JPH01176203A - Method for manufacturing superconducting thin film - Google Patents

Abstract

PURPOSE:To reduce thickness of film in a short treating time by a few processes simply by applying a solution of an organometallic compound or sol to a heat- resistant substrate to form a coating film and baking. CONSTITUTION:A rare earth metal alkoxide [e.g. Y(COCH3)3] of a compound shown by formula II (M is rare earth metal; R is <=10C alkyl), an alkaline earth metal alkoxide and a Cu alkoxide constituting a thin film of superconducting oxide comprising an oxide shown by formula I (Re is one or more rare earth metal; M is one or more alkaline earth metal) are dissolved in methyl alcohol, etc., to give a solution of organometallic compound (A). Then the component A is hydrolyzed with HCl, etc., to give sol (B). Then component A or B is applied to a heat-resistant substrate to form a coating film (C). Then the film C is baked to give a superconducting thin film having thickness of <=2mum.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing a superconducting thin film, particularly an extremely thin superconducting thin film made of a superconducting metal oxide and having a thickness of 2 μm or less.

(Prior Art) Recently, it has been discovered that certain metal oxides exhibit superconductivity at high temperatures, and research and development is underway to put them into practical use. As a technique for forming this type of high-temperature superconducting thin film, a casting method, a chemical vapor deposition method, a physical vapor deposition method, or the like is generally employed.

(Problems that Meimei is trying to solve) However, with the casting method, when preparing the film-forming paste, the raw material powder must be calcined to form an oxide, and this must be finely pulverized using a planetary mill, etc. Moreover, even if an attempt was made to obtain an ultra-thin superconducting thin film, there was a problem in that only a film with a thickness of about 10 μm could be obtained. Furthermore, chemical vapor deposition and physical vapor deposition can produce thin films of 2 μm or less, but these methods have a problem in that the composition of the formed thin film tends to change.

Therefore, the object of the present invention is to provide a method for easily manufacturing a superconducting thin film having a desired composition and having a thickness of 1 to 2 μm.

(Means for Solving the Problems) As a means for solving the above-mentioned problems, the present invention provides an organic metal compound of at least one of the metals constituting the superconducting oxide film, which is dissolved in an organic solvent. Prepare an organometallic compound solution or partially hydrolyze the obtained organometallic compound solution to form a sol, apply the organometallic compound solution or sol on a heat-resistant substrate, and remove the formed coating film. The present invention provides a method for manufacturing a superconducting thin film, which is characterized by firing.

In this specification, superconducting oxide film refers to ReM
Refers to a superconducting thin film made of Cu, O-based oxides (where Re represents at least one rare earth metal and M represents at least one alkaline earth metal), and typical examples include YBa, Cu, and O. ,, can be mentioned.

As the organometallic compound of the metal constituting the superconducting oxide film, metal alkoxides, fatty acid salts, acetylacetone complex salts, etc. are suitable.

The rare earth metal alkoxide includes a compound represented by the general formula: % formula %) (wherein M is a rare earth metal and R is an alkyl group having 10 or less carbon atoms), and a compound represented by the general formula: % formula %) (wherein M is a rare earth metal and R is an alkyl group having 10 or less carbon atoms) In the formula, M is a rare earth element, R is an alkyl group having 10 or less carbon atoms, and R1 and R1 are the same or different and are alkylene groups having 10 or less carbon atoms.

For example, typical yttrium alkoxides include Y(OCHs)s, Y(QC!H5)3, Y(O
CsHy)x, Y(OCH3)[0(,H4N(C,H
.

0H)da is mentioned. However, yttrium alkoxide is not limited to these, and the same applies to alkoxides of other rare earth metals.

In addition, the alkaline earth metal alkoxide has a general formula: % formula % (wherein, M is Be, Ca, Mg, Ba, Sr, and R is an alkyl group having 10 or less carbon atoms). Compound, general formula: M(ORXORIOR) (wherein M is Bes Cas Mgs Bas 5rS
R is an alkyl group having 10 or less carbon atoms, R1 is an alkylene group, and φ. ), and the general formula: M(ORXOR+N(RzOH)z) (wherein, M is Be, Ca, Mg, Ba, Sr, and R is the number of carbon atoms l
The alkyl groups below O, R1 and R2 are the same or different and are alkylene groups having 10 or less carbon atoms. ) is included.

Typical examples include Ba(OCHs)z, Ba(OCHs)
C2H5)2, B a(OCz Hs )(OC2Hz
CHz OCHs ), Ba(OCH, CH20CH
,),,Ba(OCHxXOCH2CHx OCH3)
, S r(OCHs)z, 5r(QCHs) [OCzH
4N(C2H40H)2] and the like.

Copper alkoxides include compounds represented by the general formula: %Formula%) (where M is a rare earth metal and R is an alkyl group having 10 or less carbon atoms), and the general formula: %Formula%)] Among them, M is a rare earth element, R is an alkyl group having 10 or less carbon atoms, and R1% and R2 are the same or different and are alkylene groups having 10 or less carbon atoms. Typical examples include, for example, Cu(OCHs)
z, Cu(OCHx) [0CzH+N(CzHaOH)
z]2, etc.

The acetylacetone complex salt of the metal has the general formula:
Bisacetylacetonato complex salt represented by M(acac)2 (wherein M is a metal and acac indicates acetylacetonate), general formula:
M(acac).

(In the formula, M is a metal and acac is acetylacetonato). Typical examples include, for example, Cu (CHs
COCHOCHs)! ,Y(CH3COCHOC
Examples include H3)3.

In addition, fatty acid salts include Ba(CHxCOO)z, Ba(CHlCHzCOO)
Includes z etc.

Any organic solvent can be used as long as it is soluble in the organometallic compound, but from an economical point of view, lower alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol are preferred. be.

In a preferred embodiment, all of the metals constituting the superconducting oxide film are used in the form of organometallic compounds, and each metal is dissolved in an organic solvent, mixed, and then partially dissolved by adding water to the mixed solution. Hydrolysis takes place.

In another embodiment, one of the metals constituting the superconducting oxide film is used in the form of an inorganic acid salt, and the aqueous solution is prepared by dissolving the organometallic compound of the remaining metal in an organic solvent. Partial hydrolysis takes place by mixing with the solution. In this case, suitable inorganic acid salts include hydrochlorides and nitrates of the metals constituting the superconducting oxide film.

For example, an aqueous solution of a fatty acid salt of an alkaline earth metal and an alkoxide solution of a rare earth element are mixed to produce a composite alkoxide of an alkaline earth metal and a rare earth element, and a solution of a copper alkoxide or an acetylacetonate complex salt is added to this. A mixed solution for forming a superconducting oxide film is prepared and used to form a film that is a precursor of a superconducting oxide film.

In addition, as the acid added to the reaction system during hydrolysis and solization, in addition to inorganic acids such as nitric acid, hydrochloric acid, and sulfuric acid, acetic acid and other arbitrary organic acids can be used.

(Function) In the present invention, at least one of the constituent elements of the superconducting oxide film is used in the form of an organic metal compound soluble in an organic solvent, and a coating film is formed on the substrate with the solution or sol. Therefore, after drying, a coating film is formed with only the organometallic compound or with the organometallic compound and the inorganic acid salt.

Therefore, during firing, the atoms of the metals that make up the superconducting oxide film in the coating react directly, forming extremely fine particles.
This makes it possible to produce extremely thin superconducting oxide films that are dense and 1 to 2 μm thick.

(Example 1) Y (0(Hs) [OC2H4N ('CZ H
40H)2 ] 2, a methanol solution of Ba(○CH3)2 as barium alkoxide, and Cu(OCH3) [OC2H4N (Cz H40
H) 2] Prepare ethanol solutions of 2, respectively,
These metals were accurately separated and mixed so that the molar ratio of Y:Ba:Cu=l:2:3.

After refluxing this mixed solution for 4 hours, a theoretical amount of l of Y B ax Cu307 obtained from its composition was added to the mixed solution.
1/4 to 1/8 of the theoretical amount required to hydrolyze the alkoxide, together with an amount of acetic acid corresponding to 1/10 to 1/20.
Add distilled water to partially hydrolyze.

This partially hydrolyzed sol solution was heated to 2.54×2゜54c.
Coat it on an m-square alumina substrate using a spinner,
The coating was dried to form a film that is a precursor to a superconducting oxide film. This process of applying and drying the sol solution was repeated until the precursor film had a predetermined thickness, and this was baked at 800°C in a natural atmosphere for 2 hours to obtain YB a2.
A superconducting thin film made of Cu,07 was obtained.

(Example 2) Y(○CH3)[0C2H4N(C2H40H)2]2
and an ethanol solution of Cu(OCHx)[0C2HaN
An ethanol solution of (C2H40H)2]2 and an aqueous solution of barium chloride were prepared, and the metals were separated and mixed accurately so that the molar ratio of these metals was Y:Ba:Cu-1=2:3. . This mixed solution was refluxed for 4 hours and cooled to obtain a solution for forming a superconducting thin film.

Next, the mixed solution was applied onto the substrate using a spinner in the same manner as in Example 1 and dried to form a precursor film of a superconducting oxide film. This was heated at 800℃ in a natural atmosphere for 2
A superconducting thin film made of YBa2Cu3O7 was obtained by baking for a period of time.

(Example 3) Y (OCHs) [OCx H4N (Cz H40
H)z]* ethanol solution and B a(CH3CO
O) z aqueous solution and Cu(OCHs) [0CzHaN
Ethanol solutions of (CtH*0H)zlz were prepared, and the molar ratio of these metals was Y:Ba:Cu=1=
Precisely separate and mix in a ratio of 2:3. This mixed solution was heated and distilled to remove methyl acetate, and then cooled to obtain a solution for forming a superconducting thin film.

When a thin film was formed using this solution in the same manner as in Example 1, a superconducting thin film made of YBalCu30A and having a thickness of lpm was obtained.

(Effects of the Invention) As explained above, according to the present invention, one can
Ultra-thin superconducting thin films of ~2 μm can be produced. In addition, there is no need to generate an intermediate as a source such as a calcined powder or target as in the casting method or vapor deposition method, and since the metal alkoxide reacts directly on the substrate, a dense film with small particle size can be formed. Furthermore, the firing temperature can be lowered by about 100°C compared to the conventional casting method, and excellent effects such as significantly shortening the processing time and the number of steps can be obtained.

Patent applicant Murata Manufacturing Co., Ltd.

Claims (5)

[Claims] (1) Prepare an organometallic compound solution by dissolving an organometallic compound of at least one metal among the metals constituting the superconducting oxide film in an organic solvent, or partially dissolve the obtained organometallic compound solution. Hydrolyze to form a sol, apply the organometallic compound solution or sol on a heat-resistant substrate,
A method for producing a superconducting thin film, which comprises firing the formed coating film. (2) The method for producing a superconducting thin film according to claim 1, wherein the metals are rare earth metals, alkaline earth metals, and copper. (3) The method for producing a superconducting thin film according to claim 2, wherein all of the metals are organometallic compounds, and the organometallic compound solution is partially hydrolyzed by adding water. (4) At least one organometallic compound among the metals is dissolved in an organic solvent, and the resulting solution is mixed with an aqueous solution of an inorganic acid salt of the remaining metal for partial hydrolysis. A method for producing superconducting thin films. (5) The method for producing a superconducting thin film according to any one of claims 2 to 4, wherein the organometallic compound is a metal alkoxide.