JPH04138624A - Manufacture of oxide superconducting layer - Google Patents

Abstract

PURPOSE:To improve strong toughness in reduction or the like of generation of a bending crack due to brittleness by forming a dust layer, contained with a silver component, on a heat resistant conductor by an electrocoating method sintered after a press process. CONSTITUTION:A bismuth system oxide and iodine-aceton dispersion liquid of silver iodide are placed in an electrocoating tank to arrange a platinum plate cathode in this electrocoating tank. Next, a silver tape is arranged in a central part of a platinum electrode and electrocoated to form a dust layer containing a silver component. Then, the silver tape, provided with this dust layer, is press-processed to compress the dust layer, and then a sintering process is performed to prepare a silver-contained integral silver tape. In this way, the dust layer can stably and efficiently be formed further in a uniform thickness on a heat resistant conductor of various forms containing a large area body and a round wire or the like, and also continuous manufacture is made possible.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention provides excellent toughness and superconducting properties by sintering a powder layer containing a silver component made of an oxide superconductor formed by electrodeposition. The present invention relates to a method for manufacturing an oxide superconducting layer.

BACKGROUND ART A known method is to develop a slurry containing an oxide superconductor and silver powder using a doctor blade method, and then sinter the slurry to produce a silver-containing oxide superconducting layer. Adding silver to the oxide superconducting layer is effective in improving toughness, such as reducing the occurrence of bending cracks due to brittleness.

However, with the manufacturing method that applies the doctor blade method, it is difficult to form a large-area oxide superconducting layer, partly because it requires advanced technology to form a layer with a uniform thickness. There were problems such as difficulty in forming the layer, which placed great restrictions on the supporting base material for the spreading layer.

Means for Solving the Problems The present invention overcomes the above problems by successfully forming a silver-containing oxide superconducting layer by applying an electrodeposition method.

That is, the present invention includes a step of forming a powder layer containing a silver component made of an oxide superconductor by electrodeposition on a heat-resistant conductor, and a step of pressing the electrodeposited powder layer and then sintering it. A method for manufacturing an oxide superconducting layer is provided.

It is possible to form a silver component-containing powder layer made of oxide superconductor by active electrodeposition, and it can be applied to various forms of heat-resistant conductors, including large-area bodies and round wires, by press processing. A powder layer containing a silver component made of an oxide superconductor can be continuously formed with good thickness uniformity. As a result, an oxide superconducting layer having excellent toughness due to the inclusion of silver can be manufactured without restrictions on the formation area.

Examples of Constituent Elements of the Invention In the present invention, a silver component-containing powder layer made of an oxide superconductor is formed on a heat-resistant conductor by electrodeposition.

Such a powder layer can be formed, for example, by a method using oxide superconductor powder and silver powder or a silver compound, or by a method using oxide superconductor powder containing a silver component.

There are no particular limitations on the oxide superconductor powder used. For example, YBa2 Cu303 and YIBa2Cu, 00
Y-based oxide superconductor such as Ba1-d k dBi0
Ba-based oxide superconductor such as No. 3, Nd2-e Ce,.

Nd-based oxide superconductor such as Cub, B10-tPb
gSr2 Ca2C+, z○ゎya Bi25r2Ca4-
+ Bi-based oxide superconductors such as CuO, and its derivatives La
oxide superconductors, T1-based oxide superconductors, Pb-based oxide superconductors, etc., and those in which the components such as Y are replaced with other rare earth elements, or those in which components such as Ba are replaced with other alkaline earth metals. It is possible to use a powder made of a Y-based oxide superconductor containing a pinning center, or a powder made of a Y-based oxide superconductor containing a pinning center.

On the other hand, oxide superconductor powder containing a silver component is obtained by mixing oxide superconductor powder and silver powder or a silver compound, for example.
It can be obtained by calcining the mixture and pulverizing it.

The pinning center-containing oxide superconductor described above has the advantage of exhibiting a large critical current density even under a high magnetic field due to the pinning effect of the magnetic flux by the pinning center. Such an oxide superconductor can be formed by a melting method, for example, by calcining a raw material powder for forming an oxide superconductor, or an oxide superconductor powder and a non-oxide superconductor powder in an appropriate composition, and then heating and melting the powder. The MPMG method (Melt-Powd
ering-Melt-Growth), etc.

As the silver component, silver powder or a silver compound such as silver iodide that can be subjected to electrodeposition treatment is used. The silver component may be added during the calcination step of the oxide superconductor powder.

Electrodeposition of the oxide superconductor powder and silver powder or silver compound, or the oxide superconductor powder containing a silver component onto the heat-resistant conductor can be performed by an electrophoretic electrodeposition method. For example, if the particle size is 0.1 to 10% in a dispersion medium such as acetone,
A heat-resistant conductor that undergoes electrodeposition is introduced into an electrodeposition tank containing a dispersion liquid containing um oxide superconductor powder and silver powder or a silver compound added thereto, with a counter electrode placed therein. Examples include a method of electrodeposition while applying a voltage between a heat-resistant conductor and a counter electrode. Note that when using an oxide superconductor powder containing a silver component, addition of silver powder or silver compound can be omitted. In the electrodeposition process, whether the heat-resistant conductor is used as an anode or a cathode is determined depending on the charge of the oxide superconductor powder, and is used as a pole on which attractive force acts based on Coulomb force. The magnitude of the applied voltage is appropriately determined and is usually 50 to 1000 V in terms of DC voltage. The thickness of the powder layer formed by electrodeposition is arbitrary, and is generally 5.
00 μm or less.

In the above, the amount of silver powder or silver compound used is generally 1 to 5 moles based on the number of moles of the silver component per mole of the oxide superconductor, but is not limited thereto.

Since the heat-resistant conductor is subjected to a sintering process together with the formed powder layer, a material that can withstand the sintering temperature and does not react with the powder layer is used. Generally, silver, a silver alloy, or a metal or ceramic composite material made of silver or a silver alloy is used. The form of the heat-resistant conductor is arbitrary, such as a tape, a plate, or a wire.

The silver component-containing powder layer made of the oxide superconductor electrodeposited on the heat-resistant conductor is pressed and densified before being sintered. The pressing process may be performed by any suitable method, such as a mechanical press method or a hydrostatic pressure method.

Pressing treatment is effective in preventing cracks due to densification of the oxide superconducting layer formed by sintering treatment, and in improving toughness and superconducting properties. In that case, the degree of densification of the electrodeposited powder layer by pressing is preferably 60% or more of the crystal density (theoretical value) of the oxide superconductor, especially an apparent density of 70 to 90%. . Typical press pressure is 0.5 to 30 t/cd.

The pressed powder layer is subjected to a sintering process.

This bulks up the oxide superconductor powder and forms an integral silver-containing oxide superconductor layer, particularly a thick layer. The sintering conditions may be determined as appropriate depending on the type of oxide superconductor. Typical sintering temperature is 800~
The temperature range is 1200°C, which is lower than the melting point of the heat-resistant conductor. Further, the sintering time is usually 200 hours or less, particularly 2 to 150 hours, but is not limited thereto.

Effects of the Invention According to the present invention, a powder layer containing a silver component made of an oxide superconductor is formed by an electrodeposition method and then press-treated to obtain a silver-containing oxide superconducting layer. Stably on various forms of heat-resistant conductors, including square bodies and round wires, etc.
Moreover, the oxide superconducting layer can be formed efficiently and with good thickness uniformity, and continuous production is also possible. The oxide superconducting layer has excellent toughness and superconducting properties due to the silver content.

Example I B+2-z Pbr 5r2Ca2 CLI30h (g
= 0.6) with a particle size of 0.1 to 10 μm (the same applies hereinafter) and 5 parts of silver iodide were dispersed in 1000 parts of a 0.05% iodine-acetone solution. The dispersion was placed in an electrodeposition tank, and a cathode made of a cylindrical platinum plate was placed in the electrodeposition tank. A silver tape with a thickness of 0.1 mm was placed in the center of the platinum electrode, and a voltage of 500V was applied. A DC voltage was applied to form a powder layer containing a silver component made of an oxide superconductor on the silver tape. The thickness of the electrodeposited powder layer was approximately 60 μm, and its apparent density was 2.9 g/ci.

Then, the silver tape with the powder layer was pressed (5
After compressing the powder layer using t/coOL (the apparent density is 4
．． 5g/cn? ), it was sintered at a temperature of 830-840° C. for 60 hours with heating at a rate of 200° C./hour to obtain a silver tape having an integral silver-containing oxide superconducting layer without cracks. Note that the oxide superconducting layer contained silver with good dispersibility, and the content was 33% by weight.

In addition, the critical temperature of the oxide superconducting layer in the silver tape is 1
02 and the critical current density is 250 OA/ct
(77K).

Furthermore, the silver tape with the oxide superconducting layer was added with a diameter of 60 mm.
No cracks or cracks were observed in the oxide superconducting layer when it was wrapped around a 11II11 pipe.

In addition, in the above, the critical temperature is 0, 1 A/ca
The change in electrical resistance due to temperature was measured by the four-terminal method under a current density of r, without cooling with liquid nitrogen, and this was the temperature when the voltage generated between the voltage terminals became O. In addition, the critical current density is determined by gradually increasing the current value while cooling with Power REIT in liquid nitrogen, and measuring the change in voltage between the voltage terminals due to the applied current using the four-terminal method.
The value is calculated by measuring the current value when a voltage of μV,/'Cm appears and dividing it by the cross-sectional area of the oxide superconducting layer (the same applies hereinafter).

Comparative Example 1 A silver tape with an oxide superconducting layer containing no silver was obtained according to Example 1 without using silver iodide.

The critical temperature of the oxide superconducting layer in the silver tape is 9
9, and the critical current density is 700A,/ci (77K
)Met.

Furthermore, when such a silver tape was wrapped around a pipe having a diameter of 60 mm, cracks or cracks occurred in the oxide superconducting layer.

Example 2 10 parts of Y20, 334 parts of BaCO, 21 parts of Cu, and 2062 parts of Ag were mixed, and this mixed powder was heated to 800'
C. for 12 hours to obtain a calcined body of Y-based oxide superconductor containing silver.

Next, the calcined body was pulverized to obtain a powder with a particle size ranging from 0.1 to 10, 20 parts of the powder was dispersed in 1000 parts of a 0.05% iodine-acetone solution, and the dispersion was electrolyzed. After placing an anode made of a cylindrical platinum plate in an electrodeposition bath, a 0.1 mm thick silver tape was placed in the center of the platinum electrode, and a DC voltage of 400 V was applied. A powder layer containing a silver component and made of an oxide superconductor was formed on the tape. The thickness of the electrodeposited powder layer was approximately 50μ steel, and its apparent density was 3.1 g/cat.

Next, the silver tape with the powder layer was pressed (2
t/c+J) to compress the powder layer (the apparent density is 4
．． 2g/cat), it was heated at a rate of 200°C/hour and sintered at a temperature of 900°C for 12 hours to obtain a silver tape with a crack-free silver-containing integral oxide superconducting layer. Ta. The oxide superconducting layer contained silver with good dispersibility, and its content was 30% by weight.

In addition, the critical temperature of the oxide superconducting layer in the silver tape is 89
The critical current density is 1400 A/c! (
77K).

Furthermore, the silver tape with the oxide superconducting layer was added with a diameter of 60 mm.
No cracks or cracks were observed in the oxide superconducting layer when it was wrapped around a 1 m1 pipe.

Comparative Example 2 A silver tape with an oxide superconducting layer containing no silver was obtained according to Example 2 without using silver oxide.

The critical temperature of the oxide superconducting layer in the silver tape is 8
8, and the critical current density is 300A/cnf (77K
)Met.

Further, when such a silver tape was wrapped around a pipe having a diameter of 60 mm+, cracks or crazing occurred in the oxide superconducting layer.

Claims (1)

[Claims] 1. It is characterized by comprising the steps of forming a powder layer containing a silver component made of an oxide superconductor by electrodeposition on a heat-resistant conductor, and pressing the electrodeposited powder layer and then sintering it. A method for manufacturing an oxide superconducting layer.