WO2003054977A2 - Procede de realisation de couches epaisses supraconductrices texturees, et structures supraconductrices texturees de façon biaxiale ainsi obtenues - Google Patents

Procede de realisation de couches epaisses supraconductrices texturees, et structures supraconductrices texturees de façon biaxiale ainsi obtenues Download PDF

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Publication number
WO2003054977A2
WO2003054977A2 PCT/IB2002/005527 IB0205527W WO03054977A2 WO 2003054977 A2 WO2003054977 A2 WO 2003054977A2 IB 0205527 W IB0205527 W IB 0205527W WO 03054977 A2 WO03054977 A2 WO 03054977A2
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starting materials
superconducting
textured
superconducting material
starting
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PCT/IB2002/005527
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German (de)
English (en)
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WO2003054977A3 (fr
Inventor
Georg J. Schmitz
Sudhakar Reddy
Jacques G. Noudem
Michael Tarka
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Nexans Superconductors Gmbh
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Publication of WO2003054977A2 publication Critical patent/WO2003054977A2/fr
Publication of WO2003054977A3 publication Critical patent/WO2003054977A3/fr

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    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10—Inorganic compounds or compositions
    • C30B29/16—Oxides
    • C30B29/22—Complex oxides
    • C30B29/225—Complex oxides based on rare earth copper oxides, e.g. high T-superconductors
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
    • 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
    • H10N60/0296—Processes for depositing or forming copper oxide superconductor layers
    • H10N60/0548—Processes for depositing or forming copper oxide superconductor layers by deposition and subsequent treatment, e.g. oxidation of pre-deposited material

Definitions

  • the present invention relates to a method for producing textured superconducting thick layers, in particular biaxially textured thick layers on a carrier material and structures suitable for practical use from these thick layers by appropriate geometric arrangement of the thick layers on the carrier material and to biaxially textured thick layers and superconductor structures formed therefrom.
  • the crystals which form the superconducting phase must have an orientation (texturing) which is as uniform as possible.
  • the layers should have a sufficiently high absolute critical current, which requires a sufficient thickness of the layer.
  • the degree of texturing of a superconducting layer should therefore be biaxial, that is to say that the crystals should be aligned as uniformly as possible along the crystallographic a and b axes, since layers with only uniaxial texturing along the crystallographic c- Axis the critical current density is insufficient for practical applications.
  • the texture describes the average crystal orientation. If this is statistical, we also speak of an untextured material.
  • superconducting thick layers because of their dimensions, superconducting thick layers, as the present invention relates, can be located between thin layers with thicknesses of less than 1 ⁇ m and superconducting solid materials with dimensions in the centimeter range and more.
  • Texturing in solid materials takes place by means of nucleation, formation of a constitutional gradient, exposure to external magnetic fields or temperature gradients etc.
  • Biaxially textured superconducting thin films can be obtained with a degree of texturing sufficient for applications and a correspondingly high critical current density by means of thin film processes such as the Ion Beam Assisted Deposition (IBAD) or Rolling Assisted Biaxially Textured Substrates (RABiTS).
  • IBAD Ion Beam Assisted Deposition
  • RABiTS Rolling Assisted Biaxially Textured Substrates
  • single-crystal superconducting thin films were deposited on various single-crystal carrier materials.
  • the thin layers obtained in this way can then only subsequently be shaped into the required geometric structures, for example with regard to electronic applications.
  • Textured superconducting thick layers for example made of rare earth barium cuprates with the general composition SEBa 2 Cu 3 O 7-x , can be obtained using various processes known for the production of thick layers, such as screen printing, electrophoresis etc.
  • the texture of the superconductor layer is achieved on the basis of special properties of the carrier material. For example, base materials with a rolled texture or multi-phase base materials are used.
  • the present invention is therefore based on the object of providing a productive, scalable and inexpensive method for producing biaxially textured superconducting thick layers and structures therefrom.
  • the invention is based on the object of providing biaxially textured superconducting thick layers and superconducting structures thereof which are suitable for practical use.
  • a method for producing a textured superconducting thick layer wherein at least two starting materials in the form of the superconducting thick layer to be formed are arranged in contact with one another on a carrier material, the at least two starting materials having a composition which, when at least partially melted, of the starting materials at least partially forms a superconducting material during a subsequent heat treatment, and in at least two of the Starting materials with respect to at least one texture size forms a gradient, the arrangement is subjected to a heat treatment with at least partial melting of one of the starting materials and formation of a superconducting material from at least some of the starting materials, and then the arrangement with crystallization of the formed superconducting material and textured growth of the Crystals isothermally cooled in the direction of the gradient of the texture size.
  • the term “superconducting material” also includes a superconducting material, that is to say a material which can be converted into a superconducting material by an aftertreatment, as is generally known and customary for adjusting the oxygen content for superconducting materials.
  • the invention also includes biaxially textured superconducting thick layers, the texture of which is independent of the texture of the carrier material or which are applied to an untextured carrier material, and which in particular have a critical current density of 10,000 A / cm 2 at 77 K in the field of their own.
  • the invention comprises biaxially textured superconducting thick layers which are applied to a carrier material which is selected from polycrystalline silver and polycrystalline silver alloys.
  • the invention comprises biaxially textured superconducting thick layers in which the superconducting material has a concentration gradient at least with respect to a component of the material forming the superconducting layer.
  • the invention in particular comprises structures made of a biaxially textured superconducting thick layer, the structure having a geometric shape that is not a straight line.
  • the attached figures relate to preferred embodiments of the invention. It shows:
  • Figure 1a shows a structure according to the invention, in which the starting materials are arranged in a meandering shape
  • FIG. 1b shows an enlarged detail of a section of the structure according to FIG.
  • FIGS. 1a and 1b shows a section through the thickness of the structure including the support material according to FIGS. 1a and 1b;
  • Figure 2 shows an example of a band-shaped arrangement of the starting materials and schematically the biaxial texture of the obtained
  • FIG. 3 shows an example of a circular arrangement of the starting materials and schematically the biaxial texture of the thick layer obtained therefrom;
  • FIG. 4 is a diagram with the Jc values of those obtained in Example 1
  • Figure 5 shows an alternative arrangement of the starting materials
  • Figure 6 shows an arrangement for a preferred embodiment of the method according to the invention.
  • the invention makes use of the fact that by generating a gradient in the starting materials used for the production of the superconducting material, textured growth of the superconductor layer is effected parallel to the gradient.
  • the gradient is generated in this case by either selecting the starting materials differently, at least with respect to a quality, or by forming a corresponding gradient while the method according to the invention is being carried out.
  • Texture quantities that can form gradients can be the concentration of a component in the starting materials or different particle sizes of the starting materials.
  • This gradient with respect to the at least one quality parameter causes the materials to solidify or melt at different speeds in the direction of the gradient and thus to a directed crystallization and texturing of the superconducting material which forms, in the direction of the gradient during subsequent cooling.
  • compositions which have a stoichiometry and which form the desired superconducting material in the course of the heat treatment and the subsequent isothermal cooling can generally be used as the starting material.
  • at least two starting materials can be selected for the formation of a concentration gradient, which differ in at least one component of the composition.
  • the starting materials are preferably already arranged on a carrier material in the form of the desired macroscopic structure in such a way that they are in contact with one another.
  • the term “in contact with one another” does not necessarily mean that all starting materials are in direct contact with one another, but individual starting materials can also be connected to one another via further starting materials with which they are in contact Depending on requirements, they can be arranged side by side or one above the other.
  • This arrangement of carrier material with starting materials arranged thereon is subjected to a heat treatment in a first stage, whereby the assembly is heated to a temperature at which at least some of the starting materials melt.
  • the starting materials mix at least partially.
  • the reason for the at least partial mixing can be diffusion processes and / or unmelted starting materials can dissolve in already melted starting materials. Due to these diffusion and mixing processes, precursors for the superconducting material are formed.
  • the at least one component, in which the compositions of the starting materials differ migrates in the direction of the starting material which does not contain this component, the concentration of this component over the cross section of the layer with increasing distance from the starting material which this component originally originates from has contained decreases.
  • the superconducting material with the highest solidification temperature first crystallizes, with the crystallization in the direction of the concentration gradient and the resulting gradient of the peritectic solidification temperature of the superconducting materials formed progresses.
  • the crystallization or solidification of the superconducting material takes place along the concentration gradient in the direction of the material with the lowest solidification temperature.
  • the resulting gradient of the solidification temperature favors the directional growth of the crystals of superconducting material parallel to this gradient during the spatially isothermal slow cooling.
  • the correspondingly favored crystal orientation prevails in the further solidification process against unfavorably oriented crystals, so that ultimately only crystals with the desired preferred orientation remain.
  • Isothermal cooling means that the temperature is reduced uniformly over the entire arrangement, so that the arrangement is exposed to the same temperature over its entire extent at a given point in time.
  • isothermal cooling has the advantage that it can also be used easily on very small and / or complicatedly shaped structures.
  • crystallization by means of an external temperature gradient requires a minimum size of the structure to be formed, on the one hand due to the practicability and on the other hand so that an effective temperature gradient can be formed over the arrangement at all. If the extent over which the directional crystallization is to take place is too small, conventional devices for carrying out the crystallization by means of external temperature gradients cannot achieve sufficiently large temperature differences which bring about the desired directional crystallization.
  • the biaxial texturing of the thick layer takes place independently of the properties or the nature of the carrier material. This means that no carrier material is required to carry out the method according to the invention which already has a corresponding orientation by means of which the texturing of the thick layer which is formed is influenced.
  • the thick layers according to the invention therefore show no correlation between the texture of the carrier material and that of the thick layer. Untextured base materials and base materials which have no preferred orientation can thus also be used for the present invention.
  • untextured polycrystalline materials made of metal or ceramic or metal alloys can be used.
  • carrier materials to be used according to the invention are polycrystalline silver and silver alloys, for example with palladium.
  • the support material does not have to be subjected to a texturing treatment for the method according to the invention, as is the case, for example, with the known specially rolled and heat-treated polycrystalline silver support materials.
  • the polycrystalline material is given the desired crystal orientation only by the special pretreatment, which then brings about the desired orientation of the thick layer.
  • the selected carrier material should not melt at the temperatures used in the process and, moreover, must not have any undesirable side reactions with the materials for the thick layer.
  • Suitable materials are, for example, carrier materials which consist of a material or composite material whose melting point is above the minimum temperature required for converting the starting materials into the superconducting material.
  • the thickness of the carrier material usually depends on the intended application and on the thickness of the thick layer to be applied. It can be between 50 ⁇ m and 100 ⁇ m or more. This information can vary as required.
  • Support materials with a buffer layer can also be used, a thin layer of the desired support material being applied to a further support.
  • the carrier material can have any shape suitable for the desired application. Examples are plates and cylinders.
  • a thick layer in any pattern, such as a meander can be applied to a plate-shaped carrier or a coil can be printed as a thick layer on a cylinder as carrier material.
  • the starting materials can thus already be arranged on the carrier material in the form of the desired macroscopic structure to be formed, so that subsequent processing to form this structure is not necessary.
  • the starting materials can be arranged in any desired geometric shape on the carrier material.
  • the shape is not limited to straight lines and bands, but it can also be complicated shapes, for example curved structures in the form of spirals, circles or meanders, etc. Multi-filament training is also possible.
  • three-dimensional structures can also be obtained in which the thick layer is applied to a corresponding body. An example of this is a coil printed on a three-dimensional body, for example a cylinder.
  • Any coating method such as is customary for the production of thick layers, can be used to apply the starting materials to the carrier material. Examples include screen printing, docter blade, spin coating, brush application, sedimentation, airbrushing, electrolysis, etc.
  • the starting materials are available in a form suitable for these processes, for example as a powder, paste, suspension, etc.
  • the starting materials can be present in a medium suitable for application, such as a suspension or paste in a liquid.
  • the medium usually evaporates in the course of the heat treatment.
  • agents which initiate the crystallization can be used to support the crystallization of the superconducting material.
  • known nucleating agents such as magnesium oxide single crystals, for example in the form of whiskers, can be provided. These nucleating agents are preferably already aligned in the desired orientation of the crystallization growth.
  • Defects in the carrier material such as grooves, other unevenness and / or geometric surface structures, such as, for example, printed patterns, can also be provided to trigger the crystallization and can also be introduced in a controlled manner if necessary.
  • These agents which initiate the crystallization, are provided at the starting point of the crystallization front - usually the area with the highest solidification temperature - to increase the probability of nucleation.
  • a superconducting material of the same type as the superconducting material to be formed, which remains at least partially and preferably completely in the solid state at the temperatures of the heat treatment, can be used as the agent which initiates the crystallization.
  • the crystals of the superconductor material presented as a nucleating agent act as crystallization nuclei for the superconducting material that forms in the melt from the starting materials. For this it is necessary that the superconducting material presented as a nucleating agent does not completely melt at the temperatures of the heat treatment, but solid nuclei remain.
  • This material therefore preferably has a peritectic solidification temperature which is higher than that of the superconductor material formed from the starting materials.
  • the method according to the invention is particularly suitable for forming thick layers from oxidic superconducting materials.
  • Particularly preferred representatives are oxidic superconducting materials based on SE barium cuprates with SE selected from at least one rare earth metal including lanthanum and yttrium.
  • the superconducting material may optionally have at least one further element selected from the group consisting of Be, Mg, Ca, Sr, Zn, Cd, Sc, Zr, Hf , Pt, Pd, Os, Ir, Ru, Ag, Au, Hg, Tl, Pb, Bi, Ce, Ti, S and F.
  • oxidic superconducting materials with the composition mentioned above are the so-called “1-2-3 materials” (also called 1-2-3 compounds) with the general formula SEBa 2 Cu 3 O, where SE has the meaning given above and the oxygen content is set to a value suitable for superconductivity, in particular compounds of the general formula SEBa 2 Cu 3 O 7- ⁇ with x 0,5 0.5.
  • the compound may contain more than one rare earth metal and optionally at least one of the additional elements listed above.
  • suitable starting materials for the production of the preferred superconducting 1-2-3 materials are compounds of the general formula SE 2 BaCuO 5 , which are usually also referred to as 2-1-1 materials.
  • SE stands for at least one rare earth metal including the elements lanthanum and yttrium.
  • the 2-1-1 materials can additionally contain at least one further element from the same group as given above for the 1-2-3 materials.
  • the 2-1-1 materials are used in a manner known per se in combination with barium cuprates and, if appropriate, copper oxide.
  • This can be a mixture with a nominal stoichiometry Ba 2 Cu 3 O 5 .
  • the liquid phase composed of barium cuprate and optionally copper oxide can contain further additives if necessary. Suitable examples are one or more rare earth elements, Ag, Pt, Ce, Zn, Ba, Ca and F as well as compounds with these elements.
  • the compounds can be the oxides of these elements or their fluoride. Trade connections such as BaF 2 .
  • These additives can be contained in an amount of 1 to 10 percent by weight.
  • At least two 2-1-1 materials are selected as starting materials which differ in at least one of their rare earth components, so that when the method according to the invention is carried out, the desired gradient of the concentration for this at least one component of the starting materials and at the same time a gradient of the peritectic solidification temperature of the superconducting 1-2-3 material that forms during isothermal cooling.
  • a suitable example of such a combination of starting materials is 2-1-1 materials with the composition Y 2 BaCuO 5 (Y211) and Yb 2 BaCuO 5 (Yb211).
  • Tp peritectic solidification temperature
  • Tp (Y123)> Tp (Yb123) applies.
  • any other combinations that meet this condition can also be selected.
  • peritectic solidification temperatures or melting temperatures for 1-2-3 materials of the general formula SEBa 2 Cu 3 O 7-x are given in Table 1 below.
  • Table 1 only gives a guide to the selection of suitable combinations. Mixtures of various elements, the use of pressure or negative pressure, contents of substances which lower the melting point or the peritectic temperature, and in particular the oxygen partial pressure, can, however, cause a significant change in temperature and possibly also a change in the sequence listed in Table 1 ,
  • the starting materials for this preferred variant are the combination of Y 2 BaCuO 5 (Y211) 2 and Yb 2 BaCuO 5 (Yb211) 3, as well as NdBa 2 Cu 3 O 7-x (Nd123) 5 and a mixture of barium cuprate and CuO with the nominal stoichiometry Ba 2 Cu 3 O 5 4 as the liquid phase.
  • any other combination of 2-1-1 materials and, if necessary, 1-2-3 materials can also be selected which meet the conditions for the peritectic solidification temperatures.
  • the geometric arrangement of the starting materials (2, 3, 5) on the carrier material (1) can be assigned at least two characteristic length scales, which are shown in FIG. 1 a and in an enlargement in FIG. 1 b.
  • the larger length scales L1 and L2 in FIG. 1a correspond to the characteristic lengths of the structure of the layer to be formed (here a meander).
  • the smaller length scale I as shown in the enlargement in FIG. 1b, on the other hand, corresponds to the arrangement of the starting materials 2, 3, 5 in relation to one another to produce a texture in the superconductor material.
  • the starting materials 2, 3, 5 are arranged in lines next to one another on the carrier material 1, the adjacent lines forming the meandering structure shown in FIG. 1a.
  • the starting materials 2, 3, 5 arranged in a line on the carrier material 1 are completely or at least partially covered with the mixture of barium cuprate and copper oxide 5. Since the liquid phase of barium cuprate and copper oxide has a lower melting temperature than the 2-1-1 material 2, 3 and the 1-2-3 material 5, it melts first during the heat treatment. The melt formed infiltrates the starting materials 2, 3, 5 below, these at least partially dissolving in the melt. From this partial melt with the Ba 2 Cu 3 O 5 4 as a liquid phase with dissolved solid 2-1-1 material, the desired 1-2-3 material forms during slow cooling.
  • the rare earth elements migrate due to diffusion and melting processes, a first concentration gradient for Nd being formed from left to right in the example shown in FIG. 1b and a second concentration gradient for Yb being formed from right to left.
  • Tp (Nd 123)> Tp (Yb123) Due to Tp (Nd 123)> Tp (Yb123), a gradient of the solidification temperature results in the overall system as a result of the two concentration gradients mentioned above between the line formed from Nd123 5 and the Yb123 formed from Yb211 2. This gradient of the solidification temperature favors the directional growth of the superconducting crystals parallel to this gradient in the subsequent spatially isothermal slow cooling.
  • the final temperature of the heat treatment is preferably selected so that the 1 -2-3 material 5 is not yet melting, but the other starting materials 2, 3, 4 have melted in whole or in part or have dissolved in a melt.
  • Germination usually takes place statistically, but the crystals grow in the direction of the region with the lowest peritectic solidification temperature, for example from left to right in FIG. 1b.
  • the heat treatment in which at least some of the starting materials are melted, can be carried out in a commercially available oven.
  • the duration of the heat treatment depends on the type of raw materials. It must be long enough so that on the one hand the desired gradient is formed, on the other hand the heat treatment must be ended before the at least one component that is to form the gradient has been uniformly distributed in the starting materials.
  • the starting materials can be brought to the desired final temperature continuously or in stages. Different heating rates and / or one or more holding times can be provided for the gradual heating.
  • the holding times during the heat treatment also depend on the type and thickness of the starting materials.
  • Suitable heating rates are in a range from 200 ° C./hour to 500 ° C./hour, with a total heating time including holding times being in a range from 5 hours to 10 hours, depending on the heating rate.
  • the heat treatment can be carried out at a total pressure which corresponds to the normal air pressure.
  • the heat treatment can be carried out in an atmosphere of ambient air or, alternatively, it can be carried out in another gas atmosphere.
  • suitable gases or atmospheres are nitrogen with oxygen or argon with oxygen.
  • the melting points of the carrier materials and the superconducting materials can be influenced in a targeted manner by changing the oxygen partial pressure.
  • the melting point of the carrier material can be expediently increased by lowering the oxygen partial pressure and at the same time the ritectic temperatures of the superconducting materials are lowered (and vice versa).
  • Cooling rates can be selected for isothermal cooling as for the
  • cooling can occur at a rate of 10 ° C / hour or less.
  • Cooling is particularly preferably carried out at a rate in the range from 0.5 to 3 ° C./hour, in particular 0.5 to 1 ° C./hour.
  • the amount of liquid phase here Ba 2 Cu 3 O 5 , has to be chosen sufficiently for the formation of the desired superconductor material. It therefore depends on the type and quantity of the other starting materials.
  • FIG. 1 c shows a section through the thickness of the arrangement of carrier material 1 and starting materials 2, 3, 4 and 5 applied thereon.
  • the Ba 2 Cu 3 O 5 4 serving as the liquid phase does not have to completely cover the materials 3 and 5, but is sufficient if it only overlaps an edge region of the lines formed from these materials.
  • FIG. 2 shows an arrangement for the formation of a band-shaped structure on a carrier material 1 made of AgPd with lines of Y211 2, Yb211 3 and Nd123 5 and Ba 2 Cu 3 O 5 4 arranged next to one another as a liquid phase.
  • the left figure shows the arrangement before the heat treatment and subsequent isothermal cooling.
  • the right-hand illustration shows the finished strip, the 1-2-3 crystals 6 formed and their alignment being shown schematically.
  • the illustrations according to FIG. 3 show the production of a circular structure according to example 2 described below.
  • the middle illustration here is an enlarged section of the illustration on the right with the smaller length scale I, that is to say the arrangement of the starting materials to one another, and the illustration on the right shows the finished one Thick film, the biaxial orientation of the 1-2-3 crystals 6 formed is shown schematically.
  • FIG. 5 shows an example of an arrangement of the starting materials one above the other.
  • a line of 1-2-3 material 5 can first be applied to the carrier material 1, which line overlaps with a line of a first starting material 211 2, which is arranged next to it becomes.
  • a line of a second 2-1-1 starting material 3 can then be applied to the first 211 starting material 2 on the side opposite the 1-2-3 starting material 5.
  • the peritectic solidification temperature of the materials again applies to Tp (1-2-3 starting material)> Tp (formed 1 -2-3 material from the first 2-1-1 starting material)> Tp (formed 1 -2-3 material from second source material).
  • this vector points in a plane from the side of the starting materials with the highest peritectic solidification temperature to the side with the lowest peritectic solidification temperature.
  • the vector points from the bottom left (highest peritectic solidification temperature) to the top right (lowest peritectic solidification temperature).
  • the superconducting thick layer is produced using crystals superconducting material which form and align in situ when the method is carried out.
  • This embodiment is based on the knowledge according to the invention that in the production of superconducting materials by means of melting technology, an alignment of the superconducting crystals in the direction of a dimension of the geometric arrangement chosen for the superconducting material can be effected if this dimension has an extremely small dimension, a few 100 ⁇ m does not exceed.
  • This geometric arrangement can have any shape as long as the dimensions bring about the desired alignment. It can be in the form of a ribbon or strip, a spiral, rhombus or combinations thereof.
  • a suitable stoichiometry for example Ba Cu 3 O 5 as described above
  • narrow strips 8 of a further starting material are arranged as a geometric arrangement at an angle to the arrangement 7 obtained in stage 1, these broad sides 8 of which are in contact with an edge of the arrangement obtained in stage 1, starting from there the directed crystallization of the superconducting material to be formed is to be initiated.
  • the nucleation along a long side is usually initiated for the formation of a thick layer of superconducting material, as shown in FIG.
  • a starting material for a superconducting material is selected for the narrow strips 8, the peritectic solidification temperature of which is higher than that of the superconducting material or the superconducting materials for the actual thick film according to the form 7.
  • the dimensions of the narrow strip 8 are chosen such that the 1-2-3 crystals that form are forced along the width of the strip 8.
  • the width of the strip should not exceed 8 200 ⁇ m, since the degree of orientation decreases with increasing width.
  • the length can also be selected to be longer, for example in the centimeter range, but also smaller, for example in the micrometer range.
  • the number of strips 8 can be selected as required and is not subject to any fundamental restriction.
  • the distance between the individual strips 8 is expediently chosen such that the materials do not influence one another when the method according to the invention is carried out, and in particular do not run into one another when melting.
  • the orientation of the crystals forming in the arrangement 7 can be influenced.
  • the crystals show a ⁇ 110> orientation with a stripe arrangement at an angle of 45 °, as in Figure 6a shown, and when hitting at a 90 ° angle a ⁇ 100> orientation as shown in Figure 6b.
  • an arrangement of the strips 8 at a 45 ° angle and thus a ⁇ 110> orientation of the crystals is particularly preferred with regard to the current densities to be achieved.
  • the grain boundaries of superconducting crystals that meet with ⁇ 110> orientation show less contamination (segregation) at the grain boundaries than crystals that meet with other orientations, such as ⁇ 100> orientation. This enables particularly high current densities to be achieved for superconducting materials with ⁇ 110> -oriented crystals.
  • the method according to the invention for producing a superconducting thick layer by means of crystals produced and aligned in situ is carried out at a temperature at which the starting material selected for the strip 8 also melts. At the same time, a gradient is formed along the contact area of the strip 8 with the geometric shape 7 for the thick layer
  • the crystallization of the 1-2-3 materials first begins at any point on the strip 8, which is indicated by rectangles 9 in FIGS. 6a and b.
  • the crystals align with their ⁇ 100> or ⁇ 010> edges parallel to the edges of the strip 8 and the crystallization proceeds along the concentration gradient in the direction of the shape 7 and then into the shape 7.
  • the 1-2-3 crystals formed in the strip 8 grow into the mold 7, so to speak, and cause a directed crystallization of the starting material, which has been arranged according to the mold 7, in this warpage direction ,
  • powdery starting materials are selected for the process according to the invention, according to a further aspect according to the invention a gradient can be generated based on different particle sizes of the individual starting materials.
  • the different starting materials can also have the same chemical composition.
  • the starting materials can be arranged on the smaller quantity scale shown in FIG. 1 b in such a way that a gradient of the particle size which promotes the textured growth of the superconducting thick layers is produced for at least one starting material.
  • the layer material obtained after the isothermal cooling generally does not yet have superconductivity as such.
  • the thick layer with the superconducting material is subjected to a heat treatment known per se for adjusting the oxygen content of the superconducting material. This production of superconductivity in a superconducting material is known per se.
  • the textured superconducting thick layer obtained can be heated to 500 ° C. for 50 to 100 hours in an atmosphere with 1 bar oxygen partial pressure in order to optimize the oxygen content of the superconducting material in the thick layer.
  • the heating and cooling rates of the oxygen treatment can be about 100 ° C / hour.
  • the thickness of the thick layers according to the invention is usually in a range from greater than 5 ⁇ m, in particular from 10 ⁇ m and more, and less than 1 mm, preferably from 20 ⁇ m and more and less than 1 mm and in particular between 20 ⁇ m and more and 200 ⁇ m.
  • the thick layers obtained according to the invention show values for each of 10 A / cm 2 at 77 K, 0 T using a 2 ⁇ V / cm criterion, the Jc values for the thick layer according to Example 1 being shown in FIG. 4 as a diagram.
  • the superconducting thick layers obtained according to the invention show a high critical current density and absolute critical current suitable for practical applications.
  • the superconducting thick layers or superconducting structures according to the invention can therefore be used for a large number of energy technology applications, such as high-current applications and in the high-frequency range.
  • a meandering structure made of textured superconducting material according to the invention can be used, for example, as a resistive current limiter.
  • thick layers or structures according to the invention can be used, for example, as antennas or filters.
  • Another area of application for the thick layers according to the invention is the use as a nucleating agent for the production of solid materials.
  • Carrier material Band piece made of AgPd12.5 (palladium in weight percent) with a thickness of approximately 100 ⁇ m, a width of approximately 2 cm and a length of approximately 5 cm.
  • the average diameter of the powder particles of all powders ranged from 1 to 50 ⁇ m.
  • the lines arranged next to one another in this way were then covered with a layer of liquid phase with a total of about 400 mg of Ba 2 Cu 3 O 5 5.
  • the support material coated in this way was placed in air in a commercially available chamber furnace on an Al 2 O 3 block and subjected to the following heat treatment:
  • the mixture of silver, barium cuprate and copper oxide - the liquid phase - melted and formed a doped barium cuprate melt that infiltrated the underlying materials arranged next to one another.
  • the starting materials (2), (3) and (5) were at least partially dissolved from this liquid phase.
  • a concentration gradient of neodymium formed, which, starting from the starting material (5), pointed in the direction of the starting material (3).
  • a gradient of the concentration of ytterbium also formed, which, starting from the starting material (3), pointed in the direction of the starting material (2).
  • the oxygen content of the samples was optimized in such a way that x in YBa 2 Cu 3 O 7-x is minimally less than 0.5 in any case.
  • the heating and cooling rates of the oxygen treatment were about 100 ° C / h.
  • the thicknesses of the thick layers obtained were typically in the range between 10 and 15 ⁇ m.
  • the second exemplary embodiment was carried out analogously to the first exemplary embodiment, but the heat treatment and the isothermal cooling were carried out under the following conditions:

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Abstract

La présente invention concerne un procédé de réalisation de couches épaisses supraconductrices texturées à partir notamment d'un matériau supraconducteur oxydique tel que des cuprates de baryum SE. Selon l'invention: au moins deux matériaux de départ sont mis en contact sur un matériau support pour constituer la couche épaisse supraconductrice à former, les deux matériaux de départ ou plus ayant des compositions qui fondent au moins partiellement au cours d'un traitement thermique ultérieur et forment au moins partiellement un matériau supraconducteur, et les deux matériaux de départ ou plus formant un gradient par rapport à au moins une grandeur de constitution telle que la concentration d'une composante; le dispositif est soumis à un traitement thermique accompagné de la fusion au moins partielle des matériaux de départ et de la formation d'un matériau supraconducteur à partir d'au moins une partie des matériaux de départ; le dispositif subit un refroidissement isotherme accompagné de la cristallisation du matériau supraconducteur et de la croissance texturée des cristaux parallèlement à la direction du gradient de la grandeur de constitution. L'invention a également pour objet des couches épaisses supraconductrices texturées de façon biaxiale et des structures qui peuvent être produites selon le procédé de l'invention.
PCT/IB2002/005527 2001-12-20 2002-12-19 Procede de realisation de couches epaisses supraconductrices texturees, et structures supraconductrices texturees de façon biaxiale ainsi obtenues WO2003054977A2 (fr)

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DE10163125A DE10163125A1 (de) 2001-12-20 2001-12-20 Verfahren zum Herstellen texturierter supraleitender Dickschichten sowie damit erhältliche biaxiale texturierte Supraleiterstrukturen
DE10163125.1 2001-12-20

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US5124310A (en) * 1990-08-20 1992-06-23 Energy Conversion Devices, Inc. Laser ablation method for depositing fluorinated y-ba-cu-o superconducting film having basal plane alignment of the unit cells deposited on non-lattice-matched substrates
JP2920001B2 (ja) * 1991-07-15 1999-07-19 財団法人国際超電導産業技術研究センター 希土類系酸化物超電導体の製造方法

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KUGELER O ET AL: "Isothermal texturing of (RE)BCO ceramics using constitutional gradients" PROCEEDINGS OF THE INTERNATIONAL WORKSHOP, CRITICAL CURRENTS IN SUPERCONDUCTORS FOR PRACTICAL APPLICATIONS, SPA '97, XI'AN, CHINA, 6-8 MARCH 1997, Seiten 185-188, XP009018709 1998, Singapore, World Scientific, Singapore ISBN: 981-02-3313-2 *
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