JP3652978B2 - Method for producing YBa2Cu3O7-x superconducting film by electrophoretic electrodeposition method - Google Patents
Method for producing YBa2Cu3O7-x superconducting film by electrophoretic electrodeposition method Download PDFInfo
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- 238000004070 electrodeposition Methods 0.000 title claims description 27
- 238000000034 method Methods 0.000 title claims description 19
- 238000004519 manufacturing process Methods 0.000 title claims description 11
- 229910003098 YBa2Cu3O7−x Inorganic materials 0.000 title 1
- 239000011882 ultra-fine particle Substances 0.000 claims description 52
- 239000000843 powder Substances 0.000 claims description 36
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 24
- 239000002245 particle Substances 0.000 claims description 23
- 229910052760 oxygen Inorganic materials 0.000 claims description 20
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 19
- 239000001301 oxygen Substances 0.000 claims description 19
- 238000010438 heat treatment Methods 0.000 claims description 17
- 239000002994 raw material Substances 0.000 claims description 17
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 15
- 229910017604 nitric acid Inorganic materials 0.000 claims description 15
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 14
- 239000000243 solution Substances 0.000 claims description 14
- QGZKDVFQNNGYKY-UHFFFAOYSA-N ammonia Natural products N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 12
- 239000007864 aqueous solution Substances 0.000 claims description 8
- 239000004570 mortar (masonry) Substances 0.000 claims description 8
- ZCYVEMRRCGMTRW-UHFFFAOYSA-N 7553-56-2 Chemical compound [I] ZCYVEMRRCGMTRW-UHFFFAOYSA-N 0.000 claims description 7
- 238000001816 cooling Methods 0.000 claims description 7
- 229910052740 iodine Inorganic materials 0.000 claims description 7
- 239000011630 iodine Substances 0.000 claims description 7
- 239000004065 semiconductor Substances 0.000 claims description 7
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 6
- 239000004020 conductor Substances 0.000 claims description 6
- 238000001652 electrophoretic deposition Methods 0.000 claims description 3
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- 239000002887 superconductor Substances 0.000 description 9
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- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 6
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
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- PAWQVTBBRAZDMG-UHFFFAOYSA-N 2-(3-bromo-2-fluorophenyl)acetic acid Chemical compound OC(=O)CC1=CC=CC(Br)=C1F PAWQVTBBRAZDMG-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
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Description
【０００１】
【発明の属する技術分野】
本発明は、泳動電着法によるＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導膜の製造方法に係り、特にＹＢａ２Ｃｕ３Ｏ７超微粒子原料粉末を用いてＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導膜を製造する方法に関するものである。
【０００２】
【従来の技術】
超伝導体として、ＹＢａ２Ｃｕ３Ｏ７−ｘは、Ｔｃ（９０Ｋ）と液体窒素温度より高いものであり注目されている。ＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導体は、出発原料としてＹ２Ｏ３，Ｂａ（ＮＯ３）２とＣｕＯを用い、仮焼、粉砕、ペレット焼結後、Ａｒ＋２０％Ｏ２混合ガス中で、熱間静水圧加圧（ＨＩＰ）処理を行い、ＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導体のバルクを製造することが知られている。
また、超電導体原料を仮焼きした後、粉砕して溶媒中に分散させ、電気泳動法により電着させて、これを本焼き９００±１００℃で本焼きを行うＹ−Ｂａ−Ｃｕ−Ｏ系酸化物超電導体の超電導体の作成方法が提案されている（例えば特開平１−２５５６９１号公報、特開平５−７８１２４号公報参照）。
【０００３】
【発明が解決しようとする課題】
従来の泳動電着法によるＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導膜の作製法では、平均粒径が２〜３μｍの超伝導粒子を用いているために、大きな基材に電着膜を作製する場合に、電着中の粒子の沈降による膜厚の偏りが顕著に現れるという問題があった。
また、従来の電気泳動法により作成されたＹ−Ｂａ−Ｃｕ−Ｏ系酸化物超電伝体では、ＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導膜についてその特性を改善する製造方法が望まれている。
【０００４】
【課題を解決するための手段】
上記課題を解決するために、本発明の泳動電着法によるＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導膜の製造方法は、ＢａＣＯ３粉末、Ｙ２０３粉末及びＣｕＯ粉末を熱硝酸水溶液に溶解した溶液にクエン酸を加え、次いでアンモニア水でｐＨ６．８を越えないように中和し、この溶液を加熱して、Ｃｕ、ＢａＯ及びＹ２Ｏ３からなり、そのモル比がＣｕ：ＢａＯ：Ｙ２Ｏ３＝６：４：１のＹＢａ２Ｃｕ３Ｏ７超微粒子原料粉末を作製する工程、前記工程で作製したＹＢａ２Ｃｕ３Ｏ７の超微粒子原料粉末を、１気圧の酸素雰囲気中で９００℃〜９３０℃に加熱、冷却して４５０〜５５０℃に保持し、冷却する熱処理を行い、ＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子のクラスターを作製する工程、前記工程で作製したＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子のクラスターを乳鉢でＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子に分離させる工程、前記工程で分離させた平均粒径が０．０４〜０．０８μｍのＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子をヨウ素を添加したアセトン中に超音波振動を加えて分散させ、導電体または半導体上に泳動電着を行う工程、前記工程で導電体上または半導体上に泳動電着されたＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子からなる膜を９００℃〜９５０℃、１気圧の酸素雰囲気中で熱処理を行う工程、からなることを特徴とするものである。
【０００５】
【作用】
本発明の泳動電着法によるＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導膜の製造方法は、
ＢａＣＯ３粉末、Ｙ２０３粉末及びＣｕＯ粉末を熱硝酸水溶液に溶かした溶液にクエン酸を加え、次いでアンモニアで中和を行い、この溶液を加熱して、Ｃｕ、ＢａＯ及びＹ２Ｏ３からなり、モル比がＣｕ：ＢａＯ：Ｙ２Ｏ３＝６：４：１のＹＢａ２Ｃｕ３Ｏ７超微粒子原料粉末を作製し、このＹＢａ２Ｃｕ３Ｏ７超微粒子原料粉末を９００℃〜９３０℃で１気圧の酸素雰囲気中で熱処理を行うことにより、ＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子のクラスターを作製し、これを乳鉢で分離させてＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子にするるものである。
ＹＢａ２Ｃｕ３Ｏ７−ｘについてｘ＝０のとき、すなわちＹＢａ２Ｃｕ３Ｏ７は絶縁体であり、超伝導にはならないものである。ＹＢａ２Ｃｕ３Ｏ７超微粒子原料粉末を９００℃〜９３０℃で１気圧の酸素雰囲気中で熱処理を行う過程において、ｘが０．１〜０．２となり、すなわちＹＢａ２Ｃｕ３Ｏ６．９〜ＹＢａ２Ｃｕ３Ｏ６．８となり、ホールキャリアが生じて超伝導性を発現するものである。好ましくは、熱処理は、１気圧の酸素雰囲気中で９００℃〜９３０℃に加熱、冷却して４５０〜５５０℃に６時間保持、冷却する過程において、ｘが０．１〜０．２となり、すなわちＹＢａ２Ｃｕ３Ｏ６．９〜ＹＢａ２Ｃｕ３Ｏ６．８となり、ホールキャリアが生じて超伝導性を発現するものである。
【０００６】
本発明は、ＢａＣＯ３粉末、Ｙ２０３粉末及びＣｕＯ粉末を熱硝酸水溶液に溶かした溶液にクエン酸を加え、次いでアンモニアで中和を行い、この溶液を加熱して、Ｃｕ、ＢａＯ及びＹ２Ｏ３からなり、モル比がＣｕ：ＢａＯ：Ｙ２Ｏ３＝６：４：１のＹＢａ２Ｃｕ３Ｏ７超微粒子原料粉末を作製することにより、平均粒径が０．０４〜０．０８μｍのようなサブミクロンサイズ以下のＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子にすることができるものであり、また平均粒径が０．０４〜０．０８μｍのようなサブミクロンサイズ以下のＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子を用いて泳動電着されたＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子からなる膜に対する熱処理を９００℃〜９５０℃で１気圧の酸素雰囲気中で行うことでＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導膜の作製が可能になった。
また、本発明の泳動電着法によるＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導膜の製造方法では、電着浴であるヨウ素を添加したアセトン中に分散させる超伝導微粒子の平均粒径が０．０４〜０．０８μｍのような超微粒子であることにより、電着浴におけるＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子の分散が安定であり、電着浴で電着中にＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子が沈降する速度が遅くなり、より均一なＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導膜が得られる。またＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導微粒子が平均粒径が０．０４〜０．０８μｍのように微細であることから、ＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導膜は稠密性が高いものが得られ、またＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導膜が基材から剥離するということがないものである。
【０００７】
【発明の実施の形態】
本発明におけるＣｕ、ＢａＯ及びＹ２Ｏ３からなり、モル比がＣｕ：ＢａＯ：Ｙ２Ｏ３＝６：４：１のＹＢａ２Ｃｕ３Ｏ７の超微粒子原料粉末を作製する工程について説明する。
まず、ＣｕＯ粉末、ＢａＣＯ３粉末、Ｙ２０３粉末のそれぞれを、ＹＢａ２Ｃｕ４Ｏ７の超微粒子原料粉末とするために、Ｙ：Ｂａ：Ｃｕが１：２：３の比率となるように秤量し、これらを混合して、熱硝酸水溶液、例えば硝酸に蒸留水を加え７０〜８０℃とした硝酸水溶液に溶かす。ここで硝酸水溶液は、その色がマリンブルーになるまで硝酸を足す。またここで白い沈殿物が形成された場合には、白い沈殿物が溶けるまで蒸留水を加える。次いで硝酸水溶液の温度を４０℃程度に下げる。白い沈殿物が生じた場合は５０℃程度まで温度を上げて、白い沈殿物が完全に溶解させる。次いで白い沈殿物が完全に溶解した状態で、クエン酸を加える。
【０００８】
次にアンモニア水によってｐＨ６．８を越えないように中和滴定を行う。ｐＨ６．８では液体は、ダークブルー色になる。アンモニア水による中和滴定のｐＨ値は、ｐＨ６．９を越えると水酸化物や塩基性塩が現れてしまうので、ｐＨ６．９を越えないようにする。
アンモニア水によってｐＨ６．８を越えないように中和滴定された溶液を加熱する。溶液は加熱によって水分の揮発に伴って粘性が増し、しだいにクエン酸のために大きく膨張し、最後に硝酸アンモニウムのために自発的に燃焼する。このようにしてＣｕ、ＢａＯ及びＹ２Ｏ３からなり、そのモル比がＣｕ：ＢａＯ：Ｙ２Ｏ３＝６：４：１のＹＢａ２Ｃｕ４Ｏ７の超微粒子原料粉末を得るものである。
【０００９】
本発明において、作製されたＹＢａ２Ｃｕ３Ｏ７の超微粒子原料粉末を９００℃〜９３０℃、１気圧の酸素雰囲気中で熱処理を行うことにより、好ましくは、１気圧の酸素雰囲気中で９００℃〜９３０℃に加熱、冷却して４５０〜５５０℃に６時間保持し、冷却する熱処理を行うことにより、ＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子のクラスターを作製する。ＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子のクラスターを作製する工程は、例えば９２０℃で２０時間、１Ｌ／ｍｉｎの酸素流量で熱処理を行い、ＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子が集まったクラスターを作製するものである。
超伝導微粒子が集まったクラスターを乳鉢で分離させる工程は、自動乳鉢で２時間、分離処理を行い、平均粒径が０．０４〜０．０８μｍのようなサブミクロンサイズ以下のＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子に分離させるものである。
本発明において、Ｃｕ、ＢａＯ及びＹ２Ｏ３からなり、モル比がＣｕ：ＢａＯ：Ｙ２Ｏ３＝６：４：１のＹＢａ２Ｃｕ３Ｏ７超微粒子原料粉末を、９００℃〜９３０℃、１気圧の酸素雰囲気中で熱処理を行ってＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子のクラスターとし、これを乳鉢でＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子に分離させるもので、ボールミルにより粉砕のように機械的にすりつぶす方法で超伝導粒子にするものとは異なり、機械的応力により結晶が変形したり、結晶が劣化することも少なく、またボールミルの粉砕球からの不純物の混入も起こらない。
【００１０】
また、分離させたＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子をヨウ素を添加したアセトン中に分散させ、導電性基材または半導体基材に泳動電着を行う工程は、ＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子を、ヨウ素を０．０５％添加したアセトン中に超音波振動を加えて分散させることにより、分散性を向上させ、５ボルトから数百ボルト程度の電圧で導電体例えば銀基板、または半導体上に泳動電着を行うものである。
また、導電体または半導体上に泳動電着されたＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子からなる膜を９００〜９５０℃で１気圧の酸素雰囲気中で熱処理を行う工程は、例えば９４５℃で１時間、１Ｌ／ｍｉｎの酸素流量で熱処理を行い、ＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導膜を作製した。
【００１１】
本発明において、電着基材としては、導電材料もしくは導電性膜をコーティングした絶縁材料で、例えば銀基板、絶縁体に銀メッキした基板を用いる。また導電体は、その表面に凹凸があるものでも均一に泳動電着することができる。すなわち基材の表面が平坦なものあるいは凹凸がある立体的なものに、ＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導膜を均一に泳動電着することができる。または半導体上にも同様にＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導膜を均一に泳動電着することができる。
このように均一に泳動電着することができるので、長尺導電基材に本発明の泳動電着法により均一にＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導膜を形成することにより超伝導テープ材として用いることができ、また表面が凹凸の立体形状の基材上に、ＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導膜を均一に形成することにより、超伝導磁気シールド材として用いることができる。
【００１２】
【実施例】
本発明の実施例について、具体的データを示し説明する。
まず、ＢａＣＯ３粉末７８．４３５ｇ、Ｙ２Ｏ３粉末２２．６９５ｇ、ＣｕＯ粉末４７．９７０ｇを秤量し、これらを混合して硝酸１８５ｍｌに１６００ｍｌ程度の蒸留水を加え７０〜８０℃の硝酸水溶液に溶かす。次に硝酸水溶液がマリンブルーになるまで硝酸を足し、また白い沈殿物が溶けるまで蒸留水を加える。次に硝酸水溶液の温度を４０℃程度に下げ。白い沈殿物が生じた場合は５０℃程度まで温度を上げる。沈殿物が完全に溶解したら１２６．６３ｇのクエン酸を加える。次にアンモニア水によってｐＨ６．８を越えないように中和滴定を行う。ｐＨ６．８では液体は、ダークブルー色になる。このアンモニアで中和した溶液を加熱する。加熱により溶液の水分は揮発し、これにに伴って粘性が増し、しだいにクエン酸のために大きく膨張し、最後に硝酸アンモニウムのために自発的に燃焼する。このようにしてそのモル比がＣｕ：ＢａＯ：Ｙ２Ｏ３＝＝６：４：１のＹＢａ２Ｃｕ３Ｏ７超微粒子原料粉末を作製した。
【００１３】
上述のようにして得られたＹＢａ２Ｃｕ４Ｏ７の超微粒子原料粉末を１Ｌ／ｍｉｎの酸素流量の雰囲気で、９２０℃で２０時間、冷却して４５０℃に６時間保持し、これを冷却してＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子が集まったクラスターとした。このようにＹＢａ２Ｃｕ３Ｏ７超微粒子原料粉末を１気圧の酸素雰囲気中で９００℃〜９３０℃に加熱、冷却して４５０〜５５０℃に６時間保持し、これを冷却する熱処理の過程で、ＹＢａ２Ｃｕ３Ｏ７−ｘ（ｘ＝０．１〜０．２）の超伝導超微粒子が集まったクラスターとなる。すなわちＹＢａ２Ｃｕ３Ｏ６．９〜ＹＢａ２Ｃｕ３Ｏ６．８となり、ホールキャリアが生じて超伝導性を発現した。
ＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子が集まったクラスターを、自動乳鉢で２時間、分離処理を行い、サブミクロンサイズ以下のＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子に分離させた。
【００１４】
図１は、分離したＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子を光の回折による粒度分布測定法により測定した粒度分布を示すもので、横軸は粒径（μｍ）、縦軸は個数（％）である。
ＹＢａ２Ｃｕ３Ｏ７−ｘ伝導超微粒子の粒度分布は、図１に示すように約０．０５μｍ（５０ｎｍ）に極大を持って分布されており、その平均粒径は０．０６１μｍ（６１ｎｍ）であった。従来の共沈法により得られたＹＢａ２Ｃｕ４Ｏ７原料粉末は平均粒径３．４４μｍであり、この従来の共沈法のものに比べて、本発明で得られたＹＢａ２Ｃｕ３Ｏ７の超微粒子原料粉末を９２０℃で２０時間、１Ｌ／ｍｉｎの酸素流量で熱処理を行ったクラスターを乳鉢で２時間、分離処理を行ったＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子は微細なものであった。
図１に示した平均粒径０．０６１μｍのＹＢａ２Ｃｕ３Ｏ７−ｘ伝導超微粒子をヨウ素４０ｍｇを添加したアセトン１００ｍｌ中に超音波で分散させ、銀基板に１０Ｖの電圧で泳動電着を行い、銀基板上に厚さ２μｍ〜４μｍの泳動電着膜を形成させた。
銀基板上に泳動電着されたＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子の膜を９４５℃で１時間、１Ｌ／ｍｉｎの酸素流量で熱処理を行い、超伝導ＹＢａ２Ｃｕ３Ｏ７−ｘ膜を得た。
【００１５】
得られたＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子の泳動電着膜は、超伝導体の転移温度（Ｔｃ）が９０Ｋであり、また図１に示した従来の共沈法により得られた平均粒径３．４４μｍのＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子の泳動電着膜より超伝導転移の幅が狭く、シヤープに超伝導体に転移した。
得られたＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子の泳動電着膜は、稠密性が高く、本発明の９４５℃で１時間、１Ｌ／ｍｉｎの酸素流量の雰囲気で熱処理を行った泳動電着膜クラックが見られなかった。これに対して従来の共沈法により得られた平均粒径３．４４μｍのＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子の泳動電着膜では多数のクラックが発生した、これは本発明のＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子の泳動電着膜は稠密性が高いことを反映している。
【００１６】
【発明の効果】
以上説明したように、本発明の泳動電着法によるＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導膜の製造方法によれば、ヨウ素を添加したアセトン電着浴に分散させるＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導微粒子が超微粒子であるので、電着中にＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子の沈降による膜厚の偏りが軽減されて、均一なＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導膜が得られ、大きな面積の立体的な基材にも均一なＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導膜を作製できるという効果を有し、またＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導膜は、その転移温度（Ｔｃ）での転移がシャープであり、さらに稠密性の高いものが得られ、超伝導状態での臨界電流が大く、機械的耐久性に優れ、振動等によりＹＢａ２Ｃｕ３Ｏ７−ｘ膜が剥離するということがないという効果を奏するものである。
【図面の簡単な説明】
【図１】 本発明実施例のＹＢａ２Ｃｕ３Ｏ７−ｘ超伝導超微粒子の粒度分布を示す図[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a YBa 2 Cu 3 O 7-x superconducting film by electrophoretic electrodeposition, and in particular, YBa 2 Cu 3 O 7-x superconductivity using YBa 2 Cu 3 O 7 ultrafine particle raw material powder. The present invention relates to a method for manufacturing a membrane.
[0002]
[Prior art]
As a superconductor, YBa 2 Cu 3 O 7-x is attracting attention because it is higher than Tc (90K) and the liquid nitrogen temperature. YBa 2 Cu 3 O 7-x superconductor uses Y 2 O 3 , Ba (NO 3 ) 2 and CuO as starting materials, and after calcining, pulverization and pellet sintering, in an Ar + 20% O 2 mixed gas It is known to perform a hot isostatic pressing (HIP) process to produce a bulk of YBa 2 Cu 3 O 7-x superconductor.
In addition, the Y-Ba-Cu-O system in which the superconductor raw material is calcined, pulverized and dispersed in a solvent, and electrodeposited by electrophoresis, followed by main baking at 900 ± 100 ° C. A method for producing a superconductor of an oxide superconductor has been proposed (see, for example, Japanese Patent Laid-Open Nos. 1-255691 and 5-78124).
[0003]
[Problems to be solved by the invention]
In the conventional method for producing a YBa 2 Cu 3 O 7-x superconducting film by electrophoretic electrodeposition, superconducting particles having an average particle diameter of 2 to 3 μm are used, so that an electrodeposited film is produced on a large substrate. In this case, there has been a problem that the unevenness of the film thickness due to the sedimentation of the particles during electrodeposition appears remarkably.
In addition, in the Y-Ba-Cu-O-based oxide superconductor prepared by the conventional electrophoresis method, a manufacturing method for improving the characteristics of the YBa 2 Cu 3 O 7-x superconducting film is desired. Yes.
[0004]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the method for producing a YBa 2 Cu 3 O 7-x superconducting film by the electrophoretic electrodeposition method of the present invention involves dissolving BaCO 3 powder,
[0005]
[Action]
The method for producing a YBa 2 Cu 3 O 7-x superconducting film by the electrophoretic electrodeposition method of the present invention,
Citric acid is added to a solution obtained by dissolving BaCO 3 powder,
Regarding YBa 2 Cu 3 O 7-x , when x = 0, that is, YBa 2 Cu 3 O 7 is an insulator and does not become superconducting. In the process of heat-treating the YBa 2 Cu 3 O 7 ultrafine particle raw material powder at 900 ° C. to 930 ° C. in an oxygen atmosphere of 1 atm, x becomes 0.1 to 0.2, that is, YBa 2 Cu 3 O 6.9. ˜YBa 2 Cu 3 O 6.8 , and hole carriers are generated to express superconductivity. Preferably, in the heat treatment, in the process of heating and cooling to 900 ° C. to 930 ° C. in an oxygen atmosphere of 1 atm and holding at 450 to 550 ° C. for 6 hours and cooling, x becomes 0.1 to 0.2, YBa 2 Cu 3 O 6.9 ~YBa 2 Cu 3 O 6.8 , and the one in which hole carriers express superconductivity occurs.
[0006]
In the present invention, citric acid is added to a solution obtained by dissolving BaCO 3 powder,
Further, in the method for producing a YBa 2 Cu 3 O 7-x superconducting film by the electrophoretic electrodeposition method of the present invention, the average particle size of the superconducting fine particles dispersed in acetone as an electrodeposition bath with iodine added is 0.00. Due to the ultrafine particles of 04 to 0.08 μm, the dispersion of the YBa 2 Cu 3 O 7-x superconducting ultrafine particles in the electrodeposition bath is stable, and YBa 2 Cu 3 during electrodeposition in the electrodeposition bath is stable. The rate at which the O 7-x superconducting ultrafine particles settle is reduced, and a more uniform YBa 2 Cu 3 O 7-x superconducting film is obtained. In addition, since the YBa 2 Cu 3 O 7-x superconducting fine particles are as fine as an average particle size of 0.04 to 0.08 μm, the YBa 2 Cu 3 O 7-x superconducting film has a high density. In addition, the YBa 2 Cu 3 O 7-x superconducting film does not peel from the substrate.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The process for producing ultrafine raw material powder of YBa 2 Cu 3 O 7 composed of Cu, BaO and Y 2 O 3 and having a molar ratio of Cu: BaO: Y 2 O 3 = 6: 4: 1 will be described. .
First, in order to make each of the CuO powder, the BaCO 3 powder, and the
[0008]
Next, neutralization titration is performed with aqueous ammonia so as not to exceed pH 6.8. At pH 6.8, the liquid becomes dark blue. When the pH value of neutralization titration with aqueous ammonia exceeds pH 6.9, hydroxides and basic salts will appear, so pH 6.9 should not be exceeded.
The solution neutralized with aqueous ammonia so as not to exceed pH 6.8 is heated. The solution increases in viscosity as the water volatilizes due to heating, gradually expands greatly due to citric acid, and finally burns spontaneously due to ammonium nitrate. Thus, an ultrafine raw material powder of YBa 2 Cu 4 O 7 composed of Cu, BaO and Y 2 O 3 and having a molar ratio of Cu: BaO: Y 2 O 3 = 6: 4: 1 is obtained. .
[0009]
In the present invention, the produced ultrafine raw material powder of YBa 2 Cu 3 O 7 is heat-treated in an oxygen atmosphere of 900 ° C. to 930 ° C. and 1 atmosphere, and preferably 900 ° C. in an oxygen atmosphere of 1 atmosphere. A cluster of YBa 2 Cu 3 O 7-x superconducting ultrafine particles is produced by heating and cooling to ˜930 ° C. and holding at 450 to 550 ° C. for 6 hours, followed by cooling heat treatment. The step of producing a cluster of YBa 2 Cu 3 O 7-x superconducting ultrafine particles is performed, for example, by performing heat treatment at 920 ° C. for 20 hours at an oxygen flow rate of 1 L / min, and YBa 2 Cu 3 O 7-x superconducting ultrafine particles. This is a cluster that collects.
The process of separating the cluster in which the superconducting fine particles are collected with a mortar is performed by an automatic mortar for 2 hours, and YBa 2 Cu 3 O having a submicron size of 0.04 to 0.08 μm or less in average particle size. 7-x superconducting ultrafine particles are separated.
In the present invention, YBa 2 Cu 3 O 7 ultrafine raw material powder composed of Cu, BaO and Y 2 O 3 and having a molar ratio of Cu: BaO: Y 2 O 3 = 6: 4: 1 is used at 900 ° C. to 930 ° C. , and subjected to heat treatment in an oxygen atmosphere at 1 atm and YBa 2 Cu 3 O 7-x superconducting ultrafine clusters, which intended to separate the YBa 2 Cu 3 O 7-x superconducting ultrafine particles in a mortar, Unlike particles that are mechanically ground by ball milling to produce superconducting particles, crystals are less likely to be deformed or deteriorated by mechanical stress, and impurities from ball milling balls are mixed. Also does not happen.
[0010]
In addition, the process of dispersing the separated YBa 2 Cu 3 O 7-x superconducting ultrafine particles in acetone to which iodine is added and performing electrophoretic deposition on the conductive substrate or the semiconductor substrate is YBa 2 Cu 3 O. The 7-x superconducting ultrafine particles are dispersed by applying ultrasonic vibration in acetone to which 0.05% of iodine is added to improve dispersibility, and a conductor, for example, at a voltage of about 5 volts to several hundred volts. Electrophoretic electrodeposition is performed on a silver substrate or a semiconductor.
In addition, the step of heat-treating a film made of YBa 2 Cu 3 O 7-x superconducting ultrafine particles electrophoretically deposited on a conductor or semiconductor at 900 to 950 ° C. in an oxygen atmosphere of 1 atm is, for example, 945 ° C. Then, heat treatment was performed at an oxygen flow rate of 1 L / min for 1 hour to produce a YBa 2 Cu 3 O 7-x superconducting film.
[0011]
In the present invention, as the electrodeposition base material, a conductive material or an insulating material coated with a conductive film, for example, a silver substrate or a substrate obtained by silver plating on an insulator is used. Moreover, even if the conductor has unevenness on its surface, it can be uniformly electrophoretically deposited. That is, the YBa 2 Cu 3 O 7-x superconducting film can be uniformly electrophoretically deposited on a substrate having a flat surface or a three-dimensional surface having irregularities. Alternatively, the YBa 2 Cu 3 O 7-x superconducting film can be uniformly electrophoretically deposited on the semiconductor.
Since electrophoretic electrodeposition can be performed uniformly in this way, a superconducting tape material can be obtained by uniformly forming a YBa 2 Cu 3 O 7-x superconducting film on a long conductive substrate by the electrophoretic electrodeposition method of the present invention. It can also be used as a superconducting magnetic shield material by uniformly forming a YBa 2 Cu 3 O 7-x superconducting film on a three-dimensional substrate having an uneven surface.
[0012]
【Example】
Examples of the present invention will be described with specific data.
First, 78.435 g of BaCO 3 powder, 22.695 g of Y 2 O 3 powder, and 47.970 g of CuO powder were weighed and mixed, and about 1600 ml of distilled water was added to 185 ml of nitric acid to form an aqueous nitric acid solution at 70 to 80 ° C. Melt. Next, add nitric acid until the aqueous nitric acid solution becomes marine blue, and add distilled water until the white precipitate dissolves. Next, the temperature of the aqueous nitric acid solution is lowered to about 40 ° C. If a white precipitate forms, raise the temperature to about 50 ° C. When the precipitate is completely dissolved, add 126.63 g of citric acid. Next, neutralization titration is performed with aqueous ammonia so as not to exceed pH 6.8. At pH 6.8, the liquid becomes dark blue. The ammonia neutralized solution is heated. The water in the solution is volatilized by heating, and as a result, the viscosity increases, gradually expanding due to citric acid, and finally burning spontaneously due to ammonium nitrate. Thus, a YBa 2 Cu 3 O 7 ultrafine particle raw material powder having a molar ratio of Cu: BaO: Y 2 O 3 == 6: 4: 1 was produced.
[0013]
The ultrafine raw material powder of YBa 2 Cu 4 O 7 obtained as described above was cooled at 920 ° C. for 20 hours and held at 450 ° C. for 6 hours in an atmosphere with an oxygen flow rate of 1 L / min. The YBa 2 Cu 3 O 7-x superconducting ultrafine particles were collected. In this way, the YBa 2 Cu 3 O 7 ultrafine particle raw material powder is heated and cooled to 900 ° C. to 930 ° C. in an oxygen atmosphere of 1 atm and held at 450 to 550 ° C. for 6 hours. , YBa 2 Cu 3 O 7-x (x = 0.1 to 0.2) superconductive ultrafine particles are collected. That YBa 2 Cu 3 O 6.9 ~YBa 2 Cu 3 O 6.8 , and the Hall carrier expressed superconductivity occurs.
The cluster in which YBa 2 Cu 3 O 7-x superconducting ultrafine particles gathered was subjected to separation treatment in an automatic mortar for 2 hours, and separated into YBa 2 Cu 3 O 7-x superconducting ultrafine particles of submicron size or less. .
[0014]
FIG. 1 shows the particle size distribution of separated YBa 2 Cu 3 O 7-x superconducting ultrafine particles measured by a particle size distribution measurement method by light diffraction, the horizontal axis is the particle size (μm), and the vertical axis is the number of particles. (%).
As shown in FIG. 1, the particle size distribution of YBa 2 Cu 3 O 7-x conductive ultrafine particles is distributed with a maximum at about 0.05 μm (50 nm), and the average particle size is 0.061 μm (61 nm). Met. The YBa 2 Cu 4 O 7 raw material powder obtained by the conventional coprecipitation method has an average particle size of 3.44 μm. Compared with this conventional coprecipitation method, YBa 2 Cu 3 O obtained by the present invention. No. 7 ultrafine raw material powder was subjected to heat treatment at 920 ° C. for 20 hours at an oxygen flow rate of 1 L / min for 2 hours in a mortar, and YBa 2 Cu 3 O 7-x superconducting ultrafine particles were subjected to separation treatment. It was something.
The YBa 2 Cu 3 O 7-x conductive ultrafine particles having an average particle size of 0.061 μm shown in FIG. 1 are dispersed ultrasonically in 100 ml of acetone to which 40 mg of iodine is added, and electrophoretic electrodeposition is performed on a silver substrate at a voltage of 10V. The electrophoretic electrodeposition film having a thickness of 2 μm to 4 μm was formed on the silver substrate.
A film of YBa 2 Cu 3 O 7-x superconducting ultrafine particles electrophoretically deposited on a silver substrate was heat-treated at 945 ° C. for 1 hour at an oxygen flow rate of 1 L / min to obtain superconducting YBa 2 Cu 3 O 7- An x film was obtained.
[0015]
The electrophoretic electrodeposition film of the obtained YBa 2 Cu 3 O 7-x superconducting ultrafine particles has a superconductor transition temperature (Tc) of 90 K, and is obtained by the conventional coprecipitation method shown in FIG. Further, the width of the superconducting transition was narrower than that of the electrophoretic electrodeposition film of YBa 2 Cu 3 O 7-x superconducting ultrafine particles having an average particle size of 3.44 μm, and the superconducting transition was performed in the shape of a shear.
The obtained migration electrodeposition film of YBa 2 Cu 3 O 7-x superconducting ultrafine particles has a high density, and migration was performed in the atmosphere of the present invention at 945 ° C. for 1 hour in an oxygen flow rate of 1 L / min. Electrodeposition cracks were not observed. On the other hand, in the electrophoretic electrodeposition film of YBa 2 Cu 3 O 7-x superconducting ultrafine particles having an average particle diameter of 3.44 μm obtained by the conventional coprecipitation method, many cracks were generated. The electrophoretic electrodeposition film of YBa 2 Cu 3 O 7-x superconducting ultrafine particles reflects the high density.
[0016]
【The invention's effect】
As described above, according to the method for producing a YBa 2 Cu 3 O 7-x superconducting film by electrophoretic electrodeposition according to the present invention, YBa 2 Cu 3 O 7- dispersed in an acetone electrodeposition bath to which iodine is added. Since the x superconducting fine particles are ultrafine particles, the unevenness of the film thickness due to the precipitation of the YBa 2 Cu 3 O 7-x superconducting ultrafine particles during electrodeposition is reduced, and the uniform YBa 2 Cu 3 O 7-x conductive membrane is obtained, having the effect of a three-dimensional substrates uniform also a YBa 2 Cu 3 O 7-x superconducting film of large area can be produced, also YBa 2 Cu 3 O 7-x superconducting film , the transition at the transition temperature (Tc) is sharp, obtained those having higher compactness, the critical current in the superconducting state is large Ku, excellent mechanical durability, YBa 2 Cu due to vibration or the like 3 without that O 7-x film is peeled off It is intended to achieve the cormorants effect.
[Brief description of the drawings]
FIG. 1 is a graph showing the particle size distribution of YBa 2 Cu 3 O 7-x superconducting ultrafine particles according to an embodiment of the present invention.
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