JPH02212308A - Manufacture of ceramic oxide having supercondctivity - Google Patents

Abstract

PURPOSE: To mix component metals thoroughly, to enable continuous treatment, and to obtain a superconductor by subjecting the droplets of aerosol of individual aqueous ammonium-metal-aminopolycarboxylic acid solutions of respective metal components of the desired conductive oxide to flash decomposition and to oxidation.

CONSTITUTION: (i) Individual aqueous ammonium-metal-aminopolycarboxylic acid solution of respective metal components of the ceramic metal oxide to be formed is prepared. (ii) The above respective ammonium-metal- aminocarboxylic acid solutions are mixed in stoichiometric ratio giving the desired ceramic metal oxide to be formed by means of decomposition, by which a precursor solution is prepared. (ii) The aerosol of droplets of the precursor solution is prepared in an oxygen-containing air flow. (iv) Subsequently, the above droplets in the air flow are subjected to flash decomposition and to oxidation, to produce ceramic oxide metal grains as a product.

COPYRIGHT: (C)1990,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention relates to a method for producing ceramic oxides having superconductivity by aerosol pyrolysis of metal-aminopolycarboxylic acid solutions such as metal-ethylenediaminetetraacetic acid solutions. .

[Prior Art] Superconducting materials have been known since 1911, but even modern niobium or vanadium alloys require extremely expensive cooling using liquid helium boiling at 4° to operate in superconducting mode. Requires.

U.S. Pat. Nos. 4,411,959 and 4.

No. 575.927 (Braginski et al.) is wire-shaped and used for superconductor production, and has a diameter of 1 μ! Discloses smaller particulate niobium or vanadium compounds.

Normal Y B a *Cu @01~B or rl:2:
Orthorhombic crystal system (0-th ceramic oxide)
Perovskite-related ceramic oxides, including alkaline earth metal-copper oxides such as yttrium-barium-copper oxide materials, are well-known "high temperature" superconducting materials.

This 1:2:3 ceramic oxide material has been found to exhibit electrical superconductivity in the 93° region, ie, essentially loses its electrical resistance.

Ceramics based on 1:2:3 ceramic oxides and other alkaline earth metal-copper oxides exhibit superconducting mode at temperatures sufficiently high due to the 77° boiling point of relatively cheap and abundant liquid nitrogen. It has the potential to be widely used in composite windings of high-current magnets, energy storage coils, and long-distance power transmission.

Other recent ceramic oxides of interest in the area of superconductivity include P. Halder et al., Science, Vol. 241, 1198-
(Bi or Tl), (Ba or Sr) Caa-+Cuno as described in 1200 (1988)
Copper (n) based on bismuth and thallium, such as m [Formula %Formula %] B i *CIL ts r *Cu *0s-a
There are acid salts.

These alkaline earth metal-copper oxide based ceramic oxides are usually formed by mixing appropriate metal oxides or carbonates in appropriate molar ratios and sintering. For example, to make l:2:3 ceramic oxide,
Y*Oss B 71 CO* and CuO to Y:
Mix so that the molar ratio of Ba:Cu is 1:2:3,
When heated in air at 900℃ for about 12 hours, YB a
*c u *C) r-x mass is obtained. However, such processes do not provide the homogeneity necessary to maximize the superconductivity of the product. In addition, this process
It is a very time consuming batch process and may require several sintering/regrinding cycles. Furthermore, it is also difficult to create thin films from the manufactured particles.

U.S. Patent Application No. 149 filed January 27, 1988
No. 223 (Charles et al.) discloses an attempt to solve the conventional problem by aerosol pyrolysis using an aqueous solution of the nitrate of the metal.

There, very small droplets of an aqueous nitrate solution, for example a Y--Ba--Cu nitrate solution, are dispersed by ultrasound into an oxygen-containing gas stream, followed by flash decomposition and oxidation to obtain powders smaller than 1 μm. Intimate mixing is achieved by dissolving the metal components, and homogeneity is maintained during processing by flash decomposition and oxidation. Flash decomposition and oxidation is accomplished in a flame, in a tube furnace or in a plasma torch between about 600<0>C and 1,000<0>C, and particle recovery is performed by gas filters and/or electrostatic precipitators.

Although this process is very suitable for T-Ba-Cu superconductors, modifications are required for application to high temperature superconductors containing Bi or T1.

In order to extend this to metals such as Bi and Tl, the nitrate solution must be made strongly acidic with nitric acid to prevent precipitation of oxynitrates. This high degree of acidity can corrode equipment. It can also produce high concentrations of nitrogen oxides in the exhaust stream, which can again react with oxide particles to reform nitrates.

Similarly, U.S. Patent Application No. 154393 (Charles et al.) filed on February 1, 1988 also describes
and Cu β-diketone complex from about 150°C to 350°C.
Attempts to solve the conventional problem by producing a thin ceramic film by vaporizing between is disclosed. Although this chemical vapor deposition method produces excellent homogeneous films, it is not easily applicable to the production of ceramic oxide particles.

[Problem to be Solved by the Invention] Bi or Tl that avoids the problems caused by the low solution pH required when using nitrate solutions, provides intimate mixing of the component metals, and allows continuous processing.
What is needed is a method for making superconducting oxide powders containing superconducting oxide powders.

One primary objective of the present invention is to provide such a process.

SUMMARY OF THE INVENTION Accordingly, the present invention comprises the steps of: (i) forming an aqueous solution of the individual ammonium-metal-amino polycarboxylic acids of each metal component of the ceramic metal oxide to be formed; )
(1ii) mixing the individual ammonium-metal-aminopolycarboxylic acid solutions in a stoichiometric ratio giving the desired ceramic metal oxide to be formed by decomposition to obtain a precursor solution; (1ii) in an oxygen-containing gas stream; (iv) flash decomposition and oxidation of the droplets in the air stream to produce ceramic metal oxide particles as a product. A method for producing a mixed ceramic metal oxide with superconducting ability.

These particles can be collected on a filter or by an electrostatic sedimentation device, or deposited as a thick film on a heated substrate. Metal components used in the reaction product include YlBa, Cu, Ca, Sr, T
Preferably, it is selected from the group consisting of 1 and Bi. One of the reaction products will contain Cu as the metal component.

Preferably, the aminopolycarboxylic acid component of the reaction product solution is derived from ethylenediaminetetraacetic acid (EDTA).

The method of the invention does not require the use of highly acidic solutions.
In a continuous process, metal-ceramic oxide particles can be produced with a uniform distribution throughout the particles.

For a clearer understanding of the invention, preferred embodiments of the invention will now be described with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a process for manufacturing a mixed ceramic metal oxide having superconductivity.

FIGS. 2A and 2B are X-ray diffraction spectra of the Y-Ba-Cu oxide particles formed in the examples and the contrast W, Wong-N, respectively.
g) et al., "X-ray powder properties of barley Y Cu 307-X", Advances in Ceramic Materials (Adv, Cerasic Mat,) No. 2
FIG. 3 is an X-ray diffraction spectrum diagram of B a *Y Cu sow □ taken from Volume 3B Special Issue, pages 565-576 (1987).

FIGS. 3A and 3B are X-ray diffraction spectra of B1-5r-Ca-Cu oxide particles formed in Examples and H as a control, respectively.

Maeda et al., “Novel high Tc oxide superconductor without rare earth elements,” Japanese Journal of Applied Physics (Japan, J.

Appl, Phys,) Volume 27 No. 2 L209-2
B15rCaCutO taken from page 10 (1988)
It is an X-ray diffraction spectrum diagram of x.

The ceramic oxide produced by the method of the present invention is YBa
Yttrium-containing alkaline earth metal-copper oxides such as mCusOt-x ceramics, bismuth-containing alkaline earth metal-copper oxides such as (Bi)x(Ha or 5r)Can-1CunOz ceramics, and (Tl
) x (Ba or 5r) Can-tcunoz ceramics, including thallium-containing alkaline earth metal-copper oxides such as (3/2)x+2n+2-δ).

These ceramic metal oxides are formed according to the process shown in FIG. In step (i), a separate ammonium-metal-aminopolycarboxylic acid reaction product solution is formed for each metal component of the ceramic metal oxide to be formed. Preferred metals are Y, Ba, Cu,
Ca, Sr.

Selected from the group consisting of T1 and Bi. In either case, Cu is present. For example, YBavcu*c)
When producing r-x particles, at least three reaction product solutions are formed, at least one containing Y, at least one containing Ba, and at least one containing Cu. . In most cases, only one reaction product solution is used for each metal needed in the final metal-ceramic oxide. Unlike Bi- and Tl-containing oxides,
Although the superconductor YBatcuso,-* is easily produced using nitrate solutions, its preparation serves herein to illustrate the general aminopolycarboxylic acid process of the present invention.

The formation of these ammonium-metal-aminopolycarboxylic acid reaction products is described below (for example, copper and ethylenediaminetetraacetic acid [H, (ED
This will be explained using TA)].

(carboxylic acid) (amino) (alkylene) (amino) (
Carboxylic acid) host almost insoluble acid H, (EDTA
) in water, stirred, and then added with a stoichiometric amount of dilute N
Semi-neutralize with H,OH. The resulting diammonium salt completely dissolves as follows: H, (to EDT) + 2NH, OH→ (NH4)tHt(EDTA) + 2H*0 Then, as a second reaction, the following two Both are possible: (NH4)tHt(EDTA)+Cu (OH)*”(
NH4)*Cu (EDTA)+HtO or (NH4)tHt(EDTA)+Cu (COs)-(
NH4)*Cu(EDTA)+C*0+HtO In the first reaction, a combined stoichiometric amount of freshly precipitated copper hydroxide is added as a washed solid and stirred with heating until a clear solution is obtained. The second reaction shows that in some cases the corresponding carbonate can be used instead of the hydroxide. These reactions are for the divalent metal Cu''''. Trivalent metals, such as Tl'', typically give compounds such as (NH4)Tl (EDTA), which dissociate in solution to form NH,'' and Tl (EDTA)- ions. . Similarly, BI3' gives the compound (NH,)B i (EDTA),
This shows that (NH,)'' ions and Bi (EDTA) in solution.
- dissociates into ions.

In some cases, the hydroxide is added directly to the acid: Cu(O
H)t+H4(EDTA)-H*Cu(EDTA)+
21 to 110 and then neutralize: H* Cu (EDTA) + 2 N H4
It has been found that 0H→(NH4)*Cu (EDTA)+2H*0 is more convenient. Here, two nearly insoluble reactants are suspended together in water and stirred with heating until a clear solution is obtained. This is followed by a stoichiometric amount of NH.

Add OH, (NH4)! Cu (E D T
A) is obtained. Other reactions may also be used as long as they do not result in undesirable ionic by-products. Such solutions, unlike nitrate solutions, are not strongly acidic and have a pH close to 7, usually between 6°5 and 6°5.
It has a pH of 7.5.

In summary, a metal hydroxide or metal carbonate can be reacted with an ammonium compound such as ammonium hydroxide and an aminopolycarboxylic acid such as ethylenediaminetetraacetic acid in various orders. The final ammonium-copper-aminopolycarboxylic acid reaction product, i.e., the ammonium-copper-ethylenediaminetetraacetic acid reaction product, is a complex whose anionic component has the following chemical structure [wherein For clarity, the bond in the Cu ring structure is indicated by a broken line]: Metal-(EDTA)
The complex, as described above, is an anion. Therefore, cations must be present to cancel out the charge.

The method of the invention requires the use of cations that do not appear in the final superconducting product.

Only cations can be used that are destroyed by heating and converted to volatile products. Such cations include ammonium (NH,) ions and organic substituted ammonium ions,
For example, tetramethylammonium ion [(CHI),
N]". As used herein, "ammonium" also includes substituted ammonium types. Monovalent metal cations such as Na'' are specifically excluded as they enter the final mixed oxide product.

Methods for forming aminopolycarboxylic acids, one of the main components used in the above reactions, are well known; for example, one particular type is described in U.S. Pat. No. 2,130,505 [Munz
nz) ] taught in the specification. In the case of the present invention,
The main conditions required for the aminopolycarboxylic acid to provide an acid component in the reaction product solution are = (1) the molecule has at least one basic nitrogen atom and at least 2, preferably 3 to 5 carboxyl atoms; (2) the intramolecular arrangement of the nitrogen atom and the carboxyl group,
When reacting with a metal, some ring structures [
Refer to structural formula (n)].

Many compounds are known that meet these two requirements.

A preferred compound is ethylenediaminetetraacetic acid [structural formula (■)], which is readily available and inexpensive. Examples of other suitable aminopolycarboxylic acids include diethylenetriaminepentaacetic acid [structural formula (III)], hydroxyethylethylenediaminetriacetic acid [structural formula (■)], and nitrilotriacetic acid [structural formula (■)]. It will be done.

C)1. C0OH In step (ii), shown in Figure 1, the various reaction product solutions are combined in stoichiometric ratios to give the desired ceramic metal oxide to be formed by decomposition. For example, if Y Ba ICu 307-X is the desired oxide upon decomposition, ammonium-Y
-(EDTA), ammonium-Ba-(EDTA)
and ammonium-Cu(EDTA) solutions, Y
, Ba and Cu in a molar ratio of 1:2:3 to obtain a metal oxide precursor solution, ie a solution capable of producing metal oxides upon heating. (Bi)x (Sr)
To obtain Can-tcuno++, Bi, Sr, Ca
(T1)X(Sr)Can-1cun using ammonium-(EDTA) solutions containing
In the oxno case, ammonium-(EDTA) solutions containing T15Sr, Ca and Cu are used. In step (ii), various reaction product solutions are mixed at about 25°C.

In step (iii), an aerosol or mist of precursor solution droplets is formed in an oxygen-containing air stream. A fine mist of an aerosol spray can be formed by ultrasonically agitating the precursor solution in a stream of air using a modified ultrasonic room humidifier or other suitable device.

In step (1v), the droplets are flash decomposed and oxidized to produce product ceramic metal oxide particles. In some cases, it may be necessary to anneal the ceramic oxide particles in O3 at 750<0>C to 950<0>C to obtain the desired structure.

In the case of powder production, flash decomposition, oxidation can be carried out using various heat sources, such as flames, tube furnaces or plasma torches, and the reaction is generally carried out at temperatures between 600°C and t,o.
Occurs at temperatures of 0°C. The product can be recovered by known means including various filters and electrostatic precipitators. The powder can then be processed into a superconductor shape, such as into ceramic pellets, by methods well known to those skilled in the art. For example, the pellets can be placed between suitable metal tubes or suitable metal plates and drawn or rolled to produce conductive filaments or ribbons.

The aerosol can also be flash decomposed and oxidized by contacting with substrates heated to 700°C to t,ooo°C. In this case, the aerosol may be preheated to an intermediate temperature, which is lower than the temperature effective to decompose and oxidize the precursor solution. Although other types of substrates can be used, including metal substrates, it will be common to use ceramic substrates. Oriented crystal substrates, particularly single crystal perovskite substrates such as strotium titanate, are preferred. For example, an ultrasonic mist can be electrically charged, and any opposite charge on or behind the substrate will attract small droplets or particles to the substrate. Therefore, in order to improve the efficiency of oxide deposition on the substrate, a method of electrostatically enhancing the deposition may be used.

Step (iv) involves a very rapid reaction of extremely fine droplets, allowing us to accurately trace the sequence of reactions that occur during flash decomposition and oxidation to form metal oxide particles or films on the heated substrate. It is impossible to know. However, for the formation of l:2:3 ceramic oxide,
The liquid aerosol particles undergo a series of processes including flash evaporation of the water solvent, stepwise decomposition and reaction of the oxide residues to form a crystalline mixed oxide, typically in the range of 700°C to 1,000°C. It is thought that it is converted into mixed oxide particles.

[Example] The present invention will be explained below with reference to Examples.

1:2:3 metal ceramic oxide YBalCus
Particles of Ot-x are prepared from a mixture of metal oxide precursor solutions of (1) ammonium-yttrium-ethylenediaminetetraacetic acid, (2) ammonium-barium-ethylenediaminetetraacetic acid, and (3) ammonium-copper-ethylenediaminetetraacetic acid. did. These individual ammonium-
The metal-aminopolycarboxylic acid is prepared by suspending ethylenediaminetetraacetic acid in water and reacting with ammonium hydroxide to form the diammonium salt, followed by mixing the freshly precipitated metal with stirring at about 30°C to 35°C. Formed by adding hydroxide to give a clear solution. These acid-ammonium-metals are Y.

Ba and Cu are mixed in a molar ratio of 1:2:3,
The unit concentration is [Y] =0.01 mol/12. [Ba
]=0.02 mol/12, [Cu]=0.03 mol/Q
And so.

The mixed metal oxide precursor solution was placed in a modified portable ultrasonic room humidifier using an ultrasonic transducer. The transducer vibrated at approximately 1.7 MHz and created an extremely fine aerosol mist of solution. This aerosol was mixed with a flow of oxygen gas and then passed through a quartz tube in a tubular resistance furnace maintained at 1000° C. at a flow rate of 4 Q/min. The total residence time of the metal oxide precursor aerosol droplets in the furnace was approximately 2 seconds. The inner diameter of the tubular reactor is 2.5c16
The length of the heating zone above 00°C was 25 cm.

The aerosol droplets underwent flash decomposition in the presence of oxygen to form metal-ceramic oxide particles. These particles were collected on a polytetrafluoroethylene Millipore filter. The diameter of the collected particles is approximately 0.1μm-1μ
It was m. For the sample of collected particles, the second
The X-ray diffraction spectrum shown in the figure was obtained, and Y B a ICu
5C) Comparison with reference X-ray diffraction spectrum for r-x, Figure 2B. By comparison, Y B iL tc
It can be seen that u*07-x particles were obtained.

(1) ammonium-bismuth-ethylenediaminetetraacetic acid, (2) ammonium-calcium-ethylenediaminetetraacetic acid, (3) as generally described above.
Metal oxide precursor solution mixtures of (4) ammonium-strotium-ethylenediaminetetraacetic acid and (4) ammonium-copper-ethylenediaminetetraacetic acid were prepared. This metal oxide precursor solution was placed in an ultrasonic humidifier to generate an extremely fine aerosol mist, which was mixed with an oxygen stream and then passed through a tubular resistance furnace maintained at 900°C at a flow rate of 4Q/min. . Here, metal-ceramic oxide particles formed from small droplets were collected in a tubular electrostatic precipitator.

The electrostatically collected powder was then heated in oxygen at 850°C for approximately 12
Annealed for an hour.

Comparing the X-ray diffraction spectrum shown in Figure 3A with the reference X-ray diffraction spectrum shown in Figure 3B, B1
It can be seen that 5rCaCutOx was formed.

[Effects of the Invention] According to the production method of the present invention, metal-ceramic oxide particles having a uniform distribution throughout the particles can be produced in a continuous process without using highly acidic solutions.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a process for manufacturing a mixed ceramic metal oxide with superconducting ability. FIG. 2A and FIG. 2B are an X-ray diffraction spectrum of Y-Ba-Cu oxide particles formed in Examples and an X-ray diffraction spectrum of BatYCuaO7-5 as a control, respectively. FIG. 3A and FIG. 3B are X-ray diffraction spectra of B1-9r-Ca-Cu oxide particles formed in Examples and an X-ray diffraction spectrum of B15rCaCu*Ox as a control, respectively. FIG, 1 FIG, 2Δ FIG, 2B

Claims (17)

[Claims] (1) (i) forming an aqueous solution of the individual ammonium-metal-amino polycarboxylic acids of each metal component of the ceramic metal oxide to be formed; (ii) said individual ammonium-metal-amino polycarboxylic acids; (iii) mixing the solutions in a stoichiometric ratio to give the desired ceramic metal oxide to be formed by decomposition to obtain a precursor solution; (iii) forming small droplets of the precursor solution in an oxygen-containing gas stream; a superconducting ceramic metal oxide mixture, characterized in that: forming an aerosol; and (iv) flash decomposing and oxidizing said small droplets in an air stream to produce ceramic metal oxide particles as a product. manufacturing method. (2) The method according to claim 1, wherein at least one metal in the reaction product solution formed in step (i) is Cu. (3) The metals in the reaction product solution are Y, Ba, Cu, Ca
, Sr, Ti, and Bi. (4) The aminopolycarboxylic acid component present in the reaction product solution formed in step (i) is an aminopolycarboxylic acid component having at least one basic nitrogen atom and at least two carboxylic acid groups per molecule. 4. The method according to claim 1, wherein the method is derived from an acid. (5) The aminopolycarboxylic acid components present in the reaction product solution formed in step (i) are mutually arranged so that several ring structures are formed together with the metal when they react with the metal ion. Claim 1, characterized in that the aminopolycarboxylic acid is derived from an aminopolycarboxylic acid having a basic nitrogen atom and a plurality of carboxylic acid groups in each molecule,
The manufacturing method described in 2 or 3. (6) The precursor solution containing ammonium-metal-aminopolycarboxylic acid is mixed in step (ii) and the pH is 6.
6. Process according to any one of the preceding claims, characterized in that a precursor solution of 5 to 7.5 is obtained. (7) The individual ammonium-metal-aminopolycarboxylic acid reaction products formed in step (i) are
7. The method according to any one of claims 1 to 6, characterized in that it is a mixture of Y-aminopolycarboxylic acid, ammonium-Ba-aminopolycarboxylic acid and ammonium-Cu-aminopolycarboxylic acid. (8) The individual ammonium-metal-aminopolycarboxylic acid reaction products formed in step (i) are
Claims 1 to 3, characterized in that it is a mixture of Bi-aminopolycarboxylic acid, ammonium-Sr-aminopolycarboxylic acid, ammonium-Ca-aminopolycarboxylic acid and ammonium-Cu-aminopolycarboxylic acid.
6. The manufacturing method according to any one of 6. (9) The individual ammonium-metal-aminopolycarboxylic acid reaction products formed in step (i) are
Claims 1 to 3, characterized in that it is a mixture of Tl-aminopolycarboxylic acid, ammonium-Sr-aminopolycarboxylic acid, ammonium-Ca-aminopolycarboxylic acid and ammonium-Cu-aminopolycarboxylic acid.
6. The manufacturing method according to any one of 6. (10) Individual ammonium formed in step (i)
The metal-aminopolycarboxylic acid reaction product is ammonium-Bi-aminopolycarboxylic acid, ammonium-Ba-
Claim 1, characterized in that it is a mixture of aminopolycarboxylic acid, ammonium-Ca-aminopolycarboxylic acid, and ammonium-Cu aminopolycarboxylic acid.
7. The manufacturing method according to any one of . (11) Individual ammonium formed in step (i)
The metal-aminopolycarboxylic acid reaction product is ammonium-Tl-aminopolycarboxylic acid, ammonium-Ba-
Claim 1 characterized in that it is a mixture of aminopolycarboxylic acid, ammonium-Ca-aminopolycarboxylic acid and ammonium-Cu-aminopolycarboxylic acid.
7. The manufacturing method according to any one of . (12) The method according to any one of claims 1 to 11, wherein the ammonium-metal-aminopolycarboxylic acid reaction product is ammonium-metal-ethylenediaminetetraacetic acid. (13) Any one of claims 1 to 12, characterized in that in step (ii), the solutions are mixed at about 25°C.
The manufacturing method described in. (14) In step (iii), the aerosol is a fine mist generated by ultrasonic stirring of the precursor solution.
The manufacturing method described in. (15) In step (iv), 600°C to 1,000°C
Claims 1 to 14 characterized in that the small droplets are flash decomposed and oxidized in the presence of a heat source having a temperature of °C.
The manufacturing method according to any one of. (16) 700°C to 1,000°C in step (iv)
Claims 1 to 14 characterized in that the droplets are flash decomposed and oxidized by contact with a substrate heated to
The manufacturing method according to any one of. (17) 75% of the product metal ceramic oxide particles
17. Process according to any one of the preceding claims, characterized in that it is annealed in O_2 at 0<0>C to 950<0>C.