JPH02279517A - Superconductor - Google Patents

Abstract

PURPOSE:To develop a superconductor with the charge density easily adjustable by forming the superconductor with La, specified rare earth elements, alkaline earth metals and CuO. CONSTITUTION:At least one kind among the oxides of rare earth elements such as Sm2O3, Eu2O3 and Gd2O3, at least one or two kinds among the oxides of alkaline earth metals such as SrCO3, BaCO3 and CaCO3 and CuO are mixed into powdery La2O3, and the mixture is calcined in the air at 1000 deg.C for 10hr. The calcined body is again crushed, pelletized, sintered in the air, heat-treated at 500 deg.C in an oxygen atmosphere kept at 500 atm, and then annealed. A superconductor having a composition expressed by the general formula (La1-p-qalphapbetaq)xCuOy is thus produced. In the formula, alpha is the rare earth elements such as Sm, Eu and Gd, beta is the alkaline earth metals such as Ca, Sr and Ba, 0.2<p<0.8, 0.025<q<0.25, 1.8<x<2.2, and 3.6<y<4.1.

Description

Detailed Description of the Invention (Field of Industrial Application) This invention is applicable to nuclear fusion reactors, magnetohydrodynamic generators, accelerators, rotating electrical equipment such as electric motors and generators, magnetic separators, magnetic levitation trains, nuclear magnetic Suitable as a material for magnet coils in resonance measurement devices, magnetic propulsion vessels, electron beam exposure devices, etc. Also suitable for applications where power loss is a problem, such as power transmission lines, electrical energy storage devices, transformers, rectifiers, and LSI wiring. Furthermore, the present invention relates to a superconductor suitable for use in various devices such as Josephson devices, 5QUID devices, and superconducting transistors, and furthermore suitable as infrared detection materials, magnetic shielding materials, and the like.

(Prior Art) Among the substances conventionally known as superconductors, a series of copper composite oxides can be mentioned as those having a high superconducting transition temperature. Among them, those in which five oxygen ions are coordinated with a copper ion are attracting attention because they can be either p-type or n-type, and have a superconducting transition temperature of 30 degrees (Nd.

Ce, Sr) 2Cub4 is known, but Nd.

The solid solution range of Ce and Sr is narrow, making it difficult to control the charge concentration 5
There is a problem.

(Problems to be Solved by the Invention) An object of the present invention is to provide a superconductor in which copper ions are coordinated with five oxygen ions, and the charge concentration can be easily adjusted.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a superconductor represented by the following general formula.

(La l-11-Q'Z pβ,), Cub.

However, 0, 2<p<Q, 8 0.025<q<0.25 1, 8<x<2.2 3.6<y<4.1 α: At least one selected from Sm, Eu and Gd One element β: At least one element selected from Ca, Sr, and Ba. However, in this invention, as the element α, S
When only m is selected, it is not possible to select only Ca from the elements β.

The superconductor of the present invention has a structure (generally called a T0 structure) consisting of La, a rare earth element, an alkaline earth metal element, Cu, and O (N d ).

It is a superconductor with a structure similar to Ce, Sr) 2Cub. Rare earth elements include Sm and Eu5Gd, and alkaline earth metal elements include Ca.

Each can be selected from Sr and Ba. It is not essential to select one type of these, but two or three types may be selected and used in any mixing ratio. However, as mentioned above, S as the element of α
When only m is selected, it is not possible to select only Ca from the elements of β.

In the superconductor of this invention, charge is provided by holes. Its concentration is primarily controlled by alkaline earth metals, although it is also related to O.

Now, as is well known, the conventional (
Nd, Ce, Sr) In a superconductor with a 2Cub4 structure, there are four types of sites: Nd site, Sr site, Cu site, and O site, but in the case of the superconductor of this invention, basically the above Nd The site is occupied by S.
m, Eu, Gd.

Ca, and La occupies the above Sr site.
, Sr, and Ba, and C occupies the Cu size 1~
u, and 0 occupies the 0 site. Therefore, the above general formula (La1-p-q α.

Ideally, X and y in βQ ) X Cu Or are x=2 and Y=4. In reality, since there are atomic defects, both Xs'/ have a certain range. In particular, since O is easily lost, the value of y is usually smaller than 4.

Next, regarding the values of p and q, as p is gradually increased, the crystal structure disappears from the T' tank structure, and p=1
The result is a structure similar to that of Nd2Cu04, which is limited to . From this, the upper limit of p is determined to be 0.8. Also, as the value of p is gradually decreased, the crystal structure changes to (La, 5r)2 Cub, which is the limit of p=o.
, changes to a similar structure. Therefore, the lower limit of p is 0,
Set it to 2. Further, for the reason regarding the occupied site mentioned above, it is preferable that the value of p is close to 0.5, and 0.4 to 0.
．． A range of 6 is preferable. By doing so,
The superconductor becomes very stable in terms of crystal chemistry, and the hole concentration due to the alkaline earth metal can be controlled over a wide range of 0 to 0.4.

On the other hand, the value of q is determined based on electrical conditions.

In the superconductor of this invention, the charge carriers responsible for superconducting current are holes, and the concentration thereof is expressed by the formula, q'x-2・(4
-y)+3・(2-x).

Generally, in a copper composite oxide superconductor, the hole concentration is C
u is 0.1 to 0. It is known that the superconducting transition temperature is highest when it is in the range of shall be.

The superconductor of the present invention can be used in various forms such as tape, line, fiber, and sheet. Also,
It can also be formed on a reinforcing wire made of carbon fibers, ceramic fibers, fibers formed by forming an intermediate layer of ceramics on the surface of these carbon fibers or ceramic fibers, or metal fibers such as silver fibers. Furthermore, it can also be used by being filled in a reinforcing hollow material such as a silver sheath. Also,
Multicore superconducting wires can also be made using a matrix of copper or other materials. Furthermore, S i, MgO1L a
It can be formed as a thin film on a base material such as GaO, and used as various elements or as LSI wiring.

The superconductor of this invention can be manufactured by various methods.

For example, it can be manufactured by a so-called powder mixing method. This method involves mixing powders of constituent element oxides or their precursors (carbonates, nitrates, etc.) in desired proportions,
This is a method in which the material is fired at a temperature below the sintering temperature, further pulverized, mixed, molded into a desired shape, and then sintered to form a superconductor.

In addition, thin films can be formed using various evaporation methods such as electron beam evaporation and laser evaporation, various sputtering methods such as magnetron sputtering, chemical vapor deposition using halides and organic metals, and nitrate and organic acid salts. Conventionally known methods such as an atomization method using an alkoxide or a coating method using an alkoxide or the like can be used. In addition, since the superconductor of this invention is prone to oxygen vacancies, 100%
It is preferable to perform the heat treatment in an oxygen atmosphere at a pressure higher than the atmospheric pressure, or in a gas such as N20 or 03 that easily produces active oxygen atoms during decomposition.

(Example) Example 1 Each powder of La2O3, Sm2O3, SrcO3, and CuO was measured so that the ratio of La:Sm:Sr:Cu was 8=102:10, and the powder was ground and mixed in an agate mortar. After that, put it in an A1□03 container and heat it at 1000℃ in the air.
It was baked for 10 hours.

Next, the fired body was crushed in an agate mortar, formed into pellets, sintered in air at 1130°C for 10 hours, and further
Heat treatment was performed at 500° C. for 5 hours in an oxygen atmosphere of 0.00 atm, followed by slow cooling.

Obtained (La0.4 Smo, s s'ro, 1)
The superconductor 2Cu04o2 had a hollow T9 structure, as shown in the X-ray diffraction pattern in FIG. In FIG. 1, the peak indicated by the arrow is the peak representing the T0 structure. Further, the superconducting transition temperature was 20, and the hole concentration was 0.24 for 1 for Cu.

Example 2 Each powder of La203, Sm2O3, BaCO3, and CuO was prepared in a ratio of La:Sm:Ba:Cu of 10:8:2:10.
After crushing and mixing it in an agate mortar, put it in an Al2O3 container and: 10 in air.
It was baked at 00°C for 10 hours.

Next, the fired body was crushed in an agate mortar, formed into pellets, sintered in air at 1110°C for 10 hours, and further
Heat treatment was performed at 500° C. for 5 hours in an oxygen atmosphere of 0.00 atm, followed by slow cooling.

Obtained (Lao, Smo4Bao,)2CuO39
The superconductor No. 8 had a superconducting transition temperature of 18 and a hole concentration of 0.16 for Cu of 1.

Example 3 Each powder of La203, Eu203, CaC01, and CuO was prepared in a ratio of La:Eu:Ca:Cu of 12:6:2:10.
After crushing and mixing it in an agate mortar, put it in an Al2O container and heat it in the air for 1000 min.
It was baked at ℃ for 10 hours.

Next, the fired body was crushed in an agate mortar, formed into pellets, sintered in air at 1130°C for 10 hours, and further
Heat treatment was performed at 500° C. for 5 hours in an oxygen atmosphere of 0.00 atm, followed by slow cooling.

Obtained (Lao6Eu, ), 3 Cao, 1) 2
The superconductor made of CuO3, as shown in the X-ray diffraction pattern in Figure 2, had a hollow T'' structure.The superconducting transition temperature was 18, and the hole concentration was 1 for Cu. It was 0.18.

Example 4 Each powder of La203, Eu2O3, Srco3, and CuO was prepared in a ratio of La:Eu:Sr:Cu of 8.5:9.5:2.
: Weighed it out so that it was 10%, crushed it in an agate mortar, mixed it, put it in an Al2O3 container, and heated it in the air to 10%.
It was baked at 000°C for 10 hours.

Next, the fired body was crushed in an agate mortar, formed into pellets, sintered in air at 1130°C for 10 hours, and further
Heat treatment was performed at 500° C. for 5 hours in an oxygen atmosphere of 0.00 atm, followed by slow cooling.

Obtained (L ao, a□, E uo47.S r
The superconductor 2CuO4o2 has a superconducting transition temperature of 25, and the hole concentration is 0,1 for Cu.
It was 24.

Example 5 Each powder of La201, Gd2O3, CaCO3, and CuO was prepared in a ratio of La:Gd2Ca:Cu of 9:8°5:2.5:1.
After crushing and mixing it in an agate mortar, it was placed in an Al2O3 container and heated to 100% in the air.
It was baked at 0°C for 10 hours.

Next, the fired body was crushed in an agate mortar, formed into pellets, sintered in air at 1140°C for 10 hours, and further
Heat treatment was performed at 500° C. for 5 hours in an oxygen atmosphere of 0.00 atm, followed by slow cooling.

Obtained (Lat), 45Gd0.425CaO,
J25) The superconductor consisting of 2CuO1,... had a hollow T'' structure as shown in the X-ray diffraction pattern in Figure 3.The superconducting transition temperature was 22, and the hole concentration was It was 0.23 to 1.

Example 6 Each powder of La203, Gd201.5rCO1, and CuO was prepared in a ratio of La:Gd:Sr:Cu of 7.5:10.5:2:
Measure out 10 pieces, crush it in an agate mortar,
After mixing, put it in an AlzOi container and leave it in the air for 10 minutes.
It was baked at 00°C for 10 hours.

Next, the fired body was crushed in an agate mortar, formed into pellets, sintered in air at 1110°C for 10 hours, and further
Heat treatment was performed at 500° C. for 5 hours in an oxygen atmosphere of 0.00 atm, followed by slow cooling.

Obtained (LaO, 375GdO, 525S ro,
t) The superconductor 2CuO4,oo is shown in Fig.
As shown in the line diffraction pattern, it had a T' structure. Further, the superconducting transition temperature was 19, and the hole concentration was 0.20 for 1 for Cu.

Example 7 La203, Gd2O3, CaCO3, S rCO3
, BaCO3, CuO powder, La; Gd: Ca:
Sr:Ba:Cu is 9:9:1:0゜6:0.4+10
After crushing and mixing it in an agate mortar, put it in an Al2O container and heat it in the air for 1000 min.
It was baked at ℃ for 10 hours.

Next, the fired body was crushed in an agate mortar, formed into pellets, sintered in air at 1100°C for 24 hours, and further
Heat treatment was performed at 500° C. for 5 hours in an oxygen atmosphere of 0.00 atm, followed by slow cooling.

Obtained (La0.45GdO, 45ccao, 05'
The superconductor S ro, o3Bao, C2))2 CuO3,a had a superconducting transition temperature of 16 and a hole concentration of 0.16 for Cu of 1.

Example 8 La203, Sm203, ELI203, Gd2
Each powder of O3, SrCO3, BaCO3, CuO is
a:Sm:Eu:Gd:Sr:Ba:Cu is 9:3:2
:4:1:1:10, crush it in an agate mortar, mix it, put it in an Al2O3 container,
It was fired in air at 1000°C for 10 hours.

Next, the fired body was crushed in an agate mortar, formed into a pellet shape, sintered in air at 1100°C for 24 hours, and further
Heat treatment was performed at 500° C. for 5 hours in an oxygen atmosphere of 0.00 atm, followed by slow cooling.

Obtained (La, 4. (Smo, , E uo
, .

Gdo2) (S rO, 0513ao, 05) )
The superconductor 2 Cub 3,9 had a superconducting transition temperature of 16, and a hole concentration of 0.18 for Cu of 1.

(Effect of the invention) The superconductor of this invention has the general formula: (La l-9-Q (Ipβ,), Cub.

However, 0, 2<I)<0. 8 0.025<q<0.25 1, 8<x<2. 2 3, 6<Y<4. 1 α: At least one element selected from Sm5Eu and Gd β: At least one element selected from Ca, Sr and Ba (However, as the element α above, Sm
(If only Ca is selected, it is not possible to select only Ca among the β elements).As shown in the examples, there is a large degree of freedom regarding the concentration of holes serving as charge carriers, that is, the charge concentration.

[Brief explanation of drawings]

1 to 4 are graphs showing the X-ray diffraction patterns of superconductors in Examples, respectively, where 26 on the horizontal axis is the diffraction angle, and ■ on the vertical axis is the diffraction intensity (number of counts).

Claims (1)

[Claims] (1) A superconductor represented by the following general formula. (La_1_-_p_-_qα_pβ_q)_xCuO
_y However, 0.2<p<0.8 0.025<q<0.25 1.8<x<2.2 3.6<y<4.1 α: selected from Sm, Eu and Gd At least one element β: at least one element selected from Sr and Ba (2) A superconductor represented by the following general formula. (La_1_-_p_-_qα_pβ_q)_xCuO
_y However, 0.2<p<0.8 0.025<q<0.25 1.8<x<2.2 3.6<y<4.1 α: selected from Sm, Eu and Gd At least one element β: at least two elements selected from Ca, Sr and Ba (3) A superconductor represented by the following general formula. (La_1_-_p_-_qα_pβ_q)_xCuO
_y However, 0.2<p<0.8 0.025<q<0.25 1.8<x<2.2 3.6<y<4.1 α: At least 1 selected from Eu and Gd Seed element β: at least one element selected from Ca, Sr, and Ba