JPH01258832A - Superconductor - Google Patents

Abstract

PURPOSE:To increase the current capacity of the oxide superconductor contg. Bi, Sr, Ca, and Cu at specific atomic ratios or Tl, Ba, Ca, and Cu at specific atomic ratios and to increase the critical current density thereof by packing the above-mentioned superconductor into a metal pipe and rolling the pipe to a laminar state of a specific thickness. CONSTITUTION:Powder 2 of the oxide superconductor is packed into the metal pipe 1 and both ends thereof are sealed. The oxide superconductor contains the Bi, Sr, Ca, and Cu at 2:2:1:2 or 2:2:2:3 by atomic ratios or the Tl, Ba, Ca, and Cu at 2:2:1:2 or 2:2:2:3 by atomic ratios. The oxide superconductor 2 is rolled together with the metal pipe 1 to the laminar state of <=100mum thickness. The plural metal pipes packed with the powder are housed in a common metal pipe and are rolled. The current capacity of the superconductor is thereby increased and the critical current density thereof is increased.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Application Field) The present invention provides B1-8r-Ca-Cu-0 system or Ti
-Regarding a superconductor using Ba-Ca-Cu-0 based oxide superconductor powder.

(Prior art) Since it was announced in recent years that La-Ba-Cu-0 layered perovskite oxides may have a high critical temperature, research on oxide superconductors has been carried out in various places. (Z, Phys, B Condensed Ma
tter 64°189-193 (1986)). Among them, defective perovskite-type oxide superconductors with oxygen defects, represented by the Y-Ba-Cu-0 system, have been confirmed to have a critical temperature T of 90 or higher, which is higher than liquid nitrogen. (Phys, Rev, Lett,
vol, 5B No. 9.908-910).

Furthermore, recently, B1-8r-Ca whose critical temperature is 105
-Cu-θ system and TJ2-Ba-Ca-Cu-0 system oxide superconductors have been discovered.

These old -8r-Ca-Cu-0 series and Ti -Ba-
Ca-Cu-0 based oxide superconductor is La-Ba-C
Compared to u-0 series and Y-Ba-Cu-0 series oxide superconductors, it not only has a higher critical temperature, but also does not require expensive rare earth elements, and has high chemical stability against moisture. It has the following advantages and is a better oxide superconductor.

By the way, this superconductor is a crystalline oxide obtained as a sintered body, and when a superconducting current is passed parallel to the six faces of the single crystal, j. J //
There is a large difference in the ratio of /JJ-, lO ~ 1000, and the critical magnetic field B. 2 also has the property that when a magnetic field is applied perpendicularly and parallel to the six faces, there is a difference of more than 20 between B, ttl, B, and L.

Therefore, the sintered body of this oxide superconductor as it is,
If the pulverized powder was simply made into a long length, the orientation of the crystals would be random, resulting in a problem in that the desired current density and critical magnetic field could not be obtained.

(Problem to be solved by the invention) In this way, the B1-8r-Ca-Cu-0 system and the Tl2-
Ba-Ca-Cu-0 based oxide superconductor has a crystalline 6
Because superconducting current flows along the plane, if the sintered body of this oxide superconductor is used as it is, or if the pulverized powder is simply made into a long length, the orientation of the crystals will be random, and the desired critical current density will not be achieved. There was a problem that j could not be obtained.

The present invention has been made to solve these conventional difficulties, and is based on the B1-8r-Ca-Cu-0 system or Tl2-
The object of the present invention is to provide a tape-shaped or rectangular oxide superconductor with a high critical current density using Ba-Ca-Cu-0 based superconductor powder.

[Structure of the Invention] (Means for Solving the Problems) The oxide superconductor of the present invention is produced by combining an oxide superconductor powder represented by the following formula 8% (δ represents an oxygen defect; the same applies hereinafter) into a metal. In the superconductor filled in a tube, the oxide superconductor powder is
The oxide superconductor powder is rolled together with the metal tube to form a layer with a thickness of 100 μm or less, and the metal tube is filled with the oxide superconductor powder to form a core, and a plurality of cores are made of a common metal. In a superconductor housed in a tube,
It is characterized in that the oxide superconductor powder is rolled together with the core metal tube or together with the core metal tube and a common metal tube to form a layer with a thickness of 100 μm or less.

The oxide superconductor and oxide superconductor wire of the present invention are
For example, it can be obtained by the method shown below.

[Manufacture of oxide superconductor powder] First, old, Sr, Ca, Cu or Tl, Ba,
Ca.

B1-8r-Ca-Cu-0 system such as Cu or Tl
- Carbonates, oxides, organic acid salts, etc. of the constituent elements of the Ba-Ca-Cu-0 system are mixed in a stoichiometric ratio, that is, an atomic ratio of 2
:2:L:2 or 2:2:2:3 and mix them thoroughly. Note that the elements constituting these oxide superconductors do not need to be in a strictly stoichiometric ratio, and may differ by about 10% depending on manufacturing conditions and the like. It is also possible to lower the reaction temperature by adding a trace amount of an alkali metal compound.

After mixing the aforementioned raw materials, they are calcined and pulverized into a desired shape, and then fired. Calcining is not necessarily necessary. firing,
Calcination is carried out in an oxygen-containing atmosphere where sufficient oxygen can be supplied at a temperature of 800°C or higher and below the melting point, preferably 870°C to 9°C.
00°C is appropriate.

The obtained oxide superconductor sintered body is then pulverized using a ball mill or other known means. At this time, the oxide superconductor powder is divided from the cleavage plane and becomes fine powder. The average particle diameter is suitably around 1 μα. Note that, if necessary, the pulverized powder may be classified and used.

[Manufacture of a single superconductor] The powder of the oxide superconductor described above is placed in a metal tube, and subjected to area reduction processing such as forging, rolling, and wire drawing in order by conventional methods to form a thin wire with a circular cross section. When the diameter is reduced to an arbitrary outer diameter, the thickness of the oxide superconductor layer is reduced to 100μ by rolling.
Roll it flat until it becomes less than m.

In addition, when surface reduction processing becomes difficult due to work hardening, annealing treatment is performed as appropriate.

Further, instead of processing the cross section into a circular shape, the surface reduction processing may be performed while keeping the rectangular shape while restricting the side surfaces with Turkshe Sodolol or the like.

Metal tubes include Ag, Au, pi, Pdq C
Metal tubes such as uq cupronickel and stainless steel can be used.

FIG. 1 shows the superconductor obtained in this way, where 1 is a rectangular metal tube, and 2 is an oxide superconductor that has been rolled together with the metal tube 1 to a thickness t of 100 μl or less. The orientation rate is usually 70% or more.

The above orientation rate is determined by removing the coating metal and measuring the diffraction intensity of the internal oxide superconductor using X-ray diffraction, and is expressed as the ratio of the (00 eu) peak of the 0 plane and the peak of the (117) plane. It is something that

In the superconductor manufactured in this way, the zero surface of the oxide superconductor powder is oriented in the direction perpendicular to the pressing direction or in the longitudinal direction of the wire during the pressurization or wire drawing process, so that the wire as a whole The current capacity of the device is greatly improved, and the critical magnetic field is also improved.

[Manufacture of multi-superconductor] The single superconductor described above is used as a core, and as shown in FIG. Multi-superconductor. As the material for this metal tube 3, the metal for the core described above can be used. Incidentally, up to the core stage, the layer of oxide superconductor 3 may be rolled in a range exceeding 100 .mu.m, and after forming a multi-structure, it may be further rolled to finally make this layer 100 .mu.m or less.

In addition, when used for high frequency alternating current or pulsed current,
For example, as shown in FIG. 3, if a composite tube is used in which the inside is made of a highly conductive metal such as copper 1a and the outside is made of a resistance metal such as cupronickel 1b, high frequency loss can be reduced.

(Function) The superconductor of the present invention is a B1-3r filled in a metal tube.
-Ca-Cu-0 system or Ti-Ba-Ca-Cu-0
Since the zero plane of the crystal of the oxide superconductor powder of the system is oriented in the length direction, that is, in the direction in which the superconducting current flows, during the rolling process, the superconducting current tends to flow in the longitudinal direction of the metal tube.
Furthermore, by arranging the flat plane parallel to the direction of the magnetic field when forming the coil, changes in critical current density due to the magnetic field can be reduced.

Furthermore, when producing the superconductor of the present invention, the superconductor powder is oriented by drawing the metal tube so that the zero plane is parallel to the drawing direction, so it is only necessary to consider the degree of diameter reduction during the drawing process. , the superconductor powder is oriented simultaneously with rolling.

Furthermore, when this is used as a core and multiple layers are stacked and housed in a rectangular metal tube, the current capacity increases,
By further rolling, the superconductor layer can be easily processed into a thinner layer. In this case the metal tube of each core acts as a stabilizing material. Furthermore, when a composite metal tube in which a highly conductive metal such as copper is coated with a resistance metal such as cupronickel is used as the metal tube of each core, the high frequency characteristics are improved.

(Example) Next, examples of the present invention will be described.

Example 1 Old 0SSrCO1 CaCO3 and CuO powders were thoroughly mixed in a molar ratio of l:2:1:2, calcined in air at 850°C for 10 hours, and after repeating this twice, they were heated in a ball mill for 24 hours. Time-pulverized, B125r2CaICu20
A powder was obtained.

8+δ This powder is sealed at one end with an outer diameter of 2011 and an inner diameter of 171
1. After putting it into a 100 ml Ag tube and sealing the other end leaving a ventilation hole, it was rolled to various thicknesses (thickness of the oxide superconductor layer) by swaging and rolling. I made a tape. Next, add this tape to 880
Heat treatment was carried out in air at .degree. C. for 5 hours.

Critical current density (77K
), and the metal coating of these tapes was stripped off to measure the relationship between the thickness of the oxide superconductor layer and the orientation rate. The measurement results are shown in Figure 4. Note that the orientation rate is determined by the (0010) peak of the 0-plane of the crystal appearing in the X-ray diffraction graph and (
117) as a ratio to the surface peak. As is clear from the figure, the orientation and critical current density are rapidly improved when the thickness of the oxide superconductor layer becomes 100 μm or less.

In the above examples, 81 was used as the oxide superconductor.
Theory 2 regarding an example using Sr Ca Cu O
2128+δ Tβ Although it was clear, B10 Srz Ca2Cua Oto+a
, 2Baz Ca2Cu30 to+a, and T
When a similar experiment was conducted using J22Ba2CalCuO, a remarkable improvement in properties due to orientation was also observed for 28+δ.

Further, a multi-layer superconductor as shown in FIG. 3 was manufactured using the above-mentioned superconductor tape as a core, and the same thickness-orientation-critical current characteristics of the oxide superconductor as in the example were obtained.

[Effects of the Invention] As is clear from the above examples, the superconductor of the present invention has the zero plane of the crystal oriented in the direction of current flow, so a high current density can be obtained, and the criticality caused by the magnetic field can be reduced. Less reduction in current density. Further, by forming a multi-structure using this superconductor as a core, the current capacity can be increased, and furthermore, the oxide superconductor layer can be easily made thinner, and a high critical current density can be obtained.

[Brief explanation of the drawing]

1 to 3 are enlarged cross-sectional views schematically showing embodiments of the present invention, and FIG. 4 is a graph showing the effects of the present invention. 1... Rectangular metal tube 1a... Copper 1b... Cupronickel 2... Oxide superconductor 3...・・・・・・Rectangular metal tube

Claims (2)

[Claims] (1) Bi, Sr, Ca, Cu in atomic ratio of 2:2:1
:2 or 2:2:2:3, or an oxide superconductor containing Tl, Ba, Ca, Cu in an atomic ratio of 2:2:1:
2 or 2:2:2:3 in a metal tube, the oxide superconductor powder is rolled together with the metal tube,
A superconductor characterized by having a layered structure with a thickness of 100 μm or less. (2) Bi, Sr, Ca, Cu in atomic ratio of 2:2:1
:2 or 2:2:2:3, or an oxide superconductor containing Tl, Ba, Ca, Cu in an atomic ratio of 2:2:1:
A metal tube is filled with oxide superconductor powder containing a ratio of 2 or 2:2:2:3 to form a core, and multiple strips of this core are
In the superconductor housed in a common metal tube, the oxide superconductor powder is rolled together with the core metal tube or together with the core metal tube and the common metal tube to a thickness of 100 μm or less. A superconductor characterized by being layered.