Superconductor technology: apparatus – material – process – Processes of producing or treating high temperature... – Using magnetic field
Reexamination Certificate
1988-03-23
2001-09-18
Derrington, James (Department: 1731)
Superconductor technology: apparatus, material, process
Processes of producing or treating high temperature...
Using magnetic field
C505S490000, C505S727000, C505S739000, C505S822000, C264S428000, C264S434000
Reexamination Certificate
active
06291403
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention generally relates to the field of superconducting ceramics and particularly to manufacturing methods for making superconducting ceramics under a magnetic field.
It has long been known that metals such as mercury and lead, intermetallics such as NbNd, Nb
3
Ge and NbGa and ternary materials such as Nb
3
(Al
0.8
Ge
0.2
) demonstrates superconductivity. However, the transition temperature of such long known conventional superconducting materials cannot exceed 25° K.
In more recent years, superconducting ceramics have attracted widespread interest. A new material was first reported by researchers at the Zurich laboratory of IBM Corp. as Ba—La—Cu—O-type high temperature superconducting oxides. Subsequently, La—Sr—Cu(II)-O-type superconducting oxides were also proposed. Another type of superconducting material that has been found is (YBa
2
)Cu
3
O
6-8
. By virtue of the fact that these superconducting ceramics form a quasi-molecular atomic unit in a crystalline structure whose unit cell is constructed with one layer in which electrons have essentially one-dimensional motion, whereas three dimensional electron condition occurs in the long known materials mentioned above, higher transition temperatures were achieved.
Much work has been undertaken by researchers in the field who have endeavoured to elevate Tco, the temperature at which resistance vanishes, above the levels previously obtained and preferably above the boiling point of nitrogen (77° K) or even higher. As described in our European Patent Application No.87309081.5, we have investigated superconducting ceramic materials having the stoichiometric formulae (A
1−x
B
x
)
y
Cu
z
O
w
, where A represents one or more elements of Group IIIa of the Periodic Table, e.g., the rare earth elements, and B represents one or more elements of Group IIa of the Periodic Table, e.g. the alkaline earth elements including beryillium and magnesium, and in the continuation of these investigations we have disclosed that the existence of voids and grain boundaries in superconducting ceramic materials makes it difficult to obtain an elevated Tco.
OBJECTS AND SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide superconducting ceramics having a higher transition temperature than hitherto and to manufacture superconducting ceramics substantially devoid of imperfection.
Whereas in previous attempts to find higher Tc superconducting materials attention has been focussed upon the composition or molar ratios of the constituent elements, in accordance with the present invention there is principally provided an improved process for the manufacture of superconducting ceramics in accordance with which, during the formation of superconducting structure, that is to say the chemical compounds which are mixed together to form the superconducting ceramics, a magnetic field is applied to thereto. The magnetic field is preferably applied in the direction normal to the (a,b) plane. The strength of the applied magnetic field is preferably not lower than 500 Gauss, e.g. 100,000 Gauss. By virtue of the magnetic field the ceramic mixture is given a special orientation in which the atomic arrangement is ordered and made more simple, e.g. on the (a,b) plane, so that few grain boundaries and imperfections exist in the final ceramic material. Accordingly, the higher transition temperature is obtained, and therefore the superconducting ceramics are endowed with a higher critical current. For example, the Tc onset is elevated to 50-107K and the critical current is elevated 10
5
to 10
6
A/cm
2
much higher than prior art has obtained on the order of 10
2
A/cm
2
. The fundamental concept of the present invention is based on the combination effect of the diamagnetism of superconductor and the current induced by the applied magnetic field.
Other feature of the invention are set forth with particularity in the appended claims and will become clear to those possessed of the relevant skills form consideration of the following description of exemplary embodiments.
REFERENCES:
patent: 4963524 (1990-10-01), Yamazaki
patent: 4975411 (1990-12-01), Danby et al.
patent: 5096880 (1992-03-01), Rybka
patent: 5841795 (1983-03-01), None
patent: 58217493 (1983-12-01), None
patent: 60221392 (1985-11-01), None
Brodsky et al, High-Temperature Superconductors, Symposium Held Nov. 30-Dec. 4, 1987, Boston, Mass., Materials Research Society, vol. 99.*
Patent Abstracts of Japan, vol. 7, No. 122 (C-168) (1267), May 26, 1983; & JP-A- 58 41 795 (Hitachi) Nov. 3, 1983 *abstract*.
Zietscherift Fuer Physik B—Condensed Matter, vo. 64, pp. 189-194, Springer-Verlag 1986; J.G. Bednorz, et al.: “Possible High Tc Superconductivity in the Ba-La-Cu-O System” *abstract*.
Patent Abstracts of Japan, vol. 10, No. 90 (C-337) (2147), Apr. 8, 1986; & JP-A-60 221 392 (Toshiba) Jun. 11, 1985 *abstract*.
Costellia Jeffrey L.
Derrington James
Nixon & Peabody LLP
Semiconductor Energy Laboratory Co,. Ltd.
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