JP2002068892A - Superconductor comprising superconducting thin film formed on surface of alumina single crystal substrate and method of forming superconducting thin film on surface of alumina single crystal substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an epitaxial thin film comprising a rare earth metal and aluminum on the surface of an alumina single crystal substrate by dissolving a rare earth oxide and an aluminum-containing compound into a solvent, then stirring the mixture to obtain a uniform solution, coating the solution on the surface of the alumina single crystal, drying to form a thin film and heating/ firing the coated film, and to form a superconducting film on the single crystal alumina substrate by forming the superconducting film on the surface of the epitaxial thin film mentioned above, being used as an intermediate layer. SOLUTION: The epitaxial thin film of a multiple oxide having a compositional ratio of rare earth metal:aluminum:oxygen of 1:1:3 is obtained by dissolving a compound containing a rare earth metal into a solvent, then stirring the mixture to obtain a uniform solution, coating the solution on the surface of an alumina single crystal substrate, drying to form a thin film and heating/firing the coated thin film. The superconductor is constituted of a YBa2 Cu3O7 yttrium-based superconductor epitaxial thin film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a superconductor comprising a superconducting thin film formed on a surface of an alumina single crystal substrate,
And a method for manufacturing a superconductor in which a superconducting thin film is formed on the surface of an alumina single crystal substrate.

[0002]

BACKGROUND OF THE INVENTION It has been 14 years since the invention of a high-temperature oxide superconductor in 1986. In the meantime, research and development has been actively promoted, and it has reached the stage of practical use,
Multifaceted efforts are being devoted. In this technique, a large-area yttrium-based superconductor (YBa ₂ Cu ₃ O ₇ : hereinafter also referred to as YBCO) film is used for a microwave filter for mobile communication or a current limiter. In this respect, it has become an important key technology. At present, as a substrate of the film, lanthanum aluminate (LaAlO ₃ : hereinafter, L
Also called AO. ) Is used. The reason is LA
The lattice constant of O (3.79 angstroms when quasi-cubic) is close to that of YBCO (short side of the tetragonal layered perovskite structure is 3.82-3.89 angstroms), and the dielectric constant of LAO Since the ratio is relatively small, the dielectric loss of alternating current is small.
Generally, whether a microwave filter for mobile communication or a current limiter, its performance depends on the area of the superconducting film, so the demand and expectation for a large area will increase further in the future. Can be Currently, commercially available LAO single crystal substrates have a limit of 7 to 8 cm in diameter. If a single crystal substrate having a size larger than this, for example, a diameter of 10 to 30 cm is to be obtained, it is considered that there is no other choice but to use alumina (Al ₂ O ₃ ) as a material. Alumina is basically hexagonal, and YBCO is tetragonal with a layered perovskite structure. Therefore, as a method for matching the two, it is conceivable to use a square lattice arrangement of the R plane (012) of alumina. However, in this case, the length of one side of the square lattice is 3.49 angstroms, and Y
Since it is significantly different from that of BCO, it cannot be used as it is as a substrate. That is, when used directly as a substrate, it is difficult to manufacture an epitaxial YBCO film having a high critical current density thereon due to the mismatch of lattice constants. As a solution to this problem, it is necessary to take measures to alleviate the difference in lattice constant. For this purpose, it is conceivable to provide an intermediate layer between the substrate and the superconducting film. If used, the difference in lattice constant can be expected to be reduced. At this time, it is expected that an optimum intermediate layer can be selected by examining all rare earth metals in addition to lanthanum. Therefore, a composite oxide having a perovskite structure in which the ratio of rare earth metal: aluminum: oxygen is 1: 1: 3 has been receiving attention as an intermediate layer. When alumina is used as a substrate, there is a concern that aluminum as a component thereof reacts with barium as a component of YBCO, but rare earth metals have intermediate properties between barium and aluminum in terms of basicity. The presence of such an intermediate layer is also useful in that a chemical reaction occurring between both layers of the substrate and the superconducting thin film can be prevented during the heat treatment. Although there are complex oxides in which the composition ratio of rare earth metal: aluminum: oxygen does not become 1: 1: 3, they do not meet the purpose. Conventionally, attempts to form such an intermediate layer have included a sapphire substrate and an epitaxial GdA
The lO ₃ film, studies have been reported to be formed by sputtering (Mat.Res.Soc.Symp.Pro
c. Vol. 401 p357-362 (1996)
Materials Research Society
). In the sputtering method, a target compound is evaporated in a plasma state to form a film on the substrate surface. However, in such a method, when manufacturing a substrate of a superconducting thin film having a large area from the point of view of an apparatus, or when manufacturing a substrate of a superconducting thin film by continuous mass production, There is impossible. From such a point, this method cannot be used when manufacturing a large-area superconducting thin film. For these reasons, there is a need for a method for producing a large-area superconducting thin-film substrate, and in particular, a novel method for forming an epitaxial thin film on a single-crystal alumina substrate capable of producing a large-area superconducting thin-film substrate. ing.

[0003]

An object of the present invention is to provide a novel superconductor comprising a superconducting thin film formed on the surface of an alumina single crystal substrate, and a superconducting thin film formed on a surface of an alumina single crystal substrate. An object of the present invention is to provide a novel method for manufacturing a superconductor to be formed.

[0004]

Means for Solving the Problems The present inventors dissolve a rare earth oxide and an aluminum-containing compound in a solvent on the surface of an alumina single crystal plate, apply a uniform solution on the surface of the alumina single crystal plate, and dry it to form a thin film. When formed and fired,
An epitaxial thin film composed of a rare earth metal and aluminum can be formed, and when this epitaxial thin film is used as an intermediate layer and a superconducting film is formed on this surface, a superconducting film can be formed on a single crystal alumina substrate. The inventors have found out what can be done and completed the present invention.

According to the present invention, the following inventions are provided. (1) Alumina single crystal substrate, a rare earth metal-containing compound is dissolved in a solvent to form a uniform solution, coated and dried on the surface of the alumina single crystal, formed into a thin film, and heated and fired to obtain a rare earth metal: aluminum: A superconductor comprising a composite oxide epitaxial thin film having an oxygen composition of 1: 1: 3 and a YBa ₂ Cu ₃ O ₇ yttrium-based superconductor epitaxial thin film. (2) the rare earth metal is selected from yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium; A superconductor as described above. (3) The superconductor as described above, wherein the rare earth metal-containing compound is a compound selected from rare earth metal organic acid salts and rare earth metal acetylacetonates. (4) The superconductor as described above, wherein when the rare earth metal-containing compound is rare earth metal acetylacetonate, the solvent is trifluoroacetic acid or methanol containing abietic acid. (5) The superconductor as described above, wherein the heating and firing are performed at 1000 to 1600 ° C. (6) The superconductor as described above, wherein an aluminum-containing compound is added to the rare-earth metal-containing compound. (7) A rare earth metal-containing compound is dissolved in a solvent to form a uniform solution on the surface of an alumina single crystal substrate, applied to the alumina single crystal surface and dried, a thin film is formed, and the rare earth metal is obtained by heating and firing. : Forming a composite oxide epitaxial thin film having a composition of aluminum: oxygen of 1: 1: 3, and further forming a metal-containing compound selected from metal organic acid salts of Y, Ba, and Cu and metal acetylacetonate on the surface thereof. An organic solvent solution is prepared, made into a uniform solution, applied and dried on the epitaxial surface of the composite oxide, a thin film is formed, and heated and baked to obtain YBa ₂ Cu ₃ O.
_{7. A} method for producing a superconductor, comprising forming a ₇ yttrium-based superconducting thin film. (8) The rare earth metal is selected from yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. A method for producing a superconductor as described above. (9) The method for producing a superconductor as described above, wherein the rare earth metal-containing compound is a compound selected from a rare earth metal organic acid salt and a rare earth metal acetylacetonate. (10) The method for producing a superconductor as described above, wherein when the rare earth metal-containing compound is a rare earth metal acetylacetonate, the solvent is trifluoroacetic acid or methanol containing abietic acid. (11) Rare earth metal: aluminum: oxygen composition is 1:
The method for producing a superconductor as described above, wherein the heating and sintering at the time of forming the 1: 3 composite oxide epitaxial thin film is performed at 1000 to 1600 ° C. (12) The method for producing a superconductor as described above, wherein an aluminum-containing compound is added to the rare-earth metal-containing compound.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, an alumina single crystal substrate is used. In the present invention, finally, a superconducting thin film of yttrium or the like is formed on the surface of the substrate. A use of a superconducting thin film requires a substrate having a large substrate diameter, and a large alumina single crystal is required. In response to such a demand, it is possible to use single-crystal alumina having a suitably large diameter. The diameter of the alumina single crystal used may be as large as possible. When the alumina single crystal substrate is used, the alumina surface is polished as a pretreatment, and the orientation of the surface is as follows: A plane (110), C plane (001), R plane (0).
12) and M-plane (100).

Next, a solution of a compound containing a rare earth metal for forming an epitaxial thin film composed of a composite oxide composed of a rare earth metal and aluminum is formed on the surface of the single crystal as follows. Rare earth metals include Y, La, Ce, Pr, Nd, Sm, Eu, Gd,
It can be used by selecting from rare earth elements consisting of Tb, Dy, Ho, Er, Tm, Yb, and Lu. The rare earth metal-containing compound is dissolved in a solvent to form a uniform solution. Any rare earth metal compound can be used as long as it is uniformly dissolved in a good solvent and a film is formed on the substrate. Generally, as such a rare earth metal-containing compound, a compound having a relatively large organic group and thereby easily forming a film is used. Preferable specific examples include rare earth metal organic acid salts such as rare earth naphthenate and rare earth 2-ethylhexanoate or rare earth metal acetylacetonate. The formation of the rare earth metal aluminum composite oxide is achieved by a chemical reaction between the rare earth metal oxide generated by thermal decomposition of the rare earth metal-containing compound and the alumina of the substrate. If alumina is insufficient for any reason in this reaction, the aluminum oxide-containing compound can be added to the starting material solution. In other words, an aluminum-containing compound can be added to the rare-earth metal-containing compound as needed.

[0008] As described above, the solvent used for dissolving the rare earth-containing compound must be capable of dissolving the compound in a uniform state. It is necessary that the solvent has excellent wettability with respect to water and that the solvent can be easily volatilized and removed by drying and heat treatment. When using a rare earth metal organic acid salt as the rare earth metal-containing compound, it is preferable to use a nonpolar solvent such as toluene as the solvent. On the other hand, when rare earth metal acetylacetonate is used as the rare earth metal-containing compound, the solvent is preferably a polar solvent. An alcohol such as methanol is used as such a polar solvent. When using methanol, it is preferable to further add trifluoroacetic acid. The content of trifluoroacetic acid is 0.1-1
0 mol%. Further, if necessary, propionic acid, abietic acid and the like can be added. By adding such a solvent, the film forming property can be improved.

If the rare earth-containing compound is mixed and dissolved in a solvent at an excessively low concentration, an expected film cannot be formed when applied to the surface of single crystal alumina.
On the other hand, if the concentration is too high, the film cannot be deposited uniformly, and the expected film formation cannot be obtained. Considering this, the concentration is 0.05-1.0 mol
/ L (liter), preferably 0.1-
0.5 mol / l (liter).

Next, a solution containing the rare earth-containing compound is applied on the surface of the single crystal alumina. As a coating method, a known method such as a dipping method, a spray method, a brush coating method, and a spin coating method is appropriately used. After the application, if necessary, a drying treatment is performed to adhere the rare earth-containing compound on the single-crystal alumina substrate on the single-crystal alumina substrate. The pressure is set at normal pressure or reduced pressure. Air can be present. A heating drying oven can be used for heating for drying. When the heating and drying process is completed,
A thin-film dried product is formed on the surface of the single-crystal alumina. The drying step can be performed continuously with the subsequent heating and firing step.

Next, the thin film layer on the substrate obtained by drying the rare earth-containing compound is heated and fired. In the heating and sintering process, the rare earth-containing compound is thermally decomposed and changes to a rare earth oxide, and the rare earth oxide undergoes a chemical reaction with the alumina of the substrate to produce a rare earth metal aluminum composite oxide as a target product. It is effective to perform temporary baking before performing full-scale heating and baking. The conditions for calcination are as follows:
A temperature lower than the heating and firing temperature in air is employed. Specifically, a condition in a temperature range exceeding 150 ° C. and less than 1000 ° C. is employed. Specifically, by performing the treatment at a temperature of about 500 ° C. for 30 minutes, pre-baking was performed to decompose and remove the organic components. Thereafter, the following full-scale heat treatment was performed. The heating and firing conditions for producing the composite oxide are as follows:
In air, at a temperature of 1000-1600 ° C. for 30 minutes-10
Process over time. In order to generate a composite oxide having a rare earth metal: aluminum: oxygen ratio of 1: 1: 3, which is a target product, among the above conditions, preferably 1100 to 1300 ° C., more preferably 11
Conditions of 50-1250 ° C. for 30 minutes-10 hours are employed. By treating under these conditions, a target perovskite cultivated composite oxide having a rare earth metal: aluminum: oxygen ratio of 1: 1: 3 can be obtained.
When the heating conditions such as a temperature that does not reach the above temperature range or a short heating time are insufficient, a desired substance having a perovskite structure in which the composition ratio of rare earth metal: aluminum: oxygen is 1: 1: 3 is obtained. Can not do. On the other hand, if the heating conditions exceed this temperature range or the time is long, the garnet structure in which the composition ratio of rare earth metal: aluminum: oxygen is 3: 5: 12, or 1:11:18 or 1:12: In some cases, a hexagonal crystal of 19 or the like may appear, and a target substance having a perovskite structure cannot be obtained. The pressure is pressurized,
It can be carried out under any of normal pressure and reduced pressure conditions. The reaction can be carried out in the presence or absence of air or oxygen. A firing furnace is used for heating and firing. As the firing furnace, a tunnel type continuous furnace or a batch type firing furnace can be used. In addition, 1000-16
500 ° C. as a step before heating and baking at 00 ° C.
Precalcination before and after can be appropriately combined.

Rare earth and aluminum obtained by heating and sintering
Epitaxial Thin Film of Complex Oxide Oxide
Is, for example, as follows. As rare earth metals, L
When a is used, LaAlO₃, Gd
Is GdAlO₃, When Sm is used, SmAlO₃,
When Y is used, YAlO₃, When using Ce
CeAlO₃, Pr when using PrAlO ₃, N
When d is used, NdAlO₃, Eu
Is EuAlO₃, When Tb is used, TbAlO₃,
When Dy is used, DyAlO₃, Ho
Has HoAlO₃, ErAl when Er is used
O₃, When Tm is used, TmAlO₃, Yb
YbAlO₃, LuA when using Lu
10₃Respectively can be obtained. These composite oxides
Regarding the orientation of the film, oxygen on the surface of single-crystal alumina
The filling direction of the composite oxide matches the filling direction of oxygen
As the crystal grows,
This result can be confirmed by X-ray analysis.
You.

The composite oxide of rare earth and aluminum obtained in this manner has a similar lattice constant to that of single crystal alumina. Therefore, an yttrium-based composite oxide is formed on the composite oxide layer of rare earth and aluminum. When the superconductor of (1) is formed, the composite oxide composed of rare earth and aluminum functions as an intermediate layer, and the superconductor can be stably formed on the surface of the single crystal alumina substrate.

Next, an yttrium-based superconducting thin film is formed on the surface of the epitaxial thin film made of the rare earth and aluminum complex oxide formed on the alumina single crystal substrate. First, in order to form a superconducting thin film, a solution for forming an yttrium-based superconducting thin film is prepared. A metal compound of Y, Ba, and Cu, for example, a metal-containing compound selected from metal organic acid salts and metal acetylacetonates is used, and a solution of the organic solvent is prepared using an organic solvent to obtain a uniform solution. This solution is applied on the epitaxial surface of the composite oxide and dried,
A thin film is formed and baked under heating to obtain YBa ₂ Cu ₃
An yttrium-based superconducting thin film made of O ₇ is formed. As the yttrium-based superconducting thin film and the method for producing the same, the superconducting thin film and the method for producing the same by the present inventors can be applied.
94, The Chemical Society of Japan, 1997 (1) 11-23 (19
97)).

The metal compound for forming the yttrium-based superconducting thin film made of YBa ₂ Cu ₃ O ₇ is as follows.
After dissolving in a solution, it is applied as a film, dried and heated and baked to form a superconducting thin film. Specifically, for example, compounds such as metal alkoxides, metal acetylacetonates, metal nitrates, metal organic acid salts, inorganic acid salts such as carbonates, chelate compounds, metal halides and hydroxides can be used. . When a metal alkoxide is used, specific compounds include methoxide, ethoxide, propoxide,
Examples thereof include i-propoxide and butoxide. Metal alkoxides include, as specific compounds,
Cu methoxide, Cu ethoxide, Ba ethoxide, B
a isopropoxide, Y methoxide, Y ethoxide, Y
Isopropoxide and the like can be mentioned. When metal acetylacetonate is used, Cu acetylacetonate, Y acetylacetonate, Ba acetylacetonate and the like can be mentioned. As metal nitrates, B
a nitrate and the like. As organic acids of metal organic acid salts, naphthenic acid, 2-ethylhexanoic acid, caprylic acid, stearic acid, lauric acid, butyric acid, propionic acid, oxalic acid, citric acid, lactic acid, phenol, catechol, benzoic acid, salicylic acid, Organic acids such as EDTA can be mentioned. Examples of metal organic acid salts include yttrium butyrate, yttrium naphthenate, barium butyrate, barium naphthenate, copper butyrate, copper naphthenate, copper propionate, and copper lactate.

An organic solvent is used as the compound used to dissolve the metal compound for forming the superconducting thin film. This solvent can be appropriately selected and used as long as it can dissolve the metal compound. Specific organic solvents include hexane, octane, benzene,
Hydrocarbons such as toluene, methanol, ethanol,
Examples thereof include alcohols such as propanol, butanol and amyl alcohol, ketones such as acetone and methyl ethyl ketone, and ethers such as diethyl ether and dimethyl ether. The concentration of the metal compound in the solution may be within a range in which the metal compound can be dissolved. Although it depends on the type of the solvent, it is generally in the range of 3 to 40% by weight.

The metal compound-containing solution obtained by dissolving the metal compound in the organic solvent is applied on the surface of an epitaxial thin film of a composite oxide composed of a rare earth metal and aluminum formed on the surface of an alumina crystal substrate. For the application, a conventionally known method can be used as an application means. Specifically, immersion method, spray method,
A spin coating method, a brush coating method, and the like can be given. The thin film material thus formed is dried.
Conditions for removing the solvent are employed for drying. The drying operation is performed under normal pressure or reduced pressure under a temperature condition of room temperature or higher.

Heating a thin film containing a metal organic compound formed on the surface of an epitaxial thin film of a complex oxide comprising a rare earth metal and aluminum formed on the surface of the alumina substrate support. Baking treatment. The heat calcination is performed under conditions where the metal-containing compound can form a composite oxide. Generally 500-10
The condition of 00 ° C. is adopted. The metal-containing compound is 200-
Decomposition or oxidation reaction is performed under a temperature condition of less than 500 ° C. Formation and crystallization of superconducting composite oxide is 500-1
At 000 ° C. From such a thing, the heating and firing initially proceed at a low temperature of less than about 200-500 ° C,
Thereafter, the heat treatment can be performed under a higher temperature condition of 500 to 1000 ° C. The heating and firing can be performed in the presence of oxygen and air. It is also possible to carry out in an atmosphere containing no oxygen. The pressure can be reduced, normal, or increased.

As a result, an epitaxial thin film of a composite oxide composed of a rare earth metal and aluminum is formed on an alumina single crystal substrate, and further, YBa ₂ Cu ₃ O _{7 is} further formed thereon.
An yttrium-based superconductor composed of

[0020]

EXAMPLES Example 1-16 Various rare earth metals (Y, La, Pr, Nd, Sm, Eu,
Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu)
The experiments used were performed. Table 1 shows the experimental conditions and results.
You. The leftmost column in the table is the starting material, a rare earth metal-containing compound.
Where acac is acetylacetonate and naph is naphte
And ox represents 2-ethylhexanoate. Said a
In the case of cetyl acetonate, use trifluo
Methanol solution containing a small amount (0.1-10 mol%) of acetic acid
The liquid was used. By adding trifluoroacetic acid,
Improve the adhesion of the dried film to the substrate
Was completed. The naphthenate or 2-ethylhexa
In the case of phosphate, it is dissolved using toluene as the solvent.
I let you. The concentrations of these raw material solutions are shown in the second column of Table 1.
You. Alumina single crystal substrates are all R-plane, (012)
Using a substrate of 1.27 cm square with the surface as the surface,
About 0.04 ml of each raw material solution was dropped on this substrate.
5 seconds (seconds) at 2000 rpm by a spin coating method.
Pause) I went. Next, temporarily in air at 500 ° C. for 30 minutes.
Baking was performed to decompose and remove organic components. After this,
Was heat-treated. (1) Raise the temperature rapidly in oxygen and keep at 1000 ° C for 2 hours.
And then rapidly cooled down. (2) Raise the temperature rapidly in air and keep at 1000 ° C for 2 hours.
And then rapidly cooled down. (3) Raise the temperature rapidly in air and keep at 1200 ° C for 2 hours.
And then rapidly cooled down. (4) Gently raise the temperature in the air to 1600 ° C at 7:00
Hold for a while, then slowly cool down, then
Was identified by X-ray diffraction. The above results are shown in the right column of Table 1. From now on,
In the case of the thermal condition (3), an X-ray solution
As a result of the precipitation, the composition ratio of rare earth metal: aluminum: oxygen was
A substance with a perovskite structure of 1: 1: 3 is produced
It was confirmed that. Also epitaxial
was gotten. On the other hand, holding at 1000 ° C. for about 2 hours (before
According to (1)), the reaction did not proceed sufficiently,
became. In the case of the above (2), the purpose is set in the case of Nd.
NdAlO₃Was found to be partially contained. Ma
In addition, in holding at 1600 ° C. for 7 hours (the above (4)),
Too far, rare earth metal: aluminum: oxygen composition
Garnet structure phase with a ratio of 3: 5: 12, or 1:
It was confirmed that an 11:18 phase appeared. Nd,
In the case of Sm and Eu, the desired Nd
AlO₃, SmAlO₃, EuAlO ₃It is included
I understood that. As a result, the optimal heat treatment conditions are temperature and
1000-1600, preferably 1100-1
300 ° C., more preferably around 1200 ° C.
I understand. The holding time depends on the temperature.
But about 30 minutes to 10 hours, preferably 1 hour
It can be seen that it is in the range from time to 7 hours.

[0021]

[Table 1]

Example 19 An epitaxial thin film having a perovskite structure having a rare earth metal: aluminum: oxygen composition ratio of 1: 1: 3 obtained on a single crystal alumina substrate was used as an intermediate layer, and an yttrium-based superconducting thin film was formed thereon. Produced. As the superconducting film, a solution prepared by using acetylacetonate of yttrium, barium, or copper as a raw material and adjusting the metal ratio to 1: 2: 3 was used. The organic component was removed by holding the solution at 500 ° C. for 30 minutes in the air after the application, and then the following heating step was performed. That is, the oxygen partial pressure is 100 ppm
After holding at 750 ° C for 90 minutes in an atmosphere of
It was kept at 50 ° C. for 30 minutes and cooled as it was in oxygen. When the rare earth metals used for the intermediate layer were praseodymium, neodymium, and europium, it was confirmed by X-ray diffraction analysis that an epitaxial YBCO superconducting film was obtained. Also,
Superconducting transition is 90K by electric resistance measurement by 4-terminal method
It was also confirmed that it started from the vicinity. Further, for comparison, YB was directly used on a single crystal alumina substrate without using an intermediate layer.
Although a CO film was produced, no epitaxial film was obtained.

[0023]

According to the present invention, the composite oxide intermediate layer of rare earth and aluminum obtained by forming an epitaxial film of a composite oxide of rare earth and aluminum on the surface of single crystal alumina by a wet method, A superconductor made of an yttrium-based superconducting thin film can be formed on the surface, and as a result, an yttrium-based superconducting thin film can be provided on a single-crystal alumina substrate. This superconductor can handle large-diameter single-crystal alumina, and can provide a superconductor using single-crystal alumina having a large area as a substrate.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Susumu Mizuta 1-1-1 Higashi, Tsukuba, Ibaraki Pref., National Institute of Advanced Industrial Science and Technology (72) Inventor Shigeru Suzuki 2-17-1 Narashino-shi, Chiba Chiba Institute of Technology Faculty of Engineering (72) Inventor Yasuaki Yamaguchi 2-17-1 Narashino-shi, Chiba Pref. Faculty of Engineering (72) Inventor Norio Shimizu 2-17-1 Narashino-shi, Chiba F-term in Engineering Faculty (reference) 4G077 AA03 BC53 CA04 ED06 EF01 HA08 4M113 AD35 AD36 AD68 BA23 BA29 CA34 5G321 AA04 BA04 CA03 CA04 CA20 CA27 CA28 CA38 CA39 DB22 DB47 DB55

Claims (12)

[Claims] 1. A rare earth obtained by dissolving an alumina single crystal substrate and a rare earth metal-containing compound in a solvent to form a uniform solution, coating and drying the surface of the alumina single crystal substrate, forming a thin film, and heating and firing. A superconductor comprising a complex oxide epitaxial thin film having a metal: aluminum: oxygen composition of 1: 1: 3 and a YBa ₂ Cu ₃ O ₇ yttrium-based superconductor epitaxial thin film. 2. The rare earth metal is yttrium, lanthanum,
The superconductor according to claim 1, wherein the superconductor is selected from cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. 3. The superconductor according to claim 1, wherein the rare earth metal-containing compound is a compound selected from a rare earth metal organic acid salt and a rare earth metal acetylacetonate. 4. The superconductor according to claim 3, wherein when the rare earth metal-containing compound is rare earth metal acetylacetonate, the solvent is trifluoroacetic acid or methanol containing abietic acid. 5. The superconductor according to claim 1, wherein the heating and firing are performed at 1000 to 1600 ° C. 6. The superconductor according to claim 1, wherein an aluminum-containing compound is added to the rare-earth metal-containing compound. 7. A rare earth metal is provided on a surface of an alumina single crystal substrate.
Dissolve the compound in a solvent to form a homogeneous solution,
Apply and dry on a single crystal substrate surface to form a thin film,
Rare earth metal obtained by thermal firing: aluminum
Composite oxide epitaxy with a composition of 1: 1: 3
Xial thin film is formed, and Y, Ba, C
u selected from metal organic acid salts and metal acetylacetonates
Prepare an organic solvent solution of the metal-containing compound
A solution and applied to the epitaxial surface of the composite oxide
After drying, forming a thin film and heating and baking, YB
a ₂Cu₃O₇ Forming yttrium-based superconducting thin films
A method for producing a superconductor, comprising: 8. The rare earth metal is yttrium, lanthanum,
The method for producing a superconductor according to claim 7, wherein the superconductor is selected from cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. . 9. The method according to claim 7, wherein the rare earth metal-containing compound is a compound selected from a rare earth metal organic acid salt and a rare earth metal acetylacetonate. 10. The method for producing a superconductor according to claim 9, wherein when the rare earth metal-containing compound is a rare earth metal acetylacetonate, the solvent is methanol containing trifluoroacetic acid or abietic acid. . 11. A heating and baking process at 1000-1600 ° C. for forming a complex oxide epitaxial thin film having a rare earth metal: aluminum: oxygen composition of 1: 1: 3. A method for producing the superconductor according to the above. 12. The method for producing a superconductor according to claim 7, wherein an aluminum-containing compound is added to the rare-earth metal-containing compound.