JPH0214825A - Production of bi-based oxide superconducting material - Google Patents

Abstract

PURPOSE:To efficiently obtain a Bi-based oxide superconducting material having the high critical temperature, mechanical strength, etc., by electrodepositing a Bi-Sr-Ca-Cu-O-based superconductor powder on the surface of an electrically conductive substrate by an electrophoretic deposition method, forming a dense electrodeposition layer and heat-treating the resultant layer. CONSTITUTION:Powder of a Bi-Sr-Ca-Cu-O-based oxide superconductor or precursor powder of an oxide superconductor is dispersed in N,N-dimethylformamide, and, as necessary, small amounts of an electrolyte, gelatin, etc., are added to produce an electrodeposition solution 3, which is then contained in an electrodeposition vessel 2. A substrate 1 having an electrically conductive material on at least the surface thereof is inserted into the electrodeposition solution 3. The substrate 1 is then used as a cathode to carry out electrophoretic deposition and form an electrodeposition layer 4 containing elements constituting an oxide superconductor on the surface thereof. The resultant superconducting material 5 is subsequently heat-treated to afford the objective Bi-based oxide superconducting material.

Description

[Detailed Description of the Invention] "Industrial Application Field" The present invention is being developed for use in superconducting magnets used in magnetic levitation trains, medical devices, magnetic propulsion ships, etc., and for power transmission lines. The r1i-based oxide super 7I! This invention relates to a method for manufacturing a conductive material.

``Prior art J'' Recently, various oxide superconductors have been discovered whose critical temperature ('l'c) for transitioning from a normal conducting state to a superconducting state exceeds the liquid nitrogen temperature.This type of oxidation Super?
The tf conductor has the formula Y -B a-Cu-0 or I
It is an oxide represented by Ii-3r-Ca-Cu-0, etc., and is significantly advantageous compared to conventional alloy-based or metal 11M compound-based superconductors, which require cooling with liquid helium. Because it can be used under cooling conditions, it is being researched as a highly promising superconducting material for practical use.

By the way, conventionally, 1111
As a method for forming a thick film made of an oxide superconductor,
A method has been considered in which a printing material is created by adding a solvent such as pine oil or an FF machine binder to oxide superconducting powder, and this printing material is screen printed onto a base material.

Alternatively, a coating solution may be prepared in the same manner as in the production of the printing materials, and this coating solution may be spray-painted onto the surface of the substrate, or the substrate may be immersed in this coating solution and then drawn.
A method has been considered in which a coating film is formed on the surface of the L.

Furthermore, a method has been considered in which an oxide superconducting layer is formed on the surface of a base material using a thin film forming method such as a sputtering method or a vapor deposition method used in the field of semiconductor manufacturing.

``Problem to be solved by the invention'' However, although the surface screen printing method can be applied to parts with simple shapes such as the surface of a flat plate or the outer surface of a cylinder, There is a problem that it cannot be applied to a base material having a shape including a portion with a large curvature, such as, or a base material having a complicated shape having a 4' convex portion.

Further, the maximum thickness of a film that can be formed by screen printing is about 200 μm, and there is a problem in that it is difficult to form a superconducting thick film with a thickness of 200 μm or more.

Furthermore, in the above-mentioned painting method and dipping method, when using a substrate with a complicated shape, if the viscosity of the coating liquid is increased, it may be difficult to uniformly apply the coating liquid to every corner of the substrate. However, if the viscosity of the coating liquid is lowered, the coating liquid will run down when the substrate is pulled out of the cloth liquid, making it impossible to apply it uniformly to the surface of the substrate, making it impossible to apply it to substrates with complex shapes. there were. In addition, when forming a paint layer on the surface of a base material and then applying heat treatment to sinter the substances contained in the paint layer to generate an oxide superconductor, resin components such as binders contained in the paint layer burn. Therefore, there was a problem that the oxide superconductor peeled off from the base material.

On the other hand, in the AI film forming method such as the sputtering method, the WAIi that can be formed is about several microns and the film forming time is long, so it is difficult to form an oxide superconducting thick film with a thickness of 200 microns or more. This is difficult, and there is a problem in that even a superconducting thin film with a thickness of several μIi requires a long manufacturing time.

In addition, these methods require film formation in a specific atmosphere such as a vacuum, so the size of the substrate is limited to a size that can be stored in the manufacturing equipment. There was a problem that it could not be applied to base materials.

The present invention has been made in view of the above-mentioned problems, and is capable of forming a dense thick film of oxide superconductor on the surface of a base material in a short time, has excellent superconducting properties such as critical temperature, and has excellent mechanical properties. The purpose of the present invention is to provide a method for efficiently manufacturing a Bi-based oxide superconducting material with high strength.

[Means for Solving the Problems] In the method for producing an oxide superconductor of the present invention, in the method for producing an oxide superconducting material comprising a Di-based oxide superconductor, a powder of the oxide superconductor is used. Alternatively, electrophoretic electrodeposition is performed in a nutrient solution in which precursor powder of an oxide superconductor is dispersed in N-N dimethylformamide, using a base material having conductivity at least on the surface as a cathode,
The method of solving the problem was to form an electrodeposited layer containing the elements constituting the oxide superconductor on the surface of the base material, and then to perform heat treatment.

"Operation" Ili-based oxide superconductor powder or oxide superconductor precursor powder is applied to the surface of the base material by electrophoretic electrodeposition.
By depositing and forming a Wi bamboo layer containing the elements constituting the oxide superconductor, and then applying heat treatment, a dense and uniform sintered layer of i-based oxide superconductor is formed on the surface of the base material. It is formed.

"Example" Figures 1 to 4 show that [3i-S
? FIG. 3 is a rounded diagram illustrating an example of manufacturing a -Ca-Cu-0-based superconducting material. In the method for manufacturing a superconducting material according to this example, first, a round wire-shaped base material 1 is pushed into an electrodeposition liquid 3 contained in an electrodeposition bath 2, and electrophoresis is performed for 7 tf to deposit the electrodeposition on its surface. A layer 4 is formed to produce a superconducting material 5 whose cross-sectional structure is shown in FIG.

The base material violet used in this example is preferably:
A noble metal with a melting point of 800°C or higher and good oxidation resistance.
11. '1' as Z ts I-I Is V
%Nb%W Single metal scrap such as sCu, Cu-Ni alloy, Cu-AI alloy, Ni-AI alloy, Ti
-V alloy, monel metal, stainless steel, chromel,
Metal base materials such as allomel and kanthal are used, and furthermore, ceramic base materials such as quartz glass, zirconia, YSZ, alumina, sapphire, titanate compounds such as strondium titanate, and magnesia and titanium oxide are used. A base material coated with a metal such as Ags N 1% Cu using a pattern forming method such as an electrolytic plating method, a sputtering method, an ion blating method, or a vacuum evaporation method is used.

The electrodeposition liquid 3 is E l + S r + Ca +
An i-based super-conducting powder having a composition such as Cu t OX is dispersed in N-N dimethylformamide. m of superconducting powder in this dispersion medium Ie
is preferably in the range of 1 to 50 (H). If the amount of superconducting powder is 50097 (1 or more), the superconducting powder will not be electrodeposited on the surface of the substrate in a dense and uniform state, and If it is less than II/(l, the voiding efficiency will deteriorate. Also, in order to disperse the superconducting powder in the dispersion medium,
It is desirable to perform ultrasonic stirring, and the stirring operation may also be performed by adding a small amount of water, gelatin, starch, electrolyte, etc. to the dispersion medium. At this time, N- used as a dispersion medium
The amount of water contained in N dimethylformamide I vo
Up to l,%, no gas is generated due to water electrolysis,
Further, the dispersion state of the superconducting powder was good and there were no problems at all. Note that, if necessary, a material such as titanium oxide that serves as a sintering aid for the oxide superconductor is added to the electrodeposition liquid 3.

The superconducting powder mentioned above is preferably one having a particle size of 50 μm or less, and in particular, a powder having a particle size of 30 μm or less is preferably used in order to prevent the powder particles from settling and to disperse them uniformly. As a method for producing this superconducting powder, for example, Di oxide powder, Cu oxide powder, Ca carbonate powder, and Sf
Carbonate powder of Bi:Sr:Ca:Cu=I:I
:l:2 (molar ratio) to obtain a mixed powder, and then this mixed powder is calcined in the air or oxygen atmosphere at 750 to 850°C for several minutes to several tens of hours. This calcined powder is then subjected to a series of operations of compaction, heating, and pulverization once or twice or more to create B1-8 r-Ca-Cu-0 based superconducting powder. Powder mixing methods are preferred. The pulverization process can be carried out using a general pulverization apparatus such as an automatic mortar or a ball mill, and a wet pulverization process in which NN dimethylformamide is added and ball mill pulverization is performed may also be used. Note that the method for producing the superconducting powder is not limited to the powder mixing method described above, and a coprecipitation method or a sol-gel method may be used. Further, instead of the superconducting powder in the electrodeposition liquid 3, the above-mentioned calcined powder (preparative precursor powder) may be used.

Then, the electrophoresis y! shown in FIG. &! 1. Therefore, in order to form electrodeposition I44 on the surface of the base material 1, the base material 1 is placed in the electrodeposition liquid 3, this base material 1 is used as a cathode, and this base material 1 and the electrodeposition tank 2 are A voltage is applied between the anode 6 and the anode 6 disposed at. In this electrophoretic electrodeposition, both the constant voltage method and the constant current method are possible, and in addition to direct current, the current waveform can be pulsed, AC/DC ffi, etc. in which the substrate 1 temporarily serves as a cathode.
Current waveforms such as tatami, intermittent, etc. can be used. Constant H
When using the E method, it is sufficient to apply a voltage of IV or more, and when using the constant current density method, the current intensity should be set to I~
It is desirable to set it in the range of 500 μA/as”.
As the anode 6, common electrode materials such as a platinum plate, a stainless steel plate, and a carbon electrode can be used. Further, it is desirable that the surface area of the anode 6 be larger than the surface area of the material 1.

As mentioned above, by applying a voltage between the base material 1, which serves as a cathode, and the anode 6, the superconducting powder dispersed in the electrodeposition liquid 3 becomes positively charged, and the surface of the base material 1, which serves as a cathode, is charged. Electrodeposited. Then, a dense 1N layer 4 made of superconducting powder is formed on the surface of the base material 1, resulting in a superconducting material 5 shown in FIG. of a predetermined thickness in the electrodeposition bath 2? The superconducting material 5 on which the Ii young layer 4 is formed is pulled up from the fried M2,
Next, drying treatment using strong air is performed to remove N--N dimethylformamide remaining on the surface portion. For this drying treatment, heating at a temperature of about 200° C. for several minutes is sufficient.

Next, this superconducting material 5 is subjected to heat treatment. This heat treatment is performed by heating the superconducting material 5 at 700 to 1000°C for several minutes to several tens of hours in the air or oxygen atmosphere.
This is done by cooling to room temperature.

Through this heat treatment I, the 11 young layer 4 on the surface of the base material 1 is sintered, and B il S rl Cal Cut is applied to this portion.
A superconducting layer having a composition ox is formed. By each of the above operations, the base material is completed as shown in Fig. 3! A superconducting material 10 having a superconducting layer 7 formed on its surface is applied.

Then, on the surface of the superconducting material A thus obtained, a layer 8 as shown in FIG. 4 is formed as necessary. The material of this coating layer 8 is Ag, Cu, AI.
, Ni%Cu-Ni, or other metals, polyimide, polyurethane, polyester, amide-imide, polytetrafluoroethylene, or other synthetic resins, or amorphous carbon. In the superconducting material B shown in FIG. 4, the superconducting layer 7 is protected by the covering layer 8,
Deterioration of superconducting properties can be prevented over a long period of time, and peeling and cracking of the superconducting layer 7 can be prevented, resulting in even higher mechanical strength.

In the method for manufacturing superconducting material A described above, D I + S r + Car is deposited on the surface of the base material 1 by electrophoresis.
Since the oxide superconducting powder having the composition Cu t OX can be electrodeposited to form a dense electrodeposited layer 4, shrinkage due to subsequent heat treatment is small, and a dense superconducting layer 7 can be formed on the surface of the base material 1. can be formed. Therefore, a high-performance superconducting material A that exhibits a high critical current density (Jci) can be manufactured without causing defects such as cracks in the superconducting layer 7 due to shrinkage during firing.

In addition, in the above-mentioned superconducting material A, a dense electrodeposited layer 4 is formed on the surface of the base material I by electrophoretic electrodeposition, and then a heat treatment is performed to generate a superconducting layer 7. Superconducting material A that has good adhesion to material 1, has good flexibility, and has high mechanical strength can be manufactured.

Furthermore, since the electrodeposition layer 4 made of superconducting powder is formed on the surface of the base material 1 by electrophoretic electrodeposition, the thickness of the superconducting layer 7 can be controlled by controlling the electrodeposition conditions such as the applied voltage and electrodeposition time. can be precisely controlled to a desired value. Furthermore, electrophoretic electrodeposition can be used to Since J layer 4 is formed, 200
It is possible to form an electrodeposition layer 4 as thick as μ or more, for example, about 1II, in a short time, and the production efficiency of the superconducting material A can be increased by 14 times. Furthermore, if the electrodeposited layer 4 formed on the surface of the base material 1 is made sufficiently thick, unnecessary elements in the base material 1 will diffuse into the superconducting layer 7 during heat treatment.
Even if a phenomenon occurs in which the superconducting properties of the diffusion portion deteriorate, the ratio of the deteriorated portion to the total thickness of the superconducting layer 7 can be reduced, so that the superconducting material A8 can be manufactured with high performance as a whole.

In the previous example, a round wire-shaped base material 1 was used as the base material, but the shape of the base material is not limited to this, and may be plate-shaped, foil-shaped, columnar, ribbon-shaped, uneven parts, or holes. Substrates of various shapes can be used, including those with complex shapes. In addition, in the manufacturing method according to the present invention, since a dense electrodeposited layer 4 made of superconducting powder is formed on the surface of the substrate by electrophoretic electrodeposition, it has good throwing power and even if the surface of the substrate is uneven,
Electrodeposition Ji 14 having a uniform thickness is formed along this unevenness.

Furthermore, when a ceramic base material is used as the base material, RJ'IT can be performed by printing and applying a conductive paste using a screen printing method and sintering this instead of applying a metal coating to the surface of the ceramic base material. .

However, a ceramic base material whose surface is coated with conductive coating may also be used. Furthermore, conductive surface treatments such as Moeki metal coating and conductive coating are applied to the entire surface of the base material. For example, when creating circuit boards and electromagnetic shields,
A superconducting layer may be formed on the circuit pattern by subjecting only the conductive circuit portion to a conductive surface treatment using a normal masking method or the like.

By the way, when the superconducting material 5 is sintered, the base material can be burnt out or melted and flowed out, so that it can be applied to applications where only the conductor portion remains. Therefore, in this case, various molded products such as threads and sheets made of low melting point metals or polymers, which have been subjected to conductive surface treatment, may be used as the base material.

Next, the manufacturing method of the present invention is applied to B i-S r-Ca-Cu
-0 series long superconducting wire tJ? Suitable for method
I will explain about it.

FIG. 5 is a diagram showing an example of an electrophoresis device suitably used for manufacturing superconducting wires, and the reference numeral ! 1 is a wire rod used as a base material, and 12 is a fuTt tank.

Furthermore, this? Ilf tank! 2 contains an electrodeposition liquid 3 similar to that used in the previous example.

The wire 11 preferably used 1a in this temple is as follows:
Similar to the previous example, a composite consisting of a metal wire material made of a metal material with a melting point of 800°C or higher and good oxidation resistance, a ceramic fiber such as quartz glass, or sapphire with a metal wave crest made of Ag on the surface. Wire rods, carbon fibers, etc. are preferably used.

In this method for producing a superconducting material, an electrophoresis apparatus (not shown in FIG.
1 is used as a cathode, and a voltage is applied between this wire 11 and an anode 14 disposed in the if loading tank weight 2. The conditions for applying this voltage are the same as in the previous example, and the anode 14 is
A similar anode 6 can be used. In addition, since the concentration of the superconducting powder in the electrodeposition liquid 3 decreases as the electrodeposition operation progresses, the superconducting powder is directly added to the electrodeposition liquid 3 in the electrodeposition bath 12 as the electrodeposition operation progresses. Supply or predetermined concentration? It is preferable to supply Ii liquid 3.

? I! Once an electrodeposited layer of a predetermined thickness is formed in the deposited liquid 1z, the superconducting wire 13 is pulled out from the electrodeposition bath 12 14L,
Next, drying treatment with hot air is performed to remove N--N dimethylformamide remaining on the surface portion.

Next, this superconducting wire 13 is subjected to heat treatment. As in the previous example, this heat treatment was performed in an oxygen atmosphere at a temperature of 700 to
It is desirable to set the conditions to be heated at 1000° C. for several minutes to several 10 hours and then cooled to room temperature.

Note that during this heat treatment, a heating means capable of continuously heating and gradually cooling the super 71 conductive wire 13 moving at a predetermined speed, such as a long tunnel-shaped heating furnace, may be used; By combining a heating furnace with the above-mentioned 71i pneumatic migration apparatus, the wire rod 11 can be formed into hq without successively performing the electrophoretic electrodeposition → drying → heat treatment.

Through each of the treatments described in 1- below, B++Sr is added to the surface of the wire rod 11.
A long superconducting wire in which a dense superconducting layer having a composition of +Ca+CutOx is formed is manufactured. Note that a coating layer may be formed on the surface of the obtained superconducting wire as in the previous example.

The method for manufacturing a superconducting wire according to this example provides almost the same effect as the method for manufacturing a superconducting material according to the previous example, and also includes a series of operations in which a first layer is formed on the surface of the wire 11 and then heat treatment is performed. It is easy to carry out continuously, the production of long superconducting wires can be automated, and the production efficiency of superconducting wires can be improved.

In addition, in the above example, one electrophoresis m-deposition operation results in 1
Although a deposited layer has been formed, this electrophoretic electrodeposition operation may be repeated two or more times.

"Example I" B LOs powder, S rCOa powder, CaCO5 powder, and CuO powder are Bi:Sr:Ca:Cu= l:I :I
: 2 (molar ratio) to make a mixed powder, then this mixed powder is calcined in the atmosphere at 820°C for 24 hours to make a calcined powder, and then by a ball mill) After crushing, the average particle size G, 3u
A superconducting powder having a composition of 1311 S r+ Cal Cu*o y was prepared.

Next, 15 g of this superconducting powder was dispersed in 300 ml of N-N dimethyl;1:lumamide to prepare an electrodeposition liquid.

This 7I! 71 with the same structure as that shown in Fig. 1
A stainless steel plate (SUS304, thickness lI.

Insert the substrate (width 50s+i, length IOOff1s) and the cathode, apply a constant DC voltage of 10 to 500v to the stainless steel plate (anode) and the substrate (cathode), and perform electrophoretic electrodeposition for 2 minutes. I went 11g. In addition, the base material is Zr, 'ri, Ag
Commercial capital 1, Olta, length 5c made of each metal.
A round wire rod with a diameter of m was used. These substrates were subjected to ultrasonic cleaning in ethanol before use.

Subsequently, each substrate that had been subjected to Moeki electrophoresis 7i was subjected to 20
After drying with 1/l hot air for 5 minutes at 0℃,
It was heated at 0°C for 12 hours and slowly cooled to room temperature at -400°C/hour to obtain a Di-based superconducting wire.

Then, a plurality of superconducting materials having different base material types and processing voltages were created using the same procedure as described above, and the film thicknesses of these superconducting materials were measured using a microscope.

In addition, the critical temperature ('l'c) of these superconducting materials was measured using a four-terminal method. The results of these measurements are shown in Table 1.

As shown in Table 1, a superconducting layer exhibiting a high critical temperature could be formed on either the Zr or Ti%Ag base material. Furthermore, no peeling or cracking of the superconducting layer was observed in each superconducting material.

"Example 2" Using N-N dimethylformamide as a dispersion medium, the width is 1
0mm, length 2011, thickness 1mm stabilized zirconia (
ysz) substrate and strontium titanate Jl (plate), the surfaces of these substrates were pretreated with an aqueous solution of tin chloride and palladium chloride, and then electroless N1 plating was performed to a thickness of approximately 2μ.
After forming a conductive layer of m, electrophoretic electrodeposition and heat treatment were performed under the same conditions as in Example 1 to create superconducting materials with different base material types and processing voltages. Similarly, the film thickness and critical temperature ('rc) of these superconducting materials
was measured. The results of these measurements are shown in Table 2.

As shown in Table 2, a Bi-based superconducting layer exhibiting a high critical temperature could be formed on each of the base materials.

In addition, in each superconducting material, peeling and cracking of the superconducting layer (1 was not observed).

"Comparative Example" In order to compare with the method of the present invention, a superconducting material was manufactured using an organic solvent other than N-N dimethylformamide as a dispersion medium.

Electrophoretic electrodeposition was performed under the same conditions as in Example 1 using n-hexane, toluene, and xylene as dispersion media, and using the same base material as that used in Example 1 in these dispersion media. As a result, when normal hexane was used as the dispersion medium, no electrodeposited layer was formed on the surface of the substrate, and when toluene and xylene were used, a small amount of electrodeposited layer was formed on the surface of the substrate. Although it was formed, the adhesion to the base material was poor and it was not formed densely, so it peeled off when the base material was pulled up from the electrodeposition solution.

"Effects of the Invention" As explained above, in the method for producing a Bii oxide superconducting material according to the present invention, B is applied to the surface of the base material by electrophoretic electrodeposition.
ii) Oxide superconducting powder can be electrodeposited to form a dense electrodeposited layer, so there is less shrinkage due to subsequent heat treatment, and a dense i-based superconducting layer without cracks is formed on the substrate. [1] with a high critical temperature and excellent superconducting properties.
An i-based oxide superconducting material can be obtained.

In addition, a dense electrodeposited layer is formed on the surface of the base material by electrophoretic electrodeposition, and then heat treatment is performed to generate a sintered layer of Bii superconducting layer, so the superconducting layer has good adhesion to the base material. This makes it possible to produce a Bi-based superconducting material with excellent flexibility and high mechanical strength.

Furthermore, since the v&@ layer made of Bi-based superconducting powder is formed on the surface of the base material by electrophoretic electrodeposition, the thickness of the superconducting layer can be accurately controlled by controlling the Wi layer conditions.

In addition, since the electrodeposition layer is formed by electrophoretic electrodeposition, 2
A relatively thick electrodeposited layer having an amount of 00μ or more can be formed in a short time by electrodeposition, and the production efficiency of Bi-based superconducting material can be improved.

[Brief explanation of the drawing]

Figures 1 to 4 illustrate examples of the manufacturing method of the present invention.
□ Figure 1 is a schematic diagram of the electrophoresis device, Figure 2 is a cross-sectional view of the superconducting material, Figure 3 is a cross-sectional view of the superconducting material, and Figure 4 is shown in Figure 3. A cross-sectional view of a superconducting material showing an example of a superconducting material coated with a coating, and FIG. 5 is a schematic configuration diagram of an electrophoresis device suitably used for manufacturing a superconducting wire by the method for manufacturing an oxide superconducting material of the present invention. It is. ! ...Base material, 3... Electrodeposition liquid, 4... M18 layer, 5
... superconducting material, 6... anode, 7... superconducting layer,
A, r3... superconducting material! 1...Wire rod (base material), 1
3... Superconducting wire, 14... Anode.

Claims (1)

[Claims] In a method for producing an oxide superconducting material comprising a Bi-Sr-Ca-Cu-O-based oxide superconductor, the oxide superconductor powder or the oxide superconductor precursor powder is mixed with N-N dimethyl Electrophoretic electrodeposition is performed in an electrodeposition solution dispersed in formamide using a base material having conductivity at least on the surface as a cathode, and electrodeposition containing elements constituting an oxide superconductor is carried out on the surface of the base material. A method for producing a Bi-based oxide superconducting material, which comprises forming a layer and then subjecting it to heat treatment.