JPH0313582A - Production of oxide superconducting wire and tape - Google Patents

Abstract

PURPOSE:To easily produce an oxide superconducting wire excellent in superconductivity by appropriately mixing Y, etc., and the carbonate, etc., of Ba and Cu, adding specified amts. of citric acid and ammonia to dissolve the materials, heating and concentrating the soln., spinning the concd. soln. and heat-treating the product. CONSTITUTION:When the wire and tape of an oxide superconductor shown by the general formula M1Ba2Cu3O7-x (M is Y or rare earth elements and x=0-1.0) is produced, the carbonate or alkoxides are used as the raw materials for the M, Ba and Cu components. The raw materials are mixed in the ratio to obtain the composition, and >=0.8mols of aq. citric acid, based on the total mols of the metals, is further added to dissolve the materials. Aq. ammonia is then added to the soln. to obtain a transparent and uniform soln. The soln. is heated at 90-100 deg.C and concentrated, the concd. soln. is spun in the atmosphere, and the product is dried and then heat-treated. In the heat treatment, the product is gradually heated to 950 deg.C, held at that temp. for several hours, cooled to 300-400 deg.C, held at that temp. for 10-20hr, and then quenched to room temp. The superconducting wire and tape are easily obtained by this method.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing an oxide superconducting wire and a tape-shaped body. More specifically, this invention
The present invention relates to a method for manufacturing oxide superconductor wire and tape-shaped bodies useful for electric wires, coils, electronic materials, etc.

(Prior Art) Many methods for manufacturing wire rods and tape-shaped bodies made of oxide superconductors have been known.

For example, raw material powder mixed to form an oxide superconductor is compressed and inserted into a metal pipe, drawn or rolled to a desired thickness, and then heat treated to transform the raw material powder into an oxide superconductor. As a superconductor.

A known method is to produce a wire rod or tape-like body as a multifilamentary wire structure by directly covering the wires as they are, or by bundling several to tens of wires together, covering them with metal, and then drawing or rolling them.

In addition, using the suspension spinning method, superconducting oxide powder is dispersed with a dispersant in a PVA aqueous or PVA non-aqueous solution, and then spun into a PVA coagulation solution and heat treated to produce oxide superconducting wire. There are also known methods.

In addition to these methods, there is also a method called melt spinning, in which an oxide or alloy with a superconducting composition is melted, extruded through a nozzle, rapidly solidified, formed into a wire or tape shape, and then heat treated to form a superconducting wire or tape. There is also a method of manufacturing the body, called the sol-gel method, which uses acetate containing a superconducting metal as a raw material, and heats this aqueous solution at 60 to 80°C.
After heating and concentrating to make a viscous spinning solution and spinning this,
Furthermore, after growing a superconducting precursor phase from the gas phase on a tape-shaped substrate by CVD (chemical vapor deposition), PVD (physical vapor deposition), etc., heat treatment is performed to produce a superconducting tape-shaped body. There are also known methods.

(Problems to be Solved by the Invention) However, the reality is that each of these conventional methods has its own drawbacks.

In the case of the method of inserting the raw material powder of oxide superconductor into a metal pipe, the thinner the wire, the more drawing processes are required, and the greater the degree of drawing, the more the inside of the sheath. The drawback is that cracks occur in the material, impairing superconductivity, and making it difficult to manufacture thin products.

In the case of suspension spinning, it has been difficult to obtain uniform superconductivity through uniform dispersion because the particle size of the superconducting oxide powder to be dispersed and the dispersion method thereof have a large influence on superconductivity. In addition to this, during spinning, nozzles were easily clogged, and there was a limit to the thickness of the fibers that could be formed.

Furthermore, in the case of melt spinning, it is actually extremely difficult to produce long fibrous or tape-like superconducting materials.

In the case of the sol-gel method, the viscosity of the resulting spinning solution is low, making it difficult to solidify into fibers.
There was a problem in that it was impossible to increase the viscosity because the spinning solution would become non-uniform in composition. For this reason, there is no choice but to use a batch method, which has the disadvantage of reducing productivity. Furthermore, adjusting the final composition directly results in non-uniformity of the composition, making it difficult to manufacture a superconductor with a uniform composition.

Furthermore, in the case of manufacturing methods such as CVD and PVD, special equipment such as a vacuum device, a plasma generator, and a raw material heating device are required, and the productivity thereof is low.

This invention was made in view of the above circumstances, and it eliminates the drawbacks of the conventional method, makes it easy to appropriately adjust the viscosity of the spinning dope, and improves the spinnability, uniformity, and stability. The object of the present invention is to provide a new method for producing a superconducting wire and a tape-shaped body, which can have excellent spinnability and are easy to manufacture.

(Means for Solving the Problems) In order to solve the above problems, the present invention solves the above problems by using the general formula M
1B a 2 Cu s O7-t (However, M represents an element selected from Y or rare earth elements, and x = 0 ~
It is 1.0. ) In producing wire rods and tape-shaped bodies of oxide superconductors shown in Add a citric acid aqueous solution of 0.8 times the mole or more to the total molar amount of metals to dissolve these raw materials, then add ammonia water to make a transparent uniform solution, heat and concentrate, and spin. The present invention provides a method for producing an oxide superconducting wire and a tape-shaped body, which is characterized by heat treatment.

In the method for producing a superconducting wire and tape-shaped body of the present invention, M component, Ba component, and C
Use the carbonate or alkoxide of component u. When the carbonate of this component is mixed with citric acid, it easily reacts with C.
02 is released, resulting in a transparent homogeneous solution. Similarly, the alkoxide of the component readily reacts with citric acid to form a clear homogeneous solution. There are no particular restrictions on the alkoxides that can be used as raw materials for each component, and examples include methoxide, ethoxide, and improoxide. Furthermore, the carbonates and alkoxides of the M component, Ba component, and Cu component can be combined as appropriate, and in this case as well, they easily react with citric acid to form a transparent and uniform solution. Any of these solutions can be converted into an oxide by firing.

When a citric acid aqueous solution is added to and dissolved in such raw materials, the amount of citric acid should be 0.8 times or more in mole or more relative to the total molar amount of the metals of the M component, Ba component, and Cu component. is important. Although there are no particular limitations on the citric acid aqueous solution, it is preferable to use water in an amount of about 20 to 50 times the total number of moles of the M component, Ba component, and Cu component.

In addition, one feature of this invention is that after the raw material for the oxide superconductor is dissolved in the citric acid aqueous solution, an ammonia aqueous solution is added until the initially dark blue solution changes from dark blue to deep purple. . This is because when dissolved metal ions and citric acid form a stable complex, their quantitative relationship is effective, and it is thought that the ammonia added functions effectively. The amount of citric acid is M component, Ba component and Cu
If the amount is less than 0.8 times the total molar amount of the component metals, if ammonia water is not added, or if the amount of ammonia water added is small, precipitation may occur during concentration or the solution may become non-uniform. This tends to cause the resulting solution to become a non-uniform paste with poor spinnability, making it impossible to form it into a fiber.

The transparent homogeneous solution was heated to 90-100°C until the viscosity was 1.
When concentrated to about 100 voids, it becomes a viscous liquid with stringiness. This viscous liquid tends to solidify as the temperature decreases, and because it solidifies easily in a dry atmosphere, when spinning, use a solution that has been heated and concentrated to 90 to 100°C, and in a dry atmosphere. When spinning, which is preferably carried out, a nozzle is used, a wire rod such as a long fiber can be obtained, and when extruded through a slit, a tape-like object can be obtained.

The obtained wire rod and tape-shaped body are then placed in a dryer to sufficiently remove moisture and ammonia, and then gradually heated in air and fired at 950° C. for several hours. If the removal of moisture and ammonia is insufficient or the rate of temperature increase is high, intense foaming will occur during the evaporation of moisture and ammonia and the decomposition and evaporation of organic matter and ammonia, which will not only impair the density of the baked product, but also Unable to maintain shape.

After firing, the temperature is lowered and held at 300 to 400°C for about 10 to 20 hours, and then rapidly cooled to room temperature. in this way,
The purpose of temperature holding treatment is to increase the amount of oxygen in the crystal structure, and the subsequent rapid cooling to room temperature is to suppress reactions with carbon dioxide, moisture, etc. in the air. If this heat treatment operation is not performed, sufficient superconducting properties cannot be obtained.

(Function) In the method for producing oxide superconducting wires and tape-shaped bodies of the present invention, carbonates or alkoxides of each component are used as raw materials to be added to the superconducting composition, and these raw materials are dissolved in an aqueous citric acid solution. By adding aqueous ammonia, the viscosity of the spinning stock solution can be controlled to an appropriate value, and a spinning stock solution with uniform properties can be easily obtained.

(Example) Hereinafter, the manufacturing method of the superconducting wire and the tape-shaped body of the present invention will be explained in more detail with reference to Examples.

Yttrium was chosen as M in the oxide superconductor shown in the one-shell type M (Ba2CusO7-1m).

A citric acid aqueous solution in which 78.8 f of citric acid was dissolved in 150 ml of distilled water was added with 19.7 f of barium carbonate and 17.8 f of carbonated steel.
9. and yttrium carbonate 11.2. was stirred for about half a day to obtain a dark blue, transparent, homogeneous solution.Next, 5'Oml of aqueous ammonia was gradually added to this solution to prepare a dark blue, transparent, homogeneous solution. All these operations were performed at room temperature.

The solution was heated to 100° C. and concentrated until the viscosity reached 50 voices. The concentrated solution was dark blue, transparent, and had a uniform consistency. This was allowed to cool and the viscosity was gradually increased to obtain a spinning dope having good spinnability.

Thereafter, the solution in a moderately viscous state was extruded through a nozzle at room temperature into a dry atmosphere and formed into dark blue transparent long fibers with a diameter of 5 to 100 μm. 100% of the obtained long fibers
After drying at ℃ for about 2 weeks, the temperature was raised from room temperature to 950 ℃ at a heating rate of 10''C/hr and held at that temperature for 5 hours.Then, it was heated to 400℃ at a rate of 20''C/hr. The temperature was lowered to room temperature, maintained for 10 hours, and rapidly cooled to room temperature.

The obtained wire rod was black in color and had a diameter of 3 to 50 μm. The critical temperature (Tc (zero)) of this wire is 85, and the critical current density (J
c) was 5A/-.

It was confirmed that the wire was an yttrium-based superconducting wire with good superconductivity.

Also, when the nozzle was changed to a slit under similar conditions,
A tape-shaped body with good superconducting properties was manufactured.

Even if M is replaced with Nb, Gd, or Yb, an oxide superconducting wire can be manufactured under the same conditions as in the above-mentioned example using yttrium.

Of course, this invention is not limited to the above examples, but includes the types of raw materials including 0M components, viscosity, temperature rise,
It goes without saying that various aspects are possible regarding details such as the rate of temperature decrease.

(Effects of the Invention) As explained in detail above, the present invention makes it easy to adjust the viscosity of the spinning dope to an appropriate level when producing oxide superconducting wires and tape-shaped bodies, and improves the spinnability and A spinning dope with excellent uniformity and stability and good spinnability can be obtained. Therefore, manufacturing of the superconducting wire and the tape-like body becomes easy. Further, since the wire rod and tape-shaped body obtained by this invention have good superconducting properties, they are effective in manufacturing coils and cables for superconducting magnets.

Claims (4)

[Claims] (1) General formula M_1Ba_2Cu_4O_7_-_x
(However, M represents an element selected from Y or a rare earth element, and x = 0 to 1.0.) In manufacturing the wire and tape-shaped body of the oxide superconductor,
As a raw material for the M component, Ba component, and Cu component, carbonate or alkoxide of the component is used, and the amount of citric acid aqueous solution is 0.8 times the mole or more based on the total molar amount of the metal of each raw material blended in the above composition ratio. and dissolve those raw materials,
A method for producing an oxide superconducting wire and a tape-shaped body, which comprises adding aqueous ammonia to obtain a transparent and uniform solution, followed by heating and concentration, spinning and heat treatment. (2) M is Y, Nd, Sm, Eu, Gd, Dy, Ho
, Er, Tm, Yb, or Lu. The method for producing an oxide superconducting wire and tape-shaped body according to claim 1. (3) The method for producing an oxide superconducting wire and tape-shaped body according to (1), wherein the oxide superconducting wire and tape-shaped body are heated and concentrated at 90 to 100°C and then spun in a dry atmosphere. (4) After spinning, it is dried, the temperature is gradually raised to 950°C, held for several hours, the temperature is lowered to 300 to 400°C, held for 10 to 20 hours, and then rapidly cooled to room temperature. The method for producing the oxide superconducting wire and tape-shaped body described above.