JPH07187671A - Oxide superconductor and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a 123 series superconductor of a rare earth element having a large ionic radius, the critical temperature of which is 90 K or higher,
Also, a superconductor having a large critical current and a method for manufacturing the same are provided. [Structure] When solidifying a 123-based superconductor containing at least one element of rare earth elements such as La, Nd, and Sm from a molten state, the oxygen partial pressure of the production atmosphere is set to 0.0000.
When controlled within the range of 1 to 0.1 atm, the critical temperature is 9
Superconductors exceeding 0K can be synthesized. Moreover, 1 inside
A phase having a composition slightly deviated from the composition of 23 is dispersed and acts as an effective pinning point, so that a superconductor having a high critical current can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxide superconductor having a high critical temperature and a high critical current and a method for manufacturing the oxide superconductor, and more particularly to a technique effectively applied to magnetic levitation, magnetic shield, superconducting bulk magnet and the like. is there.

[0002]

2. Description of the Related Art With the discovery of superconductors whose critical temperature exceeds liquid nitrogen temperature, superconducting applications have been studied worldwide. Among them, 123 represented by Y-Ba-Cu-O
For system materials, the development of melting methods such as MPMG
23 Fine Y ₂ BaCuO ₅ (2
11) It has succeeded in achieving a large critical current by dispersing the phases. Such a superconductor can generate a large electromagnetic force by interacting with a magnetic field,
Application research on bearings, flywheels, conveyors, etc. that utilize this force is becoming popular. For example, “Melt ProcessedHigh Temperature Superconducto
rs ”, ed. M. Murakami (World Scientific, 1993) and others.

Further, it has been clarified that a superconductor having a large critical current functions as a permanent magnet by shielding a strong magnetic field or conversely capturing a strong magnetic field. When considering such various applications, it is necessary to manufacture materials with crystal grains as large as possible, to increase the size by superconducting bonding, and to cope with complicated shapes by precision processing.

Since the oxide superconductor is a material having large anisotropy, it is important to control the crystal orientation. Furthermore, if a material having a larger critical current can be manufactured, it is possible to improve the generated electromagnetic force.

At present, a combination of a seed crystal and a temperature gradient is generally used as a method for controlling the crystal orientation and increasing the crystal size. At this time, as the seed crystal, for example, for growth of Y123 system, La, Nd, Sm1 having a higher melting point than that is used.
23 superconductors are used.

On the other hand, when considering the superconducting junction, Nd12
3 or Sm123 superconductor is produced and heated near the melting point of Y123 having a lower melting point, so that the Y123 phase is sandwiched between the Nd123 plates and Nd remains in the solid phase.
It is also conceivable to melt and join 3 together. For the above-mentioned applications, it is necessary to synthesize good quality Nd123, Sm123 superconductors.

[0007]

However, when these superconductors are manufactured by a commonly used sintering method or melting method, since the ionic radius of the rare earth element is large, they are easily replaced with Ba sites and the critical temperature is exceeded. However, there was a problem that For example, H. Uwe et al .: Physica
C vol.153-155 (1988) P.930-931 describes related technologies.

In addition, RE123 (RE: Y, Ho, E
In the r, Dr) -based superconductor, a high critical current is achieved by finely dispersing the 211 phase.
There is a limit to the pinning effect by the 11-phase, and research to pursue the possibility of other pinning points is also underway.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to replace Ba with a Ba in the synthesis of a 123-based oxide superconductor of a rare earth element having a large ionic radius as much as possible. It is an object of the present invention to provide a technique capable of suppressing and obtaining an oxide superconductor having a critical temperature exceeding 90K.

Another object of the present invention is to provide a technique capable of synthesizing a superconductor having a large critical current even in a high magnetic field.

[0011]

In order to achieve the above object, the present invention is characterized by the following configurations or methods.

(1) RE-Ba-Cu-O (RE is La,
In an oxide superconductor having a composition of Nd and Sm containing at least one element among rare earth elements), the RE: Ba: Cu ratio is 1: 2: 3 and the O ratio is 6.
The composition consisting of 8 to 7.2 was used as the mother phase, and RE: Ba:
The ratio of Cu is 1 + d: 2-d: 3 (0 <d <0.5) and O
The dispersed phase having a ratio of 6.8 to 7.2 is dispersed.

The above-mentioned oxide superconductor (1) is characterized in that the critical temperature exceeds 90K.

The oxide superconductor of (1) above is characterized in that the dispersed phase is contained in an amount of 1% or more and 30% or less.

The oxide superconductor of (1) is characterized in that the size of the dispersed phase is 5 μm or less.

(2) RE-Ba-Cu-O (RE is La,
Rd in an oxide superconductor having a composition of at least one element of rare earth elements of Nd and Sm)
A composition having an E: Ba: Cu ratio of 1: 2: 3 and an O ratio of 6.8 to 7.2 is used as a mother phase, and a RE: Ba: Cu ratio of 1 + d: 2-d: 3 ( 0 <d <0.5) and an O ratio of 6.8 to 7.2 and RE _4-x Ba _{2 + x} Cu ₃ O
_10-y phase (RE contains at least one element of La and Nd, and is in the range of 0 <x <0.2, 0 <y <0.5) phase and / or Sm ₂ BaCuO ₅ phase Is less than 50% and more than 0% (content> 0).

The oxide superconductor of (2) is characterized in that the critical temperature exceeds 90K.

The oxide superconductor of (2) is characterized in that the dispersed phase contains 1% or more and 30% or less.

The oxide superconductor of (2) is characterized in that the size of the dispersed phase is 5 μm or less.

(3) RE-Ba-Cu-O (RE is La,
In the melting process of the oxide superconductor having a composition of Nd and Sm containing at least one element in the rare earth elements), when the superconducting phase is solidified from the molten state, the oxygen partial pressure of the generation atmosphere is set to 0. It is characterized in that the process is performed within a range of 00001 atmospheric pressure to 0.1 atmospheric pressure.

The method for producing an oxide superconductor according to the above (3) is characterized in that the temperature in the molten state is 1000 to 1500 ° C.

The above-mentioned method (3) for producing an oxide superconductor is characterized in that the rate of solidification from a molten state is 10 ° C./hour or less.

The above-mentioned method (3) for producing an oxide superconductor is characterized in that when solidified from a molten state, the crystal is grown under a temperature gradient of 5 ° C./cm or more.

That is, the main technical idea of the present invention is as follows:
By controlling the atmosphere when the 23 phase is generated from the molten state,
As much as possible, RE (RE contains at least one element of rare earth elements such as La, Nd, Sm) and B
It is to suppress mutual substitution of a and obtain 123 crystals of good quality.

FIG. 1 is a ternary phase diagram of RE ₂ O ₃ —BaO—CuO of RE having a large ionic radius in the sample example shown in Table 1. In the present invention, as shown in FIG. 1, a solid solution region exists along a line extending from the 123 phase to the upper right. This solid solution region is displaced from the 123 phase in the air by RE _{1 + x} Ba _2-x Cu
_{This is because the 3} O _y (x> 0, 0.6 <y <7.2) phase becomes stable. However, this solid solution region differs depending on the type of RE. Further, in the case of Sm, it is not the 422 phase but the 211 phase, and there is no solid solution region. Eventually, RE having a large ionic radius indicates that this solid solution region is present and the critical temperature is greatly lowered when the treatment is performed in air.

FIG. 2 is a diagram for explaining that the stable region moves to the vicinity of the ternary phase diagram shown in FIG. 1 when the oxygen atmosphere is controlled to an appropriate range. As shown in the figure, the parent phase is the 123 phase, and RE _{1 + x} Ba _2-x Cu ₃ O _y (0 <x <0.5, 6.0 <
y <7.2) It shows that the dispersed phase is distributed in the matrix.

When La, Nd and Sm123 crystals are grown in normal air, as shown in FIG. 1, solid solution regions exist in RE and Ba, and they are mutually replaced, so that the critical temperature is greatly lowered. I will end up.

This is due to RE under the partial pressure of oxygen such as air.
RE _{1 + x} Ba _2-x Cu ₃ O _y (x> 0,
This is because 6.0 <y <7.2) is more stable. In order to solve this, in a sintering method or the like, a relatively good critical temperature is achieved by forming a superconductor in a nitrogen atmosphere and then oxidizing it (for example, T. Wada et a
l .: J. Am. Ceram. Soc., vol. 72. (1989) p. 2000-2003).

However, the transition width is wide and the zero resistance temperature is low. It is considered that this is because the sintering method is a solid-phase reaction, so that the solid solution region is inevitably affected, and mutually substituted phases are generated.

Therefore, in the method of solidifying from a molten state, if mutual substitution can be suppressed at the stage of nucleation and growth,
It is expected that a good quality RE123 phase can be synthesized.
Moreover, it has been reported that the 123 phase, which does not form a solid solution, becomes stable at a high temperature of 1050 ° C. or higher, and there is a possibility that a high-quality superconducting phase can be synthesized if it is synthesized by a melting process (for example, SIYoo & R.W.McCallum: Physica C vol.210 (1
933) P.147-156).

However, when the melting process was tried under various conditions, it was found that a good superconductor could not be easily obtained. Therefore, the present inventor made an attempt to control the oxygen partial pressure in order to suppress mutual substitution at the stage of nucleation and growth. This is because under low oxygen partial pressure, Ba substitution of divalent ions by RE which is trivalent ions is considered to be suppressed.

As a result of conducting experiments under various conditions, it was found that the oxygen partial pressure was in the range of 0.0001 atm to 0.1 atm.
It was revealed that this mutual substitution was suppressed and the RE123 phase became stable. This lower limit is that the superconducting phase itself is decomposed under extremely low oxygen partial pressure such as vacuum,
The upper limit is determined when the effect of reducing oxygen partial pressure is lost.

That is, according to the present invention, the atmosphere for growing crystals from the molten state is set to have an oxygen partial pressure within a certain range, so that even in a 123 series superconductor having a large RE radius, a 123 phase having a high critical temperature is used. Was successfully synthesized.

Further, in this process, RE: Ba:
RE _{1 + x} Ba with Cu ratio slightly deviated from 1: 2: 3
_{A 2-x} Cu ₃ O _y (x> 0,0.6 <y <7.2) phase is also formed at the same time, which is dispersed in the matrix and acts as a very effective pinning point. Became clear.

However, as for the size of the dispersed phase, the finer it is, the more effective it is as long as the contained amount is constant.
The crystal size of the phase is about 1 nm. On the other hand, when the thickness is 5 μm or more, the pinning effect becomes small and the substantial effect is lost. Further, when the content of the dispersed phase exceeds 30%, the solid solution region is widened, and the critical temperature of the superconductor itself becomes lower than 90K.

On the other hand, when the content of the dispersed phase is lower than 1%, the pinning effect becomes small and the substantial effect is lost.

Moreover, this dispersed phase acts as a pinning point in a wide magnetic field range. It is considered that this is because, as shown in FIG. 2, although the parent phase is located near 123, the crystal grows at a high temperature, and a statistical distribution is generated and dispersed in RE: Ba to some extent. These dispersed phase regions have slightly different characteristics such as critical temperature and critical magnetic field from the parent phase,
Under a strong magnetic field, superconductivity is broken and transitions to normal conduction. However, since the magnetic field that becomes normal becomes different depending on the degree of composition shift, it can act as a pinning point from low magnetic field to high magnetic field. As a result, a much higher irreversible magnetic field has been obtained as compared with the materials reported hitherto. This magnetic field is the upper limit that can be used by the superconductor, and is very important for practical use.

The present invention is also characterized by adjusting the atmosphere during crystal growth from the molten state, and can be applied to all so-called melting methods and also for growing a single crystal from the molten state. Therefore, the temperature of the molten state is 1
000 to 1500 ° C. The lower limit is the melting start temperature, and the upper limit is the upper limit that can be industrially provided as an existing electric furnace. However, RE1 with a large ion radius
In the solidification of the 23-based material, the range of 1200 ° C. or lower is preferable. This is because at 1200 ° C. or higher, the reaction with the supporting material is severe, the sample is contaminated, and the deviation from the initial composition becomes large.

The coagulation rate is required to be 10 ° C./hour (h) or less. This is because stable growth of the superconductor is difficult at a rate exceeding 10 ° C./hour (h). Further, the slower the solidification rate, the more advantageous for the growth of the superconductor, but in the existing control equipment, 0.1 ° C./hour (h) is the lower limit that can be set.

Further, although it is possible to produce a good quality superconductor even when a temperature gradient is not used during solidification, in order to obtain a large sample having a uniform crystal orientation, a temperature gradient of 5 ° C./cm or more is used. It is necessary to grow crystals. The larger this gradient is, the more advantageous it is for crystal growth. However, the upper limit is 100 ° C./cm in an electric furnace capable of large-scale crystal growth with existing equipment.

In the melting method, so-called 211 phase and 422 phase can be distributed in the matrix phase, but the pinning effect described above can be obtained even with such a structure. However, if the content of these phases exceeds 50%, the superconducting properties deteriorate. Therefore, it is preferable that these phases are contained at 50% or less and more than 0% (content ratio> 0).

Further, the 211 phase and the 422 phase have a crack suppressing effect, and if the phases are miniaturized, they are pinned by this phase as in the case of the Y-Ba-Cu-O based material produced by the MPMG method. It is possible to synergize the effects.

[0043]

According to the above-mentioned means, in the synthesis of 123 series oxide superconductor of rare earth element having a large ionic radius, Ba
Mutual substitution at the stage of nucleation and growth is suppressed at the time of substitution with, so that an oxide superconductor having a critical temperature of higher than 90 K can be provided.

Further, since the dispersed phase in which RE and Ba are slightly replaced is finely dispersed in the matrix and acts as a pinning point in a wide oxide superconductor, oxide superconductivity with a large critical current even in a high magnetic field. It can allow body synthesis.

[0045]

EXAMPLES Examples of the present invention will be described in detail below.

(Example 1) An oxide superconductor and a method for manufacturing the same according to Example 1 of the present invention will be described.

First, Nd ₂ O ₃ , BaCO ₃ , and CuO powders are mixed so that the ratio of Nd: Ba: Cu is 1: 2: 3. This is calcined at 900 ° C. for 24 hours, put in a platinum crucible, heated and melted at 1400 ° C. for 20 minutes, then sandwiched with a copper hammer and rapidly cooled. Quench the quench plate, 50 x 50 x 2
Mold to 0 mm ³ . Three such samples are prepared.
After heating these samples at 1120 ° C for 20 minutes, 1080 ° C
For 20 minutes, then 950 ℃ up to 1 ℃ / hour
Slowly cool at the speed of (h). At this time, the sample is in air (0.
The heat treatment was performed under an oxygen partial pressure of 21 atm), an oxygen partial pressure of 0.01 atm, and an oxygen partial pressure of 1 atm. Then, it was treated in oxygen at 1 atm at 500 ° C. for 100 hours.

FIG. 3 shows the temperature dependence of the magnetization of the obtained sample. Those treated in air or under an oxygen partial pressure of 1 atm have a low critical temperature and a wide transition width. On the other hand, it can be seen that the sample manufactured under the oxygen partial pressure of 0.01 atm of the present invention has a critical temperature of 90 K or higher, the transition width is very narrow, and is a high-quality superconductor.

When the critical current of this superconductor is measured with a sample vibrating magnetometer, a so-called peak effect as shown in FIG. 4 is observed, and a high critical current is obtained up to the high magnetic field side. . This suggests the existence of pinning points that act under high magnetic fields. As a pinning point of this kind, oxygen deficiency has been reported in Y-Ba-Cu-O-based materials, but in that case, a large change is shown under slight oxygen annealing conditions. However, in the sample of Example 1, such a change is not observed. this is,
It suggests that the pinning is not due to oxygen deficiency.

Further, the sample prepared in this Example 1 is the data of the Y-Ba-Cu-O based material prepared by the MPMG method showing the highest critical current so far (FIG. 5: N. Nakamura et al.
Al.Cryogenics vol.32 (1992), reprinted from p.949-953), a value exceeding that characteristic was obtained.

Further, several kinds of test pieces were cut out from a sample having a critical temperature of 90 K or higher and subjected to elemental analysis. As a result, the RE: Ba: Cu ratio was approximately 1: 2: 3.
It was found that O was distributed between 6.8 and 7.2.

(Embodiment 2) Next, an oxide superconductor and a method for manufacturing the same according to Embodiment 2 of the present invention will be described.

First, Nd ₂ O ₃ , BaCO ₃ , and CuO powders were mixed with Nd: Ba: Cu at a ratio of 1: 2: 3, 1.4: 2.
Mix so that it is 2: 3.2, 2.0: 2.5: 3.5,
Then, after the same manufacturing method as in Example 1 above, 108
Slow cooling from 0 ° C. is carried out in an oxygen partial pressure of 0.01 atm. In these samples, the Nd 422 phase is dispersed in the matrix as shown in FIG. 6 (photograph), but the zero resistance temperatures are 92K, 93K, and 91K, which are all good superconductors. It can be seen that is synthesized. The critical current densities are 8,000 and 850 at a temperature of 77K and a magnetic field of 3T, respectively.
It is 0,7500 amperes (A) / cm ² , which is higher than that of the Y-Ba-Cu-O material manufactured by the MPMG method shown in FIG. This shows that the pinning effect of the mother phase can be maintained even if the 422 phase exists. When these samples were subjected to oxygen annealing in oxygen at 1 atm at 500 ° C. for 100 hours (h), the critical temperature slightly increased, but further oxygen treatment caused a slight decrease. Therefore, although it is possible to change the critical temperature by changing the oxygen concentration, in the sample manufactured in this Example 2, if the O range is 6.8 to 7.2, the zero resistance temperature is Of more than 90K can be obtained.

(Embodiment 3) Next, an oxide superconductor of Embodiment 3 of the present invention and a method for manufacturing the same will be described.

First, Nd ₂ O ₃ , BaCO ₃ , and CuO powders were mixed so that the ratio of Nd: Ba: Cu was 1: 2: 3, and then the same process as in Example 1 was performed. ,
Slow cooling from 1080 ° C. is performed in an oxygen partial pressure of 0 atm to 0.2 atm. Table 1 shows the zero resistance temperature of these samples.
If the oxygen partial pressure exceeds 0.1 atm, the critical temperature will decrease.

[0056]

[Table 1]

(Embodiment 4) Next, an oxide superconductor of Embodiment 4 of the present invention and a method for manufacturing the same will be described.

First, as RE elements, La ₂ O ₃ and Sm _{2 are used.}
O ₃ powder was prepared and the ratio of RE: Ba: Cu was 1.2: 2.
The mixture was mixed so as to have a ratio of 1: 3.1, and after being manufactured in the same manner as in Example 1, the annealing start temperature was set to 11 each.
The temperature was set to 00 ° C. and 1060 ° C., and the mixture was gradually cooled to 900 ° C. at a rate of 1 ° C./hour (h) in air and an oxygen partial pressure of 0.01 atm. Then, after cooling to room temperature, 10 at 500 ° C.
Treated in oxygen at 1 atmosphere for 0 hours. The ones treated in air had zero resistance temperatures of 10 K and 50 K, respectively, but those treated under an oxygen partial pressure of 0.01 atm
It was 90K and 92K.

(Embodiment 5) Next, an oxide superconductor and a method for manufacturing the same according to Embodiment 5 of the present invention will be described.

First, Nd ₂ O ₃ , BaCO ₃ , and CuO powders were mixed so that the ratio of Nd: Ba: Cu was 1: 2: 3, and the same procedure as in Example 1 was performed. ,
Cooling from 1080 ℃ 10 ℃ / hour (h), 5 ℃ / hour
When carried out at a rate of (h), 0.1 ° C./hour (h), the zero resistance temperatures were 90 K, 90 K and 92 K, respectively.

Although it is possible to manufacture even at a cooling rate of 0.1 ° C./hour (h) or less, the existing control device cannot set a value lower than this value.

For cooling from 1080 ° C., set temperatures of 1050 ° C., 1020 ° C. and 990 ° C. are selected, and cooling is performed at 30 ° C./hour (h) between the set temperatures, and the holding time at each temperature is 20 hours. Even if (h) is set, the critical temperature is 91
The one of K is obtained. This indicates that a good quality superconductor can be obtained if the total cooling rate during solidification is 10 ° C./hour or less.

(Embodiment 6) Next, an oxide superconductor of Embodiment 6 of the present invention and a method for manufacturing the same will be described.

First, Nd ₂ O ₃ , BaCO ₃ and CuO powders were mixed so that the ratio of Nd: Ba: Cu was 1: 2: 3, and calcined at 950 ° C. for 24 hours (h), Diameter 2c
It is molded into a pellet having a height of m and a height of 1 cm. Place this in an electric furnace with an oxygen partial pressure of 0.01 atm at 1100 ° C for 1 hour.
(h) After heating, at a rate of 1080 ° C to 1 ° C / hour (h), 9
Slowly cool to 00 ° C. Then, it is left to cool to room temperature in the furnace. The zero resistance temperature of this sample was 95K.

Example 7 Next, an oxide superconductor of Example 7 of the present invention and a method for manufacturing the same will be described.

First, Nd ₂ O ₃ , BaCO ₃ , and CuO powders were mixed so that the ratio of Nd: Ba: Cu was 1: 2: 3, and calcined at 950 ° C. for 24 hours (h), Diameter 2c
It is molded into a pellet having a height of m and a height of 1 cm. This was placed in an electric furnace with a temperature gradient of oxygen partial pressure of 0.01 atm,
After heating at 0 ℃ for 1 hour (h), 1080 ℃ to 1 ℃ / hour
Gradually cool to 900 ° C at the rate of (h). At this time, 5 ° C./cm, 10 ° C./cm, and 100 ° C./cm were used as the temperature gradient. As a result, in all the samples, a zero resistance of 95K was obtained.

Further, as in Examples 1 to 6, it is possible to obtain a good quality superconductor without using a temperature gradient, but in order to obtain a large-sized sample with a uniform crystal orientation, A temperature gradient of 5 ° C / cm or more is required. Further, although a temperature gradient of 100 ° C./cm or more is possible, the control device used in the present invention could not obtain a value higher than this.

As described above, according to the above embodiment, when the oxygen partial pressure is controlled when the RE-Ba-Cu-O oxide superconductor is solidified from the molten state, the critical temperature and the critical current are high. An oxide superconductor can be obtained.

Although the present invention has been specifically described based on the embodiments above, it is needless to say that the present invention is not limited to the above embodiments and can be variously modified without departing from the scope of the invention. Absent.

[0070]

As described above, according to the present invention, in the synthesis of 123 series oxide superconductors of rare earth elements having a large ionic radius, mutual substitution with Ba is suppressed at the stage of nucleation growth. It is possible to provide an oxide superconductor having a critical temperature exceeding 90K.

Further, since the dispersed phase in which RE and Ba are slightly substituted is finely dispersed in the matrix and acts as a pinning point in a wide oxide superconductor, the oxide superconductor having a large critical current even in a high magnetic field. It can allow body synthesis.

[Brief description of drawings]

FIG. 1 is a RE of RE having a large ionic radius of the sample of the present invention.
_{It is a 2} O ₃ -BaO-CuO ternary phase diagram.

FIG. 2 is a diagram for explaining that the stable region moves to the vicinity of the ternary phase diagram when the oxygen atmosphere of the present invention is controlled within an appropriate range.

FIG. 3 is a diagram showing the temperature dependence of the magnetization of the sample of Example 1 of the present invention.

4 is a diagram showing the magnetic field dependence of the critical current of the sample of Example 1. FIG.

FIG. 5 is a diagram showing a magnetic field dependence of a critical current at a liquid nitrogen temperature of a Y—Ba—Cu—O oxide superconductor manufactured by an MPMG method which is one of conventional melting methods.

FIG. 6 is a structural micrograph of the Nd—Ba—Cu—O oxide superconductor synthesized in the region where the initial composition of the sample of this Example 1 contains 422 phase.

[Procedure amendment]

[Submission date] June 30, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a RE of RE having a large ionic radius of the sample of the present invention.
_{It is a 2} O ₃ -BaO-CuO ternary phase diagram.

FIG. 2 is a diagram for explaining that the stable region moves to the vicinity of the ternary phase diagram when the oxygen atmosphere of the present invention is controlled within an appropriate range.

FIG. 3 is a diagram showing the temperature dependence of the magnetization of the sample of Example 1 of the present invention.

4 is a diagram showing the magnetic field dependence of the critical current of the sample of Example 1. FIG.

FIG. 5 is a diagram showing a magnetic field dependence of a critical current at a liquid nitrogen temperature of a Y—Ba—Cu—O oxide superconductor manufactured by an MPMG method which is one of conventional melting methods.

FIG. 6 contains the initial composition of the sample of Example 1 with 422 phases.
Nd-Ba-Cu-O oxide synthesized in the region
It is a photograph of a crystal structure of a superconductor.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C04B 35/653 ZAA H01B 12/00 ZAA 13/00 565 D (71) Applicant 000003300 Tosoh Corporation Yamaguchi 4560 Kaisei-cho, Shinnanyo-ken, Japan (72) Inventor Masato Murakami 1-14-3 Shinonome, Koto-ku, Tokyo Inside Superconducting Engineering Laboratory, Center for International Superconducting Industrial Technology (72) Inventor Yousang Im Tokyo Koto, Tokyo 1-14-3 Shinonome Ward International Superconductivity Industrial Technology Research Center Superconductivity Engineering Laboratory (72) Inventor Naomi Sakai 1-14-3 Shinonome Koto Ward Tokyo International Superconductivity Industrial Technology Research Center Superconductivity Engineering In the laboratory (72) Inventor Hiroshi Takaichi 1-14-3 Shinonome, Koto-ku, Tokyo International Foundation Superconductivity Engineering Laboratory, Research Center for Conducting Industrial Technology (72) Inventor Akimitsu Higuchi, 1-14-3 Shinonome, Koto-ku, Tokyo Metropolitan Institute of Technology for International Superconductivity Engineering (72) Inventor Shoji Tanaka Tokyo 1-14-3 Shinonome, Koto-ku, Tokyo Superconductivity Engineering Research Center, International Superconductivity Technology Center

Claims (12)

[Claims] 1. RE-Ba-Cu-O (RE is La, N
d, Sm containing at least one element in the rare earth elements)), the oxide superconductor having the composition
A composition having a RE: Ba: Cu ratio of 1: 2: 3 and an O ratio of 6.8 to 7.2 is used as a mother phase, and RE: Ba: Cu is used.
The oxide superconductor is characterized in that a dispersed phase having a ratio of 1 + d: 2-d: 3 (0 <d <0.5) and an O ratio of 6.8 to 7.2 is dispersed. 2. The oxide superconductor according to claim 1, wherein the critical temperature exceeds 90K. 3. The oxide superconductor according to claim 1, wherein the dispersed phase contains 1% or more and 30% or less. 4. The oxide superconductor according to claim 1, wherein the dispersed phase has a size of 5 μm or less. 5. RE-Ba-Cu-O (RE is La, N
d, Sm containing at least one element in the rare earth elements)), the oxide superconductor having the composition
A composition having a RE: Ba: Cu ratio of 1: 2: 3 and an O ratio of 6.8 to 7.2 is used as a mother phase, and RE: Ba: Cu is used.
Phase of 1 + d: 2-d: 3 (0 <d <0.5) and O ratio of 6.8 to 7.2, and RE _4-x Ba _{2 + x} Cu ₃ O.
_10-y (RE contains at least one element of La and Nd, and is in the range of 0 <x <0.2, 0 <y <0.5)
Phase and / or Sm ₂ BaCuO ₅ phase is 50% or less and 0%
An oxide superconductor characterized by being contained in a larger amount (content ratio> 0). 6. The oxide superconductor according to claim 5, wherein the critical temperature exceeds 90K. 7. The oxide superconductor according to claim 5, wherein the dispersed phase contains 1% or more and 30% or less. 8. The oxide superconductor according to claim 5, wherein the size of the dispersed phase is 5 μm or less and is larger than zero (>).
0) An oxide superconductor characterized by being present. 9. RE-Ba-Cu-O (RE is La, N
In the melting process of the oxide superconductor having a composition of (d, Sm containing at least one element in the rare earth elements), when the superconducting phase is solidified from the molten state, the oxygen partial pressure of the generated atmosphere is set to 0. A method for producing an oxide superconductor, which is performed in a range of 00001 atmospheric pressure to 0.1 atmospheric pressure. 10. The method for producing an oxide superconductor according to claim 7, wherein the temperature of the molten state is 1000 to 150.
A method for producing an oxide superconductor, characterized in that the temperature is 0 ° C. 11. The method for producing an oxide superconductor according to claim 7, wherein a rate of solidifying from a molten state is 10 ° C.
/ Hour or less, a method for producing an oxide superconductor. 12. The method for producing an oxide superconductor according to claim 7, wherein when the molten state is solidified, 5 ° C. /
A method for producing an oxide superconductor, which comprises growing a crystal under a temperature gradient of cm or more.