JPH01239026A - Production of oxide superconducting form - Google Patents

Abstract

PURPOSE:To obtain the title high-density form of high critical current density, by covering a specific composite oxide melt around a core to make a shaping followed by cooling and then heat treatment. CONSTITUTION:Firstly, a Bi-alkali metal-Cu-O-based composite oxide with the composition range capable of obtaining vitreous phase [e.g., Bi(Sr,Ca)xCuyOz (x is 1-4; y is 1-4; z is 1-10); Ca/(Sr+Ca)=0.2-3] is heated to 900-1,300 deg.C in an electric furnace 10 and melted to produce a composite oxide melt 12. Second, this melt 12 is covered around a core 9 followed by feeding a cooling glass 14 to quench the covered core at a rate of >=100 deg.C/sec to obtain a composite wire 13 with oxide melt layer converted into amorphous phase. Thence, this composite wire 13 is heat treated at 390-890 deg.C, thus obtaining the objective superconducting form.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is directed to a Bi-alkaline earth metal-Cu-0 based oxide superconducting molded body having high density and a high critical current density (JC) value. This relates to a manufacturing method.

(Prior art) Recently, as an oxide superconductor with a higher critical temperature (Tc) than the conventional Y-Ba-C, u-○ system oxide superconductor,
A Bi-alkaline earth metal-Cu-0 based oxide superconductor has been discovered and is attracting attention.

That is, the oxidation of this Bi-alkaline earth metal-Cu-0 system
! The yJ superconductor has the following characteristics: (1) The low field temperature (T, ) is around 105 and the conventional Y-
It is nearly 15 degrees higher than the B a -Cu -0-based oxide superconductor.

(2) It is more stable than the Y-B a -Cu-0-based oxide superconductor, and is resistant to water (and does not easily escape oxygen).

(3) Raw material costs are low because rare earth elements are not required.

It has the following advantages, and its practical application is expected.

Conventionally, YX
Using oxides and carbonates of metals such as Ba and Cu as raw materials,
A mixture of these secondary raw material powders is temporarily sintered to form a composite oxide, which is pulverized to form the resulting secondary raw material powder into a desired shape and sintered.

In addition, to make a superconducting wire, oxide powder material to become a superconductor is filled into a metal tube made of silver, silver alloy, copper alloy, etc., and then it is processed by wire drawing, swaging, grooved rolls, flat rolls, etc. The wire or thin plate is cold-worked into a wire of desired dimensions, and then heat-treated to form an oxide-based superconducting wire.

Still other methods include kneading oxide powder and a binder to form a paste, and then forming the paste into a wire by extrusion processing, or coating the outer periphery of a core material and then removing the paste. A method such as 0, which involves heat treatment containing a binder, has been tried as the most effective method.

[Problem to be solved by the invention]

However, in these methods, since oxide powder is used as the material that becomes the superconducting compact, even if processing is performed with a high area reduction rate, the density of the superconducting compact after heat treatment is not the same as its true density. There is a problem that a value close to the density cannot be obtained, and therefore the critical current density (J,) of the obtained superconducting compact is low.
The same was true for the Bi-alkaline earth metal-Cu-0 based oxide superconductor.

[Means for Solving the Problems] The present invention has been made as a result of intensive studies in view of the above points, and its purpose is to achieve a high density and high value of n-field current density (J,). Bi-alkaline earth metal-C
An object of the present invention is to provide a method for producing a u-0-based oxide superconductor.

That is, the present invention provides Bi within a composition range in which a glassy phase is obtained.
1. After heating and melting a composite oxide composed of an alkaline earth metal, a metal element of Cu, and oxygen, the composite oxide molten material is applied directly or by coating around a desired core material. After cooling the oxide melt layer to an amorphous phase by cooling at a cooling rate of 10''C/sec or more, the obtained molded body is cooled within a temperature range of 390 to 890'C. It is characterized by heat treatment.

In the present invention, a material powder, etc. that becomes a Bi-alkaline earth metal-Cu-0 based oxide superconductor is used in a composition range that allows a glassy phase to be obtained, and after being melted, it is rapidly solidified. The purpose is to obtain a high-density and homogeneous i-alkaline earth metal-Cu-0 based oxide superconducting molded body by making it into an amorphous phase and then heat-treating it. By using the material powder in a composition range that turns it into a glassy phase, when heated to a high temperature and melted, the composite oxide melt can be formed into a filament, etc. within a relatively wide temperature range. The aim is to obtain a viscosity suitable for

In the present invention, Bi within a composition range in which a glassy phase is obtained.
-Alkaline earth metal-Cu-0-based oxides include, for example, when Bi=1, Bi(Sr, ca) xc
u yoz (however, x = 1 to 4, y = 1 to 4, z
= 1~10, Ca/(Sr+Ca)=0.2~3)
A complex oxide represented by can be used.

If the temperature range for heating and melting the composite oxide in the above composition range is less than 900°C, the resulting composite oxide melt will have too high a viscosity and poor moldability, and if it exceeds 1300°C, the viscosity will become low. If the temperature is too high, the moldability will deteriorate and the life of the crucible for melting will also be shortened.
Preferably, it is heated to a temperature range of 00°C.

In addition, the cooling rate when solidifying the composite oxide melt is 10
If it is less than 2° (:/sec, there will be no segregation and a sufficiently homogeneous amorphous phase will not be obtained.
It is desirable to cool at a cooling rate higher than that of SeC.

Moreover, Bi-alkaline earth metal-Cu obtained in this way
The temperature range when heat-treating the amorphous phase of the -0-based composite oxide is that if it is less than 390°C, crystallization will not occur and it will not become a superconductor, and if it exceeds 890°C, the amorphous phase will melt. is likely to occur, so 390-89
It is desirable that the temperature be within the temperature range of 0°C.

Next, embodiments of the present invention will be specifically described with reference to the drawings.

First, a mixture of primary raw materials such as BizOz, 5rCO, CaCO3, and CuO is calcined to form a composite oxide, and then the composite oxide is heated in an electric furnace, high-frequency induction heating furnace, infrared heating furnace, etc. After heating and melting, the resulting melt is rapidly cooled.

When trying to obtain a composite oxide bulk, for example, as shown in FIG. 1, a composite oxide melt 2 is rapidly cooled between two metal plates 1 to obtain a composite oxide bulk 3. Alternatively, a method such as pouring a composite oxide melt into a mold can be used.

In addition, when trying to obtain a relatively long striatum, the method shown in Figure 2 (
A single roll method or a twin roll method as shown in a) or (b) can be used. That is, in FIG. 2(a), the composite oxide@fJ melt 4 heated in the electric furnace 5 falls onto one rotating roll 6 and is rapidly cooled to become the composite oxide filament 8. . Further, in FIG. 2(b), the composite oxide melt 4 falls between the rotating L string rolls 6A and 6B and is rapidly cooled to become a composite oxide filament 8.

At this time, the crucible for melting the raw materials that will become the superconductor is a basic crucible that does not react with these raw material powders,
For example, it is desirable to use magnesia (MgO), calcia (Cab), stabilized zirconia (ZrO□+y20.), or the like.

Figure 3 shows a composite oxide melt placed around a core material in an electric furnace 1.
After the composite oxide melt 12 heated by 0 is coated around the core material 9, it is rapidly cooled by the cooling gas 14,
A composite wire 13 is obtained.

At this time, the core material 9 is, for example, Cu, Cu alloy, S
US, Ti, Ni, PT, and PT gold alloys can be used.

[Effect]

In the method of the present invention, B1, alkaline earth metal, Cu
After melting the raw materials including the above in a composition range that allows a glassy phase to be obtained, this is then cooled and solidified to form an amorphous phase, and then heat-treated to crystallize it to produce an oxide superconducting molded body. Therefore, the obtained oxide superconducting molded body is homogeneous and has improved density, and is a B1-alkaline earth metal-Cu-0 based oxide superconducting wire body with a large critical current density (J). can be obtained.

[Example 1] Next, the present invention will be explained in more detail with reference to Examples. l1
3+zot, S r C (L, CaC0,, CuO,
Bi:Sr:Ca:Cu=4:2:2:6 (molar ratio)
After weighing and mixing so that
It was pre-fired. After heating and melting this in an electric furnace,
As shown in FIG. 1, it was placed between two copper plates (plates 1 to 10 mm thick), cooled, and formed into a desired shape to obtain a composite oxide pellet. The crucible used to melt the composite oxide was made of MgO, and the melting temperature was 1100'C. Also, the two photos above! The thickness of the resulting pellet was adjusted by changing the temperature of the RL plate. Each of the pellets obtained above was heat-treated at 870°C for 6 hours in the atmosphere.
Tc), superconducting properties such as critical current density (Je) at M body nitrogen temperature (77 K) were measured. These results are shown in Table 1.

As is clear from Table 1, oxide-based superconducting molded bodies with high critical current density (JC) and high critical temperature (T c ) were obtained in Inventive Measurements 1 to 3 produced by the inventive method. There is. On the other hand, Comparative Measurement 1, in which the cooling rate of the oxide melt was too slow, could only obtain a low critical current density (JC) value.

(Example 2) A composite oxide melt prepared in the same manner as in Example 1 was heated to an outer diameter of 150 mmφ by the method shown in FIG. 2(a).
Using a copper roll, it was cooled and formed into a tape. At this time, the thickness of the obtained tape was adjusted by changing the peripheral speed of the copper roll. Thereafter, these were subjected to the same heat treatment as in Example 1, and then the superconducting properties as in Example 1 were measured. These results are shown in Table 2. For comparison, the calcined powder obtained in the same manner as in Example 1 was used as it was with an outer diameter of 10
The superconducting properties were also measured when the pellets were molded into mmφ and 1 mm thick and subjected to similar heat treatment, and the results are also listed in Table 2.

As is clear from Table 2, the tapes of the present invention height measurements 4 and 5 manufactured by the method of the present invention have a high critical current density (J, ) and a high critical temperature (TC), and are tape-shaped B1-3.
An r-Ca-Cu-0 based oxide superconductor has been obtained. On the other hand, the pellet of Comparative Height Measurement 2 in which the raw material powder was not heated and melted obtained only a low value of critical current density (J,).

(Example 3) A molten composite oxide prepared in the same manner as in Example 1 was rapidly cooled using a pair of steel rolls with an outer diameter of 50 mm in the method shown in FIG. It was formed into a shape.

At this time, the thickness of the obtained tape was adjusted by changing the circumferential speed of the F roll. Thereafter, these were subjected to the same heat treatment as in Example 1, and then the superconducting properties as in Example 1 were measured. These results are shown in Table 3.

As is clear from Table 3, the tapes No. 6 to 8 of the present invention manufactured by the method of the present invention have a high critical current density (Jc) and a high critical temperature (T).
-Cu -0 based oxide superconducting tape has been obtained.

[Example 4] The same calcined powder as in Example 1 was heated and melted in the same manner as in Example 3 by the method shown in FIG. 2(b), and then rapidly cooled and formed into a tape shape. After the molded bodies were heat treated at various heat treatment temperatures, superconducting properties such as field temperature (Tc) and field current density (J, ) at liquid nitrogen temperature (77°K) were measured.

These results are shown in Table 4.

Table 4 As is clear from Table 4, the tapes of the height measurements 1 to 3 of the present invention manufactured by the method of the present invention have a high critical current density (JC) and a high critical temperature (T c ). -C
An a-Cu-0 based oxide superconducting tape has been obtained. On the other hand, the tape of Comparative Example Hole 1, in which the heat treatment temperature was too low, did not crystallize during heat treatment, and the temperature of liquid nitrogen (7
In the case of the comparative example hole 2 tape in which a superconducting state could not be obtained even after cooling to 7 K) and the heat treatment temperature was too high, part of the material melted during heat treatment, and only a low common field current density (JC) value was obtained. I couldn't.

(Example 5) Biz○□, 5rCO*, CaCO2, CuO, Bi
:Sr:Ca:Cu=4:2:2:6 (molar ratio) after weighing and mixing, and then pre-calcining in the atmosphere at 850°C for 8 hours. After heating and melting this in an electric furnace, it was coated around various core materials (outer diameter 0.3 mmφ) by the method shown in FIG. 3, and then cooled to produce various composite wires. The crucible used was made of MgO.

These were subjected to heat treatment in the atmosphere to form superconducting composite wires, and then superconducting properties such as critical temperature (Tc) and critical current density (JC) at liquid nitrogen temperature (77K) were measured.

Regarding these, the manufacturing conditions of the superconducting composite wire are shown in Table 5, and the superconducting properties of the superconducting composite wire are shown in Table 6.

Table 6 Table 6 (Continued) As is clear from Table 6, the present invention height measurement 1-12 manufactured by the present invention method has a large field current density (JC) and a critical temperature (T). is also high Bi-S r -Ca -
A Cu-0 based oxide superconducting composite wire has been obtained.

- In the method shown in Fig. 3, Comparative height measurement 1 in which the temperature of the oxide melt was too low resulted in uneven coating of the oxide superconductor, making it impossible to obtain a sound composite wire; Comparative height measurement 2 (without gas cooling), in which the cooling rate of the l-volume melt was too slow, could not obtain a low critical current density (Jc)L. Furthermore, Comparative Measurement 3, in which the heat treatment temperature was low, did not crystallize during heat treatment, and a superconducting state could not be obtained even when cooled to liquid nitrogen temperature (77K), and Comparative Measurement 3, in which the heat treatment temperature was too high, For High 4, the material partially melted during heat treatment, and only a low value of νn critical current density Jc) was obtained.

〔Effect of the invention〕

According to the method of the invention, at high density, critical current density (J,
) It is possible to obtain a Bi-alkaline earth metal-Cu-〇-based oxide superconducting molded body, which brings about remarkable industrial effects.

[Brief explanation of the drawing]

FIG. 1, FIG. 2(a), (b), and FIG. 3 are explanatory diagrams showing an example of the method for manufacturing an oxide-based superconducting molded body according to the present invention. 1- Metal plate, 2- Oxide/8 melt, 3- Oxide bulk, 4- Oxide melt, 5- Electric furnace, 6.6A, 6B- Roll, 7- Crucible, 8- Oxide wire Strip, 9-core material, 10
-・Electric furnace, 11-~heater, 12-oxide melt,
13--Composite wire, 14-Cooling gas, 15 Crucible. Patent applicant Furukawa Electric Co., Ltd. Figure 1 Figure 2

Claims (1)

[Claims] After heating and melting a composite oxide composed of Bi, alkaline earth metal, Cu metal elements and oxygen in a composition range that provides a glassy phase, the composite oxide melt is directly or The core material is coated and shaped, and then cooled at a cooling rate of 10^2°C/sec or more to turn the oxide melt layer into an amorphous phase. A method for producing an oxide-based superconducting molded body, characterized by heat treatment within a temperature range of 890°C.