JPH0224911A - Ceramic superconductor and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a ceramic superconductor not generating quenching phenomenon and having large critical current by composing the ceramic superconductor by laminating a ceramic superconductor layer and a conductor layer parallel to the periphery of the ceramic superconductor at the cross section and arranging superconductor crystal grains along and parallel to the periphery. CONSTITUTION:A sheet compact 12 is formed by employing the powder of ceramic superconductor and organic binder. And also a conductor sheet compact 13 not exhibiting superconductivity is formed by employing silver grains and organic binder. A superconductor cylindrical compact 11 is further formed by employing the materials same as those for the sheet 12. The sheet 13 is wound around the compact 11 as a core one turn and the sheet 12 is further wound around the sheet 13 one turn. By repeating this, the sheets 13 and 12 are wound around each other by turns, for instance four turns. The compact 11 is pinched by two plates 15 and 16 to be lengthened in line by pressure with transferring the plates 15 and 16 right and left. The laminated body is sintered to be a ceramic superconductor. At the time, ceramic superconductor grains are arranged along and parallel to the periphery of the ceramic superconductor.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a structure of a ceramic superconductor and a method of manufacturing the same.

Conventional technology Ceramic superconductors such as the Ba-Y-Cu-0 system exhibit superconductivity up to high temperatures, so they do not require the use of expensive liquid helium or coolers, and are therefore being considered for application in various fields. has been done.

When a part of a superconductor breaks its superconducting state for some reason, such as when a large current is passed through it to create a strong magnetic field using the superconducting phenomenon, the temperature of that part partially increases. In order to prevent the quench phenomenon, in which the superconducting state heats up the surrounding area, the superconducting state dissipates in a ripple manner, and the energy is released as heat all at once, superconducting, as already proposed by the inventors, is Although not shown, it was necessary to use it in a composite with a conductor that has low electrical conductivity and small temperature changes.

Problems to be Solved by the Invention It is an object of the present invention to provide a structure of a ceramic superconductor that prevents the quench phenomenon and has a large critical current, and a method for manufacturing the same.

Means for Solving the Problems A linear ceramic superconductor has a structure in which a superconducting ceramic layer and a conductor layer that does not exhibit superconductivity are laminated parallel to the outer peripheral surface in a cross section, and the superconductor The porcelain crystal grains are oriented parallel to the outer circumferential surface.

Alternatively, in a linear ceramic superconductor, the superconducting porcelain and the non-superconducting conductor have a continuous and mixed structure, and the crystal grains of the superconducting porcelain are parallel to the outer peripheral surface. The structure has a planar orientation.

In addition, as a manufacturing method, superconducting ceramic particles and non-superconducting conductive powder, which have been grown into plate shapes, are used as starting materials, and a binder is added to each of these and kneaded to create a clay-like raw material that has superconducting properties. The process involves forming a columnar shape in which a conductor and a non-superconducting conductor are laminated concentrically, a step of stretching the formed body in the length direction of the columnar shape into a linear shape, and a step of firing it.

Alternatively, the process of forming a clay-like raw material into a columnar shape by using as a starting material a mixture of superconducting porcelain particles that have grown into plate shapes and a conductor that does not exhibit superconductivity, and adding a binder to this and kneading it into a columnar shape. The process involves stretching the body in the longitudinal direction of the column, stretching it linearly, and firing it.

Function In the ceramic superconductor of the present invention, the superconducting ceramic particles are oriented and sintered, so the adhesion area between the superconducting ceramic particles is large and the continuity is improved, so that superconducting Critical current increases. Moreover, the bonding area with the conductor layer that does not exhibit superconductivity becomes large, and the effect of preventing the quench phenomenon is also large.

Further, according to the method for manufacturing a ceramic superconductor of the present invention, ceramic superconductor porcelain particles that have been grown in advance into a plate shape are used and formed into a linear shape, so that the particles are plane-oriented.

Examples Example-1 As starting materials for ceramic superconductors, chemically high purity f20a+ SrCO3+ CaCO3+C
ub, was used. The molar ratio of these powders is Bf
: Sr: Ca: Cu becomes 1:1:1:2,
It was weighed so that the total amount was 150 g. These powders were placed in a polyethylene ball mill container with a capacity of 1600 cc, and 600 stabilized zirconia boulders with a diameter of 5 mm were placed.
g, and 150 g of high-purity alcohol for 17 hours. After drying, this powder was molded at 250 kg/cm2, placed in an alumina container, and inserted into a tubular furnace core tube.
Flow the oxygen gas at a flow rate of 10 cm per minute, and
The temperature was raised to 'C at a rate of 200°C/hr, held for 4 hours, and then lowered to room temperature at a rate of 200°C/hr. This calcined product is
After cooling, it was coarsely crushed in a mortar to 25 mesh passes, and then crushed with high purity alcohol for 6 hours using the aforementioned ball mill and cobblestones. When observed under a scanning microscope, the pulverized powder had a uniform plate shape with an average thickness of 0.2 μm and a diameter of 2.5 μm.

Next, the method for manufacturing the molded body will be shown in accordance with FIG. After drying, this powder was kneaded in a mortar with 15vt% (50vt% ethanol, ethyl cellulose resin mixture) of the powder weight of an organic binder, 3vt% dibutyl phthalate, and 10wt% glycerin, and was mixed with a diameter of 4 mm and a length of 100 m.
m cylindrical shape 11 (Figure 2 a), thickness 1 mm and width 100 m
It was molded into a sheet 12 (FIG. 2b) of m.

The starting material for a conductor layer that does not exhibit superconductivity is spherical and has an average particle size of 0. Using 8 μm silver particles, the powder weight was 32
Vt% (50vt% ethanol, ethyl cellulose resin mixture) organic binder, 8vt% dibutyl phthalate, and 20wt% glycerin were kneaded in a mortar to form a sheet 13 with a thickness of 1 mm and a width of 100 mm (Fig. 2 a).
It was molded into.

Next, as shown in FIG. 2d, the above-mentioned superconductor cylindrical molded body 11 is used as a core, the conductor sheet 13 is wound around it once, and the superconductor sheet 12 is wrapped around it once. rolled. Thereafter, the conductor sheet 13 and the superconductor sheet 12 were alternately wound one round each in four layers. The molded body has a diameter of 24 mm.
It became a columnar shape 14 with a length of 100 mm.

The above cylindrical molded body 14 is made of 2
It was sandwiched between two flat plates 15 and 16, and stretched linearly by applying pressure while moving the flat plates from side to side.

The molded body in which the above-mentioned superconductor layer and conductor layer were laminated had a diameter of 7 mm. This laminate was cut into a length of 40 mm.

The above-mentioned laminate was placed in an alumina porcelain container on which 100 mesh baths of coarse-grained alumina was spread, placed in an electric furnace, heated to 350°C at a rate of 20°C/hour, and held for 10 hours to incinerate the binder. It was then cooled down.

To sinter the sample, the above-mentioned binder was incinerated and the sample was inserted into the core tube of a tubular furnace together with the container, and while oxygen gas was flowing at 5 cm/min, the temperature was raised to 875°C at a rate of 300"C/hour, and after holding for 2 hours. The temperature was lowered at 300°C/hour.

FIG. 1 shows a cross-sectional view of the produced ceramic superconductor. 1 is a ceramic superconductor sintered body layer, and 2 is a silver conductor layer. When the fracture surface of the sintered body perpendicular to the line direction was observed using a scanning electron microscope, it was found that the superconductor layer ceramic particles were plane-oriented parallel to the outer peripheral surface.

FIG. 3 shows an enlarged schematic diagram of a part of the cross section. 21 is a superconductor ceramic particle 22 is a copper conductor particle.

Table 1 shows the critical current for superconductivity at 70K and the unit length at 150K (a temperature at which ceramics do not exhibit superconductivity) per unit area of the prepared sample (No. 1) (parallel to the stacking direction). Shows the resistivity of In addition, as a comparative example, a sample without a metallic silver layer and molded using the same method as the example (No. 2) (with plane orientation)
, molded by powder press (uniaxial press) (N
o, 3) (no plane orientation) values are also shown.

Table 1: Comparative examples outside the scope of the present invention As is clear from Table 1, the ceramic superconductor having the structure of the present invention has a large critical current, and when superconductivity is broken. The resistivity of is also small.

A sample that does not contain a conductor layer has a high resistivity when superconductivity is broken. Samples with unoriented ceramic layers have a small critical current.

Example 2 The same starting material as in Example 1 was used as the starting material for the ceramic superconductor. As starting materials for the conductor layer that does not exhibit superconductivity, the same materials as in Example 1 and plate-shaped silver, gold, platinum, and palladium powders having an average thickness of 0.15 μm and a diameter of 1°5 μm were used. These powders were mixed so that the volume fraction of the non-superconducting conductor became a predetermined value, and then kneaded in the same manner as in Example-1 to form a powder with a diameter of 20 m.
It was molded into a cylindrical shape with a length of 100 mm. This was stretched, cut, and fired in the same manner as in Example-1.

Table 2 shows the starting material composition, shape, and volume fraction of the conductor of the prepared sample, and Table 3 shows the critical current of superconductivity at 170 K per unit area of the prepared sample (parallel to the stacking direction). and the resistivity per unit length at 150K (a temperature at which ceramics do not exhibit superconductivity). In addition, samples in which the volume fraction of the conductor is 30% and 65% (No. 12.1
4) is a comparative example in which the conductor 12 and the ceramic 14 are localized and not continuous, which is out of the scope of the present invention.

In the other samples, the superconductor and the conductor were both continuous and mixed. Figure 4 shows an enlarged schematic diagram of a portion of the fracture surface perpendicular to the line direction of the sample. 31
is a superconducting ceramic layer, and 32 is a conductive metal layer.

The asterisks in Table 3 indicate comparative examples outside the scope of the present invention. Kiguchi in Table 3 indicates comparative examples outside the scope of the present invention, as is clear from Tables 2 and 3. Samples in which each body is continuous and have a mixed structure, and the crystal grains of the superconducting porcelain have a planar orientation, have a large critical current for superconductivity, and the superconductivity is broken. When the resistivity is small. A plate-shaped starting material for the conductor is more preferable as a manufacturing method because the orientation of the superconducting ceramic particles is improved and the critical current is increased.

Example 3 Chemically high purity T1202+ BaCO2, Ca CCh is used as the starting material for the ceramic superconductor.

CuO9 was used. These powders have a molar ratio Tl:
The ratio of Ba: Ca: Cu was 2: 2: 2: 3, and the total amount was 150 g. These powders were mixed, calcined, pulverized, and formed into cylinders and sheets in the same manner as in Example-1. When observed under a scanning microscope, the pulverized powder had a uniform plate shape with an average thickness of 0.15 μm and a diameter of 1.5 μm.

The starting material for a conductive layer that does not exhibit superconductivity is a plate-like material with an average thickness of 0.2 μm and an average diameter of 2.0 μm. Gold particles of 0 μm were used and formed into a sheet in the same manner as in Example-1. These molded bodies were concentrically laminated and molded in the same manner as in Example-1.

The above cylindrical molded body is produced by using an injector 42 with a parallel hole 41 in which the outlet is gradually narrowed as shown in the cross section in FIG. The molded product was injected from the outlet parallel hole by applying pressure from the rear and molded into a linear shape. Superconductor layer 43 after injection
The molded body in which the conductor layer 44 is laminated has a diameter of 8 mm, a superconductor layer with a diameter of 1.3 mm in the center, and a superconductor layer with a diameter of 1.3 mm in the center, and around it,
Five conductor layers and superconductor layers each having a thickness of 0.33 mm are laminated alternately. This laminate has a length of 40mm
It was cut into These laminates were fired in the same manner as in Example-1.

Table 4 shows the critical current of superconductivity per unit area of the prepared sample (No. 21) (parallel to the stacking direction) at 70K and the unit length at 150K (a temperature at which ceramics do not exhibit superconductivity). Shows the resistivity of As a comparative example, a sample without a gold layer and molded using the same molding method as in the example (No. 22) (with surface orientation), and a specimen molded by a powder press (uniaxial press) (
The value of No. 23) (no plane orientation) is also shown.

Table 4 Comparative Examples Outside the Scope of the Invention As is clear from Table 4, ceramic superconductors having the structure of the present invention have a large critical current and when superconductivity is broken. The resistivity of is also small.

A sample that does not contain a conductor layer has a high resistivity when superconductivity is broken. Samples with unoriented ceramic layers have a small critical current.

Furthermore, by using the manufacturing method of this embodiment, a linear molded body with good ceramic orientation can be easily manufactured with good mass production.

Example-4 The starting materials for the ceramic superconductor are chemically highly pure T12031 BaCO3 and CaC0a.

CuOr was used. These powders have a molar ratio Tl
: Ba: Ca: Cu is 2: 2: 2
: 3, and the total amount was weighed to be 150 g. These powders were mixed, calcined, and ground in the same manner as in Example-1. The starting material for a conductive layer that does not exhibit superconductivity is a plate with an average thickness of 0.15 μm and an average diameter of 1.5 μm.
palladium particles were used. These powders were mixed so that the volume percent of palladium was 45%, molded into a cylinder in the same manner as in Example-2, and formed in the same manner as in Example-3.
Injected from an injection machine. This linear molded body was fired in the same manner as in Example-1.

Table 5 shows the critical current of superconductivity at -70K per unit area of the prepared sample (No. 31) (parallel to the stacking direction) and the unit length at 150K (a temperature at which ceramics do not exhibit superconductivity). Shows the resistivity of As a comparative example, a sample without a palladium layer was used.
The molding method is the same as in the example (No. 32) (with plane orientation), palladium is mixed but powder press (
The values of the sample (No. 33) (no plane orientation) formed using a uniaxial press are also shown.

Table 5: Comparative examples outside the scope of the present invention As is clear from Table 5, the ceramic superconductor having the structure of the present invention has a large critical current, and when superconductivity is broken. A sample that does not contain a conductor layer with a low resistivity will have a high resistivity when superconductivity is broken. Samples with unoriented ceramic layers have a small critical current.

Furthermore, by using the manufacturing method of this embodiment, a linear molded body with good ceramic orientation can be easily manufactured with good mass production.

Example 4 The same starting materials as in Example 1 were used as the starting materials for the ceramic superconductor, and the materials were mixed, calcined, pulverized, and added with a binder in the same manner as in Example 1. Platinum particles having an average thickness of 0.3 .mu.m and an average diameter of 1.5 .mu.m were used as a starting material for a conductor layer that did not exhibit superconductivity, and a binder was added thereto in the same manner as in Example-1. These were injected into an injection machine having six parallel outlet nozzles 51 arranged concentrically as shown in FIG. 6, with ceramic superconductors 52 and conductors 53 arranged alternately. This linear molded body was fired in the same manner as in Example-1.

Table 6 shows the critical current for superconductivity at 70K and the unit length at 150K (a temperature at which ceramics do not exhibit superconductivity) per unit area of the prepared sample (No. 41) (parallel to the stacking direction). Shows the resistance around the area. As a comparative example, a sample without a palladium layer was used.
The values are also shown for those molded by the same molding method as in Examples (No. 42) (with plane orientation) and those molded by powder press (uniaxial press) (No. 43) (without plane orientation).

The end of Table 6 shows comparative examples outside the scope of the present invention.As is clear from Table 6, the ceramic superconductor produced by the manufacturing method of the present invention has a large critical current.
Moreover, the resistivity when superconductivity is broken is also small. Further, in the case where the injection process is performed through multiple nozzles as in this embodiment, the orientation of the ceramic is further improved and the critical current is increased.

Effects of the Invention According to the ceramic superconductor and the method for producing the same of the present invention, since plate-shaped superconducting ceramic particles are used as the starting material, the superconducting ceramic layer is plane-oriented parallel to the wire outer peripheral surface. , the superconducting critical current can be large, and even if superconductivity breaks down, the quench phenomenon can be prevented because the conductor layer is nearby.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the structure of a ceramic superconductor according to an embodiment of the present invention, FIG. 2 is a diagram showing a method for manufacturing the ceramic superconductor, and FIG. 3 is a cross-sectional view of the ceramic superconductor. FIG. 4 is an enlarged schematic diagram of a ceramic superconductor in another example; FIGS. 5 and 6 are cross-sectional views of an injection machine used in other examples.
1... Ceramic superconductor sintered body, 2... Silver conductor layer, 11... Ceramic superconductor cylindrical molded body, 12... Ceramic superconductor sheet-shaped molded body Body, 13... Silver conductor sheet-like molded body, 14...
Cylindrical molded body, 15...16...Parallel plate, 21
...Superconductor ceramic particles, 22 ... Silver conductor particles, 31 ... Superconductor ceramic layer, 32 ... Conductor metal layer, 41 ... Exit parallel hole , 42... Injection machine, 43... Superconductor layer, 44... Conductor layer, 5
1...Exit parallel nozzle, 52...Superconductor,
53...Electric conductor, name of agent Patent attorney Shigetaka Kurino 1 person Figure 1 Ceramic superconductor Shinofuni? 734 and conductive tram stop (e)

Claims (6)

[Claims] (1) The cross section of a linear ceramic superconductor has a structure in which a superconducting ceramic layer and a non-superconducting conductive layer are laminated parallel to the outer peripheral surface, and the crystal grains of the superconducting ceramic A ceramic superconductor characterized by having a plane orientation parallel to the outer peripheral surface. (2) A linear ceramic superconductor has a structure in which the superconducting porcelain and the non-superconducting conductor are continuous and mixed, and the crystal grains of the superconducting porcelain are connected to the outer peripheral surface. characterized by having parallel plane orientation,
Ceramic superconductor. (3) The superconductor porcelain has a Bi-Sr-Ca-Cu-O or Tl-Ba-Ca-Cu-O oxide as its main component, and the conductor is made of gold, silver, platinum, or palladium. The ceramic superconductor according to claim 1 or 2, characterized in that the ceramic superconductor is made of a metal whose main component is at least one of the following. (4) Using superconducting porcelain particles and non-superconducting conductive powder, which have been grown into plate shapes, as starting materials, binders are added to each of these and kneaded to create a clay-like raw material.
A process of forming a column in which a superconductor and a non-superconducting conductor are laminated concentrically, a process of stretching this formed body in the length direction of the column to form a linear shape, and a process of firing this. A method for producing a ceramic superconductor, comprising: (5) Using a mixture of superconducting ceramic particles that have been grown in the form of a plate in advance and a conductor that does not exhibit superconductivity as a starting material,
The method includes the steps of forming the clay-like raw material mixed with a binder into a columnar shape, stretching the formed body in the longitudinal direction of the columnar shape into a linear shape, and firing the same. A method for producing a ceramic superconductor. (6) As starting materials for conductors that do not exhibit superconductivity, gold,
The ceramic superconductor according to claim 4 or 5, characterized in that a plate-shaped powder of at least one metal selected from the group consisting of silver, platinum, and palladium is used. How the body is manufactured.