A ceramic superconductivity part, such as a wire, is produced through the partial oxidation of a specially formulated copper alloy in a core. The alloys contains low level of quantities of rare earth and alkaline earth dopant elements. Upon oxidation at high temperatures, and superconducting oxide phases are formed as a thin film

Smialek, James L.

English

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Serial No: 07/458,467 
Filed: 12/28/89 
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https://ntrs.nasa.gov/search.jsp?R=19900008138 2020-03-19T23:57:52+00:00Z
LEW-14,676-2 
AWARDS ABSTRACT 
Method of Forming Lou Cost, Formable 
High T, Superconducting Wire 
A ceramic superconductivity part, such as a wire 10, is produced 
through the partial oxidation of a specially formulated copper alloy in 
a core 12. The alloys contain low level quantities of rare earth and 
alkaline earth dopant elements. Upon oxidation at high temperatures, 
superconducting oxide phases are formed as a thin film 14. 
INVENTOR : James L. Smialek 
EMPLOYER: NASA Lewis Research Center 
EVALUATOR: Salvatore J. Grisaffe 
SERIAL NO.: 458,467 
FILED: December 28, 1989 
LEW-14,676-2 
10 
12 
14 
NASA Case No. LEW-14,676-2 PATENT 
Method of Forming Lou C o s t ,  Formable, 
High T, Superconducting Wire 
Origin of the Invention 
The invention described herein was made by an employee of the United 
States Government and may be manufactured and used by or  for the 
Government €or  governmental purposes without the payment of any royalties 
5 thereon or  therefor. 
Statement of Copendency 
This application is a division of application serial No. 305,675 
which was filed January 31, 1989. 
Technical Field 
10 This invention is concerned with forming high T, superconductive 
ceramic oxide films. The invention is particularly directed to producing 
completely formable superconducting articles. 
In the prior art the production of ceramic superconductors involves 
sintering, hot pressing, o r  hot isostatic pressinp ceramic oxide powders. 
15 The disadvantage of utilizing any of these methods is that the production 
o f  complex articles, such as lonq, fine wire, is totally precluded. 
To produce superconducting wire it has been suggested that plasma 
spraying, chemical vapor deposition, or  physical vapor deposition be 
utilized. It has also been suggested that fibers be drawn from molten 
20 oxide o r  organic precursor liquids. In another process, superconducting 
oxide powders are encapsulated in ductile metal tubing which is extruded 
into wire. While superconducting wire is potentially produced, a 
considerable degree of extra cost and effort is involved in coating, fiber 
drawing, or encapsulatinq. Furthermore, the total degree of fabricability 
25 in actual industrial applications, as opposed to laboratory 
demonstrations, still needs to be verified. 
It has been further suggested that special copper alloys be fully 
oxidized resulting in special oxide phases exhibiting superconductivity. 
This approach is somewhat unconventional in that relatively ductile copper 
30 alloy may indeed be fully formed. Then the alloy must be completely 
oxidized to form superconducting oxides of the R-A-Cu-0 type, where R is 
a rare earth element, and A is an alkaline earth element. However, some 
compositional limitations exist. Y, a commonly used superconducting 
component element in Y.Ba2Cuj07_, superconductors, is immiscible in Y-Cu 
5 melts. Therefore, a homogeneous Y-Ra-Cu alloy is precluded as would be 
any subsequent YiBalCujOl_x superconducting phase. 
A more serioiis disadvantage is that once the article is oxidized in 
the superconducting phase, it is entirely a brittle ceramic material. 
Therefore, a fully processed ceramic wire would not be amenable to the 
10 flexibility in the field normally associated with metal wire. Any 
processing following the oxidation step would be subject to the 
limitations concomitant with those of  a brittle material. To circumvent 
this limitation, the R-A-Cu metal is preformed in a noble metal composite 
such as silver. This material and process are quite costly. 
15 It is, therefore, an object of the invention to process 
superconducting articles, especially in wire form, without encountering 
the problems of poor ductility o r  complicated processing normally observed 
for the superconducting ceramic oxides. 
Background A r t  
20 U.S. patent No. 3,243,871 to Saur is directed to a method of making 
ductile superconductors. Pertinent steps in this process include cold 
drawing a wire and then cold working the wire. The wires are then heated 
to form NbjSn on the surface. 
U . S .  patent No. 4,171,464 to Steyert is concerned with a high 
25 specific heat superconducting composite material. This material includes 
a high specific heat ceramic in a metal conductor. 
U.S. patent No. 4,339,508 to Tsuya et a1 describes a method for 
manufacturing a thin and flexible ribbon of supercondiicting material. The 
raw superconducting material is heated to a temperature between its 
melting point and 3OOOC above the melting point and then ejecting the melt 
through a nozzle against a cooling surface of a moving substrate such as 
a rotating drum. 
30 
U . S .  patent No. 4,411,959 to Braginski et a1 is related to a 
submicron-particle ductile superconductor. The submicron particles of 
3 
superconductor are encapsulated in a metal tube and then fabricated down 
to a fine wire in the absence of sintering or reacting annealing, thereby 
avoiding the problems associated with the formation of brittle core o r  
filaments. 
5 Disclosure of Invention 
The problems of the prior art may be solved and the object achieved 
by the present invention. Ceramic superconductivity parts are produced 
through the partial oxidation of a specially formulated copper alloy. The 
alloys contain low level quantities of rare earth and alkaline earth 
10 dopant elements. Therefore, upon osidation at high temperatures, the 
superconducting oxide phases may be formed as thin films. 
Problems encountered in the prior art have been addressed in that 
the process of the present invention has the ability to produce wire 
confj gurations rather than just bulk solids. Also the process exhibits 
15 an ease in forming oxide films without the expense of a separate 
complicated coating step. The present invention further illustrates the 
ease of metal wire fabrication compared to ceramic fibers, and it has the 
ability to form composite wires into useful devices after partial 
conversion to the oxide phases. The invention gives more flexibility in 
20 alloy design because lower levels of rare earth and alkaline earth 
additions are needed. The invention avoids immiscibility problems at high 
Y-Cu concentrations, while avoiding mechanical forming problems caused by 
high R-A contents. 
Brief Description of the Drawing 
25 The advantages and novel features of the invention will be more 
fully apparent from the following detailed description when read in 
connection with the accompanyinE drawing which is an enlarged cross- 
section view of an oxidized Y-Ba-Cu wire produced in accordance with the 
present invention. 
30 Best Mode f o r  Carrying Out the Invention 
Referring now to the drawing there is shown a superconducting 
article, such as a coated wire 10, that is produced in accordance with 
the present invention by a partial oxidation of the specially formulated 
4 
copper alloyed core 1 2 .  The alloy contains low level quantities of rare 
earth and alkaline earth elements .Moreparticular1yup toten atom percent 
of rare earth and alkaline earth dopants can be used in alloying the 
copper core 1 2 .  By way of example, yttrium and barium may be alloyed with 
5 the copper core 1 2 .  
A wire core 12 having a diameter of about 20 p m is believed to be 
satisfactory. Upon oxidation at high temperatures, superconducting oxide 
phase!;, such as YiBa2Cu307,,, are formed as thin films 1 4 .  Yttrium and 
barium will be preferentially oxidized with respect to the copper base 
10 element, even at low alloying levels, because Y and Ba are 
thermodynamically much more oxygen-active than is copper. 
An analogous situation exists for NiCrAl + Zr alloys having about 
ten atom percent aluminum and about one atom percent zirconium. In this 
example, high temperature oxidation produces A1203 + Z r O Z  scales to the 
1 5  exclusion of NiO or  Cr20j. Thus films of any desired R-A-Cu-0 
superconducting phase can be produced on copper alloys by the proper 
selection of dopant levels and oxidation conditions. 
An important advantage of utilizing the thin film 14 structure of 
the superconductor material is that such a form is extremely compliant in 
20 any type of post-processing fabrications steps. By way of example, such 
steps may include coiling or  bending, as might be required for winding 
motor coils or  installing power transmission lines. Therefore, the 
limitation of post-processing brittleness associated with prior art 
materials are avoided. 
25 However, it is apparent that thin copper wires should be used so 
that the thin superconducting oxide films constitute a considerable 
fract:ion of the wire cross-section. By way of example, an oxide film 14 
having a thickness between 5 1.1 m and 20 1.1 m is easily formed in oxidation 
and its thicknesses sufficiently thin to be flexible. 
30 A copper wire radius of 20 p m would amount to only 44% of the total 
cross-section. This results in a substantial portion of the cross- 
sectional area being available for superconducting current. 
A full bundle of coated wires as shown in the figure could transmit 
a large current as in the case of conventional electrical transmission. 
35 
5 
5 
10 
15 
20 
It is apparent that should loss of cryogenic fluid occur some conductivity 
would still be maintained tlirouqh the copper wire substrate 12. 
Alternate Embodiment of the Invention 
It is further contemplated that alloying elements other than yttrium 
and barium may be utilized to form the superconducting phase. More 
particularlv, lanthanum, or rare earth elements, such as ytterbium, 
europium and gadolinium, may be used as alloying elements instead of 
yttrinm. Also, strontium, bismuth, and thallium may be substituted for 
barium. 
Other elements may be required to assist in the exclusive formation 
of R-A-Cu-0 during oxidation. Silicon, chromium, and aluminum may be used 
for this purpose. 
It is further contemplated that oxidation exposures may require 
adjustment to precisely control and optimize the superconducting films. 
For example, H;, HZO, or F gases may be utilized to produce beneficial 
atmospheric modifications. 
While several embodiments of the invention have been described, it 
will be apparent that various modifications may be made to the procedural 
steps the invention without departing from the spirit thereof or the scope 
of the subjoined claims. 
ABSTRACT OF TEE DISCLOSURE 
Method of Forming Lou Cost, Formable, 
T, Superconducting Wire 
A ceramic superconductivity part, such as a wire 10, is produced 
5 through the partial oxidation of a specially formulated copper alloy in 
a core 12. The alloys contain low level quantities of rare earth and 
alkaline earth dopant elements. Upon oxidation at high temperatures, 
superconducting oxide phases are formed as a thin film 14. 


Method of forming low cost, formable High T(subc) superconducting wire

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