JPS63256519A - Production of superconductor - Google Patents

Abstract

PURPOSE:To produce a high temp. superconductor having a sharp transition temp. width and superior characteristics in a short time and at low temp. with satisfactory reproducibility by heat treating an alkali hydrolyzed or solvolyzed product of a mixture of specified amts. of halides or nitrates of elements constituting an aimed material. CONSTITUTION:Each specified amt. of halide or nitrate of at least one kind of element M1 selected from B, Al, Ga, In, Ti, Sc, Y, and lanthanides (La-Lu), at least one kind of element M2 selected from Be, Mg, Ca, Sr, Ba, Ra, Sn, and Pb, and an element M3(=Cu) is hydrolyzed or solvolyzed under heating or without heating after adding, if necessary, an org. material having >=2 OH groups, in the presence of an alkali hydrolyzing agent or a solvolyzing agent (such as tetraalkyl ammonium hydroxide) contg. no alkali metal capable of generating OH ions or alkoxide ions in aq. soln. or in an org. solvent. The hydrolyzed or solvolyzed product is isolated, and heated in (non)oxygen atmosphere, to obtain thus a superconductor expressed by formula (wherein x-w are optional mole fractions).

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for manufacturing a superconductor.

(Conventional technology) Conventionally, methods for producing superconductors mainly based on copper oxides include:
(i) Finely crush the corresponding metal oxide or metal carbonate in a mortar or sieve the resulting fine powder,
Alternatively, knead with a suitable binder and
A method of sintering at a high temperature of 1200 °C (Wu, M,
K, et al.

Phys, Rev, Lett, 58,908 (198
7)) (ii) A method in which sodium carbonate is added to a homogeneous aqueous solution of the corresponding metal nitrate, the resulting poorly soluble metal carbonate is decarboxylated at 800°C, and finally sintered at 1100°C. A similar method of decarboxylation in the form (
Capone.

D, W, et al. Appl, Phys, Lett, 50
, 543 (1987)) are known.

However, method (i) includes a process of forming a solid solution of the corresponding various metal oxides by solid phase reaction,
From the common knowledge of chemical reactions.

Synthesizing a material with a uniform composition requires high temperatures and a long time.For example, in the case of copper oxide, divalent copper is
It is known that copper is converted to monovalent copper at temperatures above 050°C, which leads to a loss of superconductivity. On the other hand, obtaining a superconductor with a uniform composition requires a high temperature of 1100° C. or higher. Since method (ii) uses a water-soluble metal nitrate as a starting material, the metal salts are uniformly mixed at room temperature. However, decarboxylation occurs at 800℃ and 1200℃
It is necessary to degas and sinter at a high temperature of °C. This tends to cause bubbles and cranks inside the superconductor.

(Problems to be Solved by the Invention) In order to improve these points, the present invention provides a method for manufacturing a superconductor that enables uniform mixed sintering at low temperatures.

(Means for Solving the Problems) The present invention involves dissolving halides or metal nitrates in water or organic solvents in order to obtain a superconductor in which various metals corresponding to various desired metal ions are uniformly mixed. A process of producing a mixture of various metal hydrogels and metal organogels by using a hydrolyzing agent or solvolytic agent soluble in water or an organic solvent from a homogeneous metal ion mixture, and isolating the resulting products. After that, the method is characterized by including a step of heat-treating the product in an oxygen atmosphere or an oxygen-free atmosphere to form a metal oxide. At this time, heating can be carried out as appropriate in order to increase the effect of the hydrolyzing agent or solvolytic agent or for the purpose of sufficiently advancing the reaction.

According to a first preferred embodiment, the hydrolyzing agent or solvolytic agent is characterized in that it does not contain an alkali metal that may particularly interfere with the development of superconductivity, and such a hydrolyzing agent or solvolytic agent is used. By doing so, a superconductor with a high superconducting transition temperature can be obtained.

According to the second preferred embodiment, the hydrolyzing agent or solvolytic agent that can be most preferably used in the first embodiment has the ability to generate hydroxyl ions or alkoxide ions in an aqueous solution or an organic solvent. It is possible to use an organic compound having Most preferably, tetraalkylammonium hydroxide, trialkylsulfonium hydroxide, diazabicycloundecene, and dimethylaminopyridine can be used.

According to a third preferred embodiment, an organic substance having two or more hydroxyl groups is added in advance during hydrolysis or solvolysis. By adding an organic substance having two or more such hydroxyl groups.

A superconductor having a high yi composition can be obtained.

According to another preferred embodiment, the polymer is added beforehand or after hydrolysis or solvolysis and the product is then heat treated in an oxygen atmosphere. According to this aspect, the superconductor can be easily molded into any shape in the step of heat-treating the isolated product after hydrolysis or solvolysis in an oxygen atmosphere or an oxygen-free atmosphere. Become.

To give an overview of the heat treatment of the present invention, 9 The heat treatment of the present invention directly produces fine mixed metal oxides by further heat-treating the mixed metal hydro or organogel synthesized by hydrolysis or solvolysis in its solution. A step of obtaining a preform may also be included. In addition, there is a step of heat-treating the mixed metal hydrogel, organogel, or fine mixed metal oxide particles synthesized in this way at a higher temperature, but at a temperature low enough to cause reduction of divalent copper, in order to make the particles continuous. Also included. Also,
In order to achieve more complete sintering, a small amount of polymer is allowed to coexist in the solution during hydrolysis, and the resulting gel or metal oxide fine particles generated during solution heating are adsorbed onto the coexisting polymer, or isolated. It may also include a step of sintering a gel body or a metal oxide fine particle generated by heating the gel body to which a small amount of polymer is adsorbed.

According to the present invention, high-temperature superconductors can be uniformly mixed on an atomic scale to a predetermined composition at around room temperature, and the dehydration or alkyl partial decomposition reaction can be completed by heating the superconductor, thereby minimizing the amount of metal ions. Due to the diffusion of , a crystal structure exhibiting a superconducting phase can be completed at a lower temperature than conventional methods. In addition, it is possible to completely suppress the incorporation of these ions into the gel that occurs due to hydrolysis by basic substances containing alkali metals, and the final sintering temperature is higher than that reported so far. This method has a great advantage in that superconductors can be produced at relatively low temperatures without reducing divalent copper.

Nine typical embodiments of the present invention are shown below.

(Example 1) YCI:l 0.2mol/1. BaCl20.2
mol/1. CuC1z 0.2m.

1/l of each aqueous solution was mixed at room temperature in a ratio of 1:2:3. To this, 10% tetramethylammonium hydroxide
% aqueous solution was added gradually and the resulting hydrogel was filtered with suction. This was pre-sintered at 300-400°C. Furthermore, it was sintered at 600-900'C in an oxygen atmosphere. The obtained powder was pressed at 400-600 Kg/cm''.
Sintered at 0°C. Temperature changes in electrical conductivity of the slowly cooled samples were determined using a four-terminal AC method. The results are shown in Figure 1. Complete superconductivity was achieved at an absolute temperature of 92, and the transition width, which is a measure of sample quality, was only 0.2.

(Example 2) LaC1,0,2mo I/1. BaBrzO,2mo
l/1. Each ethanol solution containing 1 g of CuC and 0.2 mol/1 was mixed at room temperature in a ratio of 1=2:3. A 10% methanol solution of tetramethylammonium hydroxide was gradually added to this, and the resulting gel was filtered with suction. This was pre-sintered at 300-400°C. Furthermore, it was sintered at 600-900°C in an oxygen atmosphere. The obtained powder was pressed at 400-600 Kg/cm2. The pellets were further heated at 920-1050°C under an oxygen atmosphere.
Sintered with Temperature changes in electrical conductivity of the slowly cooled samples were determined using a four-terminal AC method. Complete superconductivity was reached at an absolute temperature of 37, and the transition width, which is a measure of sample quality, was only 0.2.

(Example 3) YCI, 0.2mo 1/1. BaCl20.2
mol/1. CuC1z 0.2m.

The 1/1 aqueous solutions were mixed at room temperature in a ratio of 6:4:1. A 10% aqueous solution of tetramethylammonium hydroxide was gradually added to this.

The resulting hydrogel was filtered with suction. This is 300-40
Temporary sintering was performed at 0°C. Furthermore, under an oxygen atmosphere, 600-
It was sintered at 900°C. The obtained powder is 400-600
Kg/cm". This pellet was further sintered at 920-1050°C in an oxygen atmosphere. The temperature change in electrical conductivity of the slowly cooled sample was determined by a four-probe alternating current method.

Complete superconductivity was reached at an absolute temperature of 83, and the transition width was only 0.5.

(Example 4) LaC1*0.2mo t,'1,5rC1tO,
2mol/l, CuC1z 0.2m o 1/
1 aqueous solutions were mixed at room temperature in a ratio of 9:1:4. To this, 10% tetramethylammonium hydroxide
% aqueous solution was added gradually and the resulting hydrogel was filtered with suction. This was pre-sintered at 300-400°C. Furthermore, it was sintered at 600-900°C in an oxygen atmosphere. The obtained powder was pressed at 400-600 Kg/cm''.

This pellet is further heated under an oxygen atmosphere.

Sintered at 920-1050°C. Temperature changes in electrical conductivity of the slowly cooled samples were determined using a four-terminal AC method. absolute temperature 3
It reached complete superconductivity at 7, and the transition width was 1, M2, and 5.

(Example 5) YCIs 0.2mo I/1. BaBrzO, 2m
ol/l, CuC1z 0.2m.

1/1 of each glycerin solution was mixed at room temperature in a ratio of 1:2:3. A 10% methanol solution of tetramethylammonium hydroxide was gradually added to this, and the resulting gel was filtered with suction.

This was pre-sintered at 300-400°C. Furthermore, it was sintered at 600-900°C in an oxygen atmosphere. The obtained powder was pressed at 400-600 kg/cm''.The pellet was further sintered at 920-1050°C in an oxygen atmosphere.The temperature change in conductivity of the slowly cooled sample was determined by the four-terminal AC method. The results are shown in Figure 1. Superconductivity was reached completely at an absolute temperature of 92, and the transition width, which is a measure of sample quality, was only 0.2.

(Example 6) YCl, 0.2 mol/l, BaCl 1°0.2
mol/l, CuCLO,2mo'1/1
The respective aqueous solutions were mixed at room temperature in a ratio of 1:2:3. A KOH aqueous solution was gradually added thereto, and the resulting hydrogel was suction filtered. After thoroughly washing with pure water, add 300-4
Temporary sintering was performed at 00°C. Furthermore, under an oxygen atmosphere, 600
Sintered at -900°C. The obtained powder was 400-60
0 kg/cm". This pellet was further sintered at 920-1050° C. in an oxygen atmosphere. The temperature change in conductivity of the slowly cooled sample was determined by a four-terminal alternating current method.

Complete superconductivity was achieved at an absolute temperature of 86, and the transition width, which is a measure of sample quality, was 0.9.

(Example 7) YCl, 0.2mo 1/1. BaC1zO,2m
ol/l, CuC1z 0.2m.

Each 1/1 aqueous solution was mixed at a ratio of 1:2:3 at room temperature. A 10% aqueous solution of tetramethylammonium hydroxide was gradually added to this.

The resulting hydrogel was further heated in the solution, and the resulting black precipitate was suction filtered. 300-400°
Temporary sintering was performed using C. Furthermore, under oxygen atmosphere, 600-9
Sintered at 00°C. The obtained powder was heated to 400-600K.
g/cm". This pellet was further pressed under an oxygen atmosphere.

Sintered at 920-1050°C. Temperature changes in electrical conductivity of the slowly cooled samples were determined using a four-terminal AC method. absolute temperature 9
0, it reached complete superconductivity, and the transition width, which is a measure of the quality of the sample, was 0.6.

(Example 8) YNOs O,2mo 1/l, BaN0+0, 2
mol/1. CuN0. 0. 2m.

1/l of each aqueous solution was mixed at room temperature in a ratio of 1:2:3. A 10% aqueous solution of tetramethylammonium hydroxide was gradually added to this.

The resulting hydrogel was filtered with suction. 300% of this in the air
Temporary sintering was performed at -400°C. Furthermore, under an oxygen atmosphere, 6
Sintered at 00-900°C. The obtained powder was heated to 400-
600 Kg/cm''. The pellets were further sintered at 920-1050°C under an oxygen atmosphere.

Temperature changes in electrical conductivity of the slowly cooled samples were determined using a four-terminal AC method. The results are shown in Figure 1. Complete superconductivity was achieved at an absolute temperature of 92, and the transition width, which is a measure of sample quality, was only 0.2.

(Example 9) YCl30.2mol/l, BaClzO,2mol/
1. CuC1z 0.2m.

Each 1/1 aqueous solution was mixed at a ratio of 1:2:3 at room temperature. A small amount of polyvinyl alcohol aqueous solution was added thereto, and a 10% aqueous solution of tetramethylammonium hydroxide was gradually added thereto, and the resulting hydrogel was suction-filtered.

This was pre-sintered at 300-400°C. Furthermore, it was sintered at 600-900'C in an oxygen atmosphere. The obtained powder was pressed at 400-600 Kg/cm2. This pellet was further sintered at 920-1050°C under an oxygen atmosphere. Temperature changes in electrical conductivity of the slowly cooled samples were determined using a four-terminal AC method. Complete superconductivity was achieved at an absolute temperature of 93, and the transition width, which is a measure of sample quality, was only 0.3.

(Example 10) YCl3 0.2mol/I, BaCl1g0.2
mol/I, CuCltO, 2m.

1/l of each aqueous solution was mixed at room temperature in a ratio of 11:3. To this, tetramethylammonium hydroxide 1
Add 0% aqueous solution gradually.

Further, the black precipitate produced by the heating treatment was suction-filtered. This was kneaded with a small amount of polyvinyl alcohol solution, and
Temporary sintering was performed at 0-400'C.

Furthermore, it was sintered at 600-900°C in an oxygen atmosphere. The obtained powder was pressed at 400-600 Kg/cm2. This pellet was further heated to 920-1 under an oxygen atmosphere.
Sintered at 050°C.

Temperature changes in electrical conductivity of the slowly cooled samples were determined using a four-terminal AC method. Complete superconductivity was achieved at an absolute temperature of 90°C, and the transition width, which is a measure of sample quality, was only 0.4.

In the same manner, Y was prepared to a predetermined composition.

Sc and lanthanide elements, alkaline earth elements such as Ba, and copper halides or nitrates were used as raw materials and hydrolyzed to obtain the target substance. The results are summarized in the table below.

(Effects of the Invention) As explained above, according to the low-temperature production method via the hydrolysis method or solvolysis method of the present invention, sintering can be performed at a temperature at which divalent copper does not reduce, and it is possible to sinter at a low temperature. It has the advantage of being able to easily produce high-temperature superconductors with sharp transition widths and good characteristics by dehydration of hydrogels or pre-sintering accompanied by thermal decomposition of the alkyl moieties of organogel.High-temperature superconductors, especially Materials that achieve superconductivity at temperatures above the liquid nitrogen temperature of 77% are expected to have a wide range of industrial applications such as Josephson devices, power transport, and magnets that generate high magnetic fields. It has a huge impact in that it can be done.

[Brief explanation of drawings]

FIG. 1 shows Y+ produced by the method of the present invention. Ba... Cu3. . FIG. 2 is a diagram showing resistance-temperature characteristics of an oxide superconductor.

Claims (6)

[Claims] (1) General compositional formula (M1)_x(M2)_y(M3)_
zO_w(M1 is (B, Al, Ga, In, Tl, Sc
, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, G
d, Tb, Dy, Ho, Er, Tm, Yb, Lu), M2 is (B
e, Mg, Ca, Sr, Ba, Ra, Sn, Pb), M3 is Cu
, x, y, z, w are arbitrary atomic mole fractions) In the method for producing superconductors, halides or nitrates of M1, M2, and M3 are heated or not heated to form an alkali. It is characterized by comprising a step of hydrolysis or solvolysis, and a step of isolating the resulting product, and then heat-treating the product in an oxygen atmosphere or an oxygen-free atmosphere to form a metal oxide. A method for manufacturing superconductors. (2) The method for producing a superconductor according to claim 1, wherein the decomposing agent used in alkaline hydrolysis or solvolysis does not contain an alkali metal. (3) Claims characterized in that the decomposing agent during alkaline hydrolysis or solvolysis is an organic compound having the ability to generate hydroxyl ions or alkoxide ions in an aqueous solution or an organic solvent. A method for producing a superconductor according to item 1 or 2. (4) The decomposing agent during alkaline hydrolysis or solvolysis is tetraalkylammonium hydroxide,
The method for producing a superconductor according to any one of claims 1, 2, and 3, characterized in that the superconductor is trialkylsulfonium hydroxide, diazabicycloundecene, or dimethylaminopyridine. (5) Claims 1, 2, 3, and 4, characterized in that an organic substance having two or more hydroxyl groups is added in advance during hydrolysis or solvolysis. Method of manufacturing superconductors. (6) Claims 1, 2 and 2 include the step of adding the polymer beforehand or after hydrolysis or solvolysis, and then heat-treating the product in an oxygen atmosphere. A method for producing a superconductor according to any one of Items 3, 4, and 5.