JPH04179004A - Oxide superconducting tape conductor - Google Patents

Abstract

PURPOSE:To obtain an oxide superconductive tape conductor of better superconductivity characteristics by successively forming a specific precious metal layer, an insulation oxide layer and an oxide superconductive thin film in order on a base member. CONSTITUTION:An oxide superconductive tape conductor 1 is constituted of a flexible tape-like base member 2 of heat resisting metal, a precious metal layer 3 of Pt, Au and the like formed on the base member 2, an insulation oxide layer 4 of SrTiO3, MgO and the like formed on the precious metal layer 3 at a film-forming temperature of not more than 500 deg.C in thickness of not more than 1.5mum and an oxide superconductive thin film formed on the insulation oxide layer 4. Accordingly, the precious metal layer 3 and the insulation oxide layer 4 suppress the diffusing reaction of the base member 2 and the oxide superconductive thin film 5 and the adhesion of the insulation oxide layer 4 and the base member 2 is improved by existance of the precious metal layer 3. Further, since the oxide superconductive thin film 5 is formed on the insulation oxide layer 4 of good matching to the crystal of the oxide superconductive thin film 5, the matching of the crystal of the oxide superconductive thin film 5 is improved. Thereby, the oxide superconductive tape conductor 1 showing better superconductivity characteristics may be obtained.

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention is for the use of oxide superconductors as power application superconducting conductors used in power cables, superconducting magnets, superconducting power storage, transformers, superconducting generators, etc. In this method, an oxide superconducting thin film is formed on a tape-shaped base material.

"Prior Art" The 90-grade oxide superconductor discovered in 1987 has a superconducting transition temperature that exceeds the temperature of liquid nitrogen (77K), and is expected to have a wide range of applications in electric power and electronics. There is.

However, because this type of oxide superconductor has a short coherence length, polycrystalline grain boundaries and impurities are likely to cause obstacles, and it is easy for current to flow in a specific direction of the crystal, while electrical current is difficult to flow in a specific direction. Due to its large crystal orientation, in order to obtain a practical current density for power applications, etc., it is necessary to reduce the number of grain boundaries as much as possible and manufacture oxide superconducting conductors with dense and highly crystalline orientation. There is a need to.

Therefore, unlike the conventional method of obtaining oxide superconductors by mixing powder and sintering, the iiJ film process, which can produce oxide superconductors without going through the sintering process, is a promising method for oxide superconductors. It is attracting attention as a method for manufacturing conductors.

Conventionally, this type of film formation process includes vacuum evaporation, sputtering, laser evaporation, MBE (molecular beam epitaxy), CVD (chemical vapor deposition), and IVD (
The important thing in these film-forming processes is that the crystal orientation of the obtained oxide superconducting thin film is well-organized.

When carrying out a film formation process taking into account the crystal orientation, a substrate made of a single crystal with a crystal structure similar to that of an oxide superconducting thin film is used, and film formation conditions such as heat treatment temperature are appropriately set. 2. Description of the Related Art In recent years, oxide superconducting thin films have been manufactured by performing ideal epitaxial growth on a substrate.

``Problems to be Solved by the Invention'' By the way, when trying to use an oxide superconducting thin film for power applications such as power transmission lines or superconducting magnets, it is difficult to use the oxide superconducting thin film on a long flexible substrate. It is necessary to form the Moreover, this flexible base material needs to be heat resistant so that it can withstand heat treatment, and as mentioned above, it is advantageous to have a structure similar to the crystal of the oxide superconducting thin film. .

However, at present, tape materials made of heat-resistant metals such as Hastelloy are likely to be used as long heat-resistant base materials; It has poor consistency with the crystals of the thin film, and moreover, during the heat treatment during film formation, a mutual diffusion reaction occurs between the oxide superconducting thin film and the composition of the oxide superconducting thin film, which destroys its superconductivity. There was a problem that the characteristics deteriorated.

The present invention has been made to solve the above problems, and exhibits excellent superconducting properties on the outside of a long metal base material that does not have sufficient crystal consistency with an oxide superconducting thin film. An object of the present invention is to provide an oxide superconducting tape conductor that can be provided with an oxide superconducting thin film.

"Means for Solving the Problems" In order to solve the above-mentioned problems, the present invention provides a flexible tape-shaped base material made of heat-resistant metal, and a tape-like base material formed on this base material.
t, Au, etc., and a thickness of 1.5 μtrr or less on this noble metal layer at a film formation temperature of 500°C or less.
It consists of an insulating oxide layer such as S rT jo s or Mgo which has been acidified, and an oxide superconducting 'FI' film formed on this insulating oxide layer.

The noble metal layer and insulating oxide layer formed on the fully heated tape-shaped base material suppress the diffusion reaction between the base material and the oxide superconducting thin film. The adhesion between the oxide layer and the base material is improved.Furthermore, since the oxide superconductor 4 film is formed on the insulating oxide layer that has good consistency with the crystals of the oxide superconductor thin film, the oxide superconductor thin film The crystal integrity of the oxide becomes good, and an oxide superconducting conductor with excellent superconducting properties is formed on the insulating oxide layer.

"Example" Figure 1 shows an example of the oxide superconducting conductor of the present invention. It is composed of a noble metal layer 3 coated on the upper surface of the material 2, an insulating oxide layer 4 coated on the upper surface of this noble metal layer 3, and an oxide superconducting thin film 5 coated on the upper surface of this insulating oxide layer 4. has been done. In addition,
Although not shown in the drawings, if necessary, a coating treatment is performed on the oxide superconducting thin film 5 to form a coating layer to prevent deterioration of the superconducting properties of the oxide superconducting thin film 5 over time or due to the environment. You may also do this.

The material constituting the base material 2 is preferably a heat-resistant alloy such as Hastelloy, which has excellent heat resistance and oxidation resistance. As will be explained later, when producing an oxidizing superconducting thin film,
Since the heat treatment is performed at about 600 to 850'C, preferably in an oxygen gas atmosphere, even after this heat treatment, the base material 2
This is to prevent the strength from decreasing. Moreover, the thickness of the base material 2 is preferably 0.5 mm or less. By making the thickness of the base material 2 0.5 mm or less, flexibility of the base material is ensured,
When oxide superconductor conductor I is bent, oxide superconductor 1
Although the distortion acting on 1i5 can be reduced, 0.
If it is thicker than 5+m, the flexibility of the base material 2 will be impaired and the strain caused by bending will increase, which is not preferable.

The noble metal layer 3 is made of a noble metal such as Pt or Au or an alloy of noble metals, and is coated on the upper surface of the base material 2 by a film forming method such as sputtering, CVD, or laser vapor deposition. This noble metal layer 3 is provided in order to suppress the diffusion reaction between the base material 2 and the oxide superconducting thin film 5 during heat treatment, which will be described later. coated with Considering the effect of suppressing the diffusion reaction and the effect of improving adhesion, the thickness of the noble metal R3 is as follows:
A range of 0.1 to 0.5 μl is preferred. Also, Takamei 14
If 83 is thinner than 0.1 μm, the effect of suppressing the diffusion reaction will be insufficient, and if it is thicker than 0.5 μm, there may be a problem with the adhesion of the insulating oxide s4.

The insulating oxide layer 4 is manufactured by a film forming method such as a sputtering method, a CVD method, or a laser evaporation method, and is made of 5rTiO.
It is a thin film made of an insulating oxide such as S, MgO, or yttria-stabilized zirconia (YSZ), and is formed for the purpose of controlling the diffusion reaction between the base material 1 and the oxide superconducting thin film 5 and for preventing peeling. Ru. In order to suppress the diffusion reaction and prevent the peeling phenomenon, when forming the insulating oxide layer 4,
It is important to form the film to a thickness of 15 μm or less at a substrate processing temperature of 00° C. or less. Forming at a temperature exceeding 50Q°C is unfavorable due to interdiffusion reaction with the base material, and 1
．． Formation of a thickness exceeding 5 μm is undesirable due to the formation of cracks.

The oxide superconducting thin film 5 is formed by a film forming method such as a sputtering method, a CVD method, or a laser evaporation method.
5r-Ca-Cu-0 system, T IB a-Ca-Cu-
0 series, etc., and is formed to have a thickness of several micrometers to several 10 micrometers.

The method for manufacturing the oxide superconducting tape conductor 1 will be described below.

Once a tape-shaped base material 2 is prepared, a noble metal layer 3 is formed on the surface of this base material 2 by a film forming method such as a sputtering method or a vacuum evaporation method. Note that in order to form the noble metal layer 3 on the entire upper surface of the long base material 2, the base material 2 is wound around a roller-shaped delivery device, and during the process of winding it up from this delivery device to a winding device, the film forming device The base material 2
The noble metal layer 3 can be formed over the entire length of the substrate.

Once the noble metal layer 3 has been formed, the base material 2 on which the noble metal layer 3 has been formed is set in the film forming apparatus again, and the insulating oxide layer 4 is formed on the upper surface of the noble metal layer 3 in the same manner as described above.

Once the insulating oxide layer 4 has been formed, the base material 2 on which the noble metal layer 3 and the insulating oxide layer 4 have been formed is further set in a film forming apparatus, and a precursor N of an oxide superconducting thin film is deposited on the upper surface of the insulating oxide R4. Forms a film. When forming this precursor thin film, the thin film as formed in the film forming chamber may be crystallized but not a superconductor, or it may be amorphous. If necessary, heat treatment is applied. The heat treatment may be performed in a film formation chamber simultaneously with film formation, or may be performed separately in a heating furnace after film formation. When performing this heat treatment, Y-Ba-Cu-0 system and TI-Ba-Ca
-Cu-0 type materials are preferably heat-treated in an oxygen gas atmosphere. Furthermore, the heat treatment temperature was 60
Preferably, the temperature is 0 to 850°C for several minutes to several tens of hours.

When forming a precursor thin film on the insulating oxide layer 54 as described above, the crystals of the oxide superconducting thin film 5 have good consistency with the crystals of the insulating oxide layer 4, so that the precursor thin film is formed on the insulating oxide layer 4. The precursor thin film is deposited with good consistency. Therefore, by heat-treating such a precursor thin film with good crystal consistency, an oxide layer [N-conducting film 5] with good crystal consistency is generated.

In the case of heat treatment as described above, the thermal diffusion reaction between the base material 2 and the oxide superconducting thin film 5 becomes a problem.

In this respect, in the structure of the present invention, a noble metal layer 3 and an insulating oxide layer 4 are provided between the base material 2 and the oxide superconducting thin film 5, and the noble metal layer 3 has a high melting point and is at a heat treatment temperature. The interdiffusion reaction between the base material 2 and the noble metal layer 3 is small, the interdiffusion reaction between the insulating oxide layer 4 and the noble metal layer 3 is also small, and the insulating oxide layer 4 has a higher melting point, so the oxide superconducting thin film 5 No adverse effects due to elemental diffusion. Therefore, the oxide superconducting thin film 5 has good bonding properties after heat treatment.
is obtained.

The oxide superconducting tape conductor 1 manufactured as described above is
Since the electrical resistance of the oxide superconducting thin film 5 becomes zero by cooling it with a coolant such as liquid hydrogen, it can be used for power transportation.

Since the oxide superconducting tape conductor 1 having the above structure uses the base material 2 made of heat-resistant metal, it maintains high strength even after heat treatment. Further, since the base material 2 is in the form of a tape with a thickness of 0.5+em or less, it has excellent flexibility, and even when bending stress is applied, the strain acting on the oxide superconducting thin film 5 is small.

"Manufacturing example" Width 5 l11m made of Ni alloy (Hastelloy C276),
A tape-shaped base material with a thickness of 0.5 am, a PT target, a SrTios target, and a Y-B a
-Cu-0 series targets were prepared, and precursor thin films of a noble metal layer, an insulating oxide layer, and an oxide superconducting N film were sequentially formed on the substrate using a high-frequency sputtering device using each target.

In the sputtering equipment that forms the noble metal layer and the insulating oxide layer,
In a sputtering device that forms an oxide superconducting thin film while attaching a target to a holder, the substrate is set in a delivery device and a winding device inside a vacuum container, the inside of the vacuum container is evacuated, and the material is taken up from the delivery device. The film was formed by sputtering while feeding the base material into the apparatus.

A noble metal layer with a thickness of 0.2μ, an insulating oxide layer with a thickness of 0.5μ, and a precursor thin film with a thickness of 3μl were sequentially formed on the Go board by the above-described operations. A roll-shaped delivery device and a winding device were installed inside the formation chamber of the sputtering device, so that the base material discharged from the delivery device communicated with the vicinity of the target and then wound up by the winding device.

At this time, the pressure in the vacuum chamber of the sputtering device is tX+
The atmosphere was set to O'□'Pa and 100% argon gas. Further, while forming the precursor thin film, the portion of the base material where the precursor N film was to be formed was heated to 700° C. using a heater.

When the superconducting properties of the obtained oxide superconducting tape conductor were measured at multiple locations along the length of the base material, Tc = 85 at all locations, and critical current density Jc = 5000 A/am' at 77K. Do not show. This oxide superconducting thin film had C-axis orientation, but was polycrystalline. Furthermore, when the obtained oxide superconducting tape conductor was bent, no peeling occurred in the oxide superconducting thin film.

"Effects of the Invention" As explained above, the present invention sequentially forms a noble metal layer, an insulating oxide layer, and an oxide superconducting thin film on a base material. No dispersion reaction occurs between the base material and the oxide superconducting thin film even if the substrate and the oxide superconducting thin film are mixed.

Therefore, the oxide layer 1 does not change its composition even after heat treatment.
[An oxide superconducting tape conductor having a high critical current density and having a N-conducting film can be obtained. Furthermore, since the base material is made of a heat-resistant metal, the strength of the base material does not decrease even after heat treatment. Furthermore, since the noble metal layer is formed on the base material before forming the insulating oxide layer, the noble metal layer is bonded to the base material with good adhesion, and the insulating oxide layer is bonded to the noble metal layer with good adhesion. Since the oxide superconducting tape conductor is bonded with elasticity, even when the base material is bent, it is possible to provide an oxide superconducting tape conductor that is resistant to peeling due to bending. Furthermore, since superconducting NIII is formed on the insulating oxide layer, oxide superconducting NM with excellent crystal consistency is produced, and an oxide superconducting tape conductor with excellent superconducting properties can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Oxide superconducting tape conductor, 2... Base material, 3...
- Noble metal layer, 4... Insulating oxide layer, 5... Oxide superconducting thin film.

Claims (1)

[Claims] A flexible tape-shaped base material made of a heat-resistant metal, a noble metal layer made of Pt, Au, etc. formed on the base material, and a film formed on the noble metal layer to a thickness of 1.5 mm at a film formation temperature of 500° C. or less. 5μm
An oxide superconducting tape conductor characterized by comprising an insulating oxide layer such as SrTiO_3 or MgO formed as follows, and an oxide superconducting thin film formed on this insulating oxide layer.