrystalline intermediate thin film.
FIG. 12 is a perspective sectional view showing a conventional oxide superconducting conductor.
[Explanation of symbols]
20 Oxide superconducting conductor
21 Base material
22 Orientation controlled polycrystalline intermediate thin film
23 Diffusion prevention layer
24 Oxide superconducting layer

Claims (2)

A base material tape, this is formed on a surface of a substrate a number of crystal grains is coupled orientation control multi respective grain boundary inclination angle of said multiple crystal grains consisting of YSZ is 30 degrees or less a crystalline intermediate thin, and the alignment control polycrystalline intermediate thin diffusion barrier layer formed on, Ri name comprises a oxide superconducting layer containing Ba formed in the diffusion preventing layer,
The diffusion prevention layer is formed by joining and integrating a large number of fine crystal grains having a cubic structure with each other through a grain boundary, and the c-axis of each fine crystal grain is substantially perpendicular to the upper surface of the substrate. The a-axis and the b-axis are oriented in the same direction and in-plane oriented, and the a-axis or b-axis are joined and integrated with each other at an angle of 30 degrees or less.
The c axis of the diffusion prevention layer is aligned with the c axis direction of the orientation control polycrystalline intermediate thin film, and the a axis and b axis of the diffusion prevention layer are aligned with the a axis and b axis of the orientation control polycrystalline intermediate thin film. An oxide superconducting conductor characterized by being oriented in alignment with a direction . 2. The oxide superconductor according to claim 1, wherein the diffusion preventing layer is made of at least one of Y ₂ O ₃ and CeO ₂ .

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