JP3206033B2 - Oxide superconductor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nuclear fusion reactor, a magnetic fluid generator, a particle accelerator, a rotating electric device (such as a motor or a generator), a magnetic separator, a maglev train, a maglev vehicle, a maglev elevator, It is suitable as a material for magnet coils in nuclear magnetic resonance tomography diagnostic equipment, magnetic propulsion ships, electron beam exposure equipment, single crystal manufacturing equipment, various experimental equipment, etc.It is also suitable for power transmission lines, electric energy storage, transformers, rectifiers, etc. Suitable for applications where power loss is a problem, and further suitable for various elements such as Josephson elements, SQUID elements, magnetic sensor elements, superconducting transistors, superconducting microwave three-dimensional circuits, and infrared detecting materials, magnetic shielding materials, etc. The present invention relates to an oxide superconductor suitable as various functional materials.

[0002]

2. Description of the Related Art Superconducting materials are often put into practical use in the form of thin films or wires, but at that time, they are usually used integrally with a substrate or reinforcing material. Therefore, as a superconductor material, its superconducting transition temperature (T
c) It has excellent superconducting properties such as critical current density (Jc), and, from the viewpoint of practicality, does not degrade the properties of the substrate and the reinforcing material when integrated with the substrate and the reinforcing material. It is preferable that the material can be synthesized by:

[0003] Among various superconductors, an oxide superconductor contains oxygen in its crystal structure, and therefore, most of them are synthesized in a relatively high-concentration oxygen atmosphere.
Therefore, for example, when the substrate or the reinforcing material is made of an easily oxidizable material such as a carbonaceous material, if an attempt is made to integrate the oxide superconductor therewith, the above-mentioned process will take place during the synthesis of the oxide superconductor. The substrate and the reinforcing material are oxidized to cause deterioration of the strength, and a problem arises that the substrate and the reinforcing material cannot be used in actual use.

[0004] Even with the same oxide superconductor, for example, RJ Cava et al., "Nature", vol. 336 (1988) 211
Pb ₂ Sr ₂ Ca _1-x Y _x Cu ₃ O ₈
(0 ≦ x ≦ 0.5) is known to be an oxide superconductor that can be synthesized in an inert atmosphere or a very low-concentration oxygen atmosphere. Therefore, in the case of this oxide superconductor, there is an advantage that the oxide superconductor can be integrated with the substrate and the reinforcing material without causing the characteristic deterioration. However, on the other hand, the Tc of this oxide superconductor is as low as about 80K, and there is a problem in practical use.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a Ca
Solving the above-mentioned problems in the oxide superconductor having the composition disclosed by Va et al., it can be synthesized in an inert atmosphere or an extremely low-concentration oxygen atmosphere, and has a Tc of 100 to 107K. An object is to provide an oxide superconductor having a high value.

[0006]

To achieve the above object, according to the solution to ## in the present invention, first, the following _{formula: (Pb 1-p Bi p} ) 2 Sr 2 (Ca 1-q A q) 2 Cu 4 O _r (1) (where A is Y, La, Nd, Sm, Eu, Gd, D
represents at least one element selected from the group consisting of y, Ho, Er, Tm, Yb, and Lu, and p, q, and r each represent 0
<P ≦ 0.4, 0.15 ≦ q ≦ 0.25, 9.5 ≦ r ≦
An oxide superconductor comprising, as a main component, a copper composite oxide represented by a number satisfying 10.65). Hereinafter, this is referred to as a first invention.

Further, in the present invention has the _{formula: (Pb 1-p Tl p} ) 2 Sr 2 (Ca 1-q A q) 2 Cu 4 O r ...... (2) ( In the formula, A, Y , La, Nd, Sm, Eu, Gd, D
represents at least one element selected from the group consisting of y, Ho, Er, Tm, Yb, and Lu, and p, q, and r each represent 0
<P ≦ 0.6, 0.15 ≦ q ≦ 0.25, 9.5 ≦ r ≦
An oxide superconductor comprising, as a main component, a copper composite oxide represented by a number satisfying 11.05). Hereinafter, this is referred to as a second invention.

[0008] In a copper composite oxide superconductor, the CuO ₂ layer formed in the crystal structure exhibits superconducting properties. Then, as the number of the CuO ₂ layers present in the unit crystal structure increases, Tc shifts to a higher temperature side. In the case of the copper composite oxide described by Cava et al., The number of CuO ₂ layers present in the unit crystal structure is two.

On the other hand, in each of the first and second inventions, the C
The number of uO ₂ layers is three. That is, CuO in the unit crystal structure is compared with the copper composite oxide disclosed by Cava et al.
_Two layers are one layer more, and therefore, Tc also shows a higher value.
In the copper composite oxide according to the first aspect of the present invention, in order to form one more CuO ₂ layer having a valency of -2 in the unit crystal structure, +
Divalent Ca is introduced. And Pb in the unit crystal structure
By substituting a part of Pb of the O layer with Bi + 3 to make the charge of the entire PbO layer positive, it becomes possible to introduce the Ca described above. The formation of a CuO ₂ layer is realized.

In this case, the replacement amount of Bi with respect to Pb is 0.
If it exceeds 4, that is, if p in the above formula (1) is larger than 0.4, it becomes difficult to grow a crystal as a bulk body. Therefore, the substitution amount p of Bi is 0 <p ≦ 0.4. To When the p value is within the above range, the amount of Ca that can be introduced into the unit crystal structure: (1-q) is 0 to 0.70.

That is, 0 <p ≦ 0.4, 0.15 ≦ q ≦
When the ratio is 0.25 , a copper composite oxide having three CuO ₂ layers in the unit crystal structure can be synthesized. on the other hand,
The same applies to the case of the copper composite oxide in the second invention, and PbO
By substituting a part of the layer Pb with Tl of +3 valence to realize a state in which Ca can be introduced with the total charge of the PbO layer being positive, three CuO ₂ layers are formed in the unit crystal structure. is there.

In this case, the substitution amount of Tl can be up to 0.6. When this value, that is, the p value in the equation (2) is set to 0.
If the value is larger than 6, the crystal growth as a bulk body becomes difficult as in the case of the copper composite oxide of the formula (1). Therefore, the p value is set to 0 < p ≦ 0.6. (2) can and p value falls within the above range in the formula, ie, 0 <p ≦ 0.
6 , when 0.15 ≦ q ≦ 0.25 , the CuO ₂ layer
One can be formed.

[0013] First, one of the copper composite oxide of the second invention
Even when p = 0 and q = 0 , the index r of oxygen is 10.0 when it has an ideally synthesized ideal crystal structure. However, due to the influence of the amount of Bi or Tl that partially substitutes for Pb or the amount of oxygen in the atmosphere at the time of synthesis, the amount of oxygen in the crystal structure becomes excessive or deficient. , 10.0
Value slightly deviated from

In the copper composite oxide according to the first aspect of the present invention, the r value is allowed to be in the range of 9.5 ≦ r ≦ 10.65. When r is smaller than 9.5, it becomes difficult to form three CuO ₂ layers in this unit crystal structure, which causes a decrease in Tc. When r is larger than 10.65, the bulk becomes smaller. This is because crystal growth as a body does not proceed sufficiently.

In the case of the copper composite oxide of the second invention, the r value is in the range of 9.5 ≦ r ≦ 11.05 for the same reason as in the case of the copper composite oxide of the first invention. Is acceptable. Oxide superconductor of the present invention, a tape-like, linear, fiber, sheet, etc., it is a this used in the various forms. Further, it can also be used by forming it on a reinforcing wire made of carbon fiber, ceramics, or a metal such as gold or silver. Further, it can also be used by filling in a hollow material for reinforcement such as a silver sheath. Furthermore, a superconducting wire having a multi-core wire structure can be formed by using a matrix such as copper. Also, Si, MgO, LaGaO ₃ , LaAlO ₃ ,
It can be formed as a thin film on a substrate such as SrTiO ₃ and used as various elements or as LSI wiring.

The oxide superconductor of the present invention can be synthesized by various methods. Among these methods, the solid-phase reaction method using a powder such as an oxide or a carbonate as a raw material is one of the methods. Therefore, there is a problem that a stable intermediate product is easily formed. As a synthesis method, physical vapor deposition methods such as laser ablation method, molecular beam epitaxy method, electron beam evaporation method, and various sputtering methods, which can form each atomic layer finely in an atomic order, can be formed. It is suitable.

For example, the synthesis by the laser ablation method will be described with reference to the synthesis of the copper composite oxide of the formula (1) as an example. In this case, PbO, Bi ₂ O ₃ , SrCO
_3. Each raw material powder of CuO is (Pb + Bi): Sr: Cu
Is 2: 2: 2.2 and 0 <Bi / Pb
After weighing and mixing so as to satisfy ≤ 2/3, and molding the mixed powder into pellets, the molded body is fired at a temperature of 700 to 850 ° C for 1 to 12 hours in a nitrogen atmosphere.
If the firing temperature at this time is lower than 700 ° C., the synthesis reaction may not proceed sufficiently, and if firing at a temperature higher than 850 ° C., the whole may be dissolved. Also,
If the firing time is shorter than 1 hour, the synthesis reaction may not proceed sufficiently.
It is useless as a synthesis reaction, and only increases the production time.

Next, the fired body is weighed, and the Pb amount is calculated from the measured weight based on the composition ratio of the fired body.
The PbO powder corresponding to the Pb amount of 0 to 5 times the b amount is weighed. Then, the weighed PbO is added to a powder obtained by pulverizing the fired body, mixed, and then molded. This compact is referred to as target I. During the production of the target I, the powder of the fired body was added to the powder of Pb having a stoichiometry or more of
The reason for adding O powder is to prevent the problem that, when a copper composite oxide described later is synthesized on a desired substrate, the deposition of the Pb component becomes difficult and the target composition becomes difficult to obtain as the substrate temperature increases. That's why. However, the added Pb
If the amount of O exceeds the amount corresponding to five times the calculated amount of Pb, it becomes difficult to adjust the composition ratio of the target copper composite oxide at the substrate temperature. -ing

Next, the raw material powders of CaCO ₃ , oxides or carbonates of A, and CuO were mixed with a (Ca + A): Cu molar ratio of 1: 1 and 0 <A / Ca ≦ 1/3. After weighing and mixing so as to fill the mixture and molding the mixed powder into a pellet, the molded body is heated to a temperature of 800 to 9 in the atmosphere.
Bake at 50 ° C for 6 to 12 hours. Firing temperature at this time,
The firing time is set in each of the above ranges for the same reason as in the synthesis of the target I described above.

Then, after the obtained fired body is pulverized,
Form again. This compact is designated as target II. The targets I and II are set separately on the rotary target holder of the vacuum chamber, and a substrate is set at a position facing each of these targets at a distance of 20 to 150 mm from each target to reduce the oxygen partial pressure in the vacuum chamber. 5x1
0 ^{-3 to} 5 × 10 ^-4 mbar, and the substrate is 450 to 70
Heat to a temperature of 0 ° C. The target holder is rotated and the target I and the target II are alternately irradiated with excimer laser to deposit each target material on the substrate. As the excimer laser at this time, for example, ArF,
Those using KrF and XeCl are preferable.

The switching of the target is performed by RHEED
The monitoring is carried out while monitoring the intensity of the vibration, and when the intensity Peter by each target is recognized, another target is irradiated with an excimer laser, and the target is switched in the order of target I → target II → target I →. . In the above laser ablation method,
If the distance between the target and the substrate is less than 20 mm, the substrate becomes obstructive, and the irradiation angle of the excimer laser on the target must be made extremely small, thereby making it difficult for ablation of the target to occur. Would. On the other hand, if the distance between the target and the substrate is larger than 150 mm, the deposition rate of the target material on the substrate is significantly reduced, and the time required for the synthesis becomes extremely long, which is not practical.

When the temperature of the substrate is lower than 450 ° C.,
The crystallization of the target material deposited on the substrate is less likely to occur, and when the temperature is higher than 700 ° C., the material deposited on the substrate re-evaporates. It will shift significantly. further,
When the oxygen partial pressure in the vacuum chamber is higher than 5 × 10 ⁻³ mbar , impurities are mixed in the copper composite oxide deposited on the substrate.
When it becomes easy to enter and when it is lower than 5 × 10 ⁻⁴ mbar, the oxygen uptake amount of the copper composite oxide deposited on the substrate becomes
Less .

When the copper composite oxide of the second invention is synthesized by the laser ablation method, the same method and conditions as described above are applied. In this case, in the production of the target I used for the synthesis of the copper composite product of the first invention, P
Each raw material powder of bO, Tl ₂ O ₃ , SrCO ₃ , and CuO has a (Pb + Tl): Sr: Cu molar ratio of 2: 2: 2.2 and satisfies 0 <Tl / Pb ≦ 1.5. To prepare a pellet-shaped molded body by weighing and mixing, and after calcination of the molded body, calculate the weight of Pb + Tl, and obtain an amount of PbO powder equivalent to 0 to 5 times the calculated amount. The Tl ₂ O ₃ powder may be produced in the same manner as in the first invention except that the Tl ₂ O ₃ powder is added to the powder of the fired body.

[0024]

【Example】

Example 1 Each powder of PbO, Bi ₂ O ₃ , SrCO ₃ and CuO was
The molar ratio of b: Bi: Sr: Cu is 1.7: 0.3: 2: 2.2
After weighing and mixing the four powders into a pellet, the compact was fired at 800 ° C. for 8 hours in a nitrogen stream.

The weight of the fired body was weighed, and the amount of Pb was calculated. This fired body was pulverized, and the calculated Pb amount was 2
PbO powder corresponding to twice the amount of Pb was added. The obtained mixed powder was molded and used as a target I. CaCO ₃ ,
Each powder of La ₂ (CO ₃ ) ₃ .xH ₂ O and CuO was converted to Ca: L
a: Cu is weighed so that the molar ratio of Cu is 0.75: 0.25: 1.1, and the three components are mixed, and the mixed powder is formed into a pellet. 1 at 900 ° C
It was baked for 0 hours. The fired body was pulverized and formed again to obtain a target II.

The targets I and II were separately set on a rotary target holder in a vacuum chamber, and a MgO substrate was placed at a position 50 mm away from these targets and the partial pressure of oxygen in the vacuum chamber was reduced to 1 × 10 2. ^-3 mb
The substrate temperature was kept at 550 ° C. in the state of ar. The target holder is rotated, and an ArF excimer laser is applied to each target, and while monitoring the intensity of the RHEED vibration, target I → target II → target I →...
Each target was irradiated by switching between and targets.

A thin film having a thickness of about 100 nm was obtained on the substrate. The overall composition of this thin film is Pb _1.7 Bi _0.3 S
r ₂ Ca _1.5 La _0.5 Cu ₄ O _10.4 , and the crystal structure analyzed by four-axis X-ray diffraction was as shown in FIG. The Tc of this thin film was 101K. Example 2 A target I having the same composition was manufactured in the same manner as in Example 1.

The powders of CaCO ₃ , Y ₂ O ₃ , and CuO are weighed so that the molar ratio of Ca: Y: Cu is 0.85: 0.15: 1.1, and the three are mixed. After the mixed powder is formed into a pellet, the formed body is subjected to 9
It was baked at 00 ° C. for 10 hours. The fired body was pulverized and formed again to obtain a target II. Using these targets, a thin film having a thickness of about 100 nm was formed on a LaAlO ₃ substrate under the same conditions as in Example 1.

The overall composition of this thin film is Pb _1.7 Bi _0.3
The crystal structure was Sr ₂ Ca _1.7 Y _0.3 Cu ₄ O _10.3 , and the crystal structure analyzed by four-axis X-ray diffraction method was such that La was replaced by Y in FIG. In addition, the T
c was 100K. Example 3 A target I having the same composition was produced in the same manner as in Example 1.

CaCO ₃ , Nd ₂ (CO ₃ ) ₃ .xH ₂ O,
Each powder of CuO has a molar ratio of Ca: Nd: Cu of 0.80:
The mixture was weighed so that the ratio became 0.20: 1.1, and the three components were mixed. The mixed powder was formed into a pellet, and the formed body was fired at 900 ° C. for 10 hours in the atmosphere. The fired body was pulverized and formed again to obtain a target II. Using these targets, LaG under the same conditions as in Example 1.
A thin film having a thickness of about 100 nm was formed on an aO ₃ substrate.

The overall composition of this thin film is Pb _1.7 Bi _0.3
Sr ₂ Ca _1.6 Nd _0.4 Cu ₄ O _10.4 , and the crystal structure analyzed by the 4-axis X-ray diffraction method is La in FIG.
Was substituted with Nd. The Tc of this thin film was 102K. Example 4 A target I having the same composition was produced in the same manner as in Example 1.

CaCO ₃ , Sm ₂ (CO ₃ ) ₃ .xH ₂ O,
Each powder of CuO was prepared by adding a Ca: Sm: Cu molar ratio of 0.7.
5: 0.25: 1.1 were weighed, and the three powders were mixed. The mixed powder was formed into pellets, and the formed body was fired at 900 ° C. in the air for 10 hours. The fired body was pulverized and formed again to obtain a target II.
Using these targets, a thin film having a thickness of about 100 nm was formed on a SrTiO ₃ substrate under the same conditions as in Example 1.

The overall composition of this thin film is Pb _1.7 Bi _0.3
Sr ₂ Ca _1.5 Sm _0.5 Cu ₄ O _10.4 , and the crystal structure analyzed by the 4-axis X-ray diffraction method is La in FIG.
Was replaced with Sm. The Tc of this thin film was 100K. Example 5 A target I having the same composition was produced in the same manner as in Example 1.

Each powder of CaCO ₃ , Eu ₂ O ₃ , and CuO was prepared by mixing a Ca: Eu: Cu molar ratio of 0.80: 0.20: 1.
After being weighed so as to be 1 and mixing the three components, the mixed powder was formed into pellets, and the formed body was fired at 900 ° C. for 10 hours in the air. This fired body is crushed,
It was molded again to obtain Target II. Using these targets, a thin film having a thickness of about 100 nm was formed on a Si substrate under the same conditions as in Example 1.

The overall composition of this thin film is Pb _1.7 Bi _0.3
Sr ₂ Ca _1.6 Eu _0.4 Cu ₄ O _10.4 , and the crystal structure analyzed by the 4-axis X-ray diffraction method is La in FIG.
Was replaced with Eu. The Tc of this thin film was 101K. Example 6 A target I having the same composition was produced in the same manner as in Example 1.

Each powder of CaCO ₃ , Gd ₂ O ₃ , and CuO was mixed with a Ca: Gd: Cu molar ratio of 0.80: 0.20: 1.
After being weighed so as to be 1 and mixing the three components, the mixed powder was formed into pellets, and the formed body was fired at 900 ° C. for 10 hours in the air. This fired body is crushed,
It was molded again to obtain Target II. Using these targets, a thin film having a thickness of about 100 nm was formed on an MgO substrate under the same conditions as in Example 1.

The overall composition of this thin film is Pb _1.7 Bi _0.3
Sr ₂ Ca _1.6 Gd _0.4 Cu ₄ O _10.4 , and the crystal structure analyzed by the 4-axis X-ray diffraction method is La in FIG.
Was substituted with Gd. The Tc of this thin film was 101K. Example 7 A target I having the same composition was produced in the same manner as in Example 1.

The powders of CaCO ₃ , Dy ₂ O ₃ , and CuO were mixed at a molar ratio of Ca: Dy: Cu of 0.85: 0.15: 1.
After being weighed so as to be 1 and mixing the three components, the mixed powder was formed into pellets, and the formed body was fired at 900 ° C. for 10 hours in the air. This fired body is crushed,
It was molded again to obtain Target II. Using these targets, a thin film having a thickness of about 100 nm was formed on a LaAlO ₃ substrate under the same conditions as in Example 1.

The overall composition of this thin film is Pb _1.7 Bi _0.3
Sr ₂ Ca _1.7 Dy _0.3 Cu ₄ O _10.3 , and the crystal structure analyzed by the 4-axis X-ray diffraction method is La in FIG.
Was substituted with Dy. The Tc of this thin film was 100K. Example 8 A target I having the same composition was produced in the same manner as in Example 1.

The powders of CaCO ₃ , Ho ₂ O ₃ , and CuO were mixed at a molar ratio of Ca: Ho: Cu of 0.85: 0.15: 1.
After being weighed so as to be 1 and mixing the three components, the mixed powder was formed into pellets, and the formed body was fired at 900 ° C. for 10 hours in the air. This fired body is crushed,
It was molded again to obtain Target II. Using these targets, a thin film having a thickness of about 100 nm was formed on a LaGaO ₃ substrate under the same conditions as in Example 1.

The overall composition of this thin film is Pb _1.7 Bi _0.3
Sr ₂ Ca _1.7 Ho _0.3 Cu ₄ O _10.3 , and the crystal structure analyzed by the 4-axis X-ray diffraction method is La in FIG.
Was replaced with Ho. The Tc of this thin film was 101K. Example 9 A target I having the same composition was manufactured in the same manner as in Example 1.

Each powder of CaCO ₃ , Er ₂ O ₃ , and CuO was mixed with a molar ratio of Ca: Er: Cu of 0.85: 0.15: 1.
After being weighed so as to be 1 and mixing the three components, the mixed powder was formed into pellets, and the formed body was fired at 900 ° C. for 10 hours in the air. This fired body is crushed,
It was molded again to obtain Target II. Using these targets, a thin film having a thickness of about 100 nm was formed on a SrTiO ₃ substrate under the same conditions as in Example 1.

The overall composition of this thin film is Pb _1.7 Bi _0.3
Sr ₂ Ca _1.7 Er _0.3 Cu ₄ O _10.3 , and the crystal structure analyzed by the 4-axis X-ray diffraction method is La in FIG.
Was replaced with Er. The Tc of this thin film was 101K. Example 10 A target I having the same composition was manufactured in the same manner as in Example 1.

Each powder of CaCO ₃ , Tm ₂ O ₃ , and CuO was mixed with a molar ratio of Ca: Tm: Cu of 0.85: 0.15: 1.
After being weighed so as to be 1 and mixing the three components, the mixed powder was formed into pellets, and the formed body was fired at 900 ° C. for 10 hours in the air. This fired body is crushed,
It was molded again to obtain Target II. Using these targets, a thin film having a thickness of about 100 nm was formed on a Si substrate under the same conditions as in Example 1.

The overall composition of this thin film is Pb _1.7 Bi _0.3
Sr ₂ Ca _1.7 Tm _0.3 Cu ₄ O _10.3 , and the crystal structure analyzed by the 4-axis X-ray diffraction method is La in FIG.
Was replaced with Tm. The Tc of this thin film was 102K. Example 11 A target I having the same composition was produced in the same manner as in Example 1.

Each powder of CaCO ₃ , Yb ₂ O ₃ , and CuO was mixed with a molar ratio of Ca: Yb: Cu of 0.75: 0.25: 1.
After being weighed so as to be 1 and mixing the three components, the mixed powder was formed into pellets, and the formed body was fired at 900 ° C. for 10 hours in the air. This fired body is crushed,
It was molded again to obtain Target II. Using these targets, a thin film having a thickness of about 100 nm was formed on an MgO substrate under the same conditions as in Example 1.

The overall composition of this thin film is Pb _1.7 Bi _0.3
Sr ₂ Ca _1.5 Yb _0.5 Cu ₄ O _10.4 , and the crystal structure analyzed by the 4-axis X-ray diffraction method is La in FIG.
Was substituted with Yb. The Tc of this thin film was 100K. Example 12 A target I having the same composition was produced in the same manner as in Example 1.

The powders of CaCO ₃ , Lu ₂ O ₃ , and CuO were mixed at a molar ratio of Ca: Lu: Cu of 0.75: 0.25: 1.
After being weighed so as to be 1 and mixing the three components, the mixed powder was formed into pellets, and the formed body was fired at 900 ° C. for 10 hours in the air. This fired body is crushed,
It was molded again to obtain Target II. Using these targets, a thin film having a thickness of about 100 nm was formed on a LaAlO ₃ substrate under the same conditions as in Example 1.

The overall composition of this thin film is Pb _1.7 Bi _0.3
Sr ₂ Ca _1.5 Lu _0.5 Cu ₄ O _10.4 , and the crystal structure analyzed by the 4-axis X-ray diffraction method is La in FIG.
Was replaced with Lu. The Tc of this thin film was 101K. Example 13 Each powder of PbO, Tl ₂ O ₃ , SrCO ₃ and CuO was
The molar ratio of b: Tl: Sr: Cu is 1.7: 0.3: 2: 2.2
After weighing and mixing the four powders into a pellet, the compact was fired at 800 ° C. for 8 hours in a nitrogen stream.

The weight of the fired body was weighed, and the amounts of Pb and Tl were calculated. This fired body is pulverized, and the calculated Pb
PbO equivalent to the amount of Pb and Tl twice the amount of Tl
Powder and Tl ₂ O ₃ powder were added. The obtained mixed powder was molded and used as a target I. CaCO ₃ , La ₂ (CO ₃ )
_3. Each powder of xH ₂ O and CuO was weighed so that the molar ratio of Ca: La: Cu was 0.75: 0.25: 1.1, and the three powders were mixed, and the mixed powder was pelletized. After that, the molded body was fired in the air at 900 ° C. for 10 hours. The fired body was pulverized and formed again to obtain a target II.

The targets I and II were separately set on a rotary target holder in a vacuum chamber, and an MgO substrate was placed at a position 50 mm away from these targets and the oxygen partial pressure in the vacuum chamber was reduced to 1 × 10 2. ^-3 mb
The substrate temperature was kept at 560 ° C. in the state of ar. The target holder is rotated, an ArF excimer laser is applied to each target, and the intensity of the RHEED vibration is monitored.
Each target was irradiated by switching between and targets.

A thin film having a thickness of about 100 nm was obtained on the substrate. The overall composition of this thin film is Pb _1.7 Tl _0.3 S
r ₂ Ca _1.5 La _0.5 Cu ₄ O _10.4 , and the crystal structure analyzed by four-axis X-ray diffraction was as shown in FIG. The Tc of this thin film was 106K. Example 14 A target I having the same composition was molded in the same manner as in Example 13. Further, a target II having the same composition was molded in the same manner as in Example 2.

Using these targets, a thickness of about 100 nm was formed on a SrTiO ₃ substrate in the same manner as in Example 13.
m was formed. The overall composition of this thin film is Pb _1.7
It was Tl _0.3 Sr ₂ Ca _1.7 Y _0.3 Cu ₄ O _10.3 , and its crystal structure was such that La was replaced by Y in FIG. The Tc of this thin film was 105K.

Example 15 A target I having the same composition was molded in the same manner as in Example 13. Further, a target II having the same composition was molded in the same manner as in Example 3. Using these targets, a thickness of about 100 n was formed on a Si substrate in the same manner as in Example 13.
m was formed.

The overall composition of this thin film is Pb _1.7 Tl _0.3
It was Sr ₂ Ca _1.6 Nd _0.4 Cu ₄ O _10.4 , and its crystal structure was such that La in FIG. 1 was substituted with Nd. The Tc of this thin film was 107K. Example 16 A target I having the same composition was molded in the same manner as in Example 13. Further, a target II having the same composition was molded in the same manner as in Example 4.

Using these targets, a 100 nm thick layer was formed on a LaAlO ₃ substrate in the same manner as in Example 13.
m was formed. The overall composition of this thin film is Pb _1.7
Tl _0.3 Sr ₂ Ca _1.5 Sm _0.5 Cu ₄ O _10.4 ,
Its crystal structure was such that La was replaced by Sm in FIG. The Tc of this thin film was 105K.

Example 17 A target I having the same composition was molded in the same manner as in Example 13. Also, a target II having the same composition was molded in the same manner as in Example 5. Using these targets, a thin film having a thickness of about 100 nm was formed on a LaGaO ₃ substrate in the same manner as in Example 13.

The overall composition of this thin film is Pb _1.7 Tl _0.3
It was Sr ₂ Ca _1.6 Eu _0.4 Cu ₄ O _10.4 , and its crystal structure was such that La in FIG. 1 was replaced by Eu. The Tc of this thin film was 106K. Example 18 A target I having the same composition was molded in the same manner as in Example 13. Also, a target II having the same composition was molded in the same manner as in Example 6.

Using these targets, a thickness of about 100 n was formed on a SrTiO ₃ substrate in the same manner as in Example 13.
m was formed. The overall composition of this thin film is Pb _1.7
Tl _0.3 Sr ₂ Ca _1.6 Gd _0.4 Cu ₄ O _10.4 ,
Its crystal structure was such that La was replaced by Gd in FIG. The Tc of this thin film was 106K.

Example 19 A target I having the same composition was molded in the same manner as in Example 13. Further, a target II having the same composition was molded in the same manner as in Example 7. Using these targets, a thickness of about 100 n was formed on a Si substrate in the same manner as in Example 13.
m was formed.

The overall composition of this thin film is Pb _1.7 Tl _0.3
It was Sr ₂ Ca _1.7 Dy _0.3 Cu ₄ O _10.3 , and its crystal structure was such that La in FIG. 1 was substituted with Dy. The Tc of this thin film was 105K. Example 20 A target I having the same composition was molded in the same manner as in Example 13. Further, a target II having the same composition was molded in the same manner as in Example 8.

Using these targets, a thin film having a thickness of about 100 nm was formed on an MgO substrate in the same manner as in Example 13. The overall composition of this thin film is Pb _1.7 Tl
_0.3 Sr ₂ Ca _1.7 Ho _0.3 Cu ₄ O _10.3 , and its crystal structure was such that La was replaced with Ho in FIG. The Tc of this thin film was 106K.

Example 21 A target I having the same composition was molded in the same manner as in Example 13. Also, a target II having the same composition was molded in the same manner as in Example 9. Using these targets, a thin film having a thickness of about 100 nm was formed on a LaAlO ₃ substrate in the same manner as in Example 13.

The overall composition of this thin film is Pb _1.7 Tl _0.3
It was Sr ₂ Ca _1.7 Er _0.3 Cu ₄ O _10.3 , and its crystal structure was such that La was replaced by Er in FIG. The Tc of this thin film was 106K. Example 22 A target I having the same composition was molded in the same manner as in Example 13. Also, a target II having the same composition was molded in the same manner as in Example 10.

Using these targets, a LaGaO ₃ substrate having a thickness of about 100 nm was formed in the same manner as in Example 13.
m was formed. The overall composition of this thin film is Pb _1.7
Tl _0.3 Sr ₂ Ca _1.7 Tm _0.3 Cu ₄ O _10.3 ,
Its crystal structure was such that La was replaced by Tm in FIG. The Tc of this thin film was 107K.

Example 23 A target I having the same composition was molded in the same manner as in Example 13. Further, a target II having the same composition was molded in the same manner as in Example 11. Using these targets, a thin film having a thickness of about 100 nm was formed on a SrTiO ₃ substrate in the same manner as in Example 13.

The overall composition of this thin film is Pb _1.7 Tl _0.3
It was Sr ₂ Ca _1.5 Yb _0.5 Cu ₄ O _10.4 , and its crystal structure was such that La in FIG. 1 was substituted with Yb. The Tc of this thin film was 105K. Example 24 A target I having the same composition was molded in the same manner as in Example 13. Further, a target II having the same composition was molded in the same manner as in Example 12.

Using these targets, a thin film having a thickness of about 100 nm was formed on a Si substrate in the same manner as in Example 13. The overall composition of this thin film is Pb _1.7 Tl _0.3
It was Sr ₂ Ca _1.5 Lu _0.5 Cu ₄ O _10.4 , and its crystal structure was such that La was replaced by Lu in FIG. The Tc of this thin film was 106K.

[0069]

As is clear from the above description, the oxide superconductor of the present invention can be synthesized even in an inert atmosphere or an extremely low-concentration oxygen atmosphere. It can be integrated with fibers and the like without lowering their mechanical strength.

Further, since the oxide superconductor of the present invention has three CuO ₂ layers present in the unit crystal structure, its Tc is a high temperature of 100 K or more, and is excellent in practicality. .

[Brief description of the drawings]

FIG. 1 is a schematic view showing a crystal structure of an oxide superconductor of Example 1.

Continuation of front page (56) References JP-A-3-177316 (JP, A) JP-A-2-271920 (JP, A) JP-A-2-137725 (JP, A) JP-A-3-170359 (JP) No. 4-503051 (JP, A) Toshio Nonaka et al., “Creation of Pb-based superconducting film”, Proceedings of the Ceramic Society of Japan 1991 Annual Meeting, May 22, 1991, p. 61, NONAKA T. , "The relation between super-educting property ties and microstructure of bismuth lead strontium calcium copper oxide filter (BPSCCObfilcobidex)." Sci. Monogr. , Vol. 70, 1991, p. 869-875 (58) Field surveyed (Int. Cl. ⁷ , DB name) C01G 1/00 CA (STN) INSPEC (DIALOG) JICST file (JOIS) REGISTRY (STN) WPI (DIALOG)

Claims (2)

(57) [Claims] 1. A following _{formula: (Pb 1-p Bi p} ) 2 Sr 2 (Ca
_1-q A _q ) ₂ Cu _{4 Or} (where A is Y, La, Nd, S
m, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu
Represents at least one element selected from the group of
q and r are respectively 0 <p ≦ 0.4, 0.15 ≦ q ≦
0.25, and 9.5 ≦ r ≦ 10.65). Wherein the following _{formula: (Pb 1-p Tl p} ) 2 Sr 2 (Ca
_1-q A _q ) ₂ Cu _{4 Or} (where A is Y, La, Nd, S
m, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu
Represents at least one element selected from the group of
q and r are respectively 0 <p ≦ 0.6 and 0.15 ≦ q ≦
0.25, and 9.5 ≦ r ≦ 11.05).