JPH03210711A - Manufacture of oxide superconductive conductor - Google Patents

Abstract

PURPOSE:To obtain a high critical temperature and critical current density by precipitating buffer layer material on a substrate held at a low temperature to make the surface of a buffer layer in the form of smooth amolphous, and heating and holding the substrate at a high temperature at which oxide superconductive conductor is precipitated on the buffer layer with C-axis orientation. CONSTITUTION:A buffer layer 2 and an oxide superconductive conductor layer 3 are laminated on a substrate 1 in order, or the buffer layers and the superconductive conductor layers are laminated on both surfaces of the substrate respectively. For this, the buffer layer having a smooth amorphous surface is precipitated on the substrate held at 350 deg.C or less, and the substrate is then held at a high temperature of 600 deg.C or over for precipitating oxide superconductive conductor. Superconductive conductor which is rich for C-axis orientation and having a high critical temperature and critical current density can thus be obtained, thereby a conductor preferable for a power cable, coil, etc., can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing an oxide superconductor in a conductor such as a power cable or a coil.

[Prior art] In recent years, Y-Ba-Cu-0 becomes superconducting at liquid nitrogen temperature.
Oxide superconductors such as the B1-3r-Ca-Cu-0 series and the B1-3r-Ca-Cu-0 series have been discovered, and applied research in various fields is being actively conducted.

By the way, these oxide superconductors are brittle, so in order to use them as conductors for cables, coils, etc., research is underway on methods of forming oxide superconductors into a film on a flexible metal substrate. has been done. As a method for forming an oxide superconductor on the above-mentioned metal substrate, PVD and C
Vapor phase deposition methods such as VD are mainly used, but when oxide superconductors are directly deposited on metal substrates, harmful substances in the metal substrate diffuse into the oxide superconductor layer, degrading superconducting properties. Therefore, a buffer layer is formed on a metal substrate and an oxide superconductor is formed on the buffer layer to prevent harmful substances in the metal substrate from diffusing into the oxide superconductor layer. In addition, in forming the buffer layer on the substrate in the above, the buffer layer material is deposited in a vapor phase on the substrate heated to a high temperature, or
Alternatively, the buffer layer material is vapor-deposited on the substrate at room temperature and then heat-treated at high temperature to form the buffer layer (00, ffi).
The crystals are oriented so that the plane is parallel to the substrate, and the subsequent oxide superconductor layer is placed on the buffer layer with a current flow direction C.
It was made to precipitate with axial orientation.

(Problem to be solved by the invention) However, when the buffer layer is formed on a substrate heated to a high temperature, or when it is formed at room temperature and then heat-treated at a high temperature, the surface of the formed buffer layer becomes When an oxide superconductor is deposited on such a buffer layer, the C-axis orientation of the formed oxide superconductor layer decreases, resulting in a rough surface with unevenness and high T and J. The problem was that it was not possible to obtain

[Means to solve the problem]

In view of this situation, the present invention has conducted extensive research and has found that when a seven-layer pamphlet material is deposited on a substrate kept at room temperature or a relatively low temperature, the formed buffer layer becomes amorphous with a smooth surface. discovered that when a substrate is heated to a predetermined temperature and an oxide superconductor is deposited on the amorphous buffer layer with a smooth surface, the oxide superconductor layer formed is highly C-axis oriented. After further research, the present invention was completed.

That is, the present invention provides a method for producing an oxide superconductor in which a buffer layer and an oxide superconductor layer are sequentially deposited on a substrate by a vapor phase deposition method. After depositing the buffer layer material in an amorphous form to form a buffer layer, the substrate was heated to 600 ml.
This is a method for producing an oxide superconductor, which comprises depositing an oxide superconductor on the amorphous buffer layer with a smooth surface while maintaining the temperature at a high temperature of .degree. C. or higher.

The structure of a conductor manufactured by the method of the present invention will be specifically explained below with reference to the drawings. FIG. 1 is a cross-sectional view showing an example of the structure of a conductor manufactured by the method of the present invention. In the figure, 1 is a base, on which a buffer layer 2 and an oxide superconductor layer 3 are sequentially formed.

FIG. 2 is a cross-sectional view showing another configuration example, in which a buffer layer 2 and an oxide superconductor layer 3 are sequentially formed on the upper and lower surfaces of the base 1, respectively, to increase the current carrying capacity.

In the method of the present invention, the reason why the buffer layer material is deposited on the substrate kept at a relatively low temperature of 350°C or less is to deposit the buffer layer material on the substrate in an amorphous state with a smooth surface. When the temperature exceeds .degree. C., the buffer layer material crystallizes and precipitates, resulting in unevenness on the surface.

The reason why the oxide superconductor is deposited on the buffer layer while maintaining the substrate at a high temperature of 600'C or higher is to deposit the oxide superconductor with C-axis orientation, and the substrate temperature is If the temperature is less than 600''C, the C-axis orientation is rapidly decreased.

In the method of the present invention, the substrate is made of Hastelloy alloy or SUS.
Metal materials such as In addition, the buffer layer formed on the substrate is made of a material that has excellent heat resistance and is non-reactive with the substrate and the oxide superconductor, such as YSZ (Y-stabilized Zr0t).
), MgO, 5rTiO8, and other ceramics are used. In addition, the oxide superconductor formed on the above-mentioned B and 7 F layers includes Y-Ba-Cu-0 series, B1-3r-Ca-Cu-
0 series, Tj! Any oxide superconductor such as the -Ba-Ca-Cu-0 system can be used.

In the method of the present invention, any vapor phase deposition method such as ion beam sputtering method, cluster ion beam method, MOCVD method, RF magnetron spa-vine method, etc. can be applied as a method for forming the buffer layer or oxide superconductor layer. .

[Effect]

In the present invention, the buffer layer material is deposited on the substrate kept at a relatively low temperature of 350°C or less, so the formed buffer layer has an amorphous shape with a smooth surface, and the oxide superconductor is C-axis oriented on the substrate. Since the oxide superconductor is deposited on the amorphous buffer layer with a smooth surface while being heated and held at a high temperature of 600°C or higher, the oxide superconductor layer has an extremely high carbon content on the buffer layer. Formed with axial orientation.

〔Example〕

The present invention will be explained in detail below using examples.

Example I Using an RF magnetron sputtering device, 0.4n of MgO was sputtered onto a Hastelloy alloy substrate kept at room temperature by applying a sputtering power of 100W in an atmosphere of Ar 2 mTorr.
It was sputtered to a thickness to form a buffer layer.

Next, using the RF magnetron sputtering device again, YBa,
An oxide superconductor with a composition of Cu and O in an Ar:oz ratio of 1:1
Y
A system oxide superconductor was manufactured.

In the above, the sputtering target has YB a *
A sintered body having a Cu5Ox composition was used, and the conductor after sputtering of an oxide superconductor was cooled to 200° C. and then taken out from the apparatus.

Example 2 A vacuum evaporation device was used instead of the RF magnetron spunter device, and Zr0t was deposited at 0.47% on the substrate as a buffer layer.
An oxide superconductor was manufactured by the same method as in Example 1 except that it was formed by vacuum deposition to a thickness of /Im.

In the above, the ZrO layer was formed by irradiating the ZrO□ tablet with an electron beam.

Example 3 An oxide superconductor was formed in the same manner as in Example 1, except that 5IJS 410 was used as the substrate and 5rTiO was sputtered to a thickness of 0.2μ as a buffer layer on this substrate. was manufactured.

Incidentally, a sintered body of 5rTiOs was used as a sputtering target for the above-mentioned 5rTiOs layer.

Example 4 An oxide superconductor was manufactured in the same manner as in Example 1 except that the substrate temperature was 300° C. when sputtering the buffer layer.

Example 5 An oxide superconductor was manufactured in the same manner as in Example 1 except that the substrate temperature during sputtering of the oxide superconductor was 800°C.

Comparative Example 1 In Example 1, the MgO layer provided by sputtering on the Hastelloy alloy substrate had 14! An oxide superconductor was produced in the same manner as in Example 1, except that heat treatment was performed at 900° C. for 10 minutes in an oxygen flow of /sin, and then the oxide superconductor was sputtered onto the MgO layer.

Comparative Example 2 An oxide superconductor was produced in the same manner as in Example 2, except that the Hastelloy alloy substrate was heated to 900° C. when sputtering ZrO.

Comparative Example 3 In Example 3, the 5rTiOs layer sputtered on the 5tlS410 substrate had 11! An oxide superconductor was produced in the same manner as in Example 1, except that heat treatment was performed at 800° C. for 10 minutes in an oxygen flow of 1/2 inch, and then the oxide superconductor was sputtered onto the 5rTiOs layer.

Comparative Example 4 An oxide superconductor was manufactured by the same method as in Example 1 except that the substrate temperature was 450° C. when sputtering the buffer layer material.

Comparative Example 5 An oxide superconductor was manufactured in the same manner as in Example 1 except that the substrate temperature during sputtering of the oxide superconductor was 550°C.

The critical temperature (T) and critical current density (Jc) of each oxide superconductor thus obtained were measured. Furthermore, the surface roughness of the buffer layer and the oxide superconductor layer was measured.

Note that J was measured at 77K using a DC 4-terminal method. The results are shown in Table 1 along with the main manufacturing conditions.

As is clear from Table 1, the method products of the present invention (Examples 1 to 3)
5) is an oxide superconductor formed because the surface of the buffer layer is smooth and because the oxide superconductor layer was formed on the buffer layer while heating and maintaining the substrate at a high temperature of 600°C or higher. All layers are rich in C-axis orientation, so Tc, J
The value of c was high.

On the other hand, in Comparative Examples 1 to 4 of the comparative method products, the buffer layer was formed by heating the substrate to a high temperature, or by forming it at room temperature and then heat-treating it at a high temperature, so that the buffer layer formed was on the surface. In Comparative Example 5, the oxide supert! Since the substrate temperature was too low when the body was sputtered, the C-axis orientation of the formed oxide superconductor layers decreased, resulting in low Tc and JC values.

〔effect〕

As described above, according to the method of the present invention, an oxide superconductor that is rich in C-axis orientation and excellent in T, .

[Brief explanation of drawings]

FIGS. 1 and 2 are cross-sectional views showing an example of the structure of an oxide superconductor manufactured by the method of the present invention. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Buffer layer, 3... Oxide superconductor layer.

Claims (1)

[Claims] In a method for manufacturing an oxide superconductor in which a buffer layer and an oxide superconductor layer are sequentially deposited on a substrate by a vapor phase deposition method, a buffer layer is deposited in an amorphous form with a smooth surface on a substrate maintained at 350°C or less. After depositing a layer material to form a buffer layer, an oxide superconductor is deposited on the amorphous buffer layer with a smooth surface while maintaining the substrate at a high temperature of 600° C. or higher. A method for manufacturing a superconductor.