JPH013058A - Method for manufacturing superconducting materials - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing superconducting materials. More specifically, the present invention relates to a method for producing a novel superconducting material having a high superconducting critical temperature.

Background of the Invention Superconductivity is a phenomenon in which an object exhibits complete diamagnetic properties under certain conditions, and no potential difference appears even though a finite steady current is flowing inside the object. Substances in this state are called superconductors, and various applications have been proposed for them as transmission media with no power loss.

For example, if superconducting technology is applied to power transmission, it will be possible to significantly reduce the approximately 7% transmission loss that currently occurs with power transmission. Furthermore, superconducting power storage is said to be the most efficient power storage method known today.

Furthermore, its application to electromagnets for generating high magnetic fields was realized at the earliest, and the field of use is extremely wide. In the field of power generation technology, along with MHD power generation and electric motors, it is expected to be a technology that advantageously promotes the realization of nuclear fusion reactions, which are said to consume more power than the amount of power generated. Furthermore, in the field of transportation equipment, it is expected to be used as a power source for magnetic levitation trains, electromagnetic propulsion ships, etc., and in the field of measurement and medicine, it is expected to be used in NMR 1π meson therapy, high-energy physical experiment equipment, etc.

Furthermore, when multiple superconductors are weakly bonded, the Josephson effect, which is a macroscopic manifestation of the single-child effect, is observed. A tunnel junction type Josephson device that utilizes this effect is expected to be an extremely high-speed and low-power switching device because the energy gamut of the superconductor is small. Furthermore, since the Josephson effect on electromagnetic waves and magnetic fields appears as a sensitive quantum phenomenon, it has also been proposed to use this element as an ultra-sensitive sensor for magnetic fields, microwaves, radiation, etc.

In this way, superconducting technology is said to be an important technology, along with the practical application of nuclear fusion, as a technology that responds to the social need to improve power efficiency in all fields.

By the way, in conventional technology, superconducting phenomena have been observed only at extremely low temperatures. That is, among conventionally developed superconducting materials, it is believed that a group of substances with an A-15 type crystal structure exhibit a relatively high Tc (superconducting critical temperature), and it is said that Tc is the highest. Even in Nb3Ge, Tc is still 23.2
It stopped at K.

Therefore, conventionally, in order to implement the superconducting phenomenon, superconducting materials are cooled to below Tc using liquid helium with a boiling point of 4.2. In addition, for Tc of 23.2 K, it is possible to use liquid hydrogen with a boiling point of 20, but the critical temperature Tc is generally the temperature at which the superconducting phenomenon starts,
The temperature T at which the phase transition of a substance ends and the electrical resistance becomes zero. F
is even lower than the critical temperature Tc. Therefore, even if the material is cooled down to 20K using liquid hydrogen as a cooling medium, a superconductor cannot be obtained.

However, when liquid helium is used, the technical burden and cost burden due to cooling equipment including liquefaction equipment is extremely large, which negates the energy-saving effect of superconducting technology. Furthermore, helium is a substance that is naturally present in small amounts, and some estimates suggest that it will be depleted after the 1990s.

In particular, Japan does not produce liquid helium, and currently relies entirely on imports. Therefore, moving away from the use of helium is one of the extremely important issues in the practical application of superconducting technology.

Furthermore, it is known that the superconducting phenomenon is influenced by the magnetic field in the space in which the superconducting material is placed, and type 1 superconductors easily lose their superconducting effect in a considerably low lower critical magnetic field Hcl. In addition, even in type 2 superconductors, certain H
At C2, the superconducting phenomenon disappears. Therefore, in consideration of the above-mentioned application to electromagnets for generating high magnetic fields, a superconducting material with a high critical magnetic field is required. Although it is currently only a rule of thumb, it is known that in order to obtain a high critical magnetic field, it is preferable for the material to have a high critical temperature, and from this point of view as well, it is desired to improve the Tc of superconducting materials. There is.

Problems to be Solved by the Invention On the other hand, despite various efforts over a long period of time, the Tc of superconducting materials could not exceed 23K of Nb3Ge, but in recent years, group IIa elements or IIIa
It has been reported that a sintered body containing an oxide of a group element can become a superconductor with a high Tc, and the possibility of realizing a non-low temperature superconductor is rapidly increasing.

In already reported examples, [La, Bal 2Cu
On or l:La, Sr:l2CuOs etc.2
NIFJ type oxides are mentioned, and these are thought to have a crystal structure similar to perovskite type superconducting oxides. In these materials, dramatically higher Tc was observed compared to the conventional ones of 30 to 50, and even 70 to 50.
More than T. In some cases, this has been observed.

However, as mentioned above, it must be said that this is still insufficient to use an inexpensive and easily available cooling medium such as liquid nitrogen.

Furthermore, in actual use of superconducting materials, a technique for molding them into a predetermined shape is required.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art and to provide a method for producing a novel superconducting material having a high critical temperature Tc and in which liquid nitrogen can be used as a cooling medium.

A further object of the invention is to obtain high Tc as well as T. It is an object of the present invention to provide a method for manufacturing a novel superconducting material which has F and whose properties are stable over a long period of time.

In this specification, the superconductivity starting temperature or critical temperature of a superconducting material is Tc, and the phase transition end temperature at which the electrical resistance of the material becomes completely zero is T. ,, the difference between To and TCP is ΔT
Expressed as

Means for Solving the Problems The present inventors have devised various methods to improve superconducting properties based on the assumption that superconductivity in Ba-Tm-Cu-0 based superconducting materials is mainly caused by substances at grain boundaries. As a result of repeated experiments and studies, they succeeded in producing a material with a high superconducting critical temperature by forming crystals with small grain sizes.

That is, according to the present invention, each average particle size is 20
Ba, Tm, Cu oxides and carbonates of μm or less, preferably 10 μm or less, more preferably 5 μm or less,
After mixing sulfate or nitrate powder and pulverizing the pre-sintered sintered body to an average particle size of 5 μm or less, preferably 3 μm or less, and molding it, the melting point of the sintered body powder is
A superconductor having a high critical temperature characterized by forming a perovskite-type or pseudo-perovskite-type oxide having an average crystal grain size of 10 μm or less by main sintering at a temperature in the range of melting point of the above-mentioned sintered body powder (=100°C). A method of manufacturing a material is provided. The fired body powder to be subjected to main sintering has an average particle size of 1
It is preferable to crush the particles to a size of μm or less.

Furthermore, according to a preferred embodiment of the present invention, the obtained sintered superconducting material is represented by the following general formula, (Ba, -, Tm
,)CuyOz (However, xSy is a real number between 0 and 1, and 2 is a real number between 0 and 4) Ba , Tm, Cu oxide, carbonate, sulfate, or nitrate powder is mixed and the mixed powder is sintered to produce a superconducting material.

Further according to a preferred embodiment of the invention, VSNb.

TaSMo, 'vV, Ti, Cr, Mn, Ga5I
oxide or carbonate of at least one element selected from the group consisting of n, Cd, Sn, TI, Pb, and Zn;
Sulfate or nitrate powder is added to the mixed powder to further reduce the grain size of the sintered body and increase the critical temperature.

These V, Nb, Ta, Mo, WSTi, Cr,
Mn, Ga5In5CdSSn.

It is preferable that the atomic ratio of Cu to at least one element selected from the group consisting of TI and PbS2n is A4.

Furthermore, according to a preferred embodiment of the present invention, the preliminary sintering is performed at 7
The crystal grain size of the obtained sintered body is reduced by carrying out the process at a temperature of 00 to 1000°C and repeating the steps of preliminary sintering, pulverization, and molding at least three times.

Furthermore, the fired body after the final preliminary sintering, that is, the fired body to be subjected to main sintering, has an average particle size of 3 μm, particularly preferably 1 μm.
It is preferable to crush the powder to a size of less than m. This pulverization is carried out, for example, by A.
It can be done by a ball mill using 12Ch balls, or
Alternatively, it can be carried out by a jet mill that uses air, Ar or N2 as a medium and impinges a jet stream on an Al2O3 target. It is preferable that the thus pulverized sintered body is molded to a relative density of 60 to 80% and then subjected to main sintering.

Furthermore, according to a preferred embodiment of the present invention, the pulverized fired body is shaped into a shape with a distance from the center to the surface of 1 mm or less, preferably 0.6 mm or less, such as a tape shape with a thickness of 1.2 mm or less or a diameter of 1.2 mm or less. It is formed into a wire rod and sintered. A doctor blade method may be used to form a tape, and an extrusion method may be used to form a wire. Also, during molding, polyvinyl butyral (PV
B) as a binder, dibutyl chloride (DBP)
) is preferably used as a plasticizer. Alternatively, molding may be performed using water as a solvent and polyvinyl alcohol (PVA) as a binder. Before main sintering these molded bodies, it is preferable to heat them in the air to a temperature in the range of 400°C to 800°C to remove the solvent and binder.

Furthermore, according to a preferred embodiment of the present invention, preliminary sintering and/or main sintering is performed in an oxygen atmosphere with a partial pressure of 5 to 2,500 atmospheres to reach the superconducting critical temperature T. can be significantly improved.

Furthermore, according to a preferred embodiment of the present invention, the sintered body after main sintering is heat-treated in the range of 500 to 800°C.

The heat treatment may be performed in an atmosphere with a partial pressure of 10 −1 Torr or less.

Furthermore, according to another embodiment of the main sintering, the material can be reheated immediately after sintering or after sintering to a temperature in the range of 500 to 800° C., and then rapidly cooled to form a finer crystal structure and raise the superconducting critical temperature.

The present invention is based on the knowledge that in superconductors made of perovskite or pseudo-perovskite oxides, substances with high superconducting critical temperatures are likely to be formed at grain boundaries, that is, at interfaces between grains.

That is, based on the above findings, the present inventors succeeded in forming a superconducting material having an extremely high critical temperature by microstructuring a sintered body made of perovskite or pseudo-perovskite oxide.

In order to obtain a perovskite or pseudo-perovskite oxide sintered body with such a fine structure, the following points must be strictly controlled.

■ Particle size of material powder before preliminary sintering ■ Particle size of powder after preliminary sintering and crushing ■ Preliminary sintering temperature ■ Main sintering temperature As will be described later, among the above control items, especially ■ ■
Also, ■ is important.

That is, if the average particle size of the raw material powder before pre-sintering exceeds 20 μm, the grains cannot be sufficiently refined even in the pulverization process after pre-sintering, and the finished sintered body will have coarse grains of 6 μm or more. It becomes. Therefore, in order to refine the crystal grains of the sintered body, it is essential that the particle size of the raw material powder is 20 μm or less. Further, the particle size of the raw material powder is preferably 10 μm or less, and even more preferably 5 μm or less. When the particle size of the raw material powder is 10 μm, it is easy to form into a thin layer, and when it is 5 μm or less, Tc becomes particularly high, and the difference ΔT from T CP becomes small. In particular, ΔT
is improved in proportion to the square of the particle size.

In addition, the crushing process after preliminary sintering has a direct effect on the crystal grain size after main sintering, and the particle size of the powder after crushing is 5 μm.
If it exceeds this, the grain size of the sintered body after main sintering will increase and the amount of grain boundaries will decrease. As mentioned above, grain boundary reduction is unfavorable for achieving high Tc. Therefore, the particle size is reduced to 5 μm or less, preferably 3 μm or less, by pulverization after preliminary sintering. Furthermore, if the powder is pulverized to 1 μm or less, the crystal grain size of the sintered body becomes smaller and the superconducting critical temperature increases. However, pulverizing the fired body to less than 1 μm requires a long processing time and increases the possibility of contamination with impurities, so care must be taken.

By repeating the process of [preliminary sintering → crushing → molding] multiple times, the solid solution reaction of the raw material powder or fired body is promoted, and the crystal grain size of the powder to be used for main sintering is refined. It is preferable.

From these viewpoints, it is preferable that the series of steps described above [preliminary sintering → crushing → molding] be repeated at least three times.

Further, the main sintering temperature is an extremely important control factor in the method according to the present invention, and the sintering proceeds only by phase reaction without melting of the material during the main sintering, and
It is necessary to control the crystal growth of the sintered perovskite-type or pseudo-perovskite-type oxide so that it does not become excessive. As a result of repeated experiments based on these findings, we found that if the main sintering temperature is low, the final sintered body will not have sufficient strength, whereas if it is heated beyond the melting point of the sintered body, sintering will occur. A molten phase is formed in the solid, or coarse crystal grains are formed. Therefore, in the present invention, the main sintering temperature is (melting point of the above-mentioned sintered body powder) - (melting point of the above-mentioned sintered body powder -
100°C).

Furthermore, for the same reason as the control of the main sintering described above, the preliminary sintering temperature should also be strictly controlled. That is, when the preliminary sintering temperature is less than 700° C., the solid solution reaction does not proceed sufficiently, and a perovskite or pseudo-perovskite oxide that is effective in increasing the superconducting critical temperature cannot be obtained. On the other hand, if the preliminary sintering temperature exceeds 1000°C, as in the case of main sintering, a molten phase will occur in the fired body or the crystal grains will become coarser, making it difficult to refine them by pulverization in the subsequent process. Become. Note that the pre-sintering here refers to an operation also called firing in the ceramics field.

Furthermore, when molding the fired body before main sintering, it is preferable that the relative density of the molded body is 60 to 80%. According to the findings of the present inventors, a superconductor made of a perovskite or pseudo-perovskite oxide exhibits excellent properties, particularly near the surface of a sintered body. This is because the material is thin, so the reaction with the atmosphere during sintering or heat treatment favors superconducting properties, and the phase near the surface of the ceramic is subject to strain effects, resulting in excellent superconducting properties. It is thought that it was released.

Therefore, in the method of the present invention, the relative density of the molded body is kept relatively low at 60 to 80%, and operations are performed so that the same effect as near the surface penetrates into a deeper region during main sintering. In addition, based on the same reason, the thickness of the molded body was reduced to 2 m by the doctor blade method or extrusion molding method.
It is also within the scope of the present invention to make the entire sintered body a superconductor with good characteristics by making it into a tape shape with a diameter of 1.2 mm or less, preferably 1.2 mm or less, or a wire shape with a diameter of 1.2 mm or less. It is in.

The reason why the thickness or diameter of the tape-shaped or wire-shaped compact is set to 2 mm or less is to reduce shrinkage during sintering, since the above-mentioned surface effect mainly occurs within 2 mm from the surface. Taking this into consideration, the thickness was determined to be 2 mm or less.

Furthermore, in a preferred method of the present invention, the obtained sintered superconducting material is represented by the following general formula, (Ba14Tm,)
cuyO Cu oxide, carbonate,
Mix sulfate or nitrate powder. Ba:Tm:C
If the raw material powder is mixed with the atomic ratio of u outside the above range, the desired perovskite or pseudo-perovskite oxide cannot be obtained. Furthermore, VSNb,
Ta! , 4o, W, Ti5Cr, Mn,
Ga, In, Cd.

It is preferable to reduce the crystal grain size of the sintered body by adding powder of oxide, carbonate, sulfate or nitrate of one or more elements such as Sn, TI, PB or Zn, but these elements The atomic ratio between Cu and Cu is 0.01 to 0.15
When the amount is lower than the range of 0.0, no addition effect can be obtained;
If it is higher than the range of 0.01 to 0.15, the effect of addition is saturated or the desired perovskite type or pseudo-perovskite type oxide cannot be obtained. These V, Nb,
Ta, Mo, W, Ti, Cr, Mn5Ga, In
.

By adding one or more elements of Cd5Sn, TI, Pb, or Zn, the current value of the sintered superconducting material increases. This is thought to be due to the formation of electron holes due to the addition.

Furthermore, according to a preferred embodiment of the present invention, the obtained sintered body is further heat-treated to form a substantially uniform pseudo-perovskite oxide. This heat treatment significantly increases the superconducting critical temperature at which electrical resistance becomes completely zero. This heat treatment is preferably carried out at a temperature in the range of 500 to 800°C, more preferably carried out in an oxygen cloud atmosphere under reduced pressure. That is, by this heat treatment under a low oxygen partial pressure, oxygen atoms are absorbed from the sintered body, and oxygen defects are generated.

It is estimated that the carriers generated by this defect increase the probability of forming a Cooper pair of electrons, and the superconducting critical temperature at which the resistance becomes completely zero increases significantly.

Note that if the heating temperature is less than 500° C., the desired heat treatment effect may not be obtained or a long time heat treatment will be required. On the other hand, at a treatment temperature exceeding 800° C., the crystal structure of the perovskite-type or pseudo-perovskite-type oxide having a superconducting effect disappears, and the critical temperature decreases significantly.

By heat treatment of these ceramics after sintering,
ΔT increases by an additional 3-5°C, so higher T. , is obtained. The heat treatment is preferably performed under a reduced oxygen pressure of IQ'torr or less. The reason for this is that at higher oxygen partial pressures, it takes a long time to form oxygen vacancies, which is not industrially practical, and at temperatures below 500°C or above 800°C, the formation of oxygen vacancies becomes too small or too large. T high enough. , is difficult to obtain.

Furthermore, according to a preferred embodiment of the present invention, the superconducting critical temperature can be further raised by quenching immediately after the sintering, or by reheating to a temperature in the range of 500 to 800°C and quenching after sintering. Through this rapid cooling treatment, the sintered body produced by the method of the present invention has a pseudo-perovskite structure having superior superconducting properties.

Furthermore, it has been found that by following these preferred embodiments of the present invention, the composition of the superconducting material is made uniform and stable, and as will be specifically described later, there is little deterioration of the characteristics over time.

Furthermore, the present inventors have discovered that when the thickness from the surface to the center is 1 mm or less, preferably 0.6 mm, the entire ceramic has excellent superconducting properties, that is, it consists of a structure with a low superconducting critical temperature. This is because the thickness is thin.
It is thought that the reaction with the atmosphere during sintering or heat treatment progresses favorably to improve superconducting properties, and the surface portion of the ceramic is subject to oxygen defects and/or strain effects, resulting in excellent superconducting properties.

Furthermore, sintering is not limited to one time, and it has been confirmed that further homogenization of the material can be achieved by crushing the previously sintered material and sintering it again. That is, the process is carried out in at least three stages: a preliminary sintering process in which the sintered body obtained after calcining the powder material is crushed, and a main sintering process in which the powder obtained after the preliminary sintering is shaped and sintered. That is preferable.

EXAMPLES The present invention will be specifically explained by examples below, but the technical scope of the present invention is not limited by the following disclosure.

Example 1 Each powder of BaCO3, Tm2O3, and CuO with a purity of 3N or more was mixed with Ba:T in a ratio of 0.6:0.4:0.4.
They were mixed to have an atomic ratio of m:Cu.

These mixed powders were each pulverized to obtain powders having the average particle diameters shown in Table 1. Each of the mixed powders was calcined in the air at 900° C. for 12 hours, and the powder solidified into a cake was further ground in a ball mill until it had the average particle size shown in Table 1. Repeat this process three times,
The solid solution was almost completely dissolved, and in the final pulverization step before firing, a powder having the average particle size shown in Table 1 was obtained. Each of the powders obtained as described above was filled into a rubber mold and subjected to static pressure molding at a pressure of 1 tOn/cIIl to obtain a bulk molded body of 30φ×5Qmm.

A molded body having the dimensions shown in Table 1 was cut out from this molded body by machining.

Subsequently, the molded body was held in the atmosphere at 930° C. for 10 hours and sintered to obtain a ceramic sintered body.

Gold was deposited on the fractured surface of each of the obtained sintered bodies and observed using a scanning microscope. The average particle diameter of the sintered body thus measured is also shown in Table 1.

The critical temperature Tc and TCF were measured using a direct current four-point probe method in a cryostat with electrodes made of Ag conductive paste attached to both ends of the sample according to a standard method. Temperature was measured using a calibrated Au (Fe)-Ag thermocouple. Changes in resistance were observed while increasing the temperature little by little. Furthermore, Table 1 shows Tc and T. , the difference Δ
T is also listed.

Furthermore, when each material was measured under the same conditions three weeks after producing these superconducting materials, the change in Tc of the sintered bodies produced according to the present invention was within the range of ±IK, and no significant change was observed. There wasn't. This was also confirmed by the measurement results of AC magnetic susceptibility measured using an L meter.

Example 2 BaCO5,'l with a purity of 3N or more and an average particle size of 6 μm or less
``m2(13, CaO, V2O5 or Ta205 powders after firing Baz Tms CUs V or Ta atomic ratio is 0.6:0,4:0.4
:0.02 or 0.8 :0.2 :1.0:
They were mixed so that the ratio was 0.05. This mixed powder is injected and collided with an Al2O3 target using air as a medium.
The average particle size was μm. The obtained mixed powder was heated at 890°C/1 in a N2-0□ mixed gas atmosphere with a 0□ partial pressure of 1 atm.
It was baked for 2 hours. The cake-like solidified powder was further ground to 2 μm using a jet mill similar to the above. below,
This process was repeated three times. During molding, this powder is kneaded with PVE (polyvinyl butiere) using a toluene-based solvent as a binder, and DBP (
+'butyl phthalate) was added as a plasticizer, and after forming with a doctor blade, it was cut into 4 mm width and the binder was removed at 600°C in the air.

Each of the above molded bodies was heated at 92°C in an atmosphere of 100atm.
It was sintered by holding at 0° C. for 5 hours to obtain a sintered body.

In addition, the critical temperature T. and T. The measurement of F was carried out using a direct current four-point probe method in a Talainestat by attaching electrodes to both ends of the sample using conductive paste according to a standard method. Temperature was measured using a calibrated Au (Fe)-Ag thermocouple. Changes in resistance were observed while increasing the temperature little by little.

Tc of the sintered body containing ■ is 127, KSTCF is 12
4, and on the other hand, T of the sintered body containing Ta. is 12
5KSTap was at 121.

In addition, when the same material was measured under the same conditions after 3 weeks, the change in Tc was within ±1°, and there was no significant change in S.
I couldn't bear it.

This was also confirmed by the measurement results of AC magnetic susceptibility measured using an L meter.

As described in detail, the superconducting sintered body produced by the method of the present invention exhibits a fine crystal structure and a high and stable T. shows.

Furthermore, V, NbSTaSMo, WSTiSCr,
Ga, In.

Addition of Cd, Sn, TI, Pb or Zn results in an even finer crystal structure and higher T. is obtained. Further, Tc can be significantly improved by sintering in a 0□ atmosphere of 5 to 2500 atm.

Furthermore, by manufacturing according to a preferred embodiment of the present invention with a thickness from the surface to the center of 1 mm or less, preferably 0.5 mm or less, uniformity in oxygen defect concentration is achieved;
Small ΔT, high T. , is obtained.

Since such a high and stable Tc can be obtained, it is possible to obtain superconducting ceramics that are inexpensive and use liquid nitrogen as a coolant over time.

These superconducting ceramics can be used as thin plates, thin wires, or small parts, or can be made into thin films by sputtering, etc., and can be used as Josephson elements, 5QUIDs, etc.
It can be applied to a wide range of fields such as (magnetometers), superconducting magnets, infrared sensor elements, and motors.

Patent applicant: Sumitomo Electric Industries, Ltd.

Claims (29)

[Claims] (1) Ba and Tm each having an average particle size of 20 μm or less
, Cu oxide, carbonate, sulfate or nitrate powder is mixed, the pre-sintered sintered body is pulverized to an average particle size of 5 μm or less, and after molding, (melting point of the above sintered body powder) ~
(melting point of the above-mentioned sintered body powder - 100°C) to form a perovskite-type or pseudo-perovskite-type oxide with an average crystal grain size of 10 μm or less, and has a high critical temperature. A method for producing superconducting materials. (2) The high critical temperature according to claim 1, characterized in that each of the powders of oxides, carbonates, sulfates, or nitrates of Ba, Tm, and Cu has an average particle size of 10 μm or less. A method for producing a superconducting material having (3) The high critical temperature according to claim 1, wherein the average particle size of each of the powders of oxides, carbonates, sulfates, or nitrates of Ba, Tm, and Cu is 5 μm or less. A method for producing a superconducting material having (4) The obtained sintered superconducting material is represented by the following general formula, (Ba_1_−_xTm_x)Cu_yO_2 However,
x and y are real numbers from 0 to 1, and z is a real number from 0 to 4.) Ba, Tm, and Cu are selected so that x and y are 0.1 to 0.9 and 0.4 to 1.0, respectively. A method for producing a superconducting material having a high critical temperature according to any one of claims 1 to 3, characterized by mixing powders of oxides, carbonates, sulfates, or nitrates of . (5) Furthermore, V, Nb, Ta, Mo, W, Ti, Cr
, an oxide of at least one element selected from the group consisting of Mn, Ga, In, Cd, Sn, Tl, Pb, and Zn;
Any one of claims 1 to 4, characterized in that powders of carbonate, sulfate or nitrate are mixed.
A method for producing a superconducting material having a high critical temperature as described in 2. (6) V, Nb, Ta, Mo, W, Ti, Cr, Mn,
Claim No. 1, characterized in that the atomic ratio of Cu to at least one element selected from the group consisting of Ga, In, Cd, Sn, Tl, Pb, and Zn is 0.01 to 0.15. A method for producing a superconducting material having a high critical temperature according to item 5. (7) A method for producing a superconducting material having a high critical temperature according to any one of claims 1 to 4, characterized in that preliminary sintering is carried out at a temperature in the range of 700 to 1000°C. . (8) At least 3 steps of pre-sintering, crushing and molding
A method for producing a superconducting material having a high critical temperature according to any one of claims 1 to 7, wherein the method is repeated several times. (9) Among the fired bodies after preliminary sintering, at least the fired bodies to be subjected to main sintering are pulverized to an average particle size of 3 μm or less.
A method for producing a superconducting material having a high critical temperature as described in 2. (10) The method for producing a superconducting material having a high critical temperature according to claim 9, wherein the pulverization is performed using a ball mill. (11) At least 5 using Al_2O_3 balls
Claim 10, characterized in that time pulverization is performed.
A method for producing a superconducting material having a high critical temperature as described in 2. (12) The method for producing a superconducting material according to claim 9, wherein the pulverization is performed using a jet mill. (13) Using air, Ar or N_2 as a medium, Al_2
13. The method for producing a superconducting material having a high critical temperature according to claim 12, wherein the pulverization is performed by impinging a jet stream on an O_3 target. (14) Claim 1, characterized in that the pulverized fired body is molded to a relative density of 60 to 80% and subjected to main sintering.
A method for producing a superconducting material having a high critical temperature according to any one of Items 1 to 13. (15) The pulverized fired body is formed into a shape with a distance from the center to the surface of 1 mm or less, and is then sintered. A method for producing a superconducting material having a high critical temperature as described above. (16) The pulverized fired body is formed into a shape with a distance from the center to the surface of 0.6 mm or less, and is sintered, which has a high critical temperature as set forth in claim 15. Method for manufacturing superconducting materials. (17) Production of a superconducting material having a high critical temperature according to claim 15, characterized in that the pulverized fired body is formed into a tape shape with a thickness of 2 mm or less, preferably 1.2 mm or less. Method. (18) A method for producing a superconducting material having a high critical temperature according to claim 17, characterized in that the pulverized fired body is molded by a doctor blade method. (19) A method for producing a superconducting material having a high critical temperature according to claim 15, characterized in that the pulverized fired body is formed into a wire rod having a diameter of 2 mm or less, preferably 1.2 mm or less. (20) A method for producing a superconducting material having a high critical temperature according to claim 19, characterized in that the pulverized fired body is molded by an extrusion method. (21) The above-mentioned pulverized fired body was mixed with polyvinyl butyral (
21. A method for producing a superconducting material having a high critical temperature according to claims 1 to 20, characterized in that the superconducting material is molded using PVB) as a binder. (22) Dibutyl phthalate (D
22. A method for producing a superconducting material having a high critical temperature according to claims 1 to 21, characterized in that the superconducting material is molded using BP) as a plasticizer. (23) The pulverized fired body is molded using water as a solvent and polyvinyl alcohol (PVA) as a binder, and has a high critical temperature according to claims 1 to 22. Method for manufacturing superconducting materials. (24) Production of a superconducting material having a high critical temperature according to claim 23, characterized in that the solvent and binder are removed by heating to a temperature in the range of 400°C to 700°C in the atmosphere. Method. (25) A superconductor having a high critical temperature according to any one of claims 1 to 24, wherein the main sintering is performed in an atmosphere with an O_2 partial pressure of 5 to 2,500 atmospheres. Method of manufacturing the material. (26) A superconductor having a high critical temperature according to any one of claims 1 to 25, characterized in that preliminary sintering is performed in an atmosphere with an O_2 partial pressure of 5 to 2,500 atmospheres. Method of manufacturing the material. (27) A method for manufacturing a superconducting material having a high critical temperature according to any one of claims 1 to 26, characterized in that the sintered body after main sintering is heat-treated in a range of 500 to 800°C. . (28) O_2 partial pressure during heat treatment is 10^-^1Torr
A method for producing a superconducting material having a high critical temperature according to claim 27, characterized in that: (29) Immediately after the main sintering, or after the main sintering, the method is reheated to a temperature in the range of 500 to 800°C and then rapidly cooled. A method for producing a superconducting material having a high critical temperature as described in .