JP2528117B2 - Superconductor manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing a superconductor.

(Prior Art) Conventionally, in the manufacturing method of a superconductor centered on a copper oxide system, () the corresponding metal oxide or metal carbonate is finely crushed in a mortar or the fine powder obtained is sieved. Or kneading with a suitable binder, 800-
Sintering at high temperature of 1200 ℃ (Wu, MK et al., Phys. Rev. Let
t.58,908 (1987)) () A method of adding sodium carbonate to a homogeneous aqueous solution of the corresponding metal nitrate, decarboxylating the resulting sparingly soluble metal carbonate at 800 ° C, and finally sintering at 1100 ° C or oxalate. In the same way as decarboxylation (Capon
e, DW et al. Appl. Phys. Lett. 50, 543 (1987)) are known. However, the method () includes the step of forming a solid solution of various corresponding metal oxides by a solid phase reaction,
From the common sense of chemical reactions, it takes a high temperature and a long time to synthesize a material having a uniform composition. For example, in the case of copper oxide, divalent copper is known to be converted to monovalent copper at a temperature of 1050 ° C or higher, which leads to loss of superconductivity. On the other hand, to obtain a superconductor with a uniform composition, 1100
It requires a high temperature above ℃. Since the method () uses a water-soluble metal nitrate as a starting material, the metal salts are uniformly mixed at room temperature. However, decarboxylation was performed at 800 ° C.
It is necessary to degas and sinter at a high temperature of 00 ℃. This tends to cause bubbles and cracks inside the superconductor.

(Problems to be Solved by the Invention) In order to improve such points, the present invention provides a method for producing a superconductor which enables homogeneous mixed sintering at low temperature.

(Means for Solving the Problems) In the present invention, in order to obtain a superconductor in which various metals corresponding to various desired metal ions are uniformly mixed, a halide or a metal nitrate is dissolved in water or an organic solvent. Isolation of the resulting homogeneous metal ion mixture with a hydrolyzing or solvolyzing agent soluble in water or an organic solvent to form a mixture of various corresponding metal hydrogels and metal organogels and the resulting product After that, the step of heat-treating the product in an oxygen atmosphere or an oxygen-free atmosphere to form a metal oxide is characterized by being included. At this time, heating can be appropriately performed for the purpose of enhancing the effect of the hydrolyzing agent or the solvolytic agent or for the purpose of sufficiently proceeding the reaction.

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

According to the second preferred embodiment, the ability to generate a hydroxide ion or an alkoxide ion in an aqueous solution or an organic solvent as a hydrolyzing agent or a solvolytic agent most preferably used in the first embodiment An organic compound having can be used. Most preferably, tetraalkylammonium hydroxide, trialkylsulfonium hydroxide, diazabicycloundecene, dimethylaminopyridine can be used.

According to the third preferred embodiment, an organic substance having two or more hydroxyl groups is added in advance during hydrolysis or solvolysis. By adding such an organic substance having two or more hydroxyl groups, it is possible to obtain a superconductor having a highly uniform composition.

According to another preferred embodiment, the polymer is added in advance or after hydrolysis or solvolysis,
The product is then heat treated in an oxygen atmosphere. According to this aspect, after the hydrolysis or solvolysis, it is easy to mold the superconductor into an arbitrary shape in the step of heating the isolated product in an oxygen atmosphere or an oxygen-free atmosphere. Become.

The heat treatment of the present invention will be summarized. In the heat treatment of the present invention, a mixed metal hydro or organogel synthesized by hydrolysis or solvolysis is further heat treated in the solution to directly give a fine mixed metal oxide. You may include the process of obtaining a preform. In addition, a step of heating the mixed metal hydrogel, organogel or fine mixed metal oxide fine particles synthesized in this way at a higher temperature to make the particles continuous, but at a temperature low enough to cause reduction of divalent copper. Also includes. In order to perform the sintering more completely, a small amount of polymer is allowed to coexist in the solution at the time of hydrolysis, and the generated gel or the metal oxide fine particles generated by the heat treatment of the solution is adsorbed to the coexisting polymer. A step of sintering a separated gel body or a metal oxide fine particle generated by heating thereof in which a small amount of a polymer is adsorbed may be included.

According to the present invention, a high-temperature superconductor can be uniformly mixed in a predetermined composition at around room temperature on an atomic scale, and dehydration or an alkyl part decomposition reaction can be completed by heat treatment of this, and therefore, a minimum of metal ions can be obtained. The crystal structure showing the superconducting phase can be completed at a lower temperature as compared with the conventional method by diffusion of. In addition, it is possible to completely suppress the incorporation of these ions into the gel, which is caused by hydrolysis with a basic substance containing an alkali metal, and finally, the sintering temperature tends to be higher than the previously reported sintering temperature. This has a great advantage in that the superconductor can be manufactured at a relatively low temperature without reducing the divalent copper.

 Below, the typical example of this invention is shown.

(Example 1) YC1 ₃ 0.2 mol / 1, BaCl ₂ 0.2 mol / 1, and CuCl ₂ 0.2 mol / 1 were mixed at a ratio of 1: 2: 3 at room temperature. A 10% aqueous solution of tetramethylammonium hydroxide was gradually added to this, and the resulting hydrogel was suction filtered. This is 300-400
Temporarily sintered at ℃. Furthermore, sintering was performed at 600-900 ° C in an oxygen atmosphere. The obtained powder was pressed at 400-600 Kg / cm ² . The pellets were further sintered at 920-1050 ° C under oxygen atmosphere. The temperature change of the conductivity of the annealed sample was determined by the 4-terminal AC method. The results are shown in Fig. 1. Absolute temperature 92K
It reached superconductivity completely, and the transition width, which is a measure of the quality of the sample, was only 0.2K.

(Example 2) LaCl ₃ 0.2 mol / 1, BaBr ₂ 0.2 mol / 1, CuCl ₂ 0.2 mol / 1 ethanol solutions were mixed at a ratio of 1: 2: 3 at room temperature. Tetramethylammonium hydroxide 10% methanol solution was gradually added to this, and the resulting gel was suction filtered. This was pre-sintered at 300-400 ° C. Furthermore, under oxygen atmosphere, 6
Sintered at 00-900 ° C. The obtained powder is 400-600 Kg / cm ²
Pressed. The pellets were further subjected to oxygen atmosphere at 920
Sintered at -1050 ° C. The temperature change of the conductivity of the annealed sample was determined by the 4-terminal AC method. Complete superconductivity is reached at an absolute temperature of 37K, and the transition width, which is a guideline for the quality of the sample, is only 0.
It was 2K.

(Example _{3) YC1 3 0.2mol / 1,} BaCl 2 0.2mol / 1, CuCl 2 each aqueous solution of 0.2 mol / 1 at room temperature 6: 4: mixed at a ratio of 1. A 10% aqueous solution of tetramethylammonium hydroxide was gradually added to this, and the resulting hydrogel was suction filtered. This is 300-400
Temporarily sintered at ℃. Furthermore, sintering was performed at 600-900 ° C in an oxygen atmosphere. The obtained powder was pressed at 400-600 Kg / cm ² . The pellets were further sintered at 920-1050 ° C under oxygen atmosphere. The temperature change of the conductivity of the annealed sample was determined by the 4-terminal AC method. Fully superconducting was achieved at an absolute temperature of 83K, and the transition width was only 0.5K.

(Example 4) LaCl ₃ 0.2 mol / 1, SrCl ₂ 0.2 mol / 1, and CuCl ₂ 0.2 mol / 1 aqueous solutions were mixed at a ratio of 9: 1: 4 at room temperature. A 10% aqueous solution of tetramethylammonium hydroxide was gradually added to this, and the resulting hydrogel was suction filtered. This is 300-4
It was temporarily sintered at 00 ° C. Furthermore, under oxygen atmosphere, 600-900 ℃
Sintered. The obtained powder was pressed at 400-600 Kg / cm ² . The pellets were further sintered at 920-1050 ° C under oxygen atmosphere. The temperature change of the conductivity of the annealed sample was determined by the 4-terminal AC method. It reached superconductivity completely at an absolute temperature of 37K and the transition width was 2.5K.

(Example 5) YCl ₃ 0.2 mol / 1, BaBr ₂ 0.2 mol / 1, and CuCl ₂ 0.2 mol / 1 were mixed at a ratio of 1: 2: 3 at room temperature. Tetramethylammonium hydroxide 10% methanol solution was gradually added to this, and the resulting gel was suction filtered. This was pre-sintered at 300-400 ° C. Furthermore, under oxygen atmosphere, 600
Sintered at -900 ° C. The obtained powder was pressed at 400-600 Kg / cm ² . The pellets were further subjected to an oxygen atmosphere at 920-
Sintered at 1050 ° C. The temperature change of the conductivity of the annealed sample was determined by the 4-terminal AC method. The results are shown in Fig. 1. It reached superconductivity completely at an absolute temperature of 92K, and the transition width, which is a measure of the quality of the sample, was only 0.2K.

(Example 6) YC1 ₃ 0.2 mol / 1, BaCl ₂ 0.2 mol / 1, CuCl ₂ 0.2 mol / 1 aqueous solutions were mixed at a ratio of 1: 2: 3 at room temperature. Aqueous KOH solution was gradually added to this, and the resulting hydrogel was suction filtered. After thoroughly washing with pure water, this was pre-sintered at 300-400 ° C. Furthermore, sintering was performed at 600-900 ° C in an oxygen atmosphere. The obtained powder was pressed at 400-600 Kg / cm ₂ . The pellets were further sintered at 920-1050 ° C under oxygen atmosphere. The temperature change of the conductivity of the annealed sample was determined by the 4-terminal AC method. Complete superconductivity was reached at an absolute temperature of 86K, and the transition width, which is a measure of the quality of the sample, was 0.9K.

(Example 7) YCl ₃ 0.2 mol / 1, BaCl ₂ 0.2 mol / 1, and CuCl ₂ 0.2 mol / 1 were mixed at a ratio of 1: 2: 3 at room temperature. Tetramethylammonium hydroxide 10% aqueous solution was gradually added thereto, and the resulting hydrogel was further heated in the solution, and the resulting black precipitate was suction filtered. This is 300-400 ℃
Was temporarily sintered in. Furthermore, sintering was performed at 600-900 ° C in an oxygen atmosphere. The obtained powder was pressed at 400-600 Kg / cm ² .
The pellets were further sintered at 920-1050 ° C under oxygen atmosphere. The temperature change of the conductivity of the annealed sample was determined by the 4-terminal AC method. Full superconductivity was reached at an absolute temperature of 90K, and the transition width, which is a measure of the quality of the sample, was 0.6K.

(Example 8) YNO ₃ 0.2 mol / 1, BaNO ₃ 0.2 mol / 1, and CuNO ₂ 0.2 mol / 1 were mixed at a ratio of 1: 2: 3 at room temperature. A 10% aqueous solution of tetramethylammonium hydroxide was gradually added to this, and the resulting hydrogel was suction filtered. This in the air 30
Pre-sintered at 0-400 ° C. Furthermore, under oxygen atmosphere, 600-90
Sintered at 0 ° C. The obtained powder was pressed at 400-600 Kg / cm ² . The pellets were further subjected to an oxygen atmosphere at 920-1050.
Sintered at ° C. The temperature change of the conductivity of the annealed sample was determined by the 4-terminal AC method. The results are shown in Fig. 1. Absolute temperature
Full superconductivity was reached at 92K, and the transition width, which is a measure of the quality of the sample, was only 0.2K.

(Example 9) YCl ₃ 0.2 mol / 1, BaCl ₂ 0.2 mol / 1, CuCl ₂ 0.2 mol / 1 aqueous solutions were mixed at a ratio of 1: 2: 3 at room temperature. A small amount of an aqueous solution of polyvinyl alcohol was added to this, and a 10% aqueous solution of tetramethylammonium hydroxide was gradually added, and the resulting hydrogel was suction filtered. This was pre-sintered at 300-400 ° C. Furthermore, sintering was performed at 600-900 ° C in an oxygen atmosphere.
The obtained powder was pressed at 400-600 Kg / cm ² . The pellets were further sintered at 920-1050 ° C under oxygen atmosphere. The temperature change of the conductivity of the annealed sample was determined by the 4-terminal AC method. It reached superconductivity completely at an absolute temperature of 93K, and the transition width, which is a measure of the quality of the sample, was only 0.3K.

(Example 10) YCl ₃ 0.2 mol / 1, BaCl ₂ 0.2 mol / 1, and CuCl ₂ 0.2 mol / 1 were mixed at a ratio of 1: 2: 3 at room temperature. A 10% aqueous solution of tetramethylammonium hydroxide was gradually added to this, and the resulting black precipitate was suction filtered by heating. This was kneaded with a small amount of polyvinyl alcohol solution and pre-sintered at 300-400 ℃.

Further, it was sintered at 600-900 ° C in an oxygen atmosphere. The obtained powder was pressed at 400-600 Kg / cm ² . The pellets were further sintered at 920-1050 ° C under oxygen atmosphere. The temperature change of the conductivity of the annealed material was determined by a 4-terminal AC method. Fully superconducting was achieved at an absolute temperature of 90K, and the transition width, which is a measure of the quality of the sample, was only 0.4K.

In the same manner, Y, Sc and lanthanide-based elements charged to a predetermined composition, alkaline earth elements such as Ba,
Then, using a copper halide or nitrate as a raw material, hydrolysis was carried out to obtain a target substance. The results are summarized in the table below.

(Effects of the Invention) As described above, according to the low temperature production method via the hydrolysis method or solvolysis of the present invention, it is possible to sinter at a temperature at which the reduction of divalent copper does not occur and the hydrogel at a low temperature. It has the advantage that a high-temperature superconductor with a sharp transition width and good characteristics can be produced with good reproducibility by dehydration or by temporary sintering accompanied by thermal decomposition of the alkyl part of the organogel. High-temperature superconductors, especially materials that reach superconductivity above a liquid chamber temperature of 77K absolute, are expected to have a wide range of industrial applications such as Josephson devices, power transfer, and high magnetic field generating magnets.
In terms of material processing, the present invention has an extremely large impact in that it can be manufactured by a low temperature process.

[Brief description of drawings]

FIG. 1 shows Y _1.0 Ba _2.0 Cu produced by the method of the present invention.
FIG. 3 is a diagram showing resistance-temperature characteristics of a _3.0 oxide superconductor.

Claims (6)

(57) [Claims] 1. A general composition formula (M1) x (M2) y (M3) zOw (M
1 is (B, A1, Ga, In, T1, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, T
b, Dy, Ho, Er, Tm, Yb, Lu) one or more elements selected from the group consisting of (Be, Mg, Ca, Sr, Ba, Ra, Sn, Pb) One or more elements selected from, M3 is Cu, x, y,
(z, w are arbitrary atomic mole fractions) In the method for producing superconductors, alkali hydrolysis or solvent addition of M1, M2, M3 halides or nitrates with or without heating After degrading and isolating the resulting product,
A method for producing a superconductor, comprising the step of subjecting the product to a metal oxide by heat treatment in an oxygen atmosphere or an oxygen-free atmosphere. 2. The method for producing a superconductor according to claim 1, wherein the decomposing agent for alkali hydrolysis or solvolysis does not contain an alkali metal. 3. A decomposition agent for alkali hydrolysis or solvolysis is an organic compound having an ability to generate a hydroxide ion or an alkoxide ion in an aqueous solution or an organic solvent. 2. A method for producing a superconductor according to claim 1 or 2. 4. The decomposition agent for alkali hydrolysis or solvolysis is tetraalkylammonium hydroxide, trialkylsulfonium hydroxide, diazabicycloundecene, dimethylaminopyridine. 4. A method for producing a superconductor according to any one of the first, second and third aspects of the above. 5. An organic substance having two or more hydroxyl groups is previously added at the time of hydrolysis or solvolysis, wherein the first, second, third and fourth aspects are set forth.
Item 8. A method for producing a superconductor according to any one of the items. 6. The method according to claim 1, further comprising the step of adding a polymer in advance or after hydrolysis or solvolysis, and then subjecting the product to heat treatment in an oxygen atmosphere. The method for producing a superconductor according to any one of paragraphs 3, 4, and 5.