JPH03265576A - Oxide superconducting laminated body and its production - Google Patents

Abstract

PURPOSE:To improve the peel strength by making the end of a noble-metal sheet on the oxide superconductor layer side thinner than the other parts at the lap joint or providing a complementary relation to the end shape and forming the joint and other parts in the same thickness. CONSTITUTION:The joining parts of the noble-metal sheets 1 and 1' having 50-500mum thickness and consisting of >=1 kind among Ag, Au and Pd are worked into a specified shape, the thickness d of the joint is made smaller than the total thickness of the sheets 1 and 1', an adhesive is applied on the joining parts 2 and 2' which are joined, and the joined sheets are put on a stainless steel substrate through an inorg. adhesive of glass, etc., calcined and bonded. A slurry of the Bi and Y-based oxide superconductor materials is applied on the sheets 1 and 1', dried and then sintered at 800-1100 deg.C in an O2 atmosphere to obtain an oxide superconducting laminated body having 50-5000mum thickness. Alternatively, a complementary relation is provided to the shapes of the ends of the noble-metal sheets, the thickness of the lap joint is made almost equal to that of each sheet, and both ends are joined.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an oxide superconducting laminate and a method for manufacturing the same. More specifically, the present invention relates to an oxide superconducting laminate in which a noble metal plate and an oxide superconductor layer are sequentially laminated on a substrate, and the ends of the noble metal plates are overlapped and bonded, and a method for manufacturing the same.

[Prior Art] In recent years, oxide superconductors have attracted attention due to their high critical temperature, and have been used in the electric power field and nuclear magnetic resonance computed tomography diagnostic equipment (MRI).
It is expected to be used in various fields such as ceImaging) and magnetic shielding. When these oxide superconductors are put into practical use, it is possible to manufacture devices and base materials using the oxide superconductors, but it is not possible to use the conventional method of forming an oxide superconductor layer on an existing base material. Are known.

When forming an oxide superconductor on a substrate, it is necessary to select a substrate material that reacts inertly with the oxide superconductor during firing of the oxide superconductor and does not reduce the superconducting properties, and/or to intervene with an intermediate inert material. It becomes necessary.

Since current oxide superconductors are used after being cooled to liquid nitrogen temperature (77K), each interface is affected by the difference in thermal expansion coefficient between the substrate and/or intermediate inert material and the oxide superconductor during cooling. A structure is needed to alleviate the thermal distortion stress that occurs in the process.

Conventionally, for example, in JP-A No. 63-305574, a substrate of alumina, zirconia, copper, etc. and Y-Ba-C
Palladium (Pd), silver (
A method in which a stabilizing material that does not cause a chemical reaction, such as gold (Ag) or gold (Au), is interposed as an intermediate layer has been proposed;
-173790 also, Y-Ba-Cu-0
A superconducting material in which a stabilizing layer such as #(Ag) is provided as an intermediate layer on a superconductor has been proposed.

[Problem to be solved by the invention] By the way, when producing a large-sized superconducting material, when a noble metal plate such as silver is used as a base and an oxide superconductor layer is laminated on the base, it is necessary to Since the substrate is easily deformed during firing, a thick noble metal substrate is required. In particular, when producing a large cylindrical oxide superconducting laminate, a thick noble metal substrate is required, resulting in an extremely high cost.

Therefore, an oxide superconducting laminate formed by using a material cheaper than noble metal for the base and sequentially stacking a thin noble metal plate and an oxide superconductor on the base is advantageous in reducing manufacturing costs.

However, since the precious metal plate is thin and it is difficult to manufacture a single large noble metal plate, it is necessary to overlap the ends of several precious metal plates and create a large intermediate layer of the noble metal plate as a whole. Become.

However, the method of simply overlapping the ends of precious metal plates,
Alternatively, simply applying an inorganic adhesive such as noble metal paste, glass, a superconductor of the same composition, and/or a mixture thereof to the overlapping portion will not work, as shown in FIG. 6(a). The thickness of the noble metal intermediate layer at the mating joint portion becomes thicker, and a step A is generated at the overlapping end of the noble metal plates on the side of the oxide superconductor M5. As a result, the thickness of the superconductor layer 5 after firing is uneven at this stepped portion, and particularly when manufacturing under firing conditions that involve a melting or semi-melting process of the oxide superconductor, the superconductor layer 5 is Due to the surface tension of the liquid, the thickness of the superconductor layer 5 after firing becomes significantly non-uniform. If the thickness of the superconductor layer 5 or the stepped portion A is not uniform, the critical current value of that portion will decrease, and stress will be concentrated when immersed in liquid nitrogen, as shown in Fig. 6 (b). ), a problem arises in that cracks 6 occur in the superconductor layer 5 at the stepped portion A.

Therefore, the present invention provides the following features in the overlapping joint of precious metal plates:
It is an object of the present invention to provide an oxide superconducting laminate that does not peel or break in a wide temperature range from firing temperature to liquid nitrogen temperature, and does not impair superconducting properties, and a method for manufacturing the same.

[Means for Solving the Problems] According to the present invention, a noble metal plate and an oxide superconductor layer are sequentially laminated on a substrate, and the ends of the noble metal plates are overlapped and bonded. An oxide superconducting laminate, the oxide superconducting laminate comprising at least the end portion of the noble metal plate on the oxide superconductor layer side of the precious metal plate in the overlapping joint portion, which is thinner than the other portion. body(
a first superconducting laminate), and an oxide superconducting laminate in which a noble metal plate and an oxide superconductor layer are sequentially laminated on a substrate, and the ends of the noble metal plates are overlapped and bonded, An oxide superconducting laminate (second superconducting laminate).

In addition, in the first superconducting laminate, a noble metal plate formed by overlapping and bonding the ends is coated on the base via an inorganic adhesive, and then an oxide superconductor raw material is coated on the noble metal plate. A method for manufacturing an oxide superconducting laminate comprising coating and firing, the method comprising processing at least the end of the noble metal plate on the oxide superconductor layer side among the noble metal plates at the overlapping joint part, and reducing the thickness of the end part. Furthermore, the second superconducting laminate is formed by coating the base with a precious metal plate formed by overlapping and bonding the ends with an inorganic adhesive. A method for producing an oxide superconducting laminate, which comprises: coating the noble metal plate with an oxide superconductor raw material and firing it; Each can be manufactured by a method in which the shapes of the end portions have a mutually complementary relationship and the thickness of the overlapping joint portion is formed to be approximately equal to the thickness of each noble metal plate.

[Function] The present invention comprises an oxide superconductor laminate formed by inserting a noble metal plate between a base and an oxide superconductor layer, in which the ends of the noble metal plates are overlapped and bonded. The invention relates to a laminate and a method for manufacturing the same, and in particular, among the precious metal plates at the overlapping joint, at least the edge of the noble metal plate on the oxide superconductor layer side is formed to be thinner than the other part, or This is characterized in that the end shapes of the respective precious metal plates at the overlapping joint portion have a mutually complementary relationship, and the thickness of the overlapping joint portion is formed to be approximately equal to the thickness of each noble metal plate.

Since the shape of the end of the noble metal plate at the overlapping joint was specified in this way, the resulting oxide superconducting 8iR body was
It does not peel off in a wide temperature range from firing temperature to liquid nitrogen temperature, and can stably maintain superconducting properties such as critical current (Jc).

The substrate used in the present invention is not particularly limited, or
For oxide superconductors, metals such as nickel, iron, stainless steel, Hastelloy, Inconel, Incoloy, and enameled steel plates that can maintain their base structure at about 800 to 1100°C, which is the firing temperature of oxide superconductors, are preferable. In addition to metals, ceramics such as alumina, zirconia, magnesia, and strontium titanate are also commonly used as substrates, but metal substrates are the least applicable because of their low manufacturing cost and ease of processing. It has high value for wide industrial use. Therefore, it is industrially useful to obtain a stable superconductor with high superconducting properties on a metal substrate.

The material of the noble metal plate as the intermediate layer in the present invention includes silver, gold, palladium, platinum, ruthenium, rhodium,
One or a combination of two or more of osmium and iridium, with a melting point of 900° C. or higher, is used.

The thickness of the precious metal plate is 50 g, m or more, preferably 50 g, m or more.
-500 gm, more preferably 50-200 gm. Even if it exceeds 500 ILm, the effect of stabilizing the superconductor layer will not increase, and on the contrary, the cost will increase. In addition, if the thickness is less than 50p or m, there is a risk that the substrate may be exposed due to non-uniformity, or during firing of the oxide superconductor, noble metal elements may diffuse into the molten superconductor and form the interface between the noble metal plate and the substrate. It is difficult to obtain a good oxide superconducting laminate because the active superconductor flows in and reacts with the substrate components, significantly impairing the superconducting properties.

The type of oxide superconductor used in the present invention is not particularly limited, and includes Bi-based, Y-based, TI-based, La-3r-based, L
In addition to various oxide superconductors such as a-Ba-based oxide superconductors, Bi-based oxide superconductors having a multilayer herovskite structure in which Bj is replaced with pb''C are used.

In the present invention, the oxide superconductor layer may be formed by spray coating or powder coating using an oxide superconductor raw material powder, or an unfired body formed by molding the oxide superconductor raw material powder by a doctor blade method. Alternatively, it may be formed by pasting a sintered body that has been fired to exhibit superconducting properties.

The thickness of the oxide superconductor layer may be 50 to 5000 #Lm, preferably 100 to 2000 #Lm. 500
If it is thicker than 0 m, the superconductor layer tends to peel off, and if it is thinner than 50 pm, the thickness tends to be uneven and sufficient superconducting properties cannot be obtained.

Further, the oxide superconducting laminate of the present invention can be formed into various shapes such as a flat plate shape and a cylindrical shape.

Next, the stacking and joining of precious metal plates will be explained.

In the oxide superconducting laminate of the present invention, the method of overlapping and joining noble metal plates can be roughly divided into two types.

First of all, there is a joining method in which at least the end portion of the noble metal plate on the oxide superconductor layer side of the overlapping joint portion is formed to be thinner than the other portion. For example, this joining method is shown in Fig. 1 (a), (b), and (c).
, Fig. 2(a) (b), and Fig. 3(a) (b)
(c) Those shown in (d) are listed as typical.

Here, FIG. 1(a) shows a case where the end portions of each precious metal plate are processed to form the overlapping part thickness d thinner than the sum of the thicknesses of the respective noble metal plates, and FIG. 1(b) ) and (C) respectively show the case where only the end of the noble metal plate on the oxide superconductor layer side was processed. Note that FIGS. 1(a), 1(b), and 1(c) show the case where the end portions of the precious metal plates are processed before the overlapping portions are fired.

In addition, in Fig. 2 (a), the thickness d of the overlapping part end exceeds the thickness of the lower precious metal plate l, or does not exceed the sum of the thicknesses of the lower noble metal plate l and the upper noble metal plate 1', and the upper Fig. 2(b) shows the case where the end processing angle C of the precious metal plate 1' is 0〈C〈90°, and in Fig. 2(b), the thickness d of the overlapping part end is the same as the thickness of the lower precious metal plate l, and the upper precious metal The edge processing angle of plate 1' is C or O<c
The case of <90° is shown.

Figures 3 (a), (b), (c), and (d) respectively show the state in which the ends of the upper precious metal plate 1' are processed into curved shapes.
Figure 3 (a) shows the overlapped end thickness d and the lower precious metal plate l.
exceeds the thickness of the lower precious metal plate l and the upper precious metal plate 1'
Fig. 3(b) shows the case where the radius of curvature R is less than the thickness of the overlapping part of the upper precious metal plate 1'. The case is shown in which the thickness is the same as that of the noble metal plate 1, but R exceeds the thickness of the overlapped portion of the upper noble metal plate 1'. Also, Fig. 3(c)(d)
are the cases in which the thickness d of the end of the overlapped portion is the same as the thickness of the lower precious metal plate l, respectively, and show a state in which the end of the upper precious metal plate 1' is formed by combining curved surface processing. .

In addition, Fig. 2 (a) (b), Fig. 3 (a) (b) (
c) (d) shows the case where the end portions of the precious metal plates are processed after the overlapping portions are fired.

Second, there is a joining method in which the end shapes of the precious metal plates at the stacked joint are complementary to each other, and the thickness of the stacked joint is approximately equal to the thickness of each precious metal plate. It is. For example, this joining method is shown in Fig. 4 (
Typical examples include those shown in a) and (b).

Here, in FIG. 4(a), the end shapes of the respective precious metal plates are tapered and complementary to each other, and when they are overlapped, the overlapped joint thickness d is the same as each other. The thickness is almost the same as that of a precious metal plate. Fig. 4(b) shows the end portions of each precious metal plate processed thinly to have a mutually complementary shape, and then overlapped (fitted).The overlap joint thickness d is These are the thickness and distance between each precious metal plate. Note that FIGS. 4(a) and 4(b) show the case where the end portions of the precious metal plates are processed before the overlapping portions are fired.

Preferable methods for processing the edges of the precious metal plate include, for example, a polishing method using a tarinder, sandpaper, etc., but the method is not limited to this, and other mechanical processing, chemical processing, laser processing, etc. may also be used. I'll come.

Next, a method for manufacturing an oxide superconducting laminate according to the present invention will be explained.

First, the edges of several precious metal plates are processed into the desired shape. Next, the ends of the noble metal plates are overlapped to form a noble metal plate of a predetermined size, which is then coated onto the substrate via an inorganic adhesive such as glass, and bonded by firing.

Next, an oxide superconductor raw material is further coated on a noble metal plate and then baked to produce an oxide superconductor laminate.

Note that an oxide superconducting laminate may also be produced by firing and bonding a noble metal plate onto a substrate, processing the end of the noble metal plate into a desired shape, coating the noble metal plate with an oxide superconductor raw material, and then baking it. I'll come.

Further, after the ends of the noble metal plates are processed into a desired shape, the ends of the noble metal plates are overlapped to form a noble metal plate of a predetermined size, and then the noble metal plates are bonded onto the substrate.

Then, after joining, the edges of the noble metal plates can be processed, and finally, the oxide superconductor raw material is coated on the noble metal plates and then baked, thereby producing an oxide superconducting laminate.

In this case, when an organic binder or organic solvent is used, such as by slurry coating, in forming the oxide superconductor layer,
It is preferable to perform a heat treatment in an oxygen-containing atmosphere at 500 to 930° C. for a certain period of time as a pretreatment before firing to reduce the amount of residual carbon to less than 0.5% by weight.

Firing in the present invention is performed in an atmosphere of oxygen or an oxygen-containing gas in the air, but depending on the type of superconductor, it is performed in a nitrogen gas atmosphere during cooling. The firing temperature may be appropriately selected depending on the superconductor raw material and the intended superconductor type, or it may be performed at a temperature of 800°C or higher and a maximum temperature of 1100°C.

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to these examples.

(Examples 1-2) 160mm (length) x 160mm (radius) as a precious metal plate
Use 4 silver plates 1 and 1' with a thickness of
After processing it into the shape shown in Figure 4 (a) and (b), which has a weight of 0 gm, Bi25r2 was applied to the overlapping joint surface 2.2'.
An adhesive having a composition of Ca(:u20x) was applied and the respective ends were joined with 20 cm overlap to produce a silver plate of a predetermined size.

Next, the silver plate produced in this way was
It was bonded onto a flat 5US304 stainless steel plate substrate of 0 mm x 2 mm (thickness) via stainless steel enamel (SC-2710S, manufactured by Nippon Frit Co., Ltd.) as an S machine adhesive.

Next, a slurry made by mixing Bi-based oxide superconductor raw material powder with ethyl alcohol and PVB (polyvinyl butyral) was spray coated, and after drying, the maximum temperature was 8.
It was fired in an oxygen atmosphere at 90''C to obtain a flat oxide superconductor laminate in which an oxide superconductor (Bi2Sr, CaCu2011) was laminated on a silver plate.

This laminate was held in liquid nitrogen at -196°C for 1 hour, then heated to 20°C and held at this temperature for 1 hour, and a bonding strength test was conducted using a cold/hot cycle, and 300+mX
A test piece of a certain size including the overlapping joint of precious metal plates is cut out from the oxide superconducting laminate of 300×2■■ at the position shown in 14 in Figure 5, and the The superconducting properties (critical current density value) in the superconducting layer were measured, and the relative values when the superconducting property value of the test piece cut out from the section 11 in Figure 5 was taken as 100 are shown in Table 1. Shown below.

Similarly, each of the other positions 12.1315 shown in FIG.
A test piece was cut out from the sample and its superconducting properties were measured. Table 2 shows the results.

(Examples 3 to 5) The overlapping joint of 1.1' silver plates with a thickness of 3001 Lm was
As shown in FIGS. 1(a), (b), and (c) and Table 1, the method was the same as in Examples 1 and 2, except that the overlapping portion thickness d was formed to be thinner than the total thickness of each noble metal plate. An oxide superconducting laminate was prepared using the method described above, and a test was conducted in the same manner as in Examples 1 and 2. The results are shown in Table 1.

(Examples 6-7) The overlapping joints of silver plates 1 and 1' having a thickness of 300 gjl were processed and overlapped as shown in FIGS. 2(a) and 2(b) and Table 1. In this example, the end portions were processed after the overlapping portions of the silver plates were fired. Except for the above, an oxide superconducting laminate was produced in the same manner as in Examples 1 and 2, and tested in the same manner as in Examples 1 and 2. The results are shown in Table 1.

(Examples 8 to 12) The overlapping joint of silver plates 1 and 1' with a thickness of 300 gm was
An oxide superconducting laminate was prepared in the same manner as in Examples 6 and 7, except that it was processed and stacked as shown in Figure 3 (a) (b) (c) (d) and Table 1. The test was carried out in the same manner as in Examples 1-2. The results are shown in Table 1.

(Examples 13 to 16) As shown in Table 1, the overlapped portions of silver plates 1.1' having different thicknesses were processed as shown in FIG. 1(a) and Table 1, and each silver plate 1.1' was processed as shown in FIG. 1' was bonded in the same manner as in Examples 6 and 7, the silver plate was bonded to the base by firing, and then
) The tip portion 4' of the silver plate l'' is shaped like the curved surface 3 in Figure 3(d) (R1 > 1000, R2 > 110
00u) processed.

Except for the above, an oxide superconducting laminate was produced in the same manner as in Examples 1 and 2, and tested in the same manner as in Examples 1 and 2. The results are shown in Table 1.

(Examples 17-18) Oxidation was carried out in the same manner as in Examples 13-16, except that the overlapping part of the silver plate 1 was processed as shown in FIG. 1(b) or FIG. 1(C). Example 13: Fabricating a superconducting laminate
The test was conducted in the same manner as in 16. Table 1 shows the results.
Shown below.

(Examples 19 to 22) Oxide superconducting laminates were produced in the same manner as in Example 15, except that the substrates were changed to Inconel 600, Inconel 625, and Incoloy 805.5US310S. I conducted a test. Table 1 shows the results.
Shown below.

(Comparative Examples 1 to 4) Oxide superconducting laminates were produced in the same manner as Examples 1 to 2 using silver plates with different thicknesses as shown in Table 1, with the edges of the silver plates left unprocessed, The test was conducted in the same manner as in Examples 1-2. The results are shown in Table 1.

Table 2 As is clear from the results shown in Tables 1 and 2, by processing the edges of the precious metal plate as in the present invention, the oxide content at the flanged joint of the noble metal plate was higher than that of the unprocessed one. The thickness of the superconductor layer is almost the same as the thickness of the oxide superconductor layer other than the overlapping part, and the resulting large oxide superconductor laminate has an almost uniform critical current density over the entire surface, and has a high resistance to thermal cycle tests. It can be seen that an oxide superconducting laminate that is difficult to peel or break and does not impair superconducting properties can be obtained.

[Effects of the Invention] As explained above, according to the present invention, the ends of the precious metal plates are processed into a specific shape and the precious metal plates are overlapped and joined.
The obtained oxide superconducting laminate has the advantage that it does not peel off in a wide temperature range from the firing temperature to the liquid nitrogen temperature, and does not impair its superconducting properties.

[Brief explanation of drawings]

Figure 1 (a) (b) (c), Figure 2 (a) (b)
, Figure 3(a)(b)(C)(d) and Figure 4(
a) and (b) are cross-sectional explanatory diagrams showing examples of the end shapes of the stacked joints of noble metal plates used in the oxide superconducting laminate of the present invention, and FIG. 5 is a test piece cut out from the oxide superconducting laminate. An explanatory diagram showing the position of Fig. 6 (a
) (b) is a cross-sectional explanatory view showing a state in which a superconductor layer is laminated on the noble metal plate joint portion when the noble metal plates are simply stacked. 1.1'...Precious metal plate (silver plate), 2.2'-...Overlapping joint surface, 3...Curved surface shape, 4'...Tip portion,
5...Superconductor layer, 6...Crack. Figure Figure

Claims (4)

[Claims] (1) An oxide superconducting laminate in which a noble metal plate and an oxide superconductor layer are sequentially laminated on a substrate, and the end portions of the noble metal plates are overlapped and joined, wherein the noble metal plate at the overlapped joint is An oxide superconducting laminate characterized in that the end portion of at least the noble metal plate on the oxide superconductor layer side is thinner than the other portion. (2) An oxide superconducting laminate in which a noble metal plate and an oxide superconductor layer are sequentially laminated on a substrate, and the ends of the noble metal plates are overlapped and joined, and each precious metal at the overlapped joint is 1. An oxide superconducting laminate characterized in that the end shapes of the plates are complementary to each other and the thickness of the stacked joint is approximately equal to the thickness of each noble metal plate. (3) Oxidation consisting of coating a substrate with a noble metal plate formed by overlapping and bonding the ends with an inorganic adhesive, and then coating the noble metal plate with an oxide superconductor raw material and firing. A method for manufacturing a superconducting laminate, the method comprising processing at least an end of the noble metal plate on the oxide superconductor layer side among the noble metal plates at the overlapping joint, and comparing the thickness of the end with the other part. A method for manufacturing an oxide superconducting laminate, characterized in that it is formed thinly. (4) Oxidation consisting of coating a substrate with a noble metal plate formed by overlapping and bonding the ends with an inorganic adhesive, and then coating the noble metal plate with an oxide superconductor raw material and firing. A method for manufacturing a superconducting laminate, comprising: processing the ends of each noble metal plate at the overlapping joint, so that the end shapes have a mutually complementary relationship, and the thickness of the overlapping joint is adjusted to A method for manufacturing an oxide superconducting laminate, characterized in that the thickness of the oxide superconducting laminate is approximately equal to that of the plate.