Superconductor technology: apparatus – material – process – High temperature – per se – Copper containing
Reexamination Certificate
2001-09-26
2004-07-27
Kopec, Mark (Department: 1751)
Superconductor technology: apparatus, material, process
High temperature , per se
Copper containing
C505S120000, C505S121000, C505S470000, C505S500000
Reexamination Certificate
active
06767866
ABSTRACT:
TECHNICAL FIELD
This invention relates to a selective reduction type, high temperature superconductor, which is a copper (Cu) oxide, high temperature superconductor that permits doping with positive holes by selectively reducing constituent elements (atoms). This superconductor can be used in large scale superconducting power transmission, superconducting power storage or reserve, superconducting electronics such as a high performance Josephson device, a high frequency device or the like. The invention also relates to methods of making such a superconductor.
BACKGROUND ART
Conventional Cu-oxide family, high temperature superconductors have been prepared doping with positive holes, by oxidation, to raise the contents of the superconducting carriers. Such a high temperature superconductor, however, may cause the carriers to reduce in concentration due to diffusion or bleeding of oxygen atoms by increased temperature. This leads to a depletion in superconductivity of the superconductor.
Also, doping with positive holes to obtain a higher carrier concentration has been thought to require a higher oxygen partial pressure, and it has so far been unattainable to prepare a superconductor of the type described by doping with positive holes to raise the carrier concentration in a reduction process conditioned under low partial pressure or vacuum. Since it has been found impossible to increase the concentration of positive holes by reduction, i.e., by lowering the oxygen partial pressure, the conventional high temperature superconductors have the problem that they have a limited carrier concentration and are thus low and unsatisfactory in their superconducting properties that include the critical temperature Tc, critical current density Jc, irreversible magnetic filed Hirr. It has therefore been sought to, solve the problem of bringing into realization a high temperature superconductor of a reduced oxygen concentration.
With these problems taken into account, it is accordingly a first object of the present invention to provide a selective reduction type, high temperature superconductor that permits doping with positive holes by selectively reducing constituent elements (atoms).
Another object of the present invention is to provide a method of making a selective reduction type, high temperature superconductor.
DISCLOSURE OF THE INVENTION
In order to achieve the first object mentioned above, there is provided in accordance with the present invention, a selective reduction, high temperature superconductor, wherein it has a portion of its constituent elements selectively reduced whereby it has a superconducting layer thereof doped with positive holes.
The present invention also provides a selective reduction type, high temperature superconductor that has a portion of its constituent elements selectively reduced whereby there are formed in superconducting layers a first and a second region doped overly and doped optimally with superconducting carriers, respectively.
The present invention further provides a selective reduction type, high temperature superconductor that has a portion of its constituent elements selectively reduced whereby the superconductor as a whole has a superconducting carrier concentration such that it is held doped overly or doped optimally with superconducting carriers.
The present invention also provides a selective reduction type, high temperature superconductor that has on each of an upper and a lower surface of a unit lattice thereof a charge supply layer having each of a portion of Cu atoms substituted with a selectively reducible atom.
The present invention also provides a selective reduction type, high temperature superconductor in which the said superconducting layers have an upper and a lower surface constituted by a CuO
2
layer of 5-coordination and a layer other than the upper and lower constituted by a CuO
2
layer of 4-coordination, the said CuO
2
layer of 5-coordination and 4-coordination having been over- and optimum-doped, respectively, by selective reduction.
Further, the present invention provides a selective reduction type, high temperature superconductor having a selectively over-doped and/or a selectively optimum-doped construction.
The present invention further provides a selective reduction type, high temperature superconductor, characterized in that it is made of a (Cu, M) group, high temperature superconducting material, which can be described by composition formula:
Cu
1−x
M
x
(Ba
1−y
,Sr
y
)
2
(Ca
1−z
L
z
)
n−1
Cu
n
O
2n+4−w
where M represents ions of one or more polyvalent metallic elements selected from the class which consists of Tl, Bi, Pb, In, Ga, Sn, Ti, V, Cr, Mn, Fe, Co, Ni, Zr, Nb, Mo, W, Re and Os; L represents one or more elements selected from the class which consists of Mg and alkaline metallic elements; 0≦x≦1.0; 0≦y≦1; 0≦z≦1; 0≦w≦4; and 1≦n≦16.
The present invention also provides selective reduction type, high temperature superconductor, characterized in that it is made of a (Cu, Tl) group, high temperature superconducting material that can be described by composition formula:
Cu
1−x
Tl
x
(Ba
1−y
Sr
y
)
2
(Ca
1−z
L
z
)
n−1
Cu
n
O
2n+4−w
where L represents one or more elements selected from the class which consists of Mg and alkaline metallic elements; 0≦x≦1.0; 0≦y≦1; 0≦z≦1; 0≦w≦4; and 1≦n≦16.
The present invention also provides a selective reduction type, high temperature superconductor, characterized in that it is made of a (Cu, Tl) group, high temperature superconducting material that can be described by composition formula:
Cu
1−x
Tl
x
(Ba
1−y
Sr
y
)
2
(Ca
1−z
L
z
)
2
Cu
3
O
10−w
where L represents one or more elements selected from the class which consists of Mg and alkaline metallic elements; 0≦x≦1.0; 0≦y≦1; 0≦z≦1; and 0≦w≦4.
The present invention also provides a selective reduction type, high temperature superconductor, characterized in that it is made of a high temperature superconducting material that can be described by composition formula:
Cu
1−x
Tl
x
(Ba
1−y
Sr
y
)
2
(Ca
1−z
L
z
)
3
Cu
4
O
12−w
where L represents one or more elements selected from the class which consists of Mg and alkaline metallic elements; 0≦x≦1.0; 0≦y≦1; 0≦z≦1; and 0≦w≦4.
The present invention further provides a selective reduction type, high temperature superconductor, characterized in that selective over- or optimum-doping is effected by decrease in the valence number of ions of a constituent element by decrease in the oxygen concentration, that is by selective reduction, or by varying (increasing or decreasing) oxygen concentration.
The present invention also provides a selective reduction type, high temperature superconductor, characterized in that it is a selectively over-doped type or a selectively optimum-doped type, high temperature superconductor in which n is any one of 3, 4, 5, 6 and 7.
The present invention further provides a selective reduction type, high temperature superconductor having a construction that the reduction of selectively reducible ions causes the ions in the charge supply layers to receive electrons in their outer shell orbits, thereby providing holes in the CuO
2
layer of 5-coordination of a said superconducting layer.
The present invention further provides a selective reduction type, high temperature superconductor having a construction that it has a superconducting anisotropy of not greater than 10 and a coherence distance of not less than 3 angstroms.
The present invention further provides a selective reduction type, high temperature superconductor having a construction that said selective reduction transforms its natural superconducting wave function that is of a d-wave high in spatial anisotropy to a wave function of a (d+is) wave that has also a property of an s-wave lacking of spatial anisotropy.
A selective reduction type, high temperature superconductor so constructed as mentioned
Japan Science and Technology Agency
Kopec Mark
Westerman Hattori Daniels & Adrian LLP
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