JPH06271317A - Rare-earth based superconductive material and production thereof - Google Patents

Abstract

PURPOSE:To finely disperse 211 phase particles acting as the pin centers in the crystal grains consisting of 123 phase without using any expensive metal by sintering, slowly cooling, heat-treating in a nonoxidizing atmosphere and then heat-treating in an oxidizing atmosphere, moldings contg. a rare earth element (RE), Ba, Cu, O and Ca under specified conditions. CONSTITUTION:The temp. of the moldings contg. RE, Ba, Cu, O and Ca is maintained at a temp. higher than that, at which the compound represented by the formula I decomposablly melts into the compound represented by the formula II and a liquid phase, and lower than that, at which the compound of the formula II decomposablly melts, so that the moldings are brought into a sintered state. The Ca content of the moldings is 2 to 15mol per mol of RE. In the formula I, RE is Re; X is from 0 to 1. The objective superconductive material is produced by (1) sintering as described above, (2) slowly cooling the resulting sintered compact to grow the crystal grains consisting of the compound of formula I and to disperse the particles consisting of the compound of formula II in the inside of the crystal grains, (3) nonoxidizingly heat-treating the slowly cooled sintered compact in a nonoxidizing atmosphere and further (4) oxidizingly heat-treating the resulting heat-treated sintered compact at a temp. lower than the above slow-cooling temp. in an oxidizing atmosphere.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of a rare earth-based superconducting material and a method for producing the same, and more specifically, so-called 211 phase particles that act as pin centers are referred to as "1".
The present invention relates to a rare earth-based superconducting material finely dispersed in a matrix of 23 phases and a method for producing the same. The bulk rare earth-based superconducting material according to the present invention can be used for flywheels, magnetic shields, and the like.

[0002]

2. Description of the Related Art The Meissner effect of superconductors exhibiting complete diamagnetism has been known for a long time, but oxide superconductors are superior to alloys such as Nb-Ti and intermetallic compounds such as Nb ₃ Sn. It turned out that the critical temperature was much higher, and it is suddenly drawing attention. There is a purpose that the superconductor can be applied to a magnetic field shielding material or a magnetic levitation material by utilizing this Meissner effect. Naturally, a large superconducting current value is desired for practical use. Therefore, active research is being conducted to improve the critical magnetic field and the critical current density of oxide superconductors.

In the case of perfect diamagnetism, magnetic flux lines cannot enter the inside of the superconductor, but the second-class superconductor has an electric resistance until the upper critical magnetic field is reached even if the magnetic flux starts to enter in the lower critical magnetic field. It has the property that it does not occur. Therefore, if there are a large number of so-called pin centers that can prevent the movement of magnetic flux lines due to Lorentz force even if the magnetic flux begins to penetrate into the superconductor in a magnetic field above the lower critical magnetic field, the superconducting current value should be improved. You can For example, it is known that lattice defects act as pin centers.

However, recently, attempts are being made to improve the superconducting current density by intentionally dispersing fine particles acting as pin centers in the oxide superconductor.
For example, Ogawa, Yoshida, Hirabayashi ISEC journal
Vol. 4 No. 3 1991: p30, in a rare earth oxide superconductor, platinum powder was mixed with a calcined powder as a raw material, heated to 1100 ° C., and Y ₂ BaCuO _{5 was} added.
A platinum addition method, which is a melting method, has been announced in which a solid phase (hereinafter, appropriately referred to as "211 phase") and a liquid phase coexist in a partially molten state and then gradually cooled. Then,
Fine particles of Y ₂ BaCuO ₅ are dispersed in the crystal grains of YBa ₂ Cu ₃ O _7-x (hereinafter, appropriately referred to as “123 phase”), and these fine particles act as pin centers to form oxide superconductors. It has been reported to show a high critical current density (Jc) even in a magnetic field.

Similarly, Applicants have added RE ₂ B by adding a trace amount of platinum or rhodium or any metal compound.
aCuO ₅ (RE is Y, Gd, Dy, Ho, Er and Yb
A rare earth-based oxide superconductor in which fine particles of ( ₁ ) are finely dispersed in a matrix made of REBa ₂ Cu ₃ O _7-x and a method for producing the same (Japanese Patent Application No. 412529). RE ₂ BaCuO
Fine particles of ₅ act with the pin center. Also, Y: Ba: Cu =
After adding 0.5% by weight of platinum to a calcined powder having a composition of 1.5: 2.25: 3.25, heating to 1100 ° C. and holding at that temperature for 1 hour, 1000 ° C. to 940 ° C. It has been reported that by slowly cooling at 1 ° C per hour until that time, a fine structure in which fine particles of Y ₂ BaCuO ₅ are finely dispersed in crystal grains of YBa ₂ Cu ₃ O _7-x can be obtained (Physica C 1
77 (1991) 101). It has also been reported that the superconductor thus obtained has an improved critical current density at a temperature of 77K and a magnetic flux density of 1T.

[0006]

However, obtaining a rare earth-based superconducting material in which the 211 phase is finely dispersed in the 123 phase of the matrix by the melting method to which platinum or rhodium is added is, at any rate, in the laboratory level. At the industrial level of production, expensive precious metals are used, which is not preferable in terms of cost. Therefore, it is an object of the present invention to finely disperse the 211-phase particles that act as pin centers in the crystal grains of the 123 phase without using such an expensive noble metal.

[0007]

According to the present invention, a crystal grain composed of (RECa) Ba ₂ Cu ₃ O _7-x constituting a matrix,
Having a large number of particles (RECa) ₂ BaCuO ₅ dispersed inside the crystal grains, the RE is a rare earth element,
The x is 0 or more and 1 or less, and 98% or more of the particles are rare earth superconducting materials having a particle size of 20 μm or less, and the Ca element contained in the rare earth superconducting material is the rare earth superconducting material. 2 of RE elements contained in superconducting materials
There is provided a rare earth-based superconducting material characterized by being ˜15 mol%. In the present invention, 90% of the above particles
The above preferably has a particle size of 5 μm or less. Further, in the present invention, the Ca element contained in the rare earth-based superconducting material is preferably 5 to 12 mol% of the RE element contained in the rare earth-based superconducting material.
In the present invention, the critical current density of the rare earth-based superconducting material at 77 K and magnetic flux density of 0.5 Tesla is preferably 9000 amperes / cm ² or more. Further, in the present invention, the rare earth element is Y, S
It is preferable to be composed of at least one element selected from the group consisting of m, Eu, Dy, Ho, Er and Yb. Furthermore, in the present invention, it is preferable that the rare earth element contains Y.

According to the present invention, (1) at least R
A molded body containing E, Ba, Cu, O and Ca elements was (RECa) Ba ₂ Cu
A is ₃ O _7-x is (RECa) ₂ BaCuO ₅ and liquid phases and the resolution melting temperature or higher, and the (RECa) ₂ BaCuO ₅ is kept below the temperature at which decomposition melted, thereby, the molded body Is calcined to a semi-molten state, the Ca element is contained in the molded body in an amount of 2 to 15 mol% of the RE element, and the RE is a rare earth element,
The x is 0 or more and 1 or less, and (2) the fired body is gradually cooled, whereby crystal grains composed of (RECa) Ba ₂ Cu ₃ O _7-x are grown, and inside the crystal grains. Particles of (RECa) ₂ BaCuO ₅ are dispersed in (3) in a non-oxidizing atmosphere,
A method for producing a rare earth-based superconducting material, which comprises subjecting the fired body to a non-oxidative heat treatment, and then (4) oxidizing the fired body in an oxidizing atmosphere at a temperature lower than the annealing temperature. To be done. In the present invention, it is preferable to hold the fired body at 500 ° C. or higher and 900 ° C. or lower in the non-oxidation heat treatment step. Further, in the present invention, in the holding step (1), the molded body is treated with 1050 to 120
The temperature is maintained at 0 ° C. for 0.2 to 5 hours, and in the slow cooling step (2), the calcined body is heated to a temperature of 1050 to 950 ° C.
It is preferable to gradually cool at 80 ° C. or more at a cooling rate of 2 ° C., and to hold the calcined body at 300 to 600 ° C. in the oxidative heat treatment step (4).

[0009]

[Function] In the rare earth-based superconducting material of the present invention, (RECa) Ba
Particles made of (RECa) ₂ BaCuO ₅ are dispersed inside crystal grains made of ₂ Cu ₃ O _7-x . Many crystal grains composed of (RECa) Ba ₂ Cu ₃ O _{7-x form} the matrix of the superconducting material of the present invention. In (RECa) Ba ₂ Cu ₃ O _7-x and (RECa) ₂ BaCuO ₅ , (RE
The notation (Ca) does not mean that RE and Ca are equimolar, but the sum of both elements RE and Ca is (RECa) Ba ₂ Cu ₃ O.
It means that it is 1 unit in any of the composition formulas of _7-x and (RECa) ₂ BaCuO ₅ . That is, in (RECa) Ba ₂ Cu ₃ O _7-x , R
The sum of E and Ca and the molar ratio of Ba, Cu and O are 1: 2: 3: 7-
means x. Similarly for (RECa) ₂ BaCuO ₅ , R
The sum of E and Ca and the molar ratio of Ba, Cu and O are 2: 1: 1: 5.
Means to be. This is because Ca is considered to replace RE in the present invention. The Ca element contained in the rare earth-based superconducting material of the present invention is 2 to 15 mol% of the RE element contained in the rare earth-based superconducting material. This is because within this range, the 211 phase is finely dispersed in the 123 phase, and the critical current density of the superconducting material becomes high. Ca element is R
It is considered that when the content is less than 2 mol% of the E element, the (RECa) ₂ BaCuO ₅ particles are difficult to disperse sufficiently finely.
The Ca element contained in the rare earth-based superconducting material is preferably 5 to 12 mol% of the RE element contained in the rare earth-based superconducting material. This is because the critical current density of the superconducting material is further increased in this range.

Even with a crystal grain composed of (RECa) Ba ₂ Cu ₃ O _7-x ,
Even in particles composed of ECa) ₂ BaCuO ₅ , RE is a rare earth element. Since rare earth elements are similar in physical and chemical properties to each other, no matter what kind of rare earth element is used, the rare earth superconducting material does not exhibit unpredictable special properties. Further, no matter which rare earth element is used, the method for producing the rare earth-based superconducting material of the present invention is not particularly changed. The rare earth element represented by RE is not necessarily limited to one element, and any two or more rare earth elements may be mixed.
Can be expressed as Y _y Yb _1-y (y is a real number between 0 and 1 inclusive). Moreover, RE is Y, Sm, Eu, Dy, Ho,
It is preferable that at least one element in the group consisting of Er and Yb is formed. These rare earth elements are particularly close to one another in physical and chemical properties.
Further, it is more preferable that the rare earth element contains Y. Also, since (RECa) Ba ₂ Cu ₃ O _7-x is non-stoichiometric, x
Indicates a non-stoichiometric ratio of 0 or more and 1 or less, and x can be changed in this range by heat treatment in an appropriate atmosphere. It is preferable that x is 0.1 or more and 0.5 or less. This is because superconducting properties can be exhibited within this range.
Further, the crystal structure of (RECa) Ba ₂ Cu ₃ O _7-x has a common feature regardless of the rare earth element and has a multi-layer perovskite structure. Specific examples of the matrix include (YCa) Ba ₂
Cu ₃ O _7-x can be mentioned.

In the present invention, (R
A large number of particles composed of ECa) ₂ BaCuO ₅ are dispersed. This particle acts as the pin center and exerts a pinning effect. That is, even if the rare earth-based superconducting material of the present invention, which is a second-type superconductor, has a magnetic field that is greater than or equal to the lower critical magnetic field and less than or equal to the upper critical magnetic field, magnetic flux intrusion into the rare earth-based superconducting material begins. The magnetic flux can be trapped by these 211 phase particles and prevent the magnetic flux lines from moving due to Lorentz force. In the present invention, the reason why the particles composed of (RECa) ₂ BaCuO ₅ , that is, the so-called 211 phase is dispersed in the matrix is considered to be because Ca was added and the melting method was performed. Therefore, in order to obtain the superconducting material of the present invention, it is not necessary to add a compound such as platinum, rhodium, or cerium, which is conventionally added to disperse the 211 phase. However, it does not prevent the superconducting material of the present invention from containing platinum, rhodium, cerium or the like.

In the present invention, 98% or more of the particles are 2
It has a particle size of 0 μm or less. This is because the finer the particles are, the more effective the pinning effect is, even when the volume ratio of the particles is constant. Further, 90% or more of the particles preferably have a particle size of 5 μm or less,
More preferably, 95% or more of the particles have a particle size of 5 μm or less. The critical current density of the rare earth-based superconducting material when the critical current density is improved to 77K and the magnetic flux density is 0.5 Tesla is preferably 9000 amps / cm ² or more, and 12000 amps / cm ² or more. More preferable. The superconducting material of the present invention can exhibit such a critical current density because the 211 phase is finely dispersed as described above and the non-oxidation heat treatment described below is performed.

The method for producing the rare earth-based superconducting material of the present invention will be described below. This manufacturing method of the present invention is different from the conventional melting method for manufacturing a rare earth-based superconducting material,
(A) the molded body contains Ca element in an amount of 2 to 15 mol% of the RE element, and (b) after the molded body is baked and gradually cooled, before heat treatment in a normal oxidizing atmosphere, That is, the fired body is heat-treated in a non-oxidizing atmosphere. Since the molded body contains Ca element, 211 is contained in the 123-phase matrix.
It is thought that the phases are dispersed. Moreover, the critical current density of the superconducting material is remarkably improved by this non-oxidizing heat treatment step.

The manufacturing method of the present invention will be described below in sequence. First, a molded body containing at least RE, Ba, Cu, O and Ca elements is prepared. It is preferable to use a powder compounded in a predetermined composition. For example, rare earth element oxides such as RE ₂ O ₃ , hydroxides or carbonates, carbonates of Ba, hydroxides, oxides or peroxides, and oxides of Cu, hydroxides or carbonates, etc. The powder of can be used.
Further, calcium oxide, calcium carbonate, calcium hydroxide or the like can be used. Also, these RE, Ba,
A compound containing two or more elements of Cu, O and Ca may be used. A mixed powder obtained by mixing any of these compounds, a calcined powder, or a frit powder is also used. After firing (R
It is not particularly limited as long as it is blended so as to form ECa) Ba ₂ Cu ₃ O _7-x and (RECa) ₂ BaCuO ₅ .
Also, the particle size of the raw material powder is not particularly limited,
Generally, particles having a particle size of 1 to 10 μm are used.
These powders and the like are uniformly mixed into a mixed powder by a known method. The mixing method may be wet or dry. Then, using the mixed powder thus obtained, in order to have a predetermined shape, press molding, injection molding, cast molding,
A molded body is obtained using a known molding method such as isotropic pressure molding.
The shape of the molded body is arbitrary, and if necessary, a cylinder, a polygonal prism, a parallelepiped, a rectangular parallelepiped, a cone, a polygonal pyramid, a spheroid,
Contains shapes such as spheres. Further, the shape of the molded body also includes a shape obtained by plastically deforming these shapes in an arbitrary direction, or a shape obtained by cutting these shapes with a flat surface or a curved surface in an arbitrary direction. The shape of the molded body further includes a shape in which one or more holes are formed in any of the above shapes, for example, a cylinder or a donut shape.

When (RECa) Ba ₂ Cu ₃ O _7-x is decomposed and melted into (RECa) ₂ BaCuO ₅ and a liquid phase, and is formed at a temperature not higher than (RECa) ₂ BaCuO ₅ is decomposed and melted. The body is held so that the compact is fired into a semi-molten state. In this firing step, (RECa) Ba ₂ Cu ₃ O _7-x is decomposed and melted into a solid phase (RECa) ₂ BaCuO ₅ and a liquid phase. It is preferable to hold the molded body in the atmosphere because the operation is simple. The molded body may be heated to the holding temperature. For example, 1 per hour
It can be heated in the range of 00 to 400 ° C. Also,
It is also possible to put the molded body in a furnace kept at the firing temperature in advance.

The firing temperature is appropriately selected in consideration of the rare earth elements contained in the components used in the molded product, the size of the molded product, the heating conditions and the like. Specifically, if the rare earth element is Y, it is about 1000 to 1200 ° C., if it is Sm, it is about 1040 to 1230 ° C., and if it is Eu, it is about 1030 to 1 ° C.
200 ° C, Gd approx. 1080-1230 ° C, Dy
If about 1030 ~ 1210 ℃, Ho about 10
40 to 1190 ° C, if Er is about 1020 to 1170
In the case of C and Yb, it may be appropriately selected within the range of about 950 to 1150C. It is preferable to hold the heated compact at this firing temperature for 0.2 to 5 hours. 0.5-3
Holding for a time is more preferable. Next, this fired body is cooled from the firing temperature to a temperature at which gradual cooling is started. This cooling rate is not particularly limited. However, from the time efficiency, 50 to 400 ° C. per hour is preferable.

The fired body is gradually cooled, whereby (RECa) Ba
Crystal grains made of ₂ Cu ₃ O _7-x are grown, and grains made of (RECa) ₂ BaCuO ₅ are dispersed inside the crystal grains. In this slow cooling step, the crystal surface is covered so as to enclose the (RECa) ₂ BaCuO ₅ crystal.
While (RECa) ₂ BaCuO ₅ reacts with the liquid phase at the interface, (RECa) B
It is considered that a ₂ Cu ₃ O _7-x is precipitated at the interface and crystal grains composed of (RECa) Ba ₂ Cu ₃ O _7-x grow. The gradual cooling start temperature is appropriately selected from the temperature range of about 20 ° C. from the peritectic point,
select. It is preferable to start gradual cooling from a temperature higher than the peritectic point. Slow cooling rate is 0.1-2 ° C per hour
Is preferably, and more preferably 0.2 to 1.5 ° C. It is preferable to lower the temperature by 70 ° C. or more by slow cooling, and usually the temperature is lowered by 80 to 150 ° C. However, even if gradually cooled to a temperature lower than that, there is no particular problem except that it takes time. For example, for (YCa) Ba ₂ Cu ₃ O _{7- x} , 1050 ° C to 980 ° C
It is preferable to gradually cool from a certain temperature of 940 ° C to a certain temperature of 850 ° C.

In the manufacturing method of the present invention, after the gradual cooling, the molded body is held at a temperature lower than the gradual cooling temperature in a non-oxidizing atmosphere and heat-treated. By performing this heat treatment before the heat treatment in the usual oxidizing atmosphere, even if the calcined body contains Ca, the rare earth-based superconducting composition exhibits satisfactory superconducting properties. The non-oxidizing atmosphere is an atmosphere that does not contain a gas having an oxidizing power such as oxygen. The non-oxidizing atmosphere is preferably an inert atmosphere made of an inert gas such as nitrogen or argon. Hydrogen may be contained in the non-oxidizing atmosphere. As the heat treatment, 50
It is preferable to maintain the temperature at 0 ° C or higher and 900 ° C or lower. 90
If the temperature is kept higher than 0 ° C, the 123 phase may be decomposed. Further, if the temperature is lower than 500 ° C., it takes a long time to obtain the effect of this heat treatment, which is not preferable. This heat treatment temperature is 600 ° C or higher and 900 ° C
The following is more preferable. After the slow cooling step,
Before this non-oxidizing heat treatment step, the temperature may be gradually cooled and then lowered to the heat treatment temperature as it is, or the temperature may be once lowered to room temperature and then heated again to the heat treatment temperature. .

After this non-oxidizing heat treatment step, a heat treatment which is usually carried out by a melting method of the rare earth superconducting material is performed. That is, the fired body is held at a temperature lower than the slow cooling temperature in an oxidizing atmosphere. The oxidizing atmosphere is preferably an atmosphere containing 30% by volume or more of oxygen, more preferably an atmosphere containing 90% by volume or more of oxygen, still more preferably an atmosphere containing 99% by volume or more of oxygen. By this oxidation heat treatment, an appropriate amount of oxygen is absorbed in the (RECa) Ba ₂ Cu ₃ O _7-x of the matrix of the superconducting material, and the oxygen composition ratio x is adjusted. This heat treatment is preferably performed at a temperature of 300 to 600 ° C. For example, at 600 ° C., 5 to 40 hours, 5
10 to 70 hours at 00 ° C, 20 at 400 ° C
It is preferred to hold for ~ 100 hours.

[0020]

EXAMPLES The present invention will be described in detail below with reference to examples. However, the present invention is not limited to the following examples. (Example 1-5; Comparative Examples 1 and 2) a _{Y 2 O 3, CaCO 3,} BaCO 3 and CuO powders, Y element, Ca elements, the molar ratio of Ba element, and Cu element in the ratios shown in Table 1 Mixed so that That is, Y
And Ca: the molar ratio of Ba: Cu is 1.8: 2.4:
The mixture was mixed so as to be 3.4, and the molar ratio of the Ca element to the Y element was changed from 0 to 16.1.

[0021]

[Table 1]

Each of the mixed powders was mixed with ethanol as a solvent in a wet ball mill for 5 hours and then dried. While flowing an oxygen stream to the dried mixed powder,
It was calcined by calcination at 00 ° C. for 10 hours. Next, this calcined body was pulverized for 15 hours in a rotary mill using zirconia boulders, and the average particle size was about 3 μm, and the composition was as follows.
(YCa) to obtain a calcined powder is _{1.8 Ba 2.4 Cu 3.4 O 7-} x. This calcined powder was press-molded at a pressure of 100 kgf / cm ² to form a disc-shaped compact having a diameter of 30 mm and a height of 10 mm. The molded body on a high-purity alumina plate was baked in an electric furnace in the air atmosphere at 1150 ° C. for 1 hour to be in a semi-molten state. Then 1150 ° C to 1000 ° C
The fired body was cooled at a rate of 100 ° C. per hour. Then, the fired body was gradually cooled from 1000 ° C. to 900 ° C. at a rate of 1.0 ° C. per hour, and (RECa) Ba ₂ Cu ₃ O was added.
_7-x grains were grown.

The fired body was furnace-cooled to room temperature, and the fired body was divided into two. Next, this one fired body was subjected to the heat treatment A of the present invention, and the other fired body was subjected to the conventional heat treatment B. In the heat treatment A of the present invention, the fired body was held at 800 ° C. for 20 hours in a furnace in a nitrogen atmosphere, and then,
The fired body was kept in an oxygen atmosphere at 450 ° C. for 72 hours. On the other hand, in the conventional heat treatment B, the fired body was held at 450 ° C. for 72 hours in a furnace in an oxygen atmosphere. A sample having a rectangular parallelepiped shape (1 mm × 1 mm × 5 mm) was cut out from each fired body, and the critical current density at 77 K and a magnetic flux density of 0.5 Tesla was measured by a magnetization method. The measurement results of this critical current density are summarized in Table 1.

When the surface of the rare earth superconducting material thus obtained was polished and observed with an optical microscope, Examples 1 to 5 were obtained.
In the rare earth-based superconducting material containing Ca of Comparative Example 2, 98% or more of the 211 phase particles had a particle size of 20 μm or less. Further, 95% or more of the particles had a particle size of 5 μm or less. In any of the fired bodies of Examples 1 to 5, the critical current density was significantly improved when the heat treatment A of the present invention was performed than when the conventional heat treatment B was performed. This tendency was remarkable especially when the Ca content increased.

[0025]

In the rare earth-based superconducting material of the present invention, the particles of the 211 phase are finely dispersed in the 123 phase matrix by containing a predetermined amount of Ca. Therefore, even if the magnetic flux acts as a pin center and the magnetic flux starts to penetrate into the rare earth-based superconducting material in a magnetic field that is greater than or equal to the lower critical magnetic field of the rare earth-based superconducting material and less than or equal to the upper critical magnetic field, the Lorentz The force can prevent the magnetic flux lines from moving. Further, in the method for producing a rare earth-based superconducting material of the present invention, since the molded body contains a predetermined amount of Ca, the 211 phase can be dispersed in the 123-phase matrix in the rare earth-based superconducting material.
Further, in the method for producing a rare earth-based superconducting material of the present invention,
By subjecting the fired body to a heat treatment in a non-oxidizing atmosphere after the fired body is gradually cooled and before the heat treatment in a normal oxidizing atmosphere, the critical current of the rare earth-based superconducting material containing a predetermined amount of Ca. The density can be remarkably improved.

Claims (8)

[Claims] 1. A (RECa) Ba ₂ Cu ₃ O constituting a matrix.
_7-x crystal grains and dispersed inside the crystal grains (RE
Ca) ₂ BaCuO ₅ and a large number of particles
E is a rare earth element, and x is 0 or more and 1 or less,
98% or more of the particles are rare earth-based superconducting materials having a particle size of 20 μm or less, and Ca element contained in the rare earth-based superconducting material is 2 of RE elements contained in the rare earth-based superconducting material. The rare earth-based superconducting material is characterized by being ˜15 mol%. 2. The rare earth-based superconducting material according to claim 1, wherein 90% or more of the particles have a particle size of 5 μm or less. 3. C contained in the rare earth-based superconducting material
The rare earth superconducting material according to claim 1 or 2, wherein the element a is 5 to 12 mol% of the RE element contained in the rare earth superconducting material. 4. The critical current density of the rare earth-based superconducting material at a magnetic flux density of 0.5 Tesla at 77K is 90.
The rare earth-based superconducting material according to claim 1, 2 or 3, wherein the amperage is 00 amperes / cm ² or more. 5. The rare earth element is Y, Sm, Eu or D.
The rare earth-based superconducting material according to claim 1, wherein the rare earth-based superconducting material is made of at least one element selected from the group consisting of y, Ho, Er, and Yb. 6. The rare earth-based superconducting material according to claim 5, wherein the rare earth element contains Y. 7. (1) At least RE, Ba, Cu, O 2 and
(RECa) Ba ₂ Cu ₃ O _7-x is (RECa) ₂ BaC
It is higher than the temperature at which it decomposes and melts into uO ₅ and liquid phase,
ECa) ₂ BaCuO ₅ is maintained below the temperature at which it decomposes and melts, whereby the compact is fired into a semi-molten state, and the Ca element is contained in the compact in an amount of 2 to 15 mol% of the RE element. Contained, the RE is a rare earth element, the x is 0 or more and 1 or less, and (2) the fired body is gradually cooled, whereby (RECa) Ba
_A crystal grain composed of ₂ Cu ₃ O _7-x is grown, and inside the crystal grain, particles composed of (RECa) ₂ BaCuO ₅ are dispersed,
(3) Rare earth characterized by subjecting the fired body to a non-oxidizing heat treatment in a non-oxidizing atmosphere, and then (4) subjecting the fired body to an oxidative heat treatment at a temperature lower than the annealing temperature in an oxidizing atmosphere. -Based superconducting material manufacturing method. 8. The method for producing a rare earth-based superconducting material according to claim 7, wherein the fired body is held at 500 ° C. or higher and 900 ° C. or lower in the non-oxidation heat treatment step.