JPH01133922A - Production of raw material powder for oxide superconductor - Google Patents

Abstract

PURPOSE:To obtain raw material powder for a superconductor having a fine and uniform particle size at low temp. and in a short time by mixing an alcoholic soln. of Ba(OH)2 with an alcoholic soln. of a specified nitrate, and decomposing thermally obtd. coprecipitate. CONSTITUTION:An alcoholic soln. (A) of a nitrate of copper and a lanthanide metal is mixed with an alcoholic soln. (B) of Ba(OH)2 and coprecipitation is caused. Aimed powder is obtd. by decomposing obtd. coprecipitate thermally. Suitable concn. of the soln. (A) to be used is usually 5-100g/100g solvent considering the improvement of productivity and the yield of coprecipitated component, etc. Since BaCO3 is frequently contained as impurity in commercially available Ba(OH)2 to be used in the soln. (B), it is preferred to use a soln. obtd. by dissolving BaO of high purity prepd. previously by heat-treating BaO or by decomposing BaCO3 thermally, in alcohol.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a novel method for producing oxide superconductor raw material powder.

[Prior art/problems to be solved by the invention] It was discovered that a copper-barium-yttrium complex oxide having an oxygen-deficient perovskite structure is a superconductor that exhibits a superconducting transition temperature exceeding the temperature of liquid nitrogen. Since liquid nitrogen, which is inexpensive and has good cooling efficiency, can be used as a coolant, it is expected to be put to practical use in many applications such as semiconductor devices using superconductors, magnets, energy storage devices, magnetic shields, and sensors. Vigorous research is underway in all areas.

The copper-barium-yttrium composite oxide is a ceramic, and there is no precipitation of the second component at the grain boundaries of the sintered body, and the expected performance cannot be ensured unless the density of the sintered body is increased. In addition, this composite oxide has a crystal structure in which, for example, the atomic ratio of yttrium/barium/copper is approximately 1/2/3, and the content ratio of oxygen to this ratio is 6.5 to 7.0 in atomic ratio. It is necessary that the composition and crystal structure be extremely limited, that is, the orthorhombic crystal structure. Deviation from this composition and crystal structure will affect the superconducting transition temperature, critical current value, and critical magnetic field, which are the performance characteristics of a superconductor. Either decreases l.

However, it is becoming clear that sintering conditions and precise synthesis methods for raw material powder are important. That is, it is desired that the raw material powder be homogeneous with a predetermined metal atomic ratio (hereinafter referred to as having excellent stoichiometry), and be fine with a uniform particle size.

In order to synthesize this raw material powder using the solid phase reaction method, which is currently known as the conventional method for synthesizing raw material powder for oxide superconductors, it is necessary to mix copper oxide, barium carbonate, and rare earth metal oxides. Afterwards, unless calcining and pulverization are repeated several times at a high temperature of around 950°C for a long period of time, the raw material powder cannot be changed to a single phase in X-rays, and grain growth inevitably occurs, resulting in particle sizes of several tens of degrees. There is a problem that the powder becomes large and has poor sinterability.

Therefore, compared to the above-mentioned solid phase reaction method, processes are being considered that have better stoichiometry, have finer and more uniform particles, and can change the desired oxide by firing at a lower temperature and in a shorter time. The oxalate coprecipitation method, carbonate coprecipitation method, gel decomposition method, etc. have been proposed.

However, in addition to the problem that these methods use water, which oxide superconductors dislike, there are still problems that need to be solved as described below.

That is, the oxalate coprecipitation method is a method of obtaining a coprecipitate by dropping an aqueous solution of oxalic acid or an oxalic acid compound into a mixed aqueous solution or an ethyl alcohol-water mixed solution of copper nitrate, barium nitrate, and rare earth metal nitrate. , delicate pH control is required to maintain good stoichiometry and is very difficult to implement.

In addition, the carbonate coprecipitation method is a method in which an alkali metal carbonate such as potassium carbonate is added to a mixed aqueous solution of copper nitrate, barium nitrate, and rare earth metal nitrate to neutralize and coprecipitate. Careful cleaning is required to remove alkali metal components remaining in the target compound, and even if thorough cleaning is performed, there is a risk that alkali metal may remain in the target compound.

Furthermore, the gel decomposition method is a method in which citric acid and ethylene glycol are added to a mixed aqueous solution of nitrates of various metals and heated to create a gel-like substance, which is then thermally decomposed. In some cases, carbon remains even after the firing process.

Moreover, in all three methods, the target product cannot be obtained directly through the calcination process, but instead is produced through a mixture of barium carbonate, copper oxide, and rare earth metal oxide as an intermediate, similar to the solid-phase reaction method. It is known that barium carbonate, which is relatively stable against heat, inevitably causes the firing temperature to be high, and that it occurs when a large amount of raw material is fired at once or in a deep-bottomed container. There is a problem in that it is difficult to achieve a single exchange due to the rate-limiting diffusion of carbon dioxide gas.

[Means for Solving Problems] The present inventors have conducted intensive studies on methods for solving these problems, particularly methods for synthesizing oxide superconductor raw material powder that does not produce barium carbonate as an intermediate product. Barium hydroxide is soluble in lower alcohols such as methyl alcohol, and barium hydroxide reacts with copper nitrates and rare earth metal nitrates that are soluble in lower alcohols, making it difficult to dissolve in organic solvents such as lower alcohols. Focusing on making barium nitrate, it was mixed with a copper compound,
The inventors have discovered that it is possible to co-precipitate barium compounds and rare earth metal compounds, and have arrived at the present invention.

That is, the present invention involves mixing an alcoholic solution in which a copper nitrate and a lanthanide metal nitrate are dissolved with an alcoholic solution of barium hydroxide to cause coprecipitation, and then thermally decomposing the resulting coprecipitate. The present invention relates to a method for producing a characteristic oxide superconductor raw material powder.

[Example] In the present invention, an alcohol solution (hereinafter referred to as solution (A)) in which a copper nitrate and a lanthanide metal nitrate are dissolved is used.
) is used.

The steel nitrate may be cuprous nitrate, cupric nitrate, or a cupric salt in which one of the anions forming the salt is a nitrate ion, as long as it is soluble in alcohol. In terms of stability, cost, etc., it is preferable to use cupric nitrate. These may be used alone or in combination.

It is preferable that the purity of the harmonic nitrate is high, and in particular, it is preferable to avoid contamination with impurity metals other than the amount of copper as much as possible, but it can be used as long as it has a purity of a normal reagent grade. If the salt contains impurities when dissolved in alcohol used as a solvent, it is preferable to use the solution after purification.

Specific examples of the lanthanide metals forming the lanthanide metal nitrates include yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. A nitrate of a lanthanide metal is a lanthanide metal salt in which three of the anions that form a salt with a lanthanide metal are nitrate ions, and a lanthanide metal salt in which one or two of the anions are nitrate ions. Among the salts, any salt that is soluble in alcohol can be used, but from the viewpoint of stability and cost, it is usually preferable to use lanthanide nitrate metal salts. These lanthanide metal nitrates may be used alone or in combination of two or more.

The copper nitrate and the lanthanide metal nitrate may be anhydrous nitrates, but trihydrate to hexahydrate containing water of crystallization are preferable because they have good solubility in alcohol.

Examples of the alcohol for dissolving the copper nitrate and the lanthanide metal nitrate include lower monohydric alcohols such as methyl alcohol, ethyl alcohol, l5o-propyl alcohol, and n-propyl alcohol, and ethylene glycol, diethylene glycol, propylene glycol, and glycerin. Lower polyhydric alcohols are preferred, and methyl alcohol and ethyl alcohol are particularly preferred because they increase the amount of nitrate of the metal dissolved, thereby increasing productivity during the coprecipitation reaction.

There is no particular limitation on the concentration of the alcohol solution (solution (A)) in which copper nitrate and lanthanide metal nitrate are dissolved, and the alcohol solution containing the lanthanide metal/copper atomic ratio is a predetermined ratio. Any concentration of solution can be used as long as it is formed, but from the viewpoint of productivity, yield ratio of coprecipitated components, etc., the concentration is usually 5 to 101hr/1.
00 g solvent, preferably 20-50 g/100
A solution of the order of g solvent is used.

In the present invention, in addition to the solution (A), an alcoholic solution of barium hydroxide (hereinafter also referred to as solution M (B)) is used.

Solution (B) may be prepared by dissolving commercially available barium hydroxide in alcohol, but since commercially available barium hydroxide often contains barium carbonate as an impurity, the solution (B) may be prepared by dissolving barium oxide in advance. An alcoholic solution of barium hydroxide without turbidity that can be obtained by adding high-purity barium oxide obtained by heat treatment or thermal decomposition of barium carbonate to alcohol, and then adding an equivalent amount of water to dissolve it. It is preferable to use Note that it is preferable to take care that this solution does not absorb carbon dioxide gas in the atmosphere.

As the alcohol for dissolving the barium hydroxide,
As in the case of copper nitrates and lanthanide metal nitrates, lower monohydric alcohols such as methyl alcohol, ethyl alcohol, 1so-propyl alcohol, n-propyl alcohol, and lower monohydric alcohols such as 1, ethylene glycol, diethylene glycol, propylene glycol, and glycerin are used. Polyhydric alcohols are preferred, and methyl alcohol is particularly preferred because it increases the solubility of barium hydroxide.

There is no particular limitation on the concentration of the alcohol solution of barium hydroxide, and any concentration of solution can be used as long as an alcohol solution is formed. However, from the viewpoint of improving productivity and coprecipitation efficiency, it is usually '/long solvent, preferably a solution of about 5 to 10 g/100 g solvent is used.

In the present invention, the solution (A) and solution (B) are mixed, and part of the copper nitrate and lanthanide metal nitrate in the solution (A) and barium hydroxide in the solution (B) are mixed. The reaction produces copper hydroxide, copper nitric acid hydroxide salt, lanthanide metal hydroxide, and barium nitrate, which are sparingly soluble to insoluble in alcohol, and the remaining copper nitrate and barium nitrate are produced. Nitrate of lanthanide metals is also added, forming a bluish scuttling mixture at the molecular level. This precipitate was filtered and dried under vacuum, with an average particle size of 0.0.
A fine coprecipitated powder of about 5 to Q, Js can be obtained.

As mentioned above, in addition to copper hydroxide, lanthanide metal hydroxide, and barium nitrate, alcohol-soluble nitrates and lanthanide metal nitrates are also co-precipitated by analysis of the sediment and analysis of the furnace fluid. Although this has been confirmed through analysis, the detailed reasons for this have not yet been fully elucidated.

There is no particular limitation on the method of mixing the solution (A) and solution (B), and they may be mixed by any method and under any conditions as long as the solution (A) and solution (B) are mixed quickly and homogeneously. .

In the coprecipitation reaction of the present invention, not all metal components are completely coprecipitated, and some metal components often remain as soluble components in the solvent. Therefore, depending on the metal components, solvent, and concentration used, measure the amount remaining in the coprecipitated component and the solvent in advance, and then adjust the amount added to achieve the desired metal ratio. It is preferable to distill off the solvent after the precipitation reaction.

The obtained coprecipitated powder is calcined in an oxidizing atmosphere at 700°C or higher, preferably 800°C or higher, more preferably 850°C or lower for 2 hours or more, preferably 10 hours or less, thereby changing the desired oxide superconductor raw material powder. It will be done. Furthermore, if the coprecipitate or coprecipitate powder is not brought into contact with carbon dioxide gas in the atmosphere during treatment and firing, barium carbonate will not be produced as an intermediate product, so the desirable effect of the present invention of being able to fire at low temperatures can be fully achieved. be done.

The oxide superconductor thick powder obtained in this way has a smaller particle size and has a larger surface energy than the raw material powder made by the conventional solid-phase method, and therefore has excellent sinterability. Since the stoichiometry of each material is uniform, when a sintered body is made using the raw material powder according to the present invention, the sintered density can be achieved at a firing temperature of 950°C or less without thermal decomposition of the target oxide. BaY2 with high grain boundary
The precipitation power of the second component such as Cuos or BaCuO2 ((l
You can get the highest quality sintered body. It is said that the sintered body C using the raw material powder according to the present invention has a smaller change over time than the sintered body of the conventional solid-phase method, is narrower at the superconducting transition temperature, and has a higher critical current density. This results in an oxide superconductor with excellent properties.

Hereinafter, the method of the present invention will be explained in detail based on Examples, but the present invention is not limited to the following Examples.

Example 1 15.3 g of barium oxide with a purity of 99.9% or more
was added to 200 g of methyl alcohol, and 3.6 g of pure water was gradually added while stirring with heating to prepare a methyl alcohol solution of barium hydroxide (hereinafter referred to as solution (A-1)).

Separately, add a solution (A-
1) Copper nitrate trihydrate 3 is added so that the number of copper atoms is 1.58 times the number of barium atoms in it, taking into account the uncoprecipitated content.
After adding and dissolving 19.3 g of yttrium nitrate hexahydrate with stirring so that the number of yttrium atoms is 0.504 times as much as 8.4 g, the solution prepared in advance (A
-1) was gradually added dropwise to form a bluish white coprecipitate. The obtained slurry was heated and stirred to allow 1/2 of the solvent to flow out, and then the solid material was purified under pressure, and the filtered solid was vacuum dried at about 50° C. and further lightly ground to obtain a coprecipitated powder.

This powder is soluble in water, and when the aqueous solution in which it was dissolved was measured for the metal composition ratio using ICP (plasma emission spectrometry), the atomic ratio of Y/Ba/Cu was 1.00/
The ratio was 1.99/3.01, indicating that a coprecipitate with the desired atomic ratio had been replaced.

Further, thermogravimetric analysis was performed on this powder, and it was found that while the coprecipitated powder obtained by the oxalic acid method was completely decomposed at about 830°C, this powder was completely decomposed at a low heating temperature of about 700°C.

Furthermore, this coprecipitated powder was calcined at 750°C for 3 hours in an atmosphere containing about 50% by volume of oxygen, and then slowly cooled to obtain a black calcined powder. Crystal structure analysis was conducted using Yt, o Ba2., which has the desired orthorhombic structure. OCu3. o It was consistent with the analysis pattern of the crystal structure of Oy.

Further, when the particle shape was observed using a scanning electron microscope, it was confirmed that aggregated particles having a tabular primary particle size of 0.4AII11 were formed.

[Effects of the Invention] Compared to the previously known synthesis methods using solid phase reaction methods and coprecipitation methods, the method of the present invention is characterized by: This is a coprecipitation reaction method from which there is no need to worry about moisture remaining in the powder ■The process is simple and the raw materials are relatively inexpensive ■Barium carbonate is not produced as a by-product during calcination, and the process can be performed at low temperatures and in a short time. The desired raw material powder is synthesized. The particle size is small and the raw material powder is uniform. The coprecipitate is completely inorganic,
It has excellent features such as no carbon remaining during calcination and the ability to add trace amounts of metal components.

Patent applicant Kanebuchi Chemical Industry Co., Ltd. Procedural amendment stamp button December 9, 1988 1 Display of the case 1988 Patent application No. 291173 2 Name of the invention Process for producing oxide superconductor raw material powder 3 Person making the amendment Relationship to the incident Patent applicant address: 3-2-4 Nakanoshima, Kita-ku, Osaka Name:
(094) Kanebuchi Chemical Industry Co., Ltd. Representative Masato Niino 4 Agent 540 Address 2-37 Tanimachi, Higashi-ku, Osaka NS Building” Subject of 5 amendments (1) Contents of 6 amendments to the specification (1) The specification The amendments will be made as shown in the attached "Amendment Specification".

7 List of Attached Documents (1) Amended Specification 1 Amended Specification 1 Title of Invention Process for producing oxide superconductor raw material powder 2 Claims 1 Alcohol solution and water in which jfi nitrate and lanthanide metal nitrate are dissolved A method for producing an oxide superconductor raw material powder, which comprises mixing barium oxide with an alcohol solution to cause coprecipitation, and then thermally decomposing the obtained coprecipitate.

3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a novel method for producing oxide superconductor raw material powder.

[Prior art/problems to be solved by the invention] It was discovered that a copper-barium-yttrium complex oxide having an oxygen-deficient perovskite structure is a superconductor that exhibits a superconducting transition temperature exceeding the temperature of liquid nitrogen. Since liquid nitrogen, which is inexpensive and has good cooling efficiency, can be used as a coolant, it is expected to be put to practical use in many applications such as semiconductor devices using superconductors, magnets, energy storage devices, magnetic shields, and sensors. Vigorous research is underway in all areas.

The copper-barium-yttrium composite oxide is a ceramic, and there is no precipitation of the second component at the grain boundaries of the sintered body, and the expected performance cannot be ensured unless the density of the sintered body is increased. In addition, for example, the atomic ratio of yttrium/barium/copper in this compound oxide is approximately 1/2/3,
Moreover, it is necessary to have an extremely limited composition/crystal structure in which the content ratio of oxygen to this ratio is 6.5 to 7.0 in atomic ratio and the crystal structure is orthorhombic. If the crystal structure deviates, the superconducting transition temperature, critical current value, and critical magnetic field, which are the performance characteristics of a superconductor, will decrease, so it is clear that sintering conditions and precise synthesis methods of raw material powder are important. It's coming. That is, it is desired that the raw material powder be homogeneous with a predetermined metal atomic ratio (hereinafter referred to as having excellent stoichiometry), and be fine with a uniform particle size.

In order to synthesize this raw material powder using the solid phase reaction method, which is currently known as the conventional method for synthesizing raw material powder for oxide superconductors, it is necessary to mix copper oxide, barium carbonate, and rare earth metal oxides. Afterwards, unless repeated calcination and pulverization several times at a high temperature of around 950°C for a long period of time, it is not possible to change the raw material powder to a single phase as seen by X-rays, grain growth occurs and the grain size increases to several tens of squares. There is a problem in that the resulting powder has poor sinterability.

Therefore, compared to the above-mentioned solid phase reaction method, processes are being considered that have better stoichiometry, have finer and more uniform particles, and can change the desired oxide by firing at a lower temperature and in a shorter time. The oxalate coprecipitation method, carbonate coprecipitation method, gel decomposition method, etc. have been proposed.

However, in addition to the problem that these methods use water, which oxide superconductors dislike, there are still problems that need to be solved as described below.

That is, the oxalate coprecipitation method is a method in which a coprecipitate is obtained by dropping an aqueous solution of oxalic acid or an oxalate compound into a mixed aqueous solution or an ethyl alcohol-water mixed solution of steel nitrate, barium nitrate, and rare earth metal nitrate. , delicate pII control is required to maintain good stoichiometry and is very difficult to implement.

In addition, the carbonate coprecipitation method is a method in which an alkali metal carbonate such as potassium carbonate is added to a mixed aqueous solution of copper nitrate, barium nitrate, and rare earth metal nitrate to neutralize and coprecipitate. Careful cleaning is required to remove alkali metal components remaining in the target compound, and even if thorough cleaning is performed, there is a risk that alkali metal may remain in the target compound.

Furthermore, the gel decomposition method is a method in which citric acid and ethylene glycol are added to a mixed aqueous solution of nitrates of various metals and heated to create a gel-like substance, which is then thermally decomposed. In some cases, carbon remains even after the firing process.

Moreover, in all three methods, the target product cannot be obtained directly through the calcination process, but instead is produced through a mixture of barium carbonate, copper oxide, and rare earth metal oxide as an intermediate, similar to the solid-phase reaction method. It is known that barium carbonate, which is relatively stable against heat, inevitably causes the firing temperature to be high, and that it occurs when a large amount of raw material is fired at once or in a deep-bottomed container. There is a problem in that it is difficult to achieve a single exchange due to the rate-limiting diffusion of carbon dioxide gas.

[Means for Solving the Problems] The present inventors have conducted intensive studies on methods for solving these problems, especially methods for synthesizing oxide superconductor raw material powder that does not produce barium carbonate as an intermediate product. In addition, barium hydroxide is soluble in lower alcohols such as methyl alcohol, and barium hydroxide reacts with nitrates of steel and rare earth metals that are soluble in lower alcohols, making it difficult for organic solvents such as lower alcohols to react with barium hydroxide. Focusing on making soluble barium nitrate, it was mixed with a copper compound,
The inventors have discovered that it is possible to co-precipitate barium compounds and rare earth metal compounds, and have arrived at the present invention.

That is, the present invention involves mixing an alcoholic solution in which a copper nitrate and a lanthanide metal nitrate are dissolved with an alcoholic solution of barium hydroxide to cause coprecipitation, and then thermally decomposing the resulting coprecipitate. The present invention relates to a method for producing a characteristic oxide superconductor raw material powder.

[Example] In the present invention, an alcohol solution (hereinafter referred to as solution (A)) in which a copper nitrate and a lanthanide metal nitrate are dissolved is used.
) is used.

The steel nitrates are cuprous nitrate and cupric nitrate. One of the anions that form the salt is a nitrate ion, and the other is an ion such as a halogen atom such as bromine or chlorine or a hydrogen group. Among the tAZ copper salts, any alcohol-soluble salt can be used, but it is preferable to use cupric nitrate in terms of stability and cost. These may be used alone or in combination.

It is preferable that the purity of the wave-toned nitrate is high (for example, about 98% by weight or more), and in particular, it is preferable to avoid contamination with impurity metals other than copper as much as possible. above), it can be used. If the salt contains impurities when dissolved in alcohol used as a solvent, it is preferable to filter the solution before use.

Specific examples of the lanthanide metals forming the lanthanide metal nitrates include yttrium, lanthanum, neodymium, promethium, samarium, europium, gadolinium, dysprosium, holmium, erbium,
Nitrates of lanthanide metals include thulium, ytterbium, and lutetium, and nitrates of lanthanide metals include lanthanide metal salts in which three of the anions that form the salt with the lanthanide metal are nitrate ions, and lanthanide metal salts in which one or two of the anions are nitrate ions. Among the lanthanide metal salts in which the other anions are ions such as halogen atoms such as bromine and chlorine or hydroxyl groups, it can be used as long as it is soluble in alcohol.
In view of stability, cost, etc., it is usually preferable to use lanthanide nitrate metal salts. These lanthanide metal nitrates may be used alone or in combination of two or more.

The steel nitrate and the lanthanide metal nitrate may be anhydrous nitrates, but trihydrate to hexahydrate containing water of crystallization are preferable because they have good solubility in alcohol.

Examples of the alcohol for dissolving the steel nitrate and the lanthanide metal nitrate include monohydric alcohols having 1 to 5 carbon atoms such as methyl alcohol, ethyl alcohol, l5o-propyl alcohol, and n-propyl alcohol;
Polyhydric alcohols having 2 to 8 carbon atoms, such as ethylene glycol, diethylene glycol, brobylene glycol, and glycerin, are preferred; in particular, when methyl alcohol or ethyl alcohol is used, the amount of nitrate of the metal dissolved increases, so it is difficult to use during the coprecipitation reaction. This is preferable because it increases productivity.

There is no particular limitation on the concentration of the alcohol solution (solution (A)) in which copper nitrate and lanthanide metal nitrate are dissolved, and the alcohol solution containing the lanthanide metal/copper atomic ratio is a predetermined ratio. Any concentration of solution can be used as long as it is formed, but from the viewpoint of productivity and improvement of the yield of coprecipitated components, it is usually 5 to IOD/LOG g.
A solution of about 20-50 g/100 g solvent is used, preferably about 20-50 g/100 g solvent.

In the present invention, in addition to the solution (A), an alcoholic solution of barium hydroxide (hereinafter also referred to as solution (B)) is used.

Solution (B) may be prepared by dissolving commercially available barium hydroxide in alcohol, but since commercially available barium hydroxide often contains barium carbonate as an impurity, the solution (B) may be prepared by dissolving barium oxide in advance. A clear alcohol solution of barium hydroxide obtained by adding high purity barium oxide obtained by heat treatment or thermal decomposition of barium carbonate to alcohol, then adding an equivalent amount of water to dissolve it, and in some cases filtering. It is preferable to use Note that it is preferable to take care that this solution does not absorb carbon dioxide gas in the atmosphere.

As the alcohol for dissolving the barium hydroxide,
As in the case of copper nitrates and lanthanide metal nitrates, monohydric alcohols having 1 to 5 carbon atoms such as methyl alcohol, ethyl alcohol, l5o-propyl alcohol, and rhopropyl alcohol, ethylene glycol, diethylene glycol, propylene glycol, and glycerin. Polyhydric alcohols having 2 to 8 carbon atoms are preferred, and methyl alcohol is particularly preferred because it increases the solubility of barium hydroxide.

There is no particular limit to the concentration of the alcoholic solution of barium hydroxide, and any concentration of solution can be used as long as an alcoholic solution is formed. From the point of view, usually 1 to 15
g/long solvent level, preferably 5-10g/
100 t: A solution equivalent to a solvent is used.

In the present invention, the solution (A) and the solution (13) are mixed, and part of the copper nitrate and the lanthanide metal nitrate in the solution (A) and the barium hydroxide in the solution (B) are mixed. The reaction produces copper hydroxide, copper nitric acid hydroxide salt, and lanthanide metal hydroxide barium nitrate, which are sparingly soluble to insoluble in alcohol, and the remaining copper nitrate and barium nitrate are formed. Nitrate of lanthanide metals is also added, forming a bluish scuttling mixture at the molecular level. This precipitate was filtered and dried under vacuum, with an average particle size of 0.
A fine coprecipitated powder of about 0.05 to 0.5 liters can be obtained.

As mentioned above, in addition to steel hydroxides, lanthanide metal hydroxides, and barium nitrate, alcohol-soluble nitrates and lanthanide metal nitrates also co-precipitate due to sediment analysis and furnace fluid analysis. Although this has been confirmed through analysis, the detailed reasons for this have not yet been fully elucidated.

Regarding the method of mixing the solution (A) and solution (B), etc.
There is no limitation to this, and as long as solution (A) and solution (B) are mixed quickly and homogeneously, they may be mixed by any method and under any conditions.

In the coprecipitation reaction of the present invention, not all metal components are completely coprecipitated, and some metal components often remain as soluble components in the solvent. Therefore, depending on the metal components, solvent, and concentration used, measure the amount remaining in the coprecipitated component and the solvent in advance, and then adjust the amount added to achieve the desired metal ratio. It is preferable to distill off the solvent after the precipitation reaction.

The obtained coprecipitated powder is heated at 700°C or higher, preferably 800°C or higher, and more preferably 850°C or lower in an oxidizing atmosphere.
The target oxide superconductor raw material powder can be changed by firing for more than an hour, preferably less than 10 hours. Furthermore, if the coprecipitate or coprecipitate powder is not brought into contact with carbon dioxide gas in the atmosphere during treatment and firing, barium carbonate will not be produced as an intermediate product, so the desirable effect of the present invention of being able to fire at low temperatures can be fully achieved. be done.

The oxide superconductor thick powder obtained in this way requires lower firing temperature than raw material powder made by conventional solid phase method because it does not produce thermally stable barium carbonate as a by-product. Since the particle size is small, the surface energy is large, and therefore the sinterability is high, and the stoichiometry of each particle is uniform, so when a sintered body is made using the raw material powder according to the present invention, A high-quality sintered body with high sintered density and almost no precipitation of second components such as l3aY2Cuos and 1'3acu02 at grain boundaries can be obtained at a firing temperature of 950°C or lower without thermal decomposition of the target oxide. . Therefore, the sintered body using the raw material powder according to the present invention has excellent properties such as a smaller change over time than the conventional solid-phase sintered body, a narrow superconducting transition temperature, and a high critical current density. It becomes an oxide superconductor with

Hereinafter, the method of the present invention will be explained in more detail based on Examples, but the present invention is not limited to the following Examples.

Example 1 Barium oxide having a purity of 99.9% by weight or more 15.
3 g of barium hydroxide was added to 200 g of methyl alcohol, and 3.6 g of pure water was gradually added while stirring with heating to prepare a methyl alcohol solution of barium hydroxide (hereinafter referred to as solution (A-1)).

Separately, add a solution (A-
1) Copper nitrate trihydrate 3 is added so that the number of copper atoms is 1.58 times the number of barium atoms in it, taking into account the uncoprecipitated content.
After adding and dissolving 32.8 g of yttrium nitrate hexahydrate with stirring so that the number of yttrium atoms is 0.86 times as much as 8.4 g, the solution prepared in advance (A-
When 1) was gradually added dropwise, a bluish white coprecipitate was formed. The resulting slurry was heated and stirred to allow 1/2 of the solvent to flow out, and then clarified under pressure, and the purified solid was vacuum dried at about 50° C. and further lightly pulverized to obtain a coprecipitated powder.

This powder is soluble in an acidic aqueous solution, and when the aqueous solution in which it was dissolved was measured for the metal composition ratio using ICP (plasma emission spectrometry), the atomic ratio of Y/Ba/Cu was 1.
．． 00/, 2.07/3.01, and it was found that the coprecipitate with the desired atomic ratio had been changed.

Separately, prepare an approximately 30% aqueous solution of yttrium nitrate hexahydrate, barium nitrate, and copper nitrate trihydrate in a molar ratio of Y:Ba+Cu-1:2:3.
350g of ethyl alcohol containing about 20wt% of oxalic acid
The resulting coprecipitate was filtered and dried to obtain a coprecipitated powder by the oxalic acid method.

Thermogravimetric analysis of these powders revealed that the coprecipitated powder produced by the oxalic acid method completely decomposed at about 830°C, whereas the powder produced by the method of the present invention completely decomposed at a heating temperature as low as about 700°C. did.

Further, the coprecipitated powder according to the method of the present invention can be prepared by adding about 50% oxygen to the coprecipitated powder.
After firing at 750°C for 3 hours in an atmosphere containing %% by volume and cooling slowly to obtain a black calcined powder, crystal structure analysis was performed using the X-ray diffraction method using the obtained powder. Yl, o Ba2. having a square structure. OCu3
．． The pattern was consistent with the analysis pattern of the crystal structure of 00y (Y is 6.7 to 6.9).

Furthermore, when the particle shape was observed using a scanning electron microscope, it was confirmed that aggregated particles having a primary particle size of 0.4ρ were formed.

Example 2 Norium oxide 15 with a purity of 99.9% by weight or more
．． Add 3 g to 200 g of methyl alcohol, and gradually add 3.6 g of pure water while stirring with heating to make a methyl alcohol solution of barium hydroxide (hereinafter referred to as solution (A-1)).
was prepared.

Separately, add a solution (A-
1) Copper nitrate trihydrate 3 is added so that the number of copper atoms is 1.58 times the number of barium atoms in it, taking into account the uncoprecipitated content.
After adding and dissolving 19.3 g of yttrium nitrate hexahydrate with stirring so that the number of yttrium atoms is 0.504 times as much as 8.4 g, the solution prepared in advance (A
-1) was gradually added dropwise to form a bluish white coprecipitate. The obtained slurry was heated and stirred to allow 1/2 of the solvent to flow out, and then filtered under pressure, and the filtered solid was vacuum dried at about 50° C. and further lightly ground to obtain a coprecipitated powder.

This powder is soluble in an acidic aqueous solution, and when the aqueous solution in which it was dissolved was measured for the metal composition ratio using ICP (plasma emission spectrometry), the atomic ratio of Y/Ba/Cu was 1.
．． 00/1.99/3. It was found that it was OL, and a coprecipitate with the desired atomic ratio had been replaced.

When thermogravimetric analysis was performed on this powder, it was completely decomposed at a heating temperature as low as about 700°C.

Furthermore, this coprecipitated powder was calcined at 750°C for 3 hours in an atmosphere containing about 50% by volume of oxygen, and then slowly cooled to obtain a black calcined powder. Crystal structure analysis revealed that Yl, o Ba2. o Cuco ONY is 1
3.7 to 8.9) were consistent with the analysis pattern of the crystal structure.

Further, when the particle shape was observed using a scanning electron microscope, it was confirmed that aggregated particles having a primary particle size of 0.41 tm were formed.

[Effects of the Invention] Compared to the previously known synthesis methods using solid phase reaction methods and coprecipitation methods, the method of the present invention is characterized by: This is a coprecipitation reaction method from which there is no need to worry about water remaining in the powder ■ The process is simple and the raw materials are relatively inexpensive ■ No barium carbonate is produced as a by-product during calcination, and it can be fired at low temperatures and in a short time The desired raw material powder is synthesized with the process. - The raw material powder is changed to a uniform material with a small particle size. - The coprecipitate is completely inorganic,
It has excellent features such as no carbon remaining during calcination and the ability to add trace amounts of metal components.

Patent applicant Kanebuchi Chemical Industry Co., Ltd. −Mountain

Claims (1)

[Claims] 1 Oxidation characterized by mixing an alcoholic solution in which copper nitrate and lanthanide metal nitrate are dissolved with an alcoholic solution of barium hydroxide to cause coprecipitation, and then thermally decomposing the resulting coprecipitate. Manufacturing method for material superconductor powder.