CA2090140A1 - Fabrication of superconducting metal-oxide textiles - Google Patents

Abstract

FABRICATION OF SUPERCONDUCTING
METAL-OXIDE TEXTILES
ABSTRACT OF THE DISCLOSURE
Process for producing superconducting metal-oxide textiles comprising impregnating a preformed, organic textile material with metal compounds in a desired atomic ratio, heating the material in a weakly oxidizing atmosphere to.
pyrolize and oxidize the organic material, maintaining the material at temperature in an oxidizing atmosphere, and cooling the material in an oxidizing atmosphere, so as to form a crystalline structure capable of superconducting.

Description

-. - 3 FA~RICATIO~ OF SUPERCONDUCTI~G f~
~ETAL-OXIDE TEXTILES '~
This is a continuation-in-part of 5 ~pplication Serial Number 07/573,855 filed ~ugus~ 28, lg90.

T~chnica~ Field This invention pertains to fibers, te~tiles 10 and shapes compos~d of superconductive metal o~ides and to a process for their ~abrication.

Backaround ~uperconductivity, the ~irtual 15 disappearance of electrical resisti~ity9 was initially discovered in mercury cooled to the boiling temperature of liquid helium. This discovery initiated the search for materials which would be superconductive at higher temperatures. In 20 1987 came a significant advance. Superconductivity was found at 95K in a material composed of several phases containing yttrium, barium, copper and o~ygen. ~he discovery was significant in that the temperature at which superconductivity ~pp~are~ was 25 above the boiling temperature of liquid nitrogen, which could then be used for the cooling ~edium.
The superconducting phase was found to correspond to the crystalline, orthorhombic oxide YBa2Cu3O7. The ~uperconductive property was lost, however, upon 30 heating the orthorhombic phase under conditions where o~ygen was depleted g;ving rise to a tetragonal phase, the composition of which was close to YBa~Cu3O6. The tr~nsition seemed to occur around ~ ~ .

~ the composition YBa2Cu3O6 5. Hence the superconductive property e~ists in compounds of the formula YBa2Cu3O7_~ where ~ may vary ~rom 0 to 0.4, the optimum being about ~.19.
Other high temperature ~uperconductors which now have been identified include YBa~CuO7_~, Ba~La5_~cu5Os(3-y)~ ~i2Sr~cu2O7~, Bi4~r3ca and T12Ca~Ba2Cu3O~.
Superconductive metal oxide material can be 10 produced by traditional ceramic techniques of grinding metal compounds in stoichiometric ratio to bring the metal compounds into pro~imity.
Subsequent calcination allows the metal ions in their respective crystalline compounds to diffuse 15 into the others. Repeated regrinding and calcination under controlled conditions produces the desired phase which has the superconductive property.
Most of the prospective appl~cations of superconductors are based on the capability of 20 transmitting electric power loss free, and on the production of powerful, compact magnets. Because motors and generators are based on magnetism, there is great potential for r~ducing their weights, sizes and inefficiencies. Powerful magnets are ~onceived 25 to allow the suspension of objects such as a shaft in a bearing and a train over a track.
The superconductive metal ozides, like ceramics, are intrinsically brittle and their fabrication into useful shapes, even basic wire, 30 presents many challenges. The most practiced method to date for the formation of ~uperconduetive wires has been the powder-in-tube technique. The D-163~0-1 superconductive material in powder form is packed 2~9 into a silver, ~opper or stainless steel tube. The tube is then swaged and drawn, or rolled, down to a ~mall diameter which can be further formed into a 5 useful configuration.
Lusk et al. in Supercon~. Sci. Technol. 1, 137 (1988) rep~rted ~n the fa~ricatlon of ~ cer~mic superconducting wire by an e~trusion method.
Superconductor precursor material in powder form was 10 mi~ed with a binder such as epo~y resin, and the mi~ture w~s e~truded into a wire form. The e~trusion was heated in a nonreactive atmosphe,re to remove the binder, and then sintered at high temperature in air or o~ygen to develop strength an~
lS the superconductive phase. ~ra~ile wire with a diameter of about 0.8 mm resulted from this method.
The preparation of superconductive fibers by e~truding or spinning a polymer-metal precursor was described by Chien et al. in Physical Review B, 20 3B, 1953 (1988). Metal ions in the desired atomic ratios were complesed to a polymer. The polymer solution was e~truded, dried and ~ound on a mandrel. Heating in nitrogen pyrolyzed the polymer, and subsequent heating in 02ygen converted the metal 25 intermediates to the superconductive o~ide. The process produced fibers having diameters of 1 to 100 micrGns and grain sizes from 1 to 50 microns.
Jin et al. in ~ppl. Phys. Lett. ~1, 943 (1987) described three different laboratory 30 fabrications of YBa~Cu307_~ wire by molten o~ide processing. In the melt drawing technique, the center of a bar of YBa2Cu30~_g material was fused `
:`` ~: :

with a laboratory blow torch flame, and the two 2~ ., O~.
unmelted ends pulled apart leaving a 1.2-mm diame~er filament between them. In the melt spinning technique, one end of a bar of YBa2Cu307_x material 5 was heated and a molten droplet allowed to ~all on the outside of a rotating mandrel producing a ribbon 1.5 mm wide and 0.3 mm thick. Still another e~periment employed a sil~er wire as 3 substrate onto which Y~a2Cu307_~ powder in a binder was 10 deposited. The composite was dried, producing a 0.75-mm diameter composite wire containing an 0.2~-mm diameter metal core. The wire was fur.ther processed by rapidly moving it through a torch flame and melting the outer portion. ~he wire formed in 15 each of these three methods required a homogenizing heat tr~atment followed by an o~ygen heat treatment to develop the superconductive phase. In production, any of these three techniques would require a high temperature melting furnace and 20 precise control of operating variables.
The processes described above were all directed to the fabrication of a sin~le filament. A
process for producing metal o~ide fibers, te~tiles and shapes was described by Hamling in U.S. Patent 25 3,3B5,915. By te~tiles is meant a variety of te~ile forms including single filament, s~aple fibers, continuous tow and yarns, woven fabrics, batting and f~lts composed of fibers.
The Hamling process comprises initially 30 impregnating a preform of organic polymeric te~tile material with one or more compo~nds of metals as desired in the final product. The impregna~ed ~-163~

-5- 2~301~O
material is heated under c~nSrolled conditions which prevent ignition o~ the organic material, but pyrolize the organic material to predominantly carbon and remove the ~arbon as a ~arbon-containing 5 gas. The heating continu~s to o~idi~e the metal compounds. ~t least part of the heating is - performed in the presence of an o~idizing ga~.
product results which has substantially the same shape as the preform, but only about 40 to 60% of 10 its original size. The metal oside in the product typically is substantially micro-crystalline, or amorphous, that is, its crystallites are so small that they are barely discernible by conventional 2-ray diffraction. This is indicative of a 15 crystallite size on the order of 0.1 microns or less, which Hamling preferred for masimum strength in his product. The process, however, is described as capable of preparing fibers with crystallite sizes up to approximately 1 micron. With larger 20 crystallite sizes, a significant 19ss in strength occurred. Mechanical properties of the product were impaired when the crystallite size e~ceeded appro~imately one-tenth the diameter of the fibers.
It is known that material capable of 25 superconductive behavior must be in a crystalline state. Hence the process as described by U.S.

3,385,915 would not produce superconductive metal oxide.
Fabrics composed of metal oxides are 30 described by Hamling in U.S. Patent 3,663,182. Such ~abrics are produced by the process described in U.S. Patent 3,385,915, which has been summarized .

'' ~' `~

- 6 - ~ 2~90~
above. Hence, the fabric has all the characteristics of a product of that process, and would not be e~pected to ha~e superconductiYe properties.
It is an object of the present invention to provide a process for producing superconducting metal oxide fibers, te~tiles and shapes. It i~ ~lso an object to produce these products with fle~ibility and strength so as to allow their further ~haping.
It is a feature of this invention that the starting material is organic polymeric material which can be preformed into the final product shape.
It is an advantage of this process that complicated and irregular product shapes can be 15 produced from ;ne~pensive oryanic material~ which are readily preformed into the desired final shape.
The preforming is ine~pensive in that costly machining is unnecessary. Another advantage is that a high temperature melting furnace is not required.
2~
SuMMARy ~F T~E INVENTI~N
The invention is a process for producing superconductive metal-o~ide textiles. It comprises initially impregnating a preformed, organic, 25 polymeri~ te~tile material with one or more compounds containing the desired metal elements in substantially the atomic ratios as o~cur in the superconductive material. The impregnated material is dried and heated in a controlled atmosphere to a 3D temperature suffi~iently high to pyrolize and o~idize the or~anic material and remove it as a carbon-containing gas. The heating is carried out __ , _ 7 - 2~
without igni~ion of the ~rganic and without melting the metal o~ide. The material is then cooled at least partly in an o~idizing atmosphere to further o~i~ize and develop a crystalline supercon~uctive 5 metal osideO

ERIEF DE~CRTPTION C~HE DR~I~
Fig. 1 is the X-ray diffraction pattern obtained on a specimen o~ YBa2Cu3O7_~ te~tile 1~ product by the process provided by this invention.
Fig. 2 is ~he ~-ray difEraction pattern obtained on a specimen produced by grinding m~tal powders providing metal elements in the atomic ratios indicated in YBa2Cu3O7_~ and sintering at 15 950C in o~yQen.

; D~AILED_DESC~IP~IQ~
The starting material in this invention can be any organic material capable of swelling and 20 ab~orbing a solvent and not melting on heating during the subsequent proc~ssing. Any cellulosic material can be employed including ray~n, saponified cellulose acetate, cotton, wool and ramie. Usable synthetics include acrylics, p~lyesters, vinyls ~nd 25 polyur~thanes. Rayon is a preferred material beca~se of its physical uniformity, high absorptivity and low impurity content.
The starting organic material is impregnated with ~ompounds of metal elements to 30 provide metal elements in ~he organic material in substantially the atomic ratios as are desired to appear in the product. When thesP compounds are . . ~

salts highly soluble in water, the impregnation c ~ 9 ~
be carried out by immersing the organic material in a concentrated aqueous solution of such ~alts in proper ratio. Alternatively, the organic makerial 5 may be immersed ~eguentially in ~everal solutions, each containing at least one of the desired compounds, thereby accumulating the ~esired metal content in the organic.
To obtain strength in the final product, it 10 is desirable to impregnate the starting materials with metal compounds to the e~tent of at least 0.25 moles and preferably 1 to Z moles of the metal-compounds per base mole of cellulose. Base mole as used herein refers to the molecular weight of 15 glycosidic unit of the cellulose chain, namely a molecular weight of 162. With non-cellulosic materials, the degree of impregnation should be at least 0.1 and preferably 0.5 to 1.0 gram-equivalent of metal per gram of organic material.
Water is the preferred solvent for metal compounds to impregnate cellulosic material. For impregnating vinyl and polyurethane materials, esters and ketones are suitable solvents. For impregnating acrylic and polyester materials, 25 ~uitable ~olvents for the metal compounds include aromatic alcohols and amines such as aniline, nitro-phenol, meta-cresol and paraphenylphenol.
To increase the rat~ and e~tent of salt impregnation in cellulosic starting material, it may 30 be preswelled by soaking in water prior to soaking in salt solution. For acrylic and polyester materials, aromatic alcohols are suitable swelling _ _ - agents. For vinyl and polyurethane materials, 2 0 9 ~ ~ ~ O
I ketones are useful.
¦ An alternate method of impregnating the organic material is to use metal compounds which 5 hydrolyze or react with water ~o form a metal oxide which is substantially insoluble in water. The selected compounds may be dissolved i~ ~n oryanic solvent immiscible with water, such as carbon tetrachloride, ether, or benzene, to the e~tent of 5 10 to 50 grams of metal compound per 100 ml of solvent. ~he starting organic material i~ prepared by e~posing it to air having a relative humidity of between 50 to 90 percent. It absorbs 5 to 30 percent by weight of water and swells. In this 15 swollen state, it is immersed in the prepared solution. As the metal compounds ;n the solution penetrate the swollen organic material, they react - with the water, and the resultant o~ide prec~pitates in the organic material structure. If the metal 20 compound is a gas or liquid, the swollen starting organic material may be e~posed directly to the gas or liquid to accomplish the precipitation of metal oxide.
Without being bound by the following theory 25 regardin~ impregnation, organic polymeric materials such as cellulose, ~hich are preferred starting materials for this process, are composed of small crystallites of polymer chains held together in a matri~ of amorphous polymer. Upon immersion of the 30 organic polymer in a prepared solution of metal salts, the amorphous regions absorb solution and enlarge or swell. The swollen amorphous regions ~-16390-1 -.
: : -. .
. .
.
: : " :

_ 10 --then comprise 50 to 90 percent of the volume of th~ 0 ~ 0 1 4 swollen organic. When the swollen organic i5 removed from the impregnating solution and dried, as by evaporation of the solvent, the metal compounds 5 remain in the amorphous regions. The amorphous regions are so small, about 50 angstroms in size in cellulosic material, that the metal compounds do not crystallize.
After withdrawing the Starting organic 10 material rom the impregnating solution, it is necessary to remove e~cess solution adhering to the surface of the starting material before this solution dries. Fibers bonded together by dried salt are likely to be similarly bonded in the final lS o~ide product and cause reduced strength and increa~ed brittleness. EYcess solution can be removed by ~lotting the impregnated material with adsorbent paper or cloth using moderate pressure to press out excess solution from the material.
20 Alternatively, washing, blowing with a gas stream, vacuum filtration or centrifugation may be employed.
Next, the impregnated material is dried by any convenient means such as a warm gas stream.
Rapid drying is desirable to avoid migration of salt 25 from the interior ts the surface of the impregnated material. A drying time of one hour or less is preferred. The drying ~an also be accomplished during the first por~ion of the heating step which is described following.
The ne~t principal step is to heat the impregnated organic material under controlled conditions to pyrolize the organic structure, ; ' :

~ eliminate the carbon and convert the metal compound~ O n ~ ~ A
to thQ desired metal o~ide. Pyrolysis is defined as ~hemical change brought about by the action of heat. Ignitisn and uncontrolled temperature ri~e of S the organic material during the heating iG ko be avoided. Otherwise the organic material may disintegrate ~efore the metal compounds h~ve intered together sufficiently to maintain the structural inteyrity of the working material. Also 10 e~cessive crystallization and grain growth may occur resulting in escessive loss of strength in the final product.
Ignition and uncontrolled temperature rise may be avoided ~y heating at a moderate, controlled 15 rate to a desired ma~imum temperature in an atmosphere of not more than weakly vxidizing capability. The ma~imum temperature will fall in the range from 500C to 1000C, and will depend on the particular superconducting material desired and 20 the treatment necessary to develop the appropriate o~idation state. The heating may be performed by suspending the impregnated material in a furnace having walls which are raised in temp~rature at a controlled rate. By radiation from the wall~ and 25 convection from the furnace atmosphere heat is transferred to the impregnated material so that its temperature approximates the furnac2 wall temperature. Ignition and uncontrolled temperature rise would be a temperature rise in the impregnated 30 material above the temperature of the furnace walls.
Heating rates of 60 C to 600 C per hour have been suitable~ Heating rates at the low end of .

this range are preferred in heating to about 400~C, 2 during which interval most of the pyrolysis of the organic will occur. 9y pyrolysi~ is meant chemical change brought about by the action of heat and with 5 little osidatio~. By oxidation is meant ch~mical change which involves combination with o~ygen. At temperatures higher than 400C, heating rates at the higher end of the range are preferred. A ~uitable atmosphere of weakly o~idizing capability was found 10 to be carbon dioxide. Operative are atmospheres containing nonreaetive gases with ~arbon dioxide, preferably in e~cess of 50% carbon dio~ide, e.g., from about 55% to about 100% carbon dio~ide; and preferably from about 70% to about 100% carbon 15 dio~ide.
Oth~r weakly ~idizing atmospheres may be employed such as nitrous o~ide, nitrogen dio~ide or sulfur trio~ide, mi~tures of two or more thereof and mi~tures of two or more thereof with nonreactive 20 gases. In an atmosphere containing nitrous o~ide, concentrations in e~cess of 10% nitrous o~ide are operative, e.g., from about 20~ to about 100%
nitrous o~ide.
Alternativel~ usable is a nonreactive gas 25 rontaining a ~mall percentage of o~ygen, e.g., nitrogen, argon, or helium containing several percent of ogygen. The oxygen content appropriate will depend somewhat on the heating rate employed, weaker o~idizing atmospheres in general allowing 30 somewhat faster heating rates. O~ygen contents up to 2% by ~olume are operative, from about 0.05 to about 1 % are preferred and from 0.05 to about 0.5 %

are most preferred. Above the critical content of 2 0 9 014 2% o~ygen, ignition and disintegration of the impregnated mat~rial was found to occur.
An atmosphere which is totally 5 non-o~idizing is not suitable during the heatin~
step because carbon is then ~pparently entrapped in the metal o~ide, is not sufficiently removed, Dnd is deleterious to the formation of the superconducting phase.
During the heating step, if ignition is avoided, consolidation of the metal compounds occurs which is evident as shrinkage of the starting preform material. Typically, the longest dimension of the startîng material shrinks 40 to ~0%. In 15 ~eneral, the shrinkage is inversely proportional to the degree of impregnation of metal compounds achieved in the starting material.
Particularly in the case of string or tape-like starting materials, it has been desirable 20 to apply a light tension to the starting material during the heating step. This tension ser~es to r~duce wrinkling or warpage of the material.
Upon reaching the selected ma~;mum temperature in the weakly o~idizing atmosphere, 25 these conditions are maintained until the reaction activity approaches completion as evident by the r~duction in evolution of gases from the starting organic. At this stage the pyrolysis o~ the starting material is substantially complete, and 30 oxidation of the carbon has at least begun.
The ne~t step is to convert to and maintain a mildly o~idizing atmosphere while appro~imately maintaining temperature~ until the o~idation and removal of the carbon as a gas has approached 2 0 n completion at these conditions A mildly o~idizing atmosphere can be conveniently pro~ided as a slowly 5 flowing nonreactive gas such as nitrogen, argon, or helium containing from 0.5 to 5~ of o~ygen by volume. The approach of reaction completion can be determined by observing the decrease end leveling off of the carbon dio~ide content in the effluent to 10 a small value, such as 0.5%, which has been observed to occur in from 0.5 to 2 hours.
At this poin~, the atmosphere is converted to at least a moderately o~idizing atmosphere, which will further gasify the remaining carbon and at 15 least partially form the desired o~idation state in the working material. Such atmospheres will contain at least 20% o~ygen and preferably ~ubstantially oxygen. In some instances, ozone with its greater ozidizing power may be advantageous. These 20 conditions are maintained at least for 0.5 hours and preferably for 5 hours.
Cooling may be performed in the latter atmosphere, and preferably in an atmosphere of substantially o~ygen. Cooling while the working 25 material is still at high temperature must be performed in an atmosphere which will add o~ygen to the working material, i.e., form or develop the ~uperconductive o~ide, and not remove o~ygen from the working material, i.e., maintain the oxygen 30 content. The cooling rate may be in the range of 60 C to 600 C per hour. During the cooling, the material is preferably in th~ established o~idizing __ .: : : ; ' :

atmosphere for a time of 0.5 to ~ hours while in the 2~90 temperature range of 700 to 400C. Such treatment ;s favorable for the development of the o~idation ~tate whi~h is superconducting.

Following i~ an example of the preparation of a superconducting tape of Y8a2Cu3O7_~ pursuant to the process of this invention. A solution was 10 prepared by dissolving 4 grams of Y(NO3)3O6H2O, 6 grams of ~a(NO3)~ and B.4 grams of Cu(NO3)3-3H2O
into 100 cc of distilled water at 60C. This con~entration was near the highest achievable, inasmuch as Ba(NO3)2, the least soluble of the three 15 salts, would precipitate at lower temperatures. A
rayon tape 1.25 inch wide, 0.018 inch thick, approximately 12 in~hes long, with individual fiber~
0.001 inch in diameter was soaked for 4 hours in this solution. E~cess solution was pressed out by 20 rolling the tape between sheets of absorbing paper.
About 10% by weight of salts in the tape was achieved on a dry basis.
The imbibed tape under slight tension of 50 grams was heated in a furnace at a rate between 25 60 C to 600 C~ per hour to 850C in a lowing atmosphere of carbo~ dio~ide ~as.
It was found that to form the desired YBa2Cu3O7_~ compound, the precursor tape had to be heated to at least 750C and pre~erably to 050C.
30 Above 950C, fracture of the precursor tape commonly occurred, apparently because of partial melting of the metal o~ides. At temperatures above 950~C, a , .
- . : . : .
.

molten peritectic region exists with ~ompositions ~ h that e~tend close to the desired YBa2Cu3O7_x compound.
~perimentation with nitrogen during the 5 heating step was also conducted, but did not produce the desired ~uperconducting product. Pyroly~ig of the starting organic material in a totally nono~idizing atmosphere apparently caused entrapment of carbon in the resulting metal o~ide which was 10 detrimentsl to the formation of the ~uperconducting oxide. Pyrolysis in air caused the impregnated tape ~o ignite and disintegrate apparently because the rayon fibers lost their structural integrity before the metal o~ides had sintered together 15 sufficiently. Carbon dioxide gas for the initial heating phase, where pyrolysis occurs, proved to be an acceptable atmosphere which avoided ignition yet allowed the o~idation and elimination of carbon.
Vpon reaching 850C in khe carbon dio~ide 20 atmosphere, these conditions were maintained for 1.5 hours. The atmosphere was then changed to nitrogen ~ontaining 1% o~ygen and maintained for 18 hours.
By this time, the carbon dio~ide content in the e~iting gas had decreased to less than 0.5~
25 indicati~g that the pyrolysis and carbon elimination reactions had approached completion. The atmosphere was then changed to 100% oxygen and maintained for 1 to 2 hours. Then tbe tape was slowly cooled to 450C at a rate of about 60 C per hour in oxygen.
0 Below 450C the tape was cooled rapidly to room temperature while the o~ygen flow was maintained.
The product tape typically was 0.4 inches wide and 4 inches long with individual fibers :

_ 17 - 2~
appro~imately 0.0004 inches in diameter. By chemical analysis, the tape composition was 16.67 atom % Y, 33.33 % Ba and 50.18% Cu which compared favorably with the ideal composition of 16.767 ~ Y, 5 33.67 ~a and ~0.00% Cu. Observed under a microscope, ~he tape had a morphology characteristic of the starting rayon tape.
~ -ray diffraction of the product tape displayed well-defined peaks characteristic of 10 superconducting orthorhombic YBa2Cu3O7~ as shown in Fig. 1. However, the relative magnitudes of the peaks differed from the relative magnitudes of orthorhombic YBa2Cu3O7_~ prepared by the traditional ceramic route of grinding and sinterin~ of solid 15 starting materials as shown in Fig. 2. This indicates that a degree of orientation of crystal axes had occurred in the crystallites comprising the product tape compared to the random orientation occurring in the ground and sintered material.
Although the invention has been described with a degr~e of particularity, the present disclosure has been made only by way of example, and numerous chanyes In the details and arrangement of various steps in the process may be resorted to 25 without departing from ths spirit and scope of the invention as hereinafter claimed.

Claims (8)

1. A process for producing crystalline fibers, textiles or shapes comprised of YBa2Cu3O7-x where x varies from about 0 to about 0.4, said process comprising:
(a) impregnating a preformed organic polymeric material with three metal compounds to provide metal elements in said material in substantially the atomic ratio occurring in said YBa2Cu3O7-x;
(b) heating said impregnated material in a weakly oxidizing atmosphere containing from about 0.05% to about 2% oxygen by volume to a temperature sufficiently high to at least partially pyrolize and oxidize said organic material and at least partially oxidize said metal compounds substantially without ignition of said organic material and without formation of a molten phase or reaching a decomposition temperature of said YBa2Cu3O7-x; and (c) cooling the resulting material in at least a moderately oxidizing atmosphere to room temperature so as to obtain said fibers, textiles or shapes.

2. A process for producing crystalline fibers, textiles or shapes comprised of YBa2Cu3O7-x where x varies from about 0 to about 0.4, said process comprising:
(a) impregnating a preformed organic polymeric material with three metal compounds to provide metal elements in said material in substantially the atomic ratio occurring in said YBa2Cu3O7-x;
(b) heating said impregnated material in a weakly oxidizing atmosphere containing nitrogen dioxide or sulfur trioxide or mixtures thereof to a temperature sufficiently high to at least partially pyrolize and oxidize said organic material and at least partially oxidize said metal compounds substantially without ignition of said organic material and without formation of a molten phase or reaching a decomposition temperature of said YBa2Cu3O7-x; and (c) cooling the resulting material in at least a moderately oxidizing atmosphere to room temperature so as to obtain said fibers, textiles or shapes.

3. A process for producing crystalline fibers, textiles or shapes comprised of YBa2Cu3O7-x where x varies from about 0 to about 0.4, said process comprising:
(a) impregnating a preformed organic polymeric material with three metal compounds to provide metal elements in said material in substantially the atomic ratio occurring in said YBa2Cu3O7-x;
(b) heating said impregnated material in a weakly oxidizing atmosphere containing carbon dioxide, nitrous oxide, nitrogen dioxide or sulfur trioxide or mixtures of two or more thereof to a temperature sufficiently high to at least partially pyrolize and oxidize said organic material and at least partially oxidize said metal compounds substantially without ignition of said organic material and without formation of a molten phase or reaching a decomposition temperature of said YBa2Cu3O7-x; and (c) cooling the resulting material in at least a moderately oxidizing atmosphere to room temperature so as to obtain said fibers, textiles or shapes.

4. The process as in claim 3 wherein said weakly oxidizing atmosphere contains nitrogen dioxide, sulfur trioxide, in excess of 50% by volume of carbon dioxide or in excess of 10% by volume of nitrous oxide or mixtures of two or more thereof.

5. The process as in claim 4 wherein said heating step comprises:
heating said material to a temperature between about 350°C and 1000°C in said weakly oxidizing atmosphere;
maintaining said material at said temperature condition and atmosphere condition until reaction activity approaches completion;
subsequently maintaining said material at said temperature condition in an atmosphere containing from about 0.5 to about 5% by volume oxygen until reaction activity approaches completion;
subsequently maintaining said material at said temperature condition in an atmosphere containing at least 20% by volume oxygen until reaction activity approaches completion; and said cooling step comprises maintaining said material in the temperature range of 700°C to 400°C in an atmosphere of at least 20% by volume oxygen for at least one-half hour.

6. A textile produced in accordance with the process of claim 4.

7. The textile as in claim 6 wherein said fibers have a textile morphology and a diameter in the range of from about one to about twenty-five micrometers.

8. The textile as in claim 6 further comprising material having an X-ray diffraction pattern with peaks substantially at angles and substantially with relative magnitudes as in Fig. 1.