JPH01252528A - Production of raw material powder of oxide superconductor - Google Patents

Abstract

PURPOSE:To enable the lowering of the synthesis temperature and the formation of single phase, by mixing an alcohol solution of nitrates of copper and a lanthanide metal with an alcohol solution of Ba(OH)2 and a Ba alkoxide, thereby forming a coprecipitate and directly producing the objective material. CONSTITUTION:A coprecipitate is formed by mixing an alcohol solution I of a copper nitrate and a lanthanide metal nitrate with an alcohol solution II of one or more compounds selected from Ba(OH)2 and Ba alkoxide. The objective raw material powder of oxide superconductor can be produced by the thermal decomposition of the coprecipitate. The raw material powder of oxide superconductor is obtained without forming barium carbonate, etc., as an intermediate product by this process. Accordingly, the objective compound can be produced in a short time at a low temperature. Since the process is a coprecipitation reaction from an organic solvent without using an aqueous solution which is unsuitable for the production of oxide superconductor, the trouble of the residual water in the power can be lessened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a novel method for producing oxide superconductor raw material powder. More specifically, the present invention relates to a method for producing a copper-barium-lanthanide composite oxide superconductor raw material powder that does not produce barium carbonate as an intermediate product.

[Prior art/issues to be solved by the invention] It was discovered that a copper-barium-yttrium complex oxide with an oxygen-deficient perovskite structure is a superconductor that exhibits a superconducting transition temperature exceeding the temperature of liquid nitrogen. Since then, liquid nitrogen, which is inexpensive and has good cooling efficiency, can be used as a coolant.
It is expected that they will be put to practical use in many applications such as semiconductor devices using superconductors, superconducting magnets, energy storage devices, magnetic shields, and sensors, and vigorous research is being carried out in various fields.

The copper-barium-lanthanide rare earth metal complex oxide is a type of ceramic material, and when a polycrystalline sintered body is used as a superconducting material, it has the same problem as ordinary ceramics. be.

In other words, the second component, which becomes an impurity, should not be precipitated at the grain boundaries of the superconducting oxide sintered body, the density of the sintered body should be as close to the true density as possible, and the grain size of the constituent particles should be kept as close as possible to the true density. It is extremely important that the diameter be uniform and fine to ensure performance as a superconductor.

In addition, the composite oxide cannot exhibit its expected performance as a superconductor unless the density of the sintered body is increased;
Furthermore, this composite oxide has a very limited composition and crystal structure, for example, the elemental ratio of yttrium/barium/copper is approximately 1/2/3, and the atomic ratio of oxygen to this ratio is 6. 7 to 7.0, and the crystal structure must be orthorhombic. If this composition/crystal structure deviates, the superconducting transition temperature, critical current value, and critical magnetic field, which are the performance of the superconductor, will be affected. It has become clear that the sintering conditions and precise synthesis method of the raw material powder are important because of this. That is, as a raw material powder, a fine raw material powder with a predetermined metal ratio, homogeneity (hereinafter referred to as having excellent stoichiometry), and uniform particle size is desired.

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 common copper oxide, barium carbonate, and rare earth metal oxides. Afterwards, unless calcining and pulverization are repeated several times at high temperatures of around 950°C and over a long period of time, it is not possible to change the raw material powder to a single phase in X-rays, and grain growth occurs, increasing the grain size to several tens of pieces. However, 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 processes 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 oxalic acid or an aqueous solution of an oxalate compound into a mixed aqueous solution or an ethyl alcohol-water mixed system of copper nitrate, barium nitrate, and rare earth metal nitrate, In order to maintain excellent stoichiometry, delicate control of PLL is required, making the reaction operation very difficult in practice, and additional additives are required for pH adjustment.

In addition, the carbonate coprecipitation method is a method in which a mixed aqueous solution of copper nitrate, barium nitrate, and rare earth metal nitrate is neutralized with an alkali metal carbonate such as potassium carbonate and co-precipitated. Careful cleaning is required to remove residual alkali metal components, and even then, there is a risk that alkali metals may remain in the target compound.

Furthermore, the gel decomposition method is a method in which citric acid and ethylene glycol are added to an aqueous solution containing nitrates of various metals and heated to create a gel-like substance, which is then thermally decomposed. With this method, carbon may remain even after the firing process.

Moreover, in all of these three methods, the target product cannot be obtained directly through baking acid treatment, but the target product 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. However, due to the existence of barium carbonate, which is relatively stable against heat, the synthesis temperature inevitably becomes high, and if a large amount of raw materials are fired at one time or in a deep-bottomed container, There is a problem in that it is difficult to obtain a single phase due to the rate-limiting diffusion of carbon dioxide gas that is generated.

The purpose of the present invention is to solve the problems of these conventional techniques,
In particular, it is an object of the present invention to provide a method for synthesizing raw material powder for oxide superconductors that does not produce barium carbonate as an intermediate product.

[Means for Solving the Problems] The present inventors have discovered that when an alcohol solution of barium hydroxide and/or barium alkoxide that is soluble in alcohol is mixed with an alcohol solution of copper nitrate and rare earth metal nitrate, They discovered that barium nitrate reacts to produce barium nitrate that is insoluble in organic solvents and causes coprecipitation, and they also found the optimal coprecipitation conditions and arrived at the present invention.

That is, the present invention mixes an alcoholic solution (I) of a copper nitrate and a lanthanide metal nitrate with an alcoholic solution (I) of at least one compound selected from the group consisting of barium hydroxide and barium alkoxide. The present invention relates to a method for producing an oxide superconductor raw material powder, which is characterized in that a coprecipitate is formed by oxidation, and the resulting coprecipitate is thermally decomposed.

[Example] In the present invention, an alcohol solution (hereinafter referred to as solution (■
) is used.

The above-mentioned copper nitrates include cuprous nitrate, cupric nitrate, and cupric salts in which one of the anions forming the salt is a nitrate ion and the other is an ion of a halogen atom such as bromine or chlorine or a hydroxyl group. Any alcohol-soluble salt can be used in the present invention, but from the viewpoint of operability, stability, cost, etc., it is usually preferable to use cupric nitrate. Further, these may be used alone or in combination.

The purity of the copper nitrate is higher (e.g., about 98% by weight)
The above) is preferred, and it is particularly preferable to avoid contamination with impurity metals other than copper as much as possible, but it can be used satisfactorily as long as the purity is at the level of ordinary reagent grade (ie, about 95% by weight or more). Note that if insoluble impurities are contained after dissolving copper nitrate 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. ion, and the other anions are halogen atoms such as bromine and chlorine, and ions such as hydroxyl groups. This refers to alcohol-soluble salts of lanthanide metal salts, which may be used alone or in combination. Good too. Among these, it is preferable to use a lanthanide metal salt in which all three of the anions are nitrate ions from the viewpoint of operability, stability, cost, etc.

The above-mentioned copper nitrate and lanthanide metal nitrate may be anhydrous nitrates, but if a trihydrate to hexahydrate copper nitrate or lanthanide metal nitrate containing water of crystallization is used, it has good solubility in alcohol and is easy to handle. That's preferable.

As the alcohol serving as the solvent for dissolving the copper nitrate and the lanthanide metal nitrate, any alcohol that can dissolve them can be used. Among them, methyl alcohol, ethyl alcohol, 1so-
Monohydric alcohols having 1 to 5 carbon atoms, such as propyl alcohol and n-propyl alcohol, and polyhydric alcohols having 2 to B carbon atoms, such as ethylene glycol, diethylene glycol, propylene glycol, and glycerin, are preferred, and methyl alcohol and ethyl alcohol are particularly preferred. This is preferable because the amount of metal nitrate dissolved increases and the productivity during the coprecipitation reaction increases.

In addition, organic solvents other than the above-mentioned alcohols, such as aromatic solvents such as benzene and toluene, acetate esters, ethers, ketones, etc., are usually used as a solvent for solution (I), as long as they do not reduce the original function of dissolving metal nitrates. At most 50% by weight may be used.

There is no particular limitation on the concentration of the alcohol solution (solution m) in which copper nitrate and lanthanide metal nitrate are dissolved, and an alcohol solution containing the lanthanide metal/copper atomic ratio at a predetermined ratio is formed. Any concentration of solution can be used as long as it is possible, but from the viewpoint of cost, productivity, filtration efficiency of coprecipitated components, etc., the concentration is usually 5 to 100 r/10.
0 tr solvent level, preferably 20-50g/100s
A solution of the order of r solvent is used.

In the present invention, in addition to the solvent (I), an alcoholic solution of barium hydroxide and/or barium alkoxide (hereinafter also referred to as solution (I[)) is used.

Solution (I) 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 (I) may be prepared by dissolving barium oxide in advance. Add high purity barium oxide obtained by heat treatment or thermal decomposition of barium carbonate to alcohol, then add an equivalent amount of water to dissolve it, and preferably filter it to obtain a clear alcoholic solution of barium hydroxide. 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.

Examples of the barium alkoxide include compounds represented by the general formula: % (in the formula, R represents an alcohol residue). Specific examples of R include, for example, alcohol residues having 1 to 20 carbon atoms, preferably 1 to 20 carbon atoms;
Examples of alcohol residues include alcohol residues having 1 to 20 carbon atoms, preferably 1 carbon number, such as methyl alcohol, ethyl alcohol, propyl alcohol, and butyl alcohol.
-4 monohydric alkyl alcohols, for example, polyhydric alcohols having 2 to 20 carbon atoms, preferably 2 to 8 carbon atoms, such as ethylene glycol and ethylene glycol monoalkyl ether such as ethylene glycol monoethyl ether; Specific examples of barium dialkoxide include barium alkoxide, barium jetoxide, barium di-15o-propoxide, barium di-n-propoxide, barium di-n-butoxide, barium di-t-butoxide, and the like.

Although there are no particular limitations on the method for preparing the alcohol solution of barium alkoxide, it can be easily prepared by reacting commercially available metallic barium with a predetermined alcohol. If the purity of metallic barium is low or if insoluble components are observed, the obtained alcoholic solution of barium alkoxide can be further filtered to obtain a clear alcoholic solution of barium alkoxide.

There is no particular limitation on the concentration of the alcoholic solution (I) of barium hydroxide and/or barium alkoxide,
Any concentration of solution can be used as long as an alcohol solution is formed, but from the viewpoint of productivity, coprecipitation efficiency, filtration efficiency during coprecipitation reaction, etc., the concentration is usually about 1 to 50 g/100 g of solvent, preferably about 5 to 50 g. A solution of around 25g/100g solvent is used.

Note that this solution is also preferably prevented from coming into contact with carbon dioxide gas in the atmosphere in order to prevent precipitation of barium carbonate.

It is preferable to further dissolve ammonia and/or an organic amine in the solution (I) because all metal components are efficiently precipitated during the coprecipitation reaction. Although the reason for this is not clear, it is thought to be as follows.

In the coprecipitation reaction in the present invention, the alcohol solution (I)
This reaction occurs by mixing copper nitrate and lanthanide metal nitrates in solution (I) with barium compounds in solution (II) as shown in the following formula, and all This is caused by the metal component precipitating as a compound insoluble in the solvent.

(Y(NO3)3 φxt120 +3CU(NO3)
2 ・yl120 ) + 2Ba (Oll) 2 Alcohol solution (I) Alcohol solution (I) = 2Cu (
OH)2 or Cu(011)・CNOs)+
Y(011)3 +28a(NO3)2 (In this formula, an example is shown in which yttrium is used as the lanthanide metal and barium hydroxide is used as the barium compound.

(However, x and y are each 3 to 6.) However, if the amount of nitrate radicals relative to barium is large, the metal components will not completely co-precipitate, and some will remain in the organic solvent as nitrate metal salts. Sometimes. However, if ammonia and/or an organic amine are added in advance to the alcohol solution (I), the following reaction occurs and the metal components are efficiently precipitated as insoluble compounds.

(Y(NO3)3 ・X1120+3CU(NO3)2
・yl120) + Alcohol solution (I) (2Ba(OH)2+ Rs N) Alcohol solution (I) 1 = 2Cu(OH)2 or Cu(OH) (NO
3) +Y(OH)3+28a(NOx)2+R
3N11NO3 (organic solvent soluble) (In this formula, an example is shown in which yttrium is used as the rank nide metal, barium hydroxide is used as the barium compound, and an organic amine. However, x and y are each from 3 to 6.) The ammonia is It is preferable to use ammonia gas by injecting it into the alcohol solution (I) or by dissolving the ammonia gas in an organic solvent in advance, but it is also possible to use ammonia water with a high concentration of 25 to 30% by weight. It is possible.

Further, as specific examples of the organic amine, for example, carbon atoms having 3 to 8 carbon atoms such as isopropylamine, butylamine, etc.
secondary alkylamines having 4 to 1B carbon atoms such as diethylamine, diisobutylamine, and diisopropylamine; tertiary alkylamines having 3 to 24 carbon atoms such as trimethylamine, triethylamine, tripropylamine, and tributylamine; and monomethanolamine. , primary alkanolamines having 1 to 8 carbon atoms, such as monoethanolamine, motuprobanolamine, and monobutanolamine; 3-3 carbon atoms such as secondary alkanolamine, trimethanolamine, triethanolamine, tripropaturamine, tributanolamine, etc.
Basic organic amine compounds that are soluble in organic solvents and do not contain metal components such as alkali metals that may become impurities in the coprecipitate, such as alkanolamines, but are not limited to these. If so, it can be used in the present invention. Among these, ammonia, butylamine, diisobutylamine, diisopropylamine, triethylamine, tripropylamine, and tributylamine are preferably used because they quickly react with nitrate groups and are relatively difficult to form complexes with steel ions. These organic amines may be used alone or in combination of two or more.

The amount of ammonia and/or organic amine to be added is preferably adjusted appropriately depending on the type of metal used, the combination of solvents, etc., but is usually 0.05 to 10 mol per mol of barium atom, preferably 0.05 to 10 mol, preferably 0. If .2 to 4 mol is added, a coprecipitate with the desired metal ratio can be easily obtained.

When adding ammonia and/or an organic amine to solution (II), either prepare an alcoholic solution in which ammonia and/or an organic amine are dissolved, and then dissolve barium alkoxide or its solution therein, or add barium alkoxide or a solution thereof in advance. After preparing an alcohol solution, ammonia and/or an organic amine may be dissolved therein.

As the solvent used for preparing the solution (II), the solution (
The same solvent as used in I) may be used, but in order to prevent the generated ammonium nitrate salt and organic amine nitrate salt from being mixed into the coprecipitate, a solvent that easily dissolves these salts in the solvent may be used as appropriate. It is preferable to use it selectively. In particular, the use of methyl alcohol increases the solubility of barium hydroxide, and is therefore preferred when water-solubilized barium is used.

In the present invention, when ammonia and/or organic amine are added to solution (I), solution m and solution (II
), substantially all the metal components can be mixed as a coprecipitate without leaving any metal components in the solution.

The ratio of solution (I) and solution (I) to be used is determined depending on the composition of the desired object. Also, solution (I) and solution (
There is no particular limitation on the method of mixing with the solution (II).
I) and solution (I) may be mixed by any method and under any conditions as long as they are mixed quickly and homogeneously.

The reaction is carried out, for example, by stirring the solution (I) while stirring the solution (I[
By gradually dropping 1, copper nitrate and lanthanide metal nitrate in solution (I) react with barium hydroxide and/or barium alkoxide, ammonia, and/or organic amine to form alcohol. Slightly soluble to insoluble copper hydroxides, nitric acid/hydroxide complex salts of copper, hydroxides of lanthanide metals, barium nitrate, or complex metal salts between copper, barium, and ythtrium are produced, and A mixed bluish scuttling is produced. This precipitate is filtered, preferably at 50-100°C.
When dried under vacuum, a fine coprecipitated powder with an average particle diameter of about 0.05 to 0.5° is obtained.

Although the mechanism of the coprecipitation reaction has been partially confirmed through analysis of filtrate and coprecipitate, it has not yet been fully elucidated.

The obtained coprecipitated powder is heated at 700°C or higher in an oxidizing atmosphere for 2 to 1
The desired oxide superconductor raw material powder can be changed by firing and thermally decomposing it for 20 hours, preferably at 750-900°C for 2-60 hours, more preferably at 800-850°C for 4-12 hours. Note that if the precipitate during the coprecipitation reaction and the coprecipitated powder are not brought into contact with carbon dioxide gas in the atmosphere during treatment and firing, the production of barium carbonate will be inhibited, and the favorable effects of the present invention (for example, the ability to perform firing even at low temperatures) will be prevented. ) can be fully demonstrated.

Furthermore, even if this coprecipitated powder is fired under the same temperature conditions as described above in an inert gas such as nitrogen or argon gas or under reduced pressure, it can be used as a raw material powder that does not produce carbon as a by-product.

The powder obtained by firing in this inert atmosphere is a compound that does not have superconductivity (its crystal structure is tetragonal), but the powder has shape anisotropy such as a plate shape. By molding this powder and sintering it in an oxidizing atmosphere, it becomes an anisotropic polycrystalline body, and the critical magnetic field and critical current values in a specific direction are higher than that of ordinary sintered bodies. You can expect a much larger effect.

The oxide superconductor raw material powder obtained in this way does not produce thermally stable barium carbonate as a by-product during thermal decomposition, compared to raw material powder made by the conventional solid phase method. The desired oxide superconducting composition can be produced at a lower temperature, fine particles with a secondary particle size of 1 μm or less can be easily produced, the surface energy is large, the sinterability is excellent, and the stoichiometry of each particle is Are better.

Therefore, if a sintered body is made using this raw material powder, the secondary particle size will be small and the sintered density will be high at a lower sintering temperature of 950°C or less without thermal decomposition of the target superconducting oxide. high, and BaY2Cu05 and BaCuO at the grain boundaries.
A high-quality sintered body with almost no precipitation of second components such as 2 can be obtained.

Therefore, the sintered body using the raw material powder according to the present invention is
The result is an oxide superconductor with a smaller change over time, a narrower superconducting transition temperature, and a higher critical current density than sintered bodies produced using the conventional solid-phase method.

Hereinafter, the manufacturing 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 with 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 while 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 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 metal composition ratio was determined to be 71-1 in an aqueous solution of 10P (plasma emission spectrometry), the atomic ratio of Y/Ba/Cu was 1.
．． 00/2.07/3.01, and it was found that a coprecipitate with the desired atomic ratio had been changed.

Separately, an approximately 30% aqueous solution containing yttrium nitrate hexahydrate, barium nitrate, and copper nitrate trihydrate in a molar ratio of Y:Ba:Cu-1:223 was prepared.
g was dropped into 350 g of ethyl alcohol containing about 20 ffI% of oxalic acid, and the resulting coprecipitate was filtered and dried to obtain a coprecipitated powder by the oxalic acid method.

Furthermore, 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 decomposed at about 700°C.
Completely decomposed at heating temperatures as low as ℃.

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 with a square structure, o Ba2. oCLI3
40y<Y was consistent with the analysis pattern of the crystal structure (6.7 to 6.9).

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

Example 2 Metallic barium 16. with a purity of 99.9% by weight or more.
8 g of barium jetoxide was added little by little to 250 g of ethyl alcohol with stirring to make an ethyl alcohol solution of barium jetoxide. To this was added 12.25 g of triethylamine, which is equimolar to barium, and stirred to form a homogeneous solution (solution (
A-2)) was obtained.

Separately, in 100 g of ethyl alcohol, 43.5 g of copper nitrate trihydrate and 0.5 g of yttrium were added so that the number of copper atoms was 1.5 times the number of barium atoms. Yttrium nitrate hexahydrate 23
．． 1 g was added with stirring and uniformly dissolved. Thereafter, solution (A-2) was gradually dropped into this solution while stirring vigorously, and a bluish-white coprecipitate was generated. After filtering this slurry under pressure with nitrogen gas, the solid content was reduced to approximately 60°C.
The mixture was dried under vacuum and lightly ground to obtain a coprecipitated powder. In addition,
The filtrate obtained during filtration was transparent, and no precipitate was formed even when oxalic acid was added to it, confirming that the metal components were completely coprecipitated.

This powder is soluble in an acidic aqueous solution, and when the metal composition ratio of the aqueous solution in which it was dissolved was measured by the IcP method (plasma emission spectrometry), the Y/Ba/Cu was 1.00/
1.99/3.01, and it was found that the coprecipitate of the desired metal composition had been replaced.

In addition, when thermogravimetric analysis was performed on this powder, approximately 70%
Complete decomposition occurred at heating temperatures as low as 0°C.

Further, this coprecipitated powder was fired in the air at 750°C for 6 hours and then slowly cooled to obtain a black calcined powder. When the crystal structure of this powder was measured by X-ray diffraction, it was found that Y+, o Ba2. OCu3.0 O
NY was consistent with the crystal pattern of 6.7-6.9). When the particle shape was observed using a scanning electron microscope, the -order particle size was approximately 0.4. It was confirmed that uniform particles with a diameter of cm were produced.

Furthermore, approximately 3% by weight of polyethylene wax is added to this calcined powder and coated uniformly to produce approximately 1 ton/cd.
After press molding at a pressure of
After firing at 00° C. for 8 hours, the sintered body was slowly cooled and the density of the obtained sintered body was measured and found to be about 5-83 g/cj. This corresponded to about 91% of the logic density. When the raw material powder obtained by normal solid phase reaction was sintered under similar sintering conditions, the density was 4.0 Ofr/aJ (approximately 62% of the theoretical density), so the raw material powder according to the present invention It was found that the sinterability was extremely excellent.

In addition, when electrodes were formed on the surface of the sintered body using silver paste and the resistance-temperature characteristics were measured using the DC four-terminal method, the sintered body obtained by the solid phase method had a critical transition temperature of 90 and a transition temperature of approximately 4.5, whereas the sintered body using the raw material powder according to the present invention had a critical transition temperature of 91.5 and a transition temperature of 111 of about IK, showing clearly superior properties.

Example 3 Barium oxide 2 with a purity of 99.9fffm% or more
Add 0.0 g to 250 g of methyl alcohol, and gradually add 2.0 g of pure water while stirring with heating to make a methyl alcohol solution of barium hydroxide. To this, add 25 g of triethylamine, twice the molar amount of barium. The mixture was added and stirred to obtain a homogeneous solution (solution (A-3)).

Separately, in 1001i of ethyl alcohol, the number of atoms of copper nitrate trihydrate 43.7 Or and yttrium was 0.5 times as many as the number of atoms of barium so that the number of atoms of copper was 1.5 times the number of atoms of barium. 9 g of yttrium nitrate hexahydrate 2LO was added with stirring so that it was uniformly dissolved.

Thereafter, when solution (A-3) was gradually dropped into this solution while stirring vigorously, a bluish-white coprecipitate was generated.

After filtering this slurry under pressure with nitrogen gas, the solid matter was vacuum dried at about 60° C. and lightly pulverized to obtain a coprecipitated powder. It was confirmed that the filtrate obtained during filtration was transparent, and no precipitate was formed even when oxalic acid was added to it, and the metal components were completely coprecipitated.

This powder is soluble in an acidic aqueous solution, and when the metal composition ratio of the aqueous solution in which it was dissolved was measured by ICP method (plasma emission spectrometry), Y/Ba/Cu was 1.00/
2.01/3.02, and it was found that the coprecipitate of the desired metal composition had been changed.

In addition, when thermogravimetric analysis was performed on this powder, approximately 70%
Complete decomposition occurred at heating temperatures as low as 0°C.

Further, this coprecipitated powder was fired in the air at 750°C for 6 hours, and then slowly cooled to obtain a black calcined powder. When the crystal structure of this powder was measured by X-ray diffraction, it was found that Yl, o Ba2. o Cu3. o
ONY matched the crystal pattern of 6.7 to 6.9).

Further, when the particle shape was observed using a scanning electron microscope, it was confirmed that uniform particles with a negative particle size of about 0.4a+ were precipitated.

Furthermore, approximately 3% by weight of polyethylene wax is added to this calcined powder and coated uniformly to produce approximately 1 ton/cj.
After press molding at a pressure of
After firing at 00°C for 6 hours, the sintered body was slowly cooled and the density of the obtained sintered body was measured and found to be approximately 5.57 g/cj. This corresponded to about 87% of the logic density. When we sintered raw material powder obtained by normal solid phase reaction under similar sintering conditions, the density was 4.07 g/crj (about 6% of the theoretical density).
4%), indicating that the raw material powder produced by the production method of the present invention has extremely excellent sinterability.

In addition, when electrodes were formed on the surface of the sintered body using silver paste and the resistance-temperature characteristics were measured using the DC four-terminal method, the sintered body obtained by the solid phase method had a critical transition temperature of 90 and a transition temperature of approximately 4,5, whereas the sintered body using the raw material powder produced by the manufacturing method of the present invention had a critical transition temperature of 92
The transition temperature was approximately 1K, indicating clearly excellent properties.

Example 4 The same procedure as in Example 3 was carried out except that instead of the triethylamine used in solution (A-3) in Example 3, 7.40 f of monoethanolamine was added to the methyl alcohol solution of barium hydroxide. A coprecipitation reaction was carried out, and the resulting powder was calcined and analyzed by X-ray diffraction, and as in Example 3, Y had an orthorhombic structure. Ba2. . Cu
a. The pattern was changed to match the crystal pattern of 0y (y is 667 to 6.9). Furthermore, the particle size, density, properties, etc. were almost the same as those of Example 3.

Example 5 A methyl alcohol solution of barium hydroxide was prepared without using the triethylamine used to prepare solution (A-3) in Example 3. Add 21 g of jetanolamine to 270 g of this solution so that the molar ratio of jetanolamine/ammonia to 100 g of methyl alcohol is 1/1.
A solution was prepared by adding 37.7 g of barium and 3.4 g of ammonia to a solution equivalent to barium. A coprecipitate was obtained by carrying out a coprecipitation reaction in the same manner as in Example 3, except that this solution was used, and further calcining.
．． A powder was changed that gave exactly the same X-ray diffraction pattern as 2. Furthermore, the particle size, density, properties, etc. were almost the same as those of Example 3.

[Effects of the invention] The method for producing the oxide superconductor raw material powder of the present invention has the following advantages: This is a coprecipitation reaction method from an organic solvent that does not use an aqueous solution, reducing the risk of 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 the target compound can be synthesized at low temperatures and in a short time.

■ Particle size is small and uniform raw material powder can be changed.

■ The coprecipitate is completely inorganic and does not generate carbon during calcination.

■ Furthermore, it is possible to add trace amounts of metal components. It has excellent characteristics such as:

Patent applicant Kanebuchi Chemical Industry Co., Ltd. -1'i

Claims (1)

[Claims] 1. An alcoholic solution (I) of a copper nitrate and a lanthanide metal nitrate is mixed with an alcoholic solution (II) of at least one compound selected from the group consisting of barium hydroxide and barium alkoxide. A method for producing an oxide superconductor raw material powder, which comprises co-precipitating the resulting coprecipitate by thermally decomposing the coprecipitate. 2. The method according to claim 1, wherein the alcoholic solution (II) further comprises at least one compound selected from the group consisting of ammonia and organic amines. 3. The method according to claim 1, wherein the copper nitrate is cupric nitrate. 4. The method according to claim 1, wherein a lanthanide metal salt is used in which all three of the anions forming the salt as a lanthanide metal nitrate are nitrate ions. 5 The concentration of alcohol solution (I) is about 5 to 100 g/
The method according to claim 1, wherein the amount is 100 g. 6. The method according to claim 1, wherein the alcohol in the alcoholic solution (I) is a monohydric alcohol and/or a polyhydric alcohol. 7 The concentration of alcohol solution (II) is approximately 1 to 50 g/10
The method according to claim 1, wherein the amount is 0g. 8. The method according to claim 2, wherein the amount of ammonia and/or organic amine is 0.05 to 10 mol per mol of barium atom.