JP3717683B2

JP3717683B2 - Connection structure and connection method of oxide superconducting conductor

Info

Publication number: JP3717683B2
Application number: JP31026498A
Authority: JP
Inventors: 和憲尾鍋; 伸行定方; 隆斉藤; 重夫長屋
Original assignee: Fujikura Ltd; Chubu Electric Power Co Inc
Current assignee: Fujikura Ltd; Chubu Electric Power Co Inc
Priority date: 1998-10-30
Filing date: 1998-10-30
Publication date: 2005-11-16
Anticipated expiration: 2018-10-30
Also published as: JP2000133067A

Description

【０００１】
【発明の属する技術分野】
本発明は、超電導電力ケーブル、超電導マグネット、超電導エネルギー貯蔵装置、超電導発電装置、医療用ＭＲＩ装置、超電導電流リード等の分野で利用できる酸化物超電導導体の接続構造及び接続方法に関するものである。
【０００２】
【従来の技術】
近年、臨界温度（Ｔｃ）が液体窒素温度（約７７Ｋ）よりも高い酸化物超電導体として、例えば、Ｙ-Ｂａ-Ｃｕ-Ｏ系、Ｂｉ-Ｓｒ-Ｃａ-Ｃｕ-Ｏ系、Ｔｌ-Ｂａ-Ｃａ-Ｃｕ-Ｏ系などの酸化物超電導体が発見されている。
このような酸化物超電導体を有する酸化物超電導導体の製造方法の１つとして、化学気相蒸着法（ＣＶＤ法）等の薄膜形成手段によって基材表面に酸化物超電導薄膜を成膜する方法が知られている。この種の薄膜形成手段により形成した酸化物超電導薄膜は、臨界電流密度（Ｊｃ）が大きく、優れた超電導特性を発揮することが知られている。
【０００３】
ところで、上述のような製造方法により製造された酸化物超電導導体を実用機器に応用するには、酸化物超電導導体を接続する技術の開発が要望されており、従来の酸化物超電導導体の接続方法としては、特許第２６８８９２３号の酸化物超電導体の接合方法が知られている。この酸化物超電導体の接合方法では、真空排気した真空容器内に複数個の酸化物超電導体を互いに当接して配置し、これら酸化物超電導体を加熱し、その当接部に向けてノズルから上記酸化物超電導体と同じ材料の超微粉を噴出させ、上記当接部に上記超微粉を焼結させてこれら酸化物超電導体同士を接合している。
【０００４】
【発明が解決しようとする課題】
しかしながら従来の酸化物超電導導体の接続方法にあっては、二本の酸化物超電導導体の接合するために、これら酸化物超電導導体を再度ＣＶＤ反応用容器内に配置し、当接部上に接続用超電導薄膜を形成するための超微粉を堆積、焼結する工程を要するため、接続のための作業が煩雑になってしまう。また、従来の酸化物超電導導体の製造方法により得られた酸化物超電導導体の接合構造にあっては、酸化物超電導導体の当接部上に化学気相蒸着法により酸化物超電導薄膜を形成しただけのものであるので、種々の用途に用いるには安定性が不十分であり、また、接続部の強度が不十分であった。
【０００５】
本発明は上記事情に鑑みてなされたものであり、酸化物超電導導体の接続作業の簡略化が可能であり、安定性の向上と、接続部の強度の向上が可能な酸化物超電導導体の接続構造及び接続方法を提供することを目的とする。
【０００６】
【課題を解決するための手段】
本発明者は、酸化物超電導導体の接続作業の簡略化と、安定性の向上と、接続部の強度の向上を可能にすべく、種々の検討及び実験を重ねた結果、テープ状の基材上に酸化物超電導層が形成され、さらに該酸化物超電導層上に安定化銀層が形成されてなる複数本の酸化物超電導導体の上記安定化銀層側の表面を対向させ、これら安定化銀層同士を半田を介して接続すれば、上記課題を解決できるとの推定に至った。
しかしながら、この方法では、接続部の半田や安定化銀層などの金属層の抵抗および安定化銀層と酸化物超電導層の接触抵抗が、接続抵抗として発生するが、酸化物超電導層に銀を添加すると接触抵抗を低減でき、実用レベルの低抵抗接続を実現できることを究明し、本発明を完成したのである。
【０００７】
すなわち、請求項１記載の発明では、テープ状の基材上に銀が添加された酸化物超電導層が形成され、さらに該酸化物超電導層上に安定化銀層が形成されてなる複数本の酸化物超電導導体の前記安定化銀層側の表面を対向させ、これら安定化銀層同士が半田を介して接続されてなることを特徴とする酸化物超電導導体の接続構造を上記課題の解決手段とした。
【０００８】
また、本発明者らは、上記課題を解決すべく、種々の検討及び実験を重ねた結果、テープ状の基材上に酸化物超電導層が形成されてなる複数本の酸化物超電導導体をその端面同士を突き合わせ、該突き合わせ部上に、良導性金属からなる基材上に前記酸化物超電導層をなす材料より低融点の酸化物超電導材料からなる低融点酸化物超電導層が形成されてなる接続用超電導テープを配置し、該接続用超電導テープの低融点酸化物超電導層を溶融すれば、上記課題を解決できるとの推定に至った。
しかしながら、この方法では、酸化物超電導導体の接続部の強度において不満が残るため、さらに上記突き合わせ部を覆う接続用超電導テープ及びこれの両側の酸化物超電導導体上に安定化銀層を形成することにより、上記課題を解決できることを究明し、本発明を完成したのである。
【０００９】
すなわち、請求項２記載の発明では、テープ状の基材上に酸化物超電導層が形成されてなる複数本の酸化物超電導導体がその端面同士が突き合わせられ、該突き合わせ部が、良導性金属からなる基材上に前記酸化物超電導層をなす材料より低融点の酸化物超電導材料からなる低融点酸化物超電導層が形成されてなる接続用超電導テープで覆われ、前記複数本の酸化物超電導導体の突き合わせ部の両側が前記低融点酸化物超電導層で接続され、さらに該接続用超電導テープ及びこれの両側の酸化物超電導導体上に安定化銀層が形成されてなることを特徴とする酸化物超電導導体の接続構造を上記課題の解決手段とした。
【００１０】
また、請求項３記載の発明では、テープ状の基材上に酸化物超電導層が形成されてなる複数本の酸化物超電導導体をその端面同士を突き合わせ、該突き合わせ部上に、良導性金属からなる基材上に前記酸化物超電導層をなす材料より低融点の酸化物超電導材料からなる低融点酸化物超電導層が形成されてなる接続用超電導テープを、前記複数本の酸化物超電導体どうしを低融点酸化物超電導層を介して接するように配置し、該接続用超電導テープの低融点酸化物超電導層を溶融し、さらに該接続用超電導テープ及びこれの両側の酸化物超電導導体上に安定化銀層を形成することを特徴とする酸化物超電導導体の接続方法を上記課題の解決手段とした。
【００１１】
【発明の実施の形態】
以下、本発明の酸化物超電導導体の接続構造及び接続方法の一実施形態について図面を用いて説明する。
図１は、本発明の酸化物超電導導体の接続構造の第一の実施形態を示す断面図である。
第一の実施形態の酸化物超電導導体の接続構造は、複数本（図面では２本）の酸化物超電導導体１０の安定化銀層３側の表面３ａを対向させ、これら安定化銀層３同士が半田５を介して接続されてなるものである。
ここで用いられる酸化物超電導導体１０は、テープ状の基材１上に銀が添加された酸化物超電導層２が形成され、さらに該酸化物超電導層２上に安定化銀層３が形成されてなるものである。
【００１２】
テープ状の基材１としては、長尺のものを用いることができるが、特に、熱膨張係数の低い耐熱性の金属テープの上面にセラミックス製の多結晶中間層を被覆してなるものが好ましい。上記耐熱性の金属テープの構成材料としては、銀、白金、ステンレス鋼、銅、ハステロイ（Ｃ２７６等）などの金属材料や合金が好ましい。また、上記金属テープ以外では、各種ガラステープあるいはマイカテープなどの各種セラミックスなどからなるテープを用いても良い。次に、上記多結晶中間層を構成する材料は、熱膨張係数が金属よりも酸化物超電導体の熱膨張係数に近い、ＹＳＺ（イットリウム安定化ジルコニア）、ＳｒＴｉＯ₃、ＭｇＯ、Ａｌ₂Ｏ₃、ＬａＡｌＯ₃、ＬａＧａＯ₃、ＹＡｌＯ₃、ＺｒＯ₂などのセラミックスが好ましく、これらの中でもできる限り結晶配向性の整ったものを用いることが好ましい。
【００１３】
酸化物超電導層２をなす酸化物超電導体は、Ｙ−Ｂａ−Ｃｕ−Ｏ系の酸化物超電導体、Ａ−Ｂ−Ｃｕ−Ｏ系（ただし、ＡはＬa，Ｃe，Ｙ，Ｓc，Ｙbなどの周期律表IIIa族元素の１種以上を示し、ＢはＳr，Ｂaなどの周期律表IIa族元素の１種以上を示す）の酸化物超電導体などが用いられる。
上記銀の添加量は、酸化物超電導層２中に、５〜３０重量％添加されていることが好ましく、より好ましくは１０重量％添加されていることが好ましい。銀の添加量が５重量％未満であると、安定化銀層３と酸化物超電導層２の接触抵抗を十分低減できない。また、３０重量％を超えて添加してももはや効果の増大は期待できず、経済的にも不利となる。
【００１４】
図２は、第一の実施形態の酸化物超電導導体の接続構造に用いられる銀が添加された酸化物超電導層２を有する酸化物超電導導体１０の製造装置の概略構成を示す図である。
図２に示す製造装置を用いて、酸化物超電導導体１０を製造するには、まず、テープ状の基材１と上記酸化物超電導体を作製するための液体原料３４と、上記酸物超電導体に添加するための銀溶液８０を用意する。ここでの液体原料３４は、成膜するべき目的化合物の構成金属元素の有機金属錯体、金属アルコキシドなどの金属有機化合物を、目的化合物の組成比となるように複数種混合し、テトラヒドロフラン（ＴＨＦ）などの有機溶媒に溶解させたものを用いることができる。このような液体原料３４を用意したならば、収納容器４２に満たしておく。また、銀溶液８０としては、銀（ＤＰＭ）をテトラヒドロフラン（ＴＨＦ）などの有機溶媒に溶解させたものを用いることができる。このような銀溶液８０を用意したならば、収納容器８１に満たしておく。
【００１５】
上記のテープ状の基材１を用意したならば、これをＣＶＤ用反応チャンバ６１内に基材搬送機構７８により基材導入部６２から所定の移動速度で送り込むとともに基材搬送機構７５の巻取ドラム７４で巻き取り、更に反応生成室６３内の基材１を加熱ヒータ４７で所定の温度に加熱する。なお、基材１を送り込む前に、不活性ガス供給源６８から不活性ガスをパージガスとして反応チャンバ６１内に送り込み、同時に圧力調整装置７２を作動させて反応チャンバ６１の内部のガスを抜くことで反応チャンバ６１内の空気等の不用ガスを排除して内部を洗浄しておくことが好ましい。
【００１６】
基材１を反応チャンバ６１内に送り込んだならば、酸素ガス供給源６９から反応チャンバ６１内に酸素ガスを送り、更に、加圧源４３により収納容器４２から液体原料３４を接続管４１を経て加圧式液体ポンプ３５に送液し、該加圧式液体ポンプ３５により液体原料３４を毛細管３１ａ内に圧送し、これと同時にアトマイズガスをアトマイズガス供給部３２に送り込むとともにシールドガスをシールドガス供給部３３に送り込む。また、同時に圧力調整装置７２を作動させ反応チャンバ６１の内部のガスを排気する。この際、シールドガスの温度は、室温程度になるように調節しておく。また、気化器５０の内部温度が上記原料のうちの最も気化温度の高い原料の最適温度になるようにヒータ５１により調節しておく。ここで用いる毛細管３１ａは、予め毛細管挿入部３１に挿入しておく。
すると、液体原料３４は毛細管３１ａの先端に達し、この後、吐出口から吹き出る際、アトマイズガス供給部３２から流れてくるアトマイズガスにより直ちに霧化されるので、一定流量のミスト状の液体原料３４が気化器５０内に連続的に供給される。そして、気化器５０の内部に供給されたミスト状の液体原料３４は、ヒータ５１により加熱されて気化し、原料ガスとなり、さらにこの原料ガスは輸送管５３を介してガス拡散部６６に連続的に供給される。この時、輸送管５３の内部温度が上記原料のうちの最も気化温度の高い原料の最適温度になるように調節しておく。また、この時、酸素ガス供給源５４から酸素ガスを供給して原料ガス中に酸素を混合する操作も行う。
【００１７】
また、液体原料３４を毛細管３１ａ内に圧送するとともに、加圧源８２により収納容器８１から銀溶液８０を接続管８３を経て加圧式液体ポンプ８４に送液し、該加圧式液体ポンプ８４により銀溶液８０を銀溶液供給管８５内に圧送し、これと同時にアトマイズガスをアトマイズガス供給部８６に送り込むとともにシールドガスをシールドガス供給部８７に送り込む。すると、銀溶液８０は銀溶液供給管８５の先端に達し、この後、吐出口から吹き出る際、アトマイズガス供給部８６から流れてくるアトマイズガスにより直ちに霧化されるので、一定流量のミスト状の銀が気化器８９内に連続的に供給される。そして、気化器８９の内部に供給されたミスト状の銀原料は、ヒータ９０により加熱されて気化し、さらにこの気化した銀原料は輸送管８８、５３を経て上記ガス拡散部６６に連続的に供給される。この時、輸送管８８の内部温度が上記銀溶液の気化温度になるように調節しておく。
【００１８】
次に、反応チャンバ６１の内部においては、輸送管５３の出口部分からガス拡散部６６に出た原料ガスおよび銀原料が、ガス拡散部６６から拡散しながら反応生成室６３側に移動し、反応生成室６３の内部を通り、次いで基材１の近傍を移動してガス排気管７０に引き込まれるように移動する。
従って、加熱された基材１の上面側で原料ガスおよび銀原料を反応させて銀が添加された酸化物超電導薄膜を生成させることができる。
以上の成膜操作を所定時間継続して行なうことにより、銀が添加された酸化物超電導層２が基材１上に形成された酸化物超電導導体１０を得ることができる。
【００１９】
上述のようにして得られた酸化物超電導導体１０の複数本を接続して図１に示すような接続構造を得るには、例えば、一方の酸化物超電導導体１０の安定化銀層３の表面３ａの一端部に半田５を配置し、この半田５が配置された端部上に他方の酸化物超電導導体１０の安定化銀層３の表面３ａの一端部を重ね合わせて、安定化銀層３同士を半田５を介して接続すると、図１に示すような第一の実施形態の酸化物超電導導体の接続構造が得られる。
ここで一方の酸化物超電導導体１０と他方の酸化物超電導導体１０の接続部１５のラップ長Ｗとしては、目的とする接続部の強度によっても異なるが、０．４ｃｍ程度あればよく、好ましくは０．５ｃｍ程度以上とすることが好ましい。この接続部１５のラップ長Ｗは、０．５ｃｍ以上と大きくしても、酸化物超電導層と安定化銀層との接触抵抗を大幅に小さくすることができる。
【００２０】
第一の実施形態の酸化物超電導導体の接続構造にあっては、テープ状の基材１上に銀が添加された酸化物超電導層２が形成され、さらに該酸化物超電導層２上に安定化銀層３が形成されてなる複数本の酸化物超電導導体１０の安定化銀層３側の表面３ａを対向させ、これら安定化銀層３同士が半田５を介して接続されたものであるので、銀が添加された酸化物超電導層２と安定化銀層３との接触抵抗を十分低減でき、接続部１５における酸化物超電導層２と安定化銀層３との界面の抵抗が安定化銀層３や半田５などの金属層の抵抗と同じ程度の値となり、従って、接続部の抵抗を実用上問題のない程度まで低減でき、また、容易に長尺化が可能であり、安定性も確保できるので、用途を広げることができる。
【００２１】
また、銀が添加された酸化物超電導層２は、酸化物超電導体の原料ガスと別系統で銀原料を反応チャンバに供給することで、酸化物超電導体の形成時に銀を添加できるので、酸化物超電導導体を再度ＣＶＤ反応用容器内に配置して、当接部上に接続用超電導薄膜を形成するための微粉体を堆積、焼結する工程がなく、接続のための作業を簡略化できる。
また、第一の実施形態の酸化物超電導導体の接続構造にあっては、複数本の酸化物超電導導体１０の安定化銀層３側の表面３ａを対向させ、これら安定化銀層３同士が半田５を介して接続されたものであるので、酸化物超電導導体の当接部上に化学気相蒸着法により酸化物超電導薄膜を形成しただけの従来の酸化物超電導導体の接続構造に比べて、接続部の強度が優れる。
【００２２】
次に、本発明の酸化物超電導導体の接続構造の第二の実施形態について説明する。
図３は、第二の実施形態の酸化物超電導導体の接続構造を示す断面図である。第二の実施形態の酸化物超電導導体の接続構造は、複数本（図面では２本）の酸化物超電導導体２０がその端面２０ｂ同士が突き合わせられ、該突き合わせ部２９が、接続用超電導テープ２５で覆われ、接続され、さらに接続用超電導テープ２５及びこれの両側の酸化物超電導導体２０上に安定化銀層２８が形成されてなるものである。
ここで用いられる酸化物超電導導体２０は、上述のような耐熱性の金属テープ２２上に上述のようなセラミックス製の多結晶中間層２３を被覆してなるテープ状の基材２１上に酸化物超電導層２４が形成されてなるものである。この第二の実施形態においては、酸化物超電導層２４中には、銀は添加されていなくても良い。
【００２３】
接続用超電導テープ２５は、良導性金属からなる基材２６上に酸化物超電導層２４をなす材料より低融点の酸化物超電導材料からなる低融点酸化物超電導層２７が形成されてなるものである。
基材２６をなす良導性金属としては、配向銀やプラチナ等が好適に用いられる。ここでの配向銀は、結晶配向性が制御されたものであり、例えば、一方向溶融凝固法により、単結晶Ａｇロッドを作製し、目的とする配向面が露出するように切り出したものを用いることができる。また、Ａｇテープは、温度や圧下率等の圧延条件により、集合組織を形成することができ、単結晶からなるＡｇテープに近い機能を有することができるので、圧延したＡｇテープを用いてもよい。
【００２４】
酸化物超電導層２７をなす酸化物超電導材料が、酸化物超電導層２４をなす材料より融点が高いものであると、接続用超電導テープ２５に熱をかけて酸化物超電導層２７を溶融させたときに、酸化物超電導層２４が熱により劣化したり、あるいは溶融して超電導特性が低下するため好ましくない。
低融点酸化物超電導層２７をなす酸化物超電導材料は、酸化物超電導層２４をなす酸化物超電導材料よりも融点が約５０゜Ｃ程度低いものでもよいが、融点が１００゜Ｃ程度低いものであることが好ましい。
低融点酸化物超電導層２７をなす低融点の酸化物超電導材料の具体例としては、酸化物超電導層２４が融点が９８０〜１０００゜Ｃ程度のＹ₁Ｂａ₂Ｃｕ₃Ｏ_xなる組成（ｘ＝6.9）からなる場合、融点が８８０〜９００゜Ｃ程度のＹｂ₁Ｂａ₂Ｃｕ₃Ｏ_xなる組成（ｘ＝6.9）のものなどを用いることができる。
【００２５】
安定化銀層２８の厚みとしては、５〜１０μｍ程度とされる。安定化銀層２８の厚みが５μｍ以下であると、安定性が低下してしまい、１０μｍを超えて厚くしてももはや効果の増大は期待できず、経済的にも不利となる。
【００２６】
上述のような酸化物超電導導体２０の複数本を接続して、図３に示すような接続構造を得るには、複数本（図面では２本）の酸化物超電導導体２０をその端面２０ｂ同士を突き合わせ、該突き合わせ部２９上に、接続用超電導テープ２５を配置し、該接続用超電導テープ２５を低融点酸化物超電導層２７が溶融する温度で加熱し、さらに該接続用超電導テープ２５及びこれの両側の酸化物超電導導体２０上に安定化銀層２８をスパッタ法等の薄膜形成手段により形成すると、図３に示すような第二の実施形態の酸化物超電導導体の接続構造が得られる。
【００２７】
第二の実施形態の酸化物超電導導体の接続構造にあっては、複数本の酸化物超電導導体２０がその端面２０ｂ同士が突き合わせられ、該突き合わせ部２９が接続用超電導テープ２５で覆われ、接続され、さらに該接続用超電導テープ２５及びこれの両側の酸化物超電導導体２０上に安定化銀層２８が形成されてなるものであるので、容易に長尺化が可能であり、また、安定化銀層２８により安定性も確保できるので、用途を広げることができる。
【００２８】
また、酸化物超電導導体２０の突き合わせ部２９に接続用超電導テープ２５を配置し、該テープ２５の低融点酸化物超電導層２７を溶融するだけで、複数本の酸化物超電導導体２０を接続できるので、酸化物超電導導体を再度ＣＶＤ反応用容器内に配置して、当接部上に接続用超電導薄膜を形成するための微粉体を堆積、焼結する工程がなく、接続のための作業を簡略化できる。
また、第二の実施形態の酸化物超電導導体の接続構造にあっては、複数本の酸化物超電導導体２０の突き合わせ部２９が接続用超電導テープ２５で覆われ、さらに接続用超電導テープ２５及びこれの両側の酸化物超電導導体２０上に安定化銀層２８が形成されたものであるので、酸化物超電導導体の当接部上に化学気相蒸着法により酸化物超電導薄膜を形成しただけの従来の酸化物超電導導体の接続構造に比べて、接続部の強度が優れる。
なお、第二の実施形態の酸化物超電導導体の接続構造にあっては、突き合わせ部２９を覆う接続用超電導テープ２５及びこれの両側の酸化物超電導導体２０の上に安定化銀層２８が形成されている場合について説明したが、さらに、酸化物超電導導体２０の外側面や下面側まで延長して形成されていてもよい。
【００２９】
【実施例】
（実施例１）
２本の酸化物超電導導体を用意した。ここでの酸化物超電導導体としては、ハステロテープ上にイオンビームアシストスパッタリング法によりＹＳＺ（イットリウム安定化ジルコニア）面配向中間層を形成したテープ状の基材（幅１ｃｍ×長さ１０ｃｍ×厚さ０．０２ｃｍ）上に、銀が１０重量％添加された厚さ０．８μｍのＹ-Ｂａ-Ｃｕ-Ｏ系の酸化物超電導層が形成され、さらにこの上に厚さ６μｍの安定化銀層が形成されたものを用いた。
ついで、一方の酸化物超電導導体の安定化銀層の表面の一端部に半田を配置し、この半田が配置された端部上に他方の酸化物超電導導体の安定化銀層の表面の一端部を重ね合わせて、安定化銀層同士を半田を介して接続して、図１に示すような酸化物超電導導体の接続構造を得た。ここで一方の酸化物超電導導体と他方の酸化物超電導導体の接続部のラップ長は、０．５ｃｍであった。また、接続部の半田の厚みは、３８μｍであった。
【００３０】
（比較例１）
酸化物超電導層中に銀が添加されていない酸化物超電導導体を用いた以外は、実施例１と同様にして酸化物超電導導体の接続構造を得た。
【００３１】
実施例１ならびに比較例１で得られた酸化物超電導導体の接続構造を純酸素雰囲気中にて５００℃で２時間熱処理を施して測定試料とした。
そして、これら試料を液体窒素で７７Ｋに冷却し、各試料の比抵抗を測定した。その結果を下記表１に示す。また、これにより求められる金属層部分（半田層、安定化銀層）の抵抗値と、予備実験により測定した安定化銀層と酸化物超電導層の接触比抵抗による接続部の安定化銀層と酸化物超電導層の接触抵抗（安定化銀層と酸化物超電導層の界面の抵抗）の計算結果を下記表１に合わせて示す。
【００３２】
【表１】

【００３３】
表１中、＊１、＊２は、接続部の安定化銀と酸化物超電導層との接触比抵抗であり、＊３、＊４は、接続部の安定化銀と酸化物超電導層の界面の抵抗である。上記表１に示す結果から明らかなように、比較例１の接続構造は、接続部における酸化物超電導層と安定化銀層との界面の抵抗が1.1×10^-6ohmであり、安定化銀層や半田などの金属層の抵抗に比べて２桁以上大きいことがわかる。これに対して実施例１の接続構造によれば、銀が添加された酸化物超電導層と安定化銀層との接触抵抗を十分低減でき、接続部における酸化物超電導層と安定化銀層との界面の抵抗が4.4×10^-8ohmであり、安定化銀層や半田などの金属層の抵抗と同じ程度の値となることがわかる。
また、上記測定値より計算した比較例１の接続部のトータルの接続抵抗は、１．１×１０^-6Ωであり、これに対して実施例１の接続部のトータルの接続構造は、６．９×１０^-8Ωであり、接続部の抵抗を実用上問題のない程度まで低減できることがわかる。
なお、上記実施例では、ラップ長が０．５ｃｍとしたが、これを１００倍の長さとしても、接続部の接続抵抗を従来の約１／１００とすることができることを確認した。
【００３４】
また、Ｙ-Ｂａ-Ｃｕ-Ｏ系の酸化物超電導層に添加する銀の添加量を０重量％〜３０重量％の範囲で変更した以外は、上記実施例１と同様にして作製した酸化物超電導導体の接続構造についても、酸化物超電導層と安定化銀層との接触抵抗について調べたところ、銀の添加量を１０重量％以上３０重量％以下の範囲としたものについては、実施例１のものと大差なく、酸化物超電導層と安定化銀層との接触抵抗を十分低減でき、接続部における酸化物超電導層と安定化銀層との界面の抵抗も実施例１のものとほぼ同様であり、安定化銀層や半田などの金属層の抵抗と同じ程度の値となることがわかった。また、銀の添加量を５重量％以上〜１０重量％未満としたものについては、銀の添加量が変化すると、酸化物超電導層と安定化銀層との接触抵抗も変化するが、酸化物超電導層と安定化銀層との接触抵抗を十分低減できており、接続部の抵抗を実用上問題のない程度まで低減できることがわかった。また、銀の添加量を５重量％未満としたものについては、酸化物超電導層と安定化銀層との接触抵抗を十分低減できず、実用上問題が生じる恐れがあることがわかった。
【００３５】
【発明の効果】
以上説明したように請求項１記載の酸化物超電導導体の接続構造にあっては、上述の構成としたことにより、銀が添加された酸化物超電導層と安定化銀層との接触抵抗を十分低減でき、接続部における酸化物超電導層と安定化銀層との界面の抵抗が安定化銀層や半田などの金属層の抵抗と同じ程度の値となり、従って、接続部の抵抗を実用上問題のない程度まで低減でき、また、容易に長尺化が可能であり、安定性も確保できるので、用途を広げることができる。また、上記銀が添加された酸化物超電導層は、酸化物超電導体の原料ガスと別系統で銀原料を反応チャンバに供給することで、酸化物超電導体の形成時に銀を添加できるので、酸化物超電導導体を再度ＣＶＤ反応用容器内に配置して、当接部上に接続用超電導薄膜を形成するための微粉体を堆積、焼結する工程がなく、接続のための作業を簡略化できる。
また、請求項１記載の酸化物超電導導体の接続構造にあっては、複数本の酸化物超電導導体の安定化銀層側の表面を対向させ、これら安定化銀層同士が半田を介して接続されたものであるので、酸化物超電導導体の当接部上に化学気相蒸着法により酸化物超電導薄膜を形成しただけの従来の酸化物超電導導体の接続構造に比べて、接続部の強度が優れる。
【００３６】
請求項２記載の酸化物超電導導体の接続構造にあっては、上述の構成としたことにより、容易に長尺化が可能であり、また、安定化銀層により安定性も確保できるので、用途を広げることができる。また、酸化物超電導導体の突き合わせ部に接続用超電導テープを配置し、該テープの低融点酸化物超電導層を溶融するだけで、複数本の酸化物超電導導体どうしを低融点酸化物超電導層を介して接続できるので、酸化物超電導導体を再度ＣＶＤ反応用容器内に配置して、当接部上に接続用超電導薄膜を形成するための微粉体を堆積、焼結する工程がなく、接続のための作業を簡略化できる。
また、請求項２記載の酸化物超電導導体の接続構造にあっては、複数本の酸化物超電導導体の突き合わせ部が接続用超電導テープで覆われ、複数本の酸化物超電導体どうしが低融点酸化物超電導層で接続され、さらに接続用超電導テープ及びこれの両側の酸化物超電導導体上に安定化銀層が形成されたものであるので、酸化物超電導導体の当接部上に化学気相蒸着法により酸化物超電導薄膜を形成しただけの従来の酸化物超電導導体の接続構造に比べて、接続部の強度が優れる。
請求項３記載の酸化物超電導導体の接続方法にあっては、上述の構成としたことにより、接続のための作業が煩雑になることがなく、請求項２記載の酸化物超電導導体の接続構造を得ることができる。
【図面の簡単な説明】
【図１】本発明の酸化物超電導導体の接続構造の第一の実施形態を示す断面図である。
【図２】第一の実施形態の酸化物超電導導体の接続構造に用いられる酸化物超電導導体の製造装置の概略構成を示す図である。
【図３】本発明の酸化物超電導導体の接続構造の第二の実施形態を示す断面図である。
【符号の説明】
１・・・テープ状の基材、２・・・銀が添加された酸化物超電導層、３・・・安定化銀層、３ａ・・・表面、５・・・半田、１０・・・酸化物超電導導体、１５・・・接続部、２０・・・酸化物超電導導体、２０ｂ・・・端面、２１・・・テープ状の基材、２４・・・酸化物超電導層、２５・・・接続用超電導テープ、２６・・・基材、２７・・・低融点酸化物超電導層、２８・・・安定化銀層、２９・・・突き合わせ部、Ｗ・・・ラップ長。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a connection structure and a connection method for oxide superconducting conductors that can be used in the fields of superconducting power cables, superconducting magnets, superconducting energy storage devices, superconducting power generation devices, medical MRI devices, superconducting current leads, and the like.
[0002]
[Prior art]
In recent years, oxide superconductors having a critical temperature (Tc) higher than the liquid nitrogen temperature (about 77 K) include, for example, Y—Ba—Cu—O, Bi—Sr—Ca—Cu—O, and Tl—Ba—. An oxide superconductor such as a Ca—Cu—O system has been discovered.
As one method for producing an oxide superconductor having such an oxide superconductor, there is a method of forming an oxide superconducting thin film on the surface of a substrate by thin film forming means such as chemical vapor deposition (CVD). Are known. It is known that an oxide superconducting thin film formed by this type of thin film forming means has a large critical current density (Jc) and exhibits excellent superconducting properties.
[0003]
By the way, in order to apply the oxide superconducting conductor manufactured by the above-described manufacturing method to a practical device, development of a technique for connecting the oxide superconducting conductor is demanded, and the conventional connecting method of the oxide superconducting conductor is required. As such, a method for joining oxide superconductors disclosed in Japanese Patent No. 2688923 is known. In this method of joining oxide superconductors, a plurality of oxide superconductors are disposed in contact with each other in a vacuum evacuated vacuum vessel, and these oxide superconductors are heated and directed from the nozzle toward the contact portion. Ultrafine powder of the same material as that of the oxide superconductor is ejected, and the ultrafine powder is sintered at the contact portion to join the oxide superconductors.
[0004]
[Problems to be solved by the invention]
However, in the conventional connection method of oxide superconductors, in order to join two oxide superconductors, these oxide superconductors are again placed in the CVD reaction vessel and connected on the contact part. Since a process of depositing and sintering ultrafine powder for forming the superconducting thin film for use is required, the connection work becomes complicated. In addition, in the junction structure of the oxide superconducting conductor obtained by the conventional manufacturing method of the oxide superconducting conductor, an oxide superconducting thin film was formed on the contact portion of the oxide superconducting conductor by a chemical vapor deposition method. Therefore, the stability was insufficient for use in various applications, and the strength of the connecting portion was insufficient.
[0005]
The present invention has been made in view of the above circumstances, and it is possible to simplify the connection work of the oxide superconductor, and to improve the stability and to improve the strength of the connecting portion. An object is to provide a structure and a connection method.
[0006]
[Means for Solving the Problems]
The present inventor has conducted various studies and experiments in order to simplify the connection work of the oxide superconducting conductor, improve stability, and improve the strength of the connection portion. An oxide superconducting layer is formed on the surface of the oxide superconducting layer, and a stabilized silver layer is formed on the oxide superconducting layer. It has been estimated that the above problem can be solved by connecting the silver layers via solder.
However, in this method, the resistance of the metal layer such as the solder of the connecting portion and the stabilized silver layer and the contact resistance between the stabilized silver layer and the oxide superconducting layer are generated as the connecting resistance, but silver is added to the oxide superconducting layer. The inventors have investigated that the addition can reduce the contact resistance and realize a low-resistance connection at a practical level, thus completing the present invention.
[0007]
That is, in the invention according to claim 1, a plurality of oxide superconducting layers to which silver is added are formed on a tape-like substrate, and a stabilized silver layer is further formed on the oxide superconducting layer. The oxide superconducting conductor connecting structure characterized in that the surface of the oxide superconducting conductor on the side of the stabilized silver layer is opposed and the stabilized silver layers are connected to each other via solder. It was.
[0008]
In addition, the present inventors have conducted various studies and experiments in order to solve the above problems, and as a result, a plurality of oxide superconducting conductors in which an oxide superconducting layer is formed on a tape-like substrate are obtained. The end faces are butted together, and a low melting point oxide superconducting layer made of an oxide superconducting material having a melting point lower than that of the material forming the oxide superconducting layer is formed on the base made of a highly conductive metal. It has been estimated that the above problem can be solved by disposing a connecting superconducting tape and melting the low melting point oxide superconducting layer of the connecting superconducting tape.
However, in this method, since the dissatisfaction remains in the strength of the connecting portion of the oxide superconducting conductor, a stabilizing silver layer is further formed on the connecting superconducting tape covering the butted portion and the oxide superconducting conductor on both sides thereof. Thus, the inventors have found out that the above problems can be solved and completed the present invention.
[0009]
That is, in the invention according to claim 2, the end surfaces of a plurality of oxide superconducting conductors in which an oxide superconducting layer is formed on a tape-like base material are butted, and the butted portion is a highly conductive metal. Covered with a superconducting tape for connection in which a low melting point oxide superconducting layer made of an oxide superconducting material having a lower melting point than the material forming the oxide superconducting layer is formed on a base material made of Both sides of the butt portion of the plurality of oxide superconducting conductors are the low melting point oxide superconducting layers. The oxide superconducting conductor connection structure is characterized in that a stabilized silver layer is formed on the connecting superconducting tape and the oxide superconducting conductors on both sides of the connecting superconducting tape.
[0010]
According to a third aspect of the present invention, the end surfaces of a plurality of oxide superconducting conductors each having an oxide superconducting layer formed on a tape-like base material are butted together, and a highly conductive metal is formed on the butted portion. A superconducting tape for connection, in which a low-melting point oxide superconducting layer made of an oxide superconducting material having a lower melting point than a material forming the oxide superconducting layer is formed on a base material made of The plurality of oxide superconductors are in contact with each other via a low melting point oxide superconducting layer. An oxide comprising: disposing and melting the low melting point oxide superconducting layer of the connecting superconducting tape, and further forming a stabilizing silver layer on the connecting superconducting tape and the oxide superconducting conductors on both sides thereof The superconducting conductor connection method was used as a means for solving the above problems.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a connection structure and a connection method of an oxide superconducting conductor of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing a first embodiment of the connection structure of the oxide superconducting conductor of the present invention.
The connection structure of the oxide superconducting conductors of the first embodiment is such that the surfaces 3a on the stabilized silver layer 3 side of a plurality (two in the drawing) of the oxide superconducting conductors 10 face each other, and these stabilized silver layers 3 are connected to each other. Are connected via the solder 5.
The oxide superconducting conductor 10 used here has an oxide superconducting layer 2 in which silver is added on a tape-like substrate 1, and a stabilized silver layer 3 is further formed on the oxide superconducting layer 2. It will be.
[0012]
As the tape-shaped substrate 1, a long one can be used, and in particular, a material obtained by coating a ceramic intermediate layer on the upper surface of a heat-resistant metal tape having a low thermal expansion coefficient is preferable. . As a constituent material of the heat-resistant metal tape, metal materials such as silver, platinum, stainless steel, copper, Hastelloy (C276, etc.) and alloys are preferable. In addition to the metal tape, a tape made of various ceramics such as various glass tapes or mica tapes may be used. Next, the material constituting the polycrystalline intermediate layer is composed of YSZ (yttrium stabilized zirconia), SrTiO, whose thermal expansion coefficient is closer to that of the oxide superconductor than metal. _Three , MgO, Al ₂ O _Three LaAlO _Three LaGaO _Three YAlO _Three , ZrO ₂ Ceramics such as these are preferable, and among these, it is preferable to use a material having as much crystal orientation as possible.
[0013]
The oxide superconductor forming the oxide superconducting layer 2 is a Y-Ba-Cu-O-based oxide superconductor, AB-Cu-O-based (where A is La, Ce, Y, Sc, Yb, etc.) In this case, one or more of group IIIa elements of the periodic table in the periodic table, and B represents one or more group IIa elements of the periodic table of Sr, Ba, etc.) are used.
The amount of silver added is preferably 5 to 30% by weight, more preferably 10% by weight, in the oxide superconducting layer 2. When the addition amount of silver is less than 5% by weight, the contact resistance between the stabilized silver layer 3 and the oxide superconducting layer 2 cannot be sufficiently reduced. Moreover, even if added over 30% by weight, an increase in the effect can no longer be expected, which is disadvantageous economically.
[0014]
FIG. 2 is a diagram illustrating a schematic configuration of an apparatus for manufacturing an oxide superconducting conductor 10 having an oxide superconducting layer 2 to which silver is added, which is used in the connection structure of the oxide superconducting conductor according to the first embodiment.
In order to manufacture the oxide superconductor 10 using the manufacturing apparatus shown in FIG. 2, first, the tape-shaped substrate 1, the liquid raw material 34 for manufacturing the oxide superconductor, and the acid superconductor A silver solution 80 to be added to is prepared. The liquid raw material 34 used here is a mixture of a plurality of metal organic compounds such as an organometallic complex of a constituent metal element of a target compound to be formed into a film and a metal alkoxide so as to have a composition ratio of the target compound, and tetrahydrofuran (THF). What was melt | dissolved in organic solvents, such as, can be used. When such a liquid raw material 34 is prepared, the storage container 42 is filled. Moreover, as the silver solution 80, what melt | dissolved silver (DPM) in organic solvents, such as tetrahydrofuran (THF), can be used. When such a silver solution 80 is prepared, the storage container 81 is filled.
[0015]
When the tape-like base material 1 is prepared, it is fed into the CVD reaction chamber 61 from the base material introduction section 62 by the base material transport mechanism 78 at a predetermined moving speed, and the base material transport mechanism 75 is wound up. The drum 74 is wound up, and the substrate 1 in the reaction generation chamber 63 is further heated to a predetermined temperature by the heater 47. Before feeding the base material 1, the inert gas is fed from the inert gas supply source 68 into the reaction chamber 61 as a purge gas, and at the same time, the pressure regulator 72 is operated to exhaust the gas inside the reaction chamber 61. It is preferable to clean the inside by eliminating unnecessary gas such as air in the reaction chamber 61.
[0016]
When the substrate 1 is sent into the reaction chamber 61, oxygen gas is sent from the oxygen gas supply source 69 into the reaction chamber 61, and further, the liquid source 34 is supplied from the storage container 42 by the pressurizing source 43 through the connection pipe 41. Liquid is fed to the pressurized liquid pump 35, and the liquid raw material 34 is pumped into the capillary tube 31a by the pressurized liquid pump 35. At the same time, the atomized gas is fed to the atomized gas supply unit 32 and the shield gas is fed to the shield gas supply unit 33. To send. At the same time, the pressure adjusting device 72 is operated to exhaust the gas inside the reaction chamber 61. At this time, the temperature of the shielding gas is adjusted to be about room temperature. Further, the heater 51 is adjusted so that the internal temperature of the vaporizer 50 becomes the optimum temperature of the raw material having the highest vaporization temperature among the raw materials. The capillary tube 31a used here is inserted in the capillary tube insertion portion 31 in advance.
Then, the liquid raw material 34 reaches the tip of the capillary tube 31a, and thereafter, when it is blown out from the discharge port, it is immediately atomized by the atomizing gas flowing from the atomizing gas supply section 32, so that the mist-like liquid raw material 34 having a constant flow rate is obtained. Is continuously fed into the vaporizer 50. The mist-like liquid material 34 supplied to the inside of the vaporizer 50 is heated and vaporized by the heater 51 to become a raw material gas, and this raw material gas is continuously supplied to the gas diffusion section 66 through the transport pipe 53. To be supplied. At this time, the internal temperature of the transport pipe 53 is adjusted to be the optimum temperature of the raw material having the highest vaporization temperature among the raw materials. At this time, an operation of supplying oxygen gas from the oxygen gas supply source 54 and mixing oxygen into the raw material gas is also performed.
[0017]
Further, the liquid raw material 34 is pumped into the capillary tube 31 a, and the silver solution 80 is fed from the storage container 81 through the connecting pipe 83 to the pressurizing liquid pump 84 by the pressurizing source 82, and the pressurizing liquid pump 84 supplies the silver solution 80. The solution 80 is pumped into the silver solution supply pipe 85, and at the same time, the atomizing gas is sent to the atomizing gas supply unit 86 and the shielding gas is sent to the shielding gas supply unit 87. Then, the silver solution 80 reaches the tip of the silver solution supply pipe 85, and thereafter, when it is blown out from the discharge port, it is immediately atomized by the atomizing gas flowing from the atomizing gas supply unit 86. Silver is continuously fed into the vaporizer 89. The mist-like silver raw material supplied to the inside of the vaporizer 89 is heated and vaporized by the heater 90, and the vaporized silver raw material is continuously supplied to the gas diffusion section 66 through the

transport pipes

88 and 53. Supplied. At this time, the internal temperature of the transport pipe 88 is adjusted to the vaporization temperature of the silver solution.
[0018]
Next, in the reaction chamber 61, the raw material gas and the silver raw material that have come out from the outlet portion of the transport pipe 53 to the gas diffusion portion 66 move to the reaction generation chamber 63 side while diffusing from the gas diffusion portion 66, and the reaction It passes through the inside of the generation chamber 63 and then moves in the vicinity of the base material 1 so as to be drawn into the gas exhaust pipe 70.
Therefore, the oxide superconducting thin film to which silver is added can be generated by reacting the raw material gas and the silver raw material on the upper surface side of the heated substrate 1.
The oxide superconducting conductor 10 in which the oxide superconducting layer 2 to which silver is added is formed on the substrate 1 can be obtained by continuously performing the above film forming operation for a predetermined time.
[0019]
In order to obtain a connection structure as shown in FIG. 1 by connecting a plurality of oxide superconductors 10 obtained as described above, for example, the surface of the stabilized silver layer 3 of one oxide superconductor 10 is used. Solder 5 is arranged at one end of 3a, and one end of surface 3a of stabilized silver layer 3 of the other oxide superconducting conductor 10 is superposed on the end where solder 5 is arranged, thereby stabilizing silver layer. When the three are connected via the solder 5, the connection structure of the oxide superconducting conductor of the first embodiment as shown in FIG. 1 is obtained.
Here, the wrap length W of the connecting portion 15 between the one oxide superconducting conductor 10 and the other oxide superconducting conductor 10 varies depending on the strength of the intended connecting portion, but may be about 0.4 cm, preferably It is preferably about 0.5 cm or more. Even if the wrap length W of the connecting portion 15 is increased to 0.5 cm or more, the contact resistance between the oxide superconducting layer and the stabilized silver layer can be significantly reduced.
[0020]
In the connection structure of the oxide superconducting conductor of the first embodiment, the oxide superconducting layer 2 to which silver is added is formed on the tape-like base material 1, and the oxide superconducting layer 2 is further stabilized. The surface 3a on the side of the stabilized silver layer 3 of the plurality of oxide superconducting conductors 10 formed with the silver halide layer 3 is opposed to each other, and the stabilized silver layers 3 are connected to each other through the solder 5. Therefore, the contact resistance between the oxide superconducting layer 2 to which silver is added and the stabilized silver layer 3 can be sufficiently reduced, and the resistance at the interface between the oxide superconducting layer 2 and the stabilized silver layer 3 in the connection portion 15 is stabilized. It has the same value as the resistance of the metal layer such as the silver layer 3 or the solder 5, so that the resistance of the connecting portion can be reduced to a level that does not cause a practical problem, and the length can be easily increased, and the stability. Can be secured, so the application can be expanded.
[0021]
In addition, the oxide superconducting layer 2 to which silver is added can be added with silver at the time of forming the oxide superconductor by supplying the silver source to the reaction chamber separately from the source gas of the oxide superconductor. The superconducting conductor is placed in the CVD reaction vessel again, and there is no process of depositing and sintering fine powder for forming a superconducting thin film for connection on the contact portion, thus simplifying the connection work. .
In the oxide superconducting conductor connection structure of the first embodiment, the surfaces 3a of the plurality of oxide superconducting conductors 10 on the stabilized silver layer 3 side are opposed to each other, and the stabilized silver layers 3 are connected to each other. Since it is connected via the solder 5, compared to the conventional oxide superconducting conductor connection structure in which the oxide superconducting thin film is formed on the contact portion of the oxide superconducting conductor by chemical vapor deposition. , The strength of the connecting portion is excellent.
[0022]
Next, a second embodiment of the oxide superconducting conductor connection structure of the present invention will be described.
FIG. 3 is a cross-sectional view showing the connection structure of the oxide superconducting conductor of the second embodiment. The connection structure of the oxide superconducting conductor according to the second embodiment is such that a plurality of (two in the drawing) oxide superconducting conductors 20 abut each other at their end faces 20b, and the abutting portion 29 is a connecting superconducting tape 25. The stabilized silver layer 28 is formed on the connecting superconducting tape 25 and the oxide superconducting conductors 20 on both sides thereof.
The oxide superconducting conductor 20 used here is an oxide on a tape-like base material 21 formed by coating the above-described ceramic intermediate layer 23 on the heat-resistant metal tape 22 as described above. A superconducting layer 24 is formed. In the second embodiment, silver may not be added to the oxide superconducting layer 24.
[0023]
The connecting superconducting tape 25 is formed by forming a low melting point oxide superconducting layer 27 made of an oxide superconducting material having a lower melting point than the material forming the oxide superconducting layer 24 on a base material 26 made of a highly conductive metal. is there.
As the highly conductive metal forming the substrate 26, oriented silver, platinum or the like is preferably used. The oriented silver used herein is one whose crystal orientation is controlled. For example, a single crystal Ag rod is prepared by a unidirectional melt solidification method and is cut out so that the intended orientation plane is exposed. be able to. Further, Ag tape can form a texture according to rolling conditions such as temperature and rolling reduction, and can have a function close to that of a single crystal Ag tape. Therefore, a rolled Ag tape may be used. .
[0024]
When the oxide superconducting material forming the oxide superconducting layer 27 has a melting point higher than that of the material forming the oxide superconducting layer 24, the connecting superconducting tape 25 is heated to melt the oxide superconducting layer 27. In addition, the oxide superconducting layer 24 is not preferable because it deteriorates due to heat or melts to lower the superconducting characteristics.
The oxide superconducting material forming the low melting point oxide superconducting layer 27 may have a melting point lower by about 50 ° C. than the oxide superconducting material forming the oxide superconducting layer 24, but the melting point is about 100 ° C. lower. Preferably there is.
As a specific example of the low melting point oxide superconducting material forming the low melting point oxide superconducting layer 27, the oxide superconducting layer 24 has a melting point of about 980 to 1000 ° C. ₁ Ba ₂ Cu _Three O _x Yb having a melting point of about 880 to 900 ° C. ₁ Ba ₂ Cu _Three O _x A composition having a composition (x = 6.9) or the like can be used.
[0025]
The thickness of the stabilized silver layer 28 is about 5 to 10 μm. When the thickness of the stabilized silver layer 28 is 5 μm or less, the stability is lowered, and even if the thickness exceeds 10 μm, an increase in the effect can no longer be expected, which is economically disadvantageous.
[0026]
In order to obtain a connection structure as shown in FIG. 3 by connecting a plurality of oxide superconducting conductors 20 as described above, a plurality of (two in the drawing) oxide superconducting conductors 20 are connected to the end surfaces 20b. The connecting superconducting tape 25 is disposed on the butting portion 29, the connecting superconducting tape 25 is heated at a temperature at which the low melting point oxide superconducting layer 27 melts, and the connecting superconducting tape 25 and When the stabilized silver layer 28 is formed on the oxide superconducting conductors 20 on both sides by thin film forming means such as sputtering, the connection structure of the oxide superconducting conductor of the second embodiment as shown in FIG. 3 is obtained.
[0027]
In the connection structure of the oxide superconducting conductor of the second embodiment, the end surfaces 20b of the plurality of oxide superconducting conductors 20 are butted against each other, and the butted portion 29 is covered with the superconducting tape 25 for connection. Further, since the stabilizing silver layer 28 is formed on the connecting superconducting tape 25 and the oxide superconducting conductors 20 on both sides thereof, the length can be easily increased and the stabilization can be achieved. Since the silver layer 28 can ensure stability, the use can be expanded.
[0028]
In addition, since the superconducting tape 25 for connection is disposed at the butt portion 29 of the oxide superconducting conductor 20 and the low melting point oxide superconducting layer 27 of the tape 25 is melted, a plurality of oxide superconducting conductors 20 can be connected. The superconducting oxide conductor is placed in the CVD reaction vessel again, and there is no process of depositing and sintering fine powder to form a superconducting thin film for connection on the abutment, simplifying the connection work Can be
In the oxide superconducting conductor connection structure of the second embodiment, the butted portions 29 of the plurality of oxide superconducting conductors 20 are covered with the connecting superconducting tape 25, and the connecting superconducting tape 25 and this Since the stabilized silver layer 28 is formed on the oxide superconducting conductor 20 on both sides of the oxide superconducting conductor, a conventional oxide superconducting thin film is simply formed by chemical vapor deposition on the contact portion of the oxide superconducting conductor. Compared with the connection structure of the oxide superconducting conductor, the strength of the connecting portion is excellent.
In the oxide superconducting conductor connection structure of the second embodiment, the stabilizing silver layer 28 is formed on the connecting superconducting tape 25 covering the butt 29 and the oxide superconducting conductors 20 on both sides thereof. However, the oxide superconducting conductor 20 may be formed so as to extend to the outer surface or the lower surface side.
[0029]
【Example】
(Example 1)
Two oxide superconducting conductors were prepared. The oxide superconducting conductor here is a tape-shaped substrate (width 1 cm × length 10 cm × thickness 0. 0 mm) in which a YSZ (yttrium stabilized zirconia) plane oriented intermediate layer is formed on a hastelo tape by ion beam assisted sputtering. On the other hand, a 0.8 μm thick Y—Ba—Cu—O-based oxide superconducting layer to which 10% by weight of silver is added is formed, and a 6 μm thick stabilized silver layer is further formed thereon. What was done was used.
Next, solder is placed on one end of the surface of the stabilized silver layer of one oxide superconductor, and one end of the surface of the stabilized silver layer of the other oxide superconductor is placed on the end where the solder is placed. And the stabilized silver layers were connected to each other via solder to obtain an oxide superconducting conductor connection structure as shown in FIG. Here, the wrap length of the connecting portion between one oxide superconductor and the other oxide superconductor was 0.5 cm. Further, the solder thickness of the connection portion was 38 μm.
[0030]
(Comparative Example 1)
An oxide superconducting conductor connection structure was obtained in the same manner as in Example 1 except that an oxide superconducting conductor to which silver was not added was used in the oxide superconducting layer.
[0031]
The connection structure of the oxide superconducting conductor obtained in Example 1 and Comparative Example 1 was heat-treated at 500 ° C. for 2 hours in a pure oxygen atmosphere to obtain a measurement sample.
These samples were cooled to 77K with liquid nitrogen, and the specific resistance of each sample was measured. The results are shown in Table 1 below. Further, the resistance value of the metal layer portion (solder layer, stabilized silver layer) required by this, and the stabilized silver layer of the connection portion by the contact specific resistance of the stabilized silver layer and the oxide superconducting layer measured by the preliminary experiment, The calculation results of the contact resistance of the oxide superconducting layer (resistance at the interface between the stabilized silver layer and the oxide superconducting layer) are shown in Table 1 below.
[0032]
[Table 1]

[0033]
In Table 1, * 1 and * 2 are contact specific resistances between the stabilized silver and the oxide superconducting layer at the connection part, and * 3 and * 4 are interfaces between the stabilized silver and the oxide superconducting layer at the connection part. Resistance. As is apparent from the results shown in Table 1, the connection structure of Comparative Example 1 has a resistance of 1.1 × 10 6 at the interface between the oxide superconducting layer and the stabilized silver layer in the connection portion. ^-6 It can be seen that it is ohm, which is two orders of magnitude greater than the resistance of a metal layer such as a stabilized silver layer or solder. On the other hand, according to the connection structure of Example 1, the contact resistance between the oxide superconducting layer added with silver and the stabilized silver layer can be sufficiently reduced, and the oxide superconducting layer and the stabilized silver layer at the connection portion The interface resistance is 4.4 × 10 ^-8 It can be seen that the resistance is equal to the resistance of a metal layer such as a stabilized silver layer or solder.
Moreover, the total connection resistance of the connection part of the comparative example 1 calculated from the measured value is 1.1 × 10. ^-6 On the other hand, the total connection structure of the connection portion of Example 1 is 6.9 × 10 6. ^-8 It can be seen that the resistance of the connection portion can be reduced to a practically satisfactory level.
In addition, in the said Example, although the wrap length was 0.5 cm, even if it made this length 100 times, it confirmed that the connection resistance of a connection part could be about 1/100 of the past.
[0034]
Also, an oxide produced in the same manner as in Example 1 except that the amount of silver added to the Y-Ba-Cu-O-based oxide superconducting layer was changed in the range of 0 wt% to 30 wt%. Regarding the connection structure of the superconducting conductors, the contact resistance between the oxide superconducting layer and the stabilized silver layer was examined. As for the case where the amount of silver added was in the range of 10 wt% to 30 wt%, Example 1 The contact resistance between the oxide superconducting layer and the stabilized silver layer can be sufficiently reduced, and the resistance at the interface between the oxide superconducting layer and the stabilized silver layer at the connecting portion is almost the same as that in Example 1. It was found that the resistance was the same as the resistance of a metal layer such as a stabilized silver layer or solder. In addition, for the case where the addition amount of silver is 5 wt% or more and less than 10 wt%, when the addition amount of silver changes, the contact resistance between the oxide superconducting layer and the stabilized silver layer also changes. It was found that the contact resistance between the superconducting layer and the stabilized silver layer can be sufficiently reduced, and the resistance of the connection portion can be reduced to a level that does not cause a problem in practice. In addition, it was found that when the addition amount of silver was less than 5% by weight, the contact resistance between the oxide superconducting layer and the stabilized silver layer could not be sufficiently reduced, and there was a possibility of causing a practical problem.
[0035]
【The invention's effect】
As described above, in the connection structure of the oxide superconducting conductor according to claim 1, the contact resistance between the oxide superconducting layer to which silver has been added and the stabilized silver layer is sufficient due to the above-described configuration. The resistance of the interface between the oxide superconducting layer and the stabilized silver layer at the joint becomes the same value as the resistance of the metal layer such as the stabilized silver layer or solder. Therefore, the resistance of the joint is a practical problem. It can be reduced to the extent that there is no problem, and it can be easily lengthened and the stability can be secured, so that the application can be expanded. Further, the oxide superconducting layer to which silver is added can supply silver at the time of formation of the oxide superconductor by supplying the silver raw material to the reaction chamber separately from the oxide superconductor raw material gas. The superconducting conductor is placed in the CVD reaction vessel again, and there is no process of depositing and sintering fine powder for forming a superconducting thin film for connection on the contact portion, thus simplifying the connection work. .
In the oxide superconductor connection structure according to claim 1, the surfaces of the plurality of oxide superconductors on the side of the stabilized silver layer are opposed to each other, and the stabilized silver layers are connected to each other via solder. Therefore, compared with the conventional oxide superconducting conductor connection structure in which the oxide superconducting thin film is formed on the contact portion of the oxide superconducting conductor by chemical vapor deposition, the strength of the connecting portion is higher. Excellent.
[0036]
In the connection structure of the oxide superconducting conductor according to claim 2, since it is configured as described above, the length can be easily increased, and stability can be secured by the stabilized silver layer. Can be spread. Further, a plurality of oxide superconducting conductors can be obtained simply by disposing a connecting superconducting tape at the butt portion of the oxide superconducting conductor and melting the low melting point oxide superconducting layer of the tape. Through low-melting-point oxide superconducting layers Since it can be connected, there is no step of depositing and sintering fine powder for forming the superconducting thin film for connection on the abutting portion by placing the oxide superconducting conductor in the CVD reaction vessel again. Work can be simplified.
In the connection structure of the oxide superconducting conductor according to claim 2, the butted portion of the plurality of oxide superconducting conductors is covered with a connecting superconducting tape, A plurality of oxide superconductors are connected by a low melting point oxide superconducting layer, Furthermore, since a stabilized silver layer is formed on the superconducting tape for connection and the oxide superconducting conductor on both sides thereof, an oxide superconducting thin film is formed by chemical vapor deposition on the contact portion of the oxide superconducting conductor. Compared to a conventional oxide superconducting conductor connection structure, the connection portion is superior in strength.
In the method for connecting an oxide superconducting conductor according to claim 3, the structure for connecting the oxide superconducting conductor does not complicate the operation for connecting, and the structure for connecting an oxide superconducting conductor according to claim 2. Can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a first embodiment of a connection structure for an oxide superconducting conductor according to the present invention.
FIG. 2 is a diagram showing a schematic configuration of an apparatus for manufacturing an oxide superconducting conductor used in the connection structure for an oxide superconducting conductor according to the first embodiment.
FIG. 3 is a cross-sectional view showing a second embodiment of the connection structure of the oxide superconducting conductor of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Tape-like base material, 2 ... Oxide superconducting layer added with silver, 3 ... Stabilized silver layer, 3a ... Surface, 5 ... Solder, 10 ... Oxidation Superconducting material, 15 ... connecting portion, 20 ... oxide superconducting conductor, 20b ... end face, 21 ... tape-like substrate, 24 ... oxide superconducting layer, 25 ... connection Superconducting tape, 26 ... base material, 27 ... low melting point oxide superconducting layer, 28 ... stabilized silver layer, 29 ... butt, W ... wrap length.

Claims

The stabilized silver layer of a plurality of oxide superconducting conductors in which an oxide superconducting layer to which silver is added is formed on a tape-like substrate, and a stabilized silver layer is further formed on the oxide superconducting layer An oxide superconducting conductor connection structure, wherein the stabilized silver layers are connected to each other through solder, with the surfaces on the sides facing each other.

End surfaces of a plurality of oxide superconducting conductors formed by forming an oxide superconducting layer on a tape-like base material are butted against each other, and the butted portion is formed on the base material made of a highly conductive metal. A low melting point oxide superconducting layer made of an oxide superconducting material having a lower melting point than the material forming the layer is covered with a connecting superconducting tape, and both sides of the butted portions of the plurality of oxide superconducting conductors are covered with the low melting point An oxide superconducting conductor connection structure, characterized in that it is connected by an oxide superconducting layer, and further comprises a stabilizing silver layer formed on the superconducting tape for connection and the oxide superconducting conductors on both sides thereof.

A plurality of oxide superconducting conductors having an oxide superconducting layer formed on a tape-shaped substrate are butted against each other, and the oxide superconducting material is formed on the butted portion on a substrate made of a highly conductive metal. A superconducting tape for connection in which a low-melting-point oxide superconducting layer made of an oxide superconducting material having a lower melting point than the material forming the layer is formed, and the plurality of oxide superconductors are connected to each other via the low-melting-point oxide superconducting layer. and arranged to contact, and characterized by melting the low melting point oxide superconducting layer of the connecting superconducting tape further forms a stabilized silver layer on the connecting superconducting tape and which on either side of the oxide superconductor on To connect oxide superconducting conductor.