JP2583571B2 - Method for producing oxide-based superconductor and substrate for producing superconductor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a superconductor used for a superconducting device and the like, and a substrate suitably used for producing such a superconductor.

"Prior art" Recently, various oxide-based superconductors having a critical temperature (Tc) at which a transition from a normal conducting state to a superconducting state has a value equal to or higher than the temperature of liquid nitrogen have been discovered. This type of oxide-based superconductor has a general formula AB-Cu-O (where A is La, Ce, Yb, Sc,
Is an element of Group IIIa of the Periodic Table such as Er and at least one element of Group Vb of the Periodic Table such as Bi and Sb, and B is an element of Group IIa of the Periodic Table such as Ba and Sr. It is shown.

Then, in order to produce such an oxide-based superconductor, for example, a compound or oxide powder containing a Group IIIa element and a compound or oxide powder containing a Group IIa element are mixed with a copper oxide powder. Heat-treated and pulverized powder is applied to the substrate, or superconducting powder is applied to the substrate to form a coating layer of superconductor precursor powder or superconducting powder, and then heat-treated to bake the coating layer. There is known a method in which a coating layer of a sintered superconducting material is formed to form a superconductor substrate.

"Problems to be Solved by the Invention" By the way, in the method of manufacturing a superconductor substrate,
In order to generate a superconductor sintered by applying a heat treatment to the coating layer of the superconducting precursor powder or superconducting powder, when the coating layer of the precursor powder or the superconducting powder composed of the above powder is thickened, the coating is performed. There is a problem that oxygen does not sufficiently penetrate into the lower layer of the cover layer, that is, the portion on the substrate side, and thus the superconducting material is not sufficiently generated in this portion. For this reason, there is a problem that it is difficult to produce a thick superconductor.

Further, although a substrate for producing a superconductor capable of solving the above-described problems has been desired, such a substrate has not yet been provided.

The present invention has been made in view of the above problems, and an object of the present invention is to supply a necessary amount of oxygen to a lower layer of a coating layer, which is liable to become oxygen-deficient at the time of firing, that is, a layer on the substrate side. An object of the present invention is to provide a method for producing a sintered oxide-based superconductor exhibiting characteristics, and a substrate for producing a superconductor suitably used in such a production method.

[Means for Solving the Problems] In the manufacturing method according to claim 1 of the present invention, an aluminum layer is formed on a substrate surface, and then the aluminum layer is subjected to anodizing treatment to form a porous oxide film layer. Formed, further formed a coating layer of superconductor precursor powder or superconductor powder on the porous layer, and then subjected to heat treatment to sinter the coating layer of the superconductor precursor powder or superconductor powder. The use of a superconductor is a means for solving the above problem.

Further, in the substrate according to the second aspect of the present invention, a porous aluminum layer is formed on a surface layer portion of the substrate, and oxygen required for firing is stored in pores of the porous aluminum layer. It was a solution to the problem.

Further, in the manufacturing method according to claim 3, an aluminum layer is formed on the surface of the substrate, and then the aluminum layer is subjected to an anodic oxidation treatment to form a porous oxide film layer. Is filled with an oxidizing agent, and then a coating layer of a superconductor precursor powder or a superconductor powder is formed on the porous layer, and then subjected to a heat treatment to coat the superconductor precursor powder or the superconductor powder. The substrate according to claim 4, wherein the layer is a sintered superconductor, and a porous aluminum oxide layer is formed on a surface layer portion of the substrate, and an oxidizing agent is filled in pores of the aluminum oxide layer. Are the means for solving the above problems.

Hereinafter, the present invention will be described in detail based on an example of the method for manufacturing an oxide-based superconductor according to the first aspect.

First, an aluminum layer 2 having a thickness of about 5 to 50 μm is formed on one surface of a substrate 1 as shown in FIG. Here, as a material of the substrate 1, a metal having a small coefficient of thermal expansion and a high heat resistance, such as zirconium, titanium, hafnium, nickel, tungsten, and tantalum, is suitably used.
For forming the aluminum layer 2 on the substrate 1, a dry method such as an evaporation method and an ion plating method is suitably adopted.

Next, the aluminum layer 2 is subjected to an anodizing treatment called an alumite treatment to form a porous layer 3 as shown in FIG. In this case, in order to perform the anodic oxidation treatment, the surface of the aluminum layer 2 is first degreased and washed as a pretreatment. Next, the aluminum layer 2 of the substrate 1 is used as an anode and immersed in an electrolytic solution such as sulfuric acid, oxalic acid, chromic acid or a mixed acid thereof, and a voltage is applied between the electrodes at a bath temperature of about 15 to 55 ° C. Then, a dense oxide film called a barrier layer is formed on the aluminum layer 2, and a porous layer 3 having fine pores starts to be formed on the oxide film, which grows by being treated for a predetermined time. 7-70 thickness
A porous layer 3 of about μm is formed. The porous layer 3 has a large number of holes 4 having a depth of about 6 to 69 μm and an inner diameter of about 0.02 μm.

Next, the substrate 1 on which the porous layer 3 is formed is heated in an oxygen atmosphere at a temperature of 1100 ° C. or higher, and the aluminum layer 2 is made of a thermally stable α-Al ₂ O ₃ layer.

Next, a coating layer 5 of a superconductor precursor powder or a superconductor powder having a thickness of about 10 μm to 1 mm is formed on the porous layer 3. In order to produce these precursor powders or superconducting powders, first, a predetermined ratio of the raw material powders containing the constituent elements of the oxide-based superconductor, that is, when producing a Y-Ba-Cu-O-based superconductor, Y: Ba: Cu = 1: 2: 3 (molar ratio) to obtain a mixed powder, and the mixed powder is calcined to obtain a precursor powder. In addition, this precursor powder is placed in an oxygen atmosphere at 850 to 110
By superfiring at about 0 ° C., a superconducting powder can be obtained.

In order to form the coating layer 5 of the superconductor precursor or the superconductor from the precursor powder or the superconductor powder thus prepared, a binder such as pine oil is added to the precursor powder or the superconductor powder, and the substrate is used as a resist. This is performed by coating and adhering on the first porous layer 3.

Thereafter, the substrate 1 is heat-treated in an oxidizing atmosphere at about 850 to 1100 ° C., and the coating layer 5 of the superconductor precursor powder or the superconductor powder is sintered into a superconductor layer 6.

According to such a method for manufacturing a superconductor, since the porous layer 3 is formed on the substrate 1 by anodizing the aluminum layer 2, the porous layer 3 acts as an air pocket and is trapped in the hole. Air serves as an oxygen supply source during firing of the superconductor precursor powder or the coating layer 5 of the superconductor powder, and the superconductor sintered layer 6 having excellent characteristics without deterioration in characteristics due to lack of oxygen during firing. Production becomes possible.

Further, the substrate for producing a superconductor according to claim 2 is a substrate in which the porous layer 3, that is, the porous aluminum oxide layer is formed on the surface layer portion of the substrate 1 as described above, and the aluminum oxide layer is formed of α- Since the layer is made of Al ₂ O _3, it is very stable thermally, and the coating layer 5 of the superconductor precursor powder or the superconductor powder is formed on the porous layer 3 using such a substrate. If a superconductor layer sintered by heat treatment is used, the air trapped in the pores serves as an oxygen supply source when firing the coating layer 5 of the superconductor precursor powder or the superconductor powder. This makes it possible to produce the superconductor sintered layer 6 having excellent characteristics without deterioration in characteristics due to lack of oxygen at the time.

Further, the method of manufacturing a superconductor according to claim 3 is the same as the manufacturing method of claim 1, except that the superconducting precursor powder or the superconductor powder is coated with the coating layer 5 as shown in FIG. The pores 4 of the porous layer 3 are filled with oxidizing agents 7 in the form of fine powder made of a metal oxide such as copper oxide, bismuth oxide, and silver oxide. Therefore, according to this manufacturing method, the oxidizing agents 7 in the pores 4 of the porous layer 3 serve as an oxygen supply source during firing of the superconductor precursor powder or the coating layer 5 of the superconductor powder. Even when the coating layer 5 of the precursor powder or the superconductor powder is formed thick, it is possible to form the sintered layer 6 of the superconductor without deterioration in characteristics due to lack of oxygen during firing.

In the substrate for producing a superconductor according to the fourth aspect, as described above, the porous layer 3, that is, the porous aluminum oxide layer is formed on the surface layer of the substrate 1, and the pores 4 of the porous layer 3 Is filled with oxidizing agent 7 in the form of powder,
Since the aluminum oxide layer is made of α-Al ₂ O _3, it is very stable thermally and is coated with a superconductor precursor powder or a superconductor powder on a substrate having such a porous layer 3. If the covering layer 5 is formed and the resulting superconducting layer is sintered by heat treatment, the oxidizing agents 7 in the pores supply oxygen during firing of the coating layer 5 of the superconductor precursor powder or the superconductor powder. As a source, it becomes possible to produce an excellent superconductor sintered body layer 6 without deterioration in characteristics due to lack of oxygen during firing.

"Example" Hereinafter, the present invention will be specifically described with reference to examples.

(Example 1) An oxide superconductor was manufactured based on the manufacturing method described in claim 1 of the present invention.

First, a nickel substrate having a thickness of 1.0 mm was prepared, and aluminum was deposited thereon to form an aluminum layer having a purity of 99.99% and a thickness of 5 μm.

Next, this substrate was immersed in a sulfuric acid solution having a bath temperature of 30 ° C. and a concentration of 30%, and subjected to anodization for 14 minutes at a current density of 1 A / dm ² to form a porous film having a thickness of about 7 μm Layer was formed.

Next, this substrate was heated at 1100 ° C. for 1 hour in an electric furnace to modify the aluminum layer to a thermally stable α-Al ₂ O ₃ crystal structure.

Then, a resist prepared by adding pine oil to Y-Ba-Cu-O-based superconductor precursor powder (calcined powder) is applied on the porous layer of the substrate by screen printing,
A coating layer of a superconductor precursor powder having a thickness of about 50 μm was formed.

Thereafter, the substrate on which the coating layer of the superconductor precursor powder was formed was heated in an oxygen atmosphere at 950 ° C. for 2 hours, gradually cooled, and a superconductor sintered on the substrate was produced.

When the superconducting properties of the superconductor obtained in this way were examined, the critical temperature was 90 K, and the critical current density at that time was 200 A /
It was cm ^2.

For comparison, a coating layer of a superconductor precursor powder was formed directly on a nickel substrate without forming a porous layer, and this was heat-treated to form a sintered superconductor. When the characteristics were examined, the critical temperature was 83 K, and the critical current density at that time was 50 A / cm ² .

(Example 2) An oxide-based superconductor was manufactured based on the manufacturing method described in claim 3 of the present invention.

First, in Example 1 described above, a porous layer was formed by anodic oxidation, and the substrate was further heat-treated to modify the aluminum layer into a thermally stable α-Al ₂ O ₃ crystal structure. Silver oxide fine powder as an oxidizing agent was uniformly filled in the pores of the porous layer of the substrate by a tumbling method (rubbing method).

Next, as in Example 1, Y-Ba was deposited on the porous layer of the substrate.
A resist prepared by adding pine oil to -Cu-O-based superconductor precursor powder (calcined powder) was applied by screen printing to form a coating layer of superconductor precursor powder with a thickness of about 50 μm. .

Thereafter, the substrate on which the coating layer of the superconductor precursor powder was formed was heated in an oxygen atmosphere at 950 ° C. for 2 hours, gradually cooled, and a superconductor sintered on the substrate was produced.

When the superconducting characteristics of the superconductor obtained in this way were examined, the critical temperature was 93 K, and the critical current density at that time was 220 A /
It was cm ^2.

[Effects of the Invention] As described above, in the manufacturing method according to claim 1 of the present invention, an aluminum layer is formed on a substrate surface, and then the porous layer is formed by performing anodizing treatment on the aluminum layer. Then, a coating layer of a superconductor precursor powder is formed on the porous layer, and then the coating layer of the superconductor precursor powder is subjected to a heat treatment to form a sintered superconductor. The porous layer acts as an air pocket, and the air trapped in the pores is the lower layer of the coating layer, that is, the oxygen source on the substrate side, which tends to cause deterioration in characteristics due to lack of oxygen when firing the coating layer of the superconductor precursor powder. As a result, a sintered layer of superconductor having excellent properties can be formed, and therefore, a sintered superconductor having a sufficient layer thickness and exhibiting superconducting properties excellent in critical temperature and critical current density is produced. Can do Wear.

Further, since the substrate according to claim 2 of the present invention has a porous aluminum oxide layer formed on the surface layer portion of the substrate, if a superconducting layer is formed on the aluminum oxide layer using this, a hole is formed. Since the air stored inside becomes a source of oxygen when firing the coating layer such as the superconductor precursor powder, a superconductor exhibiting excellent superconducting properties even when the coating layer is formed thickly is produced. be able to.

Further, in the manufacturing method according to the third aspect, an aluminum layer is formed on the substrate surface, and then the aluminum layer is subjected to an anodic oxidation treatment to form a porous layer. Filling agent, then forming a superconductor precursor layer on the porous layer, and then performing heat treatment to make the superconductor precursor layer a superconductor. Since it becomes an oxygen supply source when heating the coating layer of the precursor powder or the superconductor powder, even in the case where the coating layer is formed thicker, there is no deterioration in characteristics due to lack of oxygen during firing. A superconductor exhibiting superconductivity can be manufactured.

Further, the substrate according to claim 4 has a structure in which a porous aluminum oxide layer is formed in a surface layer portion of the substrate and an oxidizing agent is filled in pores of the aluminum oxide layer. If a superconductor powder or a coating layer of a superconductor powder is formed thereon, the oxidizing agent in the pores serves as an oxygen supply source during firing of the superconductor precursor layer, so that a superconductor exhibiting excellent superconductivity is produced. be able to.

[Brief description of the drawings]

FIGS. 1 and 2 are diagrams relating to a method for manufacturing a superconductor and a substrate for manufacturing a superconductor according to claims 1 and 2 of the present invention, wherein FIG. FIG. 2 is a schematic configuration diagram of a superconductor fabricated on a substrate, and FIG. 3 is related to a method of manufacturing a superconductor and a substrate for producing a superconductor according to the present invention. It is a figure and is a schematic block diagram of the superconductor produced on the board | substrate. 1 ... substrate, 2 ... aluminum layer, 3 ... porous layer,
4 ... holes, 5 ... coating layer of superconductor precursor powder or superconductor powder, 6 ... superconductor layer, 7 ... oxidizing agent.

Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H01B 12/02 H01B 12/02 13/00 565 13/00 565D H01L 39/02 H01L 39/02 W (72) Inventor Satoru Kono 1-5-1, Kiba, Koto-ku, Tokyo, Fujikura Electric Wire Co., Ltd. (72) Inventor Yoshimitsu Ikeno 1-5-1, Kiba, Koto-ku, Tokyo Fujikura Electric Wire Co., Ltd. (72) Inventor Sapporo Nobuyuki 1-5-1, Kiba, Koto-ku, Tokyo Fujikura Electric Wire Co., Ltd. (72) Inventor Mikio Nakagawa 1-5-1, Kiba, Koto-ku, Tokyo Fujikura Electric Wire Co., Ltd. (72) Inventor Yu Sugimoto, Koto, Tokyo 1-5-1, Kiba Ward, Fujikura Electric Wire Co., Ltd. (56) References JP-A-56-65996 (JP, A) JP-A-63-292518 (JP, A)

Claims (4)

(57) [Claims] An aluminum layer is formed on the surface of a substrate, and then the aluminum layer is anodized to form a porous layer. Then, a superconductor precursor powder or a superconductor powder is formed on the porous layer. A method for producing an oxide-based superconductor, comprising forming a coating layer and then performing a heat treatment to obtain a superconductor obtained by sintering the coating layer of the superconductor precursor powder or the superconductor powder. 2. A substrate for producing a superconductor, wherein a porous α-alumina layer is formed on a surface layer of the substrate. 3. An aluminum layer is formed on the surface of the substrate, and then the aluminum layer is anodized to form a porous layer. Further, an oxidizing agent is filled in the pores of the porous layer. Forming a coating layer of superconductor precursor powder or superconductor powder on the porous layer, and then performing a heat treatment to obtain a superconductor in which the coating layer of the superconductor precursor powder or superconductor powder is sintered. A method for producing an oxide-based superconductor, comprising: 4. A substrate for producing a superconductor, characterized in that a porous α-alumina layer is formed on the surface of the substrate and an oxidizing agent is filled in the holes of the α-alumina layer.