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

Smialek, James L.

English

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United States Patent [191 [ i l l  Patent Number: 5,049,539 
Smialek [45] Date of Patent: Sep. 17, 1991 
[54] LOW COST, FORMABLE, HIGH TC 
SUPERCONDUCTING WIRE 
[75] Inventor: 
[73] Assignee: 
[21] Appl. No.: 
[22] Filed: 
James L. Smialek, Strongsville, Ohio 
United States of America, as 
represented by the Administrator, 
Nat’l. Aero & Space Admin., 
Washington, D.C. 
305,675 
Jan. 31,1989 
[51] Int. 0 . 5  ................................................ B32B 9/00 
[52] U.S. Cl. ........................................ S O W ;  505/701; 
505/702; 505/703; 505/704; 421/209; 421/457; 
421/688; 421/930 
[58] Field of Search ............................ 505/1, 701-704; 
29/599; 428/209, 457, 688, 930 
~561 References Cited 
U.S. PATENT DOCUMENTS 
3,243,871 4/1966 Saur .................................... 29/155.5 
4,171,464 10/1979 Steyert, Jr. ...................... 174/126 S 
4,339,508 7/1982 Tsuya et al. ........................ 428/606 
4,411,959 10/1983 Braginski et al. ..................... 48/558 
4,826,808 5/1989 Yurek et al. ............................ 505/1 
OTHER PUBLICATIONS 
Gruen et al., “Formation of Perovskite Surface Layers 
by Oxidation of Cu-La-Si Alloys”, J. Electrochemical 
Society Vol. 134 No. 6, Jun. 1987, pp. 1588-1589. 
Kumakura et a]., “Ba a Y-Cu-0 Superconducting Tape 
Prepared by Surface Diffusion Process” Jpn. J. Appl. 
Phys. 26(7) Jul. 1987, L1172 and 1173. 
Japanese Journal Applied Physics; vol. 27, No. 8, 8-88, 
Japanese Journal of Applied Physics: vol. 26 No. 4, 
Apr. 1987 pp. L31 I-L313-Yoshizaki et al., “Supercon- 
ducting Properties”. 
pp. L366-L367-Saito et al., “Properties in Various 
Sintering Atmosphere”. 
pp. L388-L390-Kawasaki et al., “Superconducting 
Films by Sputtering”. 
pp. L410-L412-Nagata et al., “Thin Films by Sputter- 
ing” -vol. 26 No. 5, May 1987. 
pp. L709-L710-Adachi et al., “Superconducting 
Y-Ba-Cu-0 Thin Films”. 
pp. L759-L760--Kohno et al., “La-Sr-Cu Oxide 
Wires”. 
pp. L336L336-Matsuzaki et al., “Preparation of a 
High Tc Superconductor by Oxidization”. 
Appl. Physics Lett. vol. 51, No. 3, Jul. 20, 1987, Jin et 
a1.-“High Tc Superconductors-Composite Wire 
Fabrication”. 
Primary Examiner-Patrick J. Ryan 
Attorney, Agent, or Firm-Gene E. Shook; John R. 
Manning; James A. Mackin 
ABSTRACT [571 
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 temperature, 
superconducting oxide phases are formed as a thin film 
14. 
L1492-1494. 
3 Claims, 1 Drawing Sheet 
, 
https://ntrs.nasa.gov/search.jsp?R=19910022215 2020-03-24T07:01:54+00:00Z
U.S. Patent ' Sep. 17, 1991 5,049,539 
5,049,539 
1 2 
then cold working the wire. The wires are then heated 
LOW COST, FORMABLE, HIGH TC to form Nb3Sn on the surface. 
SUPERCOSDUCTING WIRE U.S. Pat. No. 4,171,464 to Steyert is concerned with 
a high specific heat superconducting composite mate- 
ORIGIN O F  THE INVENTION 5 rial. This material includes a high specific heat ceramic 
The invention described herein was made by an em- in a metal conductor. 
ployee of the United States Government and may be U.S. Pat. No. 4,339,508 to Tsuya et a1 describes a 
manufactured and used by or for the Government for method for manufacturing a thin and flexible ribbon of 
governmental purposes without the payment of any superconducting material. The raw superconducting 
royalties thereon or therefor. lo material is heated to a temperature between its melting 
point and 300" C. above the melting point and then 
ejecting the melt through a nozzle against a cooling TECHNICAL FIELD 
This hvention is concerned with forming high Tc surface of a moving substrate such as a rotating drum. 
superconductive ceramic oxide films. The invention is U.S. Pat. NO. 4,411,959 to Braginski et a] is related to 
particularly directed to producing completely formable l 5  a submicron-particle ductile superconductor. The sub- 
superconducting articles. micron particles of superconductor are encapsulated in 
ductors involves sintering, hot pressing, or hot isostatic the absence of sintering or reacting annealing, thereby 
utilizing any of these methods is that the production of *O brittle 
complex articles, such as long, fine wire, is totally pre- 
cluded. DICLOSURE OF INVENTION 
To produce superconducting wire it has been sug- 
gested that plasma spraying, chemical vapor deposition, 
. 
In the prior art the production of ceramic supercon- 
pressing ceramic Oxide powders* The disadvantage Of 
a metal tube and then fabricated down to a fine wire in 
avoiding the problems associated with the formation of 
or filaments. 
The problems of the prior art may be solved and the 
or physical vapor deposition be utilized. It has also been 25 Object achieved by the present invention. Ceramic su- 
suggested that fibers be drawn from molten oxide or perconductivity parts are produced through the partial 
organic precursor liquids. In another process, supercon- oxidation of a specially copper alloy. The 
ducting oxide powders are encapsulated in ductile metal alloys contain low level quantities of rare earth and 
tubing which is extruded into wire. While superconduc- alkaline earth dopant elements. Therefore, upon oxida- 
ting wire is potentially produced, a considerable degree 30 tion at high temperatures, the superconducting oxide 
of extra cost and effort is involved in coating, fiber Phases may be formed as thin films. 
drawing, or encapsulating. Furthermore, the total de- Problems encountered in the prior art have been 
gree of fabricability in actual industrial applications, as addressed in that the Drocess of the Dresent invention 
opposed to laboratory demonstrations, still needs to be 
verified. 
It has been suggested that special copper alloys be 
fully oxidized resulting in special oxide phases exhibit- 
ing superconductivity. This approach is somewhat un- 
conventional in that relatively ductile copper alloy may 
indeed be fully formed. Then the alloy must be com- 
pletely 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 composi- 
tional limitations exist. Y, a commonly used supercon- 
ducting component element in Y 1Ba2C~307-~ super- 
conductors, is immiscible in Y-Cu melts. Therefore, a 
homogeneous Y-Ba-Cu alloy is precluded as would be 
any subsequent Y 1Ba2C~307-~ superconducting phase. 
A more serious 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 flexibility in 
the field normally associated with metal wire. Any 
processing following the oxidation step W O U ! ~  be scb- 
ject 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. 
. It is, therefore, an object of the invention to process 
superconducting articles, especially in wire form, with- 
. out encountering the prbblems of poor ductility or com- 
plicated processing normally observed for the super- 
conducting ceramic oxides. 
BACKGROUNDART 
U.S. Pat. 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 
has the ability to produce wire configurations rather 
35 than just bulk solids. Also the process exhibits 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 compos- 
ite wires into useful devices after partial conversion to 
the oxide phases. The invention gives more flexibility in 
alloy design because lower levels of rare earth and 
alkaline earth additions are needed. The invention 
avoids immisciblity problems at high Y-Cu concentra- 
45 tions, while avoiding mechanical forming problems 
.caused by high R-A contents. 
BRIEF DESCRIPTION OF THE DRAWING 
The advantages and novel features of the invention 
50 will be more fully apparent from the following detailed 
description when read in connection with the accompa- 
nying drawing which is an enlarged cross-section view 
of an oxidized Y-Ba-Cu wire produced in accordance 
BEST MODE FOR CARRYING OUT THE 
INVENTION 
55  with the present invention. 
Referring now to the drawing there is shown a super- 
60 conducting article, such as a coated wire 10, that is 
produced in accordance with the present invention by a 
partial oxidation of the specially formulated copper 
alloyed core 12. The alloy contains low level quantities 
of rare earth and alkaline earth elements. 
More particularly up to ten atom percent of rare 
earth and alkaline earth dopants can be used in alloying 
the copper core 12. By way of example, yttrium and 
barium may be alloyed with the copper core 12. 
65 
3 
5,049,5 39 
4 
ALTERNATE EMBODIMENT O F  THE A wire core 12 having a diameter of about 20 pm is 
I N X W T I O N  as believed to be satisfactory. Upon oxidation at high tem- peratures, Y 1 Baz. 
cu307-x, are formed as thin films 14. Yttrium and bar- It is further contemplated that alloying elements 
ium will be preferentially oxidized with respect to the 5 other than yttrium and barium may be utilized to form 
copper base element, even at low alloying levels, be- the superconducting phase. More particularly, lantha- 
cause Y and Ba are thermodynamically much more num, or rare earth elements, such as ytterbium, euro- 
oxygen-active than is copper. pium and gadolinium, may be used as aIloying elements 
An analogous situation exists for NiCrAlfZr alloys instead of yttrium. Also, strontium, bismuth, and thal- 
having about ten atom percent aluminium and about 10 lium may be substituted for barium. 
one atom percent zirconium. In this example, high tem- Other elements may be required to assist in the exclu- 
perature oxidation produces AI203 +ZrOz scales to the sive formation of R-A-Cu-0 during oxidation. Silicon, 
exclusion of NiO or Cr2O3. Thus films of any desired chromium, and aluminium may be used for this purpose. 
R-A-Cu-0 superconducting phase can be produced on It is further contemplated that oxidation exposures 
copper alloys by the proper selection of dopant levels 15 may require adjustment to precisely control and opti- 
and oxidation conditions. mize the superconducting films. For example, H2, H20, 
An important advantage of utilizing the thin film 14 or F gases may be utilized to produce beneficial atoms- 
structure of the superconductor material is that such a pheric modifications. 
form is extremely compliant in any type of post-process- While several embodiments of the invention have 
ing fabrications steps. By way of example, such steps 20 been described, it will be apparent that various modifi- 
may include coiling or bending, as might be required for cations may be made to the procedural steps of the 
winding motor coils or installing power transmission invention without departing from the spirit thereof or 
lines. Therefore, the limitation of post-processing brit- the scope of the subjoined claims. 
tleness associated with prior art materials are avoided. 
be used so that the thin superconducting oxide films 
constitute a considerable fractign of the wire cross-sec- 
tion. By way of example, an oxide film 14 having a 
thickness between 5 pm and 20 pm is easily formed in 
oxidation and its thicknesses sufficiently thin to be flexi- 30 
ble. 
A copper wire radius of 20 pm would amount to only 
44% of the total cross-section. This results in a substan- 
tial 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 conven- 
tional electrical transmission. It is apparent that should 
loss of cryogenic fluid occur some conductivity would 
I claim: 
1. A formable, high T, superconducting article com- 
a thin copper alloy wire substrate having up to about 
five atom percent of elements selected from the 
group consisting essentially of yttrium and barium 
alloyed therewith, and 
a highly compliant, thin, superconducting adherent 
Y1Ba~Cu307-.~ scale film thereon, said film form- 
ing a major fraction of the wire cross section. 
2. A superconducting article as claimed in claim 1 
35 wherein the thin copper alloy wires have radii of about 
20 pm. 
3. A superconducting article as claimed in claim 2 
wherein the thickness of the Y 1BarCu307- film is 
about 10 pm. 
However, it is apparent that thin copper wires should 25 
prising 
still be maintained through the copper wire substrate 12. 40 * * * * *  
45 
50 
55 
60 
65 


Low cost, formable, high T(sub c) superconducting wire

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