CA1338396C

CA1338396C - Process for manufacturing a superconducting wire of compound oxide-type ceramics

Info

Publication number: CA1338396C
Application number: CA000558142A
Authority: CA
Inventors: Kazuo Sawada; Sigeki Isojima; Susumu Yamamoto; Teruyuki Murai; Nozomu Kawabe; Hideo Itozaki; Kenichiro Sibata; Kazuhiko Hayasi; Tetsuji Jodai; Nobuhiko Fujita; Shuji Yazu; Nobuyuki Sasaki
Original assignee: Sumitomo Electric Industries Ltd
Current assignee: Sumitomo Electric Industries Ltd
Priority date: 1987-02-05
Filing date: 1988-02-04
Publication date: 1996-06-18
Anticipated expiration: 2013-06-18
Also published as: EP0475466B1; DE3877018T2; EP0281444B1; JPH09185914A; JP2877149B2; AU1142288A; JPH01140520A; CN1033991C; EP0475466A2; JP2996340B2; JP2914331B2; EP0281444A1; JPH09185915A; JPH09185916A; CN1031442A; DE3877018D1; EP0475466A3; US5981444A; AU597148B2

Abstract

A process for manufacturing a superconducting elongated article such as a superconducting wire which is applicable for manufacturing a superconducting coil or the like. The process includes steps comprising filling a metal pipe with material powder of ceramic consisting of compound oxide having superconductivity, performing plastic deformation of the metal pipe filled with the ceramic metal powder to reduce the cross section of the metal pipe, and then subjecting the deformed metal pipe to heat-treatment to sinter the ceramic material powder filled in the metal pipe. The ceramic material powder may contain compound oxide having Perovskite-type crystal structure exhibiting superconductivity.
The metal pipe may selected from a group comprising metals of Ag, Au, Pt, Pd, Rh, Ir, Ru, Os, Cu, Al, Fe, Ni, Cr, Ti, Mo, W and Ta and alloys including these metals as the base. The heat-treatment may be carried out at a temperature ranging from 700 to 1,000 °C, The plastic deformation of the metal pipe filled with the ceramic metal powder may be performed in such manner that the cross section of the metal pipe is reduced at a dimensional reduction ratio ranging from 16 % to 92 % by wire-drawing or forging by means of dies, roller dies, or extruder.

Description

S P E C I F I C A T I O N

~itle of the Inventlon Proces~ for manufacturlng a ~uperconducting wire of compound oxide-type ceramic Backgro~nd of the Inventlon ~ield of the invention The present invention relates to a process for manufa~turlng ~n elongated article made of sintered ceramic having superconductivity.
Particularly, ~t relates to a process for manufacturin~ a ~uperconducti~g wire made o~ slntered cer~mic of co~pound oxide which is appllcable for producing a superconducting colls or the like.
More particularly, the pre~ent invention relate~ to a proce~s for manufacturing a ~uperconductlng wire made of slntered ¢er~ic of compound oxlde havlng hlgher ~ritical current density and hlgher critical tra~sltion te~pe~ature of superconductlvity.

Description of the related ar~
The ~per~onductivity is a phenomenon in which~ the electrical resi~tance ~ecome zero and henee can be utilized to reall7e pow~r cables and a variety of ~evices and apparatuG whlch ~re ~eque~ted to redu~e con~umptlo~ of electrical energy and se~eral idea~ of its applicatlon~

which utilize the phenomenon of superconductlvity have been proposed.
In fact, the super¢ondu~tivity are applicable in a variety of indu~tr1 al fields, ~cr exa~ple in the fleld of electrical power supply such as fuslon power, MHD power generatlon, power trans~ission, or electric power reserva~ion; in the field of ~ransportation such as magnetic levit~tion trains, magnetioally propelling ships;
in the medical field su~h as high-enargy beam rad~ation unit; in the fi~ld of science su~h as NMR or high-energy physlc~; or in the field of se~sor~ or de~ectors fo~
~ensing very weak magnetic field, microwave, radia~t ray or the llke as well as in the field of electron~c~ 5uch as Jo~ephson Junctlon devices and hlgh-speed ~omputers with reduced en~rgy con~umption.
Howev~r, thelr actu~l usag~ have bee~ re~trlcted because ~he phenomenon of super~onductivity can be observed only at very low ~ryogenic temperatures. Among known superconduc~ing material~, a group of materials having so-called A-15 ~tructure show ra~h~r higher Tc ~crltical temperature of superconductl~ity) ~han other~, but even the top re~ord of Tc in the ~ase of N~3Ge which showed the hlghe~t Tc could not exceed 23.2 K at most.
Thi~ means that liquidized helium (bolllng po~ nt of 4.2 K) læ only one cryogen that ~an realize su~h very ~ow temperature of Tc. However, heliu~ i9 not only a limited costly resource but also requlre a large--sc~l~d 9y8t~ for li~uefaction, The~efore, it had been de~ired to find ano~her ~upercondu~ting material~ havlng mu~h hlgher Tc, But no material which exceeded the abovementioned Tc had been found for all studies fo~ the p2st ten year~.
I~ is known that certaln ceramlc~ material of compound oxides exhibit the property of ~uperconductivity. For example, U. S. patent No, 3,~32,315 discloses 3a-Pb-Bi-type compound oxid~ which shows ~uperconductivity. Thl~ type superconductor, however, posses~ a rather low transition tempera~ure of low~r than 13 K and hence u~age of liquldized heliu~ (boiling point of 4.2 K~ 2g cryogen ls indi3p~nsable to realize superconductivity.
Po~sibiii~y of exi3tence of a new type of superconductlng materials having much higher Tc was revealed ~y sednorz and Muller who dl~covere~ a new oxide type superconductor in 1~86 (2. Phys. ~64 (1 ga6 ~ pl 8~) Thls new oxide type superconductin~ material i~
~a, 3a~2Cu04 or tLa, Sr]2Cu04 which are so-call6d the ~NiF~-type oxide havlng such d ~yst~l ~truc~ure th~t i~
Qlmllar to Perov~kite-type superconducting oxides whi¢~
were known in the pa~ ~for example, ~apb1-x~ixo3 dtsclo ed in U,S,Patent No. 3,932,315). The K2Ni~4-t~p~
oxides 6how ~uch hlgher Tc as about 30 K w~ich i8 ex~remely higher than that of known superconducting ma~erials.
As the compound oxide type ~uper¢onductor~ consisting of oxides of eleme~ts of IIa and ~Ia group~ in the Perlodtc Table, it can be mentioned tho~e of, 90 to ~ay, qu~si-Perovskite structure which can be con~idered to have ~uch a cry~t~l 5tructure ~hat is simil~r to Perovskite-type oxides and lncludes an or~horhombically disto~ed perovsklte or a dlstorted oxygen-defi¢ient perovskite such a~ 3a2YCu307-~ in addition to the abovementioned ~2Ni~4-type oxide su~h as ~La, Baj~Cu04 or ~a, Srt2Cu04~ Since these superconductlng materlals show very high Tc of 30 to go ~, it ~ecomes po~sible to u~e liquidi~ed hydrogen (b.p~ Y 2~.4 K) or liquidized neon ~b.p. = 27.3 K) as a cryog0n for reallzlng ~he superconductivi~y in practi~e.
Particularly, hydrogen i8 an inexhaustable re~ource except for danger o~ explosion.
Howeve~, the above mentioned new type superconducting materials whlch W~8 ~ U3~ born have ~een studied And developed only ln a form of ~int~red ~odies as a bulk produced from powders but have no~ been tried to be shaped into a wire form. The xeason is th~t the new type superconductors are cerami~ materials of compound oxide wh~ch pos~ess no superior plasticity or processabllllty in comparlson with ~ell~known metal type cuperconducting materlals such as Nl-Ti alloy, and th~refore they can not or are difficult to be shaped or de~or~ed in~o an elongated ar~icle such a~ a wire by conventional te~hnique 3uch as wire-dr~wln~ technigue in which ~uperconducting metal is drawn dir~ctly or ln embedded cond~tion in copper to a wire foxm.

It is propo$ed in Japane~e patent lald-open No. 6~-131,307 a method for manufacturinq a ~upercondu~ting wire from a ~etal type 6uper~0ndu~ting materlal which is apt ~o be oxidized and very fragile such a~ PbMoo,35Sg, comprising charglng the material powder in a metal shell, extruding the metal shell fllled wlth the material powder at hlgher than 1,000C, and then drawlng the extruded composlte.
This metal working technique, however~ can not app;~
dire~tly ~o ceramic materlal consistlng of compound oxide, be~a~se the ~ompound oxide type superconducting materials can not exhibi~ the superconductivity if no~ the ~pecifled or predetermined eryst~l structure i9 realized. In other word, a supercondu~ting wire havin~ higher critical temp~rature and higher crltlcal ¢urrent den~ity and which l~ useable ln ac~ual applications can not be obtalned outs~de p~edetermined optimum condition~ In p~rtlcular, if not the shell i~ selected f~om proper materials, the re~ulting compound oxlde will be reduced due to chemical rea~tion with the metal o~ the 5hell, re8ulting in poor or inferior properties of superconductivl~y, In the field of ceramic molding, it has bee~ the g~ner~l practlce for manufa~tu~ing an elongated artlcle su~h as wires or rods to add an organi~ binder to the material powder of ceraml~ in order to facilit~e shaping or molding of the powder materlal. Thus, ~ mixture of the powder materlal and the organi~ binder i~ shaped into a ro~
by m~an~ of an extruder or a pre~s maGhine and then th~

shaped rod i6 pa~sed directly or through a trimming or cutting stage to 2n intermediate sintering ~tage to remove the o~ganic binder before it is fed to the flnal sintering ~tage.
The c~bination of the above~entioned press-moldln~
and trimming or cuttlng operations loose much material of expensive ceramlcs, 50 ~hat not only econo~y of materlal ls low but also a dlmen~io~al r~tl~ of longltudinal dlrection to cross se¢tional dir~ction of the rod can not be increased. Therefore, this proce8s can not be u~ed ln prac~ice.
The extrusion technlque i6 much ~etter than the pre3s-moldlng technique in the economy of .~aterial and producti~ity, but re~uires great qu~ntltles of o~ganlc binder added to the powder material. Thls o~ganlc binder is difficult to be re~oved co~pletely durlng the lntermedla~-e sinterlng stage and hence remain in the flnally sintered artlcle, re~ul~ing tn a cau~e o~ defects of the product which will lower the 8trength and the resl~tance- to fle~ion. Therefore, it is dif~lcult to manufacture a fine rod of ceramlcs having higher dlme~ional ratlos o longitudinal directlon ~o cross sectional direction according ~o the extrusion technique.
In order to realize a rellable and practical su~erco~ducting 3tr~cture, it is lndl~pensabl~ tha~ the structure possssses enough strength and ten~clty which ls sufflcieQt to endure bending force ~uring usage and also has a finer cro~s sectlonal di~enslon ~s possible in such ma~ner that lt can transmi~ curre~cy at higher criti~
current density and ~t higher crltical temperature.
Therefore, an o~ect of the pre3ent invention is to provide a process for manufa~turing a superconductin~ wire o~ sintered oeramie havlng an eno~gh length to be used in practical ~pplic~tion~ mely havlng a higher dimensional ratio o~ lo~g~tudinal direction to cros~ ~e~lonal direction, without ~slng orga~lc binder which is caus~tive of lowering the strength ~nd tenacity of the product.
Another ob~ect of the present invention i~ t~ provide a process or manufa~turing a fine ~upercondu~ting wire o~
compound oxide type ~intered oeramic ha~i~g higher resistance to breakage, even if the the diame~e~ of the wire is reduced greatly, in other words, under higher dimen~ional reduction ratio in cross sectlon.
Still another object of the pre~ent i~ventlon ~ to provide a pro~es~ for ~anufacturing a fine ~upercond~cting wlre of compound oxide type ~intered ceramlc having higher critlcal ~urrent density and higher crlt~cal temperature.

Summary of the_Invention A subjeot of the pre5ent invention re~ides in a process for manufa~turing a ~upe~conducting elonga~ed article lncluding ~teps ~omprlslng ~illing a metal plpe wlth materlal powder of ~eramlc consiatin~ o~ compound oxide having superconductivity, performlng plastlc t 338396 deformatlon of the metal pipe fllled wlth the ceramic metal powder to red-lce the cross section of the metal pipe t and then subje~ting the deforme~ metal pipe to heat treatmen.
to sinter the ceramic materlal powder filled in the metal pipe.
The elongated articles which can be manufa~tured by the proce s according to the present invention include rod, wire, strand, tape, band, or any other articles whose di~ensional ra~io of the elon~ated direction to the cross se~ticnal dlrection i~ more t~an 30, the cross section of ~he article being not limited to a cirele but may any conf ig~ration such as a rec~angula~.
The materlal powder of ~eram~ consisting of compound oxide h~ving superconductivlty lnclude ~ny compound oxide which exhibit superconductivity after the ~eat-treatmen~ of the pre~en~ lnvention.
Generally speaklng, the ~aterial ceramic powder which can be used in the proce8s of the present invention may have the gen~r~l formula: AaBbCc, i~ wh~ch "A" s~and~ for at l~a~t on~ ele~ent ~elected f~om ~ group comprising IIa and IIIa of the Periodlc Table, "~" stands for at lea~t one e~-emen~ s~lected from a group co~pri~ing Ia, IIa and tIIa of ~he Periodic ~able, "C" stand~ for at least o~e element selec~ed fro~ a group comprlsing oxygen, ~a~bon, nitrogen, fluorine and sulfur, and sm211 l~tter~ "a" "b" and "c"
stand for stom ratios of the elements "A", "B" and "C" and they preferably satisfy following equat$on:

"a"x(an ~verage valen~e o~ "A")+"b"x(an average valence of "B") = "c"x(an avera~e vale~ce of "C"), A~ the element of Ia ~roup in the Perlodic ~ble, it can be mentioned H, ~i, Na, K, Rb, Cs and Fr. The elements of IIa in the Periodic Table may be Be, Mg, Ca, Sr, ~a and Ra. The elements of IIIa ln ~he Perlodic Table may be Sc, Y, La, Ce, Pr, Nd, Pm~ Sm, Eu, Gd, Tbr Dy, Ho, 2r, Tm, Yb, Lu~ Ac, Th, Pa, Pa, U~ Np, Pu, Am, Cm, Bk, Cf, Es, Fm, Md, ~o and Lr. The elements of Ia in the Periodlc ~able may ~e Cu, Ag and Au. The elements of IIb in the Periodic Table may be Zn, Cd and H~. The elements of IIIb in the Periodic Table may be ~, Al, Ga, In and Tl.
The material ~erami¢ powde~ is prefe~ably a powde~
mlxture cont~ining oxides of such metal~ that pos#ess hlgher oxygen po~e~tl~l for producing the oxide than that of copper.
Among superconducting ceramics, it ca~ be men~ioned those that contaln at least tw~ elemen~s ~ele~ed ~rom Ia, IIa and IIIa group~ of ~he Periodic Table a~ "A'l, at least copper as "B", and oxyge~ as "C", for example, Y-Ba-~u-O
type cera~ics, Y-Sr-Cu-O ~ype ceramic~, La-Sr-Cu-C type c~ramic3 and La-Ba-Cu-O ~ype ceramic~.
~ he ceramlc material powder ~ay be compound oxl~es having the crystal ~tructure of K2NiF4-typ6 oxides, such as ~La, 3a~2CuO4 or ~a~ Sr~2cuo4 , And also, the material ceramic powder may be compound oxides having Perovskite-type crystal ~tructure exhiblting super~ondu~tiv~ty havi~g the general fo~mula:
x, ~0x ) ~y Oz ~herein d ~tands for an ele~ent selected from IIa group element3 of the Periodic Table, ~ 8tand~ for an eleme~t selected fro~ IIIa eleme~t~ of the Periodic T~ble, ~ ~tands for an element 6ele~ted ~om a group coMprisi~g Ib, II~, IIIb, IVa and VIIIa elements of the Periodic Table, x, y and z are number3 which ~tisfy follow~ng respective ~ange~:
0,1 ~ x ~ 0.9, 0.4 ~ y ~ 4.0, and 1 ' z 5 5.
In par~icular, a ~ompound oxide in which ~ i3 Ba, ~ is Y
and ~ is Cu.
It is also pre$erable to use a ~eraml¢ .~atexial powder ~hi~h is prepared by ~tep~ ~omprislng mixing powders of Bi203, SrC03, cac03 and cuo, drying and then compaeting the powd~r ~ixtur6, ~intering ~he ~ompa~ed mas~, and then pulverlzlng the sinte~ed mass.
The materlal powder~ of ceramics are preferably granulated prevlously before they ar~ filled lnto the metal pipe.
The metal plpe may be selected from a group comprising metal~ o~ ~g, Au, Pt, Pd, Rh, Ir, Ru, 08, CU, Al, Fe, Ni, t 338396 Cr, Ti, Mo, W and Ta and alloys lncluding these m~t~1s the base.
The heat-treatment may be carried out at a temperature range of from 700 to 1,000 C, The plastic defor~ation of the ~etal pipe filled with the cer~mic metal powder may be perfor~ed ln ~uch manner that the cross section of the metal plpe l~ reduced at a dimen~ional reduction ratio rangi~g from 16 ~ to 92 %. Th~
operation of the pla~t~ c deformatlon ~ay be carried out ~y wire-drawlng which is perfoxe~ed b~ means of dl~, rolle~
dies, or ~xtruder.
The plastic defor~a~ion may be performed by forging, for example by meang of swaging unit or roll .
It is also prefe~a~le to cool the metal pip~
containing th~ sintered ce~amio ~terial powder therein ciowly at a rate of less than 50 C/mln, after the heat-~reatment complete.
Now, an apparatu~ which can be used to realize th~
abovementioned p~oce~ ~ccordlng to the pres~nt lnv~ntion wlll ~e de~ribed with re$erence to attached drawlng3 which are not limitative of the present inventlon.

Brief d~scription of th~ drawin~s Fig. 1A to 1J illustrate a ~eries of steps or manufacturin~ a 3upexconducting elongated ~rticle according to the pre5ent inventlon.

Fig. 2A to 2C ~hows variation~ of ~he ~uperconducting elongated articles accor~ing to the present invention, wherein Fig~ 2A ls ~n illustrative per~pectlve view of the article, ~ig. 2B is a cros3 section thereof, and Fig. 2C
shows an illustratlve view of another embodiment of the article.
F~g. 3A and 3B ~how ~ross sectlons of variations of ~ig. 2.
Fig. 4 shows anther e~bodiment of the p~esent lnvention, wherein, Fig. 4A is a cross section and Flg. 4s is a plane view of the elo~gated article according to th~
present invention.
Fig. 5 shows still another em~odiment of the present lnvention, wherein, Fig. 5A is a cross section and Flg. 5B
i~ a perspective view of the elcng~ted article accordlng to the p~esent i~ven~ion.
~ ig. 6 i~ an illustrative view of an apparatus for manufacturing continuously a compo~ite having ~ ~ape-like oonfiguratlon according to the present in~ention.
Referr~ng to Flg, 1, the Flg. 1A to Flg, 1J lllustrate manufacturing ~teps for an elongated ~rtlcle ~ccording ~o th~ present invention.
At fir~t, a metal pip~ 1 having a prede~er~ined cros~
sectional configuration ~outer diameter of "L", and in~er diamete o~ "l") is fiiled with a materl~l ceramic powder

2, as is ~hown in ~ig. 1~

1 3383~6 Then, the re~lting metal pipe filled wlth the material ceraml¢ powder ls pa~ed to an operation of wire-drawing which can be performed by means of roller die~ 3 ~s is shown in Fig. 1C, or a dle or a series of dies 4 shown in Fig. 1 D ln a cross section, The wire-drawing ~ay be performed by me~n~ of ~ swaglng unlt 5 as is shown in ~ig.
E or an ex~ruder-type wire drawlng machine (Fig. 1 F Qhow~ a cro&~ sectlon of an extruder head~. In case of an elongated article having a re¢tangula~ ~ross sectlon, the metal pipe may be rolled by means o~ rolls 7 as is 8hown in F ig . 1 H .
An annealing step can be lncorporated in the wi~e-drawing ~tage in order to fa~flitate ope~at~ of the wlre-drawing. It is also prefer~ble to seal o~e end or oppo~ite end~ of the met~l pipe before en~erlng i~to the wire-drawing operation as ls shown in ~ig. lH to pre~ent the powder m~terial from e~aping out of the me~al pipe.
Fig. lI illustrates a perspectiv~ view of ~he resulting wire-drawn product comprising an inner core obtained from the material powder ~ havlng a reduced diameter "1"', so that the flnal product which will ~e obtained a~ter following ~intering step hereinaftex de~ibed ha~ ~he ~ame conflgura~ion as Fig. lI.
Fig. 1J illustrates a case in which the outer pipe i~
removed.
F~g. 2 shows a variation of the elongated article obt~ined according to the pre~ent lnvention, ln which perforations or throuqh holes are made in the metal plpe 11, In an em~odlment ~hown i~ the perspective view of Fig~
2A, fine hole~ 13 are cut through the ~etal pipe over the who1e surface thereof by means of CO2 la~er or the llke.
Fig, 2B is a ~ross ~ectional ~iew of the pipe show~ in Fig.
2A. The holes 13 may be replaced by a slit 13~ shown in Fi~. 2C. The slit 13~ may have a dimension of a~out 20~ ~m in width.
It ls known that the re~ulting ~upe~conducting wire de~eriorates under an oxy~e~ ¢ontainlng atmosphere such as air, ~o that it i~ preferable to close up the holes 13 cut in the metal pipe 11. For this purpose, the holes 13 can be fil'ed up with sealant 14 to isolate ~he slntered wire o~ superconductor 1~ from ambient at~o~phere ~g i3 shown in Fig. 3A. Th~s method, however, i~ difficult to practice o~
has ~ot hlgher productivity, ~o that, ln practice, it is preferable to cover whole of ~he outer sur~ace of tha per~o~ated metal plpe wlth a suitabl~ air-tight cylindrical liner, for example a heat shr1nkable plastic tub& which 18 chemi~ally 3table as is shown in Fig. 3B. The liner may be compo3ed of a metal layer vacuum-deposited on the whole su~face o~ the metal pipe and more preferably may be made of low-meltlng polnt glass coated on the met~l pipe to produce a complete s6alin~.
Fig. 4A illustra~s an el~ngated ~lntered superc~nductor having a rectangular ~oss 8ectlon accordlng to ~n embodiment of the present lnvention and Fi~. 4~ ~hows a piane view thereof. Thls superconductor can ~e ~anufactured ~y a proce ~ including ~teps o~ molding of the supe~condu¢tlng m~terial lnto a shape of rectangular body 21 a~d then covering the molded article 21 with a me~al sheath ~2.
Fig. 5 illu~trates another ~mbodiment o~ the elong~ted artlcle having a same circular cro-cs se~tion ~s ~h~ o Fig. 1I according to the present invention, ~ut, in ~hls ca~e, a supercondu~to~ 21 ig covered with a sheath 24 made of a net. Fig. 5A is a ~ross sectional vlew and Flg. SB ls a per~pec~ive ~lew of ~he ~he resulting superconductor.
The abovementioned variation can ~e ~dopted ~o a variety of applieat~o~s. The presence of the abovementloned porou~ outer 3~eath or ~hell have followlng advantages:
At ~irct, the surface of the sheath 22 and 24 is ox~dized by the oxidative treatment to produce copper oxide, ~o that th~ contents of oxygen in the sintered ~uperconductor is not influenced or fluctuat~d by the oxidation of the sheath 22 or ~4, In particular, in cas~
of Fig. 2~ and Fig. 4, through holes 13 are dlsper~ed on the whole surface of the metal pipe 11 and 2~ and, 30 that the sintered superconductor can co~municate with an outer atmo~phere. Higher contact surface between the superconductor and the surrounding atmosphere ean be as~ured by the net-lik~ 8heath 24.

Fig. 6 lllu~trate~ an appaxatus for produclng an elongated artlcle contlnuously according to the pre~ent invention. In this case, the materlal ceramic powder i~
prefPra~ly blended wlth organic binder.
The ~pparatus ln~ludes a contlnuous furnace being provided with two heating mean~ of a binder-removlng zor.e 112 and a ~intering zo~e 113. An elong~ted shaped tape or wire 1~4 is supplled to an inlet of the binder-removi~g zone 112 from a col~er 11~, The elongated arti~le 114 unwound fro~ ~he coiler 115 is fed continuously to the to the blnder-removing zone 112 in which the elongated art~ole 114 is heated at a temperature of 4~0 to 700 C to remove th~ blnder ou~ o~ the elonga~ed article 114, A~tor the binder-removing zone 112, the elongated arti~le 114 is pa~ed to a continuou~ lining ~tation 11~
which is positioned at the downs~ream of the binder-removin~ zone 112. The con~inuous lini~g s~a~ion 11~ i8 p~ovided with a drum 118 for feeding a sheet 117 of metal or ~lloy to ~ guide 119 whe~e th~ sh~e~ 117 1s wound a~ound the elonqated arti~le 117. A sea~ of the wound sh~et 117 i3 welded by me?n6 of ~ laser welder 120 80 that the elongated artlcle 114 ~ s wrapped ~y the metal ~heet 117.
The resulting composite ~o~prising the elongated article ~14 ~nd the coverin~ sheet or outer ~heath 117 is then passed to the sinterlng zone 113 ~he~e th~ ~ompo8ite i~ heated at a temperature of ~50 to 950 C to ~inter the elongated art~cle. The longltudlnal ~imen~ion or length o~

the ~interlng ~one 113 and the advancing veloclty of the composite can ~e ad~usted in 3uch manner that the slntering is performed completely.
The product 121 thu3 obtained may be wou~ about a drum 122 for sto~k, In thi3 embodlment, the product po~sesse~ enough flexibility and sel~-6upportlng propertles, since the elongated article 114 eor.~ain~ the binder~ The apparatu~ shown ln Fig, 6 pe~mit to carry out the clnterlng operation contlnuously at a higher productivity.
According to a vari~tion o~ the pre~ent inventlon, the composite comprising ~he elongated article and the outer sheet ca~ be shaped or deformed into a de~lred configuratlon su~h as a ~oil or the like due to the higher flexibility a~d 8elf-supportlng proper~y, ~o that the ~intering can be performed ln th~ condition of the coiled conflguration or in a condition that the colled is supported on any other conductive body. The exl3tence of the sheath of me~al or alloy al80 increase th~ deflectlve strength.

De~cription of the Preferred Embodlment8 In a preferable embodlment according to the present inventlon, as the materlal ~eramic powder, following powders may be mentioned:

(~ ) Ceramic po~der containing compound oxides having the crystal ~tructure of K2NiF4-type oxides having superconductlng property, particularly powder of [ La, Ba ~ 2cuo4 or [ La, Sr 1 2cuo4 .
I 2 ) ~ompound oxlde3 having Perovskite-type crystal structure exhiblting supercondu~tivity having the general formula:

~ d l -x, ~ x ) ~y oz whersin ~ ~tands for an element seiected from IIa group element~ of the Periodic Table, ~ stand~ for an element 3electe~ f~om IIIa elements of the Periodi~ Table, J stands for an element sele~ted from a group comprising Ib, I~b, IIIb, IVa and VIIIa element3 of the Perlodic Table, x, y and z are number~ whi~h satisfy followi~g respe~tive range~:
o.1 ~ x ~ o.s, 0~4 ~ y ~ 4.0, and 1 ~ z ~ 5, In particular, a Ba-Y-Cu-O-type compound oxide in whlch d i~ Ba, ~ l~ Y and ~is Cu.
It is posslble to use another type ceramic material powders for example a ~ompound oxlde compo~ed of at least two ~lements selected from a group ~omprising IIa and III~
gxoups in the Periodic Table, one element selected from a group compri~lng Va group ln the Periodlc ~able, Cu and oxyge~, such as Sr-Ca-Bi-Cu-O type ~ompound oxide which i~
prepared for example by the steps ~ompri~ing mixing powders of ~$~03, SrC03, CaC03 and CuO, drylng and then ~onnpactirlg the powder mixture, sintering the compacted mass, and then pulverlzing the si~tered ma~s, The material powderc used ~n ~he preæent invention are not llmited to those abovementloned.
The material powder~ of ceramlc~ are p~e~erably granulated prevlously before they are fllled into the metal pipe. When the material powder can not compacted into the metal pipe at a hlgher packaging denslty, lt is desixable to granulate the material powder prevlously to facili~ate charging operatlon lnto ~e metal pipe and to obtaln a higher packaglng den~ity.
Accordlng to a preferred embodiment, the ~aterial powder i~ granulated lnto particles having an a~er~ge partlcle ~ze of le~s than 0,1 mm and then is heat-treated before they are charged lnto the metal pipe. Thl~ hea~
treatment correspond to the final sintering u8ed in the conventional procedure. In this case, lf necessary, the material powde~ may be further heat-treated agaln after the powder i9 compact~d in the metal pipe. If the heat-treatment of the powder ma~e~ial result in coagula~ion of powders to produce large particles havlng an ~ver~ge particle size of more than O,t mm, the heat-treated powder may be pulverlzed befo~e it i5 compacted in the ~etal plpe.
I~ thie ca~e, conventional flnal heat-treatment i9 earrle~
out in the ~ondition of po~der havin~ an average particle size of le83 than 0~1 mm. Therefore, the re~ulting heat-lg treated powder a~ a w~ole po~ses3 the crystal structurewhich exhiblt3 ~uperconductivity and hence there remain no portion whore cuperconductivity i~ not exhlbited. Still more, higher packing factor or density i~ obtained in the met~l pipe and also higher ~atio of elongation of the wire is assured. In con~lusion, the re~ulting wire obtained ~ccording to thls emb~dime~t is changed to a~ elongated supercondu~ting wire havi~g higher critical current density.
In operatio~, a wlre of compound oxide havln~ ~he ~rystal ~truct~re o~ K2NiF4-type oxlde~ such a~ a powder o~
~La,3a~2CuO4 or ~La,Sr]2CuO4 whlch can be obtained ~by ~lntering a material powder mixture o~ oxides, carbonat~s, nitrate, æulfates or the like of the con~tltuent elements of the ~ompcund oxide, for example, a powder ~ixture of La2O3, ~aO2, SrO2, and CuO~
The me~al pipe may be made of a metal se}e~ted from a group compri6ing Ag, Au, Pt, Pd, Rh, Ir, Ru, O~, Cu, Al, Fe~ Nl, Cr, Ti, Mo, W and Ta and of an alloy includln~
these metals as the ba~e.
On particular, it i~ preferab~e to ~elect among Ag, Au~ pla~inum metal~ ~omprising Pt, Pd, Rh, Ir, Ru and O~
and alloys containing them a~ the base me~al. The metal~
of Ag, Au and platinum m~tal~ are almost inactive to the sLperconducting ceramlc ~aterial3 under heat~d condltlon, and hence th~ heat-treatment operatlon can be carried out at a sufflci~ntly high te~perature 80 as t~ accelerate the 1 3383~S
~intering or ~olid-~olid reac~ion among superconductin~
çer~mie particles in the metal pipe to o~ta~n a ~niform elongated arti~le. When the metal pipe ma~e of ~opper is used in pla~e of the platinum metals, there is a possibillty of reaction between ~he superconducting material a~d the copper of the metal plpe, which results in that the composition in the resultlng wire will deviate or fluctuate. Still more, ~lnce ~he copper pipe is apt to be oxldlzed and hence lt ls dificult to perform the heat-treatment at a high temperature. These problem may be avoidable by uQlng the pipe of platinum metals which is ehemi~aily inactlve to the cera~lcs fllled ln the pipe and henee the resu~tlng wire possesses a composltlon whieh i~
uniformly di~tribu~ed along the longitudln~l dire~tion.
Thexefore, the superconducting wir~ whoae outer met~l pipe i8 made o~ platinum metal exhiblts almo~t sa~e ~rltical temperature as a bulk or mass whlch is produced by si~tering from 3ame ~a~erial ceramlc powder and shows much higher critical current denoity in comparl~on with a wire whose outer ~tal pipe i 8 made of eopper.
Ac~ording to the present invention, i~ i~ al50 po~ible to arrange another metal ~uch ~ copper, copper alloy or stainless steel around the ou~er metal pipe. Such additional metal layer will increase the flexibility of the resulting wire which is obtained by plastic deformatlon.
The step of the pl~ti¢ deformatlon of the metal pipe fll~ed wi~h the ceramlc me~al powder 13 preferably carried out under such conditlon that the cross ~ection of the metal plpe ls red~ced at a dlmensional reduction ratio ranging from 16 ~ to 92 ~, more partlcularly from ~Q ~ to 30 %. If the red~ction ratio exceeds 9~ ~, the material ~owder filled in the plpe will not follow or accompany with the movemen~ of the lnner surface of the metal pipe, resulting in breakage of the sintered ceramic wlre in~ide the metal pipe at ~everal points. ~o the contrary, i~ the reduction ratio ls lower ~han 16 %, satisfactory packaging density in the ~etal pipe ~an no~ be expected, so ~hat ~omplete sintering can not be performed, The pla~tic deformation is preferably performed by the technique of w~ ~e-drawing, particularly, ~y means of a die o~ a 6eries of dle~, a roller dle or a serles o~ roller dies, or an extruder or a serles of extruders. The plastic deformation may ~e carried out by orging which 19 p~eferably machlne work~ o$ ~waging or rolling.
It is also po~sible to combi~e mo~e ~han two operations of the abovementiQned plastic deformations of extrusion, rolling, ~waging and other ~l~e drawlng~ It iQ
also possible to ~hape the deformed wire in~o a desired configuration uch as a shape of a coll whlch is applicable to a superconducting m~net or the like before the coil ls heat-treated, The heat-treatment of the metal pipe filied wlth ~he material ceramlc powder which is perform~d af ter the plastic d~formation is preferably carried out at a t 338396 temperature ranging from 700 to 1,000 C which is selecte~
ln the function of the cons~ituent elements o the cera~ics. Thus, the super~onducting powder fllled ln the metai pipe ~re ~e~ained in a ~onditi~ th~t they are conta~ted with each other but are not fu~ed to ~rm ~
continuou5 body even after the pla~tio deformatlon. The heat-treatment promote sintering or reaction amon~ powd~rs to produce a product having the uniformity.
Generally speaking, the temperature at whlch the sin~erlng o~ powder6 of ~omp~und oxide iB performed ic below a meltlng polnt of the ~lntered ~ody which ls the upper llmit and i3 preferably above a temperature which is 100 C lower than the melting point. If the sinterlng temp~rature i~ ~ower than the temperature which ls 100 C
lowe~ than ~he melting point, co~plete sintering r~action ~n not be ~¢hleved and hence the resultin~ pr~duct will not have practical strength. To the contrary, lf the sint~ring temperatue exceeds the upper limit cf meltlng poi~t, llquid phaQe wlll be produced 80 that the slntered ~ody mel~s or de~omposed, re~ultlng in lowering the Tc.
Ac~ording ~o an embodiment~ af t~r the me~al pipe filled with the material powder i& de~ormed or wire-drawn to a~ objective con~iguration, the metal plpe i8 ~ubjected to the ~interin~ operation at a temperature where the super~onductor of compound oxide is not produced but whlch is more than a half or 1/2 of the reactlon temperature in ab~olute temperature to ~uch extent tha~ boundarie~ of the material powders diffuse each other. After the wire-drawing step, it is also preferable to perform an intermediate annealing which is followed by another wire-drawing. If necessary, a combination of the wire-drawing and the intermediate annealing can be repeated for desired times. After then, the sintered composite is subjected to the final treatment including a slow cooling at a rate of less than 50 ~C/min and a rapid cooling at a rate of more than 50 C to obtain the final product of superconductor.
The reasons why the abovementioned procedure is preferable come from such fact that the superconducting ceramic of Y-Ba-Cu-O type compound oxide do not exhibit the property of superconductivity if not it is sintered at a temperature of more than about 900 C and hence one constituent element of Cu in the ceramic is reduced by the reaction with the metal which constitute the outer pipe, which result in deterioration of the superconductivity. To solve this problem, it is preferable to use, as the material powder, such a powder which is prepared by pulverizing a sintered ceramic mass which itself has superconductivity and to perform the sintering operation at a temperature where no reductive reaction occur after the wire-drawing operation.
It is also preferable that, after the sintering or heat-treatment complete, the metal pipe containing sintered ceramic body therein is cooled slowly at a rate of less than 50 C/min. When the process according to the present invention is applied for a sintered ceramic wire o~ Y-Ba-C-l-O type compound ~XL~ ~L ~ rovenent in the property of superconductivity can be ahieved by the heat-treatment including a slow cooling of the sintered body at a rate of less than 50 C/min and a rapid cooling thereof at a rate of more than 50 C.
The outer metal pipe or sheath can be removed after the sintering complete, but if necessary, the outer metal pipe may be remained as it is on the outer surface of the sintered cetamic body in order to improve safety for the magnetic field and to assure heat-radiating passage by way of precausion against a case where superconductivity break accidentially. To the contrary, when inherent properties of sintered ceramic body, such as the resistence to chemicals and the resistance to abrasion are requested, it is preferable to remove the metal pipe off the sintered body (Fig. 1J). The outer metal can be removed off the sintered body mechanically for example by means of grinding work or chemically for example etching liquid such as nitric acid.
In a variation of the process according to the present invention, almost all metal of the metal pipe may be rcmovcd during the ~intering ~tep, n~m_ly ~oth of slllt~
and removal of the metal are carried out simultaneously, with leaving a very thin skin layer on the surface of the sintered body. The thickness of the thin skin layer left on the surface of the sintered body is less than 500~um, preferably less than 200 ~m, so that the thin skin layer left on the surface is held on the surface even if the metal fuse during the sintering operation owing to its surface tension withiout dropping of the fused metal.
It is also possible to carry out both of the plastic deformation for reducing the cross sectional dimention of the metal pipe and the heat-treatment simultaneously in order to complete two operations of sintering of the material powder and defor~ation of the metal pipe by means of hot-working. In this case, the reduction ratio in cross sectional direction of the metal pipe is preferably from 40 % to g5 %.
The hot-working means working, treatment or a metal processing which is carried out at a temperature which is higher than recrystallization temperature of a metal of the meta~ pipe. Thus, the metal pipe exhibits -higher malleability above the recrystaline temperature because metal lost considerably its resistance against deformation.
Still more, work hardening will not left even if recrystallization of the metal take place after it is quenched. Of course, this hot-working is performed below the melting point of metal, but preferably, it is performed at a temperature which is 10 C lower than the melting point.
It is preferable that the plastic deformation is performed by such a metal working or processing that comprssive stress is effected onto an article to be worked such as wire-drawing and forging operations, so as to make the material powder filled in the metal pipe be compacted.
It is also possible to adopt such sequence of steps comprising, after the plastic deformation such as wire-drawing for reducing the cross sectional dimention of the metal pipe complete, subjecting the deformed pipe to an intermediate annealing at a temperature where the metal pipe is annealed, further carrying out plastic deformatlon such as wlre-drawing of the annealed pipe, and then subjecting the resultlng pipe to the final heat-treatment to sinter the material ceramic powder filled in the metal pipe. In this case, the metal pipe may be removed off after the intermediate annealing and the first annealing but before the final sintering of the material cera~ic powder in order to prevent undesirable reaction between the ceramic powder and the metal of the metal pipe at a high sintering temperaure. It is also possible to repeat another intermediate annealing after the first wire-drawing following the first intermediate annealing, so that, after then, the metal pipe is removed off after the repeated second intermediate annealing before the final sintering.

A~ )rAin~ t~ thl~ s~quence of op~rationc compri~ing th~
first annealing, wire-drawing and the second annealing, the second annealing give advantageously enough strength which can resiste against external force excerted to the annealed article and/or a desired configuration to the annealed body, before it is passed to and during it is maintained in the final sintering furnace in which the annealed article is sintered with no outer metal pipe. The combination of the wire-drawlng and the intermediate annealing can be repeated for desired times to increase the dimentional reduction ratio in the cross sectional direction with no breakage of a wire, and hence the resulting wire shows a fine diameter and higher strength.
The intermediate annealing may be performed in one of two temperature ranges of (1) the first temperature range where the metal pipe is annealed but ceramic powder is not sintered and (2) the second temperature range where the metal pipe is annealed and the ceramic powder is also sintered.
~ f the intermediate annealing following the wire-drawing is per~ormed in the first temperature range ~1~
where the metal pipe is annealed but ceramic powder is not sintered, higher dimentional reduction ratio can be achieved to obtain a fine ceramic wire having satisfactory deflection strength with no breakage. In this case, the intermediate annealing can be performed at a suitable temperature which is selected in function of the kind of metal of the metal pipe and componets and composition of the ceramic powder.
In case of a combination o~ a metal pipe having relatively higher anneling temperaure and a material ceramic powder having relatively lower sintering temperature, it is preferable to adopt the second temperature range (2) where the metal pipe is annealed and the ceramic powder is also sintered.
It is also possible to add a cold working step before and/or after the hot working step. Still more, it is also possible to repeat the series of steps including the abovementioned hot working and sintering step for several times.
According to a special variation of the process of the present invention, through holes which pass through a wall of the metal pipe are made after the plastic deformation complete, so that the material ceramic powder filled in the perforated metal pipe is sintered in an open conAiti~n.
In this variation, after the wire drawing, the wall of the metal pipe of the wire is perforated by means of laser, electron beam or a microdrill or the like, so as to permit passage of gas, particularly oxygen containing gas through the perforations or holes. If the metal pipe is not perforated, the material ceramic powder is sintered under a closed or sealed condition in the outer metal pipe in the sintering stage , so that oxygen deficient of the compound oxide exceed too much to obtain a product having superiox superconductivity. Therefore, it is preferable to make through holes in the wall and to carry out the sintering of the metal pipe in an atmosphere containing oxygen gas to supply a proper amount of oxygen to the compound oxide in the ~etal pipe. It is the general property of superconducting compound oxides that the superconductivity is influenced by the oxygen deficinecy in the crystal structure. In other words, the oxygen deficiency as well as the crystal structure of the resulting sintered wlre are keys of the superconductivity. Therefore, it is important to adjust atom ratios of elements so as to satisfy the abovementioned ranges of elements defined in connection with the general formula : ( d 1 -X, ~ X ) y y oz as well as to fulfill the abovementioned procedure according to the present invention in order to adjust the oxygen contents defined by the general formula. Otherwise, the value of Tc can not be improved owing to different crystal structure and improper oxygen deficiency.
According to the abovementioned special variant, satisfactory oxygen can be supplied through the through holes or a slit made in the outer metal layer, so that the resulting sintered body of compound oxide possess a crystal structure of so to say quasiperovskite type crystal structure such as orthorhombic structure or the like which can produce Cooper pairs at higher possibility.
The through holes or slit is preferably closed by filling them with sealing mateial or by covering the whole outer surface of the metal pipe with another metal seath or covering in order to protect the compound oxide from deterioration due to attack by surrounding humid gas.
It is also preferable to increase the partial pressure of oxygen gas during the sintering stage in order to promote penetration of oxygen gas through the holes or slits.

Now, the process according to the present invention will be described with reference to illustrative Examples, but the scope of the present invention should not be limited thereto.

Example 1 As a material powder to be sintered, a powder mixture of 85 % by weight of La2O3, 4 ~ by weight of BaCO3 and 11 %
by weight of CuO was used. The powder mixture was compacked and then sintered at the conditions of 900 C, for 24 hours. The resulting sintered body itself exhibited superconductivity.
The sintered body was then pulverized into powder and was compacted in a copper pipe having an inner diameter of 5 mm and a wall thickness of 0.3 mm. The metal pipe filled with the sintered powder was then heat-treated at 850 C
for 10 hours to sinter the powder. After the sintering completed, the copper pipe thus treated was caulked without cooling it.
The resulting superconducting wire showed Tc of 30 K
and was able to bend up to a curvature of 300 mm.

Example 2 l 338396 As a material powder to be sintered, a powder mixture of 85 % by weight of La203, 2 % by weight of SrO and 13 %
by weight of CuO was compacted in a copper pipe having an inner diameter of 10 mm and a wall thickness of 1 mm. The metal pipe filled with the powder mixture was heat-treated at 850 C for 24 hours. And then, before the pipe lost heat, the copper pipe thus treated was wire-drawn to such extent that the the diameter of the copper pipe became to 2 mm under a hot condition.
The resulting superconducting wire showed Tc of 35 K
and was able to ~end up to a curvature of lOO mm.

Example 3 8~.5 % by weight of commercially available La203 powder, 3.1 % by weight of commercially available SrC03 and 11.4 % by weight of commercially available CuO were mixed in an attoriter in wet and then dried. The dried powder was compacted in a press under a pressure of 100 kg/cm2 and then sintered at 900 C in air for 20 hours. The sintered body was pulverized and passed through a sieve to obtain powder of lOO mesh under.
After treatment of granulation, the material powder was compacked in a copper pipe having an outer diameter of 5 mm, an inner diameter of 4 mm and a length of 1 m and opposite ends of the pipe were seale. The pipe filled with the material powder was subjected to wire-drawing to reduce t 338396 its outer diameter down to 1.8 mm and then sintered at 1,050 C, for 2 hours in vacuum. The resulting sintered ceramic wire was covered with a copper sheath having a wall thickness of 0.2 mm and had a length of 7.7 m.
The measured value of the critical temperature (Tc) where this sintered ceramic wire exhibited superconductivity was 35.~ K. The. ceramic wire showed the defiective strength of 24.7 kg/cm2 and the rupture toughness (KIC)of 2.2 MN/m3/2.

Example 4 The same material powder as Example 3 was compacted in five pipes of iron having an outer diameter of 6 mm, an inner diameter of 5 mm and a length of 50 cm and opposite ends of each pipe were sealed. The pipes filled with the material powder were subjected to wire-drawing so as to reduce their outer diameter at the dimentional reducction ratios of 95 %, 88 %, 56 %, 37 % and 14 ~ respectively and then were heat-treated at 1,100 C for 2 hours in vacuum to sinter the material powder.
After then, the outer irron pipe or seath was removed by washing it with acid. The result showed such a fact that a sintered ceramic wire which was wire-drawn at the dimentional reduction ratio of 95 % brake into nine pieces and a sintered ceramic wire which was wire-drawn at the dimentional reduction ratio of 14 % was not sintered sompletely and hence could not keep its shape, while the other three sintered ceramic wires were sintered completely with no breakage.

Example 5 The same materlal powder as Example 3 was compacted in five pipes of nickel having an outer diameter of 6 mm, an inner diameter of 5 mm and a length of 1 m and opposite ends of each pipe were sealed. ~he pipes filled with the material powder were subjected to wire-drawing to reduce the outer diameter down to 2.0 mm and then was heat-treated at 1,150 C for 2 hours to sinter the material powder.
After then, the outer nickel pipe or sheath was removed mechanically by cutting operation to obtain a sintered ceramic wire having a diameter of 1.6 mm and a length of 9 m.
The measured value of the critical temperature (Tc) where this sintered ceramic wire exhibited superconductivity was 37.0 K. The ceramic wire showed the deflective strength of 24.4 kg/cm2 and the rupture toughness (KIc)of 2.1 MN/m3/2.

Example 6 The same material powder as Example 3 was compacted in five pipes of silver having an outer diameter of 6 mm, an inner diameter of 5 mm and a length of 1 m and opposite ends of each pipe were sealed. The pipes filled with the material powder were subjected to wire-drawing to reduce the outer diameter down to 2.0 mm and then was heat-treated at g53C for 2 hours to sinter the material powder.
After then, the outer silver pipe or sheath was removed mechanically by cutting operation to obtain a sintered ceramic wire having a diameter of 1.5 mm and a length of 6.3 m.
The measured value of the critical temperature (Tc) where this sintered ceramic wire exhibited superconductivity was 37.0 K.

Example 7 85.5 ~ by weight of commercially available La203 powder, 3.1 ~ by weight of commercially available SrC03 and 11.4 ~ by weight of commercially available CuO were mixed in an attoriter in wet and then dried. The dried powder was compacted in a press under a pressure of 100 kg/cm2 and then sintered at 900 C in air for 20 hours. The sintered body was pulverized and passed through a sieve to obtain powder of 100 mesh under.
After treatment of granulation, the material powder was compacted in an iron pipe having an outer diameter of 5 mm, an inner diameter of 4 mm and a length of 1 m and opposite ends of the pipe were sealed. The pipe filled with the material powder was subjected to wire-drawing to reduce its outer diameter down to 1.8 mm and then sintered at 1,050 C, for 2 hours in vacuum. The resulting sintered ceramic wlre was covered with an iron sheath having a wall thickness of 0.2 mm and had a length of 7.7 m.
The measured value of the critical temperature (Tc) where this sintered ceramic wire exhibited superconductivity was 35.1 K. The ceramic wire showed the deflective strength of 25.1 kg/cm2 and the rupture toughness (KIC)of 2.1 MN/m3/2.

Example 8 The same material powder as Example 7 was compacted in seven pipes of iron having an outer diameter of 6 mm, an inner diameter of 5 mm and a length of 50 cm and opposite ends of each pipe were sealed. The pipes filled with the material powder were subjected to wire-drawing so as to reduce their outer diameter at the dimensional reduction ratios of 95 %, 90 %, 83 %, 56 ~, 37 ~, 20 % and 14 %
respectively and then were heat-treated at 1,100 C for 2 hours in vacuum to sinter the material powder.
After then, the outer iron pipe or sheath was removed by washing it with acid. The result showed such a fact that a sintered ceramic wire which was wire-drawn at the dimensional reduction ratio of 95 % broke into ten pieces while a sintered ceramic wire which was wire-drawn at the dimensional reduction ratio of 14 ~ was not sintered completely and hence could not keep its shape, while the other three sintered ceramic wires were sintered completely with no ~reakage.

Example 9 The same material powder as Example 7 was compacted in five pipes of nickel having an outer diameter of 6 mm, an inner diameter of 5 mm and a length of 1 m and opposite ends of each pipe were sealed. The pipes filled with the material powder were subjected to wire-drawing to reduce the outer diameter down to 2.0 mm and then was heat-treated at 1,150 C for 2 hours to sinter the material powder.
After then, the outer nickel pipe or sheath was removed mechanically by cutting operation to obtain a sintered ceramic wire having a diameter of 1.6 mm and a length of 9 m.
The measured value of the critical temperature ~Tc) where this sintered ceramic wire exhibited superconductivity was 35.8 K. The ceramic wire showed the deflective strength of 24.9 kg/cm2 and the rupture toughness IKIc)of 2.2 MN/m3/2.

Example 10 superconducting ceramic powder (an average particle size of 3 ~m) havin~ iti~n ~f YO,g~rO.2~ was_ compacted in a pipe of platinum. Then, the resulting platinum pipe was inserted into an outer pipe of oxygen-free copper. The composite pipe comprising the platinum pipe filled with the ceramic powder and covered by the outer oxygen-free copper pipe was subjected to metal workings of extrusion and wire-drawing to reduce its outer 1 3383q6 diameter to 0.8 mm. The composite pipe showed an areal ratio of Cu : Pt : ceramic = 10 : l : 2 in its cross section .
The composlte pipe was heat=treated at 900 C for 12 hours in air to sinter the material powder inside the metal pipes.
The resulting superconducting wire showed Tc o~ 100 K
which was almost same level of superconductivity as a tablet which was produced by steps of press-molding and then sintering the same powder as the abovementioned Example 10 and which showed Tc of 105 K.
For comparison, the abovementioned composite pipe which was not subjected to the heat-treat~ent did not show any superconductivity even in li~uid helium (4.2 K).

Example 11 A powder mixture of 20.8 % by weight of Y2O3, 54.7 %
by weight of Ba2CO3 and 24.5 % by weight of CuO was compacted in a silver pipe having an outer diameter of 6 mm, an inner diameter of S mm and a length of ~ m. after the opposite end of the pipe were sealed, the pipe W2S
subjected to wire-drawing to reduce its outer diameter to 2.0 mm and after then was heated at 950 C for 2 hours to sinter the powder mixture. After then, the outer silver pipe or sheath was removed mechanically by cutting wor~ to obtain a sintered ceramic wire having a diameter of 1.5 mm and a length of 6.3 m.

The measured value of the critical temperature ~Tc) where this sintered ceramic wire exhibited superconductivity was 87.0 K.

Example 12 A ceramic powder which had been preliminarily sintered was finally sintered at a 920 C for 20 hours to produce a powder having an average particle size of 0.1 Jum and having a composition of YBa2Cu307. The resulting sintered body was pulverized again to produce a material powder of 0.1 mm which was then filled in a stainless steel pipe having an inner diameter of 5 mm and an outer diameter of 9 mm. The pipes filled with the material powder were su~jected to wire-drawing to reduce the outer diameter to 2 mm.
The critical temperature (Tc) of this sintered ceramic wire was 97 K and the critical current density was 103 A/cm2 .
For comp~ri ~)n, ~h~ ~mf~ ~rAmi ~ w~l~r whl rh h~l h~Pn preliminarily sintered as Example 12 was molded into a tablet and the this tablet was heat-treated at the same condition as Example 12. After the tablet was pulverized, the re~ulting powder was compacted in a stainless steel pipe and then subjected to wire-drawing under the same condition as Example 12. The superconducting wire obtained showed the critical temperature (Tc) of 92 K and the critical current density was 12A/cm2.

This fact revealed that the superconducting wire manufacture according to Examp1e 12 possess higher critical current density.

Example 13 20.8 % by weight of commercially available Y203 powder, 54.7 % by weight of commercially available BaCO3 and 24.5 % by weight of commercially available CuO were mlxed in an attoriter in wet and then dried. The dried powder was sintered at 880 C in air for 24 hours. The sintered body was pulverized and passed through a sieve to obtain powder of 100 mesh under. The steps including sintering, pulverization and screening were repeated for three times.
After treatment of granulation, the material powder was compacted in an iron pipe having an outer diameter of 5 mm, an inner dia~eter of 4 mm and a length of 1 m and opposite ends of the pipe were sealed.
When the pipe filled with the material powder was subjected to a series of works of wire-drawing in such manner that its outer diameter was reduced at the cross sectional reduction ratio of 19 % per one pass, the pipe bro~e when the outer diameter thereof was reduced to 1.2 mm.
Therefore, the wire-drawing was ceased when the outer diameter reduced to a value of 1.5 ~m. And then, the pipe was subjected to a series of operation co~prising an intermediate annealing at 750 C for 25 hours, a plurality of wire-drawings each of which was carried out at the cross sectional reduction ratio of 18 ~ per pass so that the pipe was reduced to o.6 mm in diameter, and a sintering at 930 C for 3 hours.
The measured value of the critical temperature (Tc) was 38 K.

~xample 14 20.8 % by weight of commercially available Y203 powder, 54.7 % ~y weight of commercially available BaCO3 and 24.5 % by weight of commercially available CuO were mixed in an attoriter in wet and then dried. The dried powder was sintered at 9S0 C in air for 3 hours. The sintered body was pulverized and passed through a sieve to obtain powder of 100 mesh under. The steps including sintering, pulverization and screening were repeated for three times.
The resulting material powder was compacted in a set of stainless steel pipes each having an outer diameter of 5 mm, an inner diameter of 4 mm and a length of 1 m and opposite ends of the pipe were sealed.
After the pipes were subjected to wire-drawing to reduce their outer diameter to 3.6 mm, they were sintered in air under the following different conditions:
~ 1) at 950 C for 3 hours (2) at 850 C for 3 hours

(3) at 700 C for 3 hours

(4) at 500 C for 3 hours (~) at 850 C for 30 hours (6) at 700 C for 30 hours ~7) at 500 C for 30 hours The resulting sintered ceramic wires had a length of 1.6 m and an outer metal layer of 0.4 mm thick.
Electrical resistance was measured to evaluate the propertles as superconductor. Following is the result of the measurement.
(In the description hereinafter, Tc means the critical temperature of superconductivity and Tcf means a temperature at which electrical resistance become utterly zero) In case of the condition (1), no superconductivity was observed. Color of a sliced cross section was red due to reduction of copper oxide CuO in the ceramic powder.
In case of the condition (2), Tc observed was 58 K and Tcf observed was 7 K. Observation of a sliced cross section revealed that CuO was not apparently reduced but changed to rather porous mass in comparison with the original sintered body from which the materiel powder was prepared.
In case of the condition of (3), no superconductivity was observed. Observation of a sliced section revealed that the ceramic ma~erial was not sintered completely but remained in a condition of granules.

In case of the condition of (4), no superconductivity was observed. Observation of a sliced cross section revealed that the material powder was hardly changed but remained in a powdered condition.
In case of the condition of (5), It was measured that Tc was 84 K and Tcf was 7~ K. Observation of a sliced cross section revealed that the sintered ceramic body possessed almost same color and appearance as the original ceramic body from which the material powder was prepared.
In case of the condition of ~6), Tc was 68 K and Tcf Was 47 K. A sliced cress section was observed to be similar to that of the condition ~5~ but a little porous.
In case of the condition of ~7), no superconductivity was observed. A sliced section revealed that the ceramic powder remained in granular.

Example 15 Powders of BaCO3, Y203 and CuO each having a purity of more than 99.9 % were prepared. They were weighed in such manner that the proportions of BaCO3 : Y203 CuO became 20.8 : 54.7 : 24.5 by weight and mixed uniformly in an attritor in wet. After the mixture was dried at 110 C for 1 hour, it was compacted under a pressure of 100 kg/cm2.
The resulting compact was sintered at 940 C for 15 hours and then pulverized to obtain powder of 100 mesh under.
Then, the abovementioned steps of compacting, sintering and pulverization were repeated for three times. Obtained powder was used in following wire-drawing stage described in Table 1. In this Example 15, a pipe of silver was used A variety of operational conditions and combinations of procedures adopted are summarized in Table 1.
The density (~) of the resulting sintered mass was determined by dividing the weight of a sample by a volume obtained by the specific gravity measurement method in which pores displaced with solution is calculated and it result was verified by dott-counting by means of a microscope. The current density (A/cm2) thereof were determined by dividing the value of current just before a resistance appeared by a cross sectional area of a current passage. The result are also summarized in Table 1.

Example 16 The same material powder as Example 15 was used and the same procedure as Example 15 was repeated except that the material powder was compacted in metal pipes of Al, Cu and Ni respectively.
The density t~) of the resulting sintered mass and the current density (A/cm2~ thereof were determined by the same method as abovementioned. The result are summarized in Table 2.

T A B L E

Critical Sample Material ~anufacturing Process Density Current N'~ of Pipe ( Operational condition ) (%) Oensity (A/c~
Ag-1 Ag Wire-drawing by dies from 20mm ~ to 62 150 6 m~ ~ in air and then Sintering Ag-2 Ag Swaging in air from 20mm ~ to 6 mm ~ 68 210 and then Sinterin~.

Ag-3 Ag Swaging at 900 ~ from 20mm ~ to 6 m0 ~ 87 570 and then Sintering.

Ag-4 -Ag Swaging at 900~ from 20~m~ to 10mm and then Sintering. After then, secondary Swaging at 900~ fro~ 95 870 lOmm ~ to 6 mm~ and then Sintering.
Ag-5 Ag Swaging at 900 ~ fro~ 20mm ~ to 10mm~ and then Sintering. After then, secondary Swaging in air from 10mm ~ 93 800 to 6mm ~ and then Sintering.

Ag-6 Ag Swaging at 900 ~ from 20mm ~ to 6 mm ~ 81 450 and then Sintering.

Ag-7 Ag Swaging at 950~ from 20mm ~ to 6 mm ~ note and the~ Sintering.

Note: In this sample, the pipe ruptured due to poor strength of Ag, and could not measured.

I Critica~
Sample Material ~anufacturing Process Density Current ~o. I of Pipe {%) Density (A/c~) Al-1 Al Swaging at 600 ~ fro~ 20mm ~ to 2 mm ~ 75 280 and then Sintering (600C 20h) Ag-2 Ag Swaging in air fro~ 20mm ~ to 2 mm ~ 58 75 and then Sintering (600~ 20h) Cu-1 Cu Swaging at 600C fro~ 20mm~ to 2 mm ~ 80 350 and then Sintering (800~ 15h) Cu-2 Cu Swaging in air from 20mm ~ to 2 mm ~ 61 100 and then Sintering ~800 ~ 15h) Ni-1 Ni Swaging at 800 ~ from 20mm~ to 2 mm ~ 89 370 and then Sintering (900C 15h) Ni-2 Ni Swaging in air from 20mm ~ to 2 mm ~ 63 110 and then Sintering (900~ 15h) Example 17 1 3 3 8 3 9 6 Powders of BaCO3, Y203 and CuO each having a purity of more than 99.g % and an average partlcle size of 1 um were prepared. They were mixed with such a proportion that Ba Y
and Cu are satisfied a composition of :
Bao.67Y0.33Cu103-S
in other words, the atom ratios of ~a : Y : Cu became 2:1:3 (the proportions of BaCO3 : Y2O3 CuO = 52.9 : 15.13 :
31.98 by weight) and then were kneaded in wet for 3 hours in a mortal. The resulting powder mixture was dried at 200 C for 7 hours in vacuum to remove water.
The dried powder was sintered in air at 930 C for 24 hours and then the resulting cake-like mass was pulverized in a mortal and further milled in a ball-mill to reduce it to an average particle size of less than 30~um.
The powder obtained was compacted in a pipe of stainless steel (SUS 310S) and opposite ends of the pipe were sealed. The pipe filled with the powder therein was subjected to repetitive operations of wire-drawing each of which was performed at a dimensional reduction ratio of 25 % so that an outer diameter of the pipe was finally reduced to 1.8 mm.
Innumerable through holes each havlng a diameter of 200 ~m were perforated in the pipe at a pitch of 20 mm by means of CO2 laser.
Then, the perforated pipe was heat-treated at 1,000 C
for 16 hours to sinter the powder and then cooled slowly at a rate of 10 C/min. The sintering temperatures were selected in a rage where no fusion of the metal pipe occurred. Then, the pipe was heat-treated at 700 C for 10 hours and then cooled slowly at a rate of 10 C/min.
The same procedure as abovementioned was repeated for a variety of compositions of material powder and pipes of different metals which are listed in Table 3 in which ~ , ~ , x and y mean elements and atom ratios in following formula:
~ x, ~x )2Cuy 04 The result is summarized in the Table 3 in which Tci stands for the temperature at which resistance started to drop and Jc was the value of critical current density measured at 77 K. The result is summarized in Table 3.

Table 3 Sample ~ ~ x Y Material Sintering Tci Jc No. of pipe temp.~C) (~K) ~A/cm2) 1 Ba Y 0.33 1.0 Stainless* 1,000 941,000 2 Ba Y 0.33 1.0 A1 900 90 800 3 Ba Y 0.33 1.0 Cu 1,000 951,100 4 Ba Y 0.33 1.0 Fe 1,040 91 900 Ba Y 0.33 1.0 Ni 1,040 92 850 6 Ba Y 0.33 1.0 Ta 1,030 941,050 7 Ba Y 0.33 l.0 Ag 900 91 900 8 Ba Y 0.4 1.1 S~ainless* 1,00088 700 9 Ba Y 0.5 1.21 Stainless* 1,00085 600 Ba Ho 0.33 1.0 Stainless* 1,0 ~ 91 800 11 Ba Dy 0.33 1.0 Stainless* 1,000 92 1,000 12 Sr La 0.75 0.5 Stainless* 1,000 41 600 13 Ba La 0.75 0.4 Stainless* 1,000 43 700 14 Ba Y 0.33 0.4 Stainless* l,000 88 900 Ba Y 0.33 0.6 Stainless* 1,000 85 800 *--- The Stainless means SUS310S.

Example 18 l 338396 36.42 % by weight of commercially available Bi203 powder, 23.07 % by weight of commercially available SrC03, Z3.07 % by weight of commercially available CaC03 and 24.87 % by weight of commercial~y available CuO were mixed in an attoriter in wet and then dried. The dried powder was compacted under a pressure of 1,000 kg/cm2 and then sintered at 800 C in air for 8 hours. The sintered body was pulverized and passed through a sieve to obtain powder of 100 mesh under.
After treatment of granulation, the material powder was compacted in a silver pipe having an outer diameter of

5 mm, an inner diameter of 4 mm and a length of 1 m and opposite ends of the pipe were sealed.
When the ~ipe filled with the material powder was subjected to wire-drawing to reduce its outer diameter to l.8 mm. And then, the pipe was sintered at 800 C for 2 hours to obtain a sintered ceramic wire having a length of 5.0 m and having an outer coating of silver layer of 0.3 mm thick.
The measured value of the critical temperature (Tc) of this sintered ceramic wire was 100 K.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for manufacturing a superconducting elongated article including steps comprising filling a metal pipe with material powder of ceramic consisting of compound oxide having superconductivity, performing plastic deformation of the metal pipe filled with the ceramic metal powder to reduce the cross section of the metal pipe, and then subjecting the deformed metal pipe to heat-treatment to sinter the ceramic material powder filled in the metal pipe.

2. Process claimed in Claim 1, characterized in that said ceramic material powder contain compound oxide having the crystal structure of K2NiF4-type oxides.

3. Process claimed in Claim 2, characterized in that said ceramic material powder is [La, Ba]2CuO4 or [La, Sr]2CuO4

4. Process claimed in Claim 1, characterized in that said ceramic material powder contain compound oxide having Perovskite-type crystal structure exhibiting superconductivity having the general formula:
( ? 1-x, ? x ) ? y Oz wherein ? stands for an element selected from IIa group elements of the Periodic Table, .beta. stands for an element selected from IIIa elements of the Periodic Table, ? stands for an element selected from a group comprising Ib, IIb, IIIb, IVa and VIIIa elements of the Periodic Table, x, y and z are numbers which satisfy following respective ranges:
0.1 x 0.9, 0.4 y 4.0, and 1 z 5.

5. Process claimed in Claim 4, characterized in that said ? is Ba, .beta. is Y and ? is Cu.

6. Process claimed in Claim 1, characterized in that said ceramic material powder is prepared by steps comprising mixing powders of Bi2O3, SrCO3, CaCO3 and CuO, drying and then compacting the powder mixture, sintering the compacted mass, and then pulverizing the sintered mass.

7. Process claimed in Claim 1, characterized in that said metal pipe is selected from a group comprising metals of Ag, Au, Pt, Pd, Rh, Ir, Ru, Os, Cu, Al, Fe, Ni, Cr, Ti, Mo, W and Ta and alloys including these metals as the base.

8. Process claimed in Claim 1, characterized in that said heat-treatment is carried out at a temperature ranging from 700 to 1,000 °C.

9. Process claimed in Claim 1, characterized in that said plastic deformation of the metal pipe filled with the ceramic metal powder is performed in such manner that the cross section of the metal pipe is reduced at a dimensional reduction ratio ranging from 16 % to 92 %.

10. Process claimed in Claim 9, characterized in that said plastic deformation is performed by wire-drawing.

11. Process claimed in Claim 10, characterized in that said wire-drawing is performed by means of dies, roller dies, or extruder.

12. Process claimed in Claim 9, characterized in that said plastic deformation is performed by forging.

13. Process claimed in Claim 12, characterized in that said forging is performed by means of swaging unit or rolls.

14. Process claimed in Claim 1, characterized in that said material powder of ceramic consisting of compound oxide having superconductivity is granulated previously.

12. Process claimed in Claim 1, characterized in that, after the heat-treatment is completed, the metal pipe containing sintered ceramic material powder therein is cooled slowly at a rate of less than 50 °C/min.

16. A process for manufacturing a superconducting elongated article including steps comprising charging material powder of ceramic consisting of compound oxide having superconductivity into a metal pipe made of one of metals of Ag, Au, Pt, Pd, Rh, Ir, Ru, Os, Cu, Al, Fe, Ni, Cr, Ti, Mo, W and Ta or alloys including these metals as the base, performing plastic deformation of the metal pipe filled with the ceramic metal powder therein to reduce the cross section of the metal pipe to such extent that the cross section of the metal pipe is reduced at a dimensional reduction ratio ranging from 16 % to 92 %, and then subjecting the deformed metal pipe to heat-treatment at a temperature ranging from 700 to 1,000 °C to sinter the ceramic material powder filled in the metal pipe.

17. Process claimed in Claim 16, characterized in that said plastic deformation is performed by wire-drawing.

18. Process claimed in Claim 17, characterized in that said wire-drawing is performed by means of dies, roller dies, or extruder.

19. Process claimed in Claim 16, characterized in that said plastic deformation is performed by forging.

20. Process claimed in Claim 19, characterized in that said forging is performed by means of swaging unit or rolls.

21. Process claimed in Claim 16, characterized in that said ceramic material powder contain compound oxide having the crystal structure of K2NiF4-type oxides.

22. Process claimed in Claim 17, characterized in that said ceramic material powder is [La, Ba]2CuO4 or [La, Sr]2CuO4.

23. Process claimed in Claim 16, characterized in that said ceramic material powder contain compound oxide having Perovskite-type crystal structure exhibiting superconductivity having the general formula:
( ? 1-x, .beta. x ) ? y Oz wherein ? stands for an element selected from IIa group elements of the Periodic Table, .beta. stands for an element selected from IIIa elements of the Periodic Table, ? stands for an element selected from a group comprising Ib, IIb, IIIb, IVa and VIIIa elements of the Periodic Table, x, y and z are numbers which satisfy following respective ranges:

0.1 ? x ? 0.9, 0.4 ? y ? 4.0, and 1 ? z ? 5.

24. Process claimed in Claim 16, characterized in that said .alpha. is Ba, .beta. is Y and ? is Cu.

25. Process claimed in Claim 16, characterized in that said material powder of ceramic consisting of compound oxide having superconductivity is granulated previously.

26. Process claimed in Claim 16 , characterized in that, after the heat-treatment complete, the metal pipe containing sintered ceramic material powder therein is cooled slowly at a rate of less than 50 °C/min.

27. A process for manufacturing a superconducting elongated article including steps comprising filling a metal pipe with material powder of ceramic consisting of compound oxide having superconductivity, performing hot-plastic deformation of the metal pipe filled with the ceramic metal powder to reduce the cross section of the metal pipe under a heated condition so that the ceramic material powder filled in the metal pipe is sinter.

28. Process claimed in Claim 27, characterized in that said metal pipe is selected from a group comprising metals of Ag, Au, Pt, Pd, Rh, Ir, Ru, Os, Cu, Al, Fe, Ni, Cr, Ti, Mo, W and Ta and alloys including these metals as the base.

29. Process claimed in Claim 27, characterized in that said hot-plastic deformation is carried out at a temperature ranging from 700 to 1,000 °C.

30. Process claimed in Claim 27, characterized in that the cross section of the metal pipe is reduced at a dimensional reduction ratio ranging from 16 % to 92 %.

31. Process claimed in Claim 30, characterized in that said hot-plastic deformation is performed by wire-drawing.

32. Process claimed in Claim 31, characterized in that said wire-drawing is performed by means of dies, roller dies, or extruder.

33. Process claimed in Claim 30, characterized in that said plastic deformation is performed by forging.

34. Process claimed in Claim 33, characterized in that said forging is performed by means of swaging unit or rolls.

35. Process claimed in Claim 27, characterized in that said material powder of ceramic consisting of compound oxide having superconductivity is granulated previously.

36. Process claimed in Claim 27, characterized in that, after the heat-treatment is completed, the metal pipe containing sintered ceramic material powder therein is cooled slowly at a rate of less than 50 °C/min.

37. Process claimed in Claim 27, characterized by further including at least one step of cold-plastic deformation of the metal pipe, before and/or after said hot-plastic deformation.

38. Process claimed in Claim 27, characterized in that a series of operations including said hot-plastic deformation and said sintering step is repeated for more than two times.

39. A process for manufacturing a superconducting elongated article including steps comprising charging material powder of ceramic consisting of compound oxide having superconductivity into a metal pipe made of one of metals of Ag, Au, Pt, Pd, Rh, Ir, Ru, Os, Cu, Al, Fe, Ni, Cr, Ti, Mo, W and Ta or alloys including these metals as the base, performing hot-plastic deformation of the metal pipe filled with the ceramic metal powder therein to reduce the cross section of the metal pipe to such extent that the cross section of the metal pipe is reduced at a dimensional reduction ratio ranging from 16 % to 92 %, under a heated condition so that the ceramic material powder filled in the metal pipe is sintered.

40. Process claimed in claim 39, characterized in that said hot-plastic deformation is performed by wire-drawing.

41. Process claimed in Claim 40, characterized in that said wire-drawing is performed by means of dies, roller dies, or extruder.

42. Process claimed in Claim 39, characterized in that said plastic deformation is performed by forging.

43. Process claimed in Claim 42, characterized in that said forging is performed by means of swaging unit or rolls.

44. Process claimed in Claim 39, characterized in that said ceramic material powder contain compound oxide having the crystal structure of K2NiF4-type oxides.

45. Process claimed in Claim 44, characterized in that said ceramic material powder is [La, Ba]2CuO4 or [La, Sr]2CuO4

46. Process claimed in Claim 39, characterized in that said ceramic material powder contain compound oxide having Perovskite-type crystal structure exhibiting superconductivity having the general formula:
( .alpha. 1-x, .beta. x ) ? y Oz wherein .alpha. stands for an element selected from IIa group elements of the Periodic Table, .beta. stands for an element selected from IIIa elements of the Periodic Table, ? stands for an element selected from a group comprising Ib, IIb, IIIb, IVa and VIIIa elements of the Periodic Table, x, y and z are numbers which satisfy following respective ranges:
0.1 ? x ? 0.9, 0.4 ? y ? 4.0, and 1 ? z ? 5.

47. Process claimed in Claim 46, characterized in that said .alpha. is Ba, .beta. is Y and ? is Cu.

48. Process claimed in Claim 39, characterized in that said material powder of ceramic consisting of compound oxide having superconductivity is granulated previously.

49. Process claimed in Claim 39, characterized in that, after the heat-treatment is completed, the metal pipe containing sintered ceramic material powder therein is cooled slowly at a rate of less than 50 °C/min.

50. Process claimed in any one of Claims 1, 16, and 39, characterized by including a further step of removing the metal pipe from a sintered body produced from the material ceramic powder, after the sintering is completed.

51. A process for manufacturing a superconducting elongated article including steps comprising filling a metal pipe with material powder of ceramic consisting of compound oxide having superconductivity, performing plastic deformation of the metal pipe filled with the ceramic metal powder to reduce the cross section of the metal pipe, subjecting the deformed metal pipe to an intermediate annealing at such a temperature that the metal pipe is annealed , performing another plastic deformation, and then subjecting the deformed metal pipe to heat-treatment to sinter the ceramic material powder filled in the metal pipe.

52. Process claimed in Claim 51, characterized in that said ceramic material powder contain compound oxide having the crystal structure of K2NiF4-type oxides.

53. Process claimed in Claim 52, characterized in that said ceramic material powder is [La, Ba]2CuO4 or [La, Sr]2CuO4.

54. Process claimed in Claim 51, characterized in that said ceramic material powder contain compound oxide having Perovskite-type crystal structure exhibiting superconductivity having the general formula:
( .alpha. 1-x, .beta. x ) ? y Oz wherein .alpha. stands for an element selected from IIa group elements of the Periodic Table, .beta. stands for an element selected from IIIa elements of the Periodic Table, ? stands for an element selected from a group comprising Ib, IIb, IIIb, IVa and VIIIa elements of the Periodic Table, x, y and z are numbers which satisfy following respective ranges:
0.1 ? x ? 0.9, 0.4 ? y ? 4.0, and 1 ? z ? 5.

55. Process claimed in Claim 54, characterized in that said .alpha. is Ba, .beta. is Y and ? is Cu.

56. Process claimed in Claim 51, characterized in that said metal pipe is selected from a group comprising metals of Ag, Au, Pt, Pd, Rh, Ir, Ru, Os, Cu, Al, Fe, Ni, Cr, Ti, Mo, W and Ta and alloys including these metals as the base.

57. Process claimed in Claim 51, characterized in that said heat-treatment is carried out at a temperature ranging from 700 to 1,000 °C.

58. Process claimed in Claim 51, characterized in that the cross section of the metal pipe is reduced at a dimensional reduction ratio ranging from 16 % to 92 %.

59. Process claimed in Claim 58, characterized in that said plastic deformation is performed by wire-drawing.

60. Process claimed in Claim 59, characterized in that said wire-drawing is performed by means of dies, roller dies, or extruder.

61. Process claimed in Claim 58, characterized in that said plastic deformation is performed by forging.

62. Process claimed in Claim 61, characterized in that said forging is performed by means of swaging unit or rolls.

63. Process claimed in Claim 51, characterized in that said material powder of ceramic consisting of compound oxide having superconductivity is granulated previously.

64. Process claimed in Claim 51, characterized in that, after the heat-treatment complete, the metal pipe containing sintered ceramic material powder therein is cooled slowly at a rate of less than 50 °C/min.

65. A process for manufacturing a superconducting elongated article including steps comprising charging material powder of ceramic consisting of compound oxide having superconductivity into a metal pipe made of one of metals of Ag, Au, Pt, Pd, Rh, Ir, Ru, Os, Cu, Al, Fe, Ni, Cr, Ti, Mo, W and Ta or alloys including these metals as the base, subjecting the metal pipe to an intermediate annealing at such a temperature that the metal pipe is annealed, performing plastic deformation of the metal pipe filled with the ceramic metal powder therein to reduce the cross section of the metal pipe to such extent that the cross section of the metal pipe is reduced at a dimensional reduction ratio ranging from 16 % to 92 %, and then subjecting the deformed metal pipe to heat-treatment at a temperature ranging from 700 to 1,000 °C to sinter the ceramic material powder filled in the metal pipe.

66. Process claimed in claim 65, characterized in that said hot-plastic deformation is performed by wire-drawing.

67. Process claimed in Claim 65, characterized in that said wire-drawing is performed by means of dies, roller dies, or extruder.

68. Process claimed in Claim 65, characterized in that said plastic deformation is performed by forging.

69. Process claimed in Claim 68, characterized in that said forging is performed by means of swaging unit or rolls.

70. Process claimed in Claim 65, characterized in that said ceramic material powder contain compound oxide having the crystal structure of K2NiF4-type oxides.

71. Process claimed in Claim 70, characterized in that said ceramic material powder is [La, Ba]2CuO4 or [La, Sr]2CuO4.

72. Process claimed in Claim 65, characterized in that said ceramic material powder contain compound oxide having Perovskite-type crystal structure exhibiting superconductivity having the general formula:
( .alpha. 1-x, .beta. x ) ? y Oz wherein .alpha. stands for an element selected from IIa group elements of the Periodic Table, .beta. stands for an element selected from IIIa elements of the Periodic Table, ? stands for an element selected from a group comprising Ib, IIb, IIIb, IVa and VIIIa elements of the Periodic Table, x, y and z are numbers which satisfy following respective ranges:
0.1 ? x ? 0.9, 0.4 ? y ? 4.0, and 1 ? z ? 5.

73. Process claimed in Claim 72, characterized in that said .alpha. is Ba, .beta. is Y and ? is Cu.

74. Process claimed in Claim 72, characterized in that said material powder of ceramic consisting of compound oxide having superconductivity is granulated previously.

75. Process claimed in Claim 65, characterized in that, after the heat-treatment is completed, the metal pipe containing sintered ceramic material powder therein is cooled slowly at a rate of less than 50 °C/min.

76. A process for manufacturing a superconducting elongated article including steps comprising charging material powder of ceramic consisting of compound oxide having superconductivity into a metal pipe, performing plastic deformation of the metal pipe filled with the ceramic metal powder therein to reduce the cross section of the metal pipe to such extent that the cross section of the metal pipe is reduced at a dimensional reduction ratio ranging from 16 % to 92 %, making openings passing through the wall of the metal pipe, and then subjecting the perforated metal pipe to heat-treatment to sinter the ceramic material powder filled in the metal pipe.

77. Process claimed in Claim 76, characterized in that said ceramic material powder contain compound oxide having the crystal structure of K2NiF4-type oxides.

78. Process claimed in Claim 77, characterized in that said ceramic material powder is [La, Ba]2CuO4 or [La, Sr]2CuO4.

79. Process claimed in Claim 76, characterized in that said ceramic material powder contain compound oxide having Perovskite-type crystal structure exhibiting superconductivity having the general formula:
( .alpha. 1-x, .beta. x ) ? y Oz wherein .alpha. stands for an element selected from IIa group elements of the Periodic Table, .beta. stands for an element selected from IIIa elements of the Periodic Table, ? stands for an element selected from a group comprising Ib, IIb, IIIb, IVa and VIIIa elements of the Periodic Table, x, y and z are numbers which satisfy following respective ranges:
0.1 ? x ? 0.9, 0.4 ? y ? 4.0, and 1 ? z ? 5.

80. Process claimed in Claim 79, characterized in that said .alpha. is Ba, .beta. is Y and ? is Cu.

81. Process claimed in Claim 76, characterized in that said metal pipe is selected from a group comprising metals of Ag, Au, Pt, Pd, Rh, Ir, Ru, Os, Cu, Al, Fe, Ni, Cr, Ti, Mo, W and Ta and alloys including these metals as the base.

82. Process claimed in Claim 76, characterized in that said heat-treatment is carried out at a temperature ranging from 700 to 1,000 °C.

83. Process claimed in Claim 76, characterized in that said plastic deformation is performed by wire-drawing.

84. Process claimed in Claim 83, characterized in that said wire-drawing is performed by means of dies, roller dies, or extruder.

85. Process claimed in Claim 76, characterized in that said plastic deformation is performed by forging.

86. Process claimed in Claim 85, characterized in that said forging is performed by means of swaging unit or rolls.

87. Process claimed in Claim 76, characterized in that said material powder of ceramic consisting of compound oxide having superconductivity is granulated previously.

88. Process claimed in Claim 76, characterized in that, after the heat-treatment complete, the metal pipe containing sintered ceramic material powder therein is cooled slowly at a rate of less than 50 °C/min.

89. Process claimed in Claims 51 or 76 , characterized by including a further step of removing the metal pipe from a sintered body produced from the material ceramic powder, after the sintering complete.