JPH06114812A - Oxide superconductor and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a superconductor having an adequate film thickness by preventing the outflow of a liquid phase during calcination at the melting or partial melting temperature of an oxide superconductor layer. CONSTITUTION:In an oxide superconductor consisting of a substrate and an oxide superconductor layer formed on the substrate or consisting of an oxidation-resistant metal substrate and an oxide superconductor layer formed on the metal substrate through an intermediate layer, the average roughness (Ra) of the substrate next to the oxide superconductor layer or of the intermediate layer is in a range of 0.1-0.7mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxide superconductor having a laminated structure of a substrate-oxide superconducting layer or a substrate-intermediate layer-oxide superconducting layer, and a method for producing the same. By limiting the average surface roughness (Ra) of the substrate or the intermediate layer within a certain range, an oxide superconductor that prevents the outflow of a liquid phase that occurs during firing at the melting temperature or the partial melting temperature of the oxide superconducting layer And its manufacturing method.

[0002]

2. Description of the Related Art In recent years, oxide superconductors have attracted attention because of their high critical temperature, and in the field of electric power, nuclear magnetic resonance computer tomography diagnostic apparatus (MRI: Magnetic Resonance Image).
Applications such as ging) and magnetic shielding are expected. When these oxide superconductors are put into practical use, it is possible to manufacture the equipment and the substrate by using the oxide superconductor, but conventionally, a method of forming a layer of the oxide superconductor on an existing substrate is known. ing. When forming a layer of oxide superconductor on a substrate, usually select a substrate material that does not deteriorate the superconducting property because the reaction with the oxide superconductor is inactive during firing of the oxide superconductor, A layer of an oxide superconductor is formed by melting or firing at a partial melting temperature on this substrate or on the intermediate layer with an intermediate layer made of (3) being interposed.

For example, JP-A-1-270518 discloses a superconductor thick film formed on an alumina, magnesium oxide or partially stabilized zirconia substrate, and JP-A-1-252534. Describes a superconducting ceramic laminate in which an intermediate layer made of a noble metal such as silver or gold or magnesium oxide is provided between a base material and a thick film of a superconductor.

[0003]

However, in the above-mentioned prior art, the liquid phase may flow out during melting or firing at a partial melting temperature, and a sufficient film thickness may not be obtained, or the film thickness may be uneven. Therefore, there is a problem that desired superconducting characteristics cannot be obtained. Further, when the superconducting detection coil or the like is produced by the screen printing molding method, the wiring pattern printed on the substrate becomes wide due to the liquid phase outflow during firing, which makes it difficult to control the wiring width. The inventors of the present invention have conducted extensive studies to eliminate such drawbacks of the prior art, and find that the surface roughness of the substrate or the intermediate layer in contact with the oxide superconducting layer is a significant factor in the liquid phase outflow. all right.

That is, when an oxide superconductor is melted or baked at a partial melting temperature, a solid phase and a liquid phase having low viscosity coexist, but as in the conventional case, the surface roughness of the substrate or the intermediate layer is particularly high. If uncontrolled and rough, the liquid phase will flow out,
Separation occurs between the solid and liquid phases. An object of the present invention is to provide an oxide superconductor and a method for producing the same in which the above-mentioned drawbacks of the prior art are eliminated by limiting the average surface roughness of the substrate or the intermediate layer in contact with the oxide superconducting layer to a certain range. And

[0005]

In order to achieve the above object, according to the present invention, there is provided an oxide superconductor comprising a substrate and an oxide superconducting layer formed on the substrate. The surface roughness of the substrate in contact with the layer is the average surface roughness (R
a) Oxide superconductor characterized by having a thickness of 0.1 to 0.7 μm, and an oxidation resistant metal substrate and an oxide superconducting layer formed on the oxidation resistant metal substrate via an intermediate layer. The surface roughness of the intermediate layer in contact with the oxide superconducting layer has an average surface roughness (Ra) of 0.1 to 0.7.
There is provided an oxide superconductor characterized in that it is μm.

Further, according to the present invention, as a method for producing such an oxide superconductor, the surface roughness is the average surface roughness (R
a) on a substrate or intermediate layer of 0.1-0.7 μm,
Provided is a method for producing an oxide superconductor, which comprises forming a film-shaped molded product exhibiting superconducting properties by heating and then firing the film at a temperature at which the molded product melts or partially melts.

[0007]

The present invention is configured as described above, and by limiting the average surface roughness (Ra) of the substrate or the intermediate layer in contact with the oxide superconducting layer to 0.1 to 0.7 μm, the liquid phase during firing is Outflow is prevented. Further, within the above-mentioned limited range, the adhesion between the oxide superconducting layer and the substrate or the intermediate layer is also good, and peeling or the like occurs even if the cold heat is repeated between the extremely low temperature and the room temperature that express the superconducting properties. hard.

The present invention will be described in detail below. The substrate used in the present invention may be one that can maintain the mechanical strength of the oxide superconducting layer, and examples thereof include ceramics such as magnesium oxide, zirconia, and titania, and S.
US430, SUS310, Inconel, Incoloy,
Oxidation resistant metals such as Hastelloy and noble metals can be used.

However, when the oxide superconducting layer is formed directly on the substrate, when an oxidation resistant metal substrate is used, the reaction with the oxide superconducting layer is remarkable during firing, and the superconducting property of the obtained superconductor is deteriorated. . In addition, the precious metal, which has relatively little reaction with the oxide superconducting layer and can prevent deterioration of superconducting properties due to firing, increases the thickness of the precious metal when it is intended to maintain mechanical strength by itself as a substrate. It is necessary and costly.

Therefore, when the oxide superconducting layer is formed directly on the substrate, it is preferable to use ceramics such as magnesium oxide as the substrate, and when using an oxidation resistant metal substrate, the oxide superconducting layer and the substrate are used. It is preferable to provide an intermediate layer made of an inert material between and.
However, even when the intermediate layer is provided, iron, nickel, copper, and SUS304 used as a substrate in a usual magnetic shield are oxidized during firing during formation of the oxide superconducting layer and adhere to the intermediate layer. It is not preferable because it deteriorates the property. Further, the thickness of the substrate is not particularly limited as long as it can maintain the mechanical strength.

The intermediate layer may be made of any material having a low reactivity with the oxide superconducting layer during firing, such as noble metals such as silver, gold and platinum and ceramics such as magnesium oxide, zirconia and titania. Among the noble metals, inexpensive silver has a low Young's modulus and can relax the thermal stress generated in the laminated structure of the oxide superconducting layer / intermediate layer / metal substrate, and thus is preferably used. Further, magnesium oxide has extremely low reactivity with the oxide superconducting layer, and further,
Since the thermal expansion coefficient is close to that of the oxide superconducting layer and the thermal stress generated in the oxide superconducting laminated structure is small, it can be preferably used. As the method for forming the intermediate layer, any conventionally known method such as plating, thermal spraying, vapor deposition, and combinations thereof may be used. It is easy and preferable to produce a laminated substrate having an area. The thickness of the intermediate layer is
The thickness may be such that the reaction between the metal substrate and the oxide superconducting layer described above can be prevented.

In the present invention, prior to forming the oxide superconducting layer on the substrate or the intermediate layer as described above, the surface of these substrates or the intermediate layer has an average surface roughness (R).
a) Polishing is performed so as to have a thickness of 0.1 to 0.7 μm. R
The reason for limiting a to the range of 0.1 to 0.7 μm is that when Ra exceeds 0.7, liquid phase outflow occurs during firing, and when Ra is less than 0.1, liquid phase outflow can be prevented. Alternatively, the adhesion between the intermediate layer and the superconducting layer is lowered, and peeling or the like occurs due to a cooling / heating cycle in which the temperature of liquid nitrogen or the like for exhibiting superconducting characteristics is repeated between room temperature and room temperature. According to the experiments by the present inventors, Ra of the magnesium oxide sintered substrate without any surface treatment is 0.8 to 1.2 μm.
m is about Ra, and Ra when the surface treatment of the silver layer formed by thermal spraying on the substrate as the intermediate layer is not performed is 14.0 to 1
It was about 5.0 μm.

As a method of polishing the substrate or the intermediate layer,
Wet polishing using polishing paper, a method of processing with a wet lathe using a polishing grindstone, and the like can be used. If the polishing paper is used, polishing up to about # 400, and if the polishing grindstone is used up to about # 240, Ra is within the above range.

In the present invention, the superconducting composition used as the oxide superconducting layer is not particularly limited. For example, Bi ₂ Sr ₂ CaCu ₂ O _x or Bi ₂ Sr ₂ Ca is used.
Bi-Sr-Ca having a composition represented by ₂ Cu ₃ O _x
An oxide of a —Cu—O-based compound having a multi-layer perovskite structure is preferably used, and an M—Ba—Cu—O-based compound in which M is Sc, Y, La, Eu, Gd, Er,
YBa ₂ having a multilayer perovskite structure containing one or more rare earth elements selected from lanthanides such as Yb and Lu
A rare earth oxide having a composition such as Cu ₃ O _7-y is also used.

In the oxide superconductor of the present invention, an oxide superconducting layer made of the above-mentioned oxide superconducting composition is formed on a substrate having Ra of 0.1 to 0.7 μm or an intermediate layer obtained by polishing. Can be obtained. Specifically, first, Bi ₂ Sr ₂ CaCu ₂ O _x or YBa ₂ C
Raw material powders are prepared so as to have a composition of u ₃ O _7-y or the like and mixed. Next, it is preferable to calcinate the mixed raw material powder, and then to add silver and / or silver oxide to the calcined raw material powder, and it is more preferable to add magnesium oxide powder.

When a carbonate is used as a starting material, or when a slurry is prepared using an organic solvent, a binder, a dispersant, etc., carbon remains in the oxide superconducting compact.
If this carbon cannot be removed during firing and remains in the fired oxide superconducting layer, the superconducting properties will be significantly reduced. By adding the above-mentioned silver and / or silver oxide, the removal of carbon is assisted, and a high superconducting property is obtained when the addition amount of silver and / or silver oxide is in the range of 0.5 to 10.0% by weight. be able to. The residual carbon amount after firing is 0.5
It is preferable that the content is not more than wt%. Further, the silver remaining in the superconducting layer functions as a buffering agent for preventing the generation of cracks and can improve the mechanical strength of the superconducting layer, which is preferable. If the addition amount is less than 0.5% by weight, cracks occur, a large amount of carbon remains or bubbles remain, and the Jc value decreases. In addition, the melting may be non-uniform. If it exceeds 10.0% by weight, a large amount of silver is dispersed in the oxide superconducting layer after firing and the Jc value is lowered, which is not preferable.

When magnesium oxide powder is added, the ratio of the solid phase component increases when the superconducting oxide is partially melted, the apparent viscosity increases, and the decrease in the liquid phase viscosity decreases.
Therefore, it is possible to prevent glaze dripping due to a rapid decrease in viscosity around the melting point of the superconducting oxide, and to combine with the liquid phase outflow preventing effect by limiting the Ra range of the substrate or the intermediate layer, which is the main effect of the present invention. Therefore, it becomes easier to form a thick oxide superconducting layer. The amount of magnesium oxide powder added is preferably in the range of 0.5 to 5.0% by weight,
When added in this range, the oxide superconducting layer has a film thickness of 10 to 10.
If it is 1000 μm, it can be formed without suffering from disadvantages such as glaze sag. If the addition amount of the magnesium oxide powder is less than 0.5% by weight, a sufficient effect of decreasing the viscosity of the liquid phase is not obtained, and if it exceeds 5.0% by weight, a large amount of magnesium oxide is present in the oxide superconducting layer after firing. And the Jc value decreases, which is not preferable. The particle size of the magnesium oxide powder to be added is not particularly limited, but magnesium oxide powder penetrating the oxide superconducting layer itself acts as a defect, which is not preferable.

As described above, preferably, a solvent or the like is added to the oxide superconductor raw material powder to which the silver and / or silver oxide and magnesium oxide powders are added to obtain a slurry. And
Using the slurry containing this oxide superconductor raw material, Ra can be formed by any conventionally known method such as coating by spraying or the like or placing a molded body by the doctor blade method.
A film-shaped compact is formed on a substrate or an intermediate layer having a thickness of 0.1 to 0.7 μm. In addition, screen printing molding is preferably used for forming the wiring pattern and the like of the oxide superconducting detection coil and the like. Next, in an oxygen atmosphere, this molded body,
The oxide superconducting layer is formed by firing at a temperature at which it melts or partially melts. The firing temperature is appropriately adjusted depending on the type of superconducting oxide, and for example, when it is made of YBa ₂ CuO _x, it is 9
The temperature is 00 to 1200 ° C., and the temperature is 870 to 910 ° C. when it is made of Bi ₂ Sr ₂ CaCu ₂ O _x .

[0019]

EXAMPLES The present invention will now be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

(Example 1) Magnesium oxide (purity 9
One side of a 9.9%) sintered substrate (20 × 50 × 5 mm) was wet-polished to # 400 (abrasive paper). The surface roughness of the obtained polished surface is measured by a surface roughness measuring instrument (manufactured by Tokyo Seimitsu).
And an average surface roughness (Ra) of 0.15 μm was obtained. Next, the Bi ₂ Sr ₂ CaCu ₂ O _x raw material is ethanol,
Toluene, ethyl acetate or isopropyl alcohol was used as a solvent, a binder, a plasticizer and a dispersant were added to prepare a doctor blade molded oxide superconducting molded body. The obtained oxide superconducting molded body was placed on the polished surface of the magnesium oxide sintered body substrate, and it was placed in an oxygen gas atmosphere at 890.
Partially melted at ℃, gradually cooled to 830 ℃ at a cooling rate of 1 ℃ / min, and kept at 830 ℃ for 15 hours to crystallize. Furthermore, 7
It was cooled to 00 ° C. and then gradually cooled to room temperature in a nitrogen atmosphere to obtain an oxide superconductor test piece.

The resulting oxide superconductor test piece was visually observed to evaluate its appearance, and was judged as good or bad.
The judgment was made based on the presence / absence of liquid phase outflow, and those without liquid phase outflow were evaluated as good, and those with liquid phase outflow were evaluated as poor. In addition, the critical current density was measured in liquid nitrogen by the four probe method. Further, the thermal cycle evaluation was performed by the following method. First, the obtained oxide superconductor was immersed in liquid nitrogen, and after the oxide superconductor reached the liquid nitrogen temperature, it was held for 30 minutes to measure the critical current density (magnetic shielding ability). After that, the oxide superconductor is taken out of the liquid nitrogen, left at room temperature, and held for 30 minutes after the entire oxide superconductor reaches room temperature, which is defined as one cycle, and is immersed in liquid nitrogen again and held, The critical current density (magnetic shielding ability) measurement, room temperature removal, leaving, holding and cycling were repeated 5 times, the first time and 5 times.
The critical current densities (magnetic shielding ability) of the second thermal cycle are compared with the following numerical formulas 1, respectively, and 80% or more is ○, 50%
The above was evaluated as Δ, and less than 50% was evaluated as x. These results are shown in Table 1.
Shown in.

[0022]

[Equation 1]

Examples 2 to 11 Table 1 shows the measured values of the average surface roughness (Ra) of the polished surface of the magnesium oxide sintered body substrate.
As shown in Table 1, the Bi ₂ Sr ₂ CaCu ₂ O _x raw material is shown in Table 1.
Add the silver powder in the amount shown in, and adjust the partial melting temperature to 885.
An oxide superconductor test piece was obtained in the same manner as in Example 1 except that the temperature was set to 0 ° C., and each characteristic was measured and evaluated. The results are shown in Table 1.

(Examples 12 to 16) The measured values of the average surface roughness (Ra) of the polished surface of the magnesium oxide sintered body substrate are shown in Table 1, and the Bi ₂ Sr ₂ CaCu ₂ O _x raw material was used in Table 1. An oxide superconductor test piece was obtained in the same manner as in Example 1 except that the addition amounts of silver powder and magnesium oxide powder shown in 1 were added and the partial melting temperature was 885 ° C., and each characteristic was measured and evaluated. The results are shown in Table 1.

[0026]

[Table 1]

Example 17 Magnesium oxide (purity 9
9.9%) sintered cylinder (ID70 x OD80 x H40
The outer surface of 0 mm, with bottom) was ground to # 240 (grinding stone) with a wet lathe. The surface roughness of the obtained polished surface was measured with a surface roughness profiler (manufactured by Tokyo Seimitsu Co., Ltd.) to obtain an average surface roughness (Ra) of 0.25 μm. Next, Bi ₂ Sr ₂ Ca
A Cu ₂ O _x raw material was used as a solvent in ethanol, toluene, ethyl acetate, or isopropyl alcohol as a solvent, and was spray-coated to form an oxide superconducting magnetic shield cylinder. The obtained oxide superconducting magnetic shield cylinder compact was partially melted in an oxygen gas atmosphere at 890 ° C., gradually cooled to 830 ° C. at a temperature lowering rate of 1 ° C./min, and kept at 830 ° C. for 15 hours for crystallization. Further, it was cooled to 700 ° C. and then gradually cooled to room temperature in a nitrogen atmosphere to obtain an oxide superconducting magnetic shield cylinder, and each characteristic was measured and evaluated in the same manner as in Example 1. The results are shown in Table 2.

(Examples 18 and 19) The measured values of the average surface roughness (Ra) of the polished surface of the magnesium oxide sintered cylinder are shown in Table 2, and the raw material of Bi ₂ Sr ₂ CaCu ₂ O _x was silver powder. 4.0 wt% was added, and the partial melting temperature was 885 ° C.
An oxide superconducting magnetic shield cylinder was obtained in the same manner as in Example 17 except that the above was used, and each property was measured and evaluated. The results are shown in Table 2.

(Examples 20 and 21) The measured values of the average surface roughness (Ra) of the polished surface of the magnesium oxide sintered body cylinder are shown in Table 2, and the raw material of Bi ₂ Sr ₂ CaCu ₂ O _x was silver powder. 4.0% by weight, magnesium oxide powder 1.0
An oxide superconducting magnetic shield cylinder was obtained in the same manner as in Example 17 except that the weight percent was added and the partial melting temperature was 885 ° C., and each characteristic was measured and evaluated. The results are shown in Table 2.

Example 22 Magnesium oxide (purity 9
9.9%) powder by plasma spraying method to Inconel 6
Thermal spraying was performed on the outer surface of 25 cylinders (φ100 × H600 mm, with bottom) to obtain a laminated cylinder having a magnesium oxide layer thickness of 0.3 mm and an Inconel layer thickness of 1.98 mm. Next, the magnesium oxide layer was wet-turned with a # 240 (polishing wheel).
Polished up to. The surface roughness of the obtained polished surface was measured with a surface roughness measuring instrument (manufactured by Tokyo Seimitsu Co., Ltd.), and the average surface roughness (R
a) 0.64 μm was obtained. Next, Bi ₂ Sr ₂ CaCu ₂
An oxide superconducting magnetic shield molding was produced by spray coating using ethanol, toluene, ethyl acetate or isopropyl alcohol as a solvent for the O _x raw material.
The obtained oxide superconducting magnetic shield cylinder compact was partially melted in an oxygen gas atmosphere at 890 ° C., gradually cooled to 830 ° C. at a temperature lowering rate of 1 ° C./min, and kept at 830 ° C. for 15 hours for crystallization. Further, it was cooled to 700 ° C. and then gradually cooled to room temperature in a nitrogen atmosphere to obtain an oxide superconducting magnetic shield cylinder, and each characteristic was measured and evaluated in the same manner as in Example 1. The results are shown in Table 2.

(Example 23) The average surface roughness (Ra) of the polished surface of the magnesium oxide layer is shown in Table 2, and the Bi ₂ Sr ₂ CaCu ₂ O _x raw material contains 4.0 parts by weight of silver powder. %, And an oxide superconducting magnetic shield cylinder was obtained in the same manner as in Example 22 except that the partial melting temperature was set to 885 ° C., and each characteristic was measured and evaluated. The results are shown in Table 2.

(Example 24) The measured values of the average surface roughness (Ra) of the polished surface of the magnesium oxide layer are as shown in Table 2, and the Bi ₂ Sr ₂ CaCu ₂ O _x raw material contained 4.0 weight% of silver powder. %, Magnesium oxide powder was added at 1.0% by weight, and an oxide superconducting magnetic shield cylinder was obtained in the same manner as in Example 22 except that the partial melting temperature was 885 ° C., and each characteristic was measured and evaluated. The results are shown in Table 2.

(Example 25) Inconel 625 cylinder (φ1) was prepared by a powder gas spraying method using silver (purity 99.9%) powder.
Thermal spraying was applied to the outer surface (00 × H600 mm, bottomed) to obtain a laminated cylinder having a silver layer thickness of 0.3 mm and an Inconel thickness of 1.98 mm. Next, the silver layer was polished by a wet lathe to # 240 (polishing stone). The surface roughness of the obtained polished surface was measured with a surface roughness measuring instrument (manufactured by Tokyo Seimitsu Co., Ltd.) to obtain an average surface roughness (Ra) of 0.27 μm. Next, Bi ₂ Sr ₂ Ca
An oxide superconducting magnetic shield molded body was produced by spray coating molding using ethanol, toluene, ethyl acetate or isopropyl alcohol as a solvent for the Cu ₂ O _x raw material. The obtained oxide superconducting magnetic shield cylindrical molded body,
Partially melted at 885 ° C in an oxygen gas atmosphere, and the cooling rate was 1 ° C.
The mixture was gradually cooled to 830 ° C. at a heating rate of 1 minute / minute, and kept at 830 ° C. for 15 hours for crystallization. Further cool to 700 ° C, then
Slowly cool to room temperature in a nitrogen atmosphere to obtain an oxide superconducting magnetic shield cylinder, and measure each characteristic in the same manner as in Example 1.
An evaluation was made. The results are shown in Table 2.

(Example 26) The measured values of the average surface roughness (Ra) of the polished surface of the silver layer are as shown in Table 2, and Bi ₂ S
1. Magnesium oxide powder was added to r ₂ CaCu ₂ O _x raw material.
An oxide superconducting magnetic shield cylinder was obtained in the same manner as in Example 25 except that 0% by weight was added, and each characteristic was measured and evaluated. The results are shown in Table 2.

(Examples 27 to 29) The measured values of the average surface roughness (Ra) of the polished surface of the silver layer are as shown in Table 2, and the material of the cylinder to be the substrate is SUS430 (Example 27), Inconel 601 (Example 28), SUS31
An oxide superconducting magnetic shield cylinder was obtained in the same manner as in Example 25 except that it was set to 0S (Example 29), and each characteristic was measured and evaluated. The results are shown in Table 2.

(Example 30) Magnesium oxide (purity 9
9.9%) sintered cylinder (ID30 x OD36 x H10
The outer surface of 0 mm) is # 400 (grinding stone) with a wet lathe.
Polished up to. The surface roughness of the obtained polished surface was measured with a surface roughness measuring instrument (manufactured by Tokyo Seimitsu Co., Ltd.), and the average surface roughness (R
a) 0.12 μm was obtained. Next, Bi ₂ Sr ₂ CaCu _2
Ox raw material using ethanol, toluene, ethyl acetate or isopropyl alcohol as a solvent, binder, plasticizer, dispersant added, screen printing molding, oxide superconducting detection coil molding printed wiring pattern of the detection coil The body was made. The obtained oxide superconducting molded body was partially melted at 890 ° C. in an oxygen gas atmosphere, gradually cooled to 830 ° C. at a temperature lowering rate of 1 ° C./minute, and kept at 830 ° C. for 15 hours for crystallization. Further, it was cooled to 700 ° C. and then gradually cooled to room temperature in a nitrogen atmosphere to obtain an oxide superconducting detection coil, and each characteristic was measured and evaluated in the same manner as in Example 1. The results are shown in Table 2.

(Example 31) The measured values of the average surface roughness (Ra) of the polished surface of the magnesium oxide sintered cylinder are as shown in Table 1, and the Bi ₂ Sr ₂ CaCu ₂ O _x raw material was mixed with silver powder. An oxide superconducting detection coil was obtained in the same manner as in Example 30 except that 4.0% by weight was added and the partial melting temperature was 885 ° C., and each characteristic was measured and evaluated. The results are shown in Table 2.

(Example 32) The measured values of the average surface roughness (Ra) of the polished surface of the magnesium oxide sintered cylinder are as shown in Table 1, and the Bi ₂ Sr ₂ CaCu ₂ O _x raw material was mixed with silver powder. 4.0% by weight, magnesium oxide powder 1.0% by weight
Example 3 except that the partial melting temperature was 885 ° C.
An oxide superconducting detection coil was obtained in the same manner as in 0, and each characteristic was measured and evaluated. The results are shown in Table 2.

[0039]

[Table 2]

Comparative Example 1 Magnesium oxide (purity 9
An oxide superconductor test piece was obtained in the same manner as in Example 1 except that polishing was not performed on the sintered body substrate (9.9%) (20 × 50 × 5 mm), and each characteristic was measured and evaluated. The results are shown in Table 3. In addition, when the surface roughness of the fired surface of the magnesium oxide sintered body substrate was measured with a surface roughness measuring instrument (manufactured by Tokyo Seimitsu Co., Ltd.), the average surface roughness (Ra) was obtained.
0.88 μm was obtained.

Comparative Example 2 Magnesium oxide (purity 9
An oxide superconductor test piece was obtained in the same manner as in Example 1 except that one side of a sintered body substrate (9.9%) (20 × 50 × 5 mm) was wet-polished to 2 μm diamond abrasive grains. Each characteristic was measured and evaluated. The results are shown in Table 3. In addition, when the surface roughness of the obtained polished surface was measured by a surface roughness measuring instrument (manufactured by Tokyo Seimitsu Co., Ltd.), an average surface roughness (Ra) of 0.06 μm was obtained.

Comparative Example 3 Magnesium oxide (purity 9
An oxide superconductor test piece was obtained in the same manner as in Examples 2 to 7, except that the sintered substrate (9.9%) (20 × 50 × 5 mm) was not polished, and each characteristic was measured and evaluated. . The results are shown in Table 3. The surface roughness of the fired surface of the magnesium oxide sintered body substrate was measured by a surface roughness measuring instrument (manufactured by Tokyo Seimitsu Co., Ltd.), and the average surface roughness (R
a) 0.91 μm was obtained.

Comparative Example 4 Magnesium oxide (purity 9
The oxide superconductor test pieces were prepared in the same manner as in Examples 2 to 7 except that one surface of a sintered body substrate (9.9%) (20 × 50 × 5 mm) was wet-polished to 2 μm diamond abrasive grains. Then, each characteristic was measured and evaluated. The results are shown in Table 3.
Shown in. When the surface roughness of the obtained polished surface was measured by a surface roughness measuring instrument (manufactured by Tokyo Seimitsu Co., Ltd.), an average surface roughness (Ra) of 0.07 μm was obtained.

Comparative Example 5 Magnesium oxide (purity 9
An oxide superconductor test piece was obtained in the same manner as in Example 14 except that the 9.9%) sintered substrate (20 × 50 × 5 mm) was not polished, and each characteristic was measured and evaluated. The results are shown in Table 3. In addition, when the surface roughness of the fired surface of the magnesium oxide sintered body substrate was measured with a surface roughness measuring instrument (manufactured by Tokyo Seimitsu Co., Ltd.), the average surface roughness (Ra) was obtained.
0.86 μm was obtained.

Comparative Example 6 Magnesium oxide (purity 9
An oxide superconductor test piece was obtained in the same manner as in Example 14 except that one side of a sintered body substrate (9.9%) (20 × 50 × 5 mm) was optically polished to 2 μm diamond abrasive grains. Each characteristic was measured and evaluated. The results are shown in Table 3. In addition, when the surface roughness of the obtained polished surface was measured by a surface roughness measuring instrument (manufactured by Tokyo Seimitsu Co., Ltd.), an average surface roughness (Ra) of 0.06 μm was obtained.

Comparative Example 7 Magnesium oxide (purity 9
9.9%) sintered cylinder (ID70 x OD80 x H40
An oxide superconducting magnetic shield was obtained in the same manner as in Examples 20 and 21, except that the outer surface (0 mm, bottomed) was not polished, and each characteristic was measured and evaluated. The results are shown in Table 3.
Shown in. The surface roughness of the sintered surface of the magnesium oxide sintered body cylinder was measured by a surface roughness measuring instrument (manufactured by Tokyo Seimitsu Co., Ltd.), and an average surface roughness (Ra) of 0.83 μm was obtained.

Comparative Example 8 Magnesium oxide (purity 9
9.9%) sintered cylinder (ID70 x OD80 x H40
Oxide superconducting magnetic shields were obtained in the same manner as in Examples 20 and 21, except that the outer surface (0 mm, bottomed) was optically polished to 2 μm diamond abrasive grains, and each characteristic was measured and evaluated.
The results are shown in Table 3. In addition, when the surface roughness of the obtained polished surface was measured by a surface roughness measuring instrument (manufactured by Tokyo Seimitsu Co., Ltd.), an average surface roughness (Ra) of 0.08 μm was obtained.

(Comparative Example 9) An oxide superconducting magnetic shield was obtained in the same manner as in Example 23 except that the magnesium oxide layer was not polished, and each characteristic was measured and evaluated.
The results are shown in Table 3. The surface roughness of the magnesium oxide layer was measured with a surface roughness profiler (manufactured by Tokyo Seimitsu Co., Ltd.), and an average surface roughness (Ra) of 14.55 μm was obtained.

Comparative Example 10 An oxide superconducting magnetic shield was obtained in the same manner as in Example 25 except that the silver layer was not polished, and each characteristic was measured and evaluated. The results are shown in Table 3. In addition, when the surface roughness of the silver layer was measured by a surface roughness measuring instrument (manufactured by Tokyo Seimitsu Co., Ltd.), the average surface roughness (R
a) 14.03 μm was obtained.

Comparative Example 11 Magnesium oxide (purity 9
9.9%) sintered cylinder (ID30 x OD36 x H10
(0 mm) was not polished, and an oxide superconducting magnetic detection coil was obtained in the same manner as in Example 31 except that the addition amount of silver powder was 1.0% by weight, and each characteristic was measured and evaluated. The results are shown in Table 3. The surface roughness of the sintered surface of the magnesium oxide sintered body cylinder was measured with a surface roughness measuring instrument (manufactured by Tokyo Seimitsu Co., Ltd.), and the average surface roughness (Ra) was obtained.
0.86 μm was obtained.

(Comparative Example 12) Magnesium oxide (purity 9
9.9%) sintered cylinder (ID30 x OD36 x H10
(0 mm) outer surface was optically polished to 2 μm diamond abrasive grains, and the oxide superconducting magnetic detection coil was obtained in the same manner as in Example 31 except that the addition amount of silver powder was 1.0 wt%. evaluated. The results are shown in Table 3. In addition,
When the surface roughness of the obtained polished surface was measured by a surface roughness measuring instrument (manufactured by Tokyo Seimitsu Co., Ltd.), the average surface roughness (Ra) was obtained.
0.08 μm was obtained.

[0052]

[Table 3]

As a result of the above examples and comparative examples, all of the examples within the scope of the present invention showed good characteristics, but among the comparative examples, the substrate or the intermediate layer was not subjected to polishing treatment. The liquid phase flowed out during firing at the partial melting temperature, and although the film thickness was thin and the critical current was small except for the liquid phase outflow part, the prescribed critical current density was obtained. Did not show superconducting properties. Further, among the comparative examples, the one in which the substrate or the intermediate layer was optically polished to 2 μm diamond abrasive grains did not cause the outflow of the liquid phase at the time of firing, but when a cooling / heating cycle of liquid nitrogen and room temperature was carried out, two cycles were obtained. The oxide superconducting layer was peeled from the substrate or the intermediate layer in the eye.

[0054]

As described above, according to the present invention,
Since liquid phase outflow during melting of the oxide superconducting layer or firing at partial melting temperature can be prevented, it is possible to obtain an oxide superconducting layer with a sufficient film thickness, and to prepare a detection coil, etc. It is possible to control the width. Further, if the average surface density (Ra) of the substrate or the intermediate layer is controlled within the range of the present invention, no decrease in adhesion with the oxide superconducting layer is observed.

Claims (11)

[Claims] 1. An oxide superconductor comprising a substrate and an oxide superconducting layer formed on the substrate, wherein the substrate in contact with the oxide superconducting layer has an average surface roughness (Ra) of 0. ．
An oxide superconductor having a thickness of 1 to 0.7 μm. 2. The oxide superconductor according to claim 1, wherein the substrate is made of magnesium oxide. 3. An oxide superconductor comprising an oxidation resistant metal substrate and an oxide superconducting layer formed on the oxidation resistant metal substrate via an intermediate layer, the intermediate layer being in contact with the oxide superconducting layer. The average surface roughness (Ra) is 0.1 to 0.7.
An oxide superconductor characterized by being μm. 4. The oxide superconductor according to claim 3, wherein the intermediate layer is a silver layer formed by thermal spraying on an oxidation resistant metal substrate. 5. The oxide superconductor according to claim 3, wherein the intermediate layer is a magnesium oxide layer formed by thermal spraying on an oxidation resistant metal substrate. 6. The oxide superconducting layer is Bi-Sr-Ca-C.
The oxide superconductor according to any one of claims 1 to 5, which is an oxide of a u-based compound having a multi-layer perovskite structure. 7. The oxide superconductor according to claim 1, wherein the oxide superconducting layer contains 0.5 to 10.0% by weight of silver and / or silver oxide. 8. The oxide superconducting layer contains 0.5 to 5.0% by weight of magnesium oxide and has a film thickness of 10 to 1000 μm.
The oxide superconductor according to any one of claims 1 to 7, wherein m is m. 9. The surface roughness has an average surface roughness (Ra) of 0.1.
On the substrate or the intermediate layer having a thickness of ~ 0.7 μm, a film-shaped molded body exhibiting superconducting properties is formed by heating, and thereafter,
A method for producing an oxide superconductor, which comprises firing at a temperature at which the molded body is melted or partially melted. 10. The molded body contains 0.5 parts of silver and / or silver oxide.
The method for producing an oxide superconductor according to claim 9, wherein the oxide superconductor is added in an amount of -10.0% by weight. 11. A molded body containing magnesium oxide powder of 0.1.
The method for producing an oxide superconductor according to claim 9, wherein the oxide superconductor is added in an amount of 5 to 10.0% by weight.