【発明の詳細な説明】[Detailed description of the invention]
産業上の利用分野
本発明は一般式Ba2YCu3O7-x（ただし、ｘ＝0.0
〜0.9を表わす。以下同じ）で示される化学組成
を持つ超伝導酸化物焼結体の製造方法に関する。
従来技術
一般式Ba2RCu3O7-xで示される化合物は、超
伝導体として知られており、この超伝導体はTc
90Kと言う高温度の転移点を有するが、Tc付
近で導入できる電流密度、即ち臨界電流密度Icは
さほど大きくなく、中には１〜2A／cm2以下のも
のもある。このIcを向上させると利用範囲は拡大
される。
従つて、より高いTcとより大きなIcを持つ材
料にすることが重要な課題である。
発明の目的
本発明は前記課題を解決すべくなされたもの
で、その目的は高いTcを持ち、かつ大きなIcを
同時に持つ超伝導体の製造方法を提供するにあ
る。
発明の構成
本発明者らは前記目的を達成すべく鋭意研究の
結果、一般式Ba2YCu3O7-xで示される原料粉末
であるBaCO3またはBaO、Y2O3、CuOを組成割
合に混合し、これを１気圧の酸素気流中で850〜
900℃で加熱して前記一般式組成の酸化物組成物
とする。この組成物は斜方晶系相でａ＝3.88、ｂ
＝3.82、ｃ＝11.69Å程度の格子定数を有す。
この組成物を成形し、これをアルミナるつぼ中
のCuOとY2O3、Al2O3、MgOの１種または２種
以上との混合粉末からなるつめ粉中に埋込み、１
気圧以上の酸素ガス中で700〜930℃で加熱する
と、高いTcを持ち、大きなIcを持つ超伝導体が
得られることを究明し得た。この知見に基づいて
本発明を完成した。
本発明の要旨はBa2YCu3O7-x（ただし、ｘ＝0.0
〜0.9を表わす）で示される該組成酸化物成形体
を、CuOとY2O3、Al2O3、MgOの１種または２
種以上との混合粉末中に埋込み、700〜930℃で１
気圧以上の酸素雰囲気中に焼成することを特徴と
する超伝導酸化物焼結体の製造法、にある。
焼結温度が700℃より低いと焼結反応が完了せ
ず得られる焼結体のIcは低く、930℃を超えると
液相が出現し易くなる。従つて、焼結温度は700
〜930℃、好ましくは700〜900℃である。
酸素ガス圧は１気圧でもよいが、高くする方が
Icを大きくするので好ましい。
つめ粉のCuOとY2O3、Al2O3、MgO（以下総称
して希釈剤と言う）との混合割合は、希釈剤の割
合が５〜75重量％、好ましくは10〜75重量％であ
ることがよい。５重量％より少ないとCuO同志が
焼結し易く導電性が不規則となり、表面の一部分
にCuOが過剰に入りTcを低下させる。75重量％
を超えるとつめ粉を使用しない場合と比べ効果の
差違が小さくなる。
このつめ粉を使用して焼成すると、成形体から
CuOの脱離がなく、効果的にBa2YCu3O7-x中の
Ｘ量即ち酸素欠陥量を少なくし得られる。
実施例 １
Ba2YCu3O6.5の組成になるように、BaCO3，
Y2O3，CuO粉末を秤量混合した。この混合物を
１気圧の酸素ガスを0.5／minの流量で流した
900℃の炉中に入れ、24時間処理した。これを炉
中から取り出し、約12.7mm径、厚さ２mmの成形体
を作り、これをアルミナつぼ中に入れたAl2O366
重量％、CuO34重量％からなるつめ粉中に埋め込
み、上記と同じ条件で27時間焼成した。得られた
焼結体を直流４端子法で抵抗測定を行つたとこ
ろ、Tc（ｅ）（完全に抵抗が零となる温度）が
92K、Ic74A／cm2であつた。
実施例 ２
Ba2YCu3O6.5組成になるようにした混合粉末を
実施例１と同じ条件で反応時間のみを48時間とし
て生成物を得た。この生成物の成形体を実施例１
と同様にして同じつめ粉中、同条件で39時間焼成
した。得られた焼結体はTc（ｅ）＝91K、Ic
130A／cm2であつた。
実施例 ３
実施例２と同様にして得た生成物の成形体を18
時間（実施例２と同条件）焼成し、さらに４気圧
の酸素中900℃で24時間焼成した。得られた焼成
体はTc（ｅ）＝83K、Ic193A／cm2であつた。使
用したつめ粉は実施例１と同じ物であつた。
実施例 ４
実施例２と同様にして得られた生成物の成形体
を焼成条件を変えた場合の結果は次の通りであつ
た。
Industrial Application Field The present invention is based on the general formula Ba 2 YCu 3 O 7-x (where x=0.0
~0.9. The present invention relates to a method for manufacturing a superconducting oxide sintered body having a chemical composition shown in (hereinafter the same). Prior Art The compound represented by the general formula Ba 2 RCu 3 O 7-x is known as a superconductor, and this superconductor is Tc
Although it has a high temperature transition point of 90K, the current density that can be introduced near Tc, that is, the critical current density Ic, is not very large, and some of them are less than 1 to 2 A/cm 2 . Improving this IC will expand the range of use. Therefore, it is important to develop materials with higher Tc and larger Ic. Purpose of the Invention The present invention was made to solve the above-mentioned problems, and its purpose is to provide a method for manufacturing a superconductor having both a high Tc and a large Ic. Structure of the Invention As a result of intensive research to achieve the above object, the present inventors determined that the composition ratio of BaCO 3 or BaO, Y 2 O 3 and CuO, which is a raw material powder represented by the general formula Ba 2 YCu 3 O 7-x , was 850~ in an oxygen stream of 1 atm.
It is heated at 900°C to obtain an oxide composition having the general formula composition. This composition has an orthorhombic phase with a=3.88 and b
=3.82, c=11.69 Å. This composition was molded and embedded in a powder mixture of CuO and one or more of Y 2 O 3 , Al 2 O 3 , and MgO in an alumina crucible.
We have found that a superconductor with high Tc and large Ic can be obtained by heating at 700 to 930°C in oxygen gas above atmospheric pressure. The present invention was completed based on this knowledge. The gist of the present invention is Ba 2 YCu 3 O 7-x (where x=0.0
~0.9) is mixed with CuO and one or two of Y 2 O 3 , Al 2 O 3 , and MgO.
Embedded in mixed powder with seeds or more, 1 at 700-930℃
A method for producing a superconducting oxide sintered body, characterized by firing in an oxygen atmosphere at a pressure higher than atmospheric pressure. If the sintering temperature is lower than 700°C, the sintering reaction will not be completed and the resulting sintered body will have a low Ic, and if it exceeds 930°C, a liquid phase will likely appear. Therefore, the sintering temperature is 700
-930°C, preferably 700-900°C. Oxygen gas pressure may be 1 atm, but it is better to make it higher.
This is preferable because it increases Ic. The mixing ratio of CuO, Y 2 O 3 , Al 2 O 3 , and MgO (hereinafter collectively referred to as diluent) in the nail powder is such that the diluent ratio is 5 to 75% by weight, preferably 10 to 75% by weight. It is good that If it is less than 5% by weight, CuO tends to sinter together, resulting in irregular conductivity, and excessive CuO enters a portion of the surface, lowering Tc. 75% by weight
When the amount exceeds , the difference in effectiveness becomes smaller compared to when no nail powder is used. When baked using this nail powder, the molded product
There is no desorption of CuO, and the amount of X, that is, the amount of oxygen vacancies in Ba 2 YCu 3 O 7-x can be effectively reduced. Example 1 BaCO 3 ,
Y 2 O 3 and CuO powder were weighed and mixed. Oxygen gas at 1 atm was flowed through this mixture at a flow rate of 0.5/min.
It was placed in a 900°C oven and treated for 24 hours. This was taken out of the furnace, a molded body with a diameter of approximately 12.7 mm and a thickness of 2 mm was made, and this was placed in an alumina pot .
% by weight, and embedded in nail powder consisting of 4% by weight of CuO, and baked for 27 hours under the same conditions as above. When we measured the resistance of the obtained sintered body using the DC 4-terminal method, we found that Tc(e) (the temperature at which the resistance becomes completely zero) was
It was 92K, Ic74A/cm 2 . Example 2 A product was obtained using a mixed powder having a Ba 2 YCu 3 O 6.5 composition under the same conditions as in Example 1 except for a reaction time of 48 hours. A molded body of this product was prepared in Example 1.
It was baked for 39 hours in the same nail powder under the same conditions. The obtained sintered body has Tc (e) = 91K, Ic
It was 130A/ cm2 . Example 3 A molded product obtained in the same manner as in Example 2 was
It was fired for an hour (same conditions as in Example 2) and further fired at 900°C for 24 hours in 4 atmospheres of oxygen. The obtained fired body had Tc(e)=83K and Ic193A/cm 2 . The nail powder used was the same as in Example 1. Example 4 When the molded product obtained in the same manner as in Example 2 was fired under different firing conditions, the results were as follows.
【表】
比較例 １
実施例２で得られた生成物を成形体を、つめ粉
を使用せず、１気圧酸素気流中で47時間焼成し
た。得られた焼成体Tc（ｅ）＝82K、Ic7.2A／
cm2であつた。
発明の効果
本発明の方法によると、CuOとY2O3、Al2O3、
MgOの１種または２種以上との混合粉末からな
るつめ粉中に一般式Ba2YCu3O7-x成形体を埋込
み、酸素ガス中で焼成することにより、高いTc
を持ち、きわだつた臨界電流密度Icの向上させた
ものが得られる優れた効果を有する。[Table] Comparative Example 1 The molded product obtained in Example 2 was calcined for 47 hours in an oxygen stream at 1 atm without using nail powder. Obtained fired body Tc (e) = 82K, Ic7.2A/
It was warm in cm2 . Effects of the Invention According to the method of the present invention, CuO and Y 2 O 3 , Al 2 O 3 ,
By embedding a compact with the general formula Ba 2 YCu 3 O 7-x in a powder made of a mixed powder with one or more types of MgO and firing it in oxygen gas, a high Tc
It has the excellent effect of providing a markedly improved critical current density Ic.