JP3205996B2 - Superconductor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a nuclear fusion reactor, a magnetic fluid generator, an accelerator, a rotating electric device (such as a motor or a generator), a magnetic separator, a magnetic levitation train, and a magnetic levitation. Suitable as magnet coil materials for automobiles, magnetic levitation elevators, nuclear magnetic resonance tomography diagnostic equipment, magnetic propulsion ships, electron beam exposure equipment, single crystal manufacturing equipment, various experimental equipment, etc. Also, transmission lines, electric energy storage, Suitable for applications where power loss is a problem, such as transformers and rectifiers.In addition, Josephson elements, SQUID elements,
The present invention relates to a superconductor suitable as various elements such as a superconducting transistor and a superconducting microwave three-dimensional circuit, and further as various functional materials such as an infrared detecting material and a magnetic shielding material.

<Prior Art> Conventionally, about 20 types of copper composite oxide superconductors having different crystal structures have been found. When the crystal structure of these copper composite oxide superconductors is further subdivided, the repeating units of the crystal structure can be classified into a CuO ₂ layer and other units.
In addition, other than the CuO _Z layer, “Physica C”, 167, 5th
As described on page 15 (1990), it can be classified into a blocking layer and a mediating layer according to the thickness of the layer in the direction perpendicular to the CuO ₂ layer (c-axis direction). Thus, the blocking layer has different La ₂ O ₂ type, BaO / CuO / BaO type, BaO / CuO / CuO /
BaO type, SrO / Bi ₂ O ₂ / SrO type, BaO / Tl ₂ O ₂ / BaO or BaO / T
lO / BaO type, SrO / PbO-Cu-PbO / SrO type, SrO / (Pb, Cu) O / S
rO or SrO / (Pb, Sr) O / SrO type, Ln ₂ O ₂ type (Ln is Nd, S
m, Eu and Gd).

When examining the lattice constant (a-axis length or b-axis length) of the conventional copper composite oxide superconductor in a direction parallel to the CuO ₂ plane, it differs depending on the type of the blocking layer. CuO ₂
Expressing the crystal size in the direction parallel to the plane as the distance between Cu in the CuO ₂ plane and O closest to it, 1.89 to 1.89.
It is distributed over 97Å.

When a copper composite oxide superconductor is used, it is convenient if superconductors having different superconducting transition temperatures can be integrally used. For example, when configuring various elements and sensors, new effects can be expected if layers having different superconducting transition temperatures can be integrally arranged in layers. However, the common use of superconductors with different types of blocking layers is the inconsistency of the crystal size in the direction parallel to the CuO ₂ plane and the constituent elements from one superconductor to the other during fabrication. Difficult because of the spread of Therefore, it includes a blocking layer of the same type,
It is desired to obtain a plurality of types of superconductors having different superconducting transition temperatures.

For example, the Y ₁ Ba ₂ Cu ₃ O _7-z superconductor has a BaO / CuO / BaO type blocking layer and a superconducting transition temperature of about 90K, but the copper complex oxide superconductivity conventionally found BaO / in the body
This is the only one having a CuO / BaO type blocking layer, and it is difficult to share it with other superconductors, and the range of use is limited.

<Problem to be Solved by the Invention> An object of the present invention is to include a blocking layer of the same type (BaO / CuO / BaO type) as a Y ₁ Ba ₂ Cu ₃ O _7-z superconductor and to match the same. Another object of the present invention is to provide a copper composite oxide superconductor having a different superconducting transition temperature and being easy to use in common.

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

｛(Ba _1-p Sr _p ) _1-q α _q ｝ ₂ Cu ₂ O _s where α: an element selected from La and Pb 0 ≦ p ≦ 0.2 0.3 ≦ q ≦ 0.5 4.0 <s ≦ 4.8 This is referred to as a first invention.

Further, the present invention provides a superconductor represented by the following general formula.

_{{(Ba 1-t Sr t} ) 1-u α u} 2-v {β 1-w (Ca 1-x Sr x) w} 2 + v Cu 4 O y , however, alpha: selected from La and Pb Elements β: Y, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu
0 ≦ t ≦ 0.2 0 <u ≦ 0.50 ≦ v <0.20 ≦ w ≦ 0.50 ≦ x <0.2 8.5 <y ≦ 9.0 An element selected from the following is referred to as a second invention.

In the first and second inventions, α and β are each only 1
A species may be selected, or two or more types may be selected.

The superconductors of the first and second inventions are shown in FIGS.
It has a crystal structure as shown in the figure, and is formed of a layer composed of (Ba, Sr, α) and oxygen, a layer composed of Cu and oxygen, and a layer composed of (Ba, Sr, α) and oxygen. It contains a CuO / BaO type blocking layer.

Now, when the structure is ideally realized, the superconductor of the first invention has s of 5.0 in the general formula. However, since the structure is liable to cause oxygen deficiency, the superconductor usually has a composition of 4.0 <s ≦ 4.8. Range is allowed. For p, Ba and Sr
From the solid solution limit of, a restriction of 0 ≦ p ≦ 0.2 is added.

In the superconductor according to the first aspect of the present invention, electric charges are provided by holes. When a charge is given by holes as described above, the superconductor becomes a superconductor when the hole concentration is 0.01 or more and 0.5 or less per Cu, similarly to the conventional copper composite oxide superconductor. Then, since the hole concentration per Cu is given by sq-4, it must be 2.01 <sq-2 <2.50.
Preferably, 2.10 <sq-2 <2.30. However,
The valence of each element is La + 3, Ba and Sr + 2, and O is −
Bivalent. Further, since the valence of Pb can take +2 valences and +4 valences, it is considered as a mixed valence of +2 valences and +4 valences.
Trivalent.

In order to easily satisfy the constraint of 2.01 <sq−2 <2.50, it is preferable that s is smaller than the value when the structure is ideally realized.

Further, q is restricted by 0.3 ≦ q ≦ 0.5 in order to reduce the excess holes in order to stabilize the structure shown in FIG.

The lattice constant in the ab plane direction of the crystal structure of the superconductor of the first invention differs depending on the type of the element α, the composition ratio of each element, and the oxygen content (s). It may be slightly different between the a-axis direction and the b-axis direction because it is tetragonal, but it is about 3.8 °, which is 1.9 ° when expressed as the distance between Cu in the CuO ₂ plane and O closest to it. , Y ₁ Ba ₂ Cu ₃ O _7-z , which is almost the same as that of the above, and has good consistency. The c-axis length of the lattice constant is about 8.3 °.

Next, when the structure of the superconductor of the second invention is ideally realized, y is 9.0 in the general formula. However, similarly to the first invention, the superconductor is apt to cause oxygen deficiency. , 8.5 <y ≦ 9.0. Also, B
The solid solution limits of a and Sr are the same as in the first invention, with the additional restriction that 0 ≦ t ≦ 0.2.

The superconductor of the second invention is also provided with electric charges by holes, and becomes a superconductor when the hole concentration is 0.01 or more and 0.5 or less per Cu, similarly to the conventional copper composite oxide superconductor. Then, the hole concentration per Cu is y / 2− (2 + u) × (2
−v) / 4− (3-W) × (2 + v) / 4−2, so 2.01 <y / 2− (2 + u) × (2-v) / 4− (3-
W) × (2 + v) / 4 <2.50. Preferably, 2.10 <y / 2- (2 + u) × (2-v) / 4- (3-
W) × (2 + v) / 4 <2.30. However, the valence of each element is La +3, Ba, Sr and Ca +2, Y, Nd, Sm,
Eu, Gd, Dy, Ho, Er, Tm, Tb, and Lu were +3 valences, and O was -2 valences. Further, since the valence of Pb can take +2 valence and +4 valence, it is considered to be a mixed valence of +2 valence and +4 valence, and is set to +3 valence on average.

2.01 <y / 2- (2 + u) × (2-v) / 4- (3-W)
In order to easily satisfy the restriction of × (2 + v) / 4 <2.50, it is better that y is close to the value when the structure is ideally realized.

As shown in FIG. 2, the element β must have a small ionic radius of about 1 ° in order to prevent oxygen from being present in the plane (ab plane) where it exists. From this condition, the element β is Y, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm,
It must be selected from Tb and Lu, but Y, Dy, Ho, Er, and Yb are preferable for stabilizing the structure. Further, from the solid solution limit of the element β and Ca and Sr, 0 ≦ w ≦ 0.
Five restrictions are added.

Further, u, v, and x are respectively 0 <u ≦ 0.5, 0 ≦ v <0.2, 0 in order to stabilize the structure shown in FIG.
A restriction of ≦ x <0.2 is imposed.

The lattice constant in the ab plane direction of the crystal structure of the superconductor of the second invention also differs depending on the types of the elements α and β, the composition ratio of each element, and the oxygen content (y), and the crystal slightly deviates from the tetragonal crystal. it may be slightly different in the beveled method crystal in the a-axis direction and the b-axis direction Te, but about 3.8 Å, Cu in CuO ₂ plane this
The distance between the superconductor and the closest O is 1.9 °, which is almost the same as that of the Y ₁ Ba ₂ Cu ₃ O _7-z superconductor and the superconductor of the first invention. Good consistency. The c-axis length of the lattice constant is about 15.1 °.

The superconductor of the present invention can be used in various forms such as a tape, a wire, a fiber, and a sheet. Further, it can be formed on a reinforcing wire made of carbon fiber or a metal such as ceramics, gold, and silver, and used.
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,
Formed as a thin film on a substrate such as Si, MgO, LaGaO ₃ , LaAlO ₃ , SrTiO ₃ and used as various devices or LSI
Wiring.

When the superconductor of the present invention is used in combination with a refrigerator utilizing the Peltier effect or the like, handling becomes simple.

The superconductor of the present invention can be manufactured by various methods.

For example, a well-known powder mixing method can be used. In addition, various deposition methods such as an electron beam evaporation method and a laser evaporation method, which can control stacking in an atomic order,
Various sputtering methods such as a magnetron sputtering method can be used. A chemical vapor deposition method using a halide, an organic metal, or the like, an atomization method using a nitrate or an organic acid, or a coating method using an alkoxide can also be used.

<Examples> Example 1 Ba: Sr: La: Pb: Cu is 1.24: 0.065: 0.07: 0.63: BaCO ₃ , SrCO ₃ , La ₂ (CO ₃ ) ₃ .xH ₂ O, PbO, CuO It was weighed to 2.0, crushed and mixed in an agate mortar, placed in an Al ₂ O ₃ container, and calcined in air at 900 ° C. for 12 hours. Then, the mixture is again pulverized in an agate mortar, mixed and formed into pellets.
After baking for days, it was quenched. The pellets thus obtained were further heat-treated in air at 400 ° C. for 2 hours and then quenched.

A part of the obtained pellet was pulverized, and the crystal structure was analyzed by a powder X-ray diffraction method. As a result, the crystal structure was as shown in FIG. At this time, when the lattice constant was obtained,
a = 3.85 ° and c = 8.2 °. When this a-axis length is expressed as the distance between Cu in the CuO ₂ plane and O closest to it, it is 1.93Å, which is almost the same as that of the Y ₁ Ba ₂ Cu ₃ O _7-z superconductor, Excellent consistency with it.

The composition is ｛(Ba _0.95 Sr _0.05 ) _0.65 (La _0.1 Pb _0.9 )
_0.35 ｝ ₂ Cu ₂ O _4.6 , and the superconducting transition temperature was 15K.

Example 2 BaCO ₃ , SrCO ₃ , La ₂ (CO ₃ ) ₃ .xH ₂ O, PbO, Ho ₂ O ₃ , Ca
Ba: Sr: La: Pb: Ho: Ca: Cu is 1.44: 0.16 for each powder of CO ₃ and CuO:
It was weighed so as to be 0.02: 0.36: 1.26: 0.76: 4.0, crushed and mixed in an agate mortar, put in an Al ₂ O ₃ container, and calcined in the air at 900 ° C. for 12 hours. Then, again pulverized in an agate mortar, mixed, formed into pellets, oxygen partial pressure is 0.
After sintering at 900 ° C. for 3 days under an atmosphere of 1 atm or less, it was rapidly cooled. The pellets thus obtained were further subjected to an oxygen-argon mixed gas atmosphere with an oxygen partial pressure of 5 atm.
After heat treatment at 0 ° C. for 2 hours, it was gradually cooled.

A part of the obtained pellet was pulverized, and the crystal structure was analyzed by a powder X-ray diffraction method. The result was a crystal structure shown in FIG. At this time, when the lattice constant was obtained,
a = 3.85 ° and c = 15.0 °. When this a-axis length is expressed as the distance between Cu in the CuO ₂ plane and O closest to it, it is 1.93Å, which is almost the same as that of the Y ₁ Ba ₂ Cu ₃ O _7-z superconductor. Excellent in consistency.

The composition is ｛(Ba _0.95 Sr _0.05 ) _0.8 (La _0.05 P
b _0.95 ) _0.2 ｝ _1.9 ｛Ho _0.6 (Ca _0.9 Sr _0.1 ) _0.4 ｝ _2.1 Cu ₄ O
_8.95 and the superconducting transition temperature was 70K.

Example 3 A CuO powder was formed into a pellet and fired at 900 ° C. for 5 hours to obtain a sintered body. Moreover, SrCO ₃ , BaCO ₃ , La ₂ (CO ₃ ) ₃
XH ₂ O, PbO, each powder of CuO Sr: Ba: La: Pb: Cu 0.81: 0.0
4: 0.13: 0.02: 1.0, weighed and mixed to form pellets, baked at 900 ° C for 5 hours, and the composition was Sr _0.81 Ba
_A sintered body of _0.04 La _0.13 Pb _0.02 Cu ₁ O _x was obtained. Similarly, Er ₂
Each of O ₃ , CaCO ₃ , SrCO ₃ , and CuO powders contains Er: Ca: Sr: Cu 0.7: 0.
27: 0.03: 1.0, weighed and mixed, molded into pellets, and baked at 800 ° C for 5 hours, the composition was Er _0.7 Ca _0.27 Sr
_A sintered body of _0.03 Cu ₁ O _x was obtained.

Next, the above three types of sintered bodies were respectively targets,
, And vapor deposition was performed using an ArF excimer laser. That is, the target and the SrTiO ₃ substrate are placed in a vacuum chamber, the substrate is heated, and while exposing a small amount of O ₂ gas and N ₂ O gas, an excimer laser is used as a target,. .. Were repeatedly applied to cause abrasion to form layers of each composition on the substrate, thereby forming a thin film.

When the crystal structure of the obtained thin film was analyzed,
The structure was as shown in FIG. When the lattice constants were determined, a was 3.85 ° and c was 15.0 °. This a-axis length is
Expressed as the distance between Cu in the CuO ₂ plane and O closest to it, it is 1.93Å, which is almost the same as that of the Y ₁ Ba ₂ Cu ₃ O _7-z superconductor, and has excellent matching with it. I have.

The total composition of the thin film is ｛(Ba _0.95 Sr _0.05 )
_0.85 (La _0.9 Pb _0.1 ) _0.15 ｝ ₂ ｛Er _0.7 (Ca _0.9 S
r _0.1 ) _0.3 ｝ ₂ Cu ₄ O _8.95 , and the superconducting transition temperature was 60K.

<Effect of the Invention> As shown in the examples, the superconductor of the present invention has the same type (BaO / CuO / Ba) as the conventional Y ₁ Ba ₂ Cu ₃ O _7-z superconductor.
It has a crystal structure including an (O-type) blocking layer, and has not only good compatibility with this but also a superconducting transition temperature that is different from that, making it easy to share.

[Brief description of the drawings]

FIG. 1 and FIG. 2 are model diagrams of the crystal structure of the superconductor of the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C01G 1/00 CA (STN) REGISTRY (STN) WPI (DIALOG)

Claims (2)

(57) [Claims] 1. A superconductor containing a copper composite oxide represented by the following general formula as a main component. ｛(Ba _1-p Sr _p ) _1-q α _q ｝ ₂ Cu ₂ O _s where α: an element selected from La and Pb 0 ≦ p ≦ 0.2 0.3 ≦ q ≦ 0.5 4.0 <s ≦ 4.8 2. A superconductor containing a copper composite oxide represented by the following general formula as a main component. _{{(Ba 1-t Sr t} ) 1-u α u} 2-v {β 1-w (Ca 1-x Sr x) w} 2 + v Cu 4 O y , however, alpha: selected from La and Pb Β: an element selected from Y, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu 0 ≦ t ≦ 0.2 0 <u ≦ 0.5 0 ≦ v <0.2 0 ≦ w ≦ 0.5 0 ≦ x <0.2 8.5 <y ≦ 9.0