JPH01298057A - Production of high-temperature superconducting ceramic compact - Google Patents

Abstract

PURPOSE:To remarkably improve the critical current density of the title compact by impregnating the high-temp. superconducting ceramic sintered compact, etc., with a soln. contg. a metallic element compd. corresponding to the metallic element composition of the sintered compact, and sintering the compact. CONSTITUTION:The powders of A2O3 (A is a rare-earth element, etc.), BCO3 (B is an alkaline-earth element), and CuO are crushed, mixed, and sintered to obtain high-temp. superconducting ceramic raw powder (a) shown by the formula (A is >=1 kind among Y, La, Nd, etc., B is >=1 kind between Sr and Ba, 0.8<x<1.2, 1.6<y<2.4, and 0<z<0.5) and having >=- deg.C superconducting temp. The powder (a) is then compacted to form a green compact (b), or the green compact (b) is calcined at 500-950 deg.C to obtain a calcined body (c). A metallic element compd. (d) (such as a metal naphthenate) corresponding to the metallic element composition of the calcined body (c) is dissolved in toluene, etc., by 3-40wt.% to obtain a soln. (e). The calcined body (c) is then impregnated with the soln. (e), dried, and then sintered at 500-1000 deg.C in an O2 atmosphere to produce a high-temp. superconducting ceramic compact.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a high-temperature superconducting ceramic molded body.

[Prior art and its problems]

Bj,
High-temperature superconducting ceramics based on bismuth-alkaline earth elements-copper oxides, such as the -Ca-5r-Cu-0 system, are expected to be used in a wide range of fields such as transportation, heavy electrical equipment, computers, and medical equipment. ing.

These oxide-based high-temperature superconducting ceramics also become superconducting when cooled with an inexpensive coolant such as liquid nitrogen, so they can be used instead of Nb-Ti-based superconducting alloys, which only exhibit superconducting state in liquid helium. If it can be used for superconducting nets, etc.

There are great economic benefits.

In particular, high-temperature superconducting ceramics based on bismuth-alkaline earth elements-copper oxides are said to be relatively stable against moisture and carbon gas in the air; - Since expensive rare earth elements are not used as in copper oxide-based high-temperature superconducting ceramics, it is advantageous in practical terms.

However, in any case, the problem with the superconducting ceramics that have been produced so far is that they have a low critical current density, a wide temperature range (and a lack of steepness) of the transition from normal conductivity to superconductivity.

It has been pointed out that these problems are due to the fact that superconducting ceramics are porous and have low density, and that the obtained superconducting ceramics are a mixture of superconducting ceramics with different physical properties such as chemical composition and critical temperature. has been done.

Until now, oxide-based high-temperature superconducting ceramic sintered bodies have been produced by pre-sintering, pulverizing, and molding raw material powders prepared by dry mixing, wet mixing, multistage wet methods, sol-gel methods, flux methods, or hydrothermal methods. , and sintering.

Among these, the dry mixing method and the wet mixing method are technically easy and highly safe methods, but the resulting raw material powder has a large particle size of 1 to 5 μm or more, and the particle size distribution is not uniform. ,
Furthermore, the variation in components is wide 11°.On the other hand, the multi-stage wet method is a method in which a solution of a metal element compound corresponding to the metal element composition of superconducting ceramics is brought into contact with a precipitate forming agent in stages to form a co-precipitate. Therefore,
The obtained raw material powder is very fine particles with a particle size of 1 μm or less. Therefore, the superconducting ceramics obtained therefrom have a relatively high density.

Methods for manufacturing superconducting ceramic sintered bodies from superconducting ceramic raw material powder obtained by each of the above methods include pressure forming, rapid cooling forming of the melt into a wire or tape, and packing the raw material powder into a metal-clad tube. There are known forming methods such as forming into a thin wire by drawing, mixing raw material powder with an organic binder, a plasticizer, etc., and forming into a wire by extrusion.

Even if the raw material powder for superconducting ceramics is prepared by any of the above methods and the raw material powder is molded, there is a problem that the obtained high-temperature superconducting ceramic molded body has a low density and a low critical current density.

[Technical means to solve problems]

The present inventors have completed extensive research to solve the above-mentioned problems and have completed the present invention.

The present invention is a high-temperature superconductor characterized in that a molded green body or a molded sintered body of high-temperature superconducting ceramics is impregnated with a solution containing a metal element compound corresponding to the metal element composition of the high-temperature superconducting ceramic, and then sintered. This is a method for manufacturing a ceramic molded body.

The high-temperature superconducting ceramic used in the present invention is not particularly limited, including its type, but it is preferable to have a superconducting temperature as high as possible. Generally, the temperature is -°C or higher, preferably -°C or higher. Examples of such materials include rare earth element-alkaline earth element-copper oxide-based high-temperature superconducting ceramics and bismuth-alkaline earth element-copper oxide-based high-temperature superconducting ceramics.

Rare earth element-alkaline earth element-copper oxide system high temperature superconducting ceramics has the following general formula, 1zBycu30□-2
It is expressed as In the formula, A is Y, La, Nd,
Sm, Eu, Gd, Dy.

) at least one rare earth element selected from to, Er, Tm, Yb and Lu, B is Sr and 8
At least one kind of alkaline earth element selected from a is shown.

In the above formula, X is larger than 0.8 and smaller than 1.2, y is larger than 1.6 and smaller than 2.4, and z is larger than O and smaller than 0.5.

Bismuth-alkaline earth element-copper oxide-based high-temperature superconducting ceramics are represented by the following general formula, BiAχCuyOz. The characters in the formula represent at least one alkaline earth element selected from Mg, Ca, Ba and Sr. As A, it is preferable to use a combination of two of the above alkaline earth elements, and particularly preferable is a combination of Ca and Sr. In the above formula, X is greater than l and less than 4, and y is greater than 0.8 and 2.5
z is a number greater than 4 and less than 7. When two types of alkaline earth elements are used in combination as A, the composition ratio of the two types of elements is preferably larger than 0.5 and smaller than 1.5, and particularly preferably around 1.

The raw material powder for producing the molded green bodies and molded sintered bodies of high-temperature superconducting ceramics used in the present invention can be prepared using conventional methods such as dry mixing method, wet mixing method, multistage wet method, sol-gel method, flux method, or hydrothermal method. It can be manufactured by known methods.

The dry mixing method uses powders of oxides or carbonates that are components of superconducting ceramics, such as powders of A, 01 (A represents a rare earth element or bismuth), BeO2 (B represents an alkaline earth element), and CuO. As the starting material,
This is a method of preparing raw material powder for superconducting ceramics by crushing and mixing with a ball mill, grinder, pestle, mortar, etc., and then sintering.

On the other hand, the wet mixing method is a method in which a solvent that does not react with and is substantially insoluble in the starting materials is added to the same starting materials as in the dry method, and the mixture is mechanically combined.

In the multi-stage wet method, an aqueous solution or an organic solvent solution of a metal element compound corresponding to the metal element composition of the superconducting ceramic is brought into contact with a precipitant in stages to form a coprecipitate, which is then fired to form the superconducting ceramic. This is a method for preparing raw material powder.

A multi-stage wet method is preferred as a method for preparing the raw material powder.

In this method, hydroxides, hydrochlorides, nitrates, organic acid salts, alkoxides, etc. can be used as the metal element compound.

As a solvent, water, alcohols, ethers, ketones, esters, hydrocarbons, halogenated hydrocarbons, N-
Methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, dimethylsulfoxide, etc. can be used.

As the precipitant, an aqueous caustic alkali solution, aqueous ammonia, ammonium carbonate, oxalic acid, ammonium oxalate, amines, oximes, water, etc. can be used. These precipitants may be used alone or in combination with two
You may use combinations of more than one species.

The raw material powder for high-temperature superconducting ceramics obtained by each of the above methods is pre-sintered at 500 to 950°C, or molded by a commonly known method without pre-sintering to produce unsintered high-temperature superconducting ceramics. The compacted green body can be further sintered into a shaped sintered body.

Specific examples of molding methods include (1) a method in which raw material powder is molded under heat and pressure, or simply under pressure;

(2) A method of heating and melting the raw material powder to 1000°C or higher and rapidly cooling and forming the melt into a wire rod or tape. (3) A method of filling the raw material powder into a metal clad tube and forming it into a drawn wire rod or tape by machining. (4) A method of mixing molding aids such as an organic binder and plasticizer with the g material powder and forming this caking mixture into a wire rod by extrusion; (5) A method of mixing the raw material bundle with an organic binder, a plasticizer, an organic Alternatively, examples include a method of forming a paste into a thin film by forming it into a paste with an inorganic solvent, applying it to a support, and sintering it.

In the method of the present invention, the molded green body obtained by each of the above-mentioned methods or the molded green body is heated at a high temperature, for example, at 50°C.
A shaped sintered body obtained by sintering at 0 to 950°C is impregnated with a solution of a metal element compound corresponding to the metal element composition of the high-temperature superconducting ceramic.

The preparation method and impregnation method for the solution of the metal element compound used in the present invention will be explained below.

The solution of metal element compounds is obtained by dissolving a plurality of compounds of metal elements corresponding to the desired high-temperature superconducting ceramic in a solvent according to the composition ratio of the corresponding metal elements.

Generally, as a metal element compound, 1000 degrees Celsius or less,
Particularly preferred are those that thermally decompose into oxides at 200 to 900°C, such as oxides, hydroxides, halides,
Examples include organic acid salts, inorganic acid salts, alkoxides, chelate compounds, and the like. Particularly preferred metal element compounds include:
Contains a metal-oxygen-carbon bond. Specific examples include naphthenic acid, octylic acid, caprylic acid, stearic acid, lauric acid, acetic acid, propionic acid, citric acid, lactic acid, phenol, catechol, and benzoic acid. acids, metal salts of organic or inorganic acids such as salicylic acid, ethylenediaminetetraacetic acid, nitric acid, carbonic acid, and hydrochloric acid, ethanol.

Propatool, butanol, octatool, ethylene glycol, glycerin, 2-penten-4-one-2-
Examples include metal alkoxides of alcohols such as ol, chelate compounds such as metal acetylacetonates, and the like.

If the metal element compound does not have a metal-oxygen-carbon bond, by selecting an organic acid, alcohol, acetylacetone, nitric acid, etc. as the solvent, the two can be reacted in a mixed solution to form gold F+c organic acid salt, metal It can be converted into alkoxides, metal chelate compounds, nitrates, etc.

The metal concentration in the solution is not particularly limited, and its upper limit is determined by the solubility of the metal element compound, etc., but in general,
It is 3 to 40% by weight in terms of metal element compound. Furthermore, an appropriate amount of a polymeric substance or the like can be added to this solution as a viscosity modifier.

The solvent may be any solvent as long as it can dissolve the metal element compound as described above or react with it as described above if necessary. For example, hydrocarbons such as hexane, octane, toluene, and tetralin, alcohols such as methanol, ethanol, propatool, butanol,
Acetone, methyl ethyl ketone, acetylacetone and other ketones, ethers, aldehydes, formic acid, acetic acid, propionic acid, lauric acid, stearic acid, naphthenic acid,
Examples include organic acids such as oleic acid, oxalic acid, and phenol, esters, amines, heterocyclic substances such as pyridine and furfural, aqueous nitric acid, aqueous ammonia, and water. These solvents are appropriately selected either singly or in combination of two or more, depending on the type of metal element compound specifically used.

The method for impregnating the molded green body or molded sintered body of high-temperature superconducting ceramics with a solution of a metal element compound includes various methods such as a dipping method, a spray method, and a brush coating method, and is not particularly limited. During this impregnation, pressure can also be used in combination.

After the impregnation, the molded body is dried and sintered by a conventional method, thereby converting the metal element compound in the molded body into a superconducting composite metal oxide. Sintering of a molded green body or a molded sintered body of superconducting ceramics containing a metal element compound is preferably carried out in an oxygen-containing atmosphere, and the sintering temperature is generally in the range of 500 to 1000°C. After sintering, a high temperature superconducting ceramic sintered body with a high critical current density can be obtained by slowly cooling it to room temperature.

As described above, after impregnating the molded body with a solution of a metal element compound, drying the molded body, and sintering, the metal element compound is converted by repeating impregnation with a solution of a metal element compound, drying, and sintering again. A large amount of the superconducting composite metal oxide can be incorporated into the molded body. Further, when the above impregnation operation is repeated, the heat treatment after drying the molded body can be performed at a temperature equal to or higher than the temperature at which the metal element compound decomposes, except for the final sintering heat treatment. For example, when the metal element compound contains an organic component, heating conditions of 200 to 600°C are employed. If the metal element compound is a carbonate, nitrate, hydroxide, or halide that does not contain organic components, 500-100
It is preferable to adopt heating conditions of 0°C.

In the present invention, in order to obtain a superconducting ceramic molded body with excellent superconducting properties, it is particularly preferable to repeat the operations of impregnation, drying, and heat treatment at least twice or more.

〔Example〕

Examples of the present invention are shown below.

Example 1 0.1 mol of yttrium chloride and 0.2 mol of barium chloride were dissolved in 10,100 O of water, and 1,000 +++ u of 3N ammonium carbonate aqueous solution was added thereto to produce a coprecipitate.

After washing this coprecipitate with distilled water, basic copper carbonate (Cu2
Co, (011)2] 0.3 mol aqueous solution 1000
d, and an ethanol solution of 1 mol of ethylenediamine 50
0- was added to form a coprecipitate, and this precipitate was washed with water and dried to obtain a powder for temporary sintering.

This powder was pre-sintered in air at 850° C. for 1 hour, and this powder was molded at a pressure of It/a#.

The above molded body was sintered in air at 900° C. for 1 hour and slowly cooled to room temperature to obtain a superconducting ceramic molded sintered body.

Next, a solution (40 % by weight) (solution A) was prepared, and the superconducting ceramic molded sintered body was immersed in this solution for one hour or more.

The obtained impregnated sintered body was dried at 100° C. for 1 hour, then heat-treated in air at 500° C. for 1 hour, and then immersed again in the solution A for 1 hour or more. After drying at 100°C for 1 hour, it was sintered in air at 500°C for 1 hour and at 850°C for 6 hours, and slowly cooled to room temperature.

The obtained high-temperature MA conductive ceramic molded gas has a viscous density of 5.45 g/i, a critical temperature (Tc) of 94,
The critical current density was 385 A/cd.

Example 2 A solution of 0.4 mol of oxalic acid dissolved in 500 + nQ of water was added to 500 ml of 3N ammonia water to prepare a precipitate.

This precipitant was added to an aqueous solution of 0.2 mol of bismuth nitrate.
00 mQ, 500 mQ of an aqueous solution of 0.2 mol of calcium nitrate, 500 m of an aqueous solution of 0.2 mol of strontium nitrate, and 500 mQ of an aqueous solution of 0.4 mol of copper chloride were added dropwise to form precipitates.

These precipitates were washed with water, dried, and then mixed and ground in a ball mill. This mixed powder was pre-sintered at 700°C, and after molding,
It was sintered at 00°C to obtain a superconducting ceramic molded sintered body.

Next, bismuth naphthenate, calcium naphthenate, strontium naphthenate, copper naphthenate were added to Bi:Ca:
A solution (5% by weight) dissolved in a toluene solvent with an elemental ratio of Sr:Cu=1:1:1:2 (solution B) is prepared, and the above superconducting ceramic molded sintered body is immersed in this solution B for at least 1 hour. did.

The obtained impregnated sintered body was dried at 100° C. for 1 hour, then heat-treated in air at 500° C. for 1 hour, and then immersed again in the above solution B for 1 hour or more. After drying at 100°C for 1 hour, it was cured in air at 500°C for 1 hour, in oxygen at 870°C for 2 hours, and slowly cooled to room temperature.

The density of this high temperature superconducting ceramic molded sintered body is 5.5
], g/ffl, and the critical temperature (Tc) is 104,
The critical current density was 44OA/d.

Example 3 Inolium acetylacetonate, barium acetylacetonate, copper acetylacetonate Y:Ba:
Pyridine and propionic acid (Cu=1:2:3 element ratio)
Solution (9% by weight) dissolved in a mixed solvent with a weight ratio of 5:3)
(Solution C) was prepared, and the superconducting ceramic molded sintered body shown in Example 1 was immersed in this solution C for over 1 hour, dried,
It was heated, then immersed and dried again in the same manner, and finally sintered to obtain a molded sintered body of high-temperature superconducting ceramics.

The density of this high temperature superconducting ceramic molded sintered body is 5.5
0g/ffl, critical temperature (Tc) is 95K, and critical current density is 395A/c! Met.

Example 4 The molded green body obtained by the method of Example 1 was immersed in solution C shown in Example 3 for more than 1 hour, and then heated at 100°C for 1 hour.
After drying for an hour, it was heat-treated in air at 500° C. for 1 hour, and then immersed in solution C again for more than 1 hour. After drying at 100°C for 1 hour, it was sintered in air at 500°C for 1 hour and at 850°C for 6 hours, and slowly cooled to room temperature.

The density of this high-temperature superconducting ceramic molded sintered body is 5.4
8 g/cJ, critical temperature (Tc) was 95 K, and critical current density was 395 A/ffl.

Example 5 The high-temperature superconducting ceramic molded sintered body obtained in Example 4 was again impregnated with Solution C shown in Example 3, dried, and heat treated.

The density of the obtained high-temperature superconducting ceramic molded sintered body was 5.
．． 55 g/cd, critical temperature (Tc) was 95 K, and critical current density was 438 A/d.

Example 6 The molded green body obtained by the method of Example 2 was impregnated, dried, and sintered in the same manner as in Example 2. The density of this high-temperature superconducting ceramic molded sintered body was 5.5.
2g/crt? , and the critical temperature (Tc) is IO2,
The critical current density was 446 A/cJ.

Example 7 The high temperature superconducting ceramic molded sintered body obtained in Example 6 was again impregnated, dried, and heat treated in the same manner as in Example 2.

The density of the obtained high-temperature superconducting ceramic molded sintered body was 5.
．． 60g/ffl, critical temperature (Tc) is 105K
, the critical current density was 482 A/cd.

Comparative Example 1 Example 1 without impregnation with metal compound solution
The density of the superconducting ceramic molded sintered body is 5.0.
g/ad, critical temperature (Tc) was 94 K, and critical current density was 310 A/cJ.

Comparative Example 2 Example 2 without impregnation with metal compound solution
The density of the superconducting ceramic molded sintered body is 5.4
g/ci, the critical temperature (Tc) was 103K, and the critical 'Iπ flow density was 3g0A/a#.

(Effects of the Invention) As described above, the critical current density of the high temperature superconducting ceramic according to the present invention is significantly increased.

Compared to conventional products, it can be used advantageously in various fields.

Designated agent Hirofu, former director of the Institute of Chemical Technology, Agency of Industrial Science and Technology, patent attorney Satoshi Ikeura, amended procedure July 77, 1988, Commissioner of the Japan Patent Office, Yoshi 1) Moon Yi, 1988 patent Application No. 129588 2, Title of the invention: Process for manufacturing high-temperature superconducting ceramic molded bodies 3, Relationship to the amended case Patent applicant address: 1-3-1 Kasumigaseki, Chiyoda-ku, Tokyo Name
(114) Director of the Agency of Industrial Science and Technology Juzo Iizuka (one idiot) 4. Sub-Agent 151 Address 1-58-10 Yoyogi, Shibuya-ku, Tokyo -
Nishiwaki Building No. 113 Name (7450) Patent attorney Toshiaki Ikeura Telephone (370)
No. 2533 5, Date of amendment order Voluntary 6, Number of claims increased by amendment 07, Contents of amendment ``Detailed description of the invention'' column 7' of the specification:,'
,", ,,',"H2i)°゛(G367.19 8. Contents of amendment The following amendments will be made to the specification of this application.

(1) On page 5, line 3, “is above −℃, preferably −
"at temperatures above -253°C, preferably -196°C or above" should be corrected.

Yoshi, Commissioner of the Japan Patent Office 1) Mr. Moon Takeshi, Indication of the case Patent Application No. 129588 of 1988 2, Name of the invention Method for manufacturing high temperature superconducting ceramic molded body 3, Person making the amendment Relationship with the case Patent applicant address 1-3-1 Kasumigaseki, Chiyoda-ku, Tokyo Name
(11/l) Juzo Iizuka, Director of the Agency of Industrial Science and Technology (and 1 other person) 4. Sub-Agent 151 Address 1-58-10 Yoyogi, Shibuya-ku, Tokyo -
Nishiwaki Building 113 Name (7450) Patent Attorney Toshiaki Ikeura Telephone (370) 2533 5. Date of amendment order Voluntary 6. Target of amendment Column ``7. Contents of amendment'' of procedural amendment dated July 19, 1988 7. Contents of the amendment Dn ρ B Procedural amendment July 19, 1988 Director General of the Patent Office Yoshi 1) Moon Takeshi 1. Indication of the case 1988 Patent Application No. 129588 2. Name of the invention High-temperature superconducting ceramic molded body Manufacturing method 3, relationship with the case of the person making the amendment Patent applicant address: 1-3-1 Kasumigaseki, Chiyoda-ku, Tokyo Name
(114) Juzo Iizuka, Director of the Agency of Industrial Science and Technology (and 1 other person) 4. Sub-Agent 151 Address IO No. 113, Nishiwaki Building, 1-F 158 Yoyogi, Shibuya-ku, Tokyo Name (7450) Toshiaki Ikeura, Patent Attorney Telephone ( 370) 2533 No. 5, date of amendment order Voluntary

Claims (1)

[Claims] (1) impregnating a molded green body or a molded sintered body of high-temperature superconducting ceramics with a solution containing a metal element compound corresponding to the metal element composition of the high-temperature superconducting ceramics;
A method for producing a high-temperature superconducting ceramic molded body, which is characterized by sintering.