JPH01246175A - Production of compound oxide ceramics - Google Patents

Abstract

PURPOSE:To obtain a dense superconductor excellent in superconductivity characteristics by precipitating a compound of other constituent metals from a solution thereof with a precipitate-forming agent in a dispersion of compound of partial constituent metals in mixing raw materials for producing Y-Ba-Cu-O based compound oxide ceramics. CONSTITUTION:A compound powder (e.g., CuO powder) containing partial metals constituting compound oxide ceramics (e.g., Y-Ba-Cu-O based ceramics) consisting of a rare earth metal, an alkaline earth metal and copper is dispersed in a dispersion medium (e.g., water) without dissolving the above-mentioned compound. A solution of a compound (e.g., yttrium nitrate or barium nitrate) containing other metals constituting the compound oxide ceramics and a precipitate-forming agent (e.g., aqueous ammonia) are added to the resultant dispersion to form precipitates, which are then dried, calcined, formed and sintered to afford the aimed compound oxide ceramics.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing superconducting ceramics, and more specifically, the present invention relates to a method for producing superconducting ceramics, and more particularly, it uses a dense and easily sinterable oxide powder to produce high-density, uniform composition, and superconducting ceramics. The present invention relates to a method for producing composite oxide ceramics having conductive properties.

[Conventional technology] A superconducting material has a critical temperature Tc and a critical magnetic field Hc.

It is a material that exhibits the property of having zero electrical resistance (superconducting state) under conditions where the critical current Jc is below the critical value.

Complex oxides of copper, alkaline earth metals, and rare earth metals are known as oxide ceramics that exhibit superconductivity at liquid nitrogen temperatures. This ceramic is obtained by sintering a molded product of ceramic raw material powder.

Conventional methods for obtaining ceramic raw material powder include, for example,
The dry method involves mixing powders of each compound of the ceramic components and calcining the mixture.Alternatively, a mixed solution containing all of the desired ceramic components is prepared and a precipitate forming agent such as oxalic acid is added to this. There is a wet method in which a co-precipitate is obtained, which is then dried and calcined.

Composite oxide ceramics are usually produced by molding ceramic raw material powder by -axial pressure molding, CIP, extrusion molding, tape molding, injection molding, etc., followed by pressureless sintering, pressure sintering, atmosphere sintering, etc. There is a method of sintering by tying or the like.

[Problems to be solved by the invention] Superconducting ceramics with excellent properties have a homogeneous composition, few fine particles and racks, and high density (95% of the theoretical density).
(above)).

Raw material powder for producing superconducting ceramics with excellent properties must have properties such as easy sinterability, uniform composition, and high density.

However, in the conventional dry method, it is difficult to obtain a uniform composition by simple mixing, and it is necessary to increase the calcination temperature to obtain the desired oxide, resulting in coarse particles and low calcination density. The critical current Jc is also small.On the other hand, the conventional wet method does not have the drawbacks of the dry method, and a relatively uniform composition is obtained, and the calcination temperature is relatively low.
, L is insufficient and the pH is high, the Cu content becomes insufficient, and it is difficult to control the desired composition.

This invention was made based on the above-mentioned background, and its purpose is to obtain a composite oxide powder that can sufficiently control the target composition, has easy sinterability, has a uniform composition, and has a high density. An object of the present invention is to provide a method for manufacturing composite oxide ceramics having excellent superconducting properties.

[Means for Solving the Problems] The above problems are achieved by a method for producing superconducting composite oxide ceramics according to the present invention.

That is, the present invention is a method for producing a composite oxide ceramic composed of copper, an alkaline earth metal, and a rare earth metal, which comprises the following steps.

(1) Step of preparing a dispersion liquid by dispersing the constituent metal-containing compound A powder of the composite oxide that is insoluble or poorly soluble in the dispersion medium in the dispersion medium (2) On the other hand, constituent metal elements other than the above-mentioned constituent metals Step (3) of preparing a solution of one or more constituent metal-containing compounds B containing a compound A-containing dispersion, by mixing or sequentially mixing the compound B-containing solution with a precipitant in the compound A-containing dispersion to form a precipitate. Forming step (4) After drying the obtained precipitate, calcining it to produce a composite oxide powder (5) Sintering a molded product of the obtained composite oxide powder Preferred embodiment of the present invention The composite oxide ceramic has the following compositional formula.

((RE) ・(M) ) Cu Os-δyl
-3' where RE represents at least one rare earth metal element,
M represents at least one alkaline earth metal element, y
shall satisfy 0<y<1, and δ shall satisfy 0<δ<3.

In a preferred embodiment of the present invention, the composite oxide ceramic has the following compositional formula.

f (RE) ” (M) i-x l 2Cub4
-7, where RE represents at least one rare earth metal element, M represents at least one alkaline earth metal element, X represents 0<x<1, 2 represents 1<z<3, and γ shall satisfy 0 x γ x 4.

This invention will be explained in more detail below.

Preparation of Dispersions and Solutions The alkaline earth metals that can be used in this invention are Mg5Ba, Sr or/and Ca. This choice depends on the composition of the desired final ceramic.

Moreover, the rare earth metals that can be used in this invention include S C% Y SL a SN d % S m
s E u sGd,, D>l5HO% E rSTm
, Yb and/or Lu.

In the production method of the present invention, first, among the raw material compounds of copper, alkaline earth metals and rare earth metals, a constituent metal-containing compound A of the composite oxide which is insoluble or sparingly soluble in the dispersion medium is used.
A dispersion liquid is prepared by dispersing the powder in a dispersion medium (Step 1).

Which element is selected among the constituent elements of the composite oxide ceramic can be appropriately selected depending on the solubility of the compound, the types of other elements, and the like.

Further, the type of compound A is also the same, and includes, for example, insoluble or poorly soluble oxides.

Here, the powder of compound A is preferably submicron fine, for example, the particle size is 0.1 to 2 μm, preferably 0.5 to 0.8 μm.

The dispersion medium used in this invention may be of any type as long as it does not contradict the purpose of this invention. Specifically, such substances include, for example, water, methanol, ethanol,
Acetone, isopropyl alcohol, n-propyl alcohol, t-butyl alcohol, furfuryl alcohol, tetrahydrofurfuryl alcohol, dioxane, tetrahydrofuran, formic acid, acetic acid, butyric acid, methyl lactate, triethyl phosphate, trifluoroacetic acid, ethylene glycol, cellosolve, Methyl cellosolve, carbitol, diacetone alcohol, acetonitrile, cyclohexylamine, ethyleneamine, pyridine, monoethanolamine, mofoline, N-methylpyrrolidone, sulfolane,
dimethyl sulfoxide, etc., and mixtures thereof.

On the other hand, a solution of one or more constituent metal-containing compounds B containing constituent metal elements other than the constituent metals used in the dispersion is prepared (Step 2).

Here, the preparation of the solution containing raw material compound B of copper, alkaline earth metal, and rare earth metal includes hydroxides, oxychlorides, carbonates, hydrogen carbonates, and oxynitrates of copper, alkaline earth metals, and rare earth metals. , sulfates, sulfites, nitrates,
This can be done by directly or indirectly dissolving acetate, formate, oxalate, chloride, fluoride, etc. in a solvent, but if these are water-insoluble, they can be made water-soluble with mineral acids, etc. It can be implemented by The amount of each component added is adjusted so that the final ceramic has the desired composition.

In order to control the sinterability and superconductivity of the superconducting oxide ceramic in this invention, a trace amount of components can be added to the superconducting oxide ceramic by cooling. As such a constituent element, T 1
% S n s M n 1A 1 % Cs 5C
eS VS Bi, Fes Cr, Ni, Ir,
Rh.

Ga is present, and its compounds to be added include its hydroxide, oxychloride, carbonate, bicarbonate, oxynitrate, sulfate, sulfite, nitrate, acetate, formate, oxalate, and chloride. There are also lacquered materials and lacquered materials. This trace component can be added in the liquid or in the calcined composite oxide powder.

Formation of a precipitate In this invention, in a dispersion containing compound A, compound B
mixing the containing solution with a precipitating agent, or sequentially mixing;
Form a precipitate (step 3).

Therefore, it can be carried out in the following mixing manner.

That is, an embodiment in which a compound B-containing solution and a precipitant are added to the above-mentioned compound A-containing dispersion, an embodiment in which a precipitant is added to the above-mentioned compound A-containing dispersion to which a compound B-containing solution has been added, and a water-soluble There is an embodiment in which an organic solvent and a precipitant are added to the above mixed aqueous solution at the same time.

When there are two or more types of compound B-containing solutions, the above-mentioned mixing mode may be performed simultaneously or sequentially in multiple stages.

The precipitant that can be used in this invention can be changed as appropriate depending on the type and concentration of the mixed aqueous solution containing each compound of copper, alkaline earth metal, and rare earth metal. Such substances include, for example, malic acid, tartaric acid, oxalic acid, ammonium oxalate, etc.
Compounds having both or one of 0OH and OH groups, ammonia, ammonium carbonate, sodium carbonate, ammonium hydrogen carbonate, sodium hydrogen carbonate,
There are aqueous solutions of organic reagents such as sodium hydroxide, potassium hydroxide, potassium hydrogen carbonate, oxine, and amines.

Production of composite oxide Next, in the method of the present invention, the produced precipitate is filtered, the collected precipitate is dried, and further calcined at an appropriate temperature to obtain a composite oxide powder.

The calcination temperature is, for example, 400 to 1100°C, preferably about 800°C. In this temperature range, the desired single phase, which is the same composition as the final ceramic, is obtained. Moreover, monodisperse particles of 1 μm or less can be obtained by this method.

Molding of composite oxide In the present invention, the obtained composite oxide powder is then molded. The molding in this step can be performed by applying ordinary techniques. For example, forming methods include isostatic press molding, injection molding, tape forming using a doctor blade, hot pressing, -axis pressure forming, and wire rod forming using wire rod rolling. Can be molded.

Sintering of the molded product The obtained molded product is heated to a predetermined temperature in a predetermined atmosphere and sintered. This sintering temperature is appropriately selected depending on the type and content of copper, alkaline earth metal, and rare earth metal, and the melting point of the composite oxide, and is preferably lower than the melting point and as high as possible.

For example, 500-1200℃, preferably 850-95℃
It is 0°C. If the temperature is below the above lower limit, sintering will be insufficient, while if the temperature exceeds the above upper limit, melting or decomposition may occur, although this may vary depending on the composition, etc., making it impossible to obtain good superconducting properties.

The rate of temperature increase during sintering greatly affects the microstructure and superconducting properties of the ceramic, so it is appropriately set depending on the types and contents of copper, alkaline earth metals, and rare earth metals.

In this invention, sintering is performed in an oxygen or non-oxygen atmosphere. In addition to oxygen, an inert gas such as nitrogen gas, helium, or argon can also be added.

Composite Oxide Ceramics The ceramics obtained by this invention are composite oxide ceramics of copper, alkaline earth metals, and rare earth metals. Preferred ceramics have any of the following compositional formulas.

a, f(RE)” (M)■-,l CaO2
-δ In the formula, RE represents at least one rare earth metal element, M represents at least one alkaline earth metal element selected from Mg5Ba, Sr, or Ca, and y is 0<y
<1, and δ satisfies 0 x δ x 3.

b, ((RE) ' (M) ] Cu
O4-.

x l-x z In the formula, RE and M have the same meanings as above, and X is 0<
Let x<1, 2 satisfy 1<z<3, and γ satisfy O<γ>4.

The manufactured ceramics can exhibit superconductivity and can be used as various superconducting materials.

[For production]

The mechanism of the method for manufacturing the ceramic of the present invention configured as described above will be explained for a better understanding of the present invention. Accordingly, the following is not intended to limit the scope of the invention.

In the method of the present invention, a part of the target ceramic component is dispersed in a dispersion liquid as a powder of a component metal-containing compound A of a composite oxide that is insoluble or poorly soluble in a dispersion medium, and the remaining component is dispersed in a dispersion liquid. Compound B is prepared as a solution. A precipitant is added to the dispersion and the compound B solution to obtain a co-precipitate. This is because, although the ionic product of the ceramic constituent ions in the liquid does not exceed the solubility product, they precipitate together with the formation of other precipitates.

During this precipitation, the ceramic component ions in the liquid absorb or occlude other component ions on the surface of the compound A powder fine particles, undergo ion exchange, or form mixed crystals.
A homogeneous precipitate containing copper, alkaline earth metal and rare earth metal compounds is obtained. Due to the calcining of such a homogeneous precipitate, the resulting oxide powder consists of single-phase particles with a homogeneous composition.

[Effect of the invention] The following effects can be obtained by this invention.

(a) Even for components for which it is extremely difficult to form a complete precipitate using conventional wet methods, by using and dispersing the components as the Compound A powder of the present invention, the desired composition can be sufficiently controlled.

(b) Since the obtained waste oxide powder is easily sinterable, has a uniform composition, and has a high density, oxide ceramics having excellent superconducting properties can be produced.

[Example] This invention will be specifically explained by examples.

Example 1 Fine particle copper(II) oxide 35. 9g in 500ml of water
200 ml of 6N ammonia and 50 g of ammonium bicarbonate were dissolved and mixed therein.

While stirring the obtained powder dispersion, 1.5 g of a mixed aqueous solution containing 41.3 g of yttrium nitrate and 78.4 g of barium nitrate was gradually added dropwise to precipitate all the components. This precipitate was filtered, dried, and heated to 870°C for 5 minutes.
YBa2Cu307, which is calcined for a time and can be expressed by the following compositional formula:
-8 powder was obtained.

The obtained powder was observed using an electron microscope. As a result of the observation, this powder was found to be uniform fine particles with an average size of 0.8 to 1.0 μm.

The obtained powder was subjected to differential thermal analysis. The results are shown in FIG. From this figure, it can be seen that an oxide having the above composition is obtained at about 750° C., and that the precipitate according to the present invention has excellent low-temperature reactivity.

The obtained powder was heated to a diameter of 30 m under a pressure of 700 kg/cd.
+e, molded to 3 mm thick and heated in air at 900°C under normal pressure.
, baked for 8 hours.

Table 1 shows the properties of the obtained superconducting ceramic.

Comparative Example 1 Yttrium nitrate 41.3g, barium nitrate 78.4g
, 2 g of a mixed aqueous solution containing 84.4 g of copper nitrate was prepared. While stirring the mixed aqueous solution, 130 g of oxalic acid was added dropwise to 1.5 p of the H-containing solution to co-precipitate all the components with the oxalic acid.

This precipitate was filtered, dried, and then calcined at 920° C. for 5 hours to obtain a powder of YBa2Cu309-8 having the following composition.

The obtained powder was observed using an electron microscope. As a result of the observation, this powder was irregular particles with an average size of 5 to 6 μm.

The obtained powder was subjected to differential thermal analysis. The results are shown in FIG. From this figure, it can be seen that an oxide of the above composition is partially formed at about 400°C, and a single phase is obtained at 910"C after a reaction at 850°C. This shows that compared to the precipitate of this invention, This shows that the low-temperature reactivity is poor.

The obtained powder was ground in a ball mill to about 1 μm, and
A piece of 30 mm in diameter and 3 m in thickness was molded under a pressure of 0 kg/cd, and fired at 900° C. for 8 hours under normal pressure in air.

Table 1 shows the properties of the obtained superconducting ceramic.

Comparative Example 2 Each powder of Y O1 BaCO3 and CuO was made into the following composition Y B
The mixture was blended to give a 2 Cu 309-δ, mixed in a ball mill, and calcined at 950°C for 5 hours.

The obtained powder was observed using an electron microscope. As a result of the observation, this powder had irregular particles with an average size of 5 to 10 μm.

Table 1 shows the properties of the obtained superconducting ceramic.

Table 1 Examples Example 1 Comparative Example 1 Comparative Example 2 Calcination temperature ("C) 870 920 950 Particle size (tt m
) 0.8-1.0 5-6 5-10Y/Ba
/Cu ratio 1. /2.0/3.01. /1.9/3.11
．． /2.0/3.0 firing density g/cn+35. 3 4
．． 5 4. 5Jc (A/am) 3000
850 750Tc(K) 94
90 90

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing differential thermal analysis of the ceramics obtained in Example 1 and Comparative Example 1. Applicant's agent Mr. Sato

Claims (6)

[Claims] 1. A method for producing composite oxide ceramics composed of copper, alkaline earth metals, and rare earth metals, the method comprising adding a powder of a compound A containing constituent metals of the composite oxide, which is insoluble or sparingly soluble in a dispersion medium, to a dispersion medium. A dispersion liquid is prepared by dispersing, and a solution of one or more constituent metal-containing compounds B containing a constituent metal element other than the constituent metals is mixed with a precipitant in the dispersion liquid, or mixed successively to precipitate. A method for producing composite oxide ceramics, which comprises forming a composite oxide powder, drying the obtained precipitate, calcining it to produce a composite oxide powder, and sintering a molded product of the obtained composite oxide powder. . 2. 2. The method according to claim 1, wherein the alkaline earth metal is Mg, Ba, Sr or/and Ca. 3. 2. The method according to claim 1, wherein the rare earth metal is Sc, Y, La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and/or Lu. 4. The manufacturing method according to claim 1, wherein the composite oxide ceramic has the following compositional formula. {(RE)_y・(M)_1_-_y}CuO_3_-
_δ In the formula, RE is Sc, Y, La, Nd, Sm, Eu,
Represents at least one rare earth metal element selected from Gd, Dy, Ho, Er, Tm, Yb and Lu, M is M
represents at least one alkaline earth metal element selected from g, Ba, Sr, or Ca, y represents 0<y<1, and δ
shall satisfy 0<δ<3. 5. The manufacturing method according to claim 1, wherein the composite oxide ceramic has the following compositional formula. {(RE)_x・(M)_1_-_x}_zCuO_4
＿−＿γ In the formula, RE is Sc, Y, La, Ce, Pr, N
d, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er
, Tm, Yb, and Lu, and M represents Mg, Ba, Sr, or C.
represents at least one alkaline earth metal element selected from a, x represents 0<x<1, z represents 1<z<3, and γ represents 0
<γ<4 shall be satisfied. 6. The dispersion medium is water, methanol, ethanol, acetone, isopropyl alcohol, n-propyl alcohol,
t-Butyl alcohol, furfuryl alcohol, tetrahydrofurfuryl alcohol, dioxane, tetrahydrofuran, formic acid, acetic acid, butyric acid, methyl lactate, triethyl phosphate, trifluoroacetic acid, ethylene glycol, cellosolve, methyl cellosolve, carbitol, diacetone alcohol, acetonitrile, cyclohexylamine,
The manufacturing method according to any one of claims 1 to 5, comprising at least one selected from ethyleneamine, pyridine, monoethanolamine, mofoline, N-methylpyrrolidone, sulfolane, and dimethylsulfoxide.