JPH0446051A - Oxide superconducting tape - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides B1-5r-Ca-Cu-
The present invention relates to a 0-based oxide superconducting tape.

[Prior art] Conventionally, Bi*5rxCa*Cu5 was added to a B1-5r-Ca-Cu-0 superconductor (hereinafter also referred to as a Bi-based superconductor).
Oy (hereinafter also referred to as 2223 phase), B1mSr*
CaCu50y (hereinafter also referred to as 2212 phase),
There are three types of structures: B1m5rtCuOy (hereinafter also referred to as 2201 phase), and the critical temperature of each is approximately ll0.
It is known that K, 90 and 20.

Research and development aimed at practical use at liquid nitrogen temperature (77K) is being conducted mainly on the 2223 and 2212 phases, which have high critical temperatures. As a method for manufacturing a Bi-based superconductor tape, there is a method in which a crystal powder having the above-mentioned composition is synthesized, and then this is sealed in a metal tube and sintered or melted and solidified.

[Problems to be solved by the invention] The cross section of the superconducting tape manufactured by the sintering method is
As shown in Figure 1, it is a porous polycrystalline body. Each crystal grain is arranged in a disordered direction, and the bonds between the grains are weak.

In a Bi-based superconductor, the direction in which current flows easily within the crystal grains is determined, so current has a property that it is difficult for current to flow between crystal grains having different orientations. Furthermore, a small bonding area between grains means that the effective current path is narrow. For this reason, polycrystalline B as shown in Figure 1
It has not been possible to obtain an i-based superconductor with a high critical current density.

When the direction of the crystal grains is controlled by pressing the polycrystal, the critical current density is improved because the directions of the crystal grains are aligned. Similarly, when manufactured by the melt solidification method, the critical current density is improved because the crystal grains grow larger, become denser, and the bonds between the grains become stronger.

When manufactured using any of these methods, the critical current density at liquid nitrogen temperature significantly decreases in a magnetic field. This is thought to be due to the weak binding force of the magnetic flux penetrating the crystal in a magnetic field higher than the lower critical magnetic field of the Bi-based superconductor.

The main field of application for superconductors is considered as electromagnets that create strong magnetic fields by processing wire or tape materials into coils. Therefore, in order to put Bi-based superconducting tape into practical use, it is necessary to create a structure in which the crystal directions are precisely aligned and to introduce a binding center into the crystal to strengthen the binding force. It is considered necessary to create materials with critical current densities.

Fine precipitates, grain boundaries, and various defects are considered to be the center of bottle fixation. For rare earth superconductors, REJaCuO
It is known that fine particles of the non-superconducting phase finely dispersed in the i-phase (RE is a rare earth element) baka crystal can become the center of the bottle. A Bi-based superconductor partially melts at a temperature of about 880° C. or higher, and when it is cooled, a 2201 phase crystal is formed in the initial stage of solidification, and when it is slowly cooled, it easily transforms into a 2212 phase. Bi-based superconductors do not have a non-superconducting phase such as the REJaCuOs phase that precipitates in the superconducting crystal, and there are no reports of introducing a superconductor and another non-superconducting substance into the crystal.

[Means for Solving the Problems] The present invention includes at least one metal selected from Group 2A elements and Group 4A and Group 4B elements in a crystal containing Bi, Sr, Ca, Cu, and 0 as constituent elements. An oxide superconducting tape characterized in that an oxide superconducting film having a structure in which granular crystals of a composite oxide with at least one metal selected from rare earth elements are dispersed in an island shape is laminated with a metal. It provides:

In the present invention, a composite oxide of one or more metals selected from group 2A elements and one or more metals selected from group 4A, group 4B, and rare earth elements is ABO.
s (^ is one or more selected from Mg, Ca, Sr, and Ba; B is one or more selected from Zr, Sn, Ce, and Ti). In this case, ABO3 becomes a crystal with a perovskite structure. Both of these crystals have a temperature of 1200°C in the atmosphere.
It is a substance that is compositionally stable up to temperatures of 880 to 900° C., which is the partial melting temperature of Bi-based superconductors, and does not react with the Bi-based superconductor melt, and hardly causes grain growth.

The superconductor of the present invention can be suitably manufactured by mixing the raw material of the Bi-based superconductor with the above-mentioned composite oxide, heating this to a temperature equal to or higher than the partial melting temperature of the superconducting phase, and then cooling and solidifying the mixture. . When a mixture of a superconducting phase and the above composite oxide is heated to a temperature higher than the partial melting temperature of the superconducting phase and then cooled and solidified, the above composite oxide crystals form a superconducting phase while maintaining the particle size added at the time of preparation. Incorporated into crystals.

At this time, if the above-mentioned composite oxide in which only fine particles are selected is used, a non-superconducting substance of the same size as the composite oxide can be dispersed in the superconducting phase crystal, which is desirable from the viewpoint of strengthening the bottle-holding force. When only particles of 0.5 μm or less are used, the critical current density increases dramatically and does not decrease much even when a magnetic field is applied.

When using ABOa, the amount added is 0.5wt%
It is preferably at least 20 wt%. Added amount is 0.5w
If the amount is less than t%, the effect of the present invention may not be fully expressed, and if the amount added exceeds 20wt%, the ABOa phase may segregate in a part of the material, causing discontinuity in the superconductor. I don't like it because it is. More preferable A
The amount of BO* added is 1 to 10 wt%.

The superconducting tape of the present invention is preferably manufactured in a state in which it is laminated to a metal plate that does not react with the superconductor melt, or in a metal tube pressed flat. In this case, when crystals grow from the melt, Because the crystals grow perpendicularly to the surface of the metal due to the surface tension of the melt, a superconducting tape with crystals aligned in the same direction can be obtained.

Preferred metals that do not react with the superconductor melt are gold, silver, or alloys containing these as main components.

The electrically conductive tape of the present invention can be produced by, for example, laminating green sheets containing raw material powder obtained by the doctor blade method on a metal plate and melting and solidifying them, or forming a film on a metal plate by screen printing or the like and melting and solidifying the sheets. It is manufactured by filling raw material powder into a metal tube, pressing the metal tube to form a tape, and melting and solidifying it.

[Example] Example I A calcined powder of an oxide with an atomic ratio of Bi:Sr:Ca:Cu of 2:2:l:2 was prepared (this is referred to as powder AB consisting of the combination of A and B shown
5 wt % of Os (average particle size: 0.5 μm) was added and mixed.

After mixing the powder with octyl alcohol, it was mixed with 0.
It was screen printed on a 1 mm x 10+ om x 50 mm silver plate and dried. This was melted at 890'C for 20 minutes, cooled to 870'C over 3 hours, slowly cooled to room temperature, further heated to 500°C, and held in an atmosphere with an oxygen partial pressure of 0.001 atm for 10 hours. It was rapidly cooled.

When the cross section of the coagulated tape thus obtained was observed using a scanning electron microscope and an X41 elemental analyzer, one plate-shaped crystal grain of the 2212 phase was observed as shown in Figure 2.
ABO particles with a particle size of about 0.5 μm are layered on top of each other.
It was confirmed that the s-particles had a structure in which they were dispersed in the form of islands. A good structure as described above was observed throughout the sample.

The measurement results of the superconducting properties are shown in Table 1. For these measurements, tapes cut into 2 mm widths were used. The critical temperature is the temperature at which zero resistance is shown when measured by the DC four-probe method, and the critical current density is the same at liquid nitrogen temperature with an external magnetic field of 2 Tesla applied (measured by the DC four-probe method. Magnetic field was applied parallel to the C axis of the superconducting crystal.

Table Example 2 A powder obtained by adding 5 wt% of 8BO1 (average particle size 0.5 μm) consisting of the combination of A and 8 shown in Table 2 to the powder X in Example 1 was mixed with a powder having an outer diameter of 4.6 mmφ, Inner diameter 3 @mφ,
After filling a chain pipe with a length of 100 am, the mixture was kneaded to have an outer diameter of 1.5 m@φ and pressed into a tape shape with a width of 3 mm and a thickness of 0.2 mm. After sealing both ends of the obtained tape with welding stones, it was melted at 890°C for 20 minutes and heated to 870°C.
The mixture was cooled for 3 hours until the temperature reached 300°C, and then slowly cooled to room temperature, further heated to 500°C, and kept in an atmosphere with an oxygen partial pressure of 0.001 atm for 10 hours for rapid cooling.

When the cross section of the coagulated tape thus obtained was observed using a scanning electron microscope and an X-ray elemental analyzer, the third
It was confirmed that the crystal grains of the plate-like 2212 phase overlapped in a layered manner as shown in the figure, and had a structure in which ABOs particles with a grain size of about 0.5 μm were dispersed in the form of islands. A good structure as described above was observed throughout the sample.

Table 2 shows the results of superconducting properties measured in the same manner as in Example 1.

Table 2 Example 3 To powder X in Example 1, 5 wt % of ABOI consisting of a combination of A and 8 shown in Table 3, selected to have an average particle size of 0.15 μm, was added and mixed. After mixing the powder with octyl alcohol, it was divided into 0.1 mm x 10 + wm x 5
Screen printed on a 0++m silver plate and dried. This is 8
The mixture was melted at 90° C. for 20 minutes, cooled to 870° C. over 3 hours, slowly cooled to room temperature, further heated to 500°C, and kept in an atmosphere with an oxygen partial pressure of 0.001 atm for 10 hours for rapid cooling.

The cross section of the coagulated tape thus obtained was observed using a scanning electron microscope and an X-ray elemental analyzer.
As shown in the figure, the plate-shaped 2212 phase crystal grains overlap in a layered manner, and ABOs with a grain size of about 0.15 μm are contained within them.
It was confirmed that the particles had a structure in which they were dispersed in the form of islands. A good structure as described above was observed throughout the sample.

Table 3 shows the superconducting properties measured in the same manner as in Example 1.

Table Comparative Example 1 Powder X in Example 1 was mixed with octyl alcohol, then screen printed on a 0.1 aw x 10 mm x 50 mm gold plate and dried. This was melted at 890°C for 20 minutes, cooled to S70'C over 3 hours, slowly cooled to room temperature, heated roughly to 500'C, and brought to an oxygen partial pressure of 0.
The sample was kept in an atmosphere of 0.001 atm for 10 hours and rapidly cooled.

The cross section of the coagulated tape thus obtained was observed using a scanning electron microscope and an X-ray elemental analyzer.
It was confirmed that the sample had a structure in which plate-shaped 2212 phase crystal grains overlapped in layers as shown in the figure. The above-mentioned structure was observed throughout the sample.

When measured in the same manner as in Example 1, the critical temperature was 89, and the critical current density at liquid nitrogen temperature was 120 A/cm.
"Met.

Comparative Example 2 Powder X in Example 1 had an outer diameter of 4.6 mmφ and an inner diameter of 3 mmφ
After filling a brass tube with a length of 100 mm, it was threaded to have an outer diameter of 1.511+mφ and pressed into a tape shape with a width of 3 layers and a thickness of 0.2 mm. This was heated to 890℃ for 2
After melting for 0 minutes and cooling to 870°C over 3 hours, slowly cooling to room temperature, further heating to 500°C, and oxygen partial pressure 0.00.
The mixture was kept in an atmosphere of 1 atm for 10 hours and rapidly cooled.

When the cross section of the coagulated tape thus obtained was observed using a scanning electron microscope and an X-ray elemental analyzer, it was found that
It was confirmed that the sample had a structure in which plate-shaped 2212 phase crystal grains overlapped in layers as shown in the figure. The above-mentioned structure was observed throughout the sample.

When measured in the same manner as in Example 1, the critical temperature was 87, and the critical current density at liquid nitrogen temperature was 90 A/c.

[Effects of the Invention] The superconducting tape of the present invention has very fine non-superconducting particles dispersed therein, which act as centers for good binding of magnetic flux, so that the critical current density is high even in a strong magnetic field.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the structure of a Bi-based superconducting tape manufactured by a sintering method. FIG. 2 is a schematic diagram showing the structure of the superconducting tapes obtained in Examples 1 and 3. FIG. 2 is a schematic diagram showing the structure of the superconducting tape obtained in Example 2. FIG. 4 is a schematic diagram showing the structure of the superconducting tape obtained in Comparative Example 1. FIG. 5 is a schematic diagram showing the structure of the superconducting tape obtained in Comparative Example 2. Diagram 1 Hand thread sales book (method) % formula % 1 Display of the case 1990 Patent Application No. 151604 2 Name of the invention Suronide superconducting tape 3 Person making the amendment Relationship to the case Patent applicant residence Location 2-1-2 Marunouchi, Chiyoda-ku, Tokyo Name
(004) Asahi Glass Co., Ltd. August 28, 1990 (Delivery) 6. Number of claims increased by 710 due to amendment 7, Column 8 for brief explanation of drawings in the specification subject to amendment, Contents of amendment (1) ) The omission of "Figure 2" on page 15, line 15 of the specification is corrected to "Figure 3."

Claims (3)

[Claims] 1. At least one metal selected from Group 2A elements and at least one metal selected from Group 4A, Group 4B, and rare earth elements in a crystal containing Bi, Sr, Ca, Cu, and O as constituent elements. 1. An oxide superconducting tape characterized in that an oxide superconducting film having a structure in which granular crystals of a composite oxide with a metal are laminated with a metal. 2. A composite oxide of at least one metal selected from group 2A elements and at least one metal selected from group 4A, group 4B, and rare earth elements is ABO_3 (A is Mg, Ca, Sr, One or more types selected from Ba, B is Z
2. The oxide superconducting tape according to claim 1, wherein the oxide superconducting tape is one or more selected from r, Sn, Ce, and Ti. 3. The oxide superconducting tape according to claim 1 or 2, wherein the crystals containing Bi, Sr, Ca, Cu, and O are obtained by solidifying a melt.