JPH0597432A - Superconductor - Google Patents

Abstract

(57) [Abstract] [Purpose] La (212) has superconducting properties equivalent to those of conventional ones even when the HIP treatment temperature in high oxygen partial pressure is low.
6) Providing a system superconductor. [Structure] General formula, (La _1-η Ba _η ) _2-θ (Ca
_1-γ Mg _γ ) _{1 + θ} Cu ₂ O _δ , where 0 ≦ η <0.2 0 ≦ θ <0.3 0 <γ ≦ 0.4 5.9 <δ <6.1 or (La _1-α Sr _α ) _2- βCa1 ₊ βCuCu2 _-ξLi
ξ O _ζ However, a superconductor represented by 0 ≦ α <0.3 0 ≦ β <0.3 0 <ξ ≦ 0.3 5.9 <ζ <6.1.

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 magnetohydrodynamic generator, an accelerator, a rotating electric machine (motor, generator, etc.),
Suitable as a magnetic coil material for magnetic separators, magnetic levitation trains, nuclear magnetic resonance measurement equipment, magnetic propulsion vessels, electron beam exposure equipment, various experimental equipment, transmission lines, electric energy storage, transformers, rectifiers, regulators, etc. Suitable for applications where power loss is a problem such as phaser, Josephson device, SQUI
The present invention relates to a superconductor suitable as an element such as a D element and a superconducting transistor, and further as a functional material such as an infrared detection material and a magnetic shielding material.

[0002]

2. Description of the Related Art As a superconductor having a high superconducting transition temperature,
There is a series of well known copper complex oxide based superconductors. A copper composite oxide having a structure similar to those of these copper composite oxide superconductors, that is, in the unit cell, mainly Ca
It includes two pyramid structures composed of Cu and O, the bottom surfaces of which are opposed to each other with a layer made of La, and a layer composed of these pyramid structures, mainly Ca and the pyramid structure is La ₂
Of O ₂ through the stacked structure, so-called La (21
The 26) -based copper composite oxide is expected to become superconducting due to the similarity in crystal structure, and many studies have been conducted. Then, superconducting properties of (La _1-x Sr _x ) ₂ CaCu ₂ O _y with Tc _zero of 40 to 50 K have been confirmed (“Nature”, Volume 345, Volumes 602 to 60).
4 pages, 1990). However, this superconductor
Not only is it difficult to manufacture, but it is not suitable for the production of large or long products, because it requires the use of difficult-to-handle raw materials and must be contained in a glass anvil and sintered. _{Then, La 2-x Ca 1 +} x Cu 2 O y
In the above, it was found that HIP (Hot Isostatic Press) treatment of a product sintered in air or oxygen of 1 atm in a high oxygen partial pressure makes it superconducting, but this composition has a HIP treatment temperature of 1200 ° C. It has to be raised to the front and back, and since this temperature is close to the melting point, delicate temperature control is required, which is not industrial.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the conventional so-called La (2126) type superconductor, and to solve the conventional problems even when the HIP treatment temperature is high during high oxygen partial pressure. Another object of the present invention is to provide a La (2126) -based superconductor capable of obtaining superconducting properties equivalent to those of the above.

[0004]

In order to achieve the above object, the present invention provides a superconductor represented by the following general formula (hereinafter referred to as the first invention).

(La _1-η Ba _η ) _2-θ (Ca _1-γ Mg _γ ) _{1 + θ} Cu ₂ O _δ However, 0 ≦ η <0.2 0 ≦ θ <0.3 0 <γ ≦ 0.4 5.9 <δ <6.1 The present invention also provides a superconductor represented by the following general formula (hereinafter referred to as the second invention).

(La _1-α Sr _α ) _2-β Ca _{1 + β} Cu _2-ξ Li _ξ O _ζ where 0 ≦ α <0.3 0 ≦ β <0.3 0 <ξ ≦ 0.3 5.9 <Ζ <6.1 The structure of the superconductor of the present invention is C in the unit cell.
It contains two units of a pyramid structure in which O is five-coordinated around u or Li substituted with u. Also, these C
The pyramid type unit consisting of u or Li and O is
The arrangement is such that the bottom surfaces face each other with sandwiching mainly Ca or Mg which are alkaline earth elements. Furthermore, each unit cell is in the c-axis direction (direction perpendicular to the bottom surface of the pyramid type),
O located at the apex of the pyramid and La or Sr or Ba substituted with La are stacked while forming a rock salt structure. Further, the single phase of this crystal structure is obtained only when the ratio of La or Sr or Ba substituted with La to Ca or Mg that is an alkaline earth element and Cu or Li is within a certain range. That is, in the general formulas of the first invention and the second invention, if θ or β deviates from the above-mentioned range, the crystal structure may become a different crystal system, or other impurity phases (insulators) may be mixed. Become.

In the superconductor of the present invention, the superconducting charge carrier is given by holes, and the hole concentration is 0.01 per Cu, as in the conventional hole-type copper complex oxide superconductor.
As described above, it becomes a superconductor only when it is 0.25 or less. Then, the hole concentration is −6 + 0.5θ + η in the case of the first invention.
−0.5 × η × θ + δ, in the case of the second invention (-12 + β
+ 2α−α × β + ξ + 2ζ) / (2-ξ), so in the case of the first invention, 2.01 <−4 + 0.5θ + η
−0.5 × η × θ + δ <2.25, and 2.01 <(− 8 + β + 2α−α × β− in the case of the second invention.
ξ + 2ζ) / (2-ξ) <2.25.

When the structure is ideally realized, the superconductor of the first invention is (La _1-η Ba _η ) ₂ (Ca _1-γ Mg
_γ ) ₁ Cu ₂ O ₆ , and the superconductor of the second invention is (La
_{1- α} Sr _α ) ₂ Ca ₁ Cu _2-ξ Li _ξ O ₆ , but normally there is an excess or deficiency of oxygen, so in the case of the first invention, (La _1-η Ba _{η) 2-θ} (Ca _1-γ Mg _γ ) _1+
θ Cu ₂ O _δ , in the case of the second invention (La _1-α Sr _α )
A composition range of 5.9 <δ <6.1 or 5.9 <ζ <6.1 in the general formula of _2-β Ca _{1 + β} Cu _{2 −ξ} Li _ξ O _ζ is allowed. Further, in the rock salt structure described above, the element at the position of La or Sr or Ba substituted with La and the element at the position of Ca or Mg sandwiched between the opposed bottom surfaces of the pyramid-shaped unit made of Cu or Li and O. There is a slight replacement with, and in particular, some of the elements that should enter the positions of Ca and Mg are La or Sr in which it is substituted.
The structure becomes more stable when entering the position of or Ba. Therefore, 0 ≦ θ <0.3 is imposed in the first invention, and 0 ≦ β <0.3 is imposed in the second invention. Further, in the first invention, 0 ≦ η <from the solid solution limit of Ba or Mg.
0.2 and 0 <γ ≦ 0.4 are added, and in the second invention, 0 ≦ α <0.3 from the solid solution limit of Sr and Li.
And the restriction of 0 <ξ ≦ 0.3 is added.

Now, in the superconductor of the present invention, O
HIP treatment is performed in a high oxygen partial pressure in order to control the amount of H 2 and adjust the concentration of holes to be injected. Normal La2 _- xCa
_{In 1+ x} Cu ₂ O _y , oxygen is not easily taken in unless heat treatment is performed at a temperature close to its melting point, that is, at a high temperature of about 1200 ° C., and a superconducting charge carrier cannot be injected, so that a sufficient superconducting transition temperature cannot be obtained. In the first and second inventions, trivalent La is substituted with divalent Ba, trivalent La is substituted with divalent Sr, and divalent Cu is monovalent L.
i, and these substitutions and additionally C by Mg
By substituting a, the packing state of atoms is changed to facilitate the incorporation of O.
Even with P treatment, a superconducting transition temperature of the same level as in the case of HIP treatment at a temperature of about 1200 ° C. of La _2−x Ca _{1 + x} Cu ₂ O _y can be obtained, and the cycle of HIP treatment can be accelerated, and The energy required for HIP processing can be reduced.

The superconductor of the present invention can be manufactured by various methods. For example, a so-called powder mixing method can be used. In this method, powders of oxides of component elements and precursors thereof (carbonates, nitrates, etc.) are mixed at a desired ratio, fired at a temperature equal to or lower than the sintering temperature, further pulverized and mixed to obtain a desired shape. This is a method of forming, sintering in an atmosphere having an oxygen partial pressure of 5 atm or less, and further HIPing it in an atmosphere having an oxygen partial pressure of 10 atm or more to obtain a superconductor.

Further, when forming a thin film, well-known various vapor deposition methods such as electron beam vapor deposition method and laser vapor deposition method, various sputtering methods such as magnetron sputtering method, halides and organic metals are used. The chemical vapor deposition method used, the atomization method using a nitrate or an organic acid salt, or the coating method using an alkoxide or the like can be used.

The superconductor of the present invention can be used in various forms such as a tape form, a linear form, a fibrous form and a sheet form. It can also be used by forming it on a reinforcing wire made of carbon fiber, ceramics, or metal such as silver. Further, it can be used by being packed in a hollow reinforcing material such as a silver sheath. Furthermore, a superconducting wire having a multi-core wire structure can be formed by using a matrix of copper or the like. In addition, Si, MgO, SrTiO ₃ , LaGa
It can be formed as a thin film on a substrate such as O ₃ or NdGaO ₃ and can be used for wiring various elements and LSI.

[0013]

Example 1 La ₂ O ₃ , BaCO ₃ , CaCO ₃ , M
Each powder of gO and CuO was added to La: Ba: Ca: Mg: C.
u was measured to be 1.6: 0.2: 1.0: 0.2: 2.0, mixed in an agate mortar, put in an Al ₂ O ₃ container, and heated in air at 950 ° C. It was baked for 12 hours.
Further, it was ground again in an agate mortar, molded into pellets, baked in air at 1000 ° C. for 24 hours, and then gradually cooled.

Next, the pellet-shaped sintered body was mixed with a mixed gas of oxygen and argon at a mixing ratio of 1: 4 and 1020
HIP treatment was carried out at a temperature of ℃ at a total pressure of 1800 atm (oxygen partial pressure: 360 atm) for 3 hours, and then cooled to room temperature in 1.5 hours.

The composition of the obtained superconductor is (La
_{0.89 Ba 0.11) 1.8 (Ca 0.} 83 Mg
_0.17 ) _1.2 Cu ₂ O _6.03 , the temperature dependence of the electrical resistance was measured by the ordinary four-terminal method.
At K, the resistance began to drop sharply due to the superconducting transition (Tc _onset ), and at 32K, the resistance became zero (T
c _zero ). When the temperature dependence of the AC susceptibility was measured in powder form, the onset of the Meissner effect (Tc
(Χ) _onset ) was confirmed.

[0016]

Example 2 La ₂ O ₃ , SrCO ₃ , CaCO ₃ , C
uO and Li ₂ CO ₃ powders were mixed with La: Sr: Ca: C.
u: Li was measured to be 1.8: 0.2: 1.0: 1.8: 0.2, mixed in an agate mortar, and then Al ₂
It was put in a container of O ₃ and baked in air at 950 ° C. for 12 hours. Furthermore, after crushing again in an agate mortar, forming into pellets, and baking in air at 1050 ° C. for 12 hours,
It was taken out at room temperature. Next, the pellet-shaped sintered body was mixed with a mixed gas of oxygen and argon at a ratio of 1: 4,
At 1075 ° C, total pressure 2000 atm (oxygen partial pressure: 400
HIP treatment for 8 hours in the atmospheric pressure), and then cooled to room temperature in 2 hours.

The composition of the obtained superconductor is (La _0.9
Sr _0.1 ) ₂ Ca ₁ Cu _1.8 Li _0.2 O _6.02
, Tc _onset is 60K, Tc _zero is 43K, Tc
(Χ) _onset was 53K.

[0018]

Example 3 La ₂ O ₃ , CaCO ₃ , MgO, CuO
Each powder of La: Ca: Mg: Cu was 1.8: 0.
Weigh it out to 9: 0.3: 2.0, mix it in an agate mortar, put it in a container of Al ₂ O ₃ , and put it in air for 9
It was baked at 50 ° C. for 12 hours. Further, it was crushed again in an agate mortar and molded into pellets.

Next, the pellet-shaped molded body was heated at 1050 ° C. using a mixed gas of oxygen and argon at a mixing ratio of 1: 4.
Then, HIP treatment was carried out for 5 hours at a total pressure of 1500 atm (oxygen partial pressure: 300 atm), and then cooled to room temperature for 1 hour.

The composition of the obtained superconductor is (La _1.8
(Ca _0.75 Mg _0.25 ) _{1. 2} Cu ₂ O _6.07
So, Tc _onset is 52K, Tc _zero is 31K, Tc
(Χ) _{on set} was 45K.

[0021]

Comparative Example 1 La ₂ O ₃ , CaCO ₃ , and CuO powders were weighed so that La: Ca: Cu was 1.8: 1.2: 2.0, and mixed in an agate mortar. Al ₂ O ₃
It was put in a container of and heated at 950 ° C. in air for 12 hours. Further, it was ground again in an agate mortar, formed into pellets, baked in air at 1050 ° C. for 12 hours, and then taken out at room temperature.

Next, the pellet-shaped sintered body was mixed with a mixed gas of oxygen and argon at a mixing ratio of 1: 4, and 1050
HIP treatment was performed at a temperature of ℃ for 5 hours at a total pressure of 2000 atm (oxygen partial pressure: 400 atm), and then cooled to room temperature for 2 hours.

The composition of the obtained superconductor is La _1.8 C.
a _1.2 Cu ₂ O ₅ , Tc _{on set} 40K, Tc
_Zero was 15K and Tc (χ) _onset was 32K.

[0024]

Comparative Example 2 La ₂ O ₃ , CaCO ₃ , and CuO powders were weighed so that La: Ca: Cu was 1.8: 1.2: 2.0, and mixed in an agate mortar. Al ₂ O ₃
It was put in a container of and heated at 950 ° C. in air for 12 hours. Further, it was ground again in an agate mortar, formed into pellets, baked in air at 1050 ° C. for 12 hours, and then taken out at room temperature.

Next, the pellet-shaped sintered body was mixed with 1225 using a mixed gas of oxygen and argon at a mixing ratio of 1: 4.
HIP was carried out at a temperature of ℃ at a total pressure of 2000 atm (oxygen partial pressure: 400 atm) for 5 hours and then cooled to room temperature for 2 hours.

The composition of the obtained superconductor is La.
_1.8 (Ca _0.75 Mg _0.25 ) _1.2 Cu ₂ O
It is _6.07 , Tc _onset is 58K, Tc _zero is 41.
The K and Tc (χ) _onset were 50K.

[0027]

The superconductor of the present invention has the general formula: (La _1-η Ba _η ) _2-θ (Ca _1-γ Mg _γ ) _{1 + θ} Cu ₂ O _δ , where 0 ≦ η <0.20 ≦ It is represented by θ <0.3 0 <γ ≦ 0.4 5.9 <δ <6.1, or (La _1-α Sr _α ) _2-β Ca _{1 + β} Cu _2-ξ Li _ξ O _ζ , It is expressed by 0 ≦ α <0.3 0 ≦ β <0.3 0 <ξ ≦ 0.3 5.9 <ζ <6.1, and as shown in the examples, in high oxygen partial pressure. Even if the HIP treatment temperature is low, it has superconducting properties equivalent to the conventional one known in this system.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 39/24 ZAA Z 8728-4M

Claims (2)

[Claims] 1. A superconductor represented by the following general formula. (La _1-η Ba _η ) _2-θ (Ca _1-γ Mg _γ ) _{1 + θ} Cu ₂ O _δ However, 0 ≦ η <0.2 0 ≦ θ <0.3 0 <γ ≦ 0.4 5.9 <Δ <6.1 2. A superconductor represented by the following general formula. (La _1-α Sr _α ) _2-β Ca _{1 + β} Cu Cu _2-ξ Li _ξ O _ζ , where 0 ≦ α <0.3 0 ≦ β <0.3 0 <ξ ≦ 0.3 5.9 <ζ < 6.1