JPS63295415A - Production of superconductor - Google Patents

Abstract

PURPOSE:To obtain a superconductor sintered at low temp. and mixed uniformly by hydrolyzing or solvolyzing a uniform mixed soln. of halide, nitrate etc., of each element constituting a superconductor having a specified compsn. and treating thereafter the obtd. product with an oxidizing agent. CONSTITUTION:A superconductor expressed by the general formula: (M1)x(M2)y(M3)zOw (wherein M1 is at least one element selected from a group consisting of B, Al, Ga, In, Tl, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; M2 is at lease one element selected from a group consisting of Be, Mg, Ca, Sr, Ba, Ra, Sn, and Pb; M3 is Cu; each x, y, z, and w is optional atomic fraction of respective atom) is formed by a process described hereunder. Namely, each halide, nitrate, or perchlorate of M1, M2, and M3 is hydrolyzed with alkali or solvolyzed, and a product obtained by adding an oxidizing agent to the hydrolyzed or solvolyzed product is transformed to each metal oxide by heating the oxidized product.

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,
Or knead with a suitable binder and
A method of sintering at a high temperature of 1200 °C (Wu, M,
and others.

Phys, Rev. Lett, 58.908 (1987
)) (ii) Sodium carbonate is added to a homogeneous aqueous solution of the corresponding metal nitrate, and the resulting sparingly soluble metal carbonate is
A method of decarboxylation at 00°C and finally sintering at 1100°C, or a method of decarboxylation in the form of oxalate (C
apone.

D, W, et al. Appl, Phys, Lett.

50.543 (1987)) are known.

However, method (i) involves a process of forming a solid solution of various metal oxides by solid phase reaction, which is common sense in 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 converts to monovalent copper at temperatures above 0.050"C, which leads to the loss of superconductivity. On the other hand, in order to obtain a superconductor with a uniform composition, a high temperature of 1100"C or above is required. Since method (ii) uses water-soluble metal nitrates as starting materials, uniform mixing of the metal salts is carried out at room temperature.However, decarboxylation occurs at 800°C and
It is necessary to degas and sinter at a high temperature of ℃. This tends to cause bubbles and cracks 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 hydrolysis agent or solvolysis agent soluble in water or an organic solvent from a homogeneous metal ion mixture, and further oxidation of the resulting product. The method is characterized in that it includes a step of adding an agent to form a mixed metal oxide and then heat-treating the product in an oxygen atmosphere or an oxygen-free atmosphere. 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, dryalkylsulfonium hydroxide, diazabicycloundecene, and dimethylaminopyridine can be used.

The oxidizing agent used in the present invention includes halogen (fluorine, chlorine, bromine, iodine), nitrate ion, or ions containing halogen and oxygen (perchlorate ion, chlorate ion, hypochlorite ion).

perbromate ion, bromate ion, hypobromite ion, periodate ion, iodate ion, hypoiodite ion) or hydrogen peroxide or sulfur-containing oxides (peroxomonosulfate ion, peroxodisulfate ion) Alternatively, superoxide ions or the like can be selected, and by facilitating the formation of metal oxides, a superconductor with highly homogeneous composition can be obtained.

In addition, if an additive, which is an organic substance with one or more hydrophilic moieties and has a thickening effect or a surfactant effect, is added during hydrolysis or solvolysis or before or after the reaction with an oxidizing agent, it will be easier to shape the composition before firing. It is also effective in homogenizing the

To summarize the heat treatment of the present invention, the heat treatment of the present invention further adds an oxidizing agent to a mixed metal hydro or organogel synthesized by hydrolysis or solvolysis, synthesizes metal oxides under mild conditions, and directly synthesizes metal oxides. A step of obtaining a fine mixed metal oxide preform may also be included.

In addition, the fine mixed metal oxide fine particles synthesized in this way can be heat-treated at a higher temperature to make the particles continuous, but the heat treatment must be performed at a temperature sufficiently lower than the temperature at which divalent copper undergoes reduction. is preferable, and in order to achieve more complete sintering, a small amount of polymer, thickener, or surfactant is allowed to coexist in the solution during hydrolysis or oxidation.
Dispersing and sintering the generated gel or metal oxide fine particles is also an effective appetizer.

In the method of the present invention, a superconductor can be uniformly mixed on an atomic scale to a predetermined composition at around room temperature, and the formation of a metal oxide mixture is completed by treatment with an oxidizing agent and heat treatment.

Therefore, with minimal diffusion of metal ions, a crystal structure exhibiting a superconducting phase can be completed at a lower temperature than in conventional methods.

In addition, it is possible to completely suppress the incorporation of these ions into the gel due to hydrolysis caused by basic substances containing alkali metals, and the final sintering temperature is higher than that reported so far. This method has a major advantage in that superconductors can be produced at relatively low temperatures without the usual reduction of divalent copper.

Two typical embodiments of the present invention are shown below.

(Example 1) Y(C104)3 0.2 mol/1. BaC1g
0. 2 no l/1. Cu (CI 0s)
Each aqueous solution of z 0.2 mol/1 was mixed at a ratio of 1:2:3 at room temperature. A 10% aqueous solution of hypochlorinated tetramethylammonium hydroxide was gradually added to this, and an aqueous solution of tetramethylammonium hypopromite was added to the resulting hydrogel, and the resulting oxide was suction filtered. This was pre-sintered at 300-500°C.

Furthermore, it was sintered at 600 to 900°C in an oxygen atmosphere.

The obtained powder was pressed at 400 to 600 Kg/cm. The pellets were further pressed at 920 to 10
It was sintered at 50°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 92, and the transition width, which is a measure of sample quality, was only 0.2.

(Example 2) LaC 1,0,2 mol/1. BaBrgO, 2 mol
/1. CuClto and 2 mol/l ethanol solutions were mixed at room temperature in a ratio of 1:2:3. A 10% methanol solution of tetramethylammonium hydroxide was gradually added to this, tetramethylammonium nitrate was added to the resulting gel, and the generated oxide was filtered with suction. This was pre-sintered at 300-400°C. Furthermore, it was sintered at 600 to 900°C in an oxygen atmosphere. The obtained powder was pressed at 400 to 600 kg/cm''. This pellet was further sintered at 920 to 1050°C in an oxygen atmosphere. The temperature change in conductivity of the slowly cooled sample was determined by the four-terminal AC method. . Completely superconducting at an absolute temperature of 37,
The transition width, which is a measure of sample quality, was only 0.2.

(Example 3) YCIs 0.2mo 1/1. BaC1゜0.2
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.

Tetramethylammonium peroxomonosulfate was added to the resulting hydrogel, and the generated oxide was suction filtered. This was pre-sintered at 300-400°C. Furthermore, it was sintered at 600 to 900°C in an oxygen atmosphere. The obtained powder was pressed at 400 to 600 kg/cm''.The pellet was further sintered at 920 to 1050°C in an oxygen atmosphere.The temperature change in conductivity of the slowly cooled sample was determined by the four-terminal AC method. It reached complete superconductivity at an absolute temperature of 83, and the transition width was only 0.5.

(Example 4) LaC1s o, 2mo 1/1,5rC1°0.2
mo! /1. CuClto, 2mol/l
The respective aqueous solutions were mixed at room temperature in a ratio of 11:4. A 10% aqueous solution of tetramethylammonium hydroxide was gradually added to this, and 9-tetramethylammonium hypochlorite was added to the resulting hydrogel, and the generated oxide was suction-filtered. This was pre-sintered at 300-400°C. Furthermore, it was sintered at 600 to 900°C in an oxygen atmosphere. The obtained powder was pressed at 400-600 Kg/cm''.

The pellets were further heated to 920 to 1050 in an oxygen atmosphere.
Sintered at °C. Temperature changes in electrical conductivity of the slowly cooled samples were determined using a four-terminal AC method. It reached complete superconductivity at an absolute temperature of 37, and the transition width was 2.5.

(Example 5) YCl3 0.2mo 1/1. BaBrzO,2mo
l/1. CuC]z 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, tetramethylammonium bromate was added to the resulting gel, and the generated oxide was filtered with suction. This was pre-sintered at 300-400°C. Furthermore, under an oxygen atmosphere, 600-900°C
Sintered with The obtained powder is 400-600Kg/cm
Pressed with 2. This pellet is further processed 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
At No. 2, complete superconductivity was achieved, and the transition width, which is a measure of sample quality, was only 0.2.

(Example 6) YCis 0.2mol/1. , BaC1゜0.2
mol/1. CuC1z 0.2m.

1/l of each aqueous solution was mixed at room temperature in a ratio of 1:2:3. A KOH aqueous solution was gradually added thereto, tetramethylammonium superoxide was added to the resulting hydrogel, and the generated oxide was suction filtered. After thorough washing with pure water, this was pre-sintered at 300 to 400°C. Furthermore, it was sintered at 600 to 900°C in an oxygen atmosphere. The obtained powder was pressed at 400 to 600 Kg/cm''.The pellets were further pressed under an oxygen atmosphere.

It was 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 86
It reached complete superconductivity in 2000, and the transition width, which is a measure of the quality of the sample, was 0.9.

(Example 7) Y(C104)3 0.2 mol/1. BaCL 0
,2 mol/1. CuC1=o.

Each 2 mol/l 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 the resulting hydrogel, tetramethylammonium hypobromite was added to the resulting hydrogel, and the resulting oxide was further heated in the solution to remove the resulting black precipitate. It was filtered by suction. This was pre-sintered at 300-400°C. Furthermore, it was sintered at 600 to 900°C in an oxygen atmosphere. The obtained powder was pressed at 400 to 600 kg/cm''.The pellet was further pressed at 92 kg/cm in an oxygen atmosphere.
Sintered at 0-1050°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 0.6.

(Example 8) YNo, 0.2mol/l, BaNOsO, 2m
ol/1. CuNOs 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.

Tetramethylammonium hypobromite was added to the resulting hydrogel, and the generated oxide was suction filtered. This was pre-sintered in air at 300-400°C. Furthermore, it was sintered at 600 to 900°C in an oxygen atmosphere. The obtained powder was pressed at 400 to 600 kg/cm''. This pellet was further sintered at 920 to 1050°C in an oxygen atmosphere. The temperature change in conductivity of the slowly cooled sample was determined by the four-terminal AC method. 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) YCl3 0.2mo 1/1. BaC1tO,2mo
l/1. CuCIz 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.

Tetramethylammonium hypobromite was added to the resulting hydrogel, and a small amount of polyvinyl alcohol aqueous solution was added to the resulting oxide, followed by suction filtration. This is 300-400
Temporary sintering was carried out at ℃. Furthermore, under an oxygen atmosphere, 600 to 90
Sintered at 0°C. The obtained powder is 400 to 600 kg/
Pressed at cm8. This pellet was further sintered at 920-1050°C in 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) YCl30,2mo I/1. BaCIto, 2 m
ol/1. CuClto, 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.

Further, tetramethylammonium hypobromite was added, ethylene glycol was added to the generated oxide, and the mixture was filtered with suction. After pre-sintering at 300-400°C, sintering was performed at 600-900°C in an oxygen atmosphere. 40% of the obtained powder
This pellet was further sintered at 920 to 1050°C in an oxygen atmosphere. The temperature change in conductivity of the slowly cooled sample was determined by the 4-iron alternating current method. Absolute temperature At 90°C, it reached complete superconductivity, 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.

Using Sc and lanthanide elements, alkaline earth elements such as Ba, and copper halides, nitrates, or perchlorates as raw materials, hydrolysis or solvolysis and chemical treatment with oxidizing agents are performed. The target substance was obtained. The results are summarized in Table 1.

(The following is a blank space) Table 1 (Effects of the invention) As explained above, in the 9 hydrolysis or solvolysis methods of the present invention and the production method using an oxidizing agent,
Through chemical treatment, a metal oxide mixture can be synthesized at low temperatures, and this can be sintered at a temperature that does not cause reduction of divalent copper, making it possible to easily reproduce high-temperature superconductors with good properties and sharp transition widths. It has the advantage of being easily fabricated. High-temperature superconductors, especially materials that become superconducting at temperatures above the liquid nitrogen temperature of 77 degrees absolute.

It is expected to find a wide range of industrial applications such as Josephson devices, power transport, and magnets that generate high magnetic fields, and the present invention will have an extremely large impact in terms of material processing in that it can be manufactured using low-temperature processes.

Claims (5)

[Claims] (1) General compositional formula (M1)x(M2)y(M3)zOw
(M1 is (B, Al, Ga, In, Tl, Sc, Y, L
a, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb
, Dy, Ho, Er, Tm, Yb, Lu), M2 is (Be, Mg
, Ca, Sr, Ba, Ra, Sn, Pb), M3 is Cu, x, y
, z, w are arbitrary atomic mole fractions) In the method for producing a superconductor, halides, nitrates, or perchlorates of M1, M2, and M3 are subjected to alkaline hydrolysis or solvolysis. 1. A method for producing a superconductor, comprising the steps of: adding an oxidizing agent to a product produced thereby; and then heat-treating the product to form a metal oxide. (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) The oxidizing agent is a halogen (fluorine, chlorine, bromine, iodine)
Or nitrate ions or ions containing halogen and oxygen (perchlorate ions, chlorate ions, hypochlorite ions, perbromate ions, bromate ions, hypobromite ions,
Patents characterized by being either hydrogen peroxide, sulfur-containing oxides (peroxomonosulfate ion, peroxodisulfate ion), or superoxide ion (periodate ion, iodate ion, hypoiodite ion) A method for producing a superconductor according to any one of claims 1, 2, 3, and 4.