JP3844169B2

JP3844169B2 - Oxide superconductor and manufacturing method thereof

Info

Publication number: JP3844169B2
Application number: JP08195698A
Authority: JP
Inventors: 和也山口; 秀一小早志; 守佐藤
Original assignee: Dowa Holdings Co Ltd; Dowa Mining Co Ltd
Current assignee: Dowa Holdings Co Ltd
Priority date: 1998-03-27
Filing date: 1998-03-27
Publication date: 2006-11-08
Anticipated expiration: 2018-03-27
Also published as: JPH11278923A

Description

【０００１】
【発明の属する技術分野】
本発明は酸化物超電導部材に関するものであり、特に、電流リード、磁気軸受け、磁気シールド、バルクマグネット等に用いられる高磁場下においても高い臨界電流密度を有する酸化物超電導体およびその製造方法に関するものである。
【０００２】
【従来の技術】
従来この種の酸化物超電導体の製造方法として、中間材により基盤との反応を抑える手法としては特願平６ー２２９４１６号公報に示されているような方法があった。これは、ＲＥ、Ｂａ、Ｃｕの化合物を所定のモル比で混合した原料混合体を仮焼し、プレス成形した後、少なくとも該成形体の融点より高い温度領域における焼成工程を含む処理を施してＲＥーＢａーＣｕーＯ系酸化物超電導体を製造する場合における上記焼成工程において前記成形体を支えるために該成形体に直接接触する介在物を、少なくともＲＥ（ＲＥはＹを含む希土類元素）を５０モル％以上含み、かつ、このＲＥを除いては前記超電導体を形成するための元素以外の原料を主な元素として含まない材料で構成したことにより、成形体と成形体及び介在物を支える支持体との反応を抑え、相互拡散を防止する事を可能にしたものである。
【０００３】
【発明が解決しようとする課題】
しかしながら、上記手法によると、必然的に製造する酸化物超電導体の組成がＲＥ元素の過剰側に組成がずれる。すると比較的イオン半径の大きなＲＥ元素を用いてこの手法を行った場合、ＢａサイトにＲＥ元素が過剰に置換して、超電導特性を著しく劣化させてしまうという欠点があった。
【０００４】
本発明は、上述の背景のもとでなされたものであり、比較的イオン半径の大きなＲＥ元素を用いた場合にも、大型でより高い臨界電流密度特性を有する酸化物超電導体及びその製造方法を提供することを目的としている。
【０００５】
【課題を解決するための手段】
上記課題を解決するために、本発明にかかる酸化物超電導体は、
（構成１）ＲＥーＢａーＣｕーＯ系超電導結晶間の方位のズレが±５゜以下となるように配向し、かつ、前記超電導結晶のｃ軸方向の平均的な方向のＲＥ元素（ＲＥはＹを含む希土類元素）の組成ズレが該方向の厚さ１５ｍｍ以上に渡って±１．５モル％以内（ただし、組成はＲＥ、Ｂａ、Ｃｕのみのモル比で示す）であることを特徴とする。
【０００６】
また、本発明かかる酸化物超電導体の製造方法は、
（構成２）ＲＥ化合物（ＲＥはＹを含む希土類元素）、Ｂａ化合物及びＣｕ化合物を含む原料混合体に、少なくとも該原料混合体の融点より高い温度領域における焼成工程を含む処理を施してＲＥーＢａーＣｕーＯ系酸化物超電導体を製造する酸化物超電導体の製造方法において、
前記焼成工程において前記原料混合体を支えるために該原料混合体に直接接触する介在物がＢａ化合物で構成されていて、且つ該介在物中にＲＥ元素（ＲＥはＹを含む希土類元素）を５０モル％以上含まないことを特徴とし、
この構成２の態様として、
（構成３）構成２の酸化物超電導体の製造方法において、
前記Ｂａ化合物がＢａＺｒＯ_３、ＢａＳｎＯ_３又はＢａＰｔＯ_３であることを特徴とし、
（請求項４）構成２又は３の酸化物超電導体の製造方法において、
前記原料混合体にさらにＰｔ、Ｒｈ、Ｃｅの金属又は各化合物の１種または２種以上の元素を０．０５〜５ｗｔ％（化合物の場合はその金属のみの元素重量で示す）添加することを特徴とし、
（構成５）構成２ないし４のいずれかの酸化物超電導体の製造方法において、
前記原料混合体にさらにＡｇの金属又は化合物がＡｇ元素成分のみの重量で１〜６０ｗｔ％添加することを特徴とし、
（請求項６）構成２ないし５のいずれかの酸化物超電導体の製造方法において、
酸素分圧をＰ０＝２×１０^−１〜１ａｔｍとして部分的に溶融する温度以上で溶融した後、室温まで必要に応じて保定及び徐冷行程を加えながら冷却する事を特徴とする。
【０００７】
上述の構成によれば、超電導結晶間の方位のズレが±５゜以下であり、かつ、超電導結晶のｃ軸方向のＲＥ元素の組成ズレが厚さ１５ｍｍ以上に渡って±１．５モル％以内であることから、極めて高い臨界電流密度を有する酸化物超電導体が得られる。
【０００８】
この場合、従来のように、ＲＥーＢａーＣｕーＯ系超電導体を、アルミナもしくはＭｇＯ等の基板上でこの超電導体の融点温度以上で焼成すると、基板と激しく反応し、ＢａサイトやＣｕサイトへのＭｇやＡｌの置換がおこり、組成がＢａおよびＣｕの少ない方へずれ、従って全体としてＲＥ元素の過剰側に組成がずれる。さらに、ｃ軸に配向した結晶を得るために、試料に温度勾配を加えて試料上部に種結晶を接触させ、試料上部から一方向に結晶化を行う場合、試料下部は比較的溶融状態が長くなるため基板との反応が特に激しく起こり、ｃ軸方向に組成勾配を持つように組成ズレが発生する。すると比較的大きなイオン半径のＲＥ元素の場合、Ｂａのイオン半径に近くなるため、ＲＥ元素が過剰にＢａサイトに置換してしまい、超電導特性を著しく劣化させる。そこで、本発明では、超電導体と基板との間に中間相として、Ｂａ化合物で構成されている粉末、成形体、焼結体を用いることにより、Ｂａの減少を抑え、相対的にＲＥの組成ずれも抑制し、より臨界電流密度の高い超電導体を得ることを可能にしたものである。このＢａ化合物としては、ＢａＺｒＯ_３のほかに、ＢａＳｎＯ_３、ＢａＰｔＯ_３等を挙げることができる。
【０００９】
さらに、Ａｇが結晶中に微細に分散するとマイクロクラックが減少し、磁気特性、機械強度、耐水性が向上する。この際、１ｗｔ％より下ではその効果は低く、６０ｗｔ％より多いと超電導電流が流れにくくなり特性が低下してしまう。
【００１０】
（実施例１）
Ｎｄ_２Ｏ_３、ＢａＣＯ_３、ＣｕＯの各原料粉末をＮｄ：Ｂａ：Ｃｕ＝１８：２４：３４になるように秤量した後、ＢａＣＯ_３、ＣｕＯのみを８８０℃で３０時間保持する焼成をしてＢａＣｕＯ_２とＣｕＯの仮焼粉を得た（モル比でＢａＣｕＯ_２：ＣｕＯ＝２４：１０）。この仮焼粉とあらかじめ秤量しておいたＮｄ_２Ｏ_３と更に全体に対して０．５ｗｔ％のＰｔ粉末を加えて混合して８８０℃で１０時間保持する焼成を行い、その後平均粒径約１０μｍに粉砕した。次にこの仮焼粉を直径５３ｍｍ厚さ２８ｍｍのデイスク状に金型を用いて全圧２ｔｏｎ／ｃｍ^２で一軸プレス成形し、成形体を作製した。
【００１１】
次に、ＢａＺｒＯ_３の粉末をアルミナ基板上に外径５０ｍｍ厚さ２ｍｍとなるように桝を使用して敷き、前記成形体をこの敷き粉の上にのせてガス置換を行える炉の中に設置した。ロータリーポンプで０．１Ｔｏｒｒまで炉内を排気した後、大気圧になるまで酸素０．０１％と窒素９９．９９％の混合ガスを流し込んだ。その後もこの混合ガスを０．５Ｌ／ｍｉｎの割合で流しながら以下の焼成工程を行った。
【００１２】
まず、１１５０℃で前記成形体を半溶融状態にした後、上部が低温側となるように５℃／ｃｍの温度勾配を加えて、成形体上部が１０７０℃となるまで１０℃／ｍｉｎで降温し、予め溶融法で作製しておいたＳｍ_１．８（Ｂａ_０．７５Ｓｒ_０．２５）_２．４Ｃｕ_３．４Ｏ_ｘ組成の種結晶を成長方向がｃ軸と平行になるように成形体の上部に接触させる。そこから０．５℃／ｈｒの速度で１０６５℃まで降温した後２０時間温度保持し、９６５℃まで１００時間で降温し、そこから室温まで２０時間かけて徐冷することによって結晶化を行った。
【００１３】
作製した試料は焼き縮みのために直径４５ｍｍ、厚さ２４ｍｍのデイスク状となっていた。結晶化した試料は別のガス置換を行える炉の中に設置される。まず、ロータリーポンプで０．１Ｔｏｒｒまで炉内を排気した後、酸素ガスを流し込んで酸素分圧が９５％以上である大気圧の酸素雰囲気にする。その後も０．５Ｌ／ｍｉｎの流量で酸素ガスを炉内に流しながら、室温から７００℃まで１０時間で昇温し、５０時間保持した後、４５０℃まで１００時間で降温しそこから２５０℃まで２００時間かけて徐冷し、２００℃から室温まで１０時間で降温させることにより超電導体材料を製造した。
【００１４】
得られた材料を育成方向（ディスク状試料の厚さ方向）に垂直に上から５ｍｍ間隔でスライス加工し、それぞれを均一に粉砕して滴定法により組成分析を行った。分析結果を図１に示す。中間層としてＢａＺｒＯ_３の粉末を用いたために、基盤との反応が抑えられ、且つＮｄ元素の過剰側に大きく組成ズレしていなかった。
【００１５】
次に、ミクロな部分の組織を観察するため、偏光顕微鏡及び電子線マイクロアナライザー（ＥＰＭＡ）でＮｄ、Ｂａ、Ｃｕのみの組成比を何点か分析したところ、モル比で図２のような組成の部分が確認された。これらのそれぞれはＡ相：ＮｄＢａ_２Ｃｕ_３Ｏ_６．８相、Ｂ相：Ｎｄ_０．９Ｂａ_２．１Ｃｕ_３Ｏ_６．７５相、Ｃ相：Ｎｄ_１．１Ｂａ_１．９Ｃｕ_３Ｏ_６．９相、Ｄ相：Ｎｄ_４Ｂａ_２Ｃｕ_２Ｏ_１０相であると考えられる。ここで、Ｄ相はＡ，Ｂ，Ｃ相中に０．１〜５０μｍ程度に微細に分散していた。
【００１６】
また、育成表面の目視による観察によって、異方位の核発生の形跡が無い部分を選んで、背面反射ラウエ法により材料表面の中心付近および端付近を３ｍｍ間隔で各３点ずつ結晶の方位を測定したところ、種結晶を反映していずれもほぼｃ軸に配向し、隣接する結晶間の方位のズレが２゜程度であった。さらに、目視によって観察される異方位の核発生は試料表面の少なくとも80％以上について見られず、実質的に単結晶状の材料であることが確認された。
【００１７】
得られたディスク状材料を育成方向（ディスク状試料の厚さ方向）に垂直に上から５ｍｍ間隔でスライス加工し、中心付近における臨界温度（Ｔｃ）および外部磁場１Ｔ中の臨界電流密度を測定したところ、それぞれ図３のように厚さ方向に大きな組成ズレが無かったために、厚さ方向に上から15mmまで高い値を示していた。
【００１８】
（実施例２）
Ｎｄ_２Ｏ_３、ＢａＣＯ_３、ＣｕＯの各原料粉末をＮｄ：Ｂａ：Ｃｕ＝１４：２３：３２になるように秤量した後、ＢａＣＯ_３、ＣｕＯのみを８８０℃で３０時間保持する焼成をしてＢａＣｕＯ_２とＣｕＯの仮焼粉を得た（モル比でＢａＣｕＯ_２：ＣｕＯ＝２３：１０）。この仮焼粉とあらかじめ秤量しておいたＮｄ_２Ｏ_３と更に全体に対して０．５ｗｔ％のＲｈ粉末を加えて混合して８８０℃で１０時間保持する焼成を行い、その後平均粒径約１０μｍに粉砕した。次にこの仮焼粉を直径５３ｍｍ厚さ２８ｍｍのデイスク状に金型を用いて全圧２ｔｏｎ／ｃｍ^２で一軸プレス成形し、成形体を作製した。
【００１９】
次に、ＢａＳｎＯ_３の粉末をアルミナ基板上に外径５０ｍｍ厚さ２ｍｍとなるように桝を使用して敷き、前記成形体をこの敷き粉の上にのせてガス置換を行える炉の中に設置した。ロータリーポンプで０．１Ｔｏｒｒまで炉内を排気した後、大気圧になるまで酸素０．０１と窒素９９．９９％との混合ガスを流し込んだ。その後もこの混合ガスを０．５Ｌ／ｍｉｎの割合で流しながら以下の焼成工程を行った。
【００２０】
まず、１１５０℃で前記成形体を半溶融状態にした後、上部が低温側となるように５℃／ｃｍの温度勾配を加えて、成形体上部が１０７０℃となるまで１０℃／ｍｉｎで降温し、予め溶融法で作製しておいたＳｍ_１．８（Ｂａ_０．７５Ｓｒ_０．２５）_２．４Ｃｕ_３．４Ｏ_ｘ組成の種結晶を成長方向がｃ軸と平行になるように成形体の上部に接触させる。そこから０．５℃／ｈｒの速度で１０６５℃まで降温した後２０時間温度保持し、９６５℃まで１００時間で降温し、そこから室温まで２０時間かけて徐冷することによって結晶化を行った。
【００２１】
作製した試料は焼き縮みのために直径４５ｍｍ、厚さ２４ｍｍのデイスク状となっていた。結晶化した試料は別のガス置換を行える炉の中に設置される。まず、ロータリーポンプで０．１Ｔｏｒｒまで炉内を排気した後、酸素ガスを流し込んで酸素分圧が９５％以上である大気圧の酸素雰囲気にする。その後も０．５Ｌ／ｍｉｎの流量で酸素ガスを炉内に流しながら、室温から７００℃まで１０時間で昇温し、５０時間保持した後、４５０℃まで１００時間で降温しそこから２５０℃まで２００時間かけて徐冷し、２００℃から室温まで１０時間で降温させることにより超電導体材料を製造した。
【００２２】
得られた材料を育成方向（ディスク状試料の厚さ方向）に垂直に上から５ｍｍ間隔でスライス加工し、それぞれを均一に粉砕して滴定法により組成分析を行った。分析結果を図４に示す。中間層としてＢａＳｎＯ_３の粉末を用いたために、基盤との反応が抑えられ、且つＮｄ元素の過剰側に大きく組成ズレしていなかった。
【００２３】
次に、ミクロな部分の組織を観察するため、偏光顕微鏡及び電子線マイクロアナライザー（ＥＰＭＡ）でＮｄ、Ｂａ、Ｃｕのみの組成比を何点か分析したところ、実施例１とほぼ同様な組成の部分が同様な状態で観察された。
【００２４】
また、育成表面の目視による観察によって、異方位の核発生の形跡が無い部分を選んで、背面反射ラウエ法により材料表面の中心付近および端付近を３ｍｍ間隔で各３点ずつ結晶の方位を測定したところ、種結晶を反映していずれもほぼｃ軸に配向し、隣接する結晶間の方位のズレが２゜程度であった。さらに、目視によって観察される異方位の核発生は試料表面の少なくとも８０％以上について見られず、実質的に単結晶状の材料であることが確認された。
【００２５】
得られたディスク状材料を育成方向（ディスク状試料の厚さ方向）に上から垂直に上から５ｍｍ間隔でスライス加工し、中心付近における臨界温度（Ｔｃ）および外部磁場１Ｔ中の臨界電流密度を測定したところ、それぞれ図５のように厚さ方向に大きな組成ズレが無かったために、厚さ方向に上から１５ｍｍまで高い値を示していた。
【００２６】
（実施例３）
Ｓｍ_２Ｏ_３、ＢａＣＯ_３、ＣｕＯの各原料粉末をＳｍ：Ｂａ：Ｃｕ＝１８：２４：３４になるように秤量した後、ＢａＣＯ_３、ＣｕＯのみを８８０℃で３０時間保持する焼成をしてＢａＣｕＯ_２とＣｕＯの仮焼粉を得た（モル比でＢａＣｕＯ_２：ＣｕＯ＝２４：１０）。この仮焼粉とあらかじめ秤量しておいたＳｍ_２Ｏ_３と更に全体に対して０．５ｗｔ％のＰｔ粉末を加えて混合して８８０℃で１０時間保持する焼成を行い、その後平均粒径約１０μｍに粉砕した。
【００２７】
次に、この仮焼粉を直径５３ｍｍ厚さ２８ｍｍのデイスク状に金型を用いて全圧２ｔｏｎ／ｃｍ２で一軸プレス成形し、成形体を作製した。次に、ＢａＺｒＯ_３の粉末をアルミナ基板上に外径５０ｍｍ厚さ２ｍｍとなるように桝を使用して敷き、前記成形体をこの敷き粉の上にのせて、以下の焼成工程を行った。
【００２８】
まず、１１５０℃で前記成形体を半溶融状態にした後、上部が低温側となるように５℃／ｃｍの温度勾配を加えて、成形体上部が１０６５℃となるまで１０℃／ｍｉｎで降温し、予め溶融法で作製しておいたＳｍ_１．８（Ｂａ_０．７５Ｓｒ_０．２５）_２．４Ｃｕ_３．４Ｏ_ｘ組成の種結晶を成長方向がｃ軸と平行になるように成形体の上部に接触させる。そこから０．５℃／ｈｒの速度で１０６０℃まで降温した後２０時間温度保持し、９６０℃まで１００時間で降温し、そこから室温まで２０時間かけて徐冷することによって結晶化を行った。
【００２９】
作製した試料は焼き縮みのために直径４５ｍｍ、厚さ２４ｍｍのデイスク状となっていた。結晶化した試料は別のガス置換を行える炉の中に設置される。まず、ロータリーポンプで０．１Ｔｏｒｒまで炉内を排気した後、酸素ガスを流し込んで酸素分圧が９５％以上である大気圧の酸素雰囲気にする。その後も０．５Ｌ／ｍｉｎの流量で酸素ガスを炉内に流しながら、室温から４５０℃まで１０時間で昇温し、そこから２５０℃まで２００時間かけて徐冷し、２００℃から室温まで１０時間で降温させることにより超電導体材料を製造した。
【００３０】
得られた材料を育成方向（ディスク状試料の厚さ方向）に垂直に上から５ｍｍ間隔でスライス加工し、それぞれを均一に粉砕して滴定法により組成分析を行った。分析結果を図６に示す。中間層としてＢａＺｒＯ_３の粉末を用いたために、基盤との反応が抑えられ、且つＳｍ元素の過剰側に大きく組成ズレしていなかった。
【００３１】
次に、ミクロな部分の組織を観察するため、偏光顕微鏡及び電子線マイクロアナライザー（ＥＰＭＡ）でＳｍ、Ｂａ、Ｃｕのみの組成比を何点か分析したところ、モル比で図７のような組成の部分が確認された。これらのそれぞれはＥ相：ＳｍＢａ_２Ｃｕ_３Ｏ_６．８相、Ｆ相：Ｓｍ_０．９Ｂａ_２．１Ｃｕ_３Ｏ_６．７５相、Ｇ相：Ｓｍ_１．１Ｂａ_１．９Ｃｕ_３Ｏ_６．９相、Ｈ相：Ｓｍ_４Ｂａ_２Ｃｕ_２Ｏ_１０相であると考えられる。ここで、Ｈ相はＥ，Ｆ，Ｇ相中に０．１〜５０μｍ程度に微細に分散していた。
【００３２】
また、育成表面の目視による観察によって、異方位の核発生の形跡が無い部分を選んで、背面反射ラウエ法により材料表面の中心付近および端付近を３ｍｍ間隔で各３点ずつ結晶の方位を測定したところ、種結晶を反映していずれもほぼｃ軸に配向し、隣接する結晶間の方位のズレが２゜程度であった。さらに、目視によって観察される異方位の核発生は試料表面の少なくとも８０％以上について見られず、実質的に単結晶状の材料であることが確認された。
【００３３】
得られたディスク状材料を育成方向（ディスク状試料の厚さ方向）に垂直に上から５ｍｍ間隔でスライス加工し、中心付近における臨界温度（Ｔｃ）および外部磁場１Ｔ中の臨界電流密度を測定したところ、それぞれ図８のように厚さ方向に大きな組成ズレが無かったために、厚さ方向に上から１５ｍｍまで高い値を示していた。
【００３４】
（実施例４）
Ｎｄ_２Ｏ_３、ＢａＣＯ_３、ＣｕＯの各原料粉末をＮｄ：Ｂａ：Ｃｕ＝１８：２４：３４になるように秤量した後、ＢａＣＯ_３、ＣｕＯのみを８８０℃で３０時間保持する焼成をしてＢａＣｕＯ_２とＣｕＯの仮焼粉を得た（モル比でＢａＣｕＯ_２：ＣｕＯ＝２４：１０）。この仮焼粉とあらかじめ秤量しておいたＮｄ_２Ｏ_３と更に全体に対して０．５ｗｔ％のＰｔ粉末及び１０ｗｔ％のＡｇ粉末を加えて混合して８８０℃で１０時間保持する焼成を行い、その後平均粒径約１０μｍに粉砕した。
【００３５】
次に、この仮焼粉を直径５３ｍｍ厚さ２８ｍｍのデイスク状に金型を用いて全圧２ｔｏｎ／ｃｍ２で一軸プレス成形し、成形体を作製した。次に、ＢａＺｒＯ_３の粉末をアルミナ基板上に外径５０ｍｍ厚さ２ｍｍとなるように桝を使用して敷き、前記成形体をこの敷き粉の上にのせて、以下の焼成工程を行った。
【００３６】
まず、１１００℃で前記成形体を半溶融状態にした後、上部が低温側となるように５℃／ｃｍの温度勾配を加えて、成形体上部が１０２５℃となるまで１０℃／ｍｉｎで降温し、予め溶融法で作製しておいたＮｄ_１．８Ｂａ_２．４Ｃｕ_３．４Ｏ_ｘ組成の種結晶を成長方向がｃ軸と平行になるように成形体の上部に接触させる。そこから０．５℃／ｈｒの速度で１０２０℃まで降温した後２０時間温度保持し、９２０℃まで１００時間で降温し、そこから室温まで２０時間かけて徐冷することによって結晶化を行った。
【００３７】
作製した試料は焼き縮みのために直径４５ｍｍ、厚さ２４ｍｍのデイスク状となっていた。結晶化した試料は別のガス置換を行える炉の中に設置される。まず、ロータリーポンプで０．１Ｔｏｒｒまで炉内を排気した後、酸素ガスを流し込んで酸素分圧が９５％以上である大気圧の酸素雰囲気にする。その後も０．５Ｌ／ｍｉｎの流量で酸素ガスを炉内に流しながら、室温から７００℃まで１０時間で昇温し、５０時間保持した後、４５０℃まで１００時間で降温しそこから２５０℃まで２００時間かけて徐冷し、２００℃から室温まで１０時間で降温させることにより超電導体材料を製造した。
【００３８】
得られた材料を育成方向（ディスク状試料の厚さ方向）に垂直に上から５ｍｍ間隔でスライス加工し、それぞれを均一に粉砕して滴定法により組成分析を行った。分析結果を図９に示す。中間層としてＢａＺｒＯ_３の粉末を用いたために、基盤との反応が抑えられ、且つＮｄ元素の過剰側に大きく組成ズレしていなかった。
【００３９】
次に、ミクロな部分の組織を観察するため、偏光顕微鏡及び電子線マイクロアナライザー（ＥＰＭＡ）でＮｄ、Ｂａ、Ｃｕのみの組成比を何点か分析したところ、実施例１とほぼ同様な組成の部分が同様な状態で観察された。さらに０．１〜１００μｍ程度のＡｇ粒子が微細に分散していた。
【００４０】
また、育成表面の目視による観察によって、異方位の核発生の形跡が無い部分を選んで、背面反射ラウエ法により材料表面の中心付近および端付近を３ｍｍ間隔で各３点ずつ結晶の方位を測定したところ、種結晶を反映していずれもほぼｃ軸に配向し、隣接する結晶間の方位のズレが２゜程度であった。さらに、目視によって観察される異方位の核発生は試料表面の少なくとも８０％以上について見られず、実質的に単結晶状の材料であることが確認された。
【００４１】
得られたディスク状材料を育成方向（ディスク状試料の厚さ方向）に垂直に上から５ｍｍ間隔でスライス加工し、中心付近における臨界温度（Ｔｃ）および外部磁場１Ｔ中の臨界電流密度を測定したところ、それぞれ図１０のように厚さ方向に大きな組成ズレが無かったために、厚さ方向に上から15mmまで高い値を示していた。
【００４２】
（比較例１）
Ｎｄ_２Ｏ_３、ＢａＣＯ_３、ＣｕＯの各原料粉末をＮｄ：Ｂａ：Ｃｕ＝１８：２４：３４になるように秤量した後、ＢａＣＯ_３、ＣｕＯのみを８８０℃で３０時間焼成してＢａＣｕＯ２とＣｕＯの仮焼粉を得た（モル比でＢａＣｕＯ_２：ＣｕＯ＝２４：１０）。この仮焼粉とあらかじめ秤量しておいたＮｄ_２Ｏ_３と更に全体に対して０．５ｗｔ％のＰｔ粉末を加えて混合して８８０℃で再度焼成し、その後平均粒径約１０μｍに粉砕した。
【００４３】
次に、この仮焼粉を直径５３ｍｍ厚さ２８ｍｍのデイスク状に金型を用いて全圧２ｔｏｎ／ｃｍ^２で一軸プレス成形し、成形体を作製した。この成形体を直接アルミナ基板上にのせてガス置換を行える炉の中に設置した。ロータリーポンプで０．１Ｔｏｒｒまで炉内を排気した後、大気圧になるまで酸素０．０１％と窒素９９．９９％との混合ガスを流し込んだ。その後もこの混合ガスを0.5L/minの割合で流しながら以下の焼成工程を行った。
【００４４】
まず、１１５０℃で前記成形体を半溶融状態にした後、上部が低温側となるように５℃／ｃｍの温度勾配を加えて、成形体上部が１０７０℃となるまで１０℃／ｍｉｎで降温し、予め溶融法で作製しておいたＳｍ_１．８（Ｂａ_０．７５Ｓｒ_０．２５）_２．４Ｃｕ_３．４Ｏ_ｘ組成の種結晶を成長方向がｃ軸と平行になるように成形体の上部に接触させる。そこから０．５℃／ｈｒの速度で１０６５℃まで降温した後２０時間温度保持し、９６５℃まで１００時間で降温し、そこから室温まで２０時間かけて徐冷することによって結晶化を行った。
【００４５】
作製した試料は焼き縮みのために直径４５ｍｍ、厚さ２４ｍｍのデイスク状となっていた。結晶化した試料は別のガス置換を行える炉の中に設置される。まず、ロータリーポンプで０．１Ｔｏｒｒまで炉内を排気した後、酸素ガスを流し込んで酸素分圧が９５％以上である大気圧の酸素雰囲気にする。その後も０．５Ｌ／ｍｉｎの流量で酸素ガスを炉内に流しながら、室温から７００℃まで１０時間で昇温し、５０時間保持した後、４５０℃まで１００時間で降温しそこから２５０℃まで２００時間かけて徐冷し、２００℃から室温まで１０時間で降温させることにより超電導体材料を製造した。
【００４６】
得られた材料を育成方向（ディスク状試料の厚さ方向）に垂直に上から５ｍｍ間隔でスライス加工し、それぞれを均一に粉砕して滴定法により組成分析を行った。分析結果を図１１に示す。中間層を使用しなかったたために、基盤との反応が激しく起こり、Ｎｄ元素の過剰側に大きく組成ズレしていた。
【００４７】
次に、ミクロな部分の組織を観察するため、偏光顕微鏡及び電子線マイクロアナライザー（ＥＰＭＡ）でＮｄ、Ｂａ、Ｃｕのみの組成比を何点か分析したところ、実施例１とほぼ同様な組成の部分が同様な状態で観察された。
【００４８】
また、育成表面の目視による観察によって、異方位の核発生の形跡が無い部分を選んで、背面反射ラウエ法により材料表面の中心付近および端付近を３ｍｍ間隔で各３点ずつ結晶の方位を測定したところ、種結晶を反映していずれもほぼｃ軸に配向し、隣接する結晶間の方位のズレが２゜程度であった。さらに、目視によって観察される異方位の核発生は試料表面の少なくとも８０％以上について見られず、実質的に単結晶状の材料であることが確認された。
【００４９】
しかしながら、得られたディスク状材料を育成方向（ディスク状試料の厚さ方向）に垂直に上から５ｍｍ間隔でスライス加工し、中心付近における臨界温度（Ｔｃ）および外部磁場１Ｔ中の臨界電流密度を測定したところ、それぞれ図１２のように厚さ方向に大きな組成ズレがあったために、試料上部から厚さ方向に上から１５ｍｍまで高い値を示していた。
【００５０】
【発明の効果】
以上詳述したように、本発明は、ＲＥ化合物（ＲＥはＹを含む希土類元素）、Ｂａ化合物及びＣｕ化合物を含む原料混合体に、少なくとも該原料混合体の融点より高い温度領域における焼成工程を含む処理を施してＲＥーＢａーＣｕーＯ系酸化物超電導体を製造する酸化物超電導体の製造方法において、前記原料混合体を成形した成形体を支えるために該原料混合体に直接接触する介在物がＢａ化合物で構成されていて、且つ該介在物中にＲＥ元素（ＲＥはＹを含む希土類元素）を５０モル％以上含まない材料を用いることにより、基盤との反応を抑制し、組成ズレのない大型で高特性の酸化物超電導体を歩留まり良く製造することを可能にした。
【図面の簡単な説明】
【図１】実施例１で製造した材料の厚さ方向の組成分析結果を示す表である。
【図２】実施例１で製造した試料中に存在する主な結晶相を偏光顕微鏡及び電子線マイクロアナライザー（ＥＰＭＡ）によって分析した結果を示す表である。
【図３】実施例１で製造した試料の臨界温度（Ｔｃ）及び臨界電流密度の測定結果を示す表である。
【図４】実施例２で製造した試料の厚さ方向の組成分析結果を示す表である。
【図５】実施例２で製造した試料の臨界温度（Ｔｃ）及び臨界電流密度の測定結果を示す表である。
【図６】実施例３で製造した試料の厚さ方向の組成分析結果を示す表である。
【図７】実施例３で製造した試料中に存在する主な結晶相を偏光顕微鏡及び電子線マイクロアナライザー（ＥＰＭＡ）によって分析した結果を示す表である。
【図８】実施例３で製造した試料の臨界温度（Ｔｃ）及び臨界電流密度の測定結果を示す表である。
【図９】実施例４で製造した試料中に存在する主な結晶相を偏光顕微鏡及び電子線マイクロアナライザー（ＥＰＭＡ）によって分析した結果を示す表である。
【図１０】実施例４で製造した試料の臨界温度（Ｔｃ）及び臨界電流密度の測定結果を示す表である。
【図１１】比較例１で製造した試料の厚さ方向の組成分析結果を示す表である。
【図１２】比較例１で製造した試料の臨界温度（Ｔｃ）及び臨界電流密度の測定結果を示す表である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an oxide superconducting member, and more particularly to an oxide superconductor having a high critical current density even in a high magnetic field used for a current lead, a magnetic bearing, a magnetic shield, a bulk magnet, and the like, and a method for manufacturing the same. It is.
[0002]
[Prior art]
Conventionally, as a method of manufacturing this kind of oxide superconductor, there has been a method as shown in Japanese Patent Application No. 6-229416 as a method of suppressing reaction with the substrate by an intermediate material. This is because a raw material mixture in which RE, Ba, and Cu compounds are mixed at a predetermined molar ratio is calcined, press-molded, and then subjected to a process including a firing step at least in a temperature region higher than the melting point of the molded body. In the case of manufacturing a RE-Ba-Cu-O-based oxide superconductor, inclusions that are in direct contact with the molded body in order to support the molded body in the firing step are at least RE (RE is a rare earth element including Y). Is formed of a material that does not contain raw materials other than the elements for forming the superconductor as a main element except for the RE, thereby forming a molded body, a molded body, and inclusions. It is possible to suppress the reaction with the supporting substrate and prevent mutual diffusion.
[0003]
[Problems to be solved by the invention]
However, according to the above method, the composition of the oxide superconductor to be manufactured inevitably shifts to the excess side of the RE element. Then, when this method is performed using an RE element having a relatively large ionic radius, there is a disadvantage that the RE element is excessively substituted at the Ba site and the superconducting characteristics are remarkably deteriorated.
[0004]
The present invention has been made under the above-mentioned background. Even when an RE element having a relatively large ionic radius is used, a large oxide superconductor having higher critical current density characteristics and a method for manufacturing the same The purpose is to provide.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, the oxide superconductor according to the present invention is:
(Configuration 1) An RE element (RE) oriented so that a deviation in orientation between RE-Ba-Cu-O-based superconducting crystals is ± 5 ° or less, and having an average direction in the c-axis direction of the superconducting crystals. Is a composition deviation of a rare earth element including Y) within ± 1.5 mol% over a thickness of 15 mm or more in the direction (however, the composition is represented by a molar ratio of only RE, Ba, and Cu). And
[0006]
In addition, the method for producing the oxide superconductor according to the present invention includes:
(Configuration 2) A raw material mixture containing an RE compound (RE is a rare earth element including Y), a Ba compound and a Cu compound is subjected to a treatment including a firing step in a temperature range higher than the melting point of the raw material mixture. In the method for producing an oxide superconductor for producing a Ba-Cu-O-based oxide superconductor,
In order to support the raw material mixture in the firing step, inclusions that are in direct contact with the raw material mixture are composed of Ba compounds, and 50 RE elements (RE is a rare earth element including Y) are included in the inclusions. It is characterized by not containing more than mol%,
As an aspect of this configuration 2,
(Configuration 3) In the method for manufacturing the oxide superconductor of Configuration 2,
The Ba compound is BaZrO. ₃ , BaSnO ₃ Or BaPtO ₃ It is characterized by
(Claim 4) In the manufacturing method of the oxide superconductor of composition 2 or 3,
Further adding 0.05 to 5 wt% of one or more elements of Pt, Rh, and Ce metals or each compound (in the case of a compound, indicated by the element weight of only the metal) to the raw material mixture As a feature,
(Configuration 5) In the method for producing an oxide superconductor according to any one of configurations 2 to 4,
1 to 60 wt% of Ag metal or compound is further added to the raw material mixture by the weight of Ag element component only,
(Claim 6) In the method for producing an oxide superconductor according to any one of Structures 2 to 5,
The oxygen partial pressure is P0 = 2 × 10 ^-1 After melting at a temperature of partially melting as ˜1 atm or more, it is cooled to room temperature while adding a holding and gradual cooling process as necessary.
[0007]
According to the above configuration, the deviation of the orientation between the superconducting crystals is ± 5 ° or less, and the composition deviation of the RE element in the c-axis direction of the superconducting crystal is ± 1.5 mol% over a thickness of 15 mm or more. Therefore, an oxide superconductor having a very high critical current density can be obtained.
[0008]
In this case, when a RE-Ba-Cu-O-based superconductor is baked at a temperature equal to or higher than the melting point of the superconductor on a substrate such as alumina or MgO as in the prior art, it reacts violently with the substrate, resulting in a Ba site or Cu site. Substitution of Mg or Al occurs in the composition, and the composition shifts to a smaller amount of Ba and Cu. Therefore, the composition shifts to the excess side of the RE element as a whole. Furthermore, in order to obtain a crystal oriented in the c-axis, when a temperature gradient is applied to the sample and a seed crystal is brought into contact with the upper part of the sample and crystallization is performed in one direction from the upper part of the sample, the lower part of the sample is relatively in a molten state. Therefore, the reaction with the substrate occurs particularly vigorously, and composition deviation occurs so as to have a composition gradient in the c-axis direction. Then, in the case of the RE element having a relatively large ionic radius, the RE element is close to the ionic radius of Ba, so that the RE element is excessively replaced with the Ba site, and the superconducting characteristics are remarkably deteriorated. Therefore, in the present invention, by using a powder, a molded body, and a sintered body made of a Ba compound as an intermediate phase between the superconductor and the substrate, the decrease in Ba is suppressed and the composition of the RE is relatively increased. The deviation is also suppressed, and a superconductor having a higher critical current density can be obtained. As this Ba compound, BaZrO ₃ In addition to BaSnO ₃ , BaPtO ₃ Etc. can be mentioned.
[0009]
Furthermore, when Ag is finely dispersed in the crystal, microcracks are reduced, and magnetic properties, mechanical strength, and water resistance are improved. In this case, the effect is low below 1 wt%, and if it exceeds 60 wt%, the superconducting current hardly flows and the characteristics are deteriorated.
[0010]
Example 1
Nd ₂ O ₃ , BaCO ₃ , CuO raw powders were weighed so that Nd: Ba: Cu = 18: 24: 34, and then BaCO ₃ BaCuO is fired by holding only CuO at 880 ° C. for 30 hours. ₂ And CuO calcined powder was obtained (in terms of molar ratio BaCuO ₂ : CuO = 24: 10). This calcined powder and Nd weighed in advance ₂ O ₃ Further, 0.5 wt% Pt powder was added to the whole and mixed, followed by baking at 880 ° C. for 10 hours, and then pulverized to an average particle size of about 10 μm. Next, this calcined powder is formed into a disk shape having a diameter of 53 mm and a thickness of 28 mm using a mold, and the total pressure is 2 ton / cm. ² Was uniaxial press-molded to produce a compact.
[0011]
Next, BaZrO ₃ Was placed on an alumina substrate using a scissors so that the outer diameter was 50 mm and the thickness was 2 mm, and the molded body was placed on the floor powder and placed in a furnace capable of gas replacement. After evacuating the inside of the furnace to 0.1 Torr with a rotary pump, a mixed gas of oxygen 0.01% and nitrogen 99.99% was flowed to atmospheric pressure. Thereafter, the following firing process was performed while flowing the mixed gas at a rate of 0.5 L / min.
[0012]
First, after the molded body was made into a semi-molten state at 1150 ° C., a temperature gradient of 5 ° C./cm was applied so that the upper part was on the low temperature side, and the temperature was lowered at 10 ° C./min until the upper part of the molded body reached 1070 ° C. Sm prepared in advance by the melting method _1.8 (Ba _0.75 Sr _0.25 ) _2.4 Cu _3.4 O _x The seed crystal of the composition is brought into contact with the upper part of the compact so that the growth direction is parallel to the c-axis. Then, the temperature was lowered to 1065 ° C. at a rate of 0.5 ° C./hr, held for 20 hours, lowered to 965 ° C. in 100 hours, and then gradually cooled to room temperature over 20 hours for crystallization. .
[0013]
The produced sample was disk-shaped having a diameter of 45 mm and a thickness of 24 mm due to shrinkage by baking. The crystallized sample is placed in a furnace where another gas replacement is possible. First, the inside of the furnace is evacuated to 0.1 Torr with a rotary pump, and then an oxygen gas is flowed into an atmospheric pressure oxygen atmosphere having an oxygen partial pressure of 95% or more. After that, while oxygen gas was flowed into the furnace at a flow rate of 0.5 L / min, the temperature was raised from room temperature to 700 ° C. in 10 hours, held for 50 hours, then lowered to 450 ° C. in 100 hours and then to 250 ° C. The superconductor material was manufactured by gradually cooling over 200 hours and lowering the temperature from 200 ° C. to room temperature in 10 hours.
[0014]
The obtained material was sliced at intervals of 5 mm perpendicularly to the growth direction (thickness direction of the disk-shaped sample), and each was pulverized uniformly and subjected to composition analysis by a titration method. The analysis results are shown in FIG. BaZrO as an intermediate layer ₃ Therefore, the reaction with the substrate was suppressed, and the composition was not greatly shifted to the excess side of the Nd element.
[0015]
Next, in order to observe the microstructure of the micro portion, the composition ratio of only Nd, Ba, and Cu was analyzed with a polarizing microscope and an electron beam microanalyzer (EPMA). The part of was confirmed. Each of these is A phase: NdBa ₂ Cu ₃ O _6.8 Phase, B phase: Nd _0.9 Ba _2.1 Cu ₃ O _6.75 Phase, C phase: Nd _1.1 Ba _1.9 Cu ₃ O _6.9 Phase, D phase: Nd ₄ Ba ₂ Cu ₂ O ₁₀ Is considered a phase. Here, the D phase was finely dispersed in the A, B, and C phases to about 0.1 to 50 μm.
[0016]
Also, by visually observing the growth surface, select the part where there is no evidence of nucleation of different orientations, and measure the crystal orientation by 3 points at 3 mm intervals near the center and edge of the material surface by the back reflection Laue method. As a result, all of them were oriented in the c-axis reflecting the seed crystal, and the deviation of the orientation between adjacent crystals was about 2 °. Furthermore, nucleation of different orientations observed visually was not observed on at least 80% or more of the sample surface, and it was confirmed that the material was substantially a single crystal material.
[0017]
The obtained disk-shaped material was sliced at intervals of 5 mm perpendicularly to the growth direction (thickness direction of the disk-shaped sample), and the critical temperature (Tc) near the center and the critical current density in the external magnetic field 1T were measured. However, since there was no large compositional deviation in the thickness direction as shown in FIG. 3, the values were high up to 15 mm from the top in the thickness direction.
[0018]
(Example 2)
Nd ₂ O ₃ , BaCO ₃ , CuO raw powders were weighed so that Nd: Ba: Cu = 14: 23: 32, and then BaCO ₃ BaCuO is fired by holding only CuO at 880 ° C. for 30 hours. ₂ And CuO calcined powder was obtained (in terms of molar ratio BaCuO ₂ : CuO = 23: 10). This calcined powder and Nd weighed in advance ₂ O ₃ Further, 0.5 wt% Rh powder was added to the whole and mixed, followed by baking at 880 ° C. for 10 hours, and then pulverized to an average particle size of about 10 μm. Next, this calcined powder is formed into a disk shape having a diameter of 53 mm and a thickness of 28 mm using a mold, and the total pressure is 2 ton / cm. ² Was uniaxial press-molded to produce a compact.
[0019]
Next, BaSnO ₃ Was placed on an alumina substrate using a scissors so that the outer diameter was 50 mm and the thickness was 2 mm, and the molded body was placed on the floor powder and placed in a furnace capable of gas replacement. After exhausting the inside of the furnace to 0.1 Torr with a rotary pump, a mixed gas of oxygen 0.01 and nitrogen 99.99% was flowed until atmospheric pressure was reached. Thereafter, the following firing process was performed while flowing the mixed gas at a rate of 0.5 L / min.
[0020]
First, after the molded body was made into a semi-molten state at 1150 ° C., a temperature gradient of 5 ° C./cm was applied so that the upper part was on the low temperature side, and the temperature was lowered at 10 ° C./min until the upper part of the molded body reached 1070 ° C. Sm prepared in advance by the melting method _1.8 (Ba _0.75 Sr _0.25 ) _2.4 Cu _3.4 O _x The seed crystal of the composition is brought into contact with the upper part of the compact so that the growth direction is parallel to the c-axis. Then, the temperature was lowered to 1065 ° C. at a rate of 0.5 ° C./hr, held for 20 hours, lowered to 965 ° C. in 100 hours, and then gradually cooled to room temperature over 20 hours for crystallization. .
[0021]
The produced sample was disk-shaped having a diameter of 45 mm and a thickness of 24 mm due to shrinkage by baking. The crystallized sample is placed in a furnace where another gas replacement is possible. First, the inside of the furnace is evacuated to 0.1 Torr with a rotary pump, and then an oxygen gas is flowed into an atmospheric pressure oxygen atmosphere having an oxygen partial pressure of 95% or more. After that, while oxygen gas was flowed into the furnace at a flow rate of 0.5 L / min, the temperature was raised from room temperature to 700 ° C. in 10 hours, held for 50 hours, then lowered to 450 ° C. in 100 hours and then to 250 ° C. The superconductor material was manufactured by gradually cooling over 200 hours and lowering the temperature from 200 ° C. to room temperature in 10 hours.
[0022]
The obtained material was sliced at intervals of 5 mm perpendicularly to the growth direction (thickness direction of the disk-shaped sample), and each was pulverized uniformly and subjected to composition analysis by a titration method. The analysis results are shown in FIG. BaSnO as intermediate layer ₃ Therefore, the reaction with the substrate was suppressed, and the composition was not greatly shifted to the excess side of the Nd element.
[0023]
Next, in order to observe the microstructure of the micro portion, the composition ratio of only Nd, Ba, and Cu was analyzed with a polarizing microscope and an electron beam microanalyzer (EPMA). Parts were observed in a similar state.
[0024]
Also, by visually observing the growth surface, select the part where there is no evidence of nucleation of different orientations, and measure the crystal orientation by 3 points at 3 mm intervals near the center and edge of the material surface by the back reflection Laue method. As a result, all of them were oriented in the c-axis reflecting the seed crystal, and the deviation of the orientation between adjacent crystals was about 2 °. Furthermore, nucleation of different orientations observed visually was not observed on at least 80% or more of the sample surface, and it was confirmed that the material was substantially a single crystal material.
[0025]
The obtained disk-shaped material is sliced at an interval of 5 mm vertically from above in the growth direction (thickness direction of the disk-shaped sample), and the critical temperature (Tc) near the center and the critical current density in the external magnetic field 1T are determined. As a result of measurement, there was no large compositional deviation in the thickness direction as shown in FIG. 5, and thus a high value from the top to 15 mm was shown in the thickness direction.
[0026]
Example 3
Sm ₂ O ₃ , BaCO ₃ , CuO raw powders were weighed so that Sm: Ba: Cu = 18: 24: 34, and then BaCO ₃ BaCuO is fired by holding only CuO at 880 ° C. for 30 hours. ₂ And CuO calcined powder was obtained (in terms of molar ratio BaCuO ₂ : CuO = 24: 10). Sm previously weighed with this calcined powder ₂ O ₃ Further, 0.5 wt% Pt powder was added to the whole and mixed, followed by baking at 880 ° C. for 10 hours, and then pulverized to an average particle size of about 10 μm.
[0027]
Next, this calcined powder was uniaxially press-molded into a disk shape having a diameter of 53 mm and a thickness of 28 mm using a mold at a total pressure of 2 ton / cm 2 to produce a compact. Next, BaZrO ₃ The powder was spread on an alumina substrate using a scissors so that the outer diameter was 50 mm and the thickness was 2 mm, and the molded body was placed on the spread powder, and the following firing process was performed.
[0028]
First, after the molded body was made into a semi-molten state at 1150 ° C., a temperature gradient of 5 ° C./cm was applied so that the upper part was on the low temperature side, and the temperature was lowered at 10 ° C./min until the upper part of the molded body reached 1065 ° C. Sm prepared in advance by the melting method _1.8 (Ba _0.75 Sr _0.25 ) _2.4 Cu _3.4 O _x The seed crystal of the composition is brought into contact with the upper part of the compact so that the growth direction is parallel to the c-axis. Then, the temperature was lowered to 1060 ° C. at a rate of 0.5 ° C./hr, held for 20 hours, lowered to 960 ° C. in 100 hours, and then gradually cooled to room temperature over 20 hours for crystallization. .
[0029]
The produced sample was disk-shaped having a diameter of 45 mm and a thickness of 24 mm due to shrinkage by baking. The crystallized sample is placed in a furnace where another gas replacement is possible. First, the inside of the furnace is evacuated to 0.1 Torr with a rotary pump, and then an oxygen gas is flowed into an atmospheric pressure oxygen atmosphere having an oxygen partial pressure of 95% or more. Thereafter, while oxygen gas is flowed into the furnace at a flow rate of 0.5 L / min, the temperature is raised from room temperature to 450 ° C. over 10 hours, and then gradually cooled to 250 ° C. over 200 hours. The superconductor material was manufactured by lowering the temperature over time.
[0030]
The obtained material was sliced at intervals of 5 mm perpendicularly to the growth direction (thickness direction of the disk-shaped sample), and each was pulverized uniformly and subjected to composition analysis by a titration method. The analysis results are shown in FIG. BaZrO as an intermediate layer ₃ Therefore, the reaction with the substrate was suppressed, and the composition was not significantly shifted to the excess side of the Sm element.
[0031]
Next, in order to observe the structure of the micro portion, the composition ratio of only Sm, Ba, and Cu was analyzed with a polarizing microscope and an electron beam microanalyzer (EPMA). The part of was confirmed. Each of these is phase E: SmBa ₂ Cu ₃ O _6.8 Phase, F phase: Sm _0.9 Ba _2.1 Cu ₃ O _6.75 Phase, G phase: Sm _1.1 Ba _1.9 Cu ₃ O _6.9 Phase, H phase: Sm ₄ Ba ₂ Cu ₂ O ₁₀ Is considered a phase. Here, the H phase was finely dispersed in the E, F, and G phases to about 0.1 to 50 μm.
[0032]
Also, by visually observing the growth surface, select the part where there is no evidence of nucleation of different orientations, and measure the crystal orientation by 3 points at 3 mm intervals near the center and edge of the material surface by the back reflection Laue method. As a result, all of them were oriented in the c-axis reflecting the seed crystal, and the deviation of the orientation between adjacent crystals was about 2 °. Furthermore, nucleation of different orientations observed visually was not observed on at least 80% or more of the sample surface, and it was confirmed that the material was substantially a single crystal material.
[0033]
The obtained disk-shaped material was sliced at intervals of 5 mm perpendicularly to the growth direction (thickness direction of the disk-shaped sample), and the critical temperature (Tc) near the center and the critical current density in the external magnetic field 1T were measured. However, since there was no large compositional deviation in the thickness direction as shown in FIG. 8, a high value from the top to 15 mm was shown in the thickness direction.
[0034]
Example 4
Nd ₂ O ₃ , BaCO ₃ , CuO raw powders were weighed so that Nd: Ba: Cu = 18: 24: 34, and then BaCO ₃ BaCuO is fired by holding only CuO at 880 ° C. for 30 hours. ₂ And CuO calcined powder was obtained (in terms of molar ratio BaCuO ₂ : CuO = 24: 10). This calcined powder and Nd weighed in advance ₂ O ₃ Further, 0.5 wt% Pt powder and 10 wt% Ag powder were added to the whole, mixed and fired by holding at 880 ° C. for 10 hours, and then pulverized to an average particle size of about 10 μm.
[0035]
Next, this calcined powder was uniaxially press-molded into a disk shape having a diameter of 53 mm and a thickness of 28 mm using a mold at a total pressure of 2 ton / cm 2 to produce a compact. Next, BaZrO ₃ The powder was spread on an alumina substrate using a scissors so that the outer diameter was 50 mm and the thickness was 2 mm, and the molded body was placed on the spread powder, and the following firing process was performed.
[0036]
First, after the molded body was made into a semi-molten state at 1100 ° C., a temperature gradient of 5 ° C./cm was applied so that the upper part was on the low temperature side, and the temperature was lowered at 10 ° C./min until the upper part of the molded body reached 1025 ° C. Nd previously prepared by the melting method _1.8 Ba _2.4 Cu _3.4 O _x The seed crystal of the composition is brought into contact with the upper part of the compact so that the growth direction is parallel to the c-axis. From there, the temperature was lowered to 1020 ° C. at a rate of 0.5 ° C./hr, held for 20 hours, lowered to 920 ° C. in 100 hours, and then gradually cooled to room temperature over 20 hours for crystallization. .
[0037]
The produced sample was disk-shaped having a diameter of 45 mm and a thickness of 24 mm due to shrinkage by baking. The crystallized sample is placed in a furnace where another gas replacement is possible. First, the inside of the furnace is evacuated to 0.1 Torr with a rotary pump, and then an oxygen gas is flowed into an atmospheric pressure oxygen atmosphere having an oxygen partial pressure of 95% or more. After that, while oxygen gas was flowed into the furnace at a flow rate of 0.5 L / min, the temperature was raised from room temperature to 700 ° C. in 10 hours, held for 50 hours, then lowered to 450 ° C. in 100 hours and then to 250 ° C. The superconductor material was manufactured by gradually cooling over 200 hours and lowering the temperature from 200 ° C. to room temperature in 10 hours.
[0038]
The obtained material was sliced at intervals of 5 mm perpendicularly to the growth direction (thickness direction of the disk-shaped sample), and each was pulverized uniformly and subjected to composition analysis by a titration method. The analysis results are shown in FIG. BaZrO as an intermediate layer ₃ Therefore, the reaction with the substrate was suppressed, and the composition was not greatly shifted to the excess side of the Nd element.
[0039]
Next, in order to observe the microstructure of the micro portion, the composition ratio of only Nd, Ba, and Cu was analyzed with a polarizing microscope and an electron beam microanalyzer (EPMA). Parts were observed in a similar state. Further, Ag particles of about 0.1 to 100 μm were finely dispersed.
[0040]
Also, by visually observing the growth surface, select the part where there is no evidence of nucleation of different orientations, and measure the crystal orientation by 3 points at 3 mm intervals near the center and edge of the material surface by the back reflection Laue method. As a result, all of them were oriented in the c-axis reflecting the seed crystal, and the deviation of the orientation between adjacent crystals was about 2 °. Furthermore, nucleation of different orientations observed visually was not observed on at least 80% or more of the sample surface, and it was confirmed that the material was substantially a single crystal material.
[0041]
The obtained disk-shaped material was sliced at intervals of 5 mm perpendicularly to the growth direction (thickness direction of the disk-shaped sample), and the critical temperature (Tc) near the center and the critical current density in the external magnetic field 1T were measured. However, since there was no large compositional deviation in the thickness direction as shown in FIG. 10, the values were high up to 15 mm from the top in the thickness direction.
[0042]
(Comparative Example 1)
Nd ₂ O ₃ , BaCO ₃ , CuO raw powders were weighed so that Nd: Ba: Cu = 18: 24: 34, and then BaCO ₃ Then, only CuO was calcined at 880 ° C. for 30 hours to obtain BaCuO 2 and CuO calcined powder (in terms of molar ratio BaCuO ₂ : CuO = 24: 10). This calcined powder and Nd weighed in advance ₂ O ₃ Further, 0.5 wt% Pt powder was added to the whole, mixed, fired again at 880 ° C., and then pulverized to an average particle size of about 10 μm.
[0043]
Next, the calcined powder is formed into a disk shape having a diameter of 53 mm and a thickness of 28 mm using a mold, and the total pressure is 2 ton / cm. ² Was uniaxial press-molded to produce a compact. This compact was placed directly on an alumina substrate and placed in a furnace capable of gas replacement. After exhausting the inside of the furnace to 0.1 Torr with a rotary pump, a mixed gas of oxygen 0.01% and nitrogen 99.99% was flowed until atmospheric pressure was reached. Thereafter, the following firing step was performed while flowing the mixed gas at a rate of 0.5 L / min.
[0044]
First, after the molded body was made into a semi-molten state at 1150 ° C., a temperature gradient of 5 ° C./cm was applied so that the upper part was on the low temperature side, and the temperature was lowered at 10 ° C./min until the upper part of the molded body reached 1070 ° C. Sm prepared in advance by the melting method _1.8 (Ba _0.75 Sr _0.25 ) _2.4 Cu _3.4 O _x The seed crystal of the composition is brought into contact with the upper part of the compact so that the growth direction is parallel to the c-axis. Then, the temperature was lowered to 1065 ° C. at a rate of 0.5 ° C./hr, held for 20 hours, lowered to 965 ° C. in 100 hours, and then gradually cooled to room temperature over 20 hours for crystallization. .
[0045]
The produced sample was disk-shaped having a diameter of 45 mm and a thickness of 24 mm due to shrinkage by baking. The crystallized sample is placed in a furnace where another gas replacement is possible. First, the inside of the furnace is evacuated to 0.1 Torr with a rotary pump, and then an oxygen gas is flowed into an atmospheric pressure oxygen atmosphere having an oxygen partial pressure of 95% or more. After that, while oxygen gas was flowed into the furnace at a flow rate of 0.5 L / min, the temperature was raised from room temperature to 700 ° C. in 10 hours, held for 50 hours, then lowered to 450 ° C. in 100 hours and then to 250 ° C. The superconductor material was manufactured by gradually cooling over 200 hours and lowering the temperature from 200 ° C. to room temperature in 10 hours.
[0046]
The obtained material was sliced at intervals of 5 mm perpendicularly to the growth direction (thickness direction of the disk-shaped sample), and each was pulverized uniformly and subjected to composition analysis by a titration method. The analysis results are shown in FIG. Since the intermediate layer was not used, the reaction with the substrate occurred vigorously, and the composition was greatly shifted to the excess side of the Nd element.
[0047]
Next, in order to observe the microstructure of the micro portion, the composition ratio of only Nd, Ba, and Cu was analyzed with a polarizing microscope and an electron beam microanalyzer (EPMA). Parts were observed in a similar state.
[0048]
Also, by visually observing the growth surface, select the part where there is no evidence of nucleation of different orientations, and measure the crystal orientation by 3 points at 3 mm intervals near the center and edge of the material surface by the back reflection Laue method. As a result, all of them were oriented in the c-axis reflecting the seed crystal, and the deviation of the orientation between adjacent crystals was about 2 °. Furthermore, nucleation of different orientations observed visually was not observed on at least 80% or more of the sample surface, and it was confirmed that the material was substantially a single crystal material.
[0049]
However, the obtained disk-shaped material is sliced at intervals of 5 mm from the top perpendicular to the growth direction (thickness direction of the disk-shaped sample), and the critical temperature (Tc) near the center and the critical current density in the external magnetic field 1T are determined. As a result of measurement, there was a large composition shift in the thickness direction as shown in FIG.
[0050]
【The invention's effect】
As described in detail above, the present invention provides a raw material mixture containing an RE compound (RE is a rare earth element including Y), a Ba compound and a Cu compound, at least in a temperature range higher than the melting point of the raw material mixture. In an oxide superconductor manufacturing method for manufacturing a RE-Ba-Cu-O-based oxide superconductor by performing a treatment including a direct contact with the raw material mixture in order to support a molded body obtained by molding the raw material mixture By using a material in which the inclusion is composed of a Ba compound and the inclusion does not contain 50 mol% or more of RE element (RE is a rare earth element including Y), the reaction with the substrate is suppressed, and the composition We have made it possible to manufacture large-size, high-performance oxide superconductors with good yield without deviation.
[Brief description of the drawings]
1 is a table showing a composition analysis result in a thickness direction of a material manufactured in Example 1. FIG.
FIG. 2 is a table showing the results of analyzing main crystal phases present in the sample produced in Example 1 using a polarizing microscope and an electron beam microanalyzer (EPMA).
FIG. 3 is a table showing the measurement results of critical temperature (Tc) and critical current density of the sample manufactured in Example 1.
4 is a table showing the composition analysis results in the thickness direction of the samples manufactured in Example 2. FIG.
5 is a table showing the measurement results of critical temperature (Tc) and critical current density of the sample manufactured in Example 2. FIG.
6 is a table showing the composition analysis results in the thickness direction of the samples manufactured in Example 3. FIG.
7 is a table showing the results of analyzing the main crystal phase present in the sample produced in Example 3 with a polarizing microscope and an electron beam microanalyzer (EPMA). FIG.
8 is a table showing the measurement results of critical temperature (Tc) and critical current density of the sample manufactured in Example 3. FIG.
9 is a table showing the results of analyzing main crystal phases present in the sample produced in Example 4 using a polarizing microscope and an electron beam microanalyzer (EPMA). FIG.
10 is a table showing the measurement results of critical temperature (Tc) and critical current density of the sample manufactured in Example 4. FIG.
11 is a table showing the composition analysis results in the thickness direction of the sample manufactured in Comparative Example 1. FIG.
12 is a table showing the measurement results of critical temperature (Tc) and critical current density of the sample manufactured in Comparative Example 1. FIG.

Claims

A RE-Ba-Cu-O superconducting _{_{_{_{crystal, RE 1 Ba 2 Cu 3 O}}}} RE of _X 0.1 to 50 [mu] m in the phase ₄ Ba ₂ Cu ₂ O ₁₀ phase is dispersed, and, RE-Ba- The orientation of the RE element (RE is a rare earth element including Y) which is oriented so that the deviation of the orientation between the Cu-O-based superconducting crystals is ± 5 ° or less and is in the average direction of the c-axis direction of the superconducting crystal. An oxide superconductor characterized in that the composition deviation is within ± 1.5 mol% over a thickness of 15 mm or more in the direction (however, the composition is represented by a molar ratio of only RE, Ba, and Cu).

2. The oxidation according to claim 1, wherein 1 to 60 wt% of Ag is dispersed and contained as particles of 0.1 to 100 μm in the RE-Ba—Cu—O-based superconducting crystal. Superconductor.