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
• • 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
• • 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
  • C04B35/4504—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 rare earth oxides
  • C04B35/4508—Type 1-2-3
• • 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

Definitions

• This invention concerns superconducting ceramic materials and their manufacture and is directed to improvements in the fabrication of high critical temperature superconducting materials to form components and wires.
• these ceramic materials are inherently brittle, and this raises acute problems for the support of a conductor under the conditions of mechanical stress encountered in many high field applications.
• these materials are chemically extremely active, in particular exhibiting extreme sensitivity to the presence of oxygen and moisture, and in view of their extreme chemical activity, the components are also susceptible to corrosion and environmental degradation.
• a starting material from which a ceramic superconductor is to be formed comprises a ceramic base and a replaceable ceramic microstructure constituent which gives the combination significant ductility to enable thermomechanical working to be performed to produce a desired shape or configuration of the combined material, and which constituent is replaceable by another constituent material which gives the desired superconducting properties to the combined material.
• a method of making a superconducting ceramic based material in which a constituent " of the ceramic microstructure which is required to produce the superconducting properties (the superconductivity constituent), is substituted or replaced during at least an initial stage of the manufacturing process by a constituent which provides the ceramic microstructure with significant ductility, so that the material can be thermomechanically processed in the solid state, and thereafter the substituted constituent is replaced by the superconductivity constituent.
• the ceramic microstructure is controlled during solid state thermo- mechanical processing so that the ceramic has a particular chemical composition which gives the material ductility and after the solid state thermomechanical processing has been employed to•produce the final desired shape of the component, the chemical composition of the material is adjusted to give the material the desired superconducting properties.
• superconductor and superconducting material as employed herein are intended to mean materials which are capable of superconducti ity.
• the ceramic microstructure with the substituted constituent has significant ductility (typically having a Vickers hardness value similar to or below that of steel) at least at elevated temperatures at which conventional thermomechanical processing procedures are carried out (typically about 700°C), although in some cases the material may have significant dutility even at room temperature.
• composition of the material is conveniently temporarily altered to improve ductility by addition of a halide, particularly a fluoride.
• the superconducting ceramic-based material is to be an oxide phase or oxy-halide phase ceramic
• the material may be prepared, either initially or at some intermediate stage, as a halide so as to possess improved ductility, and after thermomechanical working, may be oxidised to remove and replace some or all of the halide constituent to produce the superconducting oxide or oxy- halide phase.
• Oxidation to remove halide may be carried out, eg, by . heating the material in pure oxygen gas, controlling the partial pressure of oxygen if necessary to obtain the desired degree of oxidation.
• oxidation may be carried out electrochemically by depositing an oxygen electrolyte (such as Bi D •Y 2°3' Y 2°3* Zr °2 ° r C C0 - ZrO 2 ⁇ and a halide electrolyte (such as LaF_ for fluorides) in contact with the material and applying a suitable electric potential across the electrolytes.
• the halide electrolyte may not be essential in all cases, and i-t may be possible to achieve the desired result by applying a suitable potential to the oxygen electrolyte.
• the ductile material may be formed into a wire by conventional wire processing techniques, typically by wire drawing, extrusion or swaging.
• the material may also comprise a composite with suitable cladding and internal structure, as described in our copending International Application No. PCT/GB88/00381, and if desired only selected parts of the composite may be rendered ductile while other parts may remain brittle or in the form of a powder, during the fabrication processing.
• A- particularly beneficial feature of the method of ductile wire processing described is the formation of an elongated textured microstructure.
• a microstructure is known to be very beneficial for supporting a high critical current density in conventional commercial superconductors (e.g. ductile NbTi alloys).
• the wire may be subjected to further annealing prior to conversion " to the required superconducting phase..
• the material can be adjusted to the required composition for optimum superconducting properties by more than merely one step, and a plurality of conversion steps may be employed to achieve full superconductivity.
• a fully processed conductor may be electrochemically adjusted into its optimum composition and state of oxidation or valence state so as to maximise its superconducting properties, as described in our copending International Application No. PCT/GB88/00381.
• the orientation of the ceramic material structure has been found to be significantly improved to allow high critical current densities to be obtained by titrating oxygen out of the pure oxide superconducting ceramic and then allowing the oxygen to return to restore the equilibrium over a period of time.
• Titration may be achieved using a solid electrolyte fast ionic conductor in contact with the superconductor and electrochemically titrating oxygen from the latter into the electrolyte.
• the oxygen level in the superconducting ceramic may be restored by allowing stoichiometry to reach its equilibrium value by slow cooling or by reversing the electrochemical process.
• the material in addition or alternatively, may be further processed to maximise its superconducting properties by successive annealing treatments in a vacuum or low pressure gas, on the one hand, and in gas with a high partial pressure of oxygen on the other hand. In this way the composition may be changed in a series of discrete annealing cycles.
• the superconductor may be required to be in the form of a tape or component of a particular shape.
• the ductile ceramic may be hot-formed by -roiling or forging.
• the material may be clad and may have a composite structure as in the case of wire. After forming to achieve the desired shape and microstructure the composition and state of oxidation or valence state may be adjusted as described above in the case of wire.
• the invention also envisages an alternative- method of processing- whereby the ceramic is initially compacted and partially processed as a brittle powder (or distribution of different brittle and ductile powders). Suitable cladding and appropriate separating barriers may be incorporated. After partial processing the brittle powder that is eventually intended to be the superconducting material is converted electrochemically or otherwise into a ceramic phase with ductility, and thermomechanical processing of the material in the solid state is performed in a manner such as described above, whereafter the ductile phase is altered, eg into an oxide or oxy-halide phase, to provide the desired superconducting properties.
• Figure 1 is a cross section through a wire which is capable of functioning as a superconductor and which is constructed in accordance with the invention.
• a copper wire 24 is surrounded by copper oxide 26, within a tube of yttria bismuth oxide 52 forming an oxygen ion conductor which is itself surrounded by a layer 48 of yttria barium copper oxide superconductor. This in turn is surrounded by a lanthanum fluoride layer 50 forming a fluorine ion conductor.
• a layer of porous platinum 56 provides for the establishment of an electric potential through the junction, to enable electrochemical / titration of oxygen and fluorine to be effected.
• the material was then sintered in air for 24 hours at
• a material having the composition YBa Cu 0 was
• a constant load compression test was performed on a pellet of the prepared material in which the temperature was ramped to 820°C. No detectable deviation from a linear relationship between force and reduction in thickness was noted. The material was then subjected to a constant load at 820°C for 2 hours and no change in dimension was noted to have occured.
• the material was sintered for 24 hours in air at 900°C and subsequently annealed for 120 hours in air at 500°C and furnace cooled.
• a constant load compression test was performed on a pellet of the prepared material in which the temperature was ramped to 760°C at 16 ⁇ C per minute.
• the applied load was 0.24kN.
• Example 2 Using the same starting materials as in Example 1, it is possible to produce a slightly less oxygen-rich material having an expected composition of YBa_Cu ' 0_ CL SpotifyF_ by using J o.O+X 2 a different molar ratio of 0.5 s 2 s 2 : 1 and subjecting the starting materials to the same heat treatment as in Example 2.
• the hardness tests were made using a diamond indentor which is pressed nto the surface of the sample under a known load and the size of the indentation produced is a measure of the hardness.

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

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

Family

ID=10621199

Family Applications (1)

Country Status (8)

• 1987
  • 1987-07-23 GB GB878717506A patent/GB8717506D0/en active Pending
• 1988
  • 1988-07-22 FI FI891244A patent/FI891244A0/fi not_active IP Right Cessation
  • 1988-07-22 EP EP88906007A patent/EP0329723A1/en not_active Withdrawn
  • 1988-07-22 JP JP63506087A patent/JPH02501018A/ja active Pending
  • 1988-07-22 AU AU20811/88A patent/AU2081188A/en not_active Abandoned
  • 1988-07-22 WO PCT/GB1988/000599 patent/WO1989001239A1/en not_active Ceased
• 1989
  • 1989-03-02 KR KR1019890700503A patent/KR890702264A/ko not_active Withdrawn
  • 1989-03-21 DK DK138889A patent/DK138889A/da not_active Application Discontinuation

Non-Patent Citations (3)

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