JP5066468B2 - Biaxially oriented thin film for oxide superconducting wire and method for producing the same - Google Patents

Description

  The present invention relates to a biaxially oriented thin film for an oxide superconducting wire and a method for producing the same.

  In order to make a rare earth oxide superconductor into a wire, a biaxially oriented intermediate layer, that is, a thin film, which becomes a template is required. The reason is as follows. Oxide superconductors are known to have a low critical current density, which is due to the presence of electrical anisotropy in the oxide superconductor crystals themselves. In particular, an oxide superconductor can easily flow electricity in the a-axis direction and the b-axis direction, and hardly flows in the c-axis direction. For this reason, in order to form an oxide superconductor on a substrate and use it as a superconductor, an oxide superconductor having a good crystal orientation is formed on the substrate, and It is necessary to orient the a-axis or b-axis of the oxide superconductor crystal in the direction in which electricity flows and to orient the c-axis of the oxide superconductor in the other direction. For this reason, forming an oxide superconducting layer with good crystal orientation on a substrate has been performed.

  Here, an oxide intermediate layer (that is, a thin film) having a fluorite structure oxide or a pyrochlore structure formed by an IBAD method (ion beam assisted vapor deposition method) exhibits a high degree of biaxial orientation, and a rare earth formed thereon. The system oxide superconducting layer exhibits good superconducting properties.

However, an intermediate layer (that is, a thin film) of these substances has a problem that it takes a manufacturing time and a manufacturing cost because the film forming speed is slow.
An object of the present invention is to provide a biaxially oriented thin film for an oxide superconducting wire capable of shortening the manufacturing time and reducing the manufacturing cost because the film forming speed is high.

  Another object of the present invention is to provide a method for producing a biaxially oriented thin film for an oxide superconducting wire that can reduce the production time because the film formation rate is high. .

In order to solve the above problems, the biaxially oriented thin film for an oxide superconducting wire of the present invention is laminated on a base material and disposed under a rare earth oxide superconducting layer oxide to form an intermediate layer. in biaxially oriented film for the oxide superconducting wire which, Ri Do oxides of celite structure wherein the thin film has a biaxial orientation, oxide of celite structure, at least from the YNbO _4, GdNbO 4 wherein the one selected der Rukoto ones were.

The intermediate layer may have a laminated structure in which an oxide layer having a fluorite structure is formed on the oxide having the celite structure.

The intermediate layer may have a laminated structure in which a pyrochlore oxide layer is formed on the celite oxide.
In addition, the method for producing a biaxially oriented thin film for an oxide superconducting wire according to the present invention includes an oxide superconducting layer that is laminated on a base material and disposed under an oxide of a rare earth oxide superconducting layer. In the method for manufacturing a biaxially oriented thin film for a wire, an oxide having a celite structure is laminated on the substrate by an ion beam assisted deposition method to form the thin film, and the oxide having the celite structure is formed of YNbO. ₄ or GdNbO ₄ is selected .

In the method for producing a biaxially oriented thin film for an oxide superconducting wire according to the present invention, an oxide layer having a fluorite structure may be formed on the oxide having the celite structure to form the intermediate layer. Good.
In the method for producing a biaxially oriented thin film for an oxide superconducting wire according to the present invention, a pyrochlore structure oxide layer may be formed on the celite structure oxide to form the intermediate layer. .

According to the biaxially oriented thin film for an oxide superconducting wire of the present invention, since the deposition rate of the thin film is high when the thin film is formed, the production time is shortened and the production cost can be reduced.
According to the method for producing a biaxially oriented thin film for an oxide superconducting wire of the present invention, since the deposition rate of the thin film is high when the thin film is formed, the production time is shortened and the production cost can be reduced.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 and 2.
As the material of the base material 10 of the oxide superconducting wire, Hastelloy (registered trademark) , silver, platinum, stainless steel and the like can be exemplified, and the shape can be exemplified by a long tape, a plate material and the like. .

The intermediate layer 20, that is, the thin film laminated on the base material 10 is preferably an oxide having a celite structure, and among them, at least one of YNbO ₄ and GdNbO ₄ is preferably selected. These oxides of the celite structure are less symmetrical than the fluorite structure, can maintain crystals even if they contain defects, and the film formation temperature can be changed to a pyrochlore structure or a fluorite structure. It is possible to increase the growth rate of the film because the temperature can be higher than that of the oxide. Moreover, the oxide of celite structure is almost the same as the oxide of fluorite structure or pyrochlore structure in the arrangement of cations in the crystal, so that it is as flat as these IBAD intermediate layers (ie, thin films). It is possible to increase the production speed at the time of production without impairing the advantage that cracks are hardly generated.

  Further, when the intermediate layer 20 has a laminated structure in which an oxide layer having a fluorite structure or a pyrochlore structure is formed on an oxide having a celite structure, the orientation at the initial stage of film formation is improved with the celite structure oxide. The flatness can be improved by an oxide layer having a fluorite structure or a pyrochlore structure.

  The ion beam assisted vapor deposition method (IBAD method) is a method in which particles generated from a target or an evaporation source are deposited on the base material 10 while irradiating the base material 10 with an ion gun from an oblique direction. The ion beam assisted vapor deposition method is performed in a vacuum container 40 as shown in FIG. 2, and the base material 10, target (evaporation source) 50, and ion gun 60 for assist ion beam are arranged in the vacuum container 40. Is done. The inside of the vacuum vessel 40 can be maintained in a vacuum atmosphere, and the atmosphere gas is in a low-pressure state such as a vacuum inside the vacuum vessel, and an inert gas atmosphere such as argon gas or an inert gas atmosphere containing oxygen Underneath, an intermediate layer, that is, an IBAD intermediate layer is formed on the base material 10 supported by the base material holder 15.

  The target (evaporation source) 50 is prepared for forming a target polycrystalline thin film, and has the same composition as that of the target polycrystalline or an approximate composition. 40. In the present embodiment, the aforementioned oxide having a celite structure is used as the target 50.

  DC sputtering, RF sputtering, ion beam sputtering, and electron beam are used to generate film forming material particles. Any method can obtain the effects of the present invention, but in this embodiment, ion beam sputtering is used in which the film formation rate of oxide particles having a celite structure is easily controlled. The ion beam irradiation device 70 for a sputter includes an evaporation source (not shown), and includes an electrode in the vicinity of the evaporation source. A sputtering acceleration voltage is applied to the electrode. The ion beam irradiation device for sputtering 70 ionizes a part of atoms or molecules generated from the evaporation source, and controls the ionized particles with an electric field generated by the electrodes, thereby forming an ion beam on the target 50. By irradiating, the oxide is knocked out from the target 50 and deposited on the base material 10.

The base material holder 15 is provided with a heater (not shown) for heating the base material 10.
The ion gun 60 for assist ion beam has the same configuration as the ion beam irradiation apparatus 70 for sputtering, and an incident angle θ with respect to the base material 10 (that is, a perpendicular line L with respect to the surface on which the oxide is deposited on the base material 10) The angle formed with the center line O of the ion gun 60 is tilted so as to be in the range of 45 to 60 degrees. The ion beam irradiated by the ion gun 60 may be an ion beam of a rare gas such as helium, neon, argon, xenon, or krypton, or a mixed beam of these and oxygen ions. The ion beam is controlled by applying an assist beam acceleration voltage to the electrode of the ion gun 60.

After the intermediate layer 20 (that is, a thin film) is formed on the substrate 10, a rare earth oxide superconducting layer 30 is deposited and formed by a conventional method as shown in FIG.
Rare earth-based oxide superconducting layer 30, for _example, can be cited _{YBa 2 Cu 3 O x, GdBa} 2 Cu 3 O x, the SmBa 2 _Cu 3 _{O x} or the like. Since the detailed description of the rare earth oxide superconducting layer 30 is not the main part of the present invention, the description is omitted.

  Below, Examples 1-4 and Comparative Examples 1-4 are demonstrated. In each of Examples 1 and 2 and Comparative Examples 1 to 4, an IBAD intermediate layer (that is, a thin film) was formed on a substrate by the ion beam assisted deposition method, and the film formation time of the IBAD intermediate layer and X The X-ray half width value φ formed by the line diffractometer was measured.

  3 and 4 show the relationship between the film formation time of the intermediate layer (IBAD intermediate layer) of the example and the comparative example and the quality (X-ray half width value φ) w. In FIG. 3, the vertical axis represents the X-ray half width value φ of the IBAD intermediate layer formed, and the horizontal axis represents the film formation time of the IBAD intermediate layer.

  In FIG. 3, in the case of Example 1 and Example 2, X-ray half-width values were measured at 60 minutes, 90 minutes, and 120 minutes during film formation. In Example 2, the X-ray half-width value was measured at 60 minutes, 90 minutes, 120 minutes, and 150 minutes during film formation. In Comparative Examples 3 and 4, X-ray half-width values were measured at 60 minutes, 120 minutes, and 150 minutes during film formation.

Further, in FIG. 4, the vertical axis represents the X-ray half width value [Delta] [phi, the horizontal axis is the film formation time of the IBAD intermediate layer. In the case of Example 3 and Example 4, the film formation time of the IBAD intermediate layer includes the total of the film formation time of the first stage and the second stage. In FIG. 4, in Example 3, X-ray half-width values were measured at 60 minutes, 150 minutes, and 180 minutes during the film formation in the second stage. In Example 4, the X-ray half-width value was measured at 60 minutes, 120 minutes, 180 minutes, and 220 minutes during the film formation in the second stage.

Test conditions of Examples 1 to 4 and Comparative Examples 1 to 4 are as follows.
Example 1
Target and intermediate layer material: YNbO ₄
Assist beam acceleration voltage: 400V
Sputtering acceleration voltage: 1100V
Heating temperature: 290 ° C
(Example 2)
Target and intermediate layer material: GdNbO ₄
Assist beam acceleration voltage: 400V
Sputtering acceleration voltage: 1100V
Heating temperature: 290 ° C
(Example 3)
In Example 3, a biaxially oriented thin film is formed in the same manner as in Example 1, and an oxide layer having a fluorite structure is further formed thereon to form a laminated structure.

As a first step, YNbO ₄ is formed as in the first embodiment. The conditions for the first stage are the same as in Example 1.
Target and intermediate layer material: YNbO ₄
Assist beam acceleration voltage: 400V
Sputtering acceleration voltage: 1100V
Heating temperature: 290 ° C
In the second stage, after the film formation time (30 minutes) in the first stage, the film was formed under the following film formation conditions.

Target and intermediate layer material: YSZ (yttrium stabilized zirconia)
Assist beam acceleration voltage: 200V
Sputtering acceleration voltage: 1000V
Heating temperature: 180 ° C
Example 4
In Example 4, a biaxially oriented thin film is formed in the same manner as in Example 2, and an oxide layer having a pyrochlore structure is further formed thereon to form a laminated structure.

As a first stage, GdNbO ₄ is formed in the same manner as in Example 2. The conditions for the first stage are the same as in Example 2.
Target and intermediate layer material: GdNbO ₄
Assist beam acceleration voltage: 400V
Sputtering acceleration voltage: 1100V
Heating temperature: 290 ° C
In the second stage, after the film formation time (30 minutes) in the first stage, the film was formed under the following film formation conditions.

Target and intermediate layer material: GZO (Gd ₂ Zr ₂ O ₇ )
Assist beam acceleration voltage: 200V
Sputtering acceleration voltage: 1100V
Heating temperature: 180 ° C
(Comparative Example 1)
Target and intermediate layer material: YSZ (yttrium stabilized zirconia)
Assist beam acceleration voltage: 200V
Sputtering acceleration voltage: 1000V
Heating temperature: 180 ° C
(Comparative Example 2)
Target and intermediate layer material: HoNbO ₄
Assist beam acceleration voltage: 450V
Sputtering acceleration voltage: 1000V
Heating temperature: 280 ° C
(Comparative Example 3)
Target and intermediate layer material: YbNbO ₄
Assist beam acceleration voltage: 450V
Sputtering acceleration voltage: 1000V
Heating temperature: 280 ° C
(Comparative Example 4)
Target and intermediate layer material: SrWO ₄
Assist beam acceleration voltage: 400V
Sputtering acceleration voltage: 1100V
Heating temperature: 290 ° C
In Examples 1 and 2, biaxially oriented intermediate layers were obtained. As shown in FIG. 3, in Example 1, the film formation time until the X-ray half width value Δφ reaches about 15 ° is about 120 minutes, and in Example 2, it is about 150 minutes. Note that the X-ray half width value Δφ of about 15 ° or less is a standard for obtaining a predetermined quality.

In contrast, in Comparative Examples 1 to 3, a biaxially oriented intermediate layer was obtained, but in Comparative Example 4, a biaxially oriented intermediate layer was not obtained. For this reason, FIG. 3 does not describe Comparative Example 4.
In Comparative Example 1, the time required for the X-ray half-width value Δφ to be about 15 ° takes an extremely long time of about 300 minutes.

Since Comparative Examples 2 and 3 could be expected to take longer than Comparative Example 1 as shown in FIG. 3, the formation of the film was stopped after 150 minutes.
From the above results, in Example 1 and Example 2, the time required for forming the intermediate layer to have an X-ray half-width value Δφ (= 15 °) indicating a predetermined quality as compared with the comparative example is sufficiently longer than in the comparative example. It turns out that a short time is good.

It was confirmed that the film thickness of about 0.6 μm was obtained in the film formation time of about 90 minutes for YNbO ₄ of Example 1 to achieve Δφ = 15 °.
In Example 3, in order to achieve about Δφ = 15 °, the film forming time may be about 180 minutes, and in Example 4, it may be about 120 minutes, both of which are extremely short compared to Comparative Example 1. The film could be formed in time.

The schematic sectional drawing of an oxide superconducting wire. Schematic of an apparatus for performing the IBAD method. The graph which shows the relationship between the film-forming time of the intermediate | middle layer of Examples 1, 2 and Comparative Examples 1-4, and quality (X-ray half-width value (phi)). The graph which shows the relationship between the film-forming time of the intermediate | middle layer of Example 3, 4 and Comparative Example 1, 2, and quality (X-ray half-width value (phi)).

Explanation of symbols

  10 ... substrate, 20 ... intermediate layer (thin film), 30 ... rare earth oxide superconducting layer.

Claims (6)

While being stacked on the substrate, the biaxially oriented film of superconducting wire disposed below the rare earth oxide superconducting layer to form an intermediate layer, oxidation of celite structure wherein the thin film has a biaxial orientation A biaxially oriented thin film for an oxide superconducting wire, characterized in that the oxide having a celite structure is selected from at least one of YNbO ₄ and GdNbO ₄ . 2. The biaxially oriented thin film for an oxide superconducting wire according to claim 1, wherein the intermediate layer has a laminated structure in which an oxide layer having a fluorite structure is formed on the oxide having the celite structure. . 2. The biaxially oriented thin film for an oxide superconducting wire according to claim 1 , wherein the intermediate layer has a laminated structure in which an oxide layer having a pyrochlore structure is formed on the oxide having a celite structure. While being laminated on a substrate, an intermediate layer disposed beneath the rare earth oxide superconducting layer, in the manufacturing method of the biaxially oriented film for the oxide superconducting wire,
An oxide having a celite structure is laminated on the substrate by an ion beam assisted deposition method to form the thin film,
A method for producing a biaxially oriented thin film for an oxide superconducting wire, wherein the oxide having a celite structure is at least one selected from YNbO ₄ and GdNbO ₄ .   The method for producing a biaxially oriented thin film for an oxide superconducting wire according to claim 4, wherein an oxide layer having a fluorite structure is formed on the oxide having the celite structure to form the intermediate layer. .   The method for producing a biaxially oriented thin film for an oxide superconducting wire according to claim 4, wherein an oxide layer having a pyrochlore structure is formed on the oxide having a celite structure to form the intermediate layer.

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