JPH013061A - 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 and radio 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. In addition, in the field of transportation equipment, it is used as a power source for magnetic levitation trains, electromagnetic propulsion ships, etc.
Furthermore, in the measurement and medical fields, 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 a quantum effect, can be 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 gap 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, a group of materials having an A-15 type crystal structure have a relatively high T. (superconducting critical temperature), but Nb3 is said to have the highest Tc.
T in Ge as well. remains at 23.2 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,
Temperature TcF at which the phase transition of a substance ends and the electrical resistance becomes zero
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. Additionally, helium is a substance that is naturally present in small amounts, and some estimates suggest that it will be depleted in the late 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 affected 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 Hc
2, 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 1lJa
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 the already reported example, [La, Ba) 2['
2N- such as uOs or [La, Sr]2cuOs
iF type oxides, which are considered to have a crystal structure similar to perovskite type superconducting oxides. These materials have been observed to have significantly higher Tc of 30 to 50 than conventional ones, and even Tc of 70 or more. 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 present invention is to obtain a high T. and 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 start temperature or critical temperature of a superconducting material is Tc1, and the phase transition end temperature at which the electrical resistance of the material becomes completely zero is T. The difference between P% Tc and TCP is expressed as ΔT.

Means for Solving the Problems The present inventors conducted various experiments to improve superconducting properties based on the assumption that superconductivity in Ba-La-Cu-0-based superconducting materials is mainly caused by substances at grain boundaries. ,
As a result of repeated investigations, they succeeded in producing a material that has 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, La, [u oxides, carbonates,
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, which is formed by main sintering at a temperature in the range of (the melting point of the 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. 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.

Further, by adding the preferable jB FJ of the present invention, the obtained sintered superconducting material is expressed by the following formula, (ea
t-x t, a,) Cu, Oz (however, xSy is 0
(~1 real number, 2 is 1~11 real number) Ba, La, Cu oxides, A superconducting material is produced by mixing carbonate, sulfate, or nitrate powders and sintering the mixed powder.

Furthermore, according to the preferred lI% of the present invention, ■,:<b,
Ta, Mo, WXTi, Cr, ! , ln, G
a, In, Cd, Sn, TI.

A powder of an oxide, carbonate, sulfate or nitrate of at least one element selected from the group consisting of Pb and ln is added to the mixed powder to further reduce the crystal grain size of the sintered body and increase the critical temperature. . These V, Nb, TalM
o, W, T+, CrSMn, Ga, In, C
d, Sn.

It is preferable that the atomic ratio of Cu to at least one element selected from the group consisting of T1, Pb, and Zn is A4.

Further, according to the eighth preferred embodiment of the present invention, the preliminary sintering is performed in the seventh preferred embodiment.
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.
by a ball mill using l2O3 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.

Further, 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 and 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 (P
VB) as a binder, dibutyl phthalate (DB
P) 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, the superconducting critical temperature Tc can be significantly improved by performing preliminary sintering and/or main sintering in an oxygen snow atmosphere with a partial pressure of 5 to 2,500 atmospheres. .

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 superconducting critical temperature can be increased by reheating immediately after sintering or after sintering to a temperature in the range of 500 to 800° C., and rapidly cooling it to create a finer crystal structure.

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 TCP 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 this 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 subjected to main sintering is refined. is preferred.

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 solid 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.

Further, in a preferred method of the present invention, the obtained sintered superconducting material is represented by the following general formula, (Ba 1 HLaj
CuyOz (However, X%V is a real number from 0 to 1, 2 is a real number from 0 to 4) , Mixing Cu oxide, carbonate, sulfate or nitrate powder. Ba:La:Cu
When the raw material powder is mixed with an atomic ratio outside of the above range,
The desired perovskite or pseudo-perovskite oxide cannot be changed. Furthermore, V, Nb,
Ta, Mo5WSTi, Cr, Mn, Ga,
In5Cd.

It is preferable to reduce the grain size of the sintered body by adding powder of oxide, carbonate, sulfate or nitrate of one or more elements of 5nSTl, pb or 2n.
When the atomic ratio of these elements to Cu is lower than the range of 0.01 to 0.15, no effect of addition can be obtained;
When it is higher than the range of 1 to 0.15, the effect of addition is saturated or the desired perovskite type or pseudo-perovskite type oxide cannot be obtained. These VSNb, Ta
, ! Jo, W, Ti, CrSMn, Ga5In.

By adding one or more elements of Cd, 5nSTl, 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 in an oxygen atmosphere under reduced pressure. That is, by this heat treatment under a low oxygen partial pressure, oxygen atoms are stripped 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,
Since ΔT is further improved by 3 to 5° C., higher TCP can be obtained. The heat treatment is preferably performed under reduced oxygen pressure of 10-'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. This is because it is difficult to obtain a sufficiently high TCP.

Furthermore, according to a preferred embodiment of the present invention, the superconducting critical temperature can be further increased 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 inventors have determined that the thickness from the surface to the center is 1 mm.
Hereinafter, it has been discovered that when the thickness is preferably 0.5 mm, the entire ceramic has excellent superconducting properties, that is, it consists of a structure with a low superconducting critical temperature. Because it is thin, the reaction with the atmosphere during sintering or heat treatment favors superconducting properties, and the surface area of the ceramic is subject to oxygen defects and/or strain effects, resulting in excellent superconducting properties. Conceivable.

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. It is preferable to do so.

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 BaC0, La2O3, and CuO with a purity of 3N or higher was prepared in a Ba:L ratio of 0.93:0.07:t, o.
They were mixed to have an atomic ratio of a: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 atmosphere at 870° 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 is almost completely dissolved, and in the pulverization process before the final firing, the first
A powder having the average particle size shown in the table was obtained. Each of the powders obtained as described above was filled into a rubber mold, and the amount was 1 ton/cn.
Static pressure molding was performed at a pressure of f to obtain a bulk molded product of 30φ×5Qaun.

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 at 900° C. for 10 hours in the atmosphere 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.

In addition, the critical temperature Tc and T. The measurement of F was carried out by attaching electrodes with Ag conductive paste to both ends of the sample according to a standard method, and using a DC four-point probe method in a taliostat. Temperature was measured using a calibrated Au (Fe)-Ag thermocouple. Changes in resistance were observed while increasing the temperature little by little. In addition, Table 1 also lists the difference ΔT from TC(!:TCF).

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 BaCO3,1 with a purity of 3N or more and an average particle size of 6 μm or less,
A203, Cub, V2O5 or Ta, Os powder after firing Ba, La5Cu, V or Ta
The atomic ratio of is 0.93:0.07:1.0:0.04
Or, they were mixed in a ratio of 0.7: 0.3: 0.6: 0.05. This mixed powder is mixed with Al2 using air as a medium.
The particles were injected and collided with an O3 target to obtain an average particle size of 3 μm. The obtained mixed powder was heated with N2 with a partial pressure of 1 atm.
It was fired at 860°C for 12 hours in a -0° mixed gas atmosphere. The cake-like solidified powder was further ground to 2 μm using a jet mill similar to the above. This process was repeated three times. During molding, this powder is processed into PVE (polyvinyl butiere) using a solvent mainly consisting of toluene.
was kneaded as a binder, DBP (gobutyl phthalate) was added as a plasticizer, and after doctor blade molding,
It was cut into m+u width pieces and the binder was removed at 600°C in the air.

Each of the above molded bodies was heated in a 02M atmosphere of 100 atm.
It was sintered by holding at 90° C. for 5 hours to obtain a sintered body.

In addition, the critical temperature T. and T. The measurements were carried out using a DC four-point probe method in a Talainestat by attaching electrodes with Ag conductive paste 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.

The Tc of the sintered body containing ■ is 128, and the Tcp is 12.
5, and on the other hand, T of the sintered body containing Ta. is 12
6KXTcF was at 122.

Further, when the same material was measured under the same conditions after 3 weeks, the change in Tc was within ±1°, and no significant change was observed.

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, Nb, Ta, Mo5WSTiSCr
SGaSIn.

By adding Cd5Sn, Tl, Pb, or Zn, a finer crystal structure can be obtained, and a higher Tc can be obtained. In addition, T by sintering in an 02 atmosphere of 5 to 2500 atm. can be significantly improved.

Furthermore, by manufacturing with a thickness from the surface to the center of 1 mm or less, preferably 0.5 mm or less according to a preferred embodiment of the present invention, uniformity in oxygen defect concentration is achieved.
This results in a small ΔT and a high T'c+'.

Since such a high and stable T 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 La 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) High critical temperature according to claim 1, characterized in that each of the Ba, La, Cu, oxide, carbonate, sulfate, or nitrate powder 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, La, 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_−_xLa_x)Cu_yO_z (where x and y are real numbers from 0 to 1, and z is a real number from 0 to 4) x, A patent characterized in that powders of Ba, La, and Cu oxides, carbonates, sulfates, or nitrates are mixed so that y is 0.5 to 0.95 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. (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. A method for producing 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. A method for producing 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 above.