JP2564598B2 - Oxide superconductor and manufacturing method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a superconductor and a method for producing the same, and more particularly to an oxide superconductor which prevents a change in the composition of components during heat treatment and a method for producing the same.

[Conventional technology]

Among the conventional oxide superconductor fabrication techniques, materials produced by the sputtering method, vapor deposition method, and thermal spraying method are difficult to develop superconducting properties as they are.
It is necessary to perform a heat treatment including a step of crystallizing at a temperature of one-half or more. For example, YBa ₂ Cu ₃ O ₇ with a critical temperature of about 90K
In the case of _δ oxide superconductor, JJAP, Vol.26.No11
(1987), PP.A.1907-L1909, 900 ℃
After maintaining in the temperature range above 1000 ° C for a certain period of time, it is gradually cooled to reach a crystal structure called an orthorhombic crystal to develop superconducting properties.

Appl.Phys.Lett., VoL.51 (1987), PP.858-PP.86
As also shown in 0, the elements constituting the superconducting material are deposited in several layers of several tens of nm by electron beam evaporation, and then heat treatment is performed at a temperature of 800 ° C to 850 ° C. After that, the superconductor is manufactured by cooling to room temperature at a slow rate of about 120 ° C. for 1 hour.

In any of the above methods, 800
The process involves holding the superconducting material at temperatures as high as ℃ to 1000 ℃, but during this heat treatment, the metal elements in the superconducting material evaporate at their respective evaporation rates. The composition of the material shifts before and after heat treatment. Especially when the surface area is very large compared to the volume, such as a thin film, this compositional deviation is serious. In the conventional technique, the amount of each element that evaporates during heat treatment is estimated by trial and error, a film having a composition in which the amount is added is formed, and then heat treatment is performed to manufacture a superconductor.

[Problems to be Solved by the Invention]

In the above-mentioned prior art, no consideration is given to the fact that the metal element forming the oxide superconductor evaporates in the step of performing the heat treatment, and it is necessary to change the starting composition every time the heat treatment conditions change. There is a problem that it takes a long time for trial and error to obtain a superconductor having an optimal composition. Also, since evaporation occurs only from the surface, due to the presence of significant compositional variations in the depth direction from the surface, the characteristics of the finally obtained superconductor are not stable,
There was also a problem that it was not practical as a technique used industrially.

The object of the present invention is to prevent the evaporation of various metal elements from the surface, to suppress the composition change before and after heat treatment, oxide superconductor that can easily develop stable superconducting properties and its manufacturing method. To provide.

[Means for solving the problem]

In order to achieve the above object, the oxide superconductor of the present invention is a thin film containing a superconductor constituent element formed on a substrate,
That is, on a thin film composed of Bi, Sn, Ca, and Cu, a deposit formed by forming a film made of a metal oxide that does not chemically react with the thin film and has oxygen permeability is ½ of the melting point of the thin film.
It is formed by holding the coating film after heat treatment in the above solid-phase temperature range.

The metal oxide used for forming a film on the thin film of the oxide superconductor that does not chemically react with the thin film and has oxygen permeability is, for example, stabilized zirconia.

Another oxide superconductor of the present invention is a thin film formed on a substrate and containing a superconductor-constituting element, that is, a thin film composed of Y or a rare earth, Ba and Cu, or bi, Sn,
On a thin film composed of Ca and Cu, a deposit formed by forming a film made of a substance that does not chemically react with the thin film and does not have oxygen permeability is used as a solid having a melting point of 1/2 or more of the thin film. After heat treatment in the phase temperature range, the coating film is removed, and the film is held in an oxygen atmosphere at a temperature range lower than 1/2 of the melting point of the thin film.

MgO is preferably used as a substance used for forming a film on the thin film of the oxide superconductor which does not chemically react with the thin film and has no oxygen permeability.

The method for producing an oxide superconductor according to the present invention comprises:
A first step of forming a thin film containing a superconductor-constituting element, a second step of forming a deposit on the surface of the thin film by forming a film made of stabilized zirconia that does not chemically react with the thin film, and the deposit Is heat-treated in a solid phase temperature range of ½ or more of the melting point of the thin film.

Furthermore, MgO or stabilized zirconia is used as the metal oxide for the coating.

Then, the coating in the second step becomes effective by coating or sealing the thin film.

Moreover, the thin film in the first step is preferably in an amorphous state.

The metal element of the thin film formed in the first step is composed of Y or a rare earth element, Ba and Cu, and the composition is effective if the molar ratio of Y or a rare earth element to Ba to Cu is 1: 2: 3. Target.

The metal element of the thin film formed in the first step is B
It may be composed of i, Sr, Ca and Cu.

Then, the heat treatment in the third step is preferably performed at least once in the temperature range of 700 to 1000 ° C.

Then, a film of stabilized zirconia is formed on the thin film formed in the first step, and heat treatment is performed at a temperature range of 700 to 1000 ° C., and then a temperature range of 600 to 300 ° C. is set for 2 hours in the cooling process. It becomes effective by holding the above.

In addition, MgO or A on the thin film formed in the first step
After forming a film consisting of at least one of l, Pt, Pd and Ni and performing heat treatment at least once in the temperature range of 700 to 1000 ° C., the film is removed and oxygen partial pressure of 0.1 atm or more is applied. You may hold | maintain for 30 minutes or more in the temperature range of 300-600 degreeC in oxygen atmosphere.

As an application of the oxide superconductor of the present invention, a superconducting coil having a structure in which a spirally formed superconducting thin film and a coating material are alternately deposited around a core material made of a metal oxide is used. is there.

In addition, there is a superconducting coil having a structure in which a wafer including a superconducting thin film formed on a substrate made of a metal oxide and a coating material coated on the thin film is stacked in a plurality of stages.

[Action]

In the oxide superconductor configured as described above,
When a deposit formed by forming a film on a thin film containing a superconductor constituent element is heat-treated in a solid phase temperature range of ½ or more of the melting point of the thin film, the film does not chemically react with the thin film, Oxygen is supplemented by the lack of oxygen because it prevents the evaporation of metal elements from the film to suppress the compositional change of this thin film and has oxygen permeability. Therefore, the thin film crystallized by this heat treatment and supplemented with oxygen exhibits stable superconducting properties.

Then, the metal element of the thin film containing the above-mentioned superconductor-constituting element is composed of Y or a rare earth element, an element consisting of Ba and Cu, or an element consisting of Bi, Sr, Ca and Cu, and thus has a superconducting property. Is effectively expressed.

Further, the substance for the film is preferably stabilized zirconia, which prevents evaporation of the metal element during heat treatment and allows oxygen to permeate.

In another oxide superconductor, when a deposit formed by forming a film on a thin film containing a superconductor constituent element is heat-treated at a solid phase temperature range of 1/2 or more of the melting point of the thin film, the film becomes the thin film. The chemical composition of the thin film is suppressed by preventing the evaporation of the metal element from the thin film without chemically reacting with the thin film. Then, the film is removed and kept in an oxygen atmosphere at a temperature range lower than 1/2 of the melting point of the thin film, so that the insufficient oxygen is replenished and the thin film exhibits stable superconducting properties.

The superconductivity of the thin-film metal element containing the above-mentioned superconductor-constituting element is Y or a rare earth element, an element consisting of Ba and Cu, or an element consisting of Bi, Sr, Ca and Cu. Is effectively expressed.

Further, the material for the film is preferably MgO, which prevents evaporation of the metal element during heat treatment.

Next, in the method for producing an oxide superconductor of the present invention, a thin film containing a superconductor constituent element is formed on a substrate in the first step of production, and the thin film is formed on the thin film in the second step. The thin film is crystallized by forming a coating film made of a substance that does not chemically react to form a deposit, and heat-treating the deposit in the solid phase temperature range of ½ or more of the melting point of the thin film in the third step. At the same time, the coating prevents vaporization of metal elements in the thin film during the heat treatment and suppresses the composition change of the thin film, so that the entire thin film has a uniform stoichiometric composition as intended. If this heat treatment temperature is less than half the melting point of the thin film containing the superconductor-constituting element, the crystallization of this thin film will be insufficient.

Then, the film formed in the second step has the above-mentioned function if it is made of a metal oxide.

It is effective to use MgO or stabilized zirconia as the metal oxide.

Further, the coating film of the second step may be formed by coating or sealing a thin film.

Then, the thin film in the first step is preferably in an amorphous state.

The metal element of the thin film formed in the first step is Y
Alternatively, it is composed of a rare earth element, Ba and Cu, and the composition of the thin film becomes effective when the molar ratio of Y or the rare earth element to Ba to Cu is 1: 2: 3.

The metal element of the thin film formed in the first step is Bi, S
It is also effective to be composed of r, Ca and Cu.

Then, the heat treatment in the third step is preferably performed in the temperature range of 700 to 1000 ° C. If the heat treatment temperature is lower than 70 ° C., the metal atoms of the thin film containing the superconductor-constituting element formed in the first step are not sufficiently diffused and completely crystallized.
If the temperature exceeds 00 ° C, the elemental composition of the metal oxide having superconducting properties is decomposed and sufficient superconducting properties cannot be obtained. Further, it is effective to perform this heat treatment once or more.

Also, when forming a film of stabilized zirconia on the thin film formed in the first step, since these substances have good oxygen permeability, after heat treatment at 700 to 1000 ℃, 600 ~ Even if the temperature range of 300 ° C. is maintained for 2 hours or more, oxygen is supplied to the thin film through the film, so that the stoichiometric composition is uniform as intended. At this time, 600 ℃
If held over, the metal element may evaporate,
On the other hand, if the temperature is lower than 300 ° C, the amount of oxygen supplied decreases. If the time of holding in this temperature range is less than 2 hours, the oxygen supply amount may be insufficient.

When a thin film formed of MgO or at least one of Au, Pt, Pd and Ni is formed on the thin film formed in the first step, since these substances have poor oxygen permeability, 700 Even if the heat treatment is performed at least once in the temperature range of up to 1000 ° C. for complete crystallization, oxygen may not be sufficient in the thin film, so that good superconducting properties may not be exhibited. Therefore, by removing this coating after this heat treatment and holding it in an oxygen atmosphere with an oxygen partial pressure of 0.1 atm or higher in the temperature range of 300 to 600 ° C for 30 minutes or more, the metal component composition of the thin film is not changed. Since oxygen can be supplied, a uniform stoichiometric composition as intended can be obtained. When the oxygen partial pressure of the oxygen atmosphere is less than 0.1 atm, oxygen is not sufficiently supplied to the thin film, and even when the temperature is kept in the temperature range of 300 to 600 ° C. for less than 30 minutes, oxygen is not sufficiently supplied. If the temperature exceeds 600 ° C, the metal of the thin film may evaporate, and if the temperature is lower than 300 ° C, the oxygen supply amount decreases.

Next, for the use of the oxide superconductor of the present invention, a superconducting thin film formed in a spiral shape and a coating material are alternately deposited around a core material made of a metal oxide. A superconducting coil, which has superconducting characteristics at a critical temperature or lower.

A thin film having superconducting properties formed on a substrate made of a metal oxide, and a wafer made of a coating material coated on the thin film, a superconducting coil having a structure in which a plurality of layers are stacked, It has superconducting properties below the critical temperature.

〔Example〕

The present invention heat-treats a deposit formed by forming a coating film made of a substance that does not chemically react with the thin film on a thin film containing a superconductor constituent element formed on a substrate, and depositing a metal from the coating film during the heat treatment. An oxide superconductor that exhibits stable superconducting properties by preventing the element from evaporating and suppressing its compositional change, and a method for producing the same.

In particular, the oxide superconductor is an R-Ba-Cu-O-based (R
Is Y or the following rare earth elements: Nd, Sm, Eu, Gd, Dy, Ho, Er,
In the case of Tm, Yb, Lu, La), heat treatment is performed in a temperature range of 700 ° C. or higher and 1000 ° C. or lower in a state in which a film that prevents the metal of the constituent elements from evaporating is formed. At this time, when the coating is stabilized zirconia or Ag, it allows oxygen to permeate, so it is a treatment of only slow cooling in an oxygen atmosphere, and the coating is MgO, Au, Pt, Pd or Ni. In this case, an oxide superconductor with better characteristics can be obtained by removing the coating film and then holding it in a temperature range of 300 ° C. or higher and 600 ° C. or lower for 30 minutes or longer.

In addition, the elemental composition of the oxide superconductor is the above-mentioned R-Ba-
It was confirmed that the same effect can be obtained even in the case of other than Cu-O type.

First, in the R-Ba-Cu-O-based oxide superconductor, R is Y
In the case of, the composition is represented by YBa ₂ Cu ₃ O ₇ _δ (0 ≦ δ ≦ 1) and has an oxidation-defective triple perovskite crystal structure. A slight change in the oxygen content and crystal structure has a great influence on the superconducting properties, so to make a superconductor with the best properties, the mode ratio of Y, Ba, Cu is 1: 2: Strictly control to 3 and oxygen content 0 ≦ δ ≦ 0.
It is necessary to control within the range of 3 and to perform complete crystallization.

On the other hand, even if a material with a Y, Ba, Cu ratio close to 1: 2: 3 is produced by such a method as sputtering, vapor deposition, or thermal spraying, the superconducting properties will not be manifested when the film is formed. Or, even if it showed superconducting properties, stable superconducting properties could not be obtained, such as a low critical temperature. The reason for this is that the above-mentioned conditions necessary for obtaining superconducting properties, especially complete crystallization, are not satisfied when the film is formed.

Therefore, after film formation, in the substance containing the superconductor constituent elements,
Heat treatment is performed at a temperature above the temperature at which Y, Ba, and Cu atoms can be diffused and completely crystallized, and below the temperature at which Y Ba ₂ Cu ₃ O ₇ _δ decomposes, and Therefore, it is necessary to completely regularize the arrangement of Cu atoms. It is generally known that this temperature range is from 700 ° C to 1000 ° C, but when heat treatment is performed at such a high temperature, the constituent elements evaporate, especially Cu evaporates from the surface of this substance. This is also a well-known fact.

Therefore, in order to prevent evaporation of the constituent elements from the surface,
Considering the method of heat treatment with the film formed on the surface, the properties of the film material are examined by focusing on two points: low chemical reactivity with superconductor and close thermal expansion coefficient. Advanced. As a result, finally stabilized zirconia, Mg
It was discovered that O, Ag, Au, Pt, Pd or Ni satisfies the above conditions as a coating material, and it was concluded that the thickness of the coating is preferably 10 nm or more and 10 μm or less.

As described above, when the superconducting material is YBa ₂ Cu ₃ O ₇ _δ, the value of δ is 0 ≦ in order to exhibit good superconducting properties.
It is necessary that δ ≦ 0.3, but at a high temperature of 700 ° C. or higher, the value of δ becomes larger than 0.4, and if Y Ba ₂ Cu ₃ O ₇ _δ is cooled below this temperature range while it cannot absorb oxygen. , The superconducting property becomes worse. Therefore, when MgO, Au, Pt, Pd or Ni, which has poor oxygen permeability, is used as a film, it is heat-treated at a temperature of 700 ° C or higher for complete crystallization and then slowly cooled or low-temperature. In many cases, the superconducting property is not good even if the heat treatment is performed at the temperature of 1 to suppress the change of the stoichiometric composition other than oxygen. However, in this case, after completely crystallizing the film, the film is removed, and heat treatment for oxygen supply is performed at a low temperature that does not affect the composition to stabilize the superconductor with good characteristics. Obtainable. On the other hand, when stabilized zirconia or Ag is used for the coating, these substances have good oxygen permeability, so 70%
After heat-treating at a temperature of 0 ° C. or higher, it is possible to obtain a superconductor having good characteristics simply by slowly cooling it.

The details of the embodiment of the present invention will be described below with reference to FIGS.

First Embodiment FIG. 1 shows the basic sectional structure of an oxide superconductor according to the present invention. The substrate 1 is made of MgO single crystal, and the superconducting thin film 2 formed thereon is Y ₁ Ba ₂ Cu ₃ O ₇ —δ, and δ is 0 to 1. The coating 3 formed on the thin film 2 is stabilized zirconia (YSZ).

The MgO coating layer also serving as the substrate 1 uses a MgO single crystal having a size of 5 mm × 20 mm × 0.5 mm, and has a (100) plane.

The Y ₁ Ba ₂ Cu ₃ O ₇ _δ film is formed by a sputtering method using a target of a mixture of Y, Ba, and Cu oxides, under the conditions of an accelerating voltage of 2 KV and an Ar gas of 1.0 × ^-2 torr. The film thickness was 5 μm.

The MgO film was formed by the sputtering method using a stabilized zirconia sintered body target under the same conditions as above, and the film thickness was
It was 0.2 μm.

In addition, three identical samples were prepared in order to examine the compositional shift before and after the heat treatment. One of them was used for composition analysis by ICPS as it was (Sample A) and the other two were subjected to heat treatment at 900 ° C for 1 hour in an oxygen stream and then left in the furnace at a cooling rate of 50 ° C for 1 hour. Cooled to room temperature. Then, one was subjected to composition analysis by ICPS (Sample B), and the last one was to measure the electric resistance by a usual four-terminal method after removing the film of stabilized zirconia (Sample C).

Note that ICPS is a high-frequency inductively coupled plasma optical emission analyzer, which is a device for analyzing the type and content of an element to be analyzed in a sample from the wavelength of an atomic spectrum obtained by emitting light in a plasma state. Therefore, it is suitable for trace analysis of inorganic substances.

Table 1 shows the molar ratios of Y, Ba and Cu obtained from the ICPS analysis results of sample A and sample B.

It can be seen that the method according to the invention eliminates compositional deviations before and after heat treatment. Further, as a result of measuring the electric resistance of the sample C, the electric resistance of this sample started to decrease rapidly at 92K and became O ohm at 87K.

Second Embodiment A sputtering method is used to deposit Y, Ba, and Cu on a silver tape having a thickness of 0.1 mm, a width of 5 mm, and a length of 30 mm in an amorphous state such that the composition ratio thereof is 1: 2: 3 in a molar ratio. Was deposited in the form of a film having a thickness of 5 .mu.m, and an Ag film having a thickness of 1 .mu.m was further formed thereon by a sputtering method. This is annealed in a pure oxygen stream for 1 hour at 900 ° C and then 50 ° C for 1 hour.
It cooled to room temperature at the cooling rate of. This sample is a normal 4
When the electric resistance was measured by the terminal method, the resistance began to decrease rapidly at 91K and became O ohm at 86K.

Third Example Ln, Ba, Cu was formed on a MgO single crystal substrate by a sputtering method using a target of a mixture of oxides of Ln, Ba, Cu.
An amorphous film having a composition ratio of 1: 2: 3 was deposited to a thickness of 5 μm, and a MgO film was deposited thereon to a thickness of 0.1 μm by a sputtering method. (here
Ln is Y, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu, La).

Hold this in an oxygen stream at 900 ° C for 1 hour, and
It cooled to room temperature at the cooling rate of 00 degreeC. Then the top layer
The MgO film was removed, and then kept at 400 ° C. for 3 hours in a pure oxygen stream, and then cooled at room temperature for 3 hours.

Table 2 shows the critical temperatures (temperatures at which the resistance becomes 0 ohm) obtained by measuring the electrical resistance of this sample by the ordinary four-terminal method.

The measurement result shows a good value of 65 to 87K.

Fourth Example Under the same conditions as those of the first example, 5 μm of Y ₁ Ba ₂ Cu ₃ O _{7 —} δ in an amorphous state was deposited on a MgO single crystal substrate, and this was coated with various substances. The results of the heat treatment are shown in Table 3.

In the heat treatment pattern A, the coated film is heated at a heating rate of 200 ° C./h and kept at 900 ° C. for 1 hour.
Then, a heat treatment method of cooling to room temperature at a temperature decrease rate of 50 ° C./h is shown. The heat treatment pattern B is a heat treatment in which the coating is removed after the heat treatment pattern A is applied, the temperature is raised to 600 ° C. at a heating rate of 200 ° C./h, cooling is immediately started, and the cooling is performed to room temperature at a cooling rate of 100 ° C./h. Show the method. However, the atmosphere during the heat treatment was 1 atm of pure oxygen. Also, the difference in composition before and after heat treatment is
The composition of the film after heat treatment is represented by the value of (| 3-y | / 3) +100 when it is expressed as YBaxCuyO ₇ _δ as a result of ICPS analysis, and the critical temperature is measured by the ordinary four-terminal method to measure the electric resistance. It shows the temperature when the resistance becomes zero.

Fifth Example Using a target obtained by baking and hardening a mixed powder of Bi ₂ O ₃ , CaO, SrO and CuO, the amorphous BiSrCaCu was formed on the MgO single crystal substrate under the same sputtering conditions as those shown in the first example. _Two to two
μm deposited and 0.2μm of stabilized zirconia on top
And keep it in the air at 880 ℃ for 1 hour, then 50
It was cooled to room temperature at a cooling rate of ° C / h. When the electric resistance of the film was measured by the usual four-terminal method, the resistance became zero at 78K.

Sixth Example Using a stabilized zirconia cylinder having a diameter of 1 cm and a length of 3 cm,
A superconducting coil was manufactured by the procedure shown in FIGS. 2A to 2E.

On the outer circumference of the rotated cylindrical core member 8 in FIG.
Under the same conditions as those shown in the embodiment, an amorphous YBa ₂ Cu ₃ O _{7 —} δ film 4 is deposited as shown in FIG. 2B, and an Ag film 3 is further deposited thereon to a thickness of 5 μm. Then the
As shown in the 2D figure, a part of this composite layer is removed so that the YBa ₂ Cu ₃ O ₇ _δ layer film 4 and the Ag layer film 3 form a coil. As shown, the above steps of depositing stabilized zirconia
As a cycle, this was repeated 3 times. Then, this coil was heat-treated at 900 ° C. for 1 hour in an oxygen stream of 1 atm and cooled to room temperature at a cooling rate of 10 ° C./h to obtain a superconducting coil. This superconducting coil is made of liquid nitrogen 77
When cooled in K and passed a current, a superconducting current flowed to 0.1 A. An overview of this coil is shown in FIG. First
FIG. 4A is a perspective view and FIG. 4B is a sectional view.

Seventh Example As shown in FIGS. 3A to 3C, a thin film 2 of YBa ₂ Cu ₃ O _{7 —} δ was formed on a substrate 1 of stabilized zirconia having a diameter of 2 cm, and a film 3 was formed using the stabilized zirconia, Wafers were produced by the method according to the example, and three wafers were stacked and heat-treated in an oxygen stream at 900 ° C. for 1 hour, and then cooled to room temperature at a cooling rate of 10 ° C./h.

The thin film having superconducting properties in this superconducting coil is
The thickness was 5 μm and the width was 1 mm, but at 77K, the superconducting coil could pass a superconducting current of 0.2A.

〔The invention's effect〕

Since the present invention is configured as described above, it has the following effects. This oxide superconductor is formed by forming a film on a thin film containing a superconductor constituent element and heat-treating the film, and the metal of the constituent element evaporates from the thin film during the heat treatment. To suppress the change in the composition of the thin film and to permeate oxygen to supplement the shortage of oxygen in the thin film, so that stable superconducting properties can be easily expressed.

And, the thin film containing the superconductor constituent element is composed of Y or a rare earth element, Ba and Cu, or Bi, Sr, Ca.
Even if it is composed of Cu and Cu, superconducting properties can be exhibited.

Further, if the material of the coating is stabilized zirconia, it prevents evaporation of the metal from the thin film during heat treatment and allows oxygen to permeate to replenish the oxygen deficiency of the thin film, thus providing stable superconducting properties. Can be expressed.

Another oxide superconductor is formed by forming a film on a thin film containing superconductor constituent elements and heat-treating the film. To suppress the change in the composition of the thin film, and
After the heat treatment, the film is removed and the thin film is supplemented with oxygen, so that stable superconducting properties can be easily exhibited.

The thin film containing the superconductor-constituting element can exhibit superconducting properties even if it is made of Y or a rare earth element, Ba and Cu, or Bi, Sr, Ca and Cu.

Further, when the substance of the coating film is MgO, the evaporation of the metal from the thin film during the heat treatment is prevented, so that stable superconducting properties can be exhibited.

Next, this oxide superconductor manufacturing method comprises a first step of forming a thin film on a substrate, a second step of forming a film on the thin film to produce a deposit, and a step of depositing the deposit. A third step of heat treatment, the heat treatment crystallizes the thin film, and further, the coating prevents evaporation of metal from the thin film during heat treatment, thereby suppressing a change in composition of the thin film. The uniform stoichiometric composition of the thin film as a whole is achieved, and thus a stable oxide superconductor can be easily manufactured.

The coating film formed in the second step is a metal oxide.
If it is composed of MgO or stabilized zirconia, it prevents evaporation of metal from the thin film and facilitates production of a stable oxide superconductor.

Further, even if the coating film formed in the second step is formed by sealing or sealing the thin film, the coating film can be easily formed.

Then, when the thin film formed in the first step is in an amorphous state, a thin film containing a superconductor constituent element can be easily formed.

Moreover, since the metal element of the thin film formed in the first step is composed of Y or a rare earth element, Ba and Cu, the composition of the thin film further has a molar ratio of Y or a rare earth element, Ba and Cu of 1 to 2. By setting the ratio to 2 to 3, a thin film containing a superconductor constituent element can be easily formed.

Furthermore, the metal element of the thin film formed in the first step is B
A thin film containing a superconductor-constituting element can be easily formed also by being composed of i, Sr, Ca, and Cu.

Further, since the thin film formed in the first step can be completely crystallized by performing the heat treatment in the third step once or more in the temperature range of 700 to 1000 ° C., the superconducting property can be easily exhibited.

Then, when a film of stabilized zirconia is formed on the thin film formed in the first step and heat treatment is performed at 700 to 1000 ° C.,
This film allows oxygen to permeate, supplies oxygen to the thin film, and by maintaining the temperature range of 600 to 300 ° C for 2 h or more during cooling, sufficient oxygen can be supplied. Since it can be maintained in a theoretical composition and can be completely crystallized, an oxide superconductor having stable superconducting properties can be easily manufactured with good reproducibility.

In addition, MgO or A on the thin film formed in the first step
When a coating film made of at least one of u, Pt, Pd and Ni is formed and heat-treated at 700 to 1000 ° C., this film has no oxygen permeability. Therefore, after performing this heat treatment once or more,
By removing the film and holding it in an oxygen atmosphere at 300-600 ° C for 30 minutes or more, sufficient oxygen is supplied to the thin film, so that the stoichiometric composition is as targeted and complete crystallization. Therefore, the thin film exhibits sufficient superconducting properties, and a stable oxide superconductor can be easily manufactured with good reproducibility.

Next, a superconducting coil using the oxide superconductor of the present invention has a structure in which a spirally formed thin film having superconducting properties and a coating material are alternately deposited around a core material. Since this thin film has stable superconducting properties, a high superconducting current could be passed.

Another superconducting coil has a structure in which wafers composed of a superconducting thin film formed on a substrate and a coating material coated on the thin film are stacked in a plurality of stages, and the thin film is a stable superconducting film. Since it has a conductive property, a high superconducting current could be passed.

[Brief description of drawings]

FIG. 1 is a schematic view showing a cross-sectional structure of an oxide superconductor according to the present invention, FIGS. 2A to 2E are explanatory views showing a procedure for producing a superconducting coil according to the present invention, and FIG. 3A is according to the present invention. A plan view of a wafer which is a superconducting coil component, FIG. 3B is a sectional view taken along the arrow 3B-3B in FIG. 3A, FIG. 3C is a sectional view taken along the arrow 3C-3C in FIG. 3B, and FIG. A sketch drawing showing a superconducting coil according to
FIG. 4B is a sectional view showing a sectional structure taken along a plane passing through the center of FIG. 4A. 1 ... Substrate, 2 ... Superconducting thin film, 3 ... Coating, 4 ... Thin film containing constituent elements of superconductor, 5 ... Coating material, 10 ... Superconducting coil.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location H01F 6/06 ZAA H01F 5/08 ZAA (72) Inventor Toshimi Matsumoto 4026 Kuji Town, Hitachi City, Ibaraki Prefecture Hitachi, Ltd., Hitachi Research Laboratory (56) Reference JP-A-1-105412 (JP, A) JP-A-63-261770 (JP, A) JP-A-63-52314 (JP, A) JP-A 64-64 72508 (JP, A) JP-A-64-19702 (JP, A)

Claims (18)

(57) [Claims] 1. A metal oxide having oxygen permeability, which does not chemically react with a thin film, which is formed on a substrate and which is composed of Bi, Sr, Ca, and Cu which are constituent elements of a superconductor. An oxide superconductor in which the above-mentioned film is retained after heat treatment of the deposit having the film formed thereon in a solid phase temperature range of ½ or more of the melting point of the thin film. 2. A deposit comprising a thin film containing a superconductor-constituting element formed on a substrate, on which a film made of stabilized zirconia that does not react with the thin film and has oxygen permeability is formed. An oxide superconductor holding the coating after heat treatment in a solid phase temperature range of ½ or more of the melting point of the thin film. 3. A substance which does not chemically react with the thin film and has no oxygen permeability on a thin film formed on a substrate and made of Y or a rare earth element, which is a constituent element of a superconductor, and Ba and Cu. The deposit formed with a film consisting of 1/2 of the melting point of the thin film
An oxide superconductor, which has been heat-treated in the above solid-phase temperature range, and after removing the coating film, kept in an oxygen atmosphere at a temperature range lower than 1/2 of the melting point of the thin film. 4. A substance which does not chemically react with the thin film formed on the substrate and is composed of Bi, Sr, Ca and Cu, which are constituent elements of the superconductor, and has no oxygen permeability. After heat-treating the deposit formed with a film in a solid phase temperature range of 1/2 or more of the melting point of the thin film, the film is removed, and the temperature is lower than 1/2 of the melting point of the thin film in an oxygen atmosphere. Oxide superconductor retained in the region. 5. A deposit formed by forming a film made of MgO, which does not chemically react with the thin film and has no oxygen permeability, on a thin film containing a superconductor constituent element formed on a substrate. After heat treatment in a solid phase temperature range of ½ or more of the melting point of the thin film, the coating is removed, and 1 / th of the melting point of the thin film in an oxygen atmosphere is removed.
Oxide superconductor kept at a temperature lower than 2. 6. A first step of forming a thin film containing a superconductor-constituting element on a substrate, and forming a film of stabilized zirconia having oxygen permeability without chemically reacting with the thin film on the thin film. A method for producing an oxide superconductor, comprising: a second step of producing a deposit; and a third step of heat treating the deposit in a solid phase temperature range of ½ or more of a melting point of the thin film. 7. A superconductor constituent element of Bi, Sr, Ca on a substrate.
A first step of forming a thin film of Cu and Cu; a second step of forming a deposit by forming a coating film of a metal oxide that does not chemically react with the thin film on the thin film; And a third step of performing heat treatment in a solid phase temperature range of ½ or more of the melting point, a method for producing an oxide superconductor. 8. Bi, Sr, Ca, and Bi formed in the first step
The method for producing an oxide superconductor according to claim 7, wherein the thin film made of Cu is in an amorphous state. 9. A first step of forming a thin film containing a superconductor-constituting element on a substrate, and forming a coating film of stabilized zirconia having oxygen permeability without chemically reacting with the thin film on the thin film. The second step of making a deposit and the deposit
A method for producing an oxide superconductor, comprising a third step of holding a temperature range of 600 to 300 ° C. for 2 hours or more in a cooling process after performing heat treatment in a temperature range of 700 to 1000 ° C. 10. The method for producing an oxide superconductor according to claim 9, wherein the thin film formed in the first step is in an amorphous state. 11. A first step of forming a thin film of Y or a rare earth element which is a superconductor constituent element, Ba and Cu on a substrate, and a film of stabilized zirconia which does not chemically react with the thin film on the thin film. And a second step of forming a deposit to form a deposit, and a third step of performing a heat treatment on the deposit in a temperature range of 700 to 1000 ° C. and then maintaining a temperature range of 600 to 300 ° C. for 2 hours or more in the cooling process. A method of manufacturing an oxide superconductor, comprising: 12. The oxide superconductor according to claim 11, wherein the thin film formed in the first step contains Y or a rare earth element, Ba and Cu in a molar ratio of 1: 2: 3. Body manufacturing method. 13. The oxide superconductor according to claim 12, wherein the thin film containing Y or rare earth elements, Ba and Cu in a molar ratio of 1: 2: 3 is in an amorphous state. Method. 14. A superconductor-constituting element of Bi, Sr,
A first step of forming a thin film of Ca and Cu, and a second step of forming a deposit on the thin film by forming a coating film of stabilized zirconia having oxygen permeability without chemically reacting with the thin film, A method for producing an oxide superconductor, comprising a third step of performing a heat treatment on the deposit in a temperature range of 700 to 1000 ° C. and then maintaining a temperature range of 600 to 300 ° C. for 2 hours or more in a cooling process. . 15. The thin film made of Bi, Sr, Ca and Cu,
15. The method for producing an oxide superconductor according to claim 14, which is in an amorphous state. 16. A thin film containing a superconductor-constituting element is formed on a substrate, and MgO, which does not chemically react with the thin film and has no oxygen permeability, or Au, Pt, Pd and Ni is formed on the thin film. After forming a film consisting of at least one of them, heat-treating at least once in the temperature range of 700 to 1000 ° C, and then removing the film, 300 to 60 in an oxygen atmosphere with an oxygen partial pressure of 0.1 atm or more.
A method for producing an oxide superconductor, which is characterized by holding at a temperature range of 0 ° C. for 30 minutes or more. 17. Bi, Sr, Ca and Cu as a superconductor element formed in a spiral shape around a core made of a metal oxide.
A superconducting coil having a structure in which a superconducting thin film made of an oxide containing oxide and a coating substance made of a metal oxide that does not chemically react with the thin film and has oxygen permeability are alternately deposited. 18. A superconducting thin film made of an oxide containing Bi, Sr, Ca and Cu as superconductor elements formed on a substrate made of a metal oxide, and a chemical reaction with the thin film coated on the thin film. A superconducting coil having a structure in which a plurality of wafers made of a coating material made of a metal oxide that does not exist and has oxygen permeability are stacked.