JPH04180584A - Manufacture of oxide superconductor - Google Patents

Abstract

PURPOSE:To obtain an oxide superconductor having excellent characteristics by subjecting a precursor precipitated on the cathode by the electrolysis of a soln. obtd. by dissolving organic complexes of II a group elements and III a group elements in a periodic table as well as Cu in an organic solvent to heat treatment in an oxidizing atmosphere. CONSTITUTION:At the time of manufacturing an oxide superconductor expressed by a general formula: A-B-Cu-O (wherein A denotes one or more kinds among IIIa group elements in a periodic table such as Y, Sc, La, Yb, Er, Eu, Ho and Dy and B denotes one or more kinds among IIa group elements such as Mg, Ca, Sr and Ba), the anode and the cathode are immersed in an electrolytic bath obtd. by dissolving each organic complex of the A elements, B elements and Cu in an organic solvent such as methyl alcohol, and a direct current is conducted to reduce each complex of the A elements, B elements and Cu on the cathode, by which the precursor of a superconductor constituted of a composite metallic film of the A elements, B elements and Cu is precipitated. This precursor is heated, e.g. to 600 to 900 deg.C in an oxidizing atmosphere to obtain a dense oxide superconductor free from the generation of cracks in the grain boundaries and having excellent superconducting characteristics such as critical current density.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a method for manufacturing oxide-based superconductors, which are being developed for application as superconducting devices such as Josephson elements and superconducting memory elements, or coils for superconducting magnets. It is related to.

[Prior Art] Recently, various oxide-based superconducting materials have been discovered whose critical temperature (T c ) for transitioning from a normal conductive state to a superconducting state exceeds the liquid nitrogen temperature.

This type of oxide-based superconductor has the general formula AB-Cu-0
(However, A is Y, Sc, La, Yb, Er, Eu, Ho
.

Indicates more than nIaIIIa group element species of the periodic table such as Dy,
B represents one or more elements of group IIIa of the periodic table, such as Mg, Ca, Sr, and Ba. ).

Conventionally, the method described below is known as an example of a method for producing such an oxide-based superconductor.

A mixed powder is created by mixing multiple raw material powders containing each element constituting the oxide superconductor represented by A-B-Cu-0, and then this mixed powder is calcined to remove unnecessary components. After heat-treating this calcined powder to make a superconducting powder, this superconducting powder is filled into a metal sheath material, which is then molded into a predetermined shape by compression processing, etc., and heat-treated to make an oxide-based superconductor. It's a method.

[Problems to be Solved by the Invention] However, in the above manufacturing method, it is difficult to mix the raw material powders completely uniformly, so even if heat treatment is performed, the entire oxide superconductor in the metal sheath material However, this method does not have a completely uniform crystal structure, lacks density and orientation, and often cracks occur due to grain boundaries, making it impossible to obtain a superconductor with excellent properties.

In addition, while the raw material powder shrinks in volume through sintering, the metal sheath material undergoes thermal expansion, which causes cracking defects between the metal sheath material and the oxide superconductor housed inside. There was also the problem that good superconducting properties could not be achieved due to this.

This invention was made to solve the above problems, and provides a high-performance oxide superconductor that has a dense structure, does not cause cracks due to grain boundaries, and has excellent superconducting properties such as critical current density. The purpose is to provide a method for efficiently manufacturing.

7 Second Means for Solving the Problems 2 The method for producing an oxide superconductor of the present invention is based on the general formula A-
B-Cu-0 (Top A is Y, Sc, La.

Periodic table l of Y b, E r, E u, Ho, D y, etc.
Represents one or more of the l1a group elements, B is Mg, Ca,
Indicates one or more elements of group IIa of the periodic table, such as S r and B a. ) A method for producing an oxide-based superconductor having the composition shown in
The organic complex is electrolyzed in an electrolytic bath prepared by dissolving both elements in an organic solvent, and elements A, B, and Cu are precipitated on the cathode to form a superconducting precursor. The solution was to perform heat treatment in an atmosphere.

[Function] Element A, element B, and C, which are constituent elements of oxide-based superconductor
When electrolysis is performed in an electrolytic bath in which u is dissolved, these constituent elements are deposited on the cathode as a superconductor precursor of a metal film with a dense structure.

Therefore, by subjecting this superconductor precursor to heat treatment in an oxygen atmosphere, it can be oxidized, so that a superconductor with a dense structure can be obtained.

The present invention will be explained in detail below.

The manufacturing method of Mi's invention involves electrolysis in an electrolytic bath in which elements A, B, and Cu, which are constituent elements of an oxide superconductor, are dissolved, and these elements A, B, and Cu are deposited on the cathode. A superconductor precursor made of a composite metal is precipitated, and this superconductor precursor is subjected to heat treatment.

This electrolytic bath is made by dissolving element A, element B, and Cu as electrolytes in an organic solvent at a predetermined concentration.

As the electric field substance, an organic complex of elements A, B, and Cu, which are constituent elements of the oxide superconductor, can be used. The ligand of this organic complex is not particularly limited as long as this organic complex is soluble in an organic solvent that can conduct electricity; for example, dipivaloylmethyl (C, H
,,O,), hexafluoroacetylacetonato (C5H
F so , ), etc. can be suitably used. Further, the ligands of the organic complex coordinated to each constituent element may be the same or different. It is preferable to contain fluorine as a constituent element of the ligand because it can improve the solubility of the complex in organic solvents. However, in order to improve the density of the obtained superconductor, it is necessary to It is preferable that it does not contain fluorine as a constituent element.

The organic solvent for dissolving these organic complexes is not particularly limited as long as it is an organic solvent that can dissolve the above-mentioned organic complexes and can conduct electricity, such as alcohols such as methyl alcohol and ethyl alcohol, acetone, acetylacetone, etc. Ketones and the like can be suitably used.

The concentration of the organic complex dissolved in the organic solvent is variously selected depending on the type of oxide superconductor to be manufactured, the type of organic complex, the magnitude of the applied voltage, etc.
001~(1,01mol/L B element organic complex 0.0
01-0.01 mot/L Cu organic complex 0.001
~O', 01 mol/12 is preferred. Further, the temperature of the electrolytic bath is variously selected depending on the energization conditions, etc., but usually -50 to 20°C is suitable.

The energization conditions of the electrolytic bath adjusted in this way are appropriately selected depending on the type of electrolytic bath, the dissolved concentration of the organic complex, etc., but usually a DC current of 0.2 to 1.2 A is used for lO to t.
It is preferable to apply a voltage of 10 to 60 minutes.

Further, the electrode is not particularly limited, but materials used in ordinary electrolysis, such as platinum and graphite, can be used.

FIG. 1 shows this electrolysis process. 1st
In the figure, the symbol l is an electrolytic bath. This electrolytic bath 1 is formed by dissolving elements A, B, and Cu together as an organic complex in an organic solvent.

A pair of electrodes 28% 2 b is immersed in this electrolytic bath l. By performing electrolysis in such an electrolytic bath, the central elements of the organic complex, such as A element, B element, and Cu
are reduced and deposited on the cathode as a superconductor precursor 3 consisting of a composite metal film of element A, element B, and Cu. Since this superconductor precursor 3 is deposited by electrolysis, it has a dense structure.

After energization for a certain period of time, the cathode 2a is taken out and cleaned, and after one step, the superconductor precursor 3 is subjected to heat treatment.

This heat treatment oxidizes the superconductor precursor 3 and improves the crystal orientation to produce an oxide-based superconductor with a dense structure. The heat treatment conditions are similar to the usual heat treatment conditions used in manufacturing oxide superconductors, such as 600 to 900°C in an oxygen atmosphere;
For example, 10 hours or more.

The f-dioxide-based superconductor manufactured in this way is formed into a film by electrolysis and has a dense and well-oriented crystal structure because the f-superconductor body is heat-treated. This results in a high critical current density.

In addition, since the manufacturing method of the present invention heat-treats a uniform superconductor precursor, the obtained oxide-based superconductor has a completely uniform composition, and there are no cracks or the like in the grain boundaries of each constituent element. Since this does not occur, a superconductor with high characteristics can be obtained.

Further, according to the manufacturing method of the present invention, an oxide-based superconductor having a desired thickness can be easily manufactured.

[Example] (Example 1) 4.3 g, 0.01 mol Cu(CzH1902)2
and 5.0g, O, Olmol B, a(CzH+s02
)2, 6.4 g, 0.01 mol of Y (CzH+s
O2)3 was dissolved in 30 am3 of acetone to prepare an electrolytic bath.

A Pt1i electrode was prepared as an electrode system for this, and this pt electrode was immersed in the above electrolytic bath kept at 0°C, and an applied voltage of 100
The superconductor precursor made of a composite metal film of Cu, Ba, and Y was deposited on the cathode to a thickness of 1.5 mm by electrolysis at V and a current of 0.2 A for 1 hour.

After cleaning this superconductor precursor, it was washed for 90 minutes in an oxygen atmosphere.
A heat treatment was performed at 0° C. for 24 hours to obtain an oxide superconductor.

As a result of measuring the critical temperature (Tc) and critical current density (Jc) of the obtained oxide-based superconductor, it was found that Tc-90, Jc = 2.2X 10'''A/Cm!, indicating excellent superconducting properties. The cross section of this oxide superconductor is shown as
As a result of line diffraction analysis, Y + B atcu, o 7-
It was confirmed that perovskite crystals with a composition n were formed.

(Example 2) 9.5 g in 30 cm3 of acetone as electrolytic bath.

0.02 mol of Cu(C5HF 602)2 and l
Ig, 0.02mol of Ba(CsHF to
2) 2, 7.1 g, 0.01 mol of Y (Cs
An oxide-based superconductor was produced in exactly the same manner as in Example 1, except that HF so 2) and 3 were respectively dissolved.

As a result of measuring the critical temperature (Tc) and critical current density (Jc) of the obtained oxide-based superconductor, Tc = 92KSJ
c=4.3 x 10'A/cm', showing excellent superconducting properties similar to Example 1. Furthermore, as a result of X-ray diffraction analysis of the cross section of this oxide-based superconductor, Y + B azc u
The formation of perovskite crystals having a composition of so 7-n was confirmed.

[Effects of the Invention] As explained above, the method for producing an oxide superconductor of the present invention involves dissolving an organic complex of constituent elements of an oxide superconductor in an organic solvent and then electrolyzing it in an electrolytic bath. After the constituent elements are precipitated on the cathode to form a superconducting precursor, this superconducting precursor is heat-treated in an oxygen atmosphere. It is possible to obtain an oxide-based superconductor with the same structure. Therefore, it is possible to easily produce a high-performance oxide-based superconductor that would not be possible using conventional production methods.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram showing the state of electrolysis in one step of the method for producing an oxide-based superconductor of the present invention. l...electrolytic bath, 2a, 2b...electrode, 3.
...Superconductor precursor, L...Organic solvent.

Claims (1)

[Claims] General formula AB-Cu-O (where A is Y, Sc, La,
B represents one or more elements of group IIIa of the periodic table such as Yb, Er, Eu, Ho, and Dy, and B represents one or more of elements of group IIa of the periodic table such as Mg, Ca, Sr, and Ba. ) A method for producing an oxide superconductor having a composition shown in A method for producing an oxide-based superconductor, the method comprising: precipitating element A, element B, and Cu on a cathode to form a superconducting precursor, and then heat-treating the superconducting precursor in an oxygen atmosphere.