DE10307643B4 - High-temperature superconducting body and method for its production - Google Patents

Abstract

High-temperature superconductive body containing the superconducting compound of the REBa ₂ Cu ₃ O _{7 type} and metallic additives in oxidic form prepared by a melt-texturing process, wherein RE is the chemical element Y or one of the chemical elements having the PSE atomic number 57 to 71 or a mixture of the above Is elements, characterized in that the body contains as additives one or more of the chemical elements of a group A formed with Ru, Ir and Rh and one or more of the chemical elements of a group B formed with Zn, Li, Ni and Pd, wherein the molar amount n of the addition of the group A per 1 mol of REBa ₂ Cu ₃ O ₇ with 0, 01 <n <0; 3 and the molar amount m of the addition of the group B per 1 mol of REBa ₂ Cu ₃ O ₇ with 0.001 <m <0.1 is selected, and that the melt-textured body consists of a superconducting matrix, in addition to one or more elements of the Group B ...

Description

The The invention relates to a high-temperature superconductive body and a method for its production. The body can be in a variety of geometric Molds executed be, for example, as an annular Component with square or rectangular cross-section, as a circular disk-shaped component, as cuboid Component or as a layer on a substrate. Such components can especially in energy, drive and transport technology be applied.

Massive high-temperature superconducting materials are usually prepared by peritectic melt crystallization by reversing the decomposition reaction α-superconductor phase (bulk material) ⇔ melt + β-solid phase used for YBa ₂ Cu ₃ O _7-δ (YBCO) as α-phase in air at 1020 ° C (M. Murakami et al., Journal of Engineering Materials and Technology 114 (1992) 189-195). Unreacted β phase Y ₂ BaCuO ₅ (211) remains in the case of YBCO as an inclusion in the microstructure. The crystallization underlying this process combined with a temperature gradient is commonly referred to as melt texturing.

The most important properties of the moldings thus obtained are determined by the critical current density, which is itself limited by the fact that the magnetic flux entering the type II superconductor starts to move under the influence of field and current (dissipation leading to the loss of superconductivity) can). Conventional solid materials are composite materials in which particles of a second phase, Y ₂ BaCuO are included. ₅ Magnetic flux is trapped at the inner interfaces ("pinning") Materials produced by the prior art contain up to 50% of this non-superconductive phase, which considerably narrows the current-carrying cross-section, which has a particularly pronounced effect on coated conductors and tapes. in which the superconductor thickness is only a few 10 to 100 nm.

Recently, it has been found that by chemical substitution, for example, Zn for Cu in Y123 superconductors ( DE 101 12 990 ) the critical current density can be significantly increased. In conventional processes, however, the non-superconducting phase Y ₂ BaCuO ₅ always arises in considerable proportions due to the process. Their presence enables a crucible-free dimensionally stable peritectic melting and, inversely, the crystallization of quasi-crystalline blocks. Therefore, there is an urgent need to find solutions for the replacement of the nonsuperconductive filling material without impairing the processability of the material in the melt crystallization process, which is a seal-free dimensionally stable process. Particularly effective Pinnungzentren arise in the form of long channels (nm diameter) when irradiated with high-energy neutrons or high-energy rays (R. Gonzalez-Arrabal, M. Eisterer, HW Weber, G. Fuchs, P. Verges, G. Krabbes, Very high Trapped fields in neutron irradiated and reinforced YBa ₂ Cu ₃ O _7-δ melt-textured superconductors, Applied Physics Letters, 81 2002 (5) 868-870; R. Weinstein, R.-P. Sawh, D. Parks, M. Murakami, T. Mochida, N. Chikumoto, G. Krabbes, W. bender, Very high values of J _c Obtained in NdBa ₂ Cu ₃ O _x by use of U / n process Physica C 383 (2002) 214-222).

Because of Of the only slowly decaying residual activity, these methods are economical ineffective.

A special form of solid superconductors are thick films of the REBa ₂ Cu ₃ O ₇ -based superconducting material which, for certain applications in information transmission or energy transfer, form an advantageous alternative to "powder in tube" BiSCCO materials applied to a substrate. for example, ceramic or a metal band.

Furthermore, it is known from DE 102 49 550 A1 a superconducting cable conductor with SEBCO-coated conductor elements, which comprises a support element, on which at least one layer of two or more superconducting conductor elements is wound, wherein the individual conductor elements of each layer are arranged side by side, and the superconducting conductor elements are formed from a band-shaped substrate, the coated with a superconducting material based on rare earth barium cuprate.

From the DE 196 23 050 A1 For example, a method for producing high temperature superconducting bulk materials is known. Thereafter, a species-specific platinum-containing compound SE _k Pt _l M _m Cu _n O _z is added to a starting powder SE _u M _v Cu _w O _z . This powder mixture is ground, pressed and thermally treated, including a crucible-free melt-texturing process, and made into solid blocks, moldings or ribbons which can be used as superconductors.

disadvantage previous solutions here are the slow growth rate at physical Coating and the poor coating quality in chemical processes. The crystallization over Fusion allows significantly higher rates and better qualities.

The invention has for its object to develop high-temperature superconducting body with very good, reproducible electrical and magnetic properties. Locked in in this task is the development of a corresponding manufacturing process.

These Task is with the features specified in the claims solved.

The invention is based on a high-temperature superconducting body containing or consisting of the REBa ₂ Cu ₃ O ₇ type superalloy compound and metallic additives, which is made by a melt texturing process, where RE is the chemical element Y or one of the chemical elements with the PSE -Ordnungszahl 57 to 71 or a mixture of said elements is.

According to the invention, the body contains as additives one or more of the chemical elements of a group A formed with Ru, Ir and Rh and one or more of the chemical elements of a group B formed with Zn, Li, Ni and Pd of the addition of the group A per 1 mol of REBa ₂ Cu ₃ O ₇ with 0.01 <n <0.3 and the molar amount m of the addition of the group B per 1 mol of REBa ₂ Cu ₃ O ₇ with 0, 001 <m < 0, 1 selected. According to a further feature of the invention, the melt-textured body consists of a superconducting matrix in which, in addition to one or more group B elements, there are also areas which contain one or more group A elements concentrated. These areas are present as elongated particles, as lamellar zones or as granular inclusions.

The elongated particles consist according to an advantageous embodiment of the invention of a Ru-containing phase of the composition Ru _r Pt _p Al _a Ba _b Cu _c Y _y O _x exist, where:
0.01 <r <0.2
0 <p <0.15
0 <a <0.15
0, 3 <b <0, 55
0, 01 <c <0, 5
0 <y <0, 25.

According to one appropriate embodiment of Invention, the superconducting body as a superconducting film be made with a thickness in the range of 0.1 .mu.m to 100 .mu.m.

The Ba may be wholly or partly by one or more elements of the Rare earth and / or the alkaline earth metals to be substituted.

RE may be substituted ₂ Cu ₃ O _{7-σ z} Ca _z Ba in part by Ca according RE _l _, wherein 0.01 <z <0.2 applies.

The process for producing hochtexturierter or enkristalliner high-temperature superconducting body by a melt crystallization process in which the superconducting phase is a compound of the type REBa ₂ Cu ₃ O ₇ , where RE is the chemical element Y or one of the chemical elements with the PSE atomic number 57 to 71 or is a mixture of said elements, characterized in that an additive is added to the starting mixture for the melt texturing process comprising one or more of the chemical elements of a group A formed by Ru, Ir and Rh and one or more of the chemical elements of Zn, Li, Ni and Pd formed group B. In this case, the molar amount n of the addition of the group A per 1 mol of REBa ₂ Cu ₃ O ₇ with 0.02 <n <0.3 and the molar amount m of the addition of group B per 1 mol of REBa ₂ Cu ₃ O ₇ with 0, 001 <m <0, 1 selected.

The molar amount n of a Ru additive per 1 mol of REBa ₂ Cu ₃ O ₇ is advantageously chosen to be 0.01 <n <0.3.

The molar amount m of a Zn additive per 1 mol of REBa ₂ Cu ₃ O ₇ is advantageously chosen to be 0.001 <m <0.1.

The molar amount k of a Li additive per 1 mol of REBa ₂ Cu ₃ O ₇ is advantageously chosen to be 0.001 <k <0.1.

The High-temperature superconducting inventive body have very good reproducible electrical and magnetic properties on.

The additive according to the invention greatly influences the process of melt crystallization by the chemical elements Ru, Ir and / or Rh of group A. Usually, the melt texturing is carried out with an excess of Y ₂ BaCuO ₅ , which prevents the flow apart of the partially molten molding. The surplus is then found as a foreign phase in the body again. The stabilizing function of the melt at a low content (corresponding stoichiometric amount of Y ₂ BaCuO ₅ ) take over the elements of group A.

Prefers the A-group content in the mixture should be <0.1 moles per mole of RE123, if the elimination of a second phase is not desired. This case is then installed, with favorable strong pinning forces caused by magnetic moments in the atomic range (nm scale), for the flux adhesion to be exploited.

But a higher A-group contents are advantageous when at the same time the formation of a phase Ru Pt _{r p} Al _a Ba _b Cu _c O _y Y _x is sought by the addition of A1 and Pt. This phase tends to have fine acicular precipitates in the superconducting Matrix, which, similar to columnar radiation defects, pinning flux lines multiply and tightly.

One particular advantage is that high current densities at 77 K can still be reached above 3 T.

below is the invention of embodiments explained in more detail.

example 1

• a) Herstellung einer Pulvermischung und Formgebung (Pressen zu einem Formkörper oder Verstreichen auf einer Unterlage),
• b) Durchführung eines Schmelzkristallisationsprozesses an dem geformten Körper,
• c) Oxidation des kristallisierten Formkörpers.

A superconductive body is produced in a process from the following essential process steps:

• a) preparation of a powder mixture and shaping (pressing into a molding or spreading on a substrate),
• b) performing a melt crystallization process on the molded body,
• c) oxidation of the crystallized molding.

In step a) is first a powder of the starting compound YBa ₂ Cu _2.98 Ni _0.02 O ₇ prepared from a mixture of Y ₂ O ₃ , BaCO ₃ , CuO and NiO in appropriate molar proportions by heating three times at 940 ° C with subsequent comminution and homogenization of the reaction product. The powder thus obtained is admixed with RuO ₂ powder in the following molar ratio: 1YBa ₂ Cu _2.98 Ni _0.02 O ₇ : 0.03RuO ₂

The obtained powder mixture becomes a cylindrical shaped body with a diameter of 20 mm pressed.

• 1. Aufheizen mit 400 K/h auf 1050°C
• 2. Schnelles Abkühlen auf 1020°C
• 3. Kristallisation durch Abkühlen mit 1 K/h auf 975°C

To prepare the melt texturing in process step b) is centrally ₇ placed on the end face of the shaped body, a seed of monocrystalline SmBa ₂ Cu ₃ O with its crystallographic c-axis parallel to the cylinder axis. In the subsequent melt-texturing, the shaped body is heat-treated in air as follows:

• 1. Heating at 400 K / h to 1050 ° C
• 2. Fast cooling to 1020 ° C
• 3. crystallization by cooling with 1 K / h to 975 ° C.

in the subsequent Process step c), the oxidation of the shaped body at 380 ° C over 150 Hours in an oxygen atmosphere.

Of the Moldings produced in this way contains a superconducting matrix free of inclusions of other Y-Ba-Cu oxides is. The matrix contains lamellar Ru-containing zones.

Example 2

The example relates to a solid body made of a superconducting material in which the superconducting matrix YBa ₂ Cu _2.99 Ni _0.01 O _{7 is formed} free of inclusions of the phase Y ₂ BaCuO ₅ or other Y-Ba-Cu-O phases. For the preparation, a starting powder of Y ₂ O ₃ , BaCO ₃ , CuO and Zn in the proportions corresponding to the formula is prepared in step a).

Subsequently, Ru powder is in proportion 1MolYBa ₂ Cu _2.99 Ni _0.01 O _7: 0,03MolRuO ₂ mixed and treated the mixture in an analogous manner as in the process steps b) and c) of Example 1.

Of the Moldings produced in this way contains a superconducting matrix free of inclusions of other Y-Ba-Cu oxides is. The matrix contains granular Ru-containing inclusions.

The critical current density at 77 K in a body thus produced is independent of an externally applied field over a wide range up to 3 T and greater than 5 × 10 ⁸ A / m ² .

Example 3

This example relates to the production of a superconductive bulk body in which the superconducting phase contains Li which replaces a part of the Cu in the compound YBa ₂ Cu ₃ O ₇ .

The preparation is carried out in an analogous manner as described in Example 1, with the difference that for the preparation of the starting powder Y ₂ O ₃ , BaCO ₃ , CuO and Li ₂ CO ₃ are mixed in proportions of the formula YBa ₂ Cu _2.99 Ni _0.01 O ₇ correspond.

Of the Moldings produced in this way contains a superconducting matrix free of inclusions of other Y-Ba-Cu oxides is. The matrix contains granular Ru-containing inclusions.

The body obtained is characterized in that at 77 K, the critical current density in the range up to 3 T is greater than 5 × 10 ⁸ A / m ² .

Example 4

The example relates to the case that the superconducting body is made in the form of a 50 μm thick film on a ZrO ₂ base. For this purpose, in step a) a powder having the composition YBa ₂ Cu _2.985 Zn _0.015 O ₇ is produced, the molar ratio of RuO ₂ in 1YBa ₂ (Cu, Zn) ₃ O ₇ : 0.03RuO ₂ is mixed.

The mixture is slurried in ethanol and ground in a ball mill for 20 minutes. After separation of the millbase, so much ethanol is removed until a spreadable consistency is achieved. The slip is applied to a Un with a spatula layer of ZrO _{2 applied} as a film about 50 microns thick.

To when dried in air, the coated base becomes a two zone oven to a temperature of 1015 ° C heated. After maintaining the temperature for 5 minutes, cool to 1045 ° C and with a time shift of 6 h a slow cooling process started at 0.5 K / h. Between the two Ofenheizzonen is doing set a temperature difference of 3K and the temperature Continuously lowered at 0.5 K / h to 975 ° C.

Finally, it will the oxidation at 380 ° C for 10 h carried out analogously as described in Example 1.

The obtained layer consists of a superconducting matrix, the isolated Ru-containing granular inclusions contains.

Example 5

The Preparation of a superconducting body with acicular precipitates is the following embodiment described.

First, a powder of the composition YBa ₂ Cu ₃ O _{7 is} prepared from the equivalent amounts of Y ₂ O ₃ + 2BaCuO ₃ + 3 CuO, as described in Example 1, after crushing RuO ₂ , Y ₂ O ₃ and Pt powder in the molar ratios 1YBa ₂ Cu ₃ O ₇ : 0.24Y ₂ O ₃ : 0.035RuO ₂ : 0.015Pt be mixed.

After homogenization, the powder mixture is pressed into a shaped body of dimensions 35 × 35 × 20 mm ² . To prepare the melt crystallization, the body is placed with a square side on a ceramic plate of Al ₂ O ₃ and on the opposite free side, a seed crystal of YBa ₂ Cu ₃ O _{7 is} placed in the middle. Subsequently, in process step b), the melt-texturing process is carried out as described in Example 1.

The result is a shaped body containing a superconducting matrix of YBa ₂ Cu ₃ O ₇ . In the matrix, in addition to granular inclusions of Y ₂ BaCuO _5, a high proportion of elongated particles in the form of fine needles consisting of Al _0.12 Ba _0.42 Cu _0.09 Pt _0.09 Ru _0.07 Y _0.21 O _1.22 exist.

The body is characterized by critical current densities over 5 × 10 ⁸ A / m ² in fields up to 3.5 T at 77 K.

Claims (9)

High-temperature superconductive body containing the superconducting compound of the REBa ₂ Cu ₃ O _{7 type} and metallic additives in oxidic form prepared by a melt-texturing process, wherein RE is the chemical element Y or one of the chemical elements having the PSE atomic number 57 to 71 or a mixture of the above Is elements, characterized in that the body contains as additives one or more of the chemical elements of a group A formed with Ru, Ir and Rh and one or more of the chemical elements of a group B formed with Zn, Li, Ni and Pd, wherein the molar amount n of the addition of the group A per 1 mol of REBa ₂ Cu ₃ O ₇ with 0, 01 <n <0; 3 and the molar amount m of the addition of the group B per 1 mol of REBa ₂ Cu ₃ O ₇ with 0.001 <m <0.1 is selected, and that the melt-textured body consists of a superconducting matrix, in addition to one or more elements of the Group B contain regions which contain one or more elements of group A concentrated, these regions being present as elongated particles, as lamellar zones or as granular inclusions. High-temperature superconductive body according to claim 1, characterized in that the elongated particles of a Ru-containing phase of the composition Ru _r Pt _p Al _a Ba _b Cu _c Y _y O _x exist, wherein 0, 01 <r <0, 2, 0 < p <0.15 0 <a <0.15 0, 3 <b <0, 55 0.01 <c <0.5 0 <y <0.25. High-temperature superconductive body according to claim 1, characterized characterized in that the body is a superconducting film having a thickness in the range of 0.1 μm to 100 μm. High-temperature superconductive body according to claim 1, characterized characterized in that the Ba is wholly or partly by one or more Substituted elements of rare earths and / or alkaline earth metals is. High-temperature superconductive body according to claim 1, characterized in that RE _1-z Ca _z Ba ₂ Ca is partially substituted in accordance with RE Cu ₃ O _7-σ, where 0, 01 <z <0, 2 applies. Process for the production of highly textured or monocrystalline high-temperature superconductive bodies by a melt crystallization process in which the superconducting phase is a compound of the type REBa ₂ Cu ₃ O ₇ , wherein RE is the chemi or a mixture of said elements is, according to one of claims 1 to 5, characterized in that the starting mixture for the melt-texturing process, an additive is added, the one or more the chemical elements of a group A formed with Ru, Ir and Rh and one or more of the chemical elements of a Z formed with Zn, Li, Ni and Pd group B, wherein the molar amount n of the addition of the group A per 1 mol of REBa ₂ Cu ₃ O ₇ with 0, 02 <n <0, 3 and the molar amount m of the addition of the group B per 1 mol of REBa ₂ Cu ₃ O ₇ with 0.001 <m <0.1 is selected. A method according to claim 6, characterized in that the molar amount n of a Ru additive per 1 mol of REBa ₂ Cu ₃ O _{7 is selected} with 0.01 <n <0.3. A method according to claim 6, characterized in that the molar amount m of a Zn additive per 1 mol of REBa ₂ Cu ₃ O ₇ with 0.001 <m <0.1 is selected. A method according to claim 6, characterized in that the molar amount k of a Li additive per 1 mol of REBa ₂ Cu ₃ O _{7 is} chosen to be 0.001 <k <0.1.