JPH0825248B2 - Oxide superconducting laminate and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to an oxide superconducting laminate and a method for producing the same. More specifically, the present invention relates to an oxide superconducting laminate in which an intermediate layer composed of two layers is formed on a metal substrate, and a method for producing the same.

[Conventional technology]

In recent years, oxide superconductors have attracted attention due to their high critical temperature, and are expected to be used in various fields such as power field, nuclear magnetic resonance computed tomography (MRI: Magnetic Resonance Imaging), and magnetic shield. . When these oxide superconductors are put into practical use, it is possible to manufacture a device and a substrate by using the oxide superconductor, but a method of forming a layer of the oxide superconductor on a conventional existing substrate is is there.

In particular, since metals can be processed into various shapes, it is highly useful if an oxide superconductor can be formed on a metal substrate. Furthermore, even when the oxide superconductor can be formed on the metal substrate, the current oxide superconductor is cooled at the liquid nitrogen temperature (77K) and used,
A structure that absorbs the thermal stress generated between the metal substrate and the oxide superconductor is required.

As a known example, for example, in JP-A-63-279517, it is proposed to form a glass layer between the metal body and the oxide ceramics superconductor layer, and in JP-A-63-305574, alumina, It has been proposed that a stabilizer such as platinum (Pt), silver (Ag), or gold (Au) that does not cause a chemical reaction be interposed between a substrate such as zirconia or copper and a superconductor.

[Problems to be Solved by the Invention]

However, providing an intermediate layer of the glass layer on the metal substrate means that most of the glass layers are oxide superconductors, especially Bi-Sr-Ca.
It is not preferable because it reacts violently with a —Cu—O compound and the superconducting properties are significantly deteriorated. Even if an intermediate layer of a noble metal, which is chemically stable with an oxide superconductor, is formed, the firing temperature of the oxide superconductor is as high as 800 to 950 ° C, so the precious metal intermediate layer and the metal substrate are Peeling occurs between them, and as a result, there arises a problem that the noble metal intermediate layer is destroyed and the oxide superconductor and the metal substrate react with each other. Furthermore, even if the oxide superconductor is formed on the noble metal intermediate layer without breaking the noble metal intermediate layer to form a laminate, cooling to the liquid nitrogen temperature causes thermal expansion of the metal substrate and the oxide superconductor. The difference causes a crack in the oxide superconductor, which is a problem.

Further, when the ceramic layer is formed as the intermediate layer on the metal substrate, the adhesion between the metal substrate and the ceramic is good, but when the oxide superconductor is formed on the ceramic intermediate layer to obtain the oxide superconductor. However, the oxide superconductor passes through the ceramic intermediate layer and reacts with the metal substrate, so that the adhesion between the metal substrate and the ceramic layer is impaired, which is not preferable.

As described above, the intermediate layer provided on the conventional substrate is for the purpose of preventing either peeling between the substrate and the intermediate layer or reaction between the intermediate layer and the superconductor. It has been difficult to obtain a body-metal composite without inconvenience.

The present invention provides a stable oxide superconducting laminate that prevents a reaction between a metal substrate and a superconductor and that does not separate from the metal substrate in a wide temperature range from the firing temperature to the liquid nitrogen temperature. To aim.

[Means for solving the problem]

According to the present invention, a ceramic layer having a thickness of 10 to 300 μm, a noble metal layer having a thickness of 10 to 500 μm and a thickness of 100 are formed on a metal substrate.
Provided is an oxide superconducting laminate, which is characterized in that a Bi-Sr-Ca-Cu-O-based oxide superconductor layer having a thickness of up to 5000 μm is sequentially laminated. Further, a metal substrate is coated with ceramics, the ceramics is coated with a noble metal, a ceramics layer and a noble metal layer having a thickness of 10 to 500 μm are sequentially laminated, and then Bi-Sr-Ca-Cu- is formed on the noble metal layer. Provided is a method for producing an oxide superconducting laminated body, which comprises coating an O-based oxide superconductor raw material and firing.

 The present invention will be described in more detail below.

The metal substrate of the present invention is not particularly limited, but is a metal such as nickel, iron, stainless steel, hastelloy, inconel, incoloy, or enamel steel plate, and a metal material that does not melt or deform up to the firing temperature of the oxide superconductor is preferable. In addition to metals, ceramics such as zirconia and magnesia are commonly used as the base of oxide superconductors.
Metals can be in any shape and have the widest range of application and high industrial utility value. Therefore, it is industrially useful to obtain a stable superconducting superconductor on a metal substrate.

The ceramics layer which is the first layer of the intermediate layer in the present invention is formed on the metal substrate. The ceramic constituting the ceramic layer of the present invention may be appropriately selected depending on the type of the base metal and the oxide superconductor, and the like, and partially stabilized zirconia (hereinafter referred to as PSZ), stabilized zirconia,
Alumina, mullite, spinel, and ceramics such as silicon carbide, magnesia, and glass (including crystallized glass) can be used. Of these, the following glasses are particularly preferable as the ceramics for the intermediate layer.

A preferable glass for forming the ceramic layer of the intermediate layer has sufficient bonding strength for bonding the metal substrate and the noble metal layer of the second intermediate layer, and may cause deformation or outflow phenomenon during firing of the Bi-based superconductor. There is no particular limitation as long as it does not exist. One such type of glass is enamel glass, which is particularly desirable as the ceramic layer of the present invention.

In the present invention, the glass for enamel applied to the ceramic layer of the intermediate layer is not particularly limited to each composition of the main component. For example, SiO ₂ -Ba used for heat-resistant steel and heat-resistant alloys.
O-B ₂ O ₃ -ZnO-based composition or SiO ₂ -BaO-TiO ₂ based composition resistant enamel mainly composed _{of, SiO 2 -B 2 O 3 -Na} 2 O-Al 2 O
_3- K ₂ O-BaO composition steel plate enamel, SiO
Glass for glass lining or the like mainly composed of ₂ -B ₂ O ₃ -Na ₂ O-based composition are typical.

As the additive element or trace element to the composition of the enamel glass, various elements may be added or mixed as long as they have no great influence on the adhesion to the metal and the melting point.

The ceramic intermediate layer can be coated by any method such as plasma spraying, gas spraying, spray coating, brush coating, slurry dipping, and sputtering. Particularly, a thermal spraying method such as plasma spraying or gas spraying is preferable because it has excellent adhesion to the metal substrate and a relatively thick and stable intermediate layer can be obtained.

The thickness of the ceramic intermediate layer is in the range of 10 to 300 μm. When the thickness is less than 10 μm, the thickness becomes nonuniform and it becomes difficult to obtain high adhesion.

The noble metal layer which is the second layer of the intermediate layer in the present invention is formed on the ceramic layer which is the intermediate first layer formed on the metal substrate. As the noble metal composing the noble metal layer of the present invention, any one of silver, gold, palladium and platinum or a combination of two or more thereof is used. Further, if necessary, an alloy of these noble metals and base metals may be used. For example, silver
The oxide superconductor formed on the noble metal layer is Bi-Sr-Ca.
In the case of a —Cu—O-based oxide superconductor, the superconducting characteristics such as the critical current density are improved, so that an excellent effect can be obtained.

The noble metal layer can be formed on the ceramic layer by a method such as applying a noble metal paste, plating, pressure bonding with a metal foil, CVD, sputtering, or decomposition of a noble metal compound. In this case, for example, it may be formed by performing a heat treatment as required by a paste coating method.

The thickness of the noble metal layer is 10 to 500 μm, preferably 20 to 200
μm. Even if the thickness exceeds 500 μm, the effect of stabilizing the superconductor layer does not increase, but the cost increases. On the other hand, when the thickness is less than 10 μm, non-uniformity occurs and the adhesion between the ceramic intermediate layer and the noble metal intermediate layer decreases, or the noble metal layer breaks and the superconductor reacts at the interface between the ceramic layer and the metal substrate, It is difficult to obtain a good oxide superconductor-metal composite. Furthermore, when the oxide superconducting laminate, which is an oxide superconductor-metal composite, is cooled to liquid nitrogen temperature and used, if it is thinner than 10 μm, peeling occurs between the noble metal and the ceramic layer due to the difference in thermal expansion of the constituent materials. On the other hand, when it is 10 μm or more, the stress caused by the difference in thermal expansion is absorbed by the noble metal layer, so that a stable oxide superconducting laminate can be formed.

The oxide superconductor in the present invention includes Bi-Sr-Ca.
An example thereof is a -Cu-O-based compound having a multi-layer perovskite structure. By using a Bi-Sr-Ca-Cu-O system, it can be preferably applied to the use as a magnetic shield material.

In the present invention, the oxide superconductor layer may be formed by spray coating or powder coating using an oxide superconductor raw material powder, or a green body of a molded body obtained by molding the oxide superconductor raw material powder by a doctor blade method. Alternatively, it may be formed by adhering a sintered body that is fired to exhibit superconducting properties.

As the raw material powder of the above oxide superconductor, powders of metal oxides such as yttrium, scandium, lanthanum, copper, barium, bismuth, strontium and calcium, nitrates, carbonates, hydroxides and metal alkoxides are oxidized by firing. A powder that is compounded to form a superconductor, a powder that has a main crystal phase that is calcined at 800 to 950 ° C that consists of an oxide superconducting phase, and that is calcined at 400 to 800 ° C and that exhibits superconducting properties by firing. The product powder, the powder blended to form the oxide superconductor by firing is melted at high temperature, the powder that has been crushed after quenching, the oxide frit powder that develops superconducting properties by firing again, and the like. In these raw material powders, any one kind or a mixture of two kinds or more belonging to each of the above, or the above, and, and, and / or of The mixtures according to combined, above, and ,,
Any powder selected from and / or a mixture of and and and a mixture of the above, and, can be used.

The thickness of the oxide superconductor layer is 100 to 5000 μm, preferably 200 to 2000 μm. When it is thicker than 5000 μm, the superconductor layer is easily peeled off, and when it is thinner than 100 μm, the thickness becomes non-uniform and sufficient superconducting properties cannot be obtained.

In the present invention, as described above, after forming a layer of the oxide superconductor raw material on the intermediate layer consisting of the ceramic layer and the noble metal layer on the metal substrate, it is dried and fired to form the metal substrate, the ceramic layer and the noble metal layer. It is possible to obtain an oxide superconducting laminate in which the two-layer intermediate layer and the oxide superconducting layer are integrated. In this case, in the formation of the oxide superconductor layer, when an organic binder or an organic solvent was used for slurry coating or the like, heat treatment was performed in an oxygen-containing atmosphere at 500 to 930 ° C. for a certain period of time as a pretreatment before firing, and the amount of residual carbon Is preferably less than 0.5% by weight.

The firing in the present invention is performed in an atmosphere of oxygen or an oxygen-containing gas in air. The firing temperature may be appropriately selected depending on the type of the superconductor raw material and the desired superconductor, but generally it is 850 ° C. or higher.

The oxide superconducting laminate of the present invention is one in which an intermediate layer of ceramics and a noble metal is formed on a metal substrate, and an oxide superconducting layer is formed on the intermediate layer to integrate the two layers. The intermediate layer consisting of acts synergistically on both the metal substrate and the oxide superconductor layer formed on the outer surface. Therefore, the oxide superconducting laminate of the present invention,
Each layer on the metal substrate is stabilized, and peeling or cracking does not occur even if it is repeatedly used in liquid nitrogen that exhibits superconducting properties. Further, regardless of the type of the superconductor, the metal substrate and the superconductor raw material do not react during firing. Furthermore, the superconducting property is also improved over that of the conventional one-layer intermediate layer. The reason for these is not clear, but the second
It is presumed that the precious metal intermediate layer diffuses and penetrates into both the first ceramic intermediate layer and the oxide superconductor layer, and contributes to stabilization and improvement of superconducting properties.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to this embodiment.

Example 1 PSZ powder was plasma sprayed onto the surface of a 100 × 100 × 1.0 (mm) flat plate-shaped SUS430 stainless steel substrate roughened by sandblasting with alumina abrasives, and then 200
A μm PSZ intermediate layer was formed. Furthermore, silver (Ag) paste was applied on the PSZ intermediate layer and dried at 80 ° C for 1 hour.
Heat treatment at 0 ℃ for 10 minutes to form an Ag intermediate layer with a thickness of about 30 μm.
A metal substrate having an intermediate layer composed of two layers of SZ layer and Ag layer was obtained. Then, powders of Bi ₂ O ₃ , SrCO ₃ , CaCO ₃ and CuO having an average particle diameter of 3 μm were prepared in a molar ratio of 1: 2: 1: 2, mixed in distilled water, and then in air at 800 ° C. for 10 hours. Calcined in ZrO ₂ boulders in ethanol for 15 hours, the main crystalline phase is Bi ₂ Sr ₂ CaCU
A superconducting calcined powder having a ₂ O _y phase was obtained. 100g of this calcined powder
Toluene (15 g) and PVB (polyvinyl butyral) (0.2 g) were mixed to prepare a slurry, and this slurry was spray-coated on the metal substrate having the intermediate layer obtained above. After coating, it was dried at 80 ° C. for 1 hour. Then, spray coating and drying were repeated 4 times to form a coating film of about 300 μm on the second Ag intermediate layer.

The obtained laminated substrate, on which a two-layered intermediate layer and a layer made of superconducting calcined powder were formed on the metal substrate, was dried at 100 ° C for 1 hour, and then baked in an electric furnace at a maximum temperature of 910 ° C for 10 minutes to obtain a Bi-based electrode. A conductor oxide superconducting laminate was obtained.

A test piece was cut out from the obtained laminate, and the critical current density (Jc) was measured in a liquid nitrogen by using the DC four-terminal method. The result was 865 A / cm ² .

Further, another test piece was repeatedly cooled by immersion in liquid nitrogen and taken out at room temperature, but it was confirmed that the oxide superconductor layer and the intermediate layer of the laminate did not crack or peel, and that the adhesion was good. Was done.

Example 2 In the same manner as in Example 1, PSZ powder was plasma-sprayed on a flat SUS430 stainless steel substrate having a size of 100 × 100 × 1.0 (mm) to form a 100 μm PSZ intermediate layer. Furthermore that
Silver carbonate powder was sprinkled on the PSZ intermediate layer and heat-treated at 850 ° C. for 30 minutes to form a 25 μm-thick Ag layer, and a metal substrate having an intermediate layer composed of two layers of the PSZ layer and the Ag layer was obtained. Then, powders of Bi ₂ O ₃ , SrCO ₃ , CaCO ₃ and CuO having an average particle diameter of 3 μm were mixed with 1: 2:
Prepared at a molar ratio of 1: 2, distilled water 20 g to prepared powder 100 g,
0.2 g of PVA (polyvinyl alcohol) was added and mixed to form a slurry. This slurry was spray-coated on the metal substrate having the intermediate layer obtained above. After coating, it was dried at 100 ° C. for 30 minutes. After that, spray coating and drying are repeated 7 times, and the second Ag intermediate layer is coated with about 7 times.
A coating film of 600 μm was formed.

The laminated substrate in which two layers of the intermediate layer and the layer made of superconducting calcined powder were formed on the obtained metal substrate was dried at 110 ° C for 1 hour, and then baked in an electric furnace at a maximum temperature of 900 ° C for 10 minutes to obtain a Bi-based superconducting material. A body oxide superconducting laminate was obtained.

Jc measured in the same manner as in Example 1 was 720 A / cm ² .

Example 3 As in Example 1, spinel powder was plasma-sprayed on a flat plate-shaped SUS430 stainless steel substrate having a size of 100 × 100 × 1.0 (mm) to form a spinel layer having a thickness of 300 μm. Further, a gold (Au) foil having a thickness of 30 μm was heated and pressed onto the spinel layer to form an Au layer, and a metal substrate having a spinel layer and an intermediate layer of two Au layers was obtained. Then Bi: Sr: Ca: C
A Bi-based superconducting powder having u of 2: 2: 1: 2 was used, and tape molding was performed with a doctor blade. Place the obtained green sheet molded body on the metal substrate having the intermediate layer obtained above.
Firing was performed at 920 ° C. for 10 minutes to obtain a Bi-based superconductor oxide superconducting laminate.

Jc measured in the same manner as in Example 1 was 820 A / cm ² .

Examples 4-1 to 4-6 In the same manner as in Example 1, PSZ powder was plasma-sprayed on a flat plate-shaped SUS430 stainless steel substrate having a size of 100 × 100 × 1.0 (mm) to form a 200 μm PSZ intermediate layer. Then, a metal substrate having a first ceramics intermediate layer was produced.

Then, the Ag layer of the second intermediate layer is formed by a plating method and hot pressing of the foil, and a Bi-based superconductor layer is formed on the second intermediate layer in the same manner as in Example 1 to form an oxide superconducting laminate. Got the body Table 1 shows the mode of each of the obtained oxide superconducting laminates and the critical current density at 77K. As is clear from Table 1, each of the obtained laminates showed good superconducting properties.

Comparative Examples 1 to 4 In the same manner as in Example 1, PSZ powder was plasma sprayed on a flat plate-shaped SUS430 stainless steel substrate having a size of 100 × 100 × 1.0 (mm) to form a 200 μm PSZ intermediate layer.

On this PSZ intermediate layer, an Ag intermediate layer was formed by plating in the same manner as in Example 4. Thickness is 0, 1, 5 and 8μ
m. Further, a Bi-based superconductor layer was formed on this Ag intermediate layer in the same manner as in Example 1.

The laminated body obtained and the critical current density at 77K are
Shown in the table. As is clear from Table 1, the obtained laminates did not have good superconducting properties.

Example 5 Examples 4-1 to 4-6 and Comparative Examples 1 to 1 shown in Table 1
The thermal cycle test of each laminated body obtained in 4 was carried out.
In the cooling / heating cycle test, an operation in which a laminate left at room temperature (20 ° C.) was immersed in liquid nitrogen for 10 minutes and then taken out again at room temperature and allowed to stand was repeated 5 times, and peeling was observed.

The results are shown in Table 1. As is clear from Table 1, peeling occurred in the comparative examples in which the Ag intermediate layer had a thickness of 8 μm or less, but no peeling occurred in any of the examples.

Example 6 Diameter 50 mm, height 150 mm, thickness 1 mm On the outer surface of an Incoloy 825 cylindrical substrate, glass powder for enamel (45 wt% SiO-20w
t% TiO-15wt% B ₂ O ₃ -10wt% Na ₂ O-5wt% NiO-2.5wt% K
₂ O-2.5 wt% CuO) is dissolved in isopropyl alcohol solvent to a thickness of 100 μm by spray coating, and then a 100 μm thick Ag foil is wrapped and pressure-bonded to 900
Bonding was carried out by firing in air at 1 ° C. for 1 hour.

Furthermore, a slurry of Bi ₂ Sr ₂ CaCu ₂ O _x powder dissolved in an isopropyl alcohol solvent was spray-coated on an Ag foil to a thickness of 500 μm, and then partially melted in an oxygen atmosphere at 890 ° C. for 30 minutes and then 0.5 ° C./minute. 850 ℃
It was left for 15 hours for crystallization. Then, heat treatment was further performed at 400 ° C. for 20 hours in a nitrogen atmosphere.

The magnetic shield ability of the cylindrical body obtained as described above was measured by the magnetic shield ability measuring device shown in FIG. In FIG. 1, after arranging the cylindrical body 2 in the liquid nitrogen container 1, the container 1 is filled with liquid nitrogen, and an external magnetic field is applied by an electromagnet 3 to apply a magnetic field with a Gauss meter 4 installed in the cylindrical body 2. The maximum external magnetic field (magnetic shielding ability), which starts to increase from the background, was measured. As a result, the magnetic shield capacity was 10 gauss.

Further, when the cylindrical body was observed after the magnetic shield ability was measured, defects such as cracks and peeling did not occur.

〔The invention's effect〕

The present invention forms a two-layered intermediate layer consisting of a ceramics layer and a noble metal layer on a metal substrate, and in particular, forms a noble metal intermediate layer with a thickness of 10 μm or more, and forms an oxide superconductor layer thereon to oxidize it. Object superconducting laminate, good superconducting properties can be obtained, and a metal substrate and a ceramic layer,
It is possible to obtain a stable oxide superconducting laminate which has good adhesion between the ceramics layer and the noble metal layer and between the noble metal layer and the oxide superconducting layer, and can withstand a thermal cycle. Since the oxide superconducting laminate of the present invention uses a metal substrate, the substrate has a certain degree of freedom, and it is possible to obtain an oxide superconducting laminate having a plate shape, a curved surface shape, a cylindrical shape, or the like.

In the present invention, since an oxide superconductor having a desired shape can be easily obtained, application to a superconducting magnetic shield or the like becomes easy.

[Brief description of drawings]

 FIG. 1 is a schematic explanatory view of a magnetic shield capacity measuring device. 1 ... Liquid nitrogen container, 2 ... Cylindrical body, 3 ... Electromagnet, 4 ... Gauss meter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-305574 (JP, A) JP-A-63-279517 (JP, A) Japan Patent Office, “Layered Technology” Invention Association (October 1980) 20th) Page 43, Left column, Kazuo Fueki, Koichi Kitazawa "Chemistry of oxide superconductors" Kodansha (April 10, 1988), pages 55-58

Claims (3)

[Claims] 1. A ceramic layer having a thickness of 10 to 300 μm, a noble metal layer having a thickness of 10 to 500 μm, and a thickness of 100 to 5000 on a metal substrate.
An oxide superconducting layered product comprising a Bi-Sr-Ca-Cu-O-based oxide superconducting layer having a thickness of 1 μm. 2. The oxide superconducting laminate according to claim 1, wherein the ceramic layer is glass. 3. A metal substrate is coated with ceramics, the ceramics is coated with a noble metal, a ceramic layer and a noble metal layer having a thickness of 10 to 500 μm are successively laminated, and then Bi—Sr—Ca is deposited on the noble metal layer. A method for producing an oxide superconducting laminate, which comprises coating a Cu-O-based oxide superconductor raw material and firing the coated material.