JP2004200100A - Bi series oxide superconductor - Google Patents
Bi series oxide superconductor Download PDFInfo
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- JP2004200100A JP2004200100A JP2002369567A JP2002369567A JP2004200100A JP 2004200100 A JP2004200100 A JP 2004200100A JP 2002369567 A JP2002369567 A JP 2002369567A JP 2002369567 A JP2002369567 A JP 2002369567A JP 2004200100 A JP2004200100 A JP 2004200100A
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- based oxide
- oxide superconductor
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- silver alloy
- superconductor
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- 239000002887 superconductor Substances 0.000 title claims abstract description 52
- 229910001316 Ag alloy Inorganic materials 0.000 claims abstract description 26
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims abstract description 25
- 229910052709 silver Inorganic materials 0.000 claims abstract description 25
- 239000004332 silver Substances 0.000 claims abstract description 24
- 239000011159 matrix material Substances 0.000 claims abstract description 15
- 238000009792 diffusion process Methods 0.000 claims abstract description 14
- 229910052802 copper Inorganic materials 0.000 claims abstract description 8
- 229910052797 bismuth Inorganic materials 0.000 claims abstract description 7
- 229910052712 strontium Inorganic materials 0.000 claims abstract description 7
- 229910052749 magnesium Inorganic materials 0.000 claims abstract description 4
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 4
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 4
- 229910052727 yttrium Inorganic materials 0.000 claims abstract description 4
- 229910052725 zinc Inorganic materials 0.000 claims abstract description 4
- 229910052726 zirconium Inorganic materials 0.000 claims abstract description 4
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 3
- 229910052787 antimony Inorganic materials 0.000 claims abstract description 3
- 238000005728 strengthening Methods 0.000 claims description 5
- 229910004247 CaCu Inorganic materials 0.000 claims description 3
- 230000003014 reinforcing effect Effects 0.000 claims description 3
- 229910052751 metal Inorganic materials 0.000 claims description 2
- 238000010438 heat treatment Methods 0.000 abstract description 8
- 239000000203 mixture Substances 0.000 abstract description 5
- 230000006866 deterioration Effects 0.000 abstract 1
- 230000002265 prevention Effects 0.000 abstract 1
- 230000002787 reinforcement Effects 0.000 abstract 1
- 238000000034 method Methods 0.000 description 18
- 239000007791 liquid phase Substances 0.000 description 9
- 239000000843 powder Substances 0.000 description 9
- 239000002994 raw material Substances 0.000 description 8
- 239000002245 particle Substances 0.000 description 5
- 238000007711 solidification Methods 0.000 description 5
- 238000002844 melting Methods 0.000 description 4
- 230000008018 melting Effects 0.000 description 4
- 230000008023 solidification Effects 0.000 description 4
- 229910002058 ternary alloy Inorganic materials 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 3
- 239000004020 conductor Substances 0.000 description 3
- 239000000470 constituent Substances 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 239000013078 crystal Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 238000005482 strain hardening Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000005491 wire drawing Methods 0.000 description 2
- 229910002480 Cu-O Inorganic materials 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 238000012856 packing Methods 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 229910002059 quaternary alloy Inorganic materials 0.000 description 1
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Classifications
-
- 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
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- Superconductors And Manufacturing Methods Therefor (AREA)
Abstract
Description
【0001】
【発明の属する技術分野】
本発明は酸化物超電体に係り、特に超電導マグネットや電力機器に使用される超電導特性に優れた銀シース法によるBi系酸化物超電導導体に関する。
【0002】
【従来の技術】
従来、酸化物超電導体として、Bi系(2212)酸化物超電導体(Bi:Sr:Ca:Cu=2:2:1:2のモル比)及びBi系(2223)酸化物超電導体(Bi:Sr:Ca:Cu=2:2:2:3のモル比)が線材化に成功しており、これらの線材は所謂銀シース法(Powderin Tube Method)によって製造されている。この方法は、銀又は銀合金パイプ内に超電導物質の原料粉末を充填し、これに縮径加工を施すか、あるいは更に圧延加工を施して断面丸形又はテープ状に成形した後、熱処理を施して原料粉末を超電導化するものである(例えば、非特許文献1参照。)。
【0003】
【非特許文献1】
T.Hasegawa et.al.“HTS Conductors for Magnets”,MT-17,Sep.2001,
Geneva.
この場合、原料粉末の充填密度を上げて加工及び熱処理後の組織を緻密化させ、超電導電流を寸断されることなく流すためには、線材1本当りの断面積に限界があり、この理由により、超電導電流は数十〜数百A/本程度に制限される。
【0004】
これを用いて実用的な電力機器や大型マグネットに使用する場合、これらの装置の仕様に合わせた容量の通電を行うことが必要であり、SMESや加速器等の大型機器ではその通電容量は数kA〜数十kAが必要とされるため、線材を撚合せることが必要となる。
【0005】
以上のように、実用化のためには線材の高いJc値(臨界電流密度)と高いJe値(臨界電流値/線材断面積)が必要であり、高いJe値を安定して得るためには、Ag比を下げフィラメントも細く均質なものにする必要がある。
【0006】
【発明が解決しようとする課題】
しかしながら、Bi系(2212)酸化物超電導体の場合、その成長過程は溶融〜凝固プロセスを用いることから、熱処理時に生成する液相がフィラメント間を隔てるマトリックスの銀又は銀合金壁を侵食する。さらに、液相から銀又は銀合金の粒界及び粒内を液相構成元素が拡散し、フィラメント内の元素の構成比を狂わせ、また凝固した超電導導体中に残留した余剰元素によって不純物結晶が析出し、超電導特性を低下させるという問題がある。
【0007】
さらに、銀又は銀合金内を拡散した液相構成元素は、粒界で結晶を析出させて粒界の接合強度を低下させ、粒界割れを引起す原因となるという問題があった。
【0008】
以上のような問題を解決するための手段として、当初の原料粉末中の元素のモル比を所望のモル比からずらし、液相から元素が拡散しても所望のモル比を有する超電導体が得られるようにする方法が採用されている。
【0009】
また、拡散距離を長くする目的で、フィラメント間を隔てるマトリックスの銀又は銀合金壁の厚さを厚くする試みもなされているが、銀量が増加してコストが上昇し、いずれも本質的な解決方法にはなっていない。
【0010】
本発明は以上の問題を解決するためになされたもので、溶融〜凝固プロセスを必要とするBi系(2212)酸化物超電導体において、所望の組成の超電導フィラメントを有し、超電導特性に優れるとともに、機械的強度にも優れたBi系酸化物超電導導体を提供することをその目的とする。
【0011】
【課題を解決するための手段】
以上の目的を達成するために、本発明によるBi系酸化物超電導体は、銀又は銀合金からなるマトリックス中に複数本のBi系酸化物超電導フィラメントを配置し、マトリックスの外側に銀合金シースを配置した超電導体において、銀合金シースを、AgにBi系酸化物超電導フィラメントを構成する金属元素のいずれか1種以上の元素からなる拡散防止用元素を添加した銀合金により形成することを特徴としている。
【0012】
また、本発明による他のBi系酸化物超電導体は、銀又は銀合金からなるマトリックス中に複数本のBi系酸化物超電導フィラメントを配置し、マトリックスの外側に銀合金シースを配置した超電導体において、銀合金シースを、Agに(Mg、Al、Sb、Zn、Zr、Y、Ni、Mn)から選択された少なくとも1種以上の強化用元素及び(Bi、Sr、Cu)から選択された少なくとも1種以上の拡散防止用元素を添加した銀合金により形成したことを特徴とするものである。
【0013】
以上の発明におけるBi系酸化物超電導体は銀シース法により製造されるが、特に溶融〜凝固プロセスを必要とするBi系(2212)酸化物超電導体に適し、この場合のBi系酸化物超電導フィラメントは、Bi:Sr:Ca:Cu=1.8〜2.5:1.8〜2.2:0.8〜1.2:1.6〜2.5のモル比を有するBi2Sr2CaCu2O8系超電導導体からなることが好ましい。
【0014】
また、本発明におけるBi系酸化物超電導体は、単線でも使用可能であるが、上述のように、大容量化の目的に対しては、これらの複数本を集合又は撚合せた集合導体として使用される。
【0015】
【発明の実施の形態】
本発明におけるBi系酸化物超電導体は銀シース法により製造されるが、銀シース法においては、銀又は銀合金パイプ内に超電導物質の原料粉末を充填し、これに縮径加工を施すか、あるいは更に圧延加工を施した後、熱処理が施される。この原料粉末としては、超電導物質を構成する元素を所定のモル比で含む仮焼粉末が使用され、Bi系(2212)酸化物超電導体の場合、その平均粒径が1〜5μm、最大粒径が20μmを超えないものが望ましい。この理由は、粒径が大きいとフィラメント中の超電導体密度が向上せず、フィラメント切れを生じ易くなるためである。
【0016】
マトリックス中のフィラメントの本数は、加工が可能な限り任意に選定することができる。しかしながら、その本数は線材の加工終了時にフィラメントの径で5〜20μmの範囲となるように設計することが望ましい。この理由は、フィラメントの径は超電導粒子の配向に影響を及ぼし、フィラメントの径が5μm未満であると熱処理時の反応が激しく不純物が生成し易くなり、一方、20μmを越えると超電導粒子が配向しなくなるためである。最終線材径は、撚線加工が可能である限り任意に選択することができる。
【0017】
本発明は、銀シース法によるBi系酸化物超電導体において、マトリックスの外側に配置される銀合金シースに、Agに拡散防止用元素又はこれに強化用元素を更に添加したものを使用するものであるが、拡散防止用元素としてはBi系酸化物超電導体を構成するBi、Sr、Cuから選択された少なくとも1種以上の元素が用いられ、一方、強化用元素としては、AgにMg、Al、Sb、Zn、Zr、Y、Ni、Mnから選択された少なくとも1種以上の元素が使用される。
【0018】
上記の強化用元素の添加量は、総量で0.02〜1wt%の範囲であることが好ましい。この理由は、添加量が総量で0.02wt%未満であると強化の効果がなく、一方、添加量が総量で1wt%を越えると伸びが極端に減少し、割れや断線を生じ易くなるためである。
【0019】
銀シース法によるBi系(2212)酸化物超電導体において、冷間加工後の熱処理過程で原料粉末は溶融して、主にBi、Sr、Cuで構成される液相とBi-(SrCa)-Oと(SrCa)-Cu-Oが生成する。このとき生成した液相からマトリックス及びシースである銀又は銀合金に向って超電導体構成元素のBi、Sr、Cuが拡散するが、シースに予めこの拡散元素を添加しておくことによって、拡散の駆動力となる濃度勾配を低下させあるいは濃度勾配をなくすことにより、液相からの元素の拡散を防ぐことができる。
【0020】
この拡散防止用元素の添加量は、総量で0.05〜2wt%の範囲であることが好ましい。この理由は、添加量が総量で0.05wt%未満であると液相からの元素の拡散を防ぐことができず、また添加量が総量で2wt%を越えると逆に超電導体に向って拡散を生じ超電導組織を乱し、超電導特性を低下させるためである。
【0021】
上記の冷間加工後の熱処理過程は、Bi系(2212)酸化物超電導体の融点以上まで昇温し、その凝固温度まで徐冷するプロセスを用いる。このときの冷却速度は、0.5〜10℃/hの範囲が望ましい。
【0022】
【実施例】
以下本発明の一実施例を図1に基づいて説明する。
【0023】
実施例1
外径φ18mm、内径φ15mmの純銀パイプ1中に、Bi2Sr2CaCu2O8の酸化物超電導体を構成する元素を所定のモル比で含む原料粉末2を充填し、これに伸線加工を施して外径φ2mmの線材3を製造した。この61本を束ねて同一サイズの純銀パイプ4中に収容し、更に伸線加工を施して外径φ1mmの線材5を製造した。
【0024】
次いで、この7本を束ねてAg−0.2wt%Mg−0.2wt%Cu三元合金を用いて作製したシース用パイプ6中に収容し、これに伸線加工を施してφ0.8mmまで成形した。
【0025】
このようにして製造した線材を所定の長さに切断し、酸素雰囲気中で最高温度900℃で3時間焼成した後、10℃/hの冷却速度で室温まで冷却してBi系酸化物超電導体を製造した。
【0026】
このようにして製造したBi系酸化物超電導体の臨界電流値(Ic)を4.2K、自己磁界下で測定した結果、900Aの値を示した。
【0027】
実施例2
シース用パイプとして、Ag−0.2wt%Mg−0.2wt%(Bi+Cu)四元合金を用いた他は、実施例1と同様にしてBi系酸化物超電導体を製造した。
【0028】
このようにして製造したBi系酸化物超電導体の臨界電流値(Ic)を4.2K、自己磁界下で測定した結果、1000Aの値を示した。
【0029】
実施例3
シース用パイプとして、Ag−0.2wt%Mg−0.2wt%Sr三元合金を用いた他は、実施例1と同様にしてBi系酸化物超電導体を製造した。
【0030】
このようにして製造したBi系酸化物超電導体の臨界電流値(Ic)を4.2K、自己磁界下で測定した結果、950Aの値を示した。
【0031】
比較例1
シース用パイプとして、純銀を用いた他は、実施例1と同様にしてBi系酸化物超電導体を製造した。
【0032】
このようにして製造したBi系酸化物超電導体の臨界電流値(Ic)を4.2K、自己磁界下で測定した結果、600Aの値を示した。
【0033】
比較例2
シース用パイプとして、Ag−0.2wt%Mg−7wt%Cu三元合金を用いた他は、実施例1と同様にしてBi系酸化物超電導体を製造した。
【0034】
このようにして製造したBi系酸化物超電導体の臨界電流値(Ic)を4.2K、自己磁界下で測定した結果、300Aの値を示した。
【0035】
比較例3
シース用パイプとして、Ag−0.2wt%Mg−10wt%Bi三元合金を用いた他は、実施例1と同様にしてBi系酸化物超電導体を製造した。
【0036】
このようにして製造したBi系酸化物超電導体の臨界電流値(Ic)を4.2K、自己磁界下で測定した結果、200Aの値を示した。
【0037】
【発明の効果】
以上述べたように、本発明によれば、マトリックスの外側に配置される銀合金シースに、Agに拡散防止用元素又はこれに強化用元素を添加したものを使用することにより、溶融〜凝固プロセスを必要とするBi系(2212)酸化物超電導体において、所望の組成の超電導フィラメントを有し、超電導特性に優れるとともに、機械的強度にも優れたBi系酸化物超電導体を製造することができる。
【図面の簡単な説明】
【図1】本発明によるBi系酸化物超電導体の製造方法の一実施例を示す概略図である。
【符号の説明】
1、4…純銀パイプ
2…原料粉末
3、5…線材
6…シース用パイプ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an oxide superconductor, and more particularly to a Bi-based oxide superconductor using a silver sheath method and having excellent superconducting properties used for superconducting magnets and power devices.
[0002]
[Prior art]
Conventionally, Bi-based (2212) oxide superconductor (Bi: Sr: Ca: Cu = 2: 2: 1: 2 molar ratio) and Bi-based (2223) oxide superconductor (Bi: Sr: Ca: Cu = 2: 2: 2: 3 molar ratio) has been successfully formed into a wire, and these wires are manufactured by a so-called silver sheath method (Powderin Tube Method). In this method, a silver or silver alloy pipe is filled with a raw material powder of a superconducting substance and subjected to diameter reduction processing or rolling processing to form a round or tape-shaped cross section, followed by heat treatment. Thus, the raw material powder is made superconductive (for example, see Non-Patent Document 1).
[0003]
[Non-patent document 1]
T. Hasegawa et.al. “HTS Conductors for Magnets”, MT-17, Sep. 2001,
Geneva.
In this case, in order to increase the packing density of the raw material powder to densify the structure after processing and heat treatment, and to flow the superconducting current without breaking, the cross-sectional area per wire is limited. The superconducting current is limited to several tens to several hundreds A / line.
[0004]
When this is used for practical power equipment and large magnets, it is necessary to energize the capacity according to the specifications of these devices, and for large equipment such as SMES and accelerators, the energization capacity is several kA. Since 〜10 kA is required, it is necessary to twist the wires.
[0005]
As described above, high Jc value (critical current density) and high Je value (critical current value / wire cross-sectional area) of a wire are necessary for practical use, and in order to stably obtain a high Je value, It is necessary to lower the Ag ratio and make the filament thin and uniform.
[0006]
[Problems to be solved by the invention]
However, in the case of the Bi-based (2212) oxide superconductor, since the growth process uses a melting to solidification process, the liquid phase generated during the heat treatment erodes the silver or silver alloy wall of the matrix separating the filaments. In addition, liquid phase constituent elements diffuse from the liquid phase to the grain boundaries of silver or silver alloy and inside the grains, causing the composition ratio of the elements in the filament to fluctuate, and impurity crystals being precipitated by the surplus elements remaining in the solidified superconductor. However, there is a problem that the superconducting characteristics are deteriorated.
[0007]
Further, there is a problem that the liquid phase constituent element diffused in silver or silver alloy precipitates crystals at the grain boundaries, lowers the bonding strength of the grain boundaries, and causes grain boundary cracking.
[0008]
As a means for solving the above problems, the molar ratio of the elements in the initial raw material powder is shifted from the desired molar ratio, and a superconductor having the desired molar ratio is obtained even if the elements diffuse from the liquid phase. A method is adopted to ensure that
[0009]
Attempts have also been made to increase the thickness of the silver or silver alloy wall of the matrix that separates the filaments in order to increase the diffusion distance, but the amount of silver increases and the cost increases, both of which are essential. Not a solution.
[0010]
The present invention has been made in order to solve the above problems, and in a Bi-based (2212) oxide superconductor requiring a melting to solidification process, a superconducting filament having a desired composition is provided, and the superconducting properties are excellent. It is another object of the present invention to provide a Bi-based oxide superconductor having excellent mechanical strength.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the Bi-based oxide superconductor according to the present invention has a structure in which a plurality of Bi-based oxide superconducting filaments are arranged in a matrix made of silver or a silver alloy, and a silver alloy sheath is provided outside the matrix. In the arranged superconductor, the silver alloy sheath is formed of a silver alloy in which Ag is added with a diffusion preventing element composed of at least one of metal elements constituting a Bi-based oxide superconducting filament. I have.
[0012]
Further, another Bi-based oxide superconductor according to the present invention is a superconductor in which a plurality of Bi-based oxide superconducting filaments are arranged in a matrix made of silver or a silver alloy, and a silver alloy sheath is arranged outside the matrix. , A silver alloy sheath, at least one or more reinforcing elements selected from Ag (Mg, Al, Sb, Zn, Zr, Y, Ni, Mn) and at least one selected from (Bi, Sr, Cu) It is characterized by being formed of a silver alloy to which one or more diffusion preventing elements are added.
[0013]
The Bi-based oxide superconductor in the above invention is manufactured by a silver sheath method, and is particularly suitable for a Bi-based (2212) oxide superconductor requiring a melting to solidification process. In this case, the Bi-based oxide superconducting filament is used. it is, Bi: Sr: Ca: Cu = 1.8~2.5: 1.8~2.2: 0.8~1.2: preferably consists of Bi 2 Sr 2 CaCu 2 O 8 type superconductor having a molar ratio of 1.6 to 2.5.
[0014]
In addition, the Bi-based oxide superconductor of the present invention can be used as a single wire, but as described above, for the purpose of increasing the capacity, a plurality of these are used as an aggregated conductor or as an aggregated conductor. Is done.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
The Bi-based oxide superconductor in the present invention is manufactured by a silver sheath method.In the silver sheath method, a raw material powder of a superconducting substance is filled in a silver or silver alloy pipe, and the diameter is reduced or Alternatively, heat treatment is performed after further rolling. As this raw material powder, a calcined powder containing the elements constituting the superconducting material in a predetermined molar ratio is used. In the case of a Bi-based (2212) oxide superconductor, the average particle size is 1 to 5 μm, and the maximum particle size is Is preferably not more than 20 μm. The reason for this is that if the particle size is large, the superconductor density in the filament does not increase, and the filament tends to break.
[0016]
The number of filaments in the matrix can be arbitrarily selected as much as possible. However, it is desirable to design the number of filaments to be in the range of 5 to 20 μm in the diameter of the filament at the end of processing the wire. The reason is that the diameter of the filament affects the orientation of the superconducting particles.If the diameter of the filament is less than 5 μm, the reaction at the time of heat treatment is severe and impurities are easily generated, while if it exceeds 20 μm, the superconducting particles are oriented. It is because it disappears. The final wire diameter can be arbitrarily selected as long as stranded processing is possible.
[0017]
The present invention uses a Bi-based oxide superconductor obtained by a silver sheath method, in which a silver alloy sheath disposed outside the matrix is obtained by further adding a diffusion preventing element or a strengthening element to Ag. However, as an element for preventing diffusion, at least one element selected from Bi, Sr, and Cu constituting a Bi-based oxide superconductor is used.On the other hand, as an element for strengthening, Ag, Mg, Al , Sb, Zn, Zr, Y, Ni, and Mn are used.
[0018]
It is preferable that the total amount of the above-mentioned reinforcing elements is in the range of 0.02 to 1 wt%. The reason is that if the total amount is less than 0.02% by weight, there is no strengthening effect, while if the total amount exceeds 1% by weight, the elongation is extremely reduced and cracks and breaks are liable to occur. is there.
[0019]
In Bi-based (2212) oxide superconductors by the silver sheath method, the raw material powder melts during the heat treatment process after cold working, and the liquid phase mainly composed of Bi, Sr, and Cu and Bi- (SrCa)- O and (SrCa) -Cu-O are generated. The superconductor constituent elements Bi, Sr, and Cu diffuse from the liquid phase generated toward the matrix and the silver or silver alloy as the sheath. Diffusion of elements from the liquid phase can be prevented by reducing or eliminating the concentration gradient serving as a driving force.
[0020]
The addition amount of the diffusion preventing element is preferably in the range of 0.05 to 2% by weight in total. The reason is that if the total amount of addition is less than 0.05 wt%, the diffusion of elements from the liquid phase cannot be prevented, and if the total amount exceeds 2 wt%, the diffusion toward the superconductor will be reversed. This is for disturbing the resulting superconducting structure and deteriorating the superconducting properties.
[0021]
In the heat treatment process after the cold working, a process of raising the temperature to a temperature equal to or higher than the melting point of the Bi-based (2212) oxide superconductor and gradually cooling to the solidification temperature is used. The cooling rate at this time is preferably in the range of 0.5 to 10 ° C / h.
[0022]
【Example】
Hereinafter, an embodiment of the present invention will be described with reference to FIG.
[0023]
Example 1
A raw silver powder 1 containing an element constituting the oxide superconductor of Bi 2 Sr 2 CaCu 2 O 8 at a predetermined molar ratio is filled in a pure silver pipe 1 having an outer diameter of φ18 mm and an inner diameter of φ15 mm. Thus, a wire 3 having an outer diameter of 2 mm was manufactured. The 61 wires were bundled and housed in a
[0024]
Next, these seven wires were bundled and housed in a sheath pipe 6 made of a ternary alloy of Ag-0.2wt% Mg-0.2wt% Cu, which was subjected to wire drawing and formed to φ0.8mm. .
[0025]
The wire thus manufactured is cut into a predetermined length, fired at a maximum temperature of 900 ° C. for 3 hours in an oxygen atmosphere, and then cooled to room temperature at a cooling rate of 10 ° C./h to obtain a Bi-based oxide superconductor. Was manufactured.
[0026]
The critical current value (Ic) of the Bi-based oxide superconductor thus manufactured was measured at 4.2 K under a self-magnetic field, and as a result, a value of 900 A was shown.
[0027]
Example 2
A Bi-based oxide superconductor was manufactured in the same manner as in Example 1 except that a quaternary alloy of Ag-0.2 wt% Mg-0.2 wt% (Bi + Cu) was used as the sheath pipe.
[0028]
The critical current value (Ic) of the Bi-based oxide superconductor thus manufactured was measured at 4.2 K under a self-magnetic field, and as a result, a value of 1000 A was shown.
[0029]
Example 3
A Bi-based oxide superconductor was manufactured in the same manner as in Example 1, except that a ternary alloy of Ag-0.2 wt% Mg-0.2 wt% Sr was used as a sheath pipe.
[0030]
The critical current value (Ic) of the Bi-based oxide superconductor thus manufactured was measured at 4.2 K under a self-magnetic field, and as a result, a value of 950 A was shown.
[0031]
Comparative Example 1
A Bi-based oxide superconductor was manufactured in the same manner as in Example 1, except that pure silver was used as the sheath pipe.
[0032]
The critical current value (Ic) of the Bi-based oxide superconductor thus manufactured was measured at 4.2 K under a self-magnetic field, and as a result, a value of 600 A was shown.
[0033]
Comparative Example 2
A Bi-based oxide superconductor was manufactured in the same manner as in Example 1 except that a ternary alloy of Ag-0.2 wt% Mg-7 wt% Cu was used as a sheath pipe.
[0034]
The critical current value (Ic) of the Bi-based oxide superconductor thus manufactured was measured at 4.2 K under a self-magnetic field, and as a result, a value of 300 A was shown.
[0035]
Comparative Example 3
A Bi-based oxide superconductor was manufactured in the same manner as in Example 1 except that a ternary alloy of Ag-0.2 wt% Mg-10 wt% Bi was used as a sheath pipe.
[0036]
The critical current value (Ic) of the Bi-based oxide superconductor thus manufactured was measured at 4.2 K under a self-magnetic field, and as a result, a value of 200 A was shown.
[0037]
【The invention's effect】
As described above, according to the present invention, the silver alloy sheath disposed outside the matrix, by using a diffusion preventing element or a strengthening element added to Ag, a melting-solidification process. A Bi-based (2212) oxide superconductor requiring a superconducting filament having a desired composition and having excellent superconducting characteristics and excellent mechanical strength can be manufactured. .
[Brief description of the drawings]
FIG. 1 is a schematic view showing one embodiment of a method for producing a Bi-based oxide superconductor according to the present invention.
[Explanation of symbols]
1,4 ... pure silver pipe 2 ...
Claims (5)
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