Classifications

• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
  • C04B35/45—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on copper oxide or solid solutions thereof with other oxides
  • C04B35/4521—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on copper oxide or solid solutions thereof with other oxides containing bismuth oxide
  • C04B35/4525—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on copper oxide or solid solutions thereof with other oxides containing bismuth oxide also containing lead oxide
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
  • C04B35/45—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on copper oxide or solid solutions thereof with other oxides
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N60/00—Superconducting devices
  • H10N60/01—Manufacture or treatment
  • H10N60/0268—Manufacture or treatment of devices comprising copper oxide
  • H10N60/0801—Manufacture or treatment of filaments or composite wires

Definitions

• the present invention relates to the production of superconducting articles, such as tapes and wires.
• the invention particularly relates to the production of high performance superconducting articles based on BSCCO powder materials.
• the invention also relates to superconducting articles produced by this method, modified BSCCO precursors for producing a superconducting article and superconducting articles produced from said modified BSCCO precursors.
• the present invention relates to superconducting articles produced from a particular group of BSCCO precursor powder materials suitable for the production of superconducting articles with improved performance, and to the superconducting article with improved performance.
• a superconducting article such as a wire or a tape, is based on a superconducting material, which is defined as a material that has essentially zero resistance to the flow of electrical current at temperatures below a critical temperature.
• the superconducting material is normally based on copper oxide composite material which may be single phased or raultiphased.
• the current-carrying capacity of a superconducting oxide composite depends significantly upon the degree of alignment and the connection of the superconducting oxide grains. This degree of alignment is referred to as the degree of texture. While connection is to referred to degree of grain connectivity. A high degree of texture and a high degree of grain connectivity results m a high current- carrying capacity of the superconducting oxide composite.
• Superconducting articles may be smglefllamentary, but are most often multifllamentary articles, particularly when they are designated for use m AC applications and m applications where mechanical strength is needed.
• a filament comprises a textured superconducting oxide composite material extending along the length of the article and a constraining member substantially surrounding the filament.
• a multifllamentary superconducting article comprises a bundle of constrained filaments and a constraining member substantially surrounding the bundle of filaments.
• a superconducting article is normally produced by I) filling a precursor powder composite metal oxide material into a metal container, such as a tube (normally denoted at the "powder-m-tube method'*)/ or layering the precursor material with one or more grooved or billet sheet so that the precursor material is or is about to be surrounded by a constraining member such as a metal layer, II) deforming the article e.g. by stretching, pressing or rolling to obtain the desired form of the article, and III) subjecting the article to a sintering process by heating it up to a temperature m the range of from 600 °C to 875 °C .
• the individually constrained filaments may be bundled and constrained m a outer constraining member before or after the heat treatment, and the one or more deformations and/or heat treatments may be performed.
• the density and degree of texture of the oxide composites are developed by the one or more steps of deformation and the one or more sintering processes.
• the precursor powder composite metal oxide material is normally prepared by mixing a number of individual metal compounds, e.g. in the form of its nitrates or in the form of B1.O3, CaCO,, SrC0 3 , PbO and CuO powder, and calcinating the mixture (See e.g. the examples of WO 96/08045) .
• WO 97/1772 e.g. relates to a particular two-step heat treatment of the deformed article.
• WO 96/39366 relates to a method of producing a superconducting article by using a one step deformation and sintering process (IDS process).
• the superconducting phase is constituted by the(B ⁇ ,Pb) Sr Ca .
• Cu-0 referred to as the
• (B ⁇ ,Pb)-2223 phase This phase should mainly be produced during the sintering of the superconducting article, since it also is important that the (B ⁇ ,Pb)-2223 grains are aligned along the article. If the (B ⁇ ,Pb)-2223 phase are produced prior to the texturing, the (B ⁇ ,Pb)-2223 grains will not be well-aligned.
• the object of the present invention is to provide a method of producing superconducting articles, by use of which method it is possible to obtain superconducting articles exhibiting improved current densities. Furthermore, it is an object to provide a method of producing superconducting articles, by use of which method it is possible to obtain superconducting articles exhibiting equally high current densities m repeated productions.
• Another object of the present invention is to provide a method of producing superconducting articles to obtain superconducting articles having improved properties with respect to low resistance to the flow of electrical current at operable temperatures.
• the method of producing a superconducting article comprises the steps of:
• the contact surface between adjacent grains must be as clean (no impurities left) and well crystallised as possible.
• BSCCO 2223 phase and m most situations the BSCCO 2223 phase is relatively larger than m the known superconducting articles.
• Another object of the invention is to provide a method of producing superconducting articles by improved transformation of BSCCO 2212 into BSCCO 2223, preferably at a processing temperature lower than the processing temperature normally used for converting BSCCO 2212 into BSCCO 2223.
• the superconducting articles produced according to the method according to the invention exhibit improved gram connectivity.
• the transformation of the BSCCO precursor into BSCCO 2223 by using the method according to the present invention can be conducted at a processing temperature lower than the processing temperature normally used for converting BSCCO precursors into BSCCO 2223. Probably the processing speed will be faster at the same temperature.
• the alkali-halide may be selected from a group consisting of LiF, LiCl, NaF, NaCl, KF, KC1, RbF, RbCl, CsF, CsCl, MgF_, MgCl_, CaF context, CaCl., SrF_, SrCl_, BaF ⁇ , and BaCl .
• the alkali-halide used is CaF_ .
• the amount of added alkali-halide should be from 0.1-5 % (w/w), preferably in the range of 0.1-4.0 % (w/w), more preferably 0.2-3.0 % (w/w) and even more preferably 0.4- 2.0 t (w/w) .
• the initial precursor powder may be any BSCCO material, but preferably the material comprises a major BSCCO 2212 phase, preferably more than 60 % (w/w) .
• This BSCCO material may have various nominal compositions, but a preferred nominal composition may be
• the superconducting article according to the invention may have any geometry, e.g. a superconducting wire or a superconducting tape.
• the article may be singlefilamentary as well as multifilamenatary.
• Singlefilamentary articles according to the invention may have an average transverse thickness for the numbers mentioned less than about 500 ⁇ m, and preferably an average variation in thickness along its length of less than about 20%.
• Multifilamentary articles according to the invention may comprise from 2-1000 filaments, preferably from 7-200, wherein each of said filaments has an average transverse thickness less than 200 ⁇ m, and preferably an average variation m thickness along its length of less than about 201.
• the constraining member or constraining members are preferably of a noble metal selected among Ag, Au, Pd, and Pt, or alloys based on said elements.
• the constraining member or constraining members are of Ag or of an Ag-alloy.
• the deformation and texturing of the green singlefllamentary may by carried out m any conventional way, however m a preferred embodiment according to the invention it is performed, e.g. by a rolling process.
• Sintering of the deformed single- or multifllamentary article may be performed by one or more heat treatments at a temperature the range of 400-950 °C, preferably at a temperature m the range of 600-875 °C and more preferably at a temperature m the range of 750-840 °C.
• the oxygen pressure during the process may be m the range of 0.01-0.25 at, preferably 0.07-0.21 at.
• Figure 1 shows XRD patterns recorded on powdered pellets after various heat treatments .
• Figure 2 shows HTD traces recorded during 72 h at reaction temperature.
• Figure 3 shows Ic values measured on reference tapes.
• Figure 4 shows Ic values measured on tapes containing KC1.
• Figure 5 shows Ic values measured on tapes containing CaF_.
• the we ⁇ ght-5; of CaF and the sintering temperature are indicated on the respective patterns.
• the precursor powders consist mostly of the B ⁇ ,Pb(2212) and Ca_Pb0 4 phases as well as trace amounts of various alkaline earth cuprates.
• Fig. 1 shows that after 150 h of sintering at 836 °C the
• CaF_-free pellet still contained a significant amount of unconverted B ⁇ ,Pb(2212), whereas the sample initially containing 1.0 % (w/w) of CaF was almost completely converted to Bi,Pb(2223) under the same conditions.
• the optimum sintering temperature for the CaF-free sample was found to be around 851 °C, whereas the samples containing various amounts of CaF showed an enhanced conversion of Bi,Pb(2212) into Bi,Pb(2223) at temperatures from 825-840 °C . Highest conversion level was achieved for the sample initially containing 1.0 % (w/w) of CaF : .
• Pellets produced in example 1 were subjected to differential dilatometric (HTD) investigations in a SETARAM instrument under air flow. 30 ⁇ m Au foils were placed between the sample and the pressing Al : 0 3 rods in order to avoid spurious reactions. The results are shown in fig. 2.
• the heat treatment schedule were as follows:

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Ceramic Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Structural Engineering (AREA)
• Organic Chemistry (AREA)
• Inorganic Compounds Of Heavy Metals (AREA)
• Superconductors And Manufacturing Methods Therefor (AREA)

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Cited By (2)

Citations (3)

• 2000
  • 2000-09-14 AU AU72700/00A patent/AU7270000A/en not_active Abandoned
  • 2000-09-14 KR KR1020027003444A patent/KR20020063557A/ko not_active Application Discontinuation
  • 2000-09-14 EP EP00960365A patent/EP1218948A1/en not_active Withdrawn
  • 2000-09-14 WO PCT/DK2000/000509 patent/WO2001020690A1/en not_active Application Discontinuation
  • 2000-09-14 JP JP2001524166A patent/JP2003509826A/ja active Pending

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