JP2002080221A - Hollow oxide superconductor and method of producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a large-sized hollow oxide superconductor excellent in electric characteristics, magnetic characteristics and mechanical strength and a method for producing such an oxide superconductor at low cost. provide. SOLUTION: A raw material mixture containing an RE compound (RE is one or more rare earth metal elements containing Y), a Ba compound and a Cu compound is heated and melted at a temperature higher than the melting point of the raw material mixture. Later, in a method of producing an RE-Ba-Cu-O-based oxide superconductor by gradually cooling and growing a crystal, a tubular precursor and an opening of the tubular precursor are mixed from a raw material mixture. Produce a plate-shaped precursor of the size to close, laminate the plate-shaped precursor on top of the cylindrical precursor,
After heating and melting these precursors, they are gradually cooled to grow crystals from the plate-like precursor toward the cylindrical precursor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow oxide superconductor and a method of manufacturing the same, and more particularly, to a hollow oxide superconductor of RE system used for a bulk magnet, a magnetic bearing, a current lead, a magnetic shield, a current limiter, and the like. The present invention relates to an article superconductor and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, elements (La, Nd, Pm, Sm, and E) forming a solid solution of an RE element (rare earth element) and a Ba element.
u, Gd, Tb, Dy, Ho or a mixture thereof), and after heating and melting the raw material mixture containing the RE compound, the Ba compound and the Cu compound at a temperature equal to or higher than the melting point of the raw material mixture, By performing a slow cooling step while adding a gradient to grow crystals, RE-Ba-Cu-
As a method for producing an O-based oxide superconductor, a precursor is formed into a plate shape, and after melting this precursor, a seed crystal is placed on top of the precursor at a temperature immediately before crystallization, and then the temperature is lowered. There is known a method of producing a large oriented crystal reflecting a seed crystal by holding or slowly cooling the crystal.

[0003]

However, in the above-mentioned conventional method, when the precursor is melted and crystallized with a diameter of, for example, 60 mm or more, the stress due to heat shrinkage in the slow cooling step after crystallization is large. In other words, there is a problem that microcracks occur at the edges of the material. In addition, as a bulk magnet used for a linear motor car, magnetic separation, MRI, etc., a ring-shaped bulk magnet with a hollow center is required for the sake of weight reduction and use, but it is crystallized into a plate shape. If the central portion is cut out of the material to form a ring, the cost becomes very high. Also, using only a cylindrical precursor, after melting, seeding, crystallizing and evenly orienting, the bonding portion at the end of crystal growth becomes a weak bonding, and the hollow portion , The superconducting current flowing so as to surround the space becomes very low, and a high magnetic field cannot be generated in the hollow space.

Accordingly, the present invention has been made in view of the above-mentioned conventional problems, and has been made to reduce the size of a large hollow oxide superconductor excellent in electric characteristics, magnetic characteristics and mechanical strength, and to reduce such a hollow oxide superconductor. It is an object of the present invention to provide a method for manufacturing a hollow oxide superconductor that can be manufactured at low cost.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that RE compounds (RE
Is one or more rare earth metal elements containing Y) and B
A RE-Ba-Cu-O-based oxide superconductor is obtained by heating and melting a raw material mixture containing the compound a and the Cu compound at a temperature higher than the melting point of the raw material mixture, and then gradually cooling the crystal to grow crystals. In the method for producing the above, the thermal contraction rate is adjusted to be close to that of the tubular precursor on the top of the tubular precursor (or has the same composition as that of the tubular precursor) And a plate-like precursor of a size to close the opening of the tubular precursor is laminated, and after heating and melting these precursors, gradually cooling from the plate-like precursor toward the tubular precursor side. The electrical and magnetic properties,
Finding that large, hollow RE-Ba-Cu-O-based oxide superconductors with excellent mechanical strength can be manufactured at low cost,
The present invention has been completed.

That is, the method for producing a hollow oxide superconductor according to the present invention comprises a raw material mixture containing an RE compound (RE is one or more rare earth metal elements containing Y), a Ba compound and a Cu compound. Is heated and melted at a temperature higher than the melting point of the raw material mixture, and then gradually cooled to grow crystals, thereby producing a RE-Ba-Cu-O-based hollow oxide superconductor. While producing a tubular precursor from the body, a plate-shaped precursor containing the same element as the RE of the tubular precursor and having a size to close the opening of the tubular precursor is produced, A plate-shaped precursor is laminated on the top of a plate-shaped precursor, and after heating and melting these precursors, they are gradually cooled to grow crystals from the plate-shaped precursor toward the cylindrical precursor. And

In this method for producing a hollow oxide superconductor, the composition of the plate-like precursor is preferably the same as the composition of the cylindrical precursor, and at least the thermal shrinkage of both precursors is close to each other. Preferably, both precursors contain the same RE element. In addition, the plate-shaped precursor preferably has a surface having the same size and the same shape as the surface on which the opening of the cylindrical precursor is opened.

In the above method for producing a hollow oxide superconductor, the temperature at which the precursor is heated and melted is adjusted so that the cylindrical and plate-like precursors are formed of RE _{2 + r} Ba _{1 + s} (Cu _1-d Ag _d ).
O _{5 -y} phase and _{RE 4 + r Ba 2 + s} (Cu 1-d
Ag _d ) ₂ O _10-y phase (−0.2 ≦ r ≦ 0.2, −
0.2 ≦ s ≦ 0.2, 0 ≦ d ≦ 0.05, -0.2 ≦ y
.Ltoreq.0.2).

In this case, after the heating and melting step, a temperature gradient of 1 to 30 ° C./cm is applied above and below the plate-like and tubular precursors so that the upper part of the plate-like precursor is on the low temperature side. It is preferable that the plate-like and cylindrical precursors are gradually cooled to grow crystals. After the heating and melting step, a seed crystal may be provided, and then the plate-like and tubular precursors may be gradually cooled to grow the crystal. Alternatively, after the heating and melting step, a temperature gradient of 1 to 30 ° C./cm is applied above and below the plate-like and tubular precursors so that the upper part of the plate-like precursor is on the low temperature side. After installation, the plate-like and cylindrical precursors may be gradually cooled to grow crystals.

[0010] In the above method for producing a hollow oxide superconductor, the thickness of the plate-like precursor is preferably 5 to 20 mm.

Further, the method for producing a hollow oxide superconductor according to the present invention provides a raw material mixture containing a RE compound (RE is one or more rare earth metal elements containing Y), a Ba compound and a Cu compound. A method for producing a RE-Ba-Cu-O-based hollow oxide superconductor by heating and melting at a temperature higher than the melting point of the raw material mixture and then gradually cooling the crystal to produce a RE-Ba-Cu-O-based hollow oxide superconductor. A precursor having a concave portion on one surface is manufactured from the body, and after heating and melting the precursor, a seed crystal is placed on the surface opposite to the concave portion, and then the precursor is gradually cooled to grow the crystal. Then, the side on which the seed crystal is placed is cut or penetrated through the concave portion.

Further, the hollow oxide superconductor according to the present invention
The body is RE_{1 + p}Ba_{2 + q}(Cu _1-bAg_b)₃O
_7-x(RE is one or more rare earth metal elements,
-0.2≤p≤0.2, -0.2≤q≤0.2, 0≤b
≦ 0.05, -0.2 ≦ x ≦ 0.6)
_{2 + r}Ba_{1 + s}(Cu_1-dAg_d) O_5-yPhase
And RE_{4 + r}Ba_{2 + s}(Cu_1-dAg_d )₂O
_10-yPhase (-0.2≤r≤0.2, -0.2≤s≤
0.2, 0 ≦ d ≦ 0.05, −0.2 ≦ y ≦ 0.2)
A cylindrical oxide superconductor in which at least one phase is finely dispersed
Conductor and the same element as RE in this cylindrical oxide superconductor
And a plate-like member that covers the opening of the cylindrical oxide superconductor
The oxide superconductor is laminated and crystallized integrally.
And features.

In this hollow oxide superconductor, the composition of the plate-like precursor is preferably the same as the composition of the cylindrical precursor, and the two precursors are at least close to each other in heat shrinkage. Preferably, the bodies contain the same RE element.

In the above hollow oxide superconductor, R
E is one or two selected from Nd, Sm, Gd and Dy
It is preferable that at least 50% or more of the elements are contained. Also, the hollow oxide superconductor contains 8 wt% to 60 wt%.
It preferably contains wt% Ag. Further, the hollow oxide superconductor is made of Pt, Pd, Ru, Rh, Ir, Os,
It is preferable to contain 0.05 wt% to 5 wt% (in the case of a compound, the metal is represented by the element weight of the metal alone) of at least one selected from Re and Ce metals and compounds of these metals.

[0015]

DETAILED DESCRIPTION OF THE INVENTION Hollow oxide superconductor according to the invention
In an embodiment of the method for producing a body, the RE compound (RE is Y
Or two or more rare earth metal elements containing
The raw material mixture containing the compound and the Cu compound is mixed with the raw material mixture.
After heating and melting at a temperature higher than the melting point of the body,
By growing crystals in the RE-Ba-Cu-O system
In the method for producing an empty oxide superconductor, the raw material mixture
Plug the tubular precursor from the body and the opening of this tubular precursor
Manufacture a sized plate-shaped precursor and the top of the cylindrical precursor
After laminating plate-like precursors on the
_{2 + r}Ba_{1 + s}(Cu_{1 -D}Ag_d) O_5-yPhase
And RE_{4 + r}Ba_{2 + s}(Cu_1-dAg_d )₂O
_10-yPhase (-0.2≤r≤0.2, -0.2≤s≤
0.2, 0 ≦ d ≦ 0.05, −0.2 ≦ y ≦ 0.2)
At least the temperature Tm at which at least one phase becomes a liquid phase (preferably
(Tm + 50 ° C to Tm + 200 ° C)
Is melted and then peritectic reaction of these phases
RE_{1 + p}Ba_{2 + q}(Cu_1-bAg _b)₃O
_7-xJust before the temperature Tm at which the phase crystallizes (preferably Tm +
The temperature is lowered from 20 ° C. to Tm + 0 ° C.), and the
Up and down the plate and tubular precursors so that the part is on the low temperature side
After applying a temperature gradient to the plate, a seed crystal is placed on the plate-like precursor side
And then RE_{1 + p}Ba_{2 + q}(Cu_1-bAg
_b)₃O_7-xSlightly lower than the temperature at which
(Tm-2 ° C to Tm-20 ° C)
Crystallization of the plate-like precursor in the horizontal direction
And then gradually cooled to raise the cylindrical precursor.
The crystal is grown from below.

Here, if necessary, a plate-shaped precursor portion is cut from the crystallized sample, or a through-hole is formed in the plate-shaped precursor portion to convert the entire precursor into a cylindrical precursor. When it is made into a body, a cylindrical oxide superconductor having a high critical current density without any grain boundaries along the circumferential direction can be manufactured. Such a cylindrical oxide superconductor can be used, for example, for a solenoid magnet by laminating.

The precursor is RE _{2 + r} Ba _{1 + s} (C
u _1-d Ag _d ) O _5-y phase and RE _{4 + r} Ba
Temperature Tm at which at least one phase of _{2 + s} (Cu _1-d Ag _d ) ₂ O _10-y phase becomes a liquid phase (RE _{1 + p} Ba _{2 + q} (Cu _1-b Ag _b ) when the temperature is lowered from a molten state)
The crystallization temperature of the ₃ O _7-x phase is the temperature as shown in FIG. 1 when each rare earth element is used, and when Ag is further added, the temperature is based on each temperature. , And the amount of Ag added as shown in FIG. When a plurality of rare earth elements are mixed, the temperature is a value obtained by multiplying the temperature shown in FIG. 1 by the molar ratio of each rare earth element.

According to such a method, the volume of the precursor can be kept low, the stress due to the heat shrinkage generated in the slow cooling step after crystallization is alleviated, and the generation of cracks can be suppressed. In addition, by laminating plate-like precursors, the entire ring can completely reflect the orientation of the seed crystal without any seams such as grain boundaries, and is a large, hollow oxide superconductor with excellent electromagnetic characteristics. Can be manufactured at low cost.

In the above-described method, if the melting point and the heat shrinkage of the plate-shaped precursor and the cylindrical precursor are significantly different, cracks are likely to occur at the time of heating or cooling. Or at least the same RE element.

Further, when the plate-like precursor has the same shape as the hollow precursor, the orientation of the crystal tends to be reflected from the plate-like precursor to the hollow precursor. It is preferable that the surface of the cylindrical precursor has the same size and the same shape as the surface where the opening of the precursor is opened. Further, the thickness of the plate-like precursor is 12 mm ± 5 m in terms of cost and reproducibility of orientation.
When the thickness is less than 5 mm, a polycrystalline body is apt to be formed due to the reaction with the support material. When the thickness is more than 20 mm, it takes time to grow the crystal in the thickness direction and the production cost increases.

After the step of heating and melting the precursor, a temperature gradient of 1 to 30 ° C./cm is applied above and below the plate-like and tubular precursors so that the upper part of the plate-like precursor is on the low temperature side. After that, a seed crystal is provided, and then the plate-like and cylindrical precursors are gradually cooled to grow the crystal, thereby improving the crystal orientation and the critical current density.

In the above method, when the size of the precursor is relatively small, for example, a diameter of φ60 mm or less, the precursor is formed into a shape having a concave portion on one surface, and the surface on the opposite side to the concave portion is formed. In the same way, the seed crystal is placed and subjected to the melt crystallization treatment. After the crystallization, the surface on the seed crystal side is cut or the recess is penetrated to form a through hole, so that a hollow superconducting material having relatively high characteristics is obtained. It is also possible to make a body.

In the above hollow oxide superconductor, R
E is one or two selected from Nd, Sm, Gd and Dy
When at least 50% or more of the element is contained, the crystal growth rate is increased, and a large crystal can be manufactured in a relatively short time.

Further, when Ag is contained in an amount of 8 wt% or more, Ag becomes RE _{1 + p} Ba _{2 + q} (Cu _1-b Ag _b ).
With mechanical strength is improved _{3 O 7-x} phase in finely dispersed, it is vertical composition deviation is suppressed can be manufactured less hollow oxide superconductor having large crystal defects. On the other hand, when Ag is contained in an amount of 60 wt% or more, the volume fraction of the superconductor is too low, and characteristics such as critical current density are lowered.

Further, the above-mentioned hollow oxide superconductor comprises:
Gold of Pt, Pd, Ru, Rh, Ir, Os, Re, Ce
Genus and one or more compounds selected from these metal compounds
0.05 to 5 wt% (in the case of a compound, only the metal
(Indicated by elementary weight)_{2 + r}Ba
_{1 + s}(Cu_1-dAg_d) O_5-yPhase and RE_{4 + r}B
a _{2 + s}(Cu_1-dAg_d )₂O_10-yFine phase
Has the effect of

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The hollow oxide superconductor according to the present invention and a method for producing the same will be described in detail below with reference to examples.

[Example 1] Sm₂O₃, BaCO₃, C
Each raw material powder of uO was prepared as Sm: Ba: Cu = 1.6: 2.
3: After weighing to 3.3, BaCO₃And Cu
O alone at 880 ° C. for 30 hours to obtain BaCuO₂When
A calcined powder of CuO was obtained (by molar ratio, BaCuO ₂: CuO
= 2.3: 1.0). Next, weigh this calcined powder in advance
Sm that we put ₂O₃And Pt powder (average particle size 0.01μ)
m) and Ag₂O powder (average particle size of 13.8 μm)
Pt content 0.42wt%, Ag content 15wt%
And mix at 900 ° C in air for 10 hours
Firing for a while. This calcined powder is pulverized with a raikai machine,
The particle size was about 2 μm.

The composition of the calcined powder obtained was analyzed, and the results were as shown in FIG. When the obtained calcined powder was analyzed by powder X-ray diffraction, it was found that Sm _{1 + p} B
a _{2+ q} (Cu _1-b Ag _b ) ₃ O _7-x phase and Sm
_{2 + r} Ba _{1 + s} (Cu _1-d Ag _d ) O _5-r phase was confirmed. Here, Tm is 1060-40 = 1020 ° C., calculated from FIG. 1 and FIG.

[0029] The synthetic powder thus produced was prepared with an outer diameter of 8
0 mm, an inner diameter of 30 mm and a thickness of 26 mm were press-molded into a cylinder to produce a precursor 1 and an outer diameter of 80 mm.
Precursor 2 was prepared by press-forming into a disk having a thickness of 10 mm, and precursor 2 was laminated on precursor 1 (see FIGS. 4 and 5). Next, as shown in FIGS. 4 and 5,
A cylindrical alumina pipe 4 having an outer diameter of 17 mm, an inner diameter of 13 mm, and a height of 20 mm was placed on the alumina substrate 3 and Sm _{1 . 6} Ba
A plurality of pellet pieces 5 having a composition of _2.3 Cu _3.3 O _{x and} a thickness of about 2 mm were laid. Next, the precursor 1 and the precursor 2 were placed thereon so that the precursor 1 surrounds the alumina pipe 4, and the precursor 1 and the precursor 2 were placed in a two-zone furnace, and the following steps were performed.

First, the temperature is raised from room temperature to 1100 ° C. in 50 hours, and the temperature is maintained at this temperature for 20 minutes to be in a semi-molten state. A temperature gradient of 10 ° C./cm was added above and below the temperature of 2 ° C. until the temperature at the top of the precursor 2 reached 1025 ° C.
/ Min. Next, an Sm of 2 mm in length and 1 mm in thickness, not containing Ag, prepared in advance by a melting method.
_1.8 Ba _2.4 Cu _3. A seed crystal having a composition of ₄ O _x is brought into contact with the center of the upper part of the precursor 2 so that the growth direction is parallel to the c-axis, and 1015 ° C. to 1015 ° C. at a rate of 1 ° C./hr.
The temperature was lowered to ° C. After holding at this temperature for 80 hours, 9
The mixture was gradually cooled to 45 ° C. over 70 hours, and then the lower part of the precursor 1 was cooled to 945 ° C. in 20 hours so that the upper and lower temperature gradients became 0 ° C./cm.
Crystallization was performed by slow cooling over 00 hours.

The material thus crystallized was placed in another gas-replaceable furnace and annealed as follows. First, the inside of the furnace was evacuated to 0.1 Torr by a rotary pump, and then oxygen gas was poured into the furnace to make the atmosphere at an atmospheric pressure where the oxygen partial pressure was 99% or more. Thereafter, while flowing oxygen gas into the furnace at a flow rate of 0.5 L / min, the temperature was raised from room temperature to 450 ° C. for 10 hours, and 45 ° C.
Cool slowly from 0 ° C to 250 ° C over 200 hours.
The temperature was lowered from ° C. to room temperature in 10 hours. Thereafter, the same annealing treatment was performed once again.

After this annealing treatment, the precursor 1 is baked.
Outer diameter 67mm, inner diameter 26mm, thickness 22m due to shrinkage
m, and the precursor 2 has an outer diameter of 67 mm and a thickness of 8 mm.
I was Cut this precursor 1 near the center in the vertical direction
When the cross section was observed with EPMA,_{1 + p}Ba
_{2 + q}(Cu_1-bAg_b)₃O_7-x0.1 ~
Sm of about 30μm_{2 + r}Ba_{1 + s}(Cu_1-dAg
_d) O_5-yThe phases were finely dispersed. Where p,
q, r, s, and y are values of -0.2 to 0.2, respectively.
X was a value of -0.2 to 0.6. B, d
Is a value of 0.0 to 0.05, and is 0.008 on average.
It was about. No Ag near the center of this material
Select a part and take it at 1000x magnification using a polarizing microscope
The image was analyzed from this photograph in the area of 70 × 90 μm.
Where Sm_{2 + r}Ba_{1 + s}(Cu _1-dAg_d)
O_5-yThe average particle size of the phase is 1.5 μm and the total area
Was about 25%. In addition, the entire sample
Ag of about 0.1-100 μm is finely dispersed
I was Also, use a polarizing microscope near the center of this material.
And photographed at a magnification of 50 ×, and from this photograph, 1.4 × 1.8m
When the range of m was analyzed by image, the average particle size of this Ag was
27 μm, occupying the entire area of the part excluding the holes
Was 17%. Further, the particle size is 5 to 200 μm.
Vacancies are dispersed by 6% of the total area
Was. Further, the precursor 1 and the precursor 2 are fused and the seed crystal is
The axial direction of the cylindrical and disc-shaped material is
The whole material is uniformly oriented as if it were a row, adjacent crystals
The misorientation between the directions is 3 ° or less, and is substantially a single crystal.
A superconducting material was obtained.

Next, the precursor 2 and the lower portion 2 mm were separated from the precursor 1 by slicing to obtain an outer diameter 6 mm.
The cylindrical shape was 7 mm, the inner diameter was 26 mm, and the thickness was 20 mm.
After cooling from room temperature to a temperature of 77 K while applying an external magnetic field of 2.1 T (tesla) in the axial direction of the cylindrical superconductor, the magnetic field was removed and the magnetic flux density captured in the superconductor was measured. This measurement was carried out by mounting the Hall element on an XY stage and moving it along the superconductor surface at a distance of about 1 mm from the superconductor surface, and measuring the axial magnetic flux density distribution of the material. As a result, since there was no crystal grain boundary in the entire ring, as shown in FIGS.
A trapped magnetic flux density of T was obtained.

Next, 2.5 × 2.
A sample of 5 × 2 mm was cut out, and the magnetic susceptibility was measured with a vibrating sample magnetometer. From the obtained susceptibility curve, Bean
Applying the model, the critical current density J at 77K
When c was estimated, it showed a high critical current density as shown in FIG.

[Example 2] Gd₂O₃, BaCO₃, C
Each raw material powder of uO is Gd: Ba: Cu = 1.8: 2.
4: After weighing to 3.4, BaCO₃And Cu
O alone at 880 ° C. for 30 hours to obtain BaCuO₂When
A calcined powder of CuO was obtained (by molar ratio, BaCuO ₂: CuO
= 2.4: 1.0). Next, weigh this calcined powder in advance
Gd ₂O₃And Pt powder (average particle size 0.01μ)
m) and Ag₂O powder (average particle size 13.8 μm)
t content 0.42wt%, Ag content 10wt%
Add and mix as needed, and in air at 900 ° C for 10 hours
Fired. This calcined powder is pulverized with a raikai machine,
The diameter was about 2 μm.

Analysis of the composition of the calcined powder obtained showed values as shown in FIG. When the obtained calcined powder was analyzed by powder X-ray diffraction, Gd _{1 + p} B
a _{2+ q} (Cu _1-b Ag _b ) ₃ O _7-x phase and Gd
_{2 + r} Ba _{1 + s} (Cu _1-d Ag _d ) O _5-r phase was confirmed. Here, Tm is 1030-40 = 990 ° C., calculated from FIG. 1 and FIG.

The synthetic powder produced in this manner was applied to an outer diameter of 8
0 mm, an inner diameter of 44 mm and a thickness of 26 mm were press-molded into a cylinder to produce the precursor 1 and an outer diameter of 80 mm.
Precursor 2 was prepared by press-forming into a disk having a thickness of 10 mm, and precursor 2 was laminated on precursor 1 (see FIGS. 4 and 5). Next, as shown in FIGS. 4 and 5, an outer diameter of 30 mm and an inner diameter of 24 m
An alumina pipe 4 having a height of 20 mm and a height of 20 mm is placed, and Gd _1.8 Ba prepared in advance by a melting method.
A plurality of pellet pieces 5 each having a thickness of about 2 mm having a composition of _2.4 Cu _3.4 O _x were laid, and the precursor 1 was placed thereon in the same manner as in Example 1.
The precursor 2 was placed and placed in a two-zone furnace, and the following steps were performed.

First, the temperature is raised from room temperature to 1100 ° C. in 50 hours, and the temperature is maintained at this temperature for 20 minutes to be in a semi-molten state. A temperature gradient of 10 ° C./cm was applied above and below the temperature of the precursor 2 until the temperature at the top of the precursor 2 reached 995 ° C.
The temperature was lowered in min. Next, Ag-free Gd _1.8 Ba _2.4 Cu _3.4 O prepared in advance by a melting method.
A seed crystal having an _x composition was brought into contact with the upper part of the precursor 2 so that the growth direction was parallel to the c-axis, and the temperature was lowered from 995 ° C. to 985 ° C. at a rate of 1 ° C./hr. After maintaining at this temperature for 100 hours, the temperature was gradually cooled to 915 ° C. over 70 hours, and then the precursor 1 was heated so that the upper and lower temperature gradients became 0 ° C./cm.
Was cooled to 915 ° C. in 20 hours, and then slowly cooled to room temperature over 100 hours to perform crystallization.

The thus crystallized material was placed in another gas-replaceable furnace and annealed as follows. First, the inside of the furnace was evacuated to 0.1 Torr by a rotary pump, and then oxygen gas was poured into the furnace to make the atmosphere at an atmospheric pressure where the oxygen partial pressure was 99% or more. Thereafter, while flowing oxygen gas into the furnace at a flow rate of 0.5 L / min, the temperature was raised from room temperature to 450 ° C. for 10 hours, and 45 ° C.
Cool slowly from 0 ° C to 250 ° C over 200 hours.
The temperature was lowered from ° C. to room temperature in 10 hours. Thereafter, the same annealing treatment was performed once again.

After this annealing treatment, the precursor 1 is baked.
Outer diameter 67mm, inner diameter 37mm, thickness 22m for shrinkage
m, and the precursor 2 has an outer diameter of 67 mm and a thickness of 8 mm.
I was Cut this precursor 1 near the center in the vertical direction
When the cross section was observed by EPMA, Gd_{1 + p}Ba
_{2 + q}(Cu_1-bAg_b)₃O_7-x0.1 ~
Gd of about 30 μm_{2 + r}Ba_{1 + s}(Cu_1-dAg
_d) O_5-yThe phases were finely dispersed. Where p,
q, r, s, and y are values of -0.2 to 0.2, respectively.
X was a value of -0.2 to 0.6. B, d
Is a value of 0.0 to 0.05, and is 0.008 on average.
It was about. No Ag near the center of this material
Select a part and take it at 1000x magnification using a polarizing microscope
The image was analyzed from this photograph in the area of 70 × 90 μm.
Gd_{2 + r}Ba_{1 + s}(Cu _1-dAg_d)
O_5-yThe average particle size of the phase is 1.0 μm and the total area
Was about 30%. In addition, the entire sample
Ag of about 0.1-100 μm is finely dispersed
I was Also, use a polarizing microscope near the center of this material.
And photographed at a magnification of 50 ×, and from this photograph, 1.4 × 1.8m
When the range of m was analyzed by image, the average particle size of this Ag was
24 μm, occupying the entire area of the area excluding holes
Was 7%. Further, the particle size is about 5 to 200 μm.
Vacancies are dispersed at 7% of the total area.
Was. In addition, the precursor 1 and the precursor 2 are fused and the seed crystal is reflected.
The axial direction of the cylindrical and disk-shaped material is parallel to the c-axis
So that the whole material is uniformly oriented and between adjacent crystals
Is less than 3 ° and is substantially a single crystal
A conductive material was obtained.

Next, the precursor 2 and the lower side 2 mm from the part of the precursor 1 were cut off by slicing to obtain an outer diameter 6 mm.
The cylindrical shape was 7 mm, the inner diameter was 37 mm, and the thickness was 20 mm.
After cooling from room temperature to a temperature of 77 K while applying an external magnetic field of 2.1 T in the axial direction of the cylindrical superconductor, the magnetic field was removed and the magnetic flux density captured in the superconductor was measured in the same manner as in Example 1. As a result, since there was no crystal grain boundary in the whole ring, as shown in FIG. 10, a trapped magnetic flux density of about 1.0 T was obtained almost uniformly on the inner diameter φ37 mm of the ring.

Next, when the critical current density Jc at a temperature of 77 K was estimated in the same manner as in Example 1, a high critical current density was obtained as shown in FIG.

Example 3 Each raw material powder of RE ₂ O ₃ (RE is Sm 50%, Gd 50% in molar ratio), BaCO ₃ , and CuO was prepared as RE: Ba: Cu = 1.6: 2.3: 3. 3 and weighed only 88 BaCO ₃ and CuO.
By calcining at 0 ° C. for 30 hours, a calcined powder of BaCuO ₂ and CuO was obtained (BaCuO ₂ : CuO = 2.3 by molar ratio:
1.0). Next, the calcined powder was added to R
E ₂ O ₃ and 0.45 wt% of Pt powder were added, and Ag ₂ O powder was added and mixed so that the amount of Ag element became 10 wt%, followed by firing at 900 ° C. in the atmosphere for 10 hours. The obtained calcined powder was pulverized with a raikai machine to have an average particle size of about 2 μm.

Analysis of the composition of the obtained calcined powder showed values as shown in FIG. When the obtained calcined powder was analyzed by powder X-ray diffraction, RE _{1 + p
Ba 2 + q (Cu 1-} b Ag b) 3 O 7-x phase and R
E _{2 + r} Ba _{1 + s} (Cu _{1- d} Ag _d ) O _5-r phase was confirmed. Here, Tm is calculated from FIG. 1 and FIG. 2 to be (1060 × １ ／ + 1030 × １ ／) − 40.
= 1005 ° C.

The synthetic powder produced in this manner was prepared by adding an outer diameter of 5
3 mm, an inner diameter of 16 mm and a thickness of 26 mm were press-molded into a cylinder to produce a precursor 1 and an outer diameter of 53 mm.
Precursor 2 was prepared by press-forming into a disk having a thickness of 7 mm, and precursor 2 was laminated on precursor 1 in the same manner as in Example 1. Next, a plurality of pellet pieces 5 having a thickness of about 2 mm and having a composition of Sm _1.6 Ba _2.3 Cu _3.3 O _x prepared in advance by a melting method are laid on the alumina substrate 3, Then, the precursor 1 and the precursor 2 were placed in the same manner as in Example 1 except that the alumina pipe 4 was not used, and the precursor 1 and the precursor 2 were placed in a two-zone furnace, and the following steps were performed.

First, the temperature is raised from room temperature to 1100 ° C. in 50 hours, and the temperature is maintained at this temperature for 20 minutes to be in a semi-molten state. A temperature gradient of 10 ° C./cm was applied above and below the temperature of the precursor 2 until the temperature at the top of the precursor 2 reached 1010 ° C.
/ Min. Next, Ag-free Sm _1.8 Ba _2.4 Cu _3.4 prepared in advance by a melting method.
A seed crystal having an O _x composition is brought into contact with the upper part of the precursor 2 so that the growth direction is parallel to the c-axis, and 1010 ° C. to 1 ° C./h
The temperature was lowered to 1000 ° C. at a rate of r. 90 at this temperature
After holding for a while, slowly cool down to 930 ° C over 70 hours,
Thereafter, the lower part of the precursor was cooled to 930 ° C. in 20 hours so that the upper and lower temperature gradients became 0 ° C./cm, and then gradually cooled to room temperature over 100 hours to perform crystallization.

The material thus crystallized was placed in another gas-replaceable furnace and annealed as follows. First, the inside of the furnace was evacuated to 0.1 Torr by a rotary pump, and then oxygen gas was poured into the furnace to make the atmosphere at an atmospheric pressure where the oxygen partial pressure was 99% or more. Thereafter, while flowing oxygen gas into the furnace at a flow rate of 0.5 L / min, the temperature was raised from room temperature to 450 ° C. for 10 hours, and 45 ° C.
Cool slowly from 0 ° C to 250 ° C over 200 hours.
The temperature was lowered from ° C. to room temperature in 10 hours. Thereafter, the same annealing treatment was performed once again.

After this annealing treatment, the precursor 1 is baked.
For shrinkage, outer diameter 45mm, inner diameter 14mm, thickness 22m
m, and the precursor 2 has an outer diameter of 45 mm and a thickness of 6 mm.
I was Cut this precursor 1 near the center in the vertical direction
When the cross section was observed with EPMA,_{1 + p}Ba
_{2 + q}(Cu_1-bAg_b)₃O_7-x0.1 ~
RE of about 30μm_{2 + r}Ba_{1 + s}(Cu_1-dAg
_d) O_5-yThe phases were finely dispersed. Where p,
q, r, s, and y are values of -0.2 to 0.2, respectively.
X was a value of -0.2 to 0.6. B, d
Is a value of 0.0 to 0.05, and is 0.008 on average.
It was about. No Ag near the center of this material
Select a part and take it at 1000x magnification using a polarizing microscope
The image was analyzed from this photograph in the area of 70 × 90 μm.
After that, RE_{2 + r}Ba_{1 + s}(Cu _1-dAg_d)
O_5-yThe average particle size of the phase is 1.1 μm and the total area
Was about 24%. In addition, the entire sample
Ag of about 0.1-100 μm is finely dispersed
I was Also, use a polarizing microscope near the center of this material.
And photographed at a magnification of 50 ×, and from this photograph, 1.4 × 1.8m
When the range of m was analyzed by image, the average particle size of this Ag was
49 μm, occupying the entire area of the part excluding the holes
Was 19%. Further, the particle size is 5 to 200 μm.
About 5% of pores are dispersed in the whole area
Was. Further, the precursor 1 and the precursor 2 are fused and the seed crystal is
The axial direction of the cylindrical and disc-shaped material is
The whole material is oriented as if it were a row, with the direction between adjacent crystals
Substrate displacement of 3 ° or less and superconductivity of substantially single crystal
The material was obtained.

Next, the precursor 2 and the lower side 2 mm were separated from the precursor 1 portion by slicing to obtain an outer diameter 4 mm.
It was formed into a cylindrical shape having a diameter of 5 mm, an inner diameter of 14 mm, and a thickness of 20 mm.
After cooling from room temperature to a temperature of 77 K while applying an external magnetic field of 2.1 T in the axial direction of the cylindrical superconductor, the magnetic field was removed and the magnetic flux density captured in the superconductor was measured.
This measurement was carried out by mounting the Hall element on an XY stage and moving it along the superconductor surface at a distance of about 1 mm from the superconductor surface, and measuring the axial magnetic flux density distribution of the material. As a result, since there was no grain boundary in the entire ring, as shown in FIG. 13, a trapped magnetic flux density of about 1.3 T was obtained almost uniformly on the inner diameter of the ring of φ14 mm.

Next, 2.5.times.2.
A sample of 5 × 2 mm was cut out, and the magnetic susceptibility was measured with a vibrating sample magnetometer. From the obtained susceptibility curve, Bean
Applying the model, the critical current density J at 77K
When c was estimated, a high critical current density was shown as shown in FIG.

Example 4 A synthetic powder produced in the same manner as in Example 1 was formed by forming a disc having an outer diameter of 53 mm and a thickness of 33 mm on one surface of a disk with a recess having an inner diameter of 16 mm and a depth of 23 mm. The precursor was formed by press molding into a shape. Next, Sm _1.6 prepared in advance by a melting method.
Laying a Ba _2.3 Cu _3.3 O _x plurality of pellets pieces having a thickness of about 2mm composition on an alumina substrate, the recess of the precursor is placed so that the lower thereon, 2 Zoned And the following steps were performed.

First, the temperature is raised from room temperature to 1100 ° C. in 50 hours, and maintained at this temperature for 20 minutes to obtain a semi-molten state, and then 10 ° C. above and below the precursor so that the upper part of the precursor is on the low temperature side. The temperature was lowered at 1 ° C./min until the temperature at the top of the precursor reached 1025 ° C. by applying a temperature gradient of / cm.
Next, Sm _1.8 Ba _2.4 Cu of 2 mm in length and width and 1 mm in thickness, not containing Ag, prepared in advance by a melting method.
A seed crystal of _3.4 O _x composition was brought into contact with the center of the upper part of the precursor so that the growth direction became parallel to the c-axis, and the temperature was lowered from 1025 ° C. to 1015 ° C. at a rate of 1 ° C./hr. After maintaining at this temperature for 70 hours, the temperature is gradually cooled to 945 ° C. over 70 hours, and then the lower part of the precursor is cooled to 945 ° C. in 20 hours so that the upper and lower temperature gradients become 0 ° C./cm. Thereafter, the resultant was gradually cooled to room temperature over 100 hours to perform crystallization.

The material thus crystallized was subjected to the same annealing treatment as in Example 1.

After this annealing treatment, the precursor had an outer diameter of 45 mm, an inner diameter of the concave portion of 28 mm, and a thickness of 3 mm due to shrinkage.
It was 0 mm. The precursor was cut near the center in the vertical direction and near the end in the radial direction, and the cross section was observed by EPMA. As a result, a structure almost similar to that of Example 1 was obtained. In addition, the entire material is oriented so that the axial direction of the material is parallel to the c-axis reflecting the seed crystal, and the misorientation of the orientation between adjacent crystals is 3 ° or less. The material was obtained.

Next, 8 mm of the upper side and 2 mm of the lower side were cut from this precursor to obtain an outer diameter of 45 mm and an inner diameter of 28 m.
m, a cylindrical shape having a thickness of 20 mm. After cooling from room temperature to a temperature of 77 K while applying an external magnetic field of 2.1 T in the axial direction of the cylindrical superconductor, the magnetic field was removed and the magnetic flux density captured in the superconductor was measured in the same manner as in Example 1. As a result, microcracks were partially present at the ends, but no crystal grain boundaries were present in the entire ring. As shown in FIG. 16, approximately 0.35 T was trapped almost uniformly on the inner diameter φ28 mm of the ring. Magnetic flux density was obtained.

When the critical current density Jc was measured in the same manner as in Example 1, a value substantially equal to that in Example 1 was obtained.

[Comparative Example] A synthetic powder produced in the same manner as in Example 1 was prepared by mixing an outer diameter of 80 mm, an inner diameter of 30 mm, and a thickness of 2 mm.
Precursor 1 was prepared by press molding into a 6 mm cylindrical shape.
Next, as shown in FIG. 16, on the alumina substrate 3, Sm _1.6 Ba _2.3 Cu prepared in advance by a melting method.
_3.3 laying a plurality of pellets pieces 5 having a thickness of about 2mm of O _x, by placing the precursor 1 thereon, was subjected to the following steps be installed in the furnace body 2 Zoned.

First, the temperature is raised from room temperature to 1100 ° C. in 50 hours, and maintained at this temperature for 20 minutes to make a semi-molten state. By applying a temperature gradient of 10 ° C./cm, the temperature of the precursor 1 was lowered at a rate of 1 ° C./min until the temperature at the upper portion became 1025 ° C. Then, Sm _1.8 Ba _2.4 C of 2 mm in length and width and 1 mm in thickness, not containing Ag, prepared in advance by a melting method.
The seed crystal 6 having a composition of u _3.4 O _x is brought into contact with a part of the upper portion of the precursor 1 as shown in FIG. 16 so that the growth direction is parallel to the c-axis, and 1025 ° C. to 1 ° C./hr. 10 at the speed of
The temperature was lowered to 15 ° C. After maintaining at this temperature for 80 hours, the temperature is gradually cooled to 945 ° C. over 70 hours, and then the lower part of the precursor 1 is heated to 945 ° C. in 20 hours so that the upper and lower temperature gradients become 0 ° C./cm. After cooling, the resultant was gradually cooled to room temperature over 100 hours to perform crystallization.

The material crystallized in this manner was placed in another gas-replaceable furnace and annealed as follows. First, the inside of the furnace was evacuated to 0.1 Torr by a rotary pump, and then oxygen gas was poured into the furnace to make the atmosphere at an atmospheric pressure where the oxygen partial pressure was 99% or more. Thereafter, while flowing oxygen gas into the furnace at a flow rate of 0.5 L / min, the temperature was raised from room temperature to 450 ° C. for 10 hours, and 45 ° C.
Cool slowly from 0 ° C to 250 ° C over 200 hours.
The temperature was lowered from ° C. to room temperature in 10 hours. Thereafter, the same annealing treatment was performed once again.

After this annealing treatment, the precursor 1 has an outer diameter of 67 mm, an inner diameter of 26 mm, and a thickness of 22 m due to shrinkage.
m. This precursor 1 was cut near the center in the vertical direction and the cross section was observed by EPMA. As a result, a structure almost similar to that of Example 1 was obtained. However, the crystal in FIG.
As shown by the arrow A of 7, the seed material 6 grew along the ring, and the entire material was uniformly oriented such that the axial direction of the cylindrical material was parallel to the c-axis. However, in the portion 8 to which the terminal portion of the crystal growth is connected, there was precipitation of a liquid phase component mainly composed of the extra Ba element and Cu element extruded during the crystal growth.

Next, the upper portion of the precursor 1 was cut off by slicing to obtain an outer diameter of 67 mm, an inner diameter of 26 mm, and a thickness of 20 mm.
mm cylindrical shape. After cooling from room temperature to a temperature of 77 K while applying an external magnetic field of 2.1 T in the axial direction of the cylindrical superconductor, the magnetic field was removed and the magnetic flux density captured in the superconductor was measured in the same manner as in Example 1. As a result, the terminal end of the crystal growth became a crystal grain boundary, from which magnetic flux penetrated into the cavity, and as shown in FIGS. 18 and 19, the trapped magnetic flux density was as low as 0.3 T at the maximum.

Next, a sample was cut out from the vicinity of the grain boundary, and the critical current density Jc at a temperature of 77 K was estimated in the same manner as in Example 1. As shown in FIG. 20, the critical current density was low.

[0063]

As described in detail above, according to the present invention,
On top of the cylindrical precursor, a plate-shaped precursor having a size to cover the opening of the cylindrical precursor is laminated, and after heating and melting these precursors, the plate-shaped precursor is gradually cooled. By growing crystals from the body toward the cylindrical precursor, electrical properties,
A large hollow oxide superconductor having excellent magnetic properties and mechanical strength can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 shows R when each rare earth metal element is used as RE.
_{E 1 + p Ba 2 + q} (Cu 1- b Ag b) 3 O 7-x phase melting (crystallization temperature) diagram showing the Tm.

FIG. 2 shows the addition amount of Ag and RE _{1 + p} Ba _{2 + q} (Cu
Melting point (crystallization temperature) Tm of _1-b Ag _b ) ₃ O _7-x phase
FIG. 4 is a diagram showing a relationship between the correction value and the correction value.

FIG. 3 is a view showing the compositions of precursor 1 and precursor 2 produced in Example 1.

FIG. 4 is a perspective view showing a technique for laminating a precursor 1 and a precursor 2 of Example 1.

FIG. 5 is a cross-sectional view showing a method for laminating a precursor 1 and a precursor 2 of Example 1.

FIG. 6 is a view showing a result of measuring an in-plane distribution of a trapped magnetic flux density of the cylindrical oxide superconductor manufactured in Example 1.

FIG. 7 is a view showing a result of measuring a trapped magnetic flux density along a radial direction of the cylindrical oxide superconductor manufactured in Example 1.

FIG. 8 is a diagram showing the magnetic field dependence of the critical current density of the cylindrical oxide superconductor manufactured in Example 1.

FIG. 9 is a view showing the compositions of precursor 1 and precursor 2 produced in Example 2.

FIG. 10 is a view showing a result of measuring a trapped magnetic flux density along a radial direction of a cylindrical oxide superconductor manufactured in Example 2.

FIG. 11 is a diagram showing the magnetic field dependence of the critical current density of the cylindrical oxide superconductor manufactured in Example 2.

FIG. 12 shows precursor 1 and precursor 2 produced in Example 3.
FIG.

FIG. 13 is a view showing a result of measuring a trapped magnetic flux density along a radial direction of the cylindrical oxide superconductor manufactured in Example 3.

FIG. 14 is a diagram showing the magnetic field dependence of the critical current density of the cylindrical oxide superconductor manufactured in Example 3.

FIG. 15 is a view showing a result of measuring a trapped magnetic flux density along a radial direction of the cylindrical oxide superconductor manufactured in Example 4.

FIG. 16 is a perspective view showing a method for mounting a precursor of a comparative example.

FIG. 17 is a view showing a structure of a material of a comparative example after crystal growth.

FIG. 18 is a view showing a result of measuring an in-plane distribution of a trapped magnetic flux density of a cylindrical oxide superconductor manufactured in a comparative example.

FIG. 19 is a view showing a result of measuring a trapped magnetic flux density along a radial direction of a cylindrical oxide superconductor manufactured in a comparative example.

FIG. 20 is a diagram showing the magnetic field dependence of the critical current density of a cylindrical oxide superconductor manufactured in a comparative example.

[Explanation of symbols]

 Reference Signs List 1, 2 Precursor 3 Alumina substrate 4 Alumina pipe 5 Pellet piece 6 Seed crystal 7 Crystal growth facet 8 Crystal growth termination

 ────────────────────────────────────────────────── ─── Continued from the front page (72) Inventor Shigeo Nagaya 20 Kitakanyama, Odaka-cho, Midori-ku, Nagoya-shi, Aichi F-term in Chubu Electric Power Co., Inc. Electric Power Research Laboratory 4G047 JA10 JC02 JC03 KBC20

Claims (14)

[Claims] 1. RE _{1 + p} Ba _{2 + q} (Cu _1-b Ag
_b ) ₃ O _7-x (RE is one or more rare earth metal elements, −0.2 ≦ p ≦ 0.2, −0.2 ≦ q ≦ 0.
2, 0 ≦ b ≦ 0.05, −0.2 ≦ x ≦ 0.6) In the phase, RE _{2 + r} Ba _{1 + s} (Cu _1-d Ag _d ) O
_5-y phase and RE _{4 + r} Ba _{2 + s} (Cu _1-d A
g _d ) ₂ O _10-y phase (−0.2 ≦ r ≦ 0.2, −
0.2 ≦ s ≦ 0.2, 0 ≦ d ≦ 0.05, -0.2 ≦ y
≦ 0.2) at least one phase is finely dispersed, and the tubular oxide superconductor contains the same element as RE of the tubular oxide superconductor. A hollow oxide superconductor characterized by being laminated and integrally crystallized with a plate-shaped oxide superconductor that closes the opening. 2. The hollow oxide superconductor according to claim 1, wherein the composition of the plate-shaped oxide superconductor is the same as the composition of the cylindrical oxide superconductor. 3. The method according to claim 1, wherein the RE contains at least 50% of one or more elements selected from Nd, Sm, Gd and Dy.
The hollow oxide superconductor according to claim 1, wherein the oxide superconductor includes the above. 4. The method according to claim 1, wherein said hollow oxide superconductor comprises 8 wt%.
The hollow oxide superconductor according to claim 1, wherein the hollow oxide superconductor contains Ag in an amount of from about 60 wt% to about 60 wt%. 5. The method according to claim 1, wherein the hollow oxide superconductor comprises Pt, Pt,
d, Ru, Rh, Ir, Os, Re, Ce and at least one compound selected from the compounds of these metals are added at 0.05
5 to 5 wt% (in the case of a compound, indicated by the element weight of only the metal).
The hollow oxide superconductor according to any one of the above. 6. A raw material mixture containing an RE compound (RE is one or more rare earth metal elements containing Y), a Ba compound and a Cu compound at a temperature higher than the melting point of the raw material mixture. After that, in a method of producing a RE-Ba-Cu-O-based hollow oxide superconductor by gradually cooling and growing crystals, while producing a cylindrical precursor from the raw material mixture, R of the cylindrical precursor
A plate-shaped precursor containing the same element as E and having a size to close the opening of the cylindrical precursor is produced, and the plate-shaped precursor is laminated on the cylindrical precursor, A method for producing a hollow oxide superconductor, characterized in that after heating and melting these precursors, they are gradually cooled to grow crystals from the plate-like precursor toward the cylindrical precursor. 7. The method for producing a hollow oxide superconductor according to claim 6, wherein the composition of the plate-like precursor is the same as the composition of the tubular precursor. 8. The plate-shaped precursor has a surface having the same size and the same shape as a surface on which an opening of the cylindrical precursor is opened. 3. The method for producing a hollow oxide superconductor according to item 1. 9. The method according to claim 1, wherein the heating and melting temperature is the same as the cylindrical shape.
And the plate-like precursor is RE_{2 + r}Ba_{1 + s}(Cu_1-d
Ag_d) O_5-yPhase and RE_{4 + r}Ba _{2 + s}(C
u_1-dAg_d )₂O_10-yPhase (-0.2 ≦ r ≦
0.2, -0.2≤s≤0.2, 0≤d≤0.05,-
0.2 ≦ y ≦ 0.2)
9. The method according to claim 6, wherein the temperature is
A method for producing a hollow oxide superconductor according to any of the above. 10. After the heating and melting step, a temperature gradient of 1 to 30 ° C./cm is applied above and below the plate-like and tubular precursors so that the upper part of the plate-like precursor is on the low temperature side. The method for producing a hollow oxide superconductor according to any one of claims 6 to 9, wherein the plate-like and cylindrical precursors are gradually cooled to grow crystals. 11. The method according to claim 6, wherein a seed crystal is provided after the heating and melting step, and thereafter, the plate-like and cylindrical precursors are gradually cooled to grow crystals. The method for producing a hollow oxide superconductor according to any one of the above. 12. After the heating and melting step, a temperature gradient of 1 to 30 ° C./cm is applied above and below the plate-like and tubular precursors so that the upper part of the plate-like precursor is on the low temperature side. After that, a seed crystal is provided, and thereafter, the plate-like and tubular precursors are gradually cooled to grow crystals.
A method for producing a hollow oxide superconductor according to any one of claims 6 to 9. 13. The plate-like precursor has a thickness of 5 to 20.
The method for producing a hollow oxide superconductor according to any one of claims 6 to 12, wherein the diameter is 0.1 mm. 14. A raw material mixture containing an RE compound (RE is one or more rare earth metal elements containing Y), a Ba compound and a Cu compound, is heated and melted at a temperature higher than the melting point of the raw material mixture. And then gradually cooling the crystal to grow the crystal, thereby producing a RE-Ba-Cu-O-based hollow oxide superconductor, producing a precursor having a concave portion on one surface from the raw material mixture. Then, after heating and melting this precursor, a seed crystal is placed on the surface opposite to the concave portion, and then the precursor is gradually cooled to grow a crystal, and then the seed crystal is placed. Or a method for producing a hollow oxide superconductor.