JP2012018799A - Method for manufacturing oxide superconductive thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an oxide superconductive thin film, in which, when a coating film of a MOD solution is subjected to calcination heat treatment to form a thick calcined film, reduced calcination period to improve its productivity, reduced thermal consumption, and reduced thermal history for a substrate allow the oxide superconductive thin film having a sufficiently high Ic to be formed in subsequent burning treatment.SOLUTION: A method for manufacturing an oxide superconductive thin film comprises: forming a coating film by applying a raw material solution containing metallic organic compounds of Re, Ba and Cu to a substrate (coating film formation step); pyrolyzing only the organic compound of Cu contained in the coating film to remove its organic component (first calcination treatment step); pyrolyzing the organic compounds of Re and Ba contained in the coating film to remove those organic components to form a calcined film (second calcination treatment step); and crystallizing the calcined film to form the oxide superconductive thin film (burning treatment step), in which the coating formation step and the first calcination treatment step are alternately repeated and thereafter the second calcination treatment is performed.

Description

  The present invention relates to a method for manufacturing an oxide superconducting thin film, and more particularly to a method for manufacturing an oxide superconducting thin film having a high critical current value used for manufacturing a superconducting wire.

  In order to further spread the superconducting wire using the oxide superconducting thin film, research on the production of an oxide superconducting thin film having a higher critical current value Ic has been conducted.

  One method of manufacturing such an oxide superconducting thin film is a method called a coating organic decomposition method (abbreviation: MOD method) (Patent Document 1).

  In this method, a raw material solution (hereinafter, also referred to as “MOD solution”) produced by dissolving each metal organic compound of Re (rare earth element), Ba (barium), and Cu (copper) in a solvent is applied to a substrate. Thereafter, the metal organic compound was heat-treated (calcined) at, for example, around 500 ° C., and the organic components contained were thermally decomposed and removed to form a calcined film that is a precursor of the oxide superconducting thin film. A vapor phase method in which an oxide superconducting thin film is manufactured by crystallizing a calcined film by further heat treatment (main baking) at a higher temperature (for example, 750 to 800 ° C.), and mainly manufactured in a vacuum. Compared to (sputtering method, pulsed laser deposition method, etc.), manufacturing equipment is simple, and it is widely used because it has features such as easy handling of large areas and complex shapes. .

  In addition, as a method of manufacturing a thick oxide superconducting thin film having a high Ic by using the MOD method, the MOD solution is repeatedly applied and calcined, and the calcined films are laminated, that is, multilayered to obtain a thick film temporarily. A method of firing is generally employed after forming a fired film.

JP 2007-165153 A

  However, in the conventional manufacturing method, much time is required for the calcining heat treatment. FIG. 7 shows a temperature profile of a conventional calcining heat treatment process for forming a three-layer calcined film on a substrate. As shown in FIG. 7, in the conventional manufacturing method, each layer is heated up to 350 ° C. at a rate of 10 ° C./min, and then up to 505 ° C. at a rate of 0.5 ° C./min. After raising the temperature, the organic matter of each metal organic compound is thermally decomposed by holding at 505 ° C. for 120 minutes. For this reason, it took about 8 hours for the calcining heat treatment of one layer, and it took 24 hours to produce a calcined film of a three-layer laminated type.

  As described above, since only a calcination heat treatment requires an enormous amount of time, there is a problem in that productivity is poor and a large amount of heat is consumed.

  Further, since the substrate is repeatedly exposed to a high temperature for a long time during the calcination heat treatment, a thermal history is generated on the substrate. For this reason, the superconducting properties of the oxide superconducting thin film may be adversely affected.

  Therefore, an attempt was made to form a thick calcined film by forming a coating film having a thickness of two layers on the substrate and performing a calcining heat treatment, but the calcined film is cracked. A new problem has occurred. With a calcined film in which cracks have occurred, a high Ic oxide superconducting thin film cannot be obtained even if a main heat treatment is performed.

  In the present invention, when a thick calcined film is produced by calcining a coating film of a MOD solution, the time is shortened to improve the productivity, the heat consumption is reduced, and the thermal history for the substrate is further reduced. It is an object of the present invention to provide a method for producing an oxide superconducting thin film, which can produce an oxide superconducting thin film having a sufficiently high Ic in the subsequent main annealing heat treatment.

  As a result of earnest research, the present inventor has found that the above problems can be solved by the inventions shown in the following claims, and has completed the present invention.

The invention described in claim 1
An oxide superconducting thin film used for the production of a superconducting wire is a method for producing an oxide superconducting thin film produced from a metal organic compound of Re (rare earth element), Ba and Cu by a coating pyrolysis method,
A coating film production step of producing a coating film by applying a raw material solution containing each metal organic compound on the substrate;
A first calcining heat treatment step of thermally decomposing only the organic compound of Cu contained in the coating film to remove organic components;
A second calcining heat treatment step of thermally decomposing the organic compound of Re and Ba contained in the coating film to remove organic components and producing a calcined film;
A calcination heat treatment step of crystallizing the calcined film to produce an oxide superconducting thin film,
The method for producing an oxide superconducting thin film is characterized in that after the coating film preparation step and the first calcination heat treatment step are alternately repeated twice or more, a second calcination heat treatment step is performed.

  In the invention of this claim, among the metal organic compounds of Re, Ba and Cu, the thermal decomposition temperature of the organic compound of Cu is as low as 200 ° C., and most of the organic components contained in the coating film are decomposed at a low temperature. It pays attention to.

  As an example, FIG. 8 shows a TG-DTA measurement result of a coating film in the production of a YBCO superconducting thin film. As shown in FIG. 8, the thermal decomposition temperature of the organic compound of Cu is 247 ° C., while the thermal decomposition temperature of the organic compound of Y and Ba is 443 ° C. And it turns out that about 40% of the organic component contained in a coating film is decomposed | disassembled by 247 degreeC.

  And when it heats up to 320 degreeC which the thermal decomposition of the metal organic compound of Cu is complete | finished, it turns out that 50% of organic components are decomposed | disassembled. When the rate of temperature increase is 10 ° C./minute as in the conventional case, about 30 minutes is sufficient as the time required for this treatment.

  In the invention of this claim, the calcination heat treatment step includes the first calcination heat treatment step of thermally decomposing the organic compound of Cu, and the first step of thermally decomposing organic compounds other than Cu, that is, Y and Ba. The process is divided into two calcining heat treatment processes, and the coating film preparation process and the first calcining heat treatment process are alternately repeated twice or more to increase the film thickness, and then the entire calcining heat treatment is performed in the second calcining heat treatment process. Thus, a thick calcined film is produced.

  Therefore, as described above, the time required for the first calcination heat treatment step is about 30 minutes, and the coating film preparation step and the first calcination heat treatment step can be repeatedly performed without requiring much time. . And finally, since the organic compounds of Y and Ba are thermally decomposed at the same temperature as the conventional calcining heat treatment temperature, the time required for the calcining heat treatment is greatly shortened even if the coating film is thickened. In addition, the heat consumption of the calcining heat treatment can be suppressed, and the thermal history of the substrate can also be reduced.

  Further, even when the calcination heat treatment is performed on the calcined film thus obtained, inhibition of crystal growth is suppressed, and the crystal grows sufficiently c-axis, so that it is sufficiently high. An oxide superconducting thin film having Ic can be produced.

  Further, as described above, since the thermal history of the substrate is also reduced, it is possible to manufacture an oxide superconducting thin film having high quality in the main annealing process.

The invention described in claim 2
2. The method for producing an oxide superconducting thin film according to claim 1, wherein a treatment temperature in the first calcining heat treatment step is 150 to 350 ° C. 3.

  In this claim, since the processing temperature in the first calcining heat treatment step is set to 150 to 350 ° C., it is preferable in that the calcining time is short and the thermal history received by the substrate can be reduced.

The invention according to claim 3
3. The method for producing an oxide superconducting thin film according to claim 1, wherein a treatment temperature in the second calcining heat treatment step is 350 to 600 ° C. 4.

  In the present claim, since the treatment temperature in the second calcining heat treatment step is set to 350 to 600 ° C., it is preferable from the viewpoint that a plurality of layers of Y and Ba organic compounds can be decomposed together.

  According to the present invention, when a thick calcined film is produced by calcining a coating film of a MOD solution, the time can be shortened to improve productivity, and the heat consumption can be reduced. By suppressing the thermal history with respect to the substrate, an oxide superconducting thin film having a sufficiently high Ic can be produced in the subsequent main annealing heat treatment.

It is a figure which shows the calcination temperature profile of the calcination heat treatment process of Example 1 of this invention. (A) and (b) are LSM photographs of the calcined film and the oxide superconducting thin film (fired film) of Example 1 of the present invention, respectively. It is a SEM photograph of the oxide superconducting thin film of Example 1 of this invention. It is a figure which shows the calcination temperature profile of the calcination heat treatment process of the form of Example 2 of this invention. (A) and (b) are LSM photographs of the calcined film at the two-layer lamination stage and the calcined film after the three-layer lamination of the three-layer lamination type calcined film of Example 2 of the present invention, respectively. It is a figure explaining the required time of the calcination heat processing of Example 2 of this invention. It is a figure which shows the three-layer lamination | stacking calcination temperature profile of the conventional calcination heat treatment process. It is a figure which shows the relationship between TG / weight reduction rate and DTA with respect to the temperature measured by apply | coating the MOD solution of Y, Ba, and Cu to a board | substrate, and heating up.

  Hereinafter, the present invention will be specifically described based on examples.

This example relates to a YBCO (Y123) oxide superconducting thin film.
[1] Example 1

1. Preparation of raw material solution Each acetylacetone metal complex of Y, Ba, and Cu is adjusted so that the molar ratio of Y: Ba: Cu is 1: 2: 3 and dissolved in alcohol (methanol) to obtain an acetylacetone metal complex solution. Was prepared.

2. Preparation of oxide superconducting thin film (1) Coating film preparation process The prepared raw material solution was applied on a CeO ₂ / YSZ single crystal substrate and then dried to prepare a coating film having a thickness of 0.90 μm.
(2) Calcination Heat Treatment Step FIG. 1 is a diagram showing a calcination temperature profile in the calcination heat treatment step of Example 1. The calcination heat treatment step includes a first calcination heat treatment step and a second calcination heat treatment step.

(A) First calcination heat treatment step The prepared coating film was heated to 350 ° C. at a temperature increase rate of 10 ° C./min as shown in FIG. The calcined film having a thickness of 0.30 μm was prepared.

  The coating film production step and the first calcining heat treatment step were alternately repeated twice to produce a calcined film having a thickness of 0.60 μm.

(B) Second calcination heat treatment step The prepared calcination film is further heated from 350 ° C. to 505 ° C. at a temperature increase rate of 0.5 ° C./min, and then held at the same temperature for 120 minutes. Thus, a calcined film having a thickness of 0.40 μm of a two-layer laminate type was produced.

(3) Main calcination heat treatment step After the calcination heat treatment step, the calcined film was heated from 505 ° C. to 770 ° C. at a temperature increase rate of 30 ° C./min in an Ar / O ₂ (25PPM) atmosphere. The temperature was maintained for 90 minutes. Thereafter, the temperature was lowered to room temperature to produce an oxide superconducting thin film having a thickness of 0.30 μm.

3. Evaluation of calcined film and oxide superconducting thin film after calcining heat treatment step FIGS. 2A and 2B are LSM photographs of the calcined film and the oxide superconducting thin film (fired film) of Example 1, respectively. FIG. 3 is a SEM photograph of the oxide superconducting thin film of Example 1. FIG. 2 shows that no cracks are observed in the calcined film and the main-fired film, and that a good calcined film and the main-fired film are obtained. In addition, it can be seen from FIG. 3 that a uniform composition with c-axis orientation up to the surface is obtained.

4). Evaluation of the time required for the calcination heat treatment step As shown in FIG. 1, the time required for the calcination heat treatment in Example 1, that is, the total time required for the first calcination heat treatment step and the second calcination heat treatment step is 500 minutes. It is. On the other hand, when the same two-layered calcined film as in Example 1 is produced by a conventional method, it takes about 900 minutes. According to Example 1, it can be seen that the time required for the calcining heat treatment can be greatly shortened as compared with the prior art.

[2] Example 2
1. Preparation of raw material solution A raw material solution was prepared in the same manner as in Example 1.

2. Preparation of oxide superconducting thin film (1) Coating film preparation process The prepared raw material solution was applied on the same substrate as in Example 1 and then dried to prepare a coating film having a thickness of 0.90 μm.

(2) Calcination Heat Treatment Step FIG. 4 is a diagram showing a calcination temperature profile in the calcination heat treatment step of Example 2.

(A) First calcination heat treatment step The prepared coating film was heated to 350 ° C. at a temperature rising rate of 10 ° C./min as shown in FIG. The calcined film having a thickness of 0.30 μm was prepared.

  The coating film production process and the first calcining heat treatment process were alternately repeated three times to produce a calcined film having a thickness of 0.90 μm.

(B) Second calcination heat treatment step The prepared calcination film is further heated from 350 ° C. to 505 ° C. at a temperature increase rate of 0.5 ° C./min, and then held at the same temperature for 120 minutes. Thus, a calcined film having a thickness of 0.60 μm was manufactured.

(3) Main calcination heat treatment step After the calcination heat treatment step, the calcined film was heated from 505 ° C. to 770 ° C. at a temperature increase rate of 30 ° C./min in an Ar / O ₂ (25PPM) atmosphere. The temperature was maintained for 90 minutes. Thereafter, the temperature was lowered to room temperature to produce an oxide superconducting thin film having a thickness of 0.45 μm.

3. Evaluation of calcined film and oxide superconducting thin film after calcining heat treatment step FIG. 5A is a calcined film in a two-layer lamination stage of the three-layer laminated type calcined film of Example 2, and FIG. It is a LSM photograph of the calcined film after three-layer lamination. 5 (a) and 5 (b), it can be seen that cracks do not occur even in the two-layer lamination stage where cracks have occurred in the conventional method. Furthermore, it turns out that the crack has not generate | occur | produced also in the calcined film after three-layer lamination.

4). Evaluation of Time Required for Calcination Heat Treatment Step FIG. 6 is a diagram illustrating a calcination temperature profile of the conventional three-layer lamination type with respect to the calcination temperature profile of the three-layer lamination type of Example 2 shown in FIG. It is the figure which expressed the time display of the horizontal axis as the same length.

  As shown in FIG. 6, the time required for the calcination heat treatment step in Example 2 is 9 hours. On the other hand, in the case of producing the same three-layer laminated type calcined film as in Example 2 by the conventional method, it takes 24 hours as shown in FIG. Thus, according to Example 2, it can be seen that the time required for the calcination heat treatment step can be significantly shortened as compared with the conventional case.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to above-described embodiment. Various modifications can be made to the above-described embodiment within the same and equivalent scope as the present invention.

Claims (3)

An oxide superconducting thin film used for the production of a superconducting wire is a method for producing an oxide superconducting thin film produced from a metal organic compound of Re (rare earth element), Ba and Cu by a coating pyrolysis method,
A coating film production step of producing a coating film by applying a raw material solution containing each metal organic compound on the substrate;
A first calcining heat treatment step of thermally decomposing only the organic compound of Cu contained in the coating film to remove organic components;
A second calcining heat treatment step of thermally decomposing the metal compound of Re and Ba contained in the coating film to remove organic components and producing a calcined film;
A calcination heat treatment step of crystallizing the calcined film to produce an oxide superconducting thin film,
A method for producing an oxide superconducting thin film, comprising performing the second calcination heat treatment step after alternately performing the coating film preparation step and the first calcination heat treatment step twice or more.   2. The method for producing an oxide superconducting thin film according to claim 1, wherein a treatment temperature in the first calcination heat treatment step is 150 to 350 ° C. 3.   The method for producing an oxide superconducting thin film according to claim 1 or 2, wherein a treatment temperature in the second calcining heat treatment step is 350 to 600 ° C.