Method for improving current downloading capability of REBCO superconducting layer in magnetic field

Abstract

The invention discloses a method for improving the current downloading capacity of an REBCO superconducting layer in a magnetic field, and belongs to the field of superconductor materials, and the method comprises the steps: depositing an auxiliary layer on the surface of the REBCO superconducting layer, and carrying out the rotary grinding of the auxiliary layer on abrasive paper in cooperation with a cleaning solution, so as to introduce high-density dislocation into the REBCO superconducting layer, and cleaning the surface of the ground REBCO superconducting layer by using a cleaning solution, depositing a silver layer, and carrying out oxygen absorption treatment to obtain the final REBCO superconducting tape. According to the technical scheme, the on-site performance of the REBCO superconducting layer can be improved at low cost.

Description

Technical Field

[0001] This invention belongs to the field of superconducting materials technology, and particularly relates to a method for improving the current-carrying capacity of REBCO superconducting layers under magnetic fields. Background Technology

[0002] Second-generation high-temperature superconductor (REBa2Cu3O) 7-δ REBCO (where RE represents rare earth elements) tapes are widely used in power transmission, high-field magnets, microwave devices, and magnetic levitation due to their high critical transition temperature, excellent mechanical properties, and large current-carrying capacity. Under an applied magnetic field, the current-carrying capacity of the REBCO superconducting layer rapidly decreases with increasing magnetic field due to the vortex motion of magnetic flux within the REBCO. Artificially introduced flux pinning centers are needed to limit the vortex motion and improve the in-field current-carrying capacity to meet the application requirements in complex electromagnetic environments. Currently, methods for introducing artificial pinning centers include introducing a non-superconducting second phase, ion irradiation, and elemental substitution, among other defect engineering methods. However, current methods either require composition control during growth or the use of expensive irradiation equipment, lacking a cost-effective and simple post-processing method for introducing artificial pinning centers. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention proposes a method to improve the current-carrying capacity of REBCO superconducting layers in a magnetic field. This method introduces high-density dislocations as pinning centers through a mechanical approach, thereby improving the on-field performance of REBCO and solving the problem of the lack of inexpensive and efficient post-processing methods for introducing pinning centers in the prior art.

[0004] To achieve the above objectives, the present invention provides a method for improving the current-carrying capacity of a REBCO superconducting layer under a magnetic field, comprising: An auxiliary layer is deposited on the surface of the REBCO superconducting layer. The auxiliary layer is then rotary-ground on sandpaper with a cleaning solution to introduce dislocations onto the surface of the REBCO superconducting layer. After cleaning the surface of the REBCO superconducting layer with a cleaning solution, a silver layer is deposited, followed by oxygen absorption treatment to obtain the final REBCO superconducting tape.

[0005] Optionally, the auxiliary layer is made of CeO2 or Al2O3, and the deposition method is magnetron sputtering at a pressure of 100 Pa and a frequency of 300 Hz.

[0006] Optionally, the thickness of the auxiliary layer is 2nm-10nm, the mesh size of the sandpaper is 2000-5000 mesh, the applied force during the grinding process is 0.5N-5N, the grinding time is 1min-5min, and the grinding speed is 50rpm-200rpm.

[0007] Optionally, the cleaning solution is an anhydrous organic cleaning solution, including ethanol, ethylene glycol, or propylene glycol.

[0008] Optionally, the REBCO superconducting layer is disposed on a buffer layer, which is deposited on a metal substrate. The REBCO superconducting layer is doped or undoped REBa₂Cu₃O. 7-δ The thickness is over 500nm.

[0009] Optional, REBa2Cu3O 7-δ In this context, RE represents one or more of the 17 rare earth elements, including Sc and Y.

[0010] Optionally, when the REBCO superconducting layer is doped REBa2Cu3O 7-δ At that time, the doped material was Ba perovskite. M O3, Ba2RE N O6 or other non-superconducting phases, wherein, in Ba M In O3, M Selected from one or more of Zr, Hf, and Sn; in Ba2RE N In O6, RE is selected from one or more rare earth elements. N Select one or a mixture of Nb and Ta; other non-superconducting phases include RE2O3, SiO2 and BaCuO2.

[0011] Optionally, the buffer layer is a single-layer or multi-layer oxide film; When the buffer layer is a single layer, the oxide film composition is MgO; When the buffer layer is a multilayer oxide film, the oxide film composition is: a multilayer structure formed by Y2O3, YSZ and CeO2 in sequence; or a multilayer structure formed by Al2O3, Y2O3, MgO and LaMnO3 in sequence; or a multilayer structure formed by Al2O3, Y2O3, MgO and CeO2 in sequence.

[0012] Optionally, the metal substrate is a nickel-based or copper-based flexible metal substrate.

[0013] Optionally, the REBCO superconducting layer may or may not be ion-irradiated.

[0014] Compared with the prior art, the present invention has the following advantages and technical effects: This invention introduces high-density dislocations in a low-cost and simple manner, thereby improving the on-field properties of REBCO superconducting layers. >10^ 14 / m 2The high density of dislocations makes it possible to achieve the critical current density ( ) at a Kelvin temperature of 50K and a magnetic field strength of 5T. J c Greater than 2MA / cm 2 . Attached Figure Description

[0015] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of the device structure according to an embodiment of the present invention; Among them, 1-REBCO superconducting layer, 2-buffer layer, and 3-metal base band. Detailed Implementation

[0016] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0017] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0018] In this invention, the deposition of the REBCO film on the substrate uses conventional methods known to those skilled in the art, as exemplified below: Pulsed Laser Deposition (PLD) is a technique that typically utilizes equipment consisting of an excimer laser, an optical system, and a vacuum system. The optical system comprises a focusing lens and a laser window, while the vacuum system includes a vacuum chamber, a vacuum pump, a target material system, and a heater. The PLD system works by using a high-power pulsed laser beam provided by the excimer laser, which is focused through the optical system into the vacuum chamber and acts on the target surface. The target surface is subjected to high-temperature ablation, generating high-temperature, high-pressure plasma. This plasma expands and forms a plume. The plasma plume is directionally emitted to the substrate surface, ultimately depositing to form a thin film. The advantages of PLD include good repeatability, high deposition rate, ability to form high-quality thin films over large areas, and relatively low substrate temperature requirements. Notably, PLD causes almost no damage to the formed film and substrate, and the composition of the deposited film is essentially identical to that of the target material, exhibiting precise stoichiometry. These two advantages are particularly prominent in the preparation of superconducting thin films using REBCO materials with large molecular weights, making it a widely used preparation method. By setting parameters such as laser energy, laser frequency, focal length of the focusing lens in the optical path, distance between the target and the substrate (target distance), and substrate temperature, various REBCO materials can be prepared.

[0019] Metal-organic chemical vapor deposition (MOCVD) is a thin film deposition technique developed based on chemical vapor deposition (CVD) technology, and it is widely used for various thin film deposition processes. A typical MOCVD process for depositing REBCO films involves dissolving organic salts of RE, Ba, and Cu (such as tetramethylheptanediol) in an organic solvent (such as diethylene glycol dimethyl ether, xylene, etc.) as source materials. The solvent and organic salts are separated in an evaporating dish. Using oxygen as a carrier, the gaseous organic salts are pumped into a reaction chamber and uniformly deposited onto the substrate surface. The REBCO film is then obtained through in-situ heating. MOCVD can deposit REBCO films in a single step and offers advantages such as rapid growth, uniform film composition, easy control of elemental ratios, and no size limitations on the deposition area.

[0020] Reactive co-evaporation by deposition and reaction (RCE-DR) is a physical vapor deposition technique based on electron beam co-evaporation. Under vacuum, a high-energy electron beam directly heats the target material and transports it to the substrate, directly achieving thin film deposition. Electron beams are used to evaporate Gd, Ba, and Cu targets. The three metal vapors enter the reaction chamber in a specific ratio, and through temperature and oxygen partial pressure control, a precursor film is formed on the substrate. This precursor film is then heat-treated through low and high oxygen partial pressure regions to obtain the REBCO film. This process is a typical ex-situ method that can produce REBCO superconducting bands at a relatively high rate (120 m / h) and allows for precise control of the elemental ratios.

[0021] Metal-organic decomposition (MOD) is a method for preparing thin film materials. It primarily involves coating a solution of an organometallic compound onto a substrate, followed by thermal treatment to decompose and form an oxide film. A typical process for preparing REBCO films involves dissolving hydrolysis-insensitive carboxylates (such as isooctanoates), nitrates, or β-diketones (such as acetylacetonates) in a non-polar solvent (methanol, toluene, etc.) at a specific stoichiometric ratio to prepare a precursor solution. This precursor solution is then coated onto a superconducting substrate, followed by pyrolysis and sintering to form a composite oxide film. Because the pyrolysis process releases CO2 and H2O, resulting in significant volume changes, it requires strict control to prevent biaxial tensile forces within the oxide film, which could lead to cracking. Currently, MOD methods for REBCO film deposition can be categorized into two types based on the metal salt used: trifluoroacetic acid organometallic deposition (TFA-MOD) and fluorine-free organometallic deposition (FF-MOD).

[0022] like Figure 1 As shown, this embodiment provides a method to improve the current-carrying capacity of the REBCO superconducting layer 1 in a magnetic field, which can improve the current-carrying capacity of the REBCO tape in the field, including: An auxiliary layer is deposited on the surface of REBCO superconducting layer 1. A cleaning solution is added, and the auxiliary layer is rotated and polished on sandpaper to introduce high-density dislocations into REBCO superconducting layer 1. After polishing, the layer is cleaned, and a silver layer is deposited. Then, the REBCO superconducting layer 1 after silver deposition is subjected to oxygen absorption treatment to obtain the REBCO superconducting layer 1 with improved performance, which is the final REBCO superconducting tape.

[0023] Specifically, a 2 nm to 10 nm thick auxiliary layer (CeO2 / Al2O3) is first deposited on the surface of REBCO superconducting layer 1. Then, the auxiliary layer is faced with sandpaper (2000-5000 mesh) and a certain force (0.5N-5N) is applied. A cleaning solution (ethanol, ethylene glycol or propylene glycol) is added and the mixture is rotated and polished (1-5 min, 50-200 rmp) to introduce high-density dislocations into REBCO superconducting layer 1. After cleaning with a cleaning solution, a silver layer is deposited and then oxygen is absorbed to improve the on-field performance.

[0024] Under the influence of a magnetic field, magnetic field lines will enter the interior of REBCO superconducting layer 1 and form magnetic flux vortices. These vortices can move under the influence of the magnetic field, thus disrupting the lossless transmission capability. Dislocations can act as pinning centers for these magnetic flux vortices, effectively restricting their movement and thus improving the field performance.

[0025] Specifically, the REBCO superconducting layer 1 is a doped or undoped REBa2Cu3O deposited on a flexible metal substrate 3 with a buffer layer 2. 7-δ The thickness is over 500nm.

[0026] Specifically, in REBCO superconducting layer 1, "RE" refers to a mixture of elements containing one or more of the rare earth elements Sc and Y.

[0027] The rare earth elements mentioned above are scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). The "RE" in REBCO superconducting layer 1 can be any one or a mixture of the above rare earth elements. The material of the REBCO superconducting layer 1 with earth elements can be ScBCO, YBCO, LaBCO, CeBCO, PrBCO, NdBCO, PmBCO, SmBCO, EuBCO, GdBCO, TbBCO, DyBCO, HoBCO, ErBCO, TmBCO, YbBCO, or LuBCO. The material of the REBCO superconducting layer 1 with several mixed rare earth elements can be (Y... x Eu 1-x BCO, (Gd) x Eu 1-x BCO, (Y) x Eu y Gd 1-x-y BCO. (x ranges from 0 to 1, y ranges from 0 to 1, x + y ≤ 1) High-density dislocations can be introduced into REBCO superconducting layer 1 for any rare earth element or a mixture of several rare earth elements using the above scheme.

[0028] Specifically, if REBCO superconducting layer 1 is doped with REBa2Cu3O 7-δ The doped material in it is Ba M O3 or Ba2RE N O6 or other non-superconducting phases; in Ba M In O3, M Selected from one or more of Zr, Hf, and Sn; in Ba2RE N In O6, RE is selected from one or more of the rare earth elements Y, Gd, Eu, and Sm. N Select one or more of Nb and Ta; other non-superconducting phases include but are not limited to RE2O3, SiO2, and BaCuO2.

[0029] For Ba-doped materials M O3, M When one of the elements is selected from Zr, Hf, and Sn, the material is BaZrO3, BaHfO3, or BaSnO3. M When the elements selected are mixed from Zr, Hf, and Sn, the material is Ba(Zr) x Hf 1-x O3, Ba(Hf) x Sn 1-x O3, Ba(Zr) x Sn 1-x O3, Ba(Zr) x Hf y Sn 1-x-y O3, For Ba2RE doped material N In O6, RE is selected from one or more of the rare earth elements Y, Gd, Eu, and Sm. N Select one or more of Nb and Ta, and the above materials can be: Ba2YNbO6, Ba2EuNbO6, Ba2GdNbO6, Ba2YTaO6, Ba2EuTaO6, Ba2GdTaO6, Ba2(Y x Eu 1-x NbO6, Ba2(Y) x Gd 1-x NbO6, Ba2(Gd) x Eu 1-x NbO6, Ba2Y(Nb y Ta 1-y )O6,Ba2Eu(Nb y Ta1-y O6, Ba2Gd(Nb) y Ta 1-y O6, Ba2(Y) x Eu 1-x ) (Nb y Ta 1-y O6, Ba2(Y) x Gd 1-x ) (Nb y Ta 1-y )O6,Ba2(Gd x Eu 1-x ) (Nb y Ta 1-y )O6.

[0030] Different doped materials composed of one or more of the above-mentioned elements are well known in the art. The above example illustrates that the REBCO superconducting layer 1 composed of doped materials is also applicable to the method of introducing high-density dislocations described above in this invention. In addition to the above-mentioned materials, if other materials can form the REBCO superconducting layer 1 indicated in this invention, the method of introducing high-density dislocations described above in this invention is also applicable to the corresponding REBCO superconducting layer 1.

[0031] Specifically, REBCO superconducting layer 1 may or may not have been irradiated with ions.

[0032] In the un-ion-irradiated REBCO superconducting layer 1, there are no irradiation-damaged pinning centers. High-density dislocations can be directly introduced as pinning centers using this method. In the ion-irradiated REBCO superconducting layer 1, irradiation-damaged pinning centers have been formed. High-density dislocations can be introduced further using this method, thereby introducing more pinning centers to improve its field performance.

[0033] Specifically, the metal substrate 3 of the deposited REBCO superconducting layer 1 is a nickel-based or copper-based flexible metal substrate, and a single or multiple oxide film is coated on the metal substrate 3 as a buffer layer 2. The structure of the oxide film is one of CeO2 / YSZ / Y2O3, MgO, LaMnO3 / MgO / Y2O3 / Al2O3 or CeO2 / MgO / Y2O3 / Al2O3.

[0034] It is feasible that, when the buffer layer is a single layer, the oxide film composition is MgO; When the buffer layer is a multilayer oxide film, the oxide film composition is: a multilayer structure formed by Y2O3, YSZ and CeO2 in sequence; or a multilayer structure formed by Al2O3, Y2O3, MgO and LaMnO3 in sequence; or a multilayer structure formed by Al2O3, Y2O3, MgO and CeO2 in sequence.

[0035] The oxygen absorption process described is a common treatment method for REBCO phase transition from tetragonal to orthorhombic phase, and is not limited by specific conditions.

[0036] The above technical solutions are described in detail below: Example 1 A 2 nm thick auxiliary layer (CeO2) was first deposited on the surface of a BaHfO3(BHO)-doped (3.5 mol%) EuBCO superconducting film (the superconducting film preparation method is described in reference Wu Yue, Shi Jiangtao, Guo Chunjiang, et al., Ultra-fast dynamicdeposition of EuBa2Cu3O7-δ-BaHfO3 nanocomposite films: Self-assemblystructure modulation and flux pinning behaviors[J], Materials&Design, 2022,224: 111406). Then, the auxiliary layer was faced with 5000-mesh sandpaper and a certain force (0.5 N) was applied. A cleaning solution (ethanol) was added, and the film was rotary polished (5 min, 50 rpm) to introduce a high density of dislocations into the EuBCO superconducting layer, with a dislocation density of 2.1 × 10^6. 14 / m 2 Then, after cleaning with a cleaning solution, a silver layer is deposited. Following this, oxygen absorption treatment is performed at a Kelvin temperature of 50K, a magnetic field strength of 5T, and a critical current density. (J c The value is 2.5 MA / cm 2 Compared to the critical current density of 1.3 MA / cm² for the original sample, this represents a significant improvement. 2 Performance has nearly doubled.

[0037] Example 2 In GdBa2Cu3O 7-δ(For the preparation method of the GdBCO superconducting film, see reference Shi Jiangtao, Zhao Yue, Jiang Guangyu, et al., Deposition of REBCO with different rare earthelements on CeO2 buffered technical substrates by fluorine-free metal organic decomposition route[J], Journal of the European Ceramic Society, 2021, 41:5223-5229.) First, a 10 nm thick auxiliary layer (CeO2) is deposited on the surface. Then, the auxiliary layer is faced with sandpaper (2000 mesh) and a certain force (5 N) is applied. A cleaning solution (propylene glycol) is added and the film is rotated and polished (1 min at 200 rmp), thereby introducing a high density of dislocations in the GdBCO superconducting layer, with a dislocation density of 5 × 10^ 14 / m 2 Then, it is cleaned with a cleaning solution, after which a silver layer is deposited. It then undergoes oxygen absorption treatment, and is subjected to a critical current density of 50 Kelvin and 5 T magnetic field strength. J c The value is 3.2 MA / cm 2 .

[0038] Example 3 Y after ion irradiation x Pr 1-x Ba2Cu3O 7-δ (Y x Pr 1-xFor a BCO superconducting film (0 < x < 1) (for the preparation method of the superconducting film, see Fischer D. X., Prokopec R., Emhofer J., et al., The effect of fast neutron irradiation on the superconducting properties of REBCO coated conductors with and without artificial pinning centers[J], Superconductor Science and Technology, 2018, 31: 044006.), a 10-nm-thick auxiliary layer (Al2O3) is first deposited on its surface. Then, the auxiliary layer is faced towards sandpaper (5000 mesh) and a certain force (5 N) is applied. A cleaning solution (propylene glycol) is added and rotary grinding is carried out (3 min, 100 rmp), so as to introduce high-density dislocations into the Y x Pr 1-x BCO film. The dislocation density is 1.5×10^ 14 / m 2 . Then, it is cleaned with the cleaning solution. After cleaning, a silver layer is deposited. Then, after oxygen absorption treatment, at a Kelvin temperature of 50 K and a magnetic field magnetic induction intensity of 5 T, the critical current density ( J c ) is 1.8 MA / cm 2 .

[0039] Comparative Example 1 On the surface of the GdBCO superconducting film, no auxiliary layer is deposited. It is faced towards sandpaper (2000 mesh) and a certain force (5 N) is applied. A cleaning solution (propylene glycol) is added and rotary grinding is carried out (1 min, 200 rmp). Then, it is cleaned with the cleaning solution. After cleaning, a silver layer is deposited. High-density dislocations cannot be generated in the GdBCO superconducting layer. After oxygen absorption treatment, at a Kelvin temperature of 50 K and a magnetic field magnetic induction intensity of 5 T, the critical current density ( J c ) is the same as that of the original sample, only 1.1 MA / cm 2 .

[0040] Comparative Example 2 A 2 nm thick auxiliary layer (CeO2) was first deposited on the surface of a BHO-doped (3.5 mol%) EuBCO superconducting film. Then, the auxiliary layer was placed on 500-mesh sandpaper with a force of 20 N, and a cleaning solution (ethanol) was added for rotary grinding (10 min, 500 rpm). After cleaning with the cleaning solution, a silver layer was deposited. High-density dislocations could not be generated in the EuBCO superconducting layer. After oxygen absorption treatment, the film was tested at a Kelvin temperature of 50 K and a magnetic field strength of 5 T under the critical current density (…). J c The value was the same as the original sample, 1.3 MA / cm. 2 .

[0041] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for improving the current-carrying capacity of a REBCO superconducting layer under a magnetic field, characterized in that, include: An auxiliary layer is deposited on the surface of the REBCO superconducting layer. The auxiliary layer is then rotary-ground on sandpaper with a cleaning solution to introduce dislocations onto the surface of the REBCO superconducting layer. After cleaning the surface of the REBCO superconducting layer with a cleaning solution, a silver layer is deposited, followed by oxygen absorption treatment to obtain the final REBCO superconducting tape.

2. The method according to claim 1, characterized in that, The auxiliary layer is made of CeO2 or Al2O3, and the deposition method is magnetron sputtering with a gas pressure of 100 Pa and a frequency of 300 Hz.

3. The method according to claim 1, characterized in that, The thickness of the auxiliary layer is 2nm-10nm, the mesh size of the sandpaper is 2000-5000 mesh, the applied force during the grinding process is 0.5N-5N, the grinding time is 1min-5min, and the grinding speed is 50rpm-200rpm.

4. The method according to claim 1, characterized in that, The cleaning solution is an anhydrous organic cleaning solution, including ethanol, ethylene glycol or propylene glycol.

5. The method according to claim 1, characterized in that, The REBCO superconducting layer is disposed on a buffer layer, which is deposited on a metal substrate. The REBCO superconducting layer is doped or undoped REBa₂CuO. 7-δ The thickness is over 500nm.

6. The method according to claim 1, characterized in that, REBa2Cu3O 7-δ In this context, RE represents one or more of the 17 rare earth elements, including Sc and Y.

7. The method according to claim 1, characterized in that, When the REBCO superconducting layer is doped REBa2Cu3O 7-δ At that time, the doped material was Ba perovskite. M O3, Ba2RE N O6 or other non-superconducting phases, wherein, in Ba M In O3, M Selected from one or more of Zr, Hf, and Sn; in Ba2RE N In O6, RE is selected from one or more rare earth elements. N Select one or a mixture of Nb and Ta; other non-superconducting phases include RE2O3, SiO2 and BaCuO2.

8. The method according to claim 5, characterized in that, The buffer layer is a single-layer or multi-layer oxide film; When the buffer layer is a multilayer oxide film, the oxide film composition is: a multilayer structure formed by Y2O3, YSZ and CeO2 in sequence; or a multilayer structure formed by Al2O3, Y2O3, MgO and LaMnO3 in sequence; or a multilayer structure formed by Al2O3, Y2O3, MgO and CeO2 in sequence.

9. The method according to claim 5, characterized in that, The metal substrate is a nickel-based or copper-based flexible metal substrate.

10. The method according to claim 7, characterized in that, The REBCO superconducting layer may or may not have been irradiated with ions.

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