JP7518519B2 - Superconductor and manufacturing method thereof - Google Patents
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- 238000004519 manufacturing process Methods 0.000 title claims description 29
- 239000002243 precursor Substances 0.000 claims description 58
- 239000000758 substrate Substances 0.000 claims description 53
- 238000000034 method Methods 0.000 claims description 51
- 238000010304 firing Methods 0.000 claims description 33
- 229910052751 metal Inorganic materials 0.000 claims description 31
- 239000011248 coating agent Substances 0.000 claims description 30
- 238000000576 coating method Methods 0.000 claims description 30
- 150000001875 compounds Chemical class 0.000 claims description 24
- 239000002245 particle Substances 0.000 claims description 24
- 238000010438 heat treatment Methods 0.000 claims description 16
- 241000954177 Bangana ariza Species 0.000 claims description 15
- 229910052688 Gadolinium Inorganic materials 0.000 claims description 11
- 229910052727 yttrium Inorganic materials 0.000 claims description 11
- 229910052726 zirconium Inorganic materials 0.000 claims description 11
- 229910052788 barium Inorganic materials 0.000 claims description 10
- 229910052692 Dysprosium Inorganic materials 0.000 claims description 8
- 229910052691 Erbium Inorganic materials 0.000 claims description 8
- 229910052693 Europium Inorganic materials 0.000 claims description 8
- 229910052779 Neodymium Inorganic materials 0.000 claims description 8
- 229910052777 Praseodymium Inorganic materials 0.000 claims description 8
- 229910052772 Samarium Inorganic materials 0.000 claims description 8
- 229910052769 Ytterbium Inorganic materials 0.000 claims description 8
- 229910052802 copper Inorganic materials 0.000 claims description 8
- 229910052735 hafnium Inorganic materials 0.000 claims description 8
- 229910052689 Holmium Inorganic materials 0.000 claims description 7
- 229910052718 tin Inorganic materials 0.000 claims description 7
- 229910052684 Cerium Inorganic materials 0.000 claims description 6
- 229910052741 iridium Inorganic materials 0.000 claims description 6
- 229910052758 niobium Inorganic materials 0.000 claims description 6
- 229910052719 titanium Inorganic materials 0.000 claims description 6
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- 238000001354 calcination Methods 0.000 claims description 2
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- 230000015572 biosynthetic process Effects 0.000 description 6
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- 125000004432 carbon atom Chemical group C* 0.000 description 5
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- 238000002360 preparation method Methods 0.000 description 4
- 229910052702 rhenium Inorganic materials 0.000 description 4
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 3
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- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
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- 229910052737 gold Inorganic materials 0.000 description 2
- 239000010931 gold Substances 0.000 description 2
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- REHQLKUNRPCYEW-UHFFFAOYSA-N 1-methylcyclohexane-1-carboxylic acid Chemical compound OC(=O)C1(C)CCCCC1 REHQLKUNRPCYEW-UHFFFAOYSA-N 0.000 description 1
- HNNQYHFROJDYHQ-UHFFFAOYSA-N 3-(4-ethylcyclohexyl)propanoic acid 3-(3-ethylcyclopentyl)propanoic acid Chemical compound CCC1CCC(CCC(O)=O)C1.CCC1CCC(CCC(O)=O)CC1 HNNQYHFROJDYHQ-UHFFFAOYSA-N 0.000 description 1
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- 229910002544 Fe-Cr Inorganic materials 0.000 description 1
- 229910017116 Fe—Mo Inorganic materials 0.000 description 1
- PXGOKWXKJXAPGV-UHFFFAOYSA-N Fluorine Chemical compound FF PXGOKWXKJXAPGV-UHFFFAOYSA-N 0.000 description 1
- 229910002609 Gd2Zr2O7 Inorganic materials 0.000 description 1
- 229910001030 Iron–nickel alloy Inorganic materials 0.000 description 1
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- 229910001080 W alloy Inorganic materials 0.000 description 1
- OBETXYAYXDNJHR-UHFFFAOYSA-N alpha-ethylcaproic acid Natural products CCCCC(CC)C(O)=O OBETXYAYXDNJHR-UHFFFAOYSA-N 0.000 description 1
- 229910000963 austenitic stainless steel Inorganic materials 0.000 description 1
- 150000001732 carboxylic acid derivatives Chemical class 0.000 description 1
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 description 1
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 description 1
- UPHIPHFJVNKLMR-UHFFFAOYSA-N chromium iron Chemical compound [Cr].[Fe] UPHIPHFJVNKLMR-UHFFFAOYSA-N 0.000 description 1
- KLKMXKACEROVRH-UHFFFAOYSA-L copper;3,5,5-trimethylhexanoate Chemical compound [Cu+2].[O-]C(=O)CC(C)CC(C)(C)C.[O-]C(=O)CC(C)CC(C)(C)C KLKMXKACEROVRH-UHFFFAOYSA-L 0.000 description 1
- CLUOTFHJTGLPSG-UHFFFAOYSA-L copper;7,7-dimethyloctanoate Chemical compound [Cu+2].CC(C)(C)CCCCCC([O-])=O.CC(C)(C)CCCCCC([O-])=O CLUOTFHJTGLPSG-UHFFFAOYSA-L 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
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- VFRSADQPWYCXDG-LEUCUCNGSA-N ethyl (2s,5s)-5-methylpyrrolidine-2-carboxylate;2,2,2-trifluoroacetic acid Chemical compound OC(=O)C(F)(F)F.CCOC(=O)[C@@H]1CC[C@H](C)N1 VFRSADQPWYCXDG-LEUCUCNGSA-N 0.000 description 1
- FPIQZBQZKBKLEI-UHFFFAOYSA-N ethyl 1-[[2-chloroethyl(nitroso)carbamoyl]amino]cyclohexane-1-carboxylate Chemical compound ClCCN(N=O)C(=O)NC1(C(=O)OCC)CCCCC1 FPIQZBQZKBKLEI-UHFFFAOYSA-N 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- VBJZVLUMGGDVMO-UHFFFAOYSA-N hafnium atom Chemical compound [Hf] VBJZVLUMGGDVMO-UHFFFAOYSA-N 0.000 description 1
- 230000020169 heat generation Effects 0.000 description 1
- 125000000468 ketone group Chemical group 0.000 description 1
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- 239000000155 melt Substances 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 125000005609 naphthenate group Chemical group 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- NFHFRUOZVGFOOS-UHFFFAOYSA-N palladium;triphenylphosphane Chemical compound [Pd].C1=CC=CC=C1P(C=1C=CC=CC=1)C1=CC=CC=C1.C1=CC=CC=C1P(C=1C=CC=CC=1)C1=CC=CC=C1.C1=CC=CC=C1P(C=1C=CC=CC=1)C1=CC=CC=C1.C1=CC=CC=C1P(C=1C=CC=CC=1)C1=CC=CC=C1 NFHFRUOZVGFOOS-UHFFFAOYSA-N 0.000 description 1
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B12/00—Superconductive or hyperconductive conductors, cables, or transmission lines
- H01B12/02—Superconductive or hyperconductive conductors, cables, or transmission lines characterised by their form
- H01B12/06—Films or wires on bases or cores
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/60—Superconducting electric elements or equipment; Power systems integrating superconducting elements or equipment
Landscapes
- Superconductors And Manufacturing Methods Therefor (AREA)
- Inorganic Compounds Of Heavy Metals (AREA)
Description
本発明は、超電導体およびその製造方法に関する。 The present invention relates to a superconductor and a method for manufacturing the same.
酸化物超電導体は、その臨界温度（Ｔｃ）が液体窒素温度を超えることから超電導マグネット、超電導ケーブル、電力機器及びデバイス等への応用が期待されており、多くの研究結果が報告されている。 Oxide superconductors have a critical temperature (T c ) that exceeds the temperature of liquid nitrogen, and are therefore expected to be useful in superconducting magnets, superconducting cables, electric power equipment and devices, and many research results have been reported.
酸化物超電導体を上記の分野に適用するためには、臨界電流密度（Ｊｃ）が高く、かつ高い臨界電流（Ｉｃ）値を有する長尺の線材を製造する必要がある。そして、このような線材は、通常、金属テープ等からなる基板上に酸化物超電導層が配置された構造を有する。 In order to apply oxide superconductors to the above fields, it is necessary to manufacture long wires having high critical current density ( Jc ) and high critical current ( Ic ) values. Such wires usually have a structure in which an oxide superconducting layer is disposed on a substrate made of a metal tape or the like.
ここで、ＲｅＢａ２Ｃｕ３Ｏｘ系超電導体（Ｒｅは、Ｙ、Ｎｄ、Ｓｍ、Ｇｄ、Ｄｙ、Ｅｕ、Ｅｒ、Ｙｂ、Ｐｒ、およびＨｏからなる群から選択される少なくとも１種の元素を表し、ｘは６．２～７．０を表す）は、従来の超電導体であるＮｂ３ＳｎやＮｂ３Ａｌ等と比較して臨界電流密度が高い。したがって、種々の製品への適用が期待されている。 Here, the ReBa 2 Cu 3 O x superconductor (Re represents at least one element selected from the group consisting of Y, Nd, Sm, Gd, Dy, Eu, Er, Yb, Pr, and Ho, and x represents 6.2 to 7.0) has a higher critical current density than conventional superconductors such as Nb 3 Sn and Nb 3 Al. Therefore, it is expected to be applied to various products.
当該ＲｅＢａ２Ｃｕ３Ｏｘ系超電導体の製造方法として、金属有機酸塩堆積法（Ｍｅｔａｌ Ｏｒｇａｎｉｃ Ｄｅｐｏｓｉｔｉｏｎ Ｐｒｏｃｅｓｓｅｓ、以下「ＭＯＤ法」とも称する）が知られている。ＭＯＤ法は、金属有機酸塩を基板上に塗布し、これを熱分解させて薄膜を形成する方法である。ＭＯＤ法は非真空で行うことができ、かつ低コストで高速成膜が可能であるという利点がある。また、当該方法で、ＲｅＢａ２Ｃｕ３Ｏｘ系超電導体を製造すると、他の方法で製造した場合と比較して臨界電流密度が高くなる。 Metal organic deposition processes (hereinafter also referred to as the "MOD process") are known as a method for producing the ReBa 2 Cu 3 O x superconductor. The MOD process is a method for forming a thin film by applying a metal organic acid salt onto a substrate and thermally decomposing it. The MOD process has the advantage that it can be performed in a non-vacuum environment and can form a film at a low cost and at a high speed. In addition, when a ReBa 2 Cu 3 O x superconductor is produced by this process, the critical current density is higher than when it is produced by other methods.
ここで、上記ＭＯＤ法の中でも、フッ素を含む有機酸塩（例えば、トリフルオロ酢酸塩（以下、「ＴＦＡ塩」とも称する）を使用する方法が近年注目されている。例えば、以下のような方法が提案されている。まず、ＹのＴＦＡ塩、ＢａのＴＦＡ塩、およびＣｕのナフテン酸塩を含む溶液（溶液中の金属元素のモル比Ｙ：Ｂａ：Ｃｕ＝１：２：３）を基板上に塗布し、仮焼成してアモルファスの超電導前駆体層を形成する。そして、当該超電導前駆体層を一定時間加熱して本焼成する。当該方法では本焼成の際、超電導前駆体層と雰囲気中の水蒸気とが反応し、基板と超電導前駆体層との界面に液相が生じる。そして、当該液相に超電導前駆体層中の各金属材料が溶融し、基板側からＲｅＢａ２Ｃｕ３Ｏｘ系化合物がエピタキシャル成長する。 Among the above-mentioned MOD methods, a method using an organic acid salt containing fluorine (for example, a trifluoroacetate salt (hereinafter also referred to as a "TFA salt") has been attracting attention in recent years. For example, the following method has been proposed. First, a solution containing a TFA salt of Y, a TFA salt of Ba, and a naphthenate salt of Cu (molar ratio of metal elements in the solution: Y:Ba:Cu=1:2:3) is applied onto a substrate and pre-baked to form an amorphous superconducting precursor layer. Then, the superconducting precursor layer is heated for a certain period of time for main baking. In this method, during main baking, the superconducting precursor layer reacts with water vapor in the atmosphere, and a liquid phase is generated at the interface between the substrate and the superconducting precursor layer. Then, each metal material in the superconducting precursor layer melts in the liquid phase, and a ReBa 2 Cu 3 O x compound grows epitaxially from the substrate side.
ただし、上記方法では、本焼成時に異相（Ｂａ化合物）や空孔等が生じやすく、それに伴い超電導層の配向性および結晶粒界における電気的結合性も低下する。そのため、臨界電流密度の向上が困難であった。However, with the above method, foreign phases (Ba compounds) and vacancies are likely to occur during the firing process, which reduces the orientation of the superconducting layer and the electrical connection at the grain boundaries. This makes it difficult to improve the critical current density.
このような課題に対し、ＴＦＡ塩を用いたＭＯＤ法において、基板上に塗布する溶液中の金属元素のモル比Ｒｅ：Ｂａ：Ｃｕを１：ｎ：３（ｎ＜２）とすることが提案されている（特許文献１）。当該方法によれば、超電導層中の結晶粒界に異相（Ｂａ化合物）が生じ難くなり、結晶粒界における電気的結合性が良好になる。To address these issues, it has been proposed to set the molar ratio of metal elements Re:Ba:Cu in the solution applied to the substrate to 1:n:3 (n<2) in the MOD method using TFA salt (Patent Document 1). This method makes it difficult for a different phase (Ba compound) to form at the grain boundaries in the superconducting layer, improving the electrical connection at the grain boundaries.
一方、微細な磁束ピンニング点を導入するために、ＴＦＡ塩を用いたＭＯＤ法において、厚みの薄い超電導前駆体層を複数積層してから、本焼成を行う方法も提案されている（特許文献２）。On the other hand, in order to introduce fine magnetic flux pinning points, a method has been proposed in which multiple thin superconducting precursor layers are stacked and then sintered in a MOD method using TFA salt (Patent Document 2).
しかしながら、上記特許文献１の技術では、異相（Ｂａ化合物）の抑制が可能であるものの、本焼成時のクラックを十分に抑制することが難しい。一方、特許文献２の方法では、異相（Ｂａ化合物）の発生の抑制が難しい。However, while the technology of Patent Document 1 makes it possible to suppress the formation of heterogeneous phases (Ba compounds), it is difficult to sufficiently suppress cracks during firing. On the other hand, the method of Patent Document 2 makes it difficult to suppress the formation of heterogeneous phases (Ba compounds).
そこで、基板上に金属元素のモル比Ｒｅ：Ｂａ：Ｃｕが１：ｎ：３（ｎ＜２）である溶液を薄く塗布し、厚みの薄い超電導前駆体層を複数積層してから本焼成することが考えられる。しかしながら、本発明者らが鋭意検討したところ、当該方法でＲｅＢａ２Ｃｕ３Ｏｘ系化合物を含む超電導層を形成すると、その表面抵抗が大きくなることが明らかとなった。 Therefore, it is conceivable to thinly coat a solution having a molar ratio of metal elements Re:Ba:Cu of 1:n:3 (n<2) on a substrate, stack a plurality of thin superconducting precursor layers, and then perform main firing. However, the inventors of the present invention have made extensive studies and found that when a superconducting layer containing a ReBa 2 Cu 3 O x compound is formed by this method, its surface resistance increases.
その理由は、以下のように考えられる。超電導前駆体層形成の際に、厚みの薄い膜を複数層積層してから積層体を本焼成すると、空孔や異相の少ない超電導層が形成される。ただし、超電導前駆体層が含むＢａの量が化学量論値より少ないため、最終的にはＢａが不足し、ＲｅおよびＣｕが余剰となる。その結果、表面にＹ２Ｃｕ３Ｏ５やＣｕＯ、Ｙ２Ｏ３等を含む異物層が生じる。そして、当該異物層が、超電導層の表面抵抗を高める要因になると考えられる。 The reason for this is considered to be as follows. When forming a superconducting precursor layer, if a plurality of thin films are laminated and then the laminate is sintered, a superconducting layer with few voids and heterogeneous phases is formed. However, since the amount of Ba contained in the superconducting precursor layer is less than the stoichiometric value, Ba is ultimately insufficient and Re and Cu are in excess . As a result, a foreign matter layer containing Y2Cu3O5 , CuO, Y2O3 , etc. is generated on the surface. It is considered that the foreign matter layer is a factor that increases the surface resistance of the superconducting layer.
以上のように、従来の技術では、臨界電流密度が高く、かつ表面抵抗が十分に低い超電導体は十分に得られていない、というのが実状であった。そこで、本発明は、臨界電流密度が高く、かつ表面抵抗が十分に低い超電導体、および当該超電導体を複雑な工程等を経ることなく製造可能な方法の提供を目的とする。As described above, the reality is that conventional technology has not been able to provide a sufficient number of superconductors with high critical current density and sufficiently low surface resistance. Therefore, the present invention aims to provide a superconductor with high critical current density and sufficiently low surface resistance, and a method for manufacturing such a superconductor without going through complicated processes, etc.
即ち、本発明は、以下の超電導体を提供する。
基板と、前記基板上に配置された、ＲｅＢａ２Ｃｕ３Ｏｘ系化合物（Ｒｅは、Ｙ、Ｎｄ、Ｓｍ、Ｇｄ、Ｄｙ、Ｅｕ、Ｅｒ、Ｙｂ、Ｐｒ、およびＨｏからなる群から選択される、少なくとも１種の元素を表し、ｘは６．２～７．０を表す）を含む超電導層と、を有し、前記超電導層の７７Ｋにおける表面抵抗が１ｋΩ以下であり、前記超電導層の７７Ｋ、自己磁場中での臨界電流密度が３．０ＭＡ／ｃｍ２以上である、超電導体。
That is, the present invention provides the following superconductor.
A superconductor comprising: a substrate; and a superconducting layer disposed on the substrate, the superconducting layer containing a ReBa2Cu3Ox compound (Re represents at least one element selected from the group consisting of Y, Nd, Sm, Gd, Dy, Eu, Er, Yb, Pr, and Ho, and x represents 6.2 to 7.0), wherein the surface resistance of the superconducting layer at 77K is 1 kΩ or less, and the critical current density of the superconducting layer at 77K in a self-magnetic field is 3.0 MA/ cm2 or more.
本発明は、以下の超電導体の製造方法も提供する。
基板を準備する工程と、前記基板上に、Ｒｅ（Ｒｅは、Ｙ、Ｎｄ、Ｓｍ、Ｇｄ、Ｄｙ、Ｅｕ、Ｅｒ、Ｙｂ、ＰｒおよびＨｏからなる群から選択される少なくとも１種の元素を表す）、Ｂａ、およびＣｕを少なくとも含み、金属元素のモル比Ｒｅ：Ｂａ：Ｃｕ：Ｍが１．０：１．４～２．２：３．０～３．２：０～０．３である（Ｍは、Ｚｒ、Ｈｆ、Ｉｒ、Ｓｎ、Ｃｅ、Ｔｉ、およびＮｂからなる群から選択される少なくとも１種の元素を表し、Ｍのモル比が０であるとき、Ｂａのモル比は２．０未満である）第１溶液を塗布し、焼成後の厚みが１５０ｎｍ以下となるように塗膜を形成して、前記第１溶液の塗膜を仮焼成するステップを繰り返し行って、超電導前駆体層を形成する工程と、前記超電導前駆体層上に、Ｃｕ元素を含まず、かつ金属元素のモル比Ｒｅ：Ｂａ：Ｍが０～１．１：０．０５～５５：０～７である第２溶液を塗布し、前記第２溶液の塗膜を仮焼成するステップを繰り返し行って、Ｂａ含有層を形成する工程と、前記超電導前駆体層および前記Ｂａ含有層を本焼成し、超電導層を形成する工程と、を含む、超電導体の製造方法。
The present invention also provides the following method for producing a superconductor.
The method includes the steps of preparing a substrate, and applying a first solution containing at least Re (Re represents at least one element selected from the group consisting of Y, Nd, Sm, Gd, Dy, Eu, Er, Yb, Pr, and Ho), Ba, and Cu, and a molar ratio of metal elements Re:Ba:Cu:M is 1.0:1.4-2.2:3.0-3.2:0-0.3 (M represents at least one element selected from the group consisting of Zr, Hf, Ir, Sn, Ce, Ti, and Nb, and when the molar ratio of M is 0, the molar ratio of Ba is less than 2.0) onto the substrate. and forming a Ba-containing layer by repeatedly performing a step of applying a second solution, which does not contain Cu and has a molar ratio of metal elements Re:Ba:M of 0-1.1:0.05-55:0-7, onto the superconducting precursor layer and temporarily firing the coating of the second solution, and forming a Ba-containing layer by repeatedly performing a step of applying a second solution, which does not contain Cu and has a molar ratio of metal elements Re:Ba:M of 0-1.1:0.05-55:0-7 onto the superconducting precursor layer and temporarily firing the coating of the second solution.
本発明の超電導体は、高い臨界電流密度と低い表面抵抗とを兼ね備える。さらに本発明の超電導体の製造方法によれば、複雑な工程等を経ることなく簡便な方法で超電導体を作製可能である。The superconductor of the present invention has both a high critical current density and low surface resistance. Furthermore, according to the manufacturing method of the superconductor of the present invention, it is possible to manufacture the superconductor in a simple manner without going through complicated processes.
本明細書において、「～」で示す数値範囲は、「～」の前後に記載された数値を含む数値範囲を意味する。In this specification, a numerical range indicated by "~" means a numerical range including the numbers written before and after "~".
１.超電導体
本発明の超電導体の構成や物性について説明し、その後、当該超電導体の製造方法について説明する。
1. Superconductor The configuration and physical properties of the superconductor of the present invention will be explained, and then the method for producing the superconductor will be explained.
本発明の超電導体は、基板と、当該基板上に配置された、ＲｅＢａ２Ｃｕ３Ｏｘ系化合物を含む超電導層と、を有する。 The superconductor of the present invention has a substrate and a superconducting layer containing a ReBa 2 Cu 3 O x based compound disposed on the substrate.
上記基板は、ＲｅＢａ２Ｃｕ３Ｏｘ系化合物をエピタキシャル成長させることが可能なものであれば特に制限されない。基板の形状は、超電導体の用途に応じて適宜選択される。例えば平板状であってもよいが、超電導体を線材とする場合にはテープ状等の長尺状とする。 The substrate is not particularly limited as long as it is capable of epitaxially growing a ReBa 2 Cu 3 O x compound. The shape of the substrate is appropriately selected depending on the application of the superconductor. For example, the substrate may be flat, but when the superconductor is to be a wire, the substrate is long, such as a tape.
また、基板は、単層構造であってもよいが、低磁性かつ耐熱性および強度が高い支持体と、当該支持体上に配置された、２軸配向性を有する中間層と、を含むことが好ましい。The substrate may have a single-layer structure, but preferably includes a support having low magnetic properties, high heat resistance and high strength, and an intermediate layer having biaxial orientation disposed on the support.
支持体は、２軸配向性を有していてもよく、配向性を有していなくてもよい。支持体の材料の例には、ニッケル（Ｎｉ）や、ニッケル合金、タングステン合金、ステンレス鋼、銀（Ａｇ）等が含まれる。より具体的には、Ｎｉ－Ｃｒ－Ｆｅ－Ｍｏ系のハステロイ（登録商標）Ｂ、Ｃ、Ｘ等のＮｉ－Ｃｒ系合金；Ｗ－Ｍｏ系合金；オーステナイト系ステンレス鋼等のＦｅ－Ｃｒ系合金；非磁性のＦｅ－Ｎｉ系合金；等が含まれる。支持体はその強度の観点からビッカース硬度（Ｈｖ）が１５０以上であることが好ましい。また、基材の厚みは、通常１００μｍ以下が好ましい。The support may have biaxial orientation or may not have orientation. Examples of materials for the support include nickel (Ni), nickel alloys, tungsten alloys, stainless steel, silver (Ag), etc. More specifically, Ni-Cr-Fe-Mo-based alloys such as Hastelloy (registered trademark) B, C, and X; W-Mo-based alloys; Fe-Cr-based alloys such as austenitic stainless steel; non-magnetic Fe-Ni-based alloys; etc. From the viewpoint of strength, it is preferable that the support has a Vickers hardness (Hv) of 150 or more. In addition, the thickness of the substrate is usually preferably 100 μm or less.
一方、中間層は、基板に２軸配向性を付与することが可能であれば単層で構成されてもよく、複数層から構成されてもよいが、支持体側から超電導層側への元素の拡散を抑制するための拡散防止層や、配向性を付与するための配向層等、複数の層を有する中間層がより好ましい。On the other hand, the intermediate layer may be composed of a single layer or multiple layers as long as it is possible to impart biaxial orientation to the substrate, but an intermediate layer having multiple layers, such as a diffusion prevention layer for suppressing the diffusion of elements from the support side to the superconducting layer side and an orientation layer for imparting orientation, is more preferable.
複数層からなる中間層の一例として、Ｇｄ２ＺｒＯ７層（第１中間層）／Ｙ２Ｏ３層（第２中間層）／ＭｇＯ層（第３中間層）／ＬａＭｎＯ３層（第４中間層）／ＣｅＯ２層（第５中間層）をこの順に積層した積層体等が挙げられる。当該中間層は、第１中間層側が上記支持体側に配置される。上記中間層の総厚みは、通常１．５μｍ未満が好ましい。 An example of an intermediate layer made of multiple layers is a laminate in which 7 layers of Gd 2 ZrO (first intermediate layer), 3 layers of Y 2 O (second intermediate layer), 3 layers of MgO (third intermediate layer), 3 layers of LaMnO (fourth intermediate layer), and 2 layers of CeO (fifth intermediate layer) are laminated in this order. The intermediate layer is arranged with the first intermediate layer side facing the support. The total thickness of the intermediate layer is usually preferably less than 1.5 μm.
一方、超電導層は、ＲｅＢａ２Ｃｕ３Ｏｘ系化合物（Ｒｅは、Ｙ、Ｎｄ、Ｓｍ、Ｇｄ、Ｄｙ、Ｅｕ、Ｅｒ、Ｙｂ、Ｐｒ、およびＨｏからなる群から選択される、少なくとも１種の元素を表し、ｘは６．２～７．０を表す）を含んでいればよい。ここで、Ｒｅは、上記のいずれの元素であってもよいが、好ましくはＹ、Ｇｄ、もしくはＹおよびＧｄの併用であり、特に好ましくはＹ、もしくはＹおよびＧｄの併用である。また、超電導層中のＲｅＢａ２Ｃｕ３Ｏｘ系化合物の量は、７０体積％以上が好ましく、８０～１００体積％がより好ましい。 On the other hand, the superconducting layer may contain a ReBa 2 Cu 3 O x compound (Re represents at least one element selected from the group consisting of Y, Nd, Sm, Gd, Dy, Eu, Er, Yb, Pr, and Ho, and x represents 6.2 to 7.0). Here, Re may be any of the above elements, but is preferably Y, Gd, or a combination of Y and Gd, and particularly preferably Y, or a combination of Y and Gd. The amount of the ReBa 2 Cu 3 O x compound in the superconducting layer is preferably 70% by volume or more, and more preferably 80 to 100% by volume.
一方、超電導層は、ＢａおよびＭ（Ｍは、Ｚｒ、Ｈｆ、Ｉｒ、Ｓｎ、Ｃｅ、Ｔｉ、およびＮｂからなる群から選択される、少なくとも１種の元素）を含む酸化物粒子をさらに含んでいてもよい。Ｍは、上記のいずれの元素であってもよいが、好ましくはＺｒ、Ｈｆであり、特に好ましくはＨｆである。酸化物粒子の量は２０体積％以下が好ましく、３体積％～１０体積％がより好ましい。超電導層中において、ＢａおよびＭを含む酸化物粒子は、超電導層の量子化磁束の移動を抑制するための磁束ピンニング点として機能する。ＢａおよびＭを含む酸化物粒子の平均粒子径は、３０ｎｍ以下が好ましく、５～１５ｎｍがより好ましい。酸化物粒子の平均粒子径が当該範囲であると、高い超電導特性が得られやすくなる。On the other hand, the superconducting layer may further contain oxide particles containing Ba and M (M is at least one element selected from the group consisting of Zr, Hf, Ir, Sn, Ce, Ti, and Nb). M may be any of the above elements, but is preferably Zr or Hf, and particularly preferably Hf. The amount of oxide particles is preferably 20 vol.% or less, and more preferably 3 vol.% to 10 vol.%. In the superconducting layer, the oxide particles containing Ba and M function as flux pinning points to suppress the movement of quantized magnetic flux in the superconducting layer. The average particle diameter of the oxide particles containing Ba and M is preferably 30 nm or less, and more preferably 5 to 15 nm. When the average particle diameter of the oxide particles is within this range, high superconducting properties are easily obtained.
ここで、超電導層中の金属元素のモル比Ｒｅ：Ｂａ：Ｃｕ：Ｍは、１．０～１．２：１．８～２．５：３．０～３．１：０～０．４が好ましく、１．０～１．１：２．０～２．２：３．０～３．１：０．１０～０．２０がより好ましい。超電導層中の金属元素のモル比が当該範囲であると、臨界電流密度が良好になりやすい。Here, the molar ratio of the metal elements in the superconducting layer, Re:Ba:Cu:M, is preferably 1.0-1.2:1.8-2.5:3.0-3.1:0-0.4, and more preferably 1.0-1.1:2.0-2.2:3.0-3.1:0.10-0.20. When the molar ratio of the metal elements in the superconducting layer is within this range, the critical current density tends to be good.
また、超電導層の厚みは、０．５～５．０μｍが好ましく、１．０～２．０μｍがより好ましい。超電導層の厚みが当該範囲であると、各種用途に適用しやすくなる。The thickness of the superconducting layer is preferably 0.5 to 5.0 μm, and more preferably 1.0 to 2.0 μm. When the thickness of the superconducting layer is within this range, it is easy to apply to various applications.
ここで、本発明の超電導体では、超電導層の表面抵抗が１ｋΩ以下である。表面抵抗は、３００Ω以下がより好ましく、１００Ω以下がさらに好ましく、８４Ω以下がさらに好ましい。本明細書における表面抵抗は、超電導体を複数の領域に区分し、各領域における１０ｍｍ間の表面抵抗をテスターで測定したときの平均値とする。超電導層の表面抵抗が１ｋΩ以下であると、電流の流し込みが容易になり、超電導体層の発熱や焼損を抑制できる。後述の製造方法で超電導体を製造すると、表面抵抗が１ｋΩ以下になる。Here, in the superconductor of the present invention, the surface resistance of the superconducting layer is 1 kΩ or less. The surface resistance is more preferably 300Ω or less, even more preferably 100Ω or less, and even more preferably 84Ω or less. In this specification, the surface resistance is the average value when the superconductor is divided into multiple regions and the surface resistance of each region is measured over a 10 mm area using a tester. If the surface resistance of the superconducting layer is 1 kΩ or less, it becomes easy to pass the current therethrough, and heat generation and burning of the superconductor layer can be suppressed. When the superconductor is manufactured using the manufacturing method described below, the surface resistance becomes 1 kΩ or less.
また、上記超電導層の７７Ｋ、自己磁場中での臨界電流密度は、３．０ＭＡ／ｃｍ２以上であり、５．６ＭＡ／ｃｍ２以上が好ましい。上記臨界電流密度は、４端子法等で測定される臨界電流値を超電導層の電流通過断面積で割った値である。後述の製造方法で超電導体を製造すると、臨界電流密度が３．０ＭＡ／ｃｍ２以上になる。 The critical current density of the superconducting layer at 77K in a self-magnetic field is 3.0 MA/ cm2 or more, and preferably 5.6 MA/ cm2 or more. The critical current density is a value obtained by dividing the critical current value measured by a four-terminal method or the like by the current passing cross-sectional area of the superconducting layer. When a superconductor is manufactured by the manufacturing method described below, the critical current density becomes 3.0 MA/ cm2 or more.
また、当該超電導体の基板と超電導層との積層面に垂直な断面において、超電導層が含む空孔の面積は、超電導層の面積に対して３％以下が好ましい。上記断面は、基板と前記超電導層との積層面に垂直であれば、どの位置における断面であってもよい。当該空孔の面積が小さいと、通電時の電流経路が阻害され難く、上記臨界電流密度が得られやすい。空孔の面積の割合は、２％以下がより好ましく、１％未満がさらに好ましい。空孔の面積の割合は、後述の超電導体の製造方法における第１溶液塗布工程および第１仮焼成工程で１回に形成する超電導前駆体層の厚みを薄くすることで少なくできる。In addition, in a cross section perpendicular to the lamination plane of the substrate and the superconducting layer of the superconductor, the area of the voids contained in the superconducting layer is preferably 3% or less of the area of the superconducting layer. The cross section may be at any position as long as it is perpendicular to the lamination plane of the substrate and the superconducting layer. If the area of the voids is small, the current path is less likely to be obstructed when current is passed through, and the critical current density is more likely to be obtained. The proportion of the area of the voids is more preferably 2% or less, and even more preferably less than 1%. The proportion of the area of the voids can be reduced by reducing the thickness of the superconducting precursor layer formed in one step in the first solution application step and the first pre-baking step in the manufacturing method for a superconductor described later.
ここで、本発明の超電導体は、上記超電導層上に、安定化層等をさらに有していてもよい。安定化層は、例えば、銅、銀、金や白金、あるいはこれらの積層膜や合金等を含む、抵抗の低い層である。当該安定化層の厚みは、数μｍ以上とすることができる。Here, the superconductor of the present invention may further have a stabilization layer or the like on the superconducting layer. The stabilization layer is a low-resistance layer that contains, for example, copper, silver, gold, platinum, or a laminated film or alloy thereof. The thickness of the stabilization layer can be several μm or more.
本発明の超電導体の用途は特に制限されないが、例えば線材とすることができ、当該線材は、超電導マグネット、超電導ケーブル、電力機器及びデバイス等に適用可能である。The use of the superconductor of the present invention is not particularly limited, but it can be, for example, made into a wire, which can be applied to superconducting magnets, superconducting cables, electric power equipment and devices, etc.
２．超電導体の製造方法
上述の物性を有する超電導体の製造方法について説明する。ただし、上述の超電導体の製造方法は、以下の方法に制限されない。
2. Method for Producing Superconductor A method for producing a superconductor having the above-mentioned physical properties will be described below, although the method for producing the above-mentioned superconductor is not limited to the following method.
本発明の超電導体の製造方法の工程を図１に示す。本発明の超電導体の製造方法では、まず、基板１を準備する（基板準備工程、図１Ａ）。そして当該基板１上に、所定のモル比でＲｅ（Ｒｅは、Ｙ、Ｎｄ、Ｓｍ、Ｇｄ、Ｄｙ、Ｅｕ、Ｅｒ、Ｙｂ、ＰｒおよびＨｏからなる群から選択される少なくとも１種の元素を表す）、Ｂａ、およびＣｕを含む第１溶液を塗布し、焼成後の厚み（超電導層換算厚み）が１５０ｎｍ以下である塗膜を形成する（第１溶液塗布工程）。そして、当該第１溶液の塗膜を仮焼成し（第１仮焼成工程）、超電導前駆体層２ａを形成する（図１Ｂ）。当該第１溶液塗布工程および第１仮焼成工程は、繰り返し行うことが好ましく、複数の超電導前駆体層２ａ、２ｂ、２ｃを積層することが好ましい（図１Ｃ）。 The steps of the method for producing a superconductor of the present invention are shown in FIG. 1. In the method for producing a superconductor of the present invention, first, a substrate 1 is prepared (substrate preparation step, FIG. 1A). Then, a first solution containing Re (Re represents at least one element selected from the group consisting of Y, Nd, Sm, Gd, Dy, Eu, Er, Yb, Pr and Ho), Ba and Cu in a predetermined molar ratio is applied onto the substrate 1 to form a coating film having a thickness after firing (superconducting layer equivalent thickness) of 150 nm or less (first solution application step). Then, the coating film of the first solution is pre-fired (first pre-fire step) to form a superconducting precursor layer 2a (FIG. 1B). The first solution application step and the first pre-fire step are preferably performed repeatedly, and a plurality of superconducting precursor layers 2a, 2b and 2c are preferably stacked (FIG. 1C).
上記の方法によって、所望の厚みの超電導前駆体層２を形成した後、当該超電導前駆体層２上に、Ｃｕ元素を含まず、かつ金属元素のモル比Ｒｅ：Ｂａ：Ｍが０～１．１：０．０５～５５：０～７である第２溶液を塗布する（第２溶液塗布工程）。そして、第２溶液の塗膜を仮焼成し（第２仮焼成工程）、Ｂａ含有層３を形成する（図１Ｄ）。第２溶液塗布工程および第２仮焼成工程は、必要に応じて繰り返し行ってもよい。その後、超電導前駆体層２およびＢａ含有層３を本焼成し、超電導層４を形成する（本焼成工程、図１Ｅ）。なお、超電導前駆体層２およびＢａ含有層３を本焼成する前に、中間熱処理工程を含めてもよい。After forming the superconducting precursor layer 2 of the desired thickness by the above method, a second solution that does not contain Cu elements and has a molar ratio of metal elements Re:Ba:M of 0-1.1:0.05-55:0-7 is applied onto the superconducting precursor layer 2 (second solution application step). Then, the coating of the second solution is pre-fired (second pre-fire step) to form a Ba-containing layer 3 (Figure 1D). The second solution application step and the second pre-fire step may be repeated as necessary. Thereafter, the superconducting precursor layer 2 and the Ba-containing layer 3 are fired to form a superconducting layer 4 (firing step, Figure 1E). Note that an intermediate heat treatment step may be included before firing the superconducting precursor layer 2 and the Ba-containing layer 3.
本発明の製造方法では、第１溶液塗布工程において、Ｂａの量が化学量論値より少ない第１溶液を塗布して、超電導前駆体層を形成する。このような超電導前駆体層をそのまま本焼成すると、基板から離れた表面側でＢａが不足し、異物が発生する。そこで、本発明の製造方法では、超電導前駆体層上にＢａを含み、かつＣｕを実質的に含まないＢａ含有層を形成する。そして、超電導前駆体層およびＢａ含有層を本焼成すると、Ｂａが不足して生じた異物とＢａ含有層とが固相反応する。その結果、得られる超電導層の組成が、基板側から表面側まで略均一になり、得られる超電導体の表面抵抗が小さくなり、さらには臨界電流密度が高くなる。In the manufacturing method of the present invention, in the first solution application step, a first solution containing less Ba than the stoichiometric value is applied to form a superconducting precursor layer. If such a superconducting precursor layer is sintered as is, Ba will be insufficient on the surface side away from the substrate, and foreign matter will be generated. Therefore, in the manufacturing method of the present invention, a Ba-containing layer that contains Ba and does not substantially contain Cu is formed on the superconducting precursor layer. Then, when the superconducting precursor layer and the Ba-containing layer are sintered, the foreign matter generated due to the deficiency of Ba will react with the Ba-containing layer in a solid phase. As a result, the composition of the obtained superconducting layer becomes approximately uniform from the substrate side to the surface side, the surface resistance of the obtained superconductor will be reduced, and the critical current density will be increased.
以下、本発明の超電導体の製造方法が含む各工程について、詳しく説明する。Below, each step in the manufacturing method for the superconductor of the present invention is described in detail.
（基板準備工程）
本工程では、超電導層を形成するための基板を準備する。基板は、ＲｅＢａ２Ｃｕ３Ｏｘ系化合物をエピタキシャル成長させることが可能であれば特に制限されず、平板状であってもよく長尺状であってもよい。当該基板は、上述の超電導体の基板として説明したものと同様である。
(Substrate preparation process)
In this step, a substrate for forming a superconducting layer is prepared. The substrate is not particularly limited as long as it is possible to epitaxially grow a ReBa 2 Cu 3 O x compound, and may be flat or elongated. The substrate is the same as that described above as the substrate for the superconductor.
（第１溶液塗布工程）
本工程では、上述の基板上に、Ｒｅ、Ｂａ、およびＣｕを少なくとも含み、かつ金属元素のモル比Ｒｅ：Ｂａ：Ｃｕ：Ｍが１．０：１．４～２．２：３．０～３．２：０～０．３である（Ｍは、Ｚｒ、Ｈｆ、Ｉｒ、Ｓｎ、Ｃｅ、Ｔｉ、およびＮｂからなる群から選択される少なくとも１種の元素を表し、Ｍのモル比が０であるとき、Ｂａのモル比は２．０未満である）第１溶液を塗布し、焼成後の厚み（超電導層換算厚み）が１５０ｎｍ以下である塗膜を形成する。
(First solution application step)
In this process, a first solution containing at least Re, Ba, and Cu and having a molar ratio of metal elements Re:Ba:Cu:M of 1.0:1.4-2.2:3.0-3.2:0-0.3 (M represents at least one element selected from the group consisting of Zr, Hf, Ir, Sn, Ce, Ti, and Nb, and when the molar ratio of M is 0, the molar ratio of Ba is less than 2.0) is applied onto the above-mentioned substrate to form a coating film having a thickness after firing (superconducting layer equivalent thickness) of 150 nm or less.
本工程で塗布する第１溶液は、Ｒｅ源、Ｂａ源、およびＣｕ源を必須として含んでいればよく、必要に応じてＭ源や、溶媒を含んでいてもよい。第１溶液がＭ源を含むと、得られる超電導層中に、上述のＢａおよびＭを含む酸化物粒子（磁束ピンニング点）が形成される。The first solution applied in this process must contain a Re source, a Ba source, and a Cu source as essential components, and may contain an M source and a solvent as necessary. When the first solution contains an M source, oxide particles (flux pinning points) containing the above-mentioned Ba and M are formed in the resulting superconducting layer.
第１溶液が含むＲｅ源は、Ｒｅ（Ｙ、Ｎｄ、Ｓｍ、Ｇｄ、Ｄｙ、Ｅｕ、Ｅｒ、Ｙｂ、ＰｒまたはＨｏ）を含む化合物（例えば有機酸塩）であれば特に制限されないが、反応性等の観点で、ケトン基を含まない、炭素数３～８のカルボン酸のＲｅ塩が好ましい。その具体例には、プロピオン酸イットリウム（Ｙ）や、プロピオン酸ガドリウム（Ｇｄ）等が含まれる。第１溶液は、Ｒｅ源を１種のみ含んでいてもよく、２種以上含んでいてもよい。The Re source contained in the first solution is not particularly limited as long as it is a compound (e.g., an organic acid salt) containing Re (Y, Nd, Sm, Gd, Dy, Eu, Er, Yb, Pr, or Ho), but from the viewpoint of reactivity, etc., a Re salt of a carboxylic acid having 3 to 8 carbon atoms and not containing a ketone group is preferable. Specific examples include yttrium propionate (Y) and gadolinium propionate (Gd). The first solution may contain only one type of Re source, or may contain two or more types.
第１溶液が含むＢａ源は、Ｂａを含む化合物（例えば有機酸塩）であれば特に制限されないが、トリフルオロ酢酸バリウムが特に好ましい。トリフルオロ酢酸バリウムは、無水和物であってもよく、水和物であってもよい。第１溶液は、Ｂａ源を１種のみ含んでいてもよく、２種以上含んでいてもよい。The Ba source contained in the first solution is not particularly limited as long as it is a compound containing Ba (e.g., an organic acid salt), but barium trifluoroacetate is particularly preferred. Barium trifluoroacetate may be an anhydrate or a hydrate. The first solution may contain only one type of Ba source, or may contain two or more types.
第１溶液が含むＣｕ源は、Ｃｕを含む化合物（例えば有機酸塩）であれば特に制限されないが、反応性等の観点で、炭素数６～１６の分岐飽和脂肪族カルボン酸の銅塩、または炭素数６～１６の脂環族カルボン酸の銅塩が好ましい。銅塩は、無水和物であってもよく、水和物であってもよい。炭素数６～１６の分岐飽和脂肪族カルボン酸の例には、２－エチルヘキサン酸、イソノナン酸、ネオデカン酸等が含まれる。一方、炭素数６～１６の脂環族カルボン酸の例には、シクロヘキサンカルボン酸、メチルシクロヘキサンカルボン酸、ナフテン酸等が含まれる。これらの中でも、ネオデカン酸銅、２－エチルヘキサン酸銅、イソノナン酸銅が安定性や溶解性等の観点で特に好ましい。第１溶液は、Ｃｕ源を１種のみ含んでいてもよく、２種以上含んでいてもよい。The Cu source contained in the first solution is not particularly limited as long as it is a compound containing Cu (e.g., an organic acid salt), but from the viewpoint of reactivity, etc., a copper salt of a branched saturated aliphatic carboxylic acid having 6 to 16 carbon atoms or a copper salt of an alicyclic carboxylic acid having 6 to 16 carbon atoms is preferred. The copper salt may be an anhydrate or a hydrate. Examples of branched saturated aliphatic carboxylic acids having 6 to 16 carbon atoms include 2-ethylhexanoic acid, isononanoic acid, neodecanoic acid, etc. On the other hand, examples of alicyclic carboxylic acids having 6 to 16 carbon atoms include cyclohexane carboxylic acid, methylcyclohexane carboxylic acid, naphthenic acid, etc. Among these, copper neodecanoate, copper 2-ethylhexanoate, and copper isononanoate are particularly preferred from the viewpoint of stability, solubility, etc. The first solution may contain only one type of Cu source, or may contain two or more types.
第１溶液が含むＭ源は、Ｍ（Ｚｒ、Ｈｆ、Ｉｒ、Ｓｎ、Ｃｅ、Ｔｉ、またはＮｂ）を含む化合物（例えば有機酸塩）であれば特に制限されないが２－エチルヘキサン酸ジルコニル、テトラキス（２，２，６，６－テトラメチル－３，５－ヘプタンジオナト）ハフニウム等が、安定性や溶解性の観点でより好ましい。第１溶液は、Ｍ源を１種のみ含んでいてもよく、２種以上含んでいてもよい。The M source contained in the first solution is not particularly limited as long as it is a compound (e.g., an organic acid salt) containing M (Zr, Hf, Ir, Sn, Ce, Ti, or Nb), but zirconyl 2-ethylhexanoate, tetrakis(2,2,6,6-tetramethyl-3,5-heptanedionato)hafnium, etc. are more preferred from the viewpoint of stability and solubility. The first solution may contain only one type of M source, or may contain two or more types.
ここで、第１溶液がＭ源を含まない場合、第１溶液中の金属元素のモル比Ｒｅ：Ｂａ：Ｃｕは１．０：１．４～１．９：３．０～３．２が好ましく１．０：１．５～１．８：３．０がより好ましい。金属元素のモル比、特にＢａ元素のモル比が上記範囲であると、上述のように、得られる超電導層にＢａ化合物の異相が生じ難く、臨界電流密度が所望の範囲になりやすい。Here, when the first solution does not contain an M source, the molar ratio of the metal elements in the first solution, Re:Ba:Cu, is preferably 1.0:1.4-1.9:3.0-3.2, and more preferably 1.0:1.5-1.8:3.0. When the molar ratio of the metal elements, particularly the molar ratio of the Ba element, is within the above range, as described above, a different phase of Ba compounds is unlikely to occur in the obtained superconducting layer, and the critical current density is likely to be within the desired range.
一方、第１溶液がＭ源を含む場合、第１溶液中の金属元素のモル比Ｒｅ：Ｂａ：Ｃｕ：Ｍは、１．０：１．４～２．２：３．０～３．２：０．０５～０．３０が好ましく、１．０：１．６～２．０：３．０：０．１０～０．１５がより好ましい。第１溶液がＭ源を含む場合、上述のように、得られる超電導層中に、ＢａおよびＭを含む酸化物粒子が形成される。したがって、Ｂａのモル比は、２．０を超えてもよい。ただし、ＲｅＢａ２Ｃｕ３Ｏｘ系化合物を形成するために供される成分のみに着目すると、Ｂａのモル比は２．０未満となる。そのため、得られる超電導層にＢａ化合物の異相が生じ難く、臨界電流密度が所望の範囲になりやすい。 On the other hand, when the first solution contains an M source, the molar ratio of the metal elements in the first solution, Re:Ba:Cu:M, is preferably 1.0:1.4-2.2:3.0-3.2:0.05-0.30, and more preferably 1.0:1.6-2.0:3.0:0.10-0.15. When the first solution contains an M source, as described above, oxide particles containing Ba and M are formed in the obtained superconducting layer. Therefore, the molar ratio of Ba may exceed 2.0. However, when only the components provided to form the ReBa 2 Cu 3 O x -based compound are considered, the molar ratio of Ba is less than 2.0. Therefore, a different phase of Ba compounds is unlikely to occur in the obtained superconducting layer, and the critical current density is likely to be in the desired range.
また、第１溶液は、必要に応じて溶媒を含んでいてもよく、当該溶媒は、上記Ｒｅ源、Ｂａ源、Ｃｕ源、およびＭ源を均一に溶解または分散させることが可能であれば特に制限されず、公知の各種溶媒を用いることができる。また、溶媒の量は、第１溶液の塗布方法や、所望の厚み等に応じて適宜選択される。The first solution may contain a solvent as necessary. The solvent is not particularly limited as long as it can uniformly dissolve or disperse the Re source, Ba source, Cu source, and M source, and various known solvents can be used. The amount of the solvent is appropriately selected depending on the application method of the first solution, the desired thickness, etc.
ここで、第１溶液の塗布方法は、本焼成後の厚み（超電導層換算厚み）が１５０ｎｍ以下の塗膜を形成可能であれば特に制限されず、所望の塗膜の厚みや、第１溶液の粘度等に応じて適宜選択されるが、例えばスピンコート法、ディップコート法、スプレーコート法、バーコート法、スロットダイコート法、インクジェット法等が含まれる。また、本工程で形成する第１溶液の塗膜の超電導層換算厚みは、１５０ｎｍ以下であればよいが、２０～４０ｎｍがより好ましい。塗膜の超電導層換算厚みを１５０ｎｍ以下とした場合に、上述の異物層が表面に生じやすくなり、本発明の効果が得られやすくなる。また、塗膜の超電導層換算厚みを１５０ｎｍ以下とすることで、第１仮焼成工程後の超電導前駆体層中に溶媒や金属有機酸塩が残り難くなり、得られる超電導層中の空孔を少なくできる。Here, the method of applying the first solution is not particularly limited as long as it is possible to form a coating film having a thickness (superconducting layer equivalent thickness) of 150 nm or less after the main baking process, and is appropriately selected according to the desired thickness of the coating film and the viscosity of the first solution, and includes, for example, spin coating, dip coating, spray coating, bar coating, slot die coating, inkjet coating, etc. In addition, the superconducting layer equivalent thickness of the coating film of the first solution formed in this process may be 150 nm or less, but 20 to 40 nm is more preferable. When the superconducting layer equivalent thickness of the coating film is 150 nm or less, the above-mentioned foreign matter layer is likely to be formed on the surface, and the effect of the present invention is easily obtained. In addition, by making the superconducting layer equivalent thickness of the coating film 150 nm or less, it is difficult for solvents and metal organic acid salts to remain in the superconducting precursor layer after the first pre-baking process, and the number of voids in the resulting superconducting layer can be reduced.
さらに、上述の第１溶液がＭ源を含む場合、後述の第１仮焼成工程において、ＢａおよびＭを含む酸化物粒子（磁束ピンニング点）が形成される。このとき形成される酸化物粒子の大きさは通常、超電導前駆体層の厚みより小さくなる。したがって、本工程で形成する塗膜の超電導層換算厚みを１５０ｎｍ以下とすることで、酸化物粒子の平均粒子径を十分に小さくできる。Furthermore, when the first solution described above contains an M source, oxide particles (magnetic flux pinning points) containing Ba and M are formed in the first pre-baking step described below. The size of the oxide particles formed at this time is usually smaller than the thickness of the superconducting precursor layer. Therefore, by setting the superconducting layer equivalent thickness of the coating film formed in this step to 150 nm or less, the average particle size of the oxide particles can be made sufficiently small.
（第１仮焼成工程）
第１仮焼成工程では、上述の第１溶液塗布工程で形成した塗膜を仮焼成し、超電導前駆体層を形成する。本工程で上記塗膜を加熱することにより、第１溶液中の溶媒が除去され、さらにはＲｅ源やＢａ源、Ｃｕ源、Ｍ源中の有機成分が除去される。そして、Ｒｅや、Ｂａ、Ｃｕ等の酸化物を含むアモルファスの超電導前駆体層が形成される。また上述のように、第１溶液がＭ源を含む場合、本工程において超電導前駆体層中にＢａおよびＭを含む酸化物粒子（磁束ピンニング点）が形成される。
(First pre-firing step)
In the first pre-baking step, the coating film formed in the above-mentioned first solution application step is pre-baked to form a superconducting precursor layer. By heating the coating film in this step, the solvent in the first solution is removed, and further, organic components in the Re source, Ba source, Cu source, and M source are removed. Then, an amorphous superconducting precursor layer containing oxides of Re, Ba, Cu, and the like is formed. Also, as described above, when the first solution contains an M source, oxide particles (flux pinning points) containing Ba and M are formed in the superconducting precursor layer in this step.
仮焼成では、昇温速度２～１００℃／分で上記第１溶液の塗膜を加熱し、４５０～５５００℃（最高到達温度）程度まで加熱することが好ましい。昇温速度は５～２０℃がより好ましい。また、最高到達温度は、５００℃がより好ましい。最高到達温度まで到達させた後、冷却し、基板および超電導前駆体層の積層体を取り出す。なお、第１仮焼成工程は、水蒸気を含む酸素雰囲気下で行うことが好ましく、このときの酸素分圧は５０～１０１ｋＰａが好ましく、９８～９９ｋＰａがより好ましい。また、水蒸気分圧は０～１０ｋＰａが好ましく、２～４ｋＰａがより好ましい。酸素分圧および水蒸気分圧を当該範囲とすることで、Ｒｅ源やＢａ源、Ｃｕ源、Ｍ源等が含む有機成分を効率よく除去できる。In the pre-firing, the coating of the first solution is preferably heated at a temperature rise rate of 2 to 100°C/min to about 450 to 5500°C (maximum temperature). The temperature rise rate is more preferably 5 to 20°C. The maximum temperature is more preferably 500°C. After the maximum temperature is reached, the substrate and the superconducting precursor layer laminate are cooled and removed. The first pre-firing step is preferably performed in an oxygen atmosphere containing water vapor, and the oxygen partial pressure at this time is preferably 50 to 101 kPa, more preferably 98 to 99 kPa. The water vapor partial pressure is preferably 0 to 10 kPa, more preferably 2 to 4 kPa. By setting the oxygen partial pressure and water vapor partial pressure within the ranges, organic components contained in the Re source, Ba source, Cu source, M source, etc. can be efficiently removed.
ここで、本発明の製造方法では、第１塗膜形成工程および第１仮焼成工程を複数回繰り返して行うことが好ましく、超電導前駆体層の本焼成後の総厚み（超電導層換算総厚み）が、０．５～５．０μｍとなるまで行うことが好ましい。超電導前駆体層の超電導層換算総厚みは、１．０～２．０μｍがより好ましい。第１塗膜形成工程および第１仮焼成工程の繰り返し回数は、上記総厚みに応じて適宜選択される。Here, in the manufacturing method of the present invention, it is preferable to repeat the first coating film formation step and the first pre-baking step multiple times, and it is preferable to repeat the steps until the total thickness of the superconducting precursor layer after main baking (total thickness in terms of superconducting layer) is 0.5 to 5.0 μm. It is more preferable that the total thickness in terms of superconducting layer of the superconducting precursor layer is 1.0 to 2.0 μm. The number of times that the first coating film formation step and the first pre-baking step are repeated is appropriately selected depending on the total thickness.
（第２溶液塗布工程）
第２溶液塗布工程では、上記第１塗膜形成工程および第１仮焼成工程によって形成された超電導前駆体層上に、Ｂａを含み、かつＣｕを含まない第２溶液を塗布する。なお、Ｃｕを含まないとは、Ｃｕを実質的に含まないことを意味し、本発明の目的および効果を損なわない範囲で、極微量のＣｕを含む場合を排除するものではない。
(Second solution application step)
In the second solution application step, a second solution containing Ba and not containing Cu is applied onto the superconducting precursor layer formed by the first coating film formation step and the first calcination step. Note that not containing Cu means that Cu is substantially not contained, and does not exclude the case where a trace amount of Cu is contained within a range that does not impair the object and effect of the present invention.
第２溶液は、Ｂａ源を必須成分として含み、かつＣｕを含んでいなければよいが、必要に応じてＲｅ源や、Ｍ源、溶媒を含んでいてもよい。第１溶液中の金属元素のモル比によっては、超電導前駆体層の表面側で、ＢａだけでなくＲｅが欠乏したり、磁束ピンニング点（ＢａおよびＭを含む酸化物粒子）が不足したりすることもある。そこで、第２層にＲｅやＭを含有させることで、これらが補うことができる。第２溶液中の金属元素のモル比Ｒｅ：Ｂａ：Ｍは０～１．１：０．０５～５０：０～７が好ましく、１．０：０．６～４０：０．１～４がより好ましい。The second solution must contain a Ba source as an essential component and must not contain Cu, but may contain a Re source, an M source, or a solvent as necessary. Depending on the molar ratio of the metal elements in the first solution, the surface side of the superconducting precursor layer may be deficient in not only Ba but also Re, or the magnetic flux pinning points (oxide particles containing Ba and M) may be insufficient. These can be compensated for by including Re and M in the second layer. The molar ratio of the metal elements Re:Ba:M in the second solution is preferably 0-1.1:0.05-50:0-7, and more preferably 1.0:0.6-40:0.1-4.
ここで、第２溶液の塗布方法は特に制限されず、所望の塗膜の厚みや、第２溶液の粘度等に応じて適宜選択されるが、例えばスピンコート法、ディップコート法、スプレーコート法、バーコート法、スロットダイコート法、インクジェット法等が含まれる。また、第２溶液の塗膜の超電導層換算厚みは、１５０ｎｍ以下がより好ましく、２０～１００ｎｍがさらに好ましい。Here, the method of applying the second solution is not particularly limited and is appropriately selected depending on the desired thickness of the coating film and the viscosity of the second solution, and examples of the method include spin coating, dip coating, spray coating, bar coating, slot die coating, and inkjet methods. The equivalent superconducting layer thickness of the coating film of the second solution is more preferably 150 nm or less, and even more preferably 20 to 100 nm.
（第２仮焼成工程）
第２仮焼成工程では、上述の第２溶液の塗膜を仮焼成し、Ｂａ含有層を形成する。本工程で上記塗膜を加熱することにより、第２溶液中の溶媒が除去され、さらにはＲｅ源やＢａ源、Ｍ源中の有機成分が除去される。そして、Ｒｅや、Ｂａの酸化物を含むアモルファスのＢａ含有層が形成される。また、第２溶液がＭ源を含む場合には、Ｂａ含有層中にＢａおよびＭを含む酸化物粒子（磁束ピンニング点）が形成される。
(Second pre-firing step)
In the second pre-baking step, the coating of the second solution is pre-baked to form a Ba-containing layer. By heating the coating in this step, the solvent in the second solution is removed, and further, the organic components in the Re source, Ba source, and M source are removed. Then, an amorphous Ba-containing layer containing Re and Ba oxides is formed. In addition, when the second solution contains an M source, oxide particles (flux pinning points) containing Ba and M are formed in the Ba-containing layer.
仮焼成では、昇温速度２～１００℃／分で上記第２溶液の塗膜を加熱し、４５０～５５０℃（最高到達温度）程度まで加熱することが好ましい。昇温速度は５～２０℃／分がより好ましい。また、最高到達温度は、５００℃がより好ましい。最高到達温度まで到達させた後、冷却し、基板、超電導前駆体層、およびＢａ含有層の積層体を取り出す。なお、第２仮焼成工程は、水蒸気を含む酸素雰囲気下で行うことが好ましく、このときの酸素分圧は５０～１０１ｋＰａが好ましく、９８～９９ｋＰａがより好ましい。また、水蒸気分圧は０～１０ｋＰａが好ましく、２～４ｋＰａがより好ましい。酸素分圧および水蒸気分圧を当該範囲とすることで、Ｒｅ源やＢａ源、Ｍ源が含む有機成分を除去できる。In the pre-firing, the coating of the second solution is preferably heated at a temperature rise rate of 2 to 100°C/min to about 450 to 550°C (maximum temperature). The temperature rise rate is more preferably 5 to 20°C/min. The maximum temperature is more preferably 500°C. After the maximum temperature is reached, the substrate is cooled, and the laminate of the substrate, the superconducting precursor layer, and the Ba-containing layer is removed. The second pre-firing step is preferably performed in an oxygen atmosphere containing water vapor, and the oxygen partial pressure at this time is preferably 50 to 101 kPa, more preferably 98 to 99 kPa. The water vapor partial pressure is preferably 0 to 10 kPa, more preferably 2 to 4 kPa. By setting the oxygen partial pressure and water vapor partial pressure within the ranges, organic components contained in the Re source, Ba source, and M source can be removed.
本発明の製造方法では、第２溶液塗布工程および第２仮焼成工程を複数回繰り返して行ってもよい。Ｂａ含有層の総厚みは、超電導前駆体層の厚みや、Ｂａの不足状態等に応じて適宜選択されるが、通常０．０２～１．５０μｍが好ましく、０．０３～０．５μｍがより好ましい。Ｂａ含有層の総厚みが当該範囲であると、後述の本焼成工程において、Ｂａの不足によって形成される異物とＢａ含有層とを十分に反応させることが可能となる。第２溶液塗布工程および第２仮焼成工程の繰り返し回数は、所望のＢａ含有層の厚みに応じて適宜選択される。In the manufacturing method of the present invention, the second solution application step and the second pre-baking step may be repeated multiple times. The total thickness of the Ba-containing layer is appropriately selected depending on the thickness of the superconducting precursor layer, the Ba deficiency state, etc., but is usually preferably 0.02 to 1.50 μm, and more preferably 0.03 to 0.5 μm. If the total thickness of the Ba-containing layer is within this range, it is possible to sufficiently react the Ba-containing layer with foreign matter formed due to the Ba deficiency in the main baking step described later. The number of times the second solution application step and the second pre-baking step are repeated is appropriately selected depending on the desired thickness of the Ba-containing layer.
（本焼成工程）
本焼成工程では、上述の工程で作製した、超電導前駆体層およびＢａ含有層を本焼成する。本焼成を行うと、超電導前駆体層と水蒸気とが反応し、基板と超電導前駆体層との間に液相が形成される。そして、当該液相に超電導前駆体層中の金属元素が溶融し、基板側からＲｅＢａ２Ｃｕ３Ｏｘ系化合物がエピタキシャル成長する。そして、超電導前駆体層の表面側まで結晶成長すると、Ｂａの不足によって生じた異物とＢａ含有層中のＢａが固相反応する。その結果、基板側から表面側にかけて略均一な組成の超電導層が得られる。
(Main firing process)
In the firing step, the superconducting precursor layer and the Ba-containing layer prepared in the above steps are fired. When firing is performed, the superconducting precursor layer reacts with water vapor, and a liquid phase is formed between the substrate and the superconducting precursor layer. Then, the metal elements in the superconducting precursor layer melt in the liquid phase, and a ReBa 2 Cu 3 O x compound grows epitaxially from the substrate side. Then, when the crystals grow to the surface side of the superconducting precursor layer, the foreign matter generated due to the shortage of Ba reacts with Ba in the Ba-containing layer in a solid phase. As a result, a superconducting layer having a substantially uniform composition from the substrate side to the surface side is obtained.
本焼成工程では、昇温速度５～２００℃／分で超電導前駆体層およびＢａ含有層を昇温することが好ましい。昇温速度は１０～４０℃／分がより好ましい。そして、７２０～８２０℃で２０～７２０分保持することが好ましい。また、焼成温度は、７４０～７６０℃がより好ましい。さらに、焼成時間は、６０～２４０分がより好ましい。なお、本焼成工程は、全圧５～１０１ｋＰａで行うことが好ましく、このときの酸素分圧は０．０１～０．１０ｋＰａ、水蒸気分圧は０．０５～５０ｋＰａとすることが好ましい。酸素分圧や水蒸気分圧を当該範囲とすることで、効率よくＲｅＢａ２Ｃｕ３Ｏｘ系化合物が形成される。 In the firing step, the superconducting precursor layer and the Ba-containing layer are preferably heated at a heating rate of 5 to 200° C./min. The heating rate is more preferably 10 to 40° C./min. The temperature is preferably maintained at 720 to 820° C. for 20 to 720 minutes. The firing temperature is more preferably 740 to 760° C. The firing time is more preferably 60 to 240 minutes. The firing step is preferably performed at a total pressure of 5 to 101 kPa, and the oxygen partial pressure is preferably 0.01 to 0.10 kPa and the water vapor partial pressure is preferably 0.05 to 50 kPa. By setting the oxygen partial pressure and the water vapor partial pressure in the above ranges, the ReBa 2 Cu 3 O x compound is efficiently formed.
（他の工程）
本発明の超電導体の製造方法は、上記基板準備工程、第１溶液塗布工程、第１仮焼成工程、第２溶液塗布工程、第２仮焼成工程、および本焼成工程以外に、必要に応じて他の工程を含んでいてもよい。
(Other processes)
The method for manufacturing a superconductor of the present invention may include other steps as necessary in addition to the above-mentioned substrate preparation step, first solution application step, first pre-baking step, second solution application step, second pre-baking step, and main baking step.
例えば上記第２仮焼成工程の後、本焼成工程の前に中間熱処理工程を含んでも良い。中間熱処理を行うと、超電導体前駆体膜の結晶化が進行し、本焼成工程においてＢａＭＯ３粒子の生成反応が低温で起こるようになり、その結果、ＢａＭＯ３粒子が微細化する。 For example, an intermediate heat treatment process may be included after the second pre-baking process and before the main baking process. When the intermediate heat treatment is performed, the crystallization of the superconductor precursor film progresses, and the reaction for generating BaMO3 particles occurs at a low temperature in the main baking process, resulting in fine BaMO3 particles.
中間熱処理工程では、昇温速度５～２００℃／分で超電導前駆体層およびＢａ含有層を昇温することが好ましい。昇温速度は２０～５０℃／分がより好ましい。そして、５５０～６５０℃で０．５～５０時間保持することが好ましい。また、熱処理温度は、５８０℃がより好ましい。さらに、中間熱処理時間は、２～５時間がより好ましい。なお、中間熱処理工程は、全圧５～１０１ｋＰａで行うことが好ましく、このときの水蒸気分圧は０．０１～５０ｋＰａとすることが好ましい。水蒸気分圧を当該範囲とすることで、本焼成工程において微細なＢａＭＯ３粒子および良好なＲｅＢａ２Ｃｕ３Ｏｘ系化合物が形成される。 In the intermediate heat treatment step, the superconducting precursor layer and the Ba-containing layer are preferably heated at a heating rate of 5 to 200°C/min. The heating rate is more preferably 20 to 50°C/min. The temperature is preferably kept at 550 to 650°C for 0.5 to 50 hours. The heat treatment temperature is more preferably 580°C. The intermediate heat treatment time is more preferably 2 to 5 hours. The intermediate heat treatment step is preferably performed at a total pressure of 5 to 101 kPa, and the water vapor partial pressure at this time is preferably 0.01 to 50 kPa . By setting the water vapor partial pressure within this range, fine BaMO3 particles and good ReBa2Cu3Ox - based compounds are formed in the main firing step.
例えば上記超電導層上に安定化層を形成する工程等を含んでいてもよい。安定化層の形成方法は特に制限されず、例えば銅、銀、金や白金、あるいはこれらの積層膜および合金等をスパッタ法等で堆積させる工程とすることができる。For example, the method may include a step of forming a stabilizing layer on the superconducting layer. The method of forming the stabilizing layer is not particularly limited, and may be, for example, a step of depositing copper, silver, gold, platinum, or a laminated film or alloy thereof by a sputtering method or the like.
以下、本発明を実施例により更に詳細に説明する。しかしながら、本発明の範囲はこれによって何ら制限を受けない。The present invention will now be described in more detail with reference to examples. However, the scope of the present invention is not limited thereby.
［実施例１］
（基板準備工程）
１０ｍｍ×３５ｍｍのハステロイ（登録商標）Ｃ２７６と、厚み６０ｎｍのＧｄ２Ｚｒ２Ｏ７からなる第１中間層と、厚み２０ｎｍのＹ２Ｏ３からなる第２中間層と、厚み５ｎｍのＭｇＯからなる第３中間層と、厚み１０ｎｍのＬａＭｎＯ３からなる第４中間層と、厚み０．７μｍのＣｅＯ２からなる第５中間層と、がこの順に積層された基板を準備した。
[Example 1]
(Substrate preparation process)
A substrate was prepared in which a 10 mm x 35 mm Hastelloy (registered trademark) C276, a first intermediate layer made of Gd2Zr2O7 having a thickness of 60 nm, a second intermediate layer made of Y2O3 having a thickness of 20 nm, a third intermediate layer made of MgO having a thickness of 5 nm, a fourth intermediate layer made of LaMnO3 having a thickness of 10 nm, and a fifth intermediate layer made of CeO2 having a thickness of 0.7 μm were laminated in this order.
（第１溶液塗布工程および第１仮焼成工程）
一方、プロピオン酸イットリウム、プロピオン酸ガドリニウム、トリフルオロ酢酸バリウム、２－エチルヘキサン酸銅、および２－エチルヘキサン酸ジルコニルを準備し、金属元素の比Ｙ：Ｇｄ：Ｂａ：Ｃｕ：Ｚｒが０．７７：０．２３：１．６：３．０：０．１となるように混合して第１溶液とした。
(First solution application step and first pre-baking step)
Meanwhile, yttrium propionate, gadolinium propionate, barium trifluoroacetate, copper 2-ethylhexanoate, and zirconyl 2-ethylhexanoate were prepared and mixed such that the ratio of metal elements Y:Gd:Ba:Cu:Zr was 0.77:0.23:1.6:3.0:0.1 to prepare a first solution.
上記基板上に、スピンコート法により、第１溶液を塗布厚みが３０ｎｍとなるように塗布した。そして、第１溶液を塗布した基板を小型環状電気炉に入れ、酸素雰囲気中、昇温速度：１０℃／分にて５００℃まで加熱して仮焼成し、超電導前駆体層を形成した。その後、炉冷し、基板を取り出した。再度、当該超電導前駆体層上に、上述の第１溶液を塗布厚みが３０ｎｍとなるように塗布し、上記と同様に仮焼成した。第１溶液の塗布および仮焼成を繰り返し、超電導前駆体層を２０層積層した。The first solution was applied to the substrate by spin coating to a thickness of 30 nm. The substrate coated with the first solution was then placed in a small circular electric furnace and pre-baked in an oxygen atmosphere at a heating rate of 10°C/min to 500°C to form a superconducting precursor layer. The furnace was then cooled, and the substrate was removed. The above-mentioned first solution was again applied to the superconducting precursor layer to a thickness of 30 nm, and pre-baked in the same manner as above. The application of the first solution and pre-baking were repeated to stack 20 layers of superconducting precursor layers.
（第２溶液塗布工程および第２仮焼成工程）
続いて、上記超電導前駆体層上に、トリフルオロ酢酸バリウム（第２溶液）をＢａ含有層厚みが２０ｎｍとなるように塗布した。そして、上記と同様に小型環状電気炉内で仮焼成し、Ｂａ含有層を形成した。第２溶液の塗布および仮焼成を繰り返し、Ｂａ含有層を５層積層した。
(Second solution application step and second pre-baking step)
Next, barium trifluoroacetate (second solution) was applied onto the superconducting precursor layer so that the Ba-containing layer had a thickness of 20 nm. Then, the Ba-containing layer was formed by pre-firing in a small circular electric furnace in the same manner as above. The application of the second solution and pre-firing were repeated to stack five Ba-containing layers.
（本焼成工程）
上記超電導前駆体層およびＢａ含有層を形成した基板を小型環状電気炉に入れ、全圧：３０ｋＰａ（酸素分圧４０Ｐａ、水蒸気分圧１．７ｋＰａ）とした。そして、昇温速度：１０℃／分にて７５０℃まで温度を上げ、当該温度で１００分焼成し、超電導層を有する超電導体を得た。
(Main firing process)
The substrate on which the superconducting precursor layer and the Ba-containing layer were formed was placed in a small circular electric furnace under a total pressure of 30 kPa (oxygen partial pressure: 40 Pa, water vapor partial pressure: 1.7 kPa). The temperature was then raised to 750°C at a heating rate of 10°C/min, and sintered at that temperature for 100 minutes to obtain a superconductor having a superconducting layer.
（超電導体の物性）
得られた超電導層の厚みは０．６０μｍであった。さらに、超電導層中の金属元素のモル比をＩＣＰ発光分光分析装置により測定したところ、Ｙ：Ｇｄ：Ｂａ：Ｃｕ：Ｚｒは、１．０：２．０：３．０：０．１であった。また、ＢａおよびＺｒを含む酸化物粒子（磁束ピンニング点）の量を組成から計算したところ、４体積％であった。さらに、図２に示すように当該超電導体（超電導層）を９つの領域に区分し、各領域における１０ｍｍ間の表面抵抗をテスターで測定した。当該測定値の平均値は、８４Ωであった。さらに、７７Ｋ、自己磁場中での臨界電流値（Ｉｃ）を４端子法により測定したところ、Ｉｃ＝３３４Ａ／ｃｍ-ｗで、臨界電流密度（Ｊｃ）は５．６ＭＡ／ｃｍ２であった。
(Physical properties of superconductors)
The thickness of the obtained superconducting layer was 0.60 μm. Furthermore, the molar ratio of the metal elements in the superconducting layer was measured by an ICP emission spectrometer, and the ratio was 1.0:2.0:3.0:0.1 for Y:Gd:Ba:Cu:Zr. The amount of oxide particles (flux pinning points) containing Ba and Zr was calculated from the composition to be 4% by volume. Furthermore, as shown in FIG. 2, the superconductor (superconducting layer) was divided into nine regions, and the surface resistance of each region was measured over a 10 mm distance using a tester. The average value of the measured values was 84 Ω. Furthermore, the critical current value (Ic) in the self-magnetic field at 77 K was measured by a four-terminal method, and the Ic was 334 A/cm-w, and the critical current density (Jc) was 5.6 MA/cm 2 .
図３Ａに実施例１で得られた超電導体の断面の走査電子顕微鏡写真を示す。当該断面の顕微鏡写真から、超電導層４の面積に対する、空孔の面積の割合を特定したところ、１％未満であった。 Figure 3A shows a scanning electron microscope photograph of the cross section of the superconductor obtained in Example 1. From the microscope photograph of the cross section, the ratio of the area of the voids to the area of the superconducting layer 4 was determined to be less than 1%.
［実施例２］
第２溶液を、プロピオン酸イットリウムおよびトリフルオロ酢酸バリウムの混合液（金属元素のモル比Ｙ：Ｂａ＝１．０：９．０）とした以外は、実施例１と同様に超電導体を作製した。
[Example 2]
A superconductor was produced in the same manner as in Example 1, except that the second solution was a mixed solution of yttrium propionate and barium trifluoroacetate (the molar ratio of metal elements Y:Ba=1.0:9.0).
得られた超電導層の厚みは０．６３μｍであった。さらに超電導層中の金属元素のモル比をＩＣＰ発光分光分析装置により測定したところＹ：Ｇｄ：Ｂａ：Ｃｕ：Ｚｒは、１．１：２．１：３．０：０．１であった。また、ＢａおよびＺｒを含む酸化物粒子（磁束ピンニング点）の量を組成から計算したところ、４体積％であった。さらに、実施例１と同様に超電導層の表面抵抗を測定したところ、５５Ωであった。さらに、７７Ｋ、自己磁場中での臨界電流値（Ｉｃ）および臨界電流密度（Ｊｃ）を測定したところ、Ｉｃ＝３６１Ａ／ｃｍであり、Ｊｃ＝５．７ＭＡ／ｃｍ２であった。 The thickness of the obtained superconducting layer was 0.63 μm. Furthermore, the molar ratio of the metal elements in the superconducting layer was measured by an ICP emission spectrometer, and the ratio was 1.1:2.1:3.0:0.1. The amount of oxide particles (flux pinning points) containing Ba and Zr was calculated from the composition and found to be 4% by volume. Furthermore, the surface resistance of the superconducting layer was measured in the same manner as in Example 1 and found to be 55 Ω. Furthermore, the critical current value (I c ) and critical current density (J c ) in the self-magnetic field at 77 K were measured and found to be I c = 361 A/cm and J c = 5.7 MA/cm 2 .
図３Ｂに実施例２で得られた超電導体の断面の走査電子顕微鏡写真を示す。当該断面の顕微鏡写真から、超電導層４の面積に対する、空孔の面積の割合を特定したところ、１％未満であった。 Figure 3B shows a scanning electron microscope photograph of the cross section of the superconductor obtained in Example 2. From the microscope photograph of the cross section, the ratio of the area of the voids to the area of the superconducting layer 4 was determined to be less than 1%.
［比較例１］
第２溶液の塗布および焼成（Ｂａ含有層の形成）を行わなかった以外は、実施例１と同様に超電導体を作製した。
[Comparative Example 1]
A superconductor was produced in the same manner as in Example 1, except that the application of the second solution and the firing (formation of the Ba-containing layer) were not carried out.
得られた超電導層の厚みは０．６０μｍであった。さらに、超電導相中の金属元素のモル比をＩＣＰ発光分光分析装置により測定したところ、Ｙ：Ｇｄ：Ｂａ：Ｃｕ：Ｚｒが１．０：１．６：３．０：０．１であった。ＢａおよびＺｒを含む酸化物粒子（磁束ピンニング点）の量を組成から計算したところ、６体積％であった。さらに、実施例１と同様に超電導層の表面抵抗を測定したところ、４７００Ωであった。さらに、７７Ｋ、自己磁場中での臨界電流値（Ｉｃ）および臨界電流密度（Ｊｃ）を測定したところ、Ｉｃ＝２９３Ａ／ｃｍ－ｗであり、Ｊｃ＝４．９ＭＡ／ｃｍ２であった。 The thickness of the obtained superconducting layer was 0.60 μm. Furthermore, the molar ratio of metal elements in the superconducting phase was measured by an ICP emission spectrometer, and it was found that Y:Gd:Ba:Cu:Zr was 1.0:1.6:3.0:0.1. The amount of oxide particles (flux pinning points) containing Ba and Zr was calculated from the composition to be 6 volume %. Furthermore, the surface resistance of the superconducting layer was measured in the same manner as in Example 1, and it was 4700 Ω. Furthermore, the critical current value (I c ) and the critical current density (J c ) in the self-magnetic field at 77 K were measured, and they were I c = 293 A/cm-w and J c = 4.9 MA/cm 2 .
図４Ａに比較例１で得られた超電導体の断面の走査電子顕微鏡写真を示す。当該断面の顕微鏡写真から、超電導層４の面積に対する、空孔の面積の割合を特定したところ、１％未満であった。 Figure 4A shows a scanning electron microscope photograph of the cross section of the superconductor obtained in Comparative Example 1. From the microscope photograph of the cross section, the ratio of the area of the voids to the area of the superconducting layer 4 was determined to be less than 1%.
［比較例２］
第１溶液の塗布厚みを２２０ｎｍとし、実施例１と同様に仮焼成を行い、超電導前駆体層を形成した。これを繰り返し、超電導前駆体層を３層積層した。その後、第２溶液の塗布および焼成（Ｂａ含有層の形成）を行なうことなく、実施例１と同様に本焼成を行って、超電導体を得た。
[Comparative Example 2]
The coating thickness of the first solution was set to 220 nm, and a pre-baking was performed in the same manner as in Example 1 to form a superconducting precursor layer. This was repeated to stack three superconducting precursor layers. Thereafter, main baking was performed in the same manner as in Example 1 without coating the second solution and baking (forming a Ba-containing layer), to obtain a superconductor.
得られた超電導層の厚みは０．６６μｍであった。さらに、超電導相中の金属元素のモル比は、Ｙ：Ｇｄ：Ｂａ：Ｃｕ：Ｚｒが１．０：１．６：３．０：０．１であった。ＢａおよびＺｒを含む酸化物粒子（磁束ピンニング点）の量をＩＣＰ発光分光分析装置により測定したところ、６体積％であった。さらに、実施例１と同様に超電導層の表面抵抗を測定したところ、４３００Ωであった。また、当該超電導体について、７７Ｋ、自己磁場中での臨界電流値（Ｉｃ）および臨界電流密度（Ｊｃ）を測定したところ、Ｉｃ＝２２６Ａ／ｃｍであり、Ｊｃ＝３．４ＭＡ／ｃｍ２であった。 The thickness of the obtained superconducting layer was 0.66 μm. Furthermore, the molar ratio of metal elements in the superconducting phase was Y:Gd:Ba:Cu:Zr, which was 1.0:1.6:3.0:0.1. The amount of oxide particles (flux pinning points) containing Ba and Zr was measured by an ICP emission spectrometer and found to be 6% by volume. Furthermore, the surface resistance of the superconducting layer was measured as in Example 1 and found to be 4300Ω. Furthermore, the critical current value (I c ) and critical current density (J c ) of the superconductor in a self-magnetic field at 77K were measured and found to be I c =226 A/cm and J c =3.4 MA/cm 2 .
図４Ｂに比較例２で得られた超電導体の断面の走査電子顕微鏡写真を示す。当該断面の顕微鏡写真から、超電導層４の面積に対する、空孔の面積の割合を特定したところ、４．４％であった。 Figure 4B shows a scanning electron microscope photograph of the cross section of the superconductor obtained in Comparative Example 2. From the microscope photograph of the cross section, the ratio of the area of the voids to the area of the superconducting layer 4 was determined to be 4.4%.
［考察］
上記のように、超電導前駆体層を形成後、Ｂａ含有層を形成し、本焼成を行った場合（実施例１および実施例２）、Ｂａ含有層を形成しない場合（比較例１）と比較して、表面抵抗が格段に下がった。比較例１では、図４Ａに示されるように、超電導層４の表面に異物層が形成されており、これが、表面抵抗を高めていると考えられる。これに対し、実施例１および２では、図３Ａおよび図３Ｂに示されるように、超電導層４の表面に異物を含む層がほとんど見られない。超電導前駆体層とＢａ含有層とを共に焼成することで、所望のＲｅＢａ２Ｃｕ３Ｏｘ系化合物に変化し、その結果、表面抵抗が下がったといえる。
[Discussion]
As described above, when the Ba-containing layer was formed after the superconducting precursor layer was formed and then the firing was performed (Examples 1 and 2), the surface resistance was significantly reduced compared to when the Ba-containing layer was not formed (Comparative Example 1). In Comparative Example 1, as shown in FIG. 4A, a foreign matter layer was formed on the surface of the superconducting layer 4, which is considered to increase the surface resistance. In contrast, in Examples 1 and 2, as shown in FIG. 3A and FIG. 3B, a layer containing foreign matter was hardly observed on the surface of the superconducting layer 4. By firing the superconducting precursor layer and the Ba-containing layer together, they were changed into the desired ReBa 2 Cu 3 O x compound, and as a result, the surface resistance was reduced.
一方、比較例２のように、図４Ｂに示すように、厚みの厚い超電導前駆体層を形成した場合、超電導層４の表面だけでなく、内部にも異物が見られた。On the other hand, when a thick superconducting precursor layer was formed as in Comparative Example 2, as shown in Figure 4B, foreign matter was found not only on the surface of the superconducting layer 4 but also inside it.
本出願は、２０２０年５月２５日出願の特願２０２０－０９０６０５号に基づく優先権を主張する。当該出願明細書および図面に記載された内容は、すべて本願明細書に援用される。This application claims priority from Japanese Patent Application No. 2020-090605, filed May 25, 2020. The contents of the specification and drawings of that application are incorporated herein by reference in their entirety.
本発明の超電導体の製造方法によれば、臨界電流密度が高く、かつ表面抵抗が十分に低い超電導体を複雑な工程等を経ることなく作製可能である。当該超電導体は、超電導マグネット、超電導ケーブル、電力機器及びデバイス等に適用可能である。According to the method for manufacturing a superconductor of the present invention, it is possible to produce a superconductor having a high critical current density and a sufficiently low surface resistance without going through complicated processes, etc. The superconductor can be applied to superconducting magnets, superconducting cables, electric power equipment and devices, etc.
１ 基板
２、２ａ、２ｂ、２ｃ 超電導前駆体層
３ Ｂａ含有層
４ 超電導層
1 Substrate 2, 2a, 2b, 2c Superconducting precursor layer 3 Ba-containing layer 4 Superconducting layer
Claims (10)
前記基板上に配置された、ＲｅＢａ２Ｃｕ３Ｏｘ系化合物（Ｒｅは、Ｙ、Ｎｄ、Ｓｍ、Ｇｄ、Ｄｙ、Ｅｕ、Ｅｒ、Ｙｂ、Ｐｒ、およびＨｏからなる群から選択される、少なくとも１種の元素を表し、ｘは６．２～７．０を表す）を含む超電導層と、
を有し、
前記超電導層の７７Ｋにおける表面抵抗が１ｋΩ以下であり、
前記超電導層の７７Ｋ、自己磁場中での臨界電流密度が３．０ＭＡ／ｃｍ２以上である、
超電導体。 A substrate;
a superconducting layer including a ReBa 2 Cu 3 O x compound (Re represents at least one element selected from the group consisting of Y, Nd, Sm, Gd, Dy, Eu, Er, Yb, Pr, and Ho, and x represents 6.2 to 7.0) disposed on the substrate;
having
the surface resistance of the superconducting layer at 77 K is 1 kΩ or less;
The superconducting layer has a critical current density of 3.0 MA/ cm2 or more at 77K in a self-magnetic field.
Superconductor.
請求項１に記載の超電導体。 In a cross section perpendicular to a lamination surface of the substrate and the superconducting layer, an area of voids contained in the superconducting layer is 3% or less of an area of the superconducting layer.
The superconductor according to claim 1.
請求項１または２に記載の超電導体。 Oxide particles containing Ba and M (M represents at least one element selected from the group consisting of Zr, Hf, Ir, Sn, Ce, Ti, and Nb) are dispersed in the superconducting layer in an amount of 20 volume % or less.
3. The superconductor according to claim 1 or 2.
請求項１～３のいずれか一項に記載の超電導体。 The molar ratio of metal elements in the superconducting layer, Re:Ba:Cu:M, is 1.0-1.2:1.8-2.5:3.0-3.1:0-0.4.
The superconductor according to any one of claims 1 to 3.
請求項１～４のいずれか一項に記載の超電導体。 The substrate has a support and an intermediate layer having biaxial orientation disposed on the support.
The superconductor according to any one of claims 1 to 4.
請求項１～５のいずれか一項に記載の超電導体。 A wire material,
The superconductor according to any one of claims 1 to 5.
前記基板上に、Ｒｅ（Ｒｅは、Ｙ、Ｎｄ、Ｓｍ、Ｇｄ、Ｄｙ、Ｅｕ、Ｅｒ、Ｙｂ、ＰｒおよびＨｏからなる群から選択される少なくとも１種の元素を表す）、Ｂａ、およびＣｕを少なくとも含み、金属元素のモル比Ｒｅ：Ｂａ：Ｃｕ：Ｍが１．０：１．４～２．２：３．０～３．２：０～０．３である（Ｍは、Ｚｒ、Ｈｆ、Ｉｒ、Ｓｎ、Ｃｅ、Ｔｉ、およびＮｂからなる群から選択される少なくとも１種の元素を表し、Ｍのモル比が０であるとき、Ｂａのモル比は２．０未満である）第１溶液を塗布して、焼成後の厚みが１５０ｎｍ以下となるように塗膜を形成し、前記第１溶液の塗膜を仮焼成するステップを繰り返し行って、超電導前駆体層を形成する工程と、
前記超電導前駆体層上に、Ｃｕ元素を含まず、かつ金属元素のモル比Ｒｅ：Ｂａ：Ｍが０～１．１：０．０５～５５：０～７である第２溶液を塗布し、前記第２溶液の塗膜を仮焼成するステップを繰り返し行って、Ｂａ含有層を形成する工程と、
前記超電導前駆体層および前記Ｂａ含有層を本焼成し、超電導層を形成する工程と、
を含む、
超電導体の製造方法。 providing a substrate;
a step of applying a first solution containing at least Re (Re represents at least one element selected from the group consisting of Y, Nd, Sm, Gd, Dy, Eu, Er, Yb, Pr, and Ho), Ba, and Cu, and having a molar ratio of metal elements Re:Ba:Cu:M of 1.0:1.4-2.2:3.0-3.2:0-0.3 (M represents at least one element selected from the group consisting of Zr, Hf, Ir, Sn, Ce, Ti, and Nb, and when the molar ratio of M is 0, the molar ratio of Ba is less than 2.0) onto the substrate to form a coating film having a thickness of 150 nm or less after firing, and then provisionally firing the coating film of the first solution, thereby forming a superconducting precursor layer;
a step of repeatedly applying a second solution, which does not contain Cu element and has a molar ratio of metal elements Re:Ba:M of 0-1.1:0.05-55:0-7, onto the superconducting precursor layer and calcining the applied film of the second solution, to form a Ba-containing layer;
sintering the superconducting precursor layer and the Ba-containing layer to form a superconducting layer;
including,
A method for manufacturing superconductors.
請求項７に記載の超電導体の製造方法。 the step of subjecting the superconducting precursor layer and the Ba-containing layer to an intermediate heat treatment after the step of forming the Ba-containing layer and before the step of firing the superconducting precursor layer and the Ba-containing layer;
The method for producing a superconductor according to claim 7.
請求項７または８に記載の超電導体の製造方法。 The molar ratio of metal elements Re:Ba:M in the second solution is 0.9-1.0:0.05-55:0-7;
The method for producing a superconductor according to claim 7 or 8.
請求項７～９のいずれか一項に記載の超電導体の製造方法。 the molar ratio of metal elements Re:Ba:Cu:M in the superconducting layer obtained after the main firing is 1.0-1.2:1.8-2.5:3.0-3.1:0-0.4;
The method for producing a superconductor according to any one of claims 7 to 9.
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| JP2012113860A (en) | 2010-11-22 | 2012-06-14 | Sumitomo Electric Ind Ltd | Superconducting oxide thin film wire rod, and method for manufacturing the same |
| JP2013012354A (en) | 2011-06-28 | 2013-01-17 | Furukawa Electric Co Ltd:The | Method for manufacturing superconducting wire |
| JP2013235766A (en) | 2012-05-10 | 2013-11-21 | Sumitomo Electric Ind Ltd | Oxide superconducting thin film and method for manufacturing the same |
| JP2019102178A (en) | 2017-11-29 | 2019-06-24 | 昭和電線ケーブルシステム株式会社 | Manufacturing method of superconducting wire rod |
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| JP2012113860A (en) | 2010-11-22 | 2012-06-14 | Sumitomo Electric Ind Ltd | Superconducting oxide thin film wire rod, and method for manufacturing the same |
| JP2013012354A (en) | 2011-06-28 | 2013-01-17 | Furukawa Electric Co Ltd:The | Method for manufacturing superconducting wire |
| JP2013235766A (en) | 2012-05-10 | 2013-11-21 | Sumitomo Electric Ind Ltd | Oxide superconducting thin film and method for manufacturing the same |
| JP2019102178A (en) | 2017-11-29 | 2019-06-24 | 昭和電線ケーブルシステム株式会社 | Manufacturing method of superconducting wire rod |
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