A method for improving the current carrying capability of a REBCO superconducting layer under magnetic field

Abstract

The application discloses a method for improving current-carrying capacity of REBCO superconducting layer in a magnetic field, and belongs to the field of superconductor materials, and comprises the following steps: depositing an auxiliary layer on the surface of the REBCO superconducting layer; rotating and grinding the auxiliary layer on sandpaper with a cleaning liquid, so that high-density dislocations are introduced into the REBCO superconducting layer; depositing a silver layer on the surface of the REBCO superconducting layer after cleaning; and performing oxygen absorption treatment, so as to obtain a final REBCO superconducting tape. Through the technical scheme, the field performance of the REBCO superconducting layer can be improved at low cost.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of superconducting materials, and particularly relates to a method for improving the current-carrying capacity of a REBCO superconducting layer in a magnetic field. BACKGROUND

[0002] Second-generation high-temperature superconducting (REBa2Cu3O 7-δ , REBCO, RE is a rare earth element) tapes are widely used in power transmission, high-field magnets, microwave devices, magnetic levitation and other fields 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 the increase of the magnetic field due to the motion of magnetic flux vortices in the REBCO. Artificial pinning centers need to be introduced to limit the motion of magnetic flux vortices and improve the field current-carrying capacity in order to meet the application requirements in complex electromagnetic environments. At present, there are many defect engineering methods for introducing artificial pinning centers, such as introducing a non-superconducting second phase, ion irradiation and element substitution. However, the current methods either need to control the composition during growth or need to use expensive irradiation equipment, and there is a lack of low-cost and simple post-processing methods for introducing artificial pinning centers. SUMMARY

[0003] To solve the above technical problems, the application provides a method for improving the current-carrying capacity of a REBCO superconducting layer in a magnetic field, which introduces high-density dislocations as pinning centers by a mechanical method to improve the field performance of REBCO, so as to solve 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 purpose, the application provides a method for improving the current-carrying capacity of a REBCO superconducting layer in a magnetic field, comprising:

[0005] A auxiliary layer is deposited on the surface of the REBCO superconducting layer, and the auxiliary layer is rotated and ground on sandpaper with a cleaning liquid to introduce dislocations on the surface of the REBCO superconducting layer, and then the ground REBCO superconducting layer is cleaned on the surface with a cleaning liquid and then a silver layer is deposited thereon, and then oxygen absorption treatment is performed to obtain the final REBCO superconducting tape.

[0006] Optionally, the auxiliary layer is made of CeO2 or Al2O3, and the deposition method is magnetron sputtering, the gas pressure is 100 Pa, and the frequency is 300 Hz.

[0007] Optionally, the thickness of the auxiliary layer is 2 nm-10 nm, the mesh number of the sandpaper is 2000 mesh-5000 mesh, the force applied during grinding is 0.5 N-5 N, the grinding time is 1 min-5 min, and the grinding speed is 50 rmp-200 rmp.

[0008] Optionally, the cleaning liquid is anhydrous organic cleaning liquid, including ethanol, ethylene glycol or propylene glycol.

[0009] Optionally, the REBCO superconducting layer is disposed on the buffer layer, the buffer layer is deposited on the metal-based strip, and the REBCO superconducting layer is doped or undoped REBa2Cu3O 7-δ with a thickness of 500 nm or more.

[0010] Optionally, the REBCO superconducting layer is REBa2Cu3O 7-δ , wherein RE is a mixed element of one or more of 17 rare earth elements including Sc and Y.

[0011] Optionally, when the REBCO superconducting layer is doped REBa2Cu3O 7-δ , the doping material is perovskite Ba M O3, Ba2RE N O6 or other non-superconducting phases, wherein, in Ba M O3, M one or more of Zr, Hf and Sn; in Ba2RE N O6, RE is a mixed element of one or more of rare earth elements, N one or more of Nb and Ta; and the other non-superconducting phase includes RE2O3, SiO2 and BaCuO2.

[0012] Optionally, the buffer layer is a single-layer or multi-layer oxide film.

[0013] When the buffer layer is a single layer, the oxide film composition is MgO.

[0014] When the buffer layer is a multi-layer oxide film, the oxide film composition is a multi-layer structure formed by Y2O3, YSZ and CeO2 in sequence; or a multi-layer structure formed by Al2O3, Y2O3, MgO and LaMnO3 in sequence; or a multi-layer structure formed by Al2O3, Y2O3, MgO and CeO2 in sequence.

[0015] Optionally, the metal-based strip is a nickel-based or copper-based flexible metal-based strip.

[0016] Optionally, the REBCO superconducting layer is ion-irradiated or not ion-irradiated.

[0017] Compared with the prior art, the present application has the following advantages and technical effects:

[0018] The application introduces high-density dislocations in a cheap and simple way, thereby improving the field performance of the REBCO superconducting layer. High-density dislocations of >10^ 14 / m 2 are generated in the REBCO tape, so that the critical current density ( J c ) at a Kelvin temperature of 50K and a magnetic field magnetic induction of 5T is greater than 2MA / cm 2 . BRIEF DESCRIPTION OF DRAWINGS

[0019] The accompanying drawings, which form a part of the present application, are intended to provide further understanding of the present application and serve to explain the schematic embodiments of the present application and their descriptions, and do not constitute an improper limitation to the present application. In the drawings:

[0020] Figure 1 is a device structure schematic diagram of an embodiment of the application;

[0021] wherein 1 is a REBCO superconducting layer, 2 is a buffer layer, and 3 is a metal-based tape. DETAILED DESCRIPTION

[0022] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0023] It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a group of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described herein can be executed in an order different from that shown herein.

[0024] In the present application, the REBCO film is deposited on the base tape using a conventional method for those skilled in the art, as an exemplary:

[0025] Pulsed Laser Deposition (PLD). The equipment used in this technology generally consists of an excimer laser, an optical system, and a vacuum system. The optical system consists of focusing lenses and laser windows, and the vacuum system includes a vacuum chamber, a vacuum pump, a target material system, and a heater. The working principle of the PLD system is as follows: a high-power pulsed laser beam is provided by an excimer laser, which is focused into the vacuum chamber through the optical system and acts on the target material surface. The target material surface is subjected to high-temperature ablation to produce high-temperature and high-pressure plasma, which expands to form a plume. The plasma plume is directed to the substrate surface, and finally a thin film is deposited. The advantages of the PLD method are as follows: good repeatability, high deposition rate, large-area formation of high-quality thin films, and low substrate temperature requirement. It is worth noting that the PLD method has little damage to the formed thin film and substrate, and the composition of the deposited thin film is basically consistent with that of the target material, with precise stoichiometric ratio. The above two points are particularly outstanding when preparing superconducting layer thin films of REBCO materials with large molecular mass, and are a widely used preparation method. By setting parameters such as laser energy, laser frequency, focal length of focusing lenses in the optical path, distance between target and substrate (target distance), and substrate temperature, various REBCO materials can be prepared.

[0026] Metal Organic Chemical Vapor Deposition (MOCVD) is a thin film deposition technology developed on the basis of chemical vapor deposition technology, and is widely used for various thin film deposition. The typical process of MOCVD deposition of REBCO film is as follows: RE, Ba, and Cu organic salts (such as tetramethylheptane diol salt, etc.) are mixed and dissolved in an organic solvent (such as diglycol dimethyl ether, xylene, etc.) as source material, the solvent and organic salt are separated by an evaporation dish, and oxygen is used as a carrier to pump the gaseous organic salt into the reaction chamber to uniformly deposit on the substrate surface, and then REBCO film is obtained by in-situ heating reaction. MOCVD can deposit REBCO film in one step, with the advantages of fast growth speed, uniform film composition, easy control of element ratio, and no size limitation of deposition area.

[0027] The reactive co-evaporation by deposition and reaction (RCE-DR) is a physical vapor deposition technology based on electron beam co-evaporation. The high-energy electron beam is used to directly heat and evaporate the target material in vacuum and transport it to the substrate to realize thin film deposition. The electron beam is used to evaporate the metal Gd, Ba and Cu targets. The three metal vapors enter the reaction chamber in a specific ratio. Through the control of temperature and oxygen partial pressure, the precursor film is formed on the substrate. Through the heat treatment in the low and high oxygen partial pressure zones, the REBCO film is obtained. This process is a typical ex situ method, which can produce REBCO superconducting tapes at a faster speed (120 meters / hour) and accurately control the proportion of each element.

[0028] The metal-organic decomposition (MOD) is a method for preparing thin film materials. The metal-organic compound solution is coated on the substrate, and then decomposed by heat treatment to form an oxide film. The typical process for preparing REBCO film is to dissolve the carboxylate salt (such as isooctanoate, etc.), nitrate or β-diketone salt (such as acetylacetone, etc.) which is not sensitive to hydrolysis in a certain stoichiometric ratio in a non-polar solvent (methanol, toluene, etc.) to prepare a precursor solution. The precursor solution is coated on the superconducting substrate, and then pyrolysis and sintering are carried out to form a composite oxide film. Due to the release of CO2 and H2O during pyrolysis, the volume will change greatly, so the pyrolysis process needs to be strictly controlled to avoid the generation of biaxial tensile force in the oxide film during pyrolysis, which may cause the film to crack. The MOD method for REBCO film deposition can be divided into two types: trifluoroacetic acid metal organic salt deposition (TFA-MOD) and fluorine-free metal organic salt deposition (FF-MOD) according to the metal salt used.

[0029] As shown in Figure 1 In this embodiment, a method for improving the current-carrying capacity of the REBCO superconducting layer 1 in a magnetic field is provided, which can improve the field current-carrying capacity of the REBCO tape, comprising:

[0030] A layer of auxiliary layer is deposited on the surface of the REBCO superconducting layer 1, a cleaning liquid is added, and the auxiliary layer is rotated and ground on sandpaper, so that high-density dislocations are introduced into the REBCO superconducting layer 1. After grinding, the REBCO superconducting layer 1 is cleaned and a silver layer is deposited thereon. The REBCO superconducting layer 1 after deposition of the silver layer is subjected to oxygen absorption treatment to obtain the REBCO superconducting layer 1 with improved performance, i.e. the final REBCO superconducting tape.

[0031] Specifically, a 2 nm to 10 nm thick auxiliary layer (CeO2 / Al2O3) is first deposited on the surface of the REBCO superconducting layer 1, then the auxiliary layer is directed towards the sandpaper (2000-5000 mesh) and a certain force (0.5N-5N) is applied, and the cleaning liquid (ethanol, ethylene glycol or propylene glycol) is rotated and ground (1-5min, 50-200 rmp), thereby introducing high-density dislocations into the REBCO superconducting layer 1, then the cleaning liquid is washed, and the silver layer is deposited after washing, and then oxygen absorption treatment is carried out, so that the field performance is improved.

[0032] Under the action of the magnetic field, the magnetic lines of force will enter the REBCO superconducting layer 1 and form magnetic flux vortices, which can move under the action of the magnetic field to destroy the non-dissipative transmission capability. The dislocation can effectively limit the movement of the magnetic flux vortex as a pinning center of the magnetic flux vortex, thereby improving the field performance.

[0033] Specifically, the REBCO superconducting layer 1 is a doped or undoped REBa2Cu3O 7-δ with a thickness of 500 nm or more.

[0034] Specifically, the "RE" in the REBCO superconducting layer 1 is a mixed element containing one or more of Sc and Y rare earth elements.

[0035] The above rare earth elements are scandium (Sc) and 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 the REBCO superconducting layer 1 can be any one or more of the above mixed rare earth elements, and the material of the REBCO superconducting layer 1 of any one rare earth element can be ScBCO, YBCO, LaBCO, CeBCO, PrBCO, NdBCO, PmBCO, SmBCO, EuBCO, GdBCO, TbBCO, DyBCO, HoBCO, ErBCO, TmBCO, YbBCO, LuBCO, and the material of the REBCO superconducting layer 1 of 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. (The range of x is 0-1, the range of y is 0-1, and x+y≤1)

[0036] The REBCO superconducting layer 1 of any rare earth element or a mixture of several rare earth elements can introduce high-density dislocations through the above scheme.

[0037] Specifically, if the REBCO superconducting layer 1 is doped with REBa2Cu3O 7-δ , the doping material is Ba M O3 or Ba2RE N O6 or other non-superconducting phases; in Ba M O3, M one or a mixture of several elements selected from Zr, Hf, Sn; in Ba2RE N O6, RE is selected from one or a mixture of several rare earth elements selected from Y, Gd, Eu, Sm, N one or a mixture of several elements selected from Nb, Ta; other non-superconducting phases include but are not limited to RE2O3, SiO2, BaCuO2.

[0038] When the doping material is Ba M O3, M when one element is selected from Zr, Hf, Sn, the material is BaZrO3, BaHfO3, BaSnO3; M when a mixture of elements is selected from Zr, Hf, 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,

[0039] When the doping material is Ba2RE N O6, RE is selected from one or a mixture of several rare earth elements selected from Y, Gd, Eu, Sm, N one or a mixture of several elements selected from Nb, Ta, the above material 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(Nby Ta 1-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.

[0040] 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.

[0041] Specifically, REBCO superconducting layer 1 may or may not have been irradiated with ions.

[0042] 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.

[0043] 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.

[0044] It is feasible that, when the buffer layer is a single layer, the oxide film composition is MgO;

[0045] When the buffer layer is a multilayer oxide film, the oxide film composition is a multilayer structure formed in sequence by Y2O3, YSZ and CeO2; or a multilayer structure formed in sequence by Al2O3, Y2O3, MgO and LaMnO3; or a multilayer structure formed in sequence by Al2O3, Y2O3, MgO and CeO2.

[0046] The oxygen absorption process is a general processing method for REBCO from tetragonal phase to orthorhombic phase transition, and does not limit the conditions.

[0047] The above technical solutions are described in detail as follows:

[0048] Embodiment 1

[0049] On the surface of EuBCO superconducting film doped with BaHfO3 (BHO) (doping ratio 3.5 mol%) (the preparation method of the superconducting film is described in reference literature Wu Yue, Shi Jiangtao, Guo Chunjiang, et al., Ultra-fast dynamic deposition of EuBa2Cu3O7-δ-BaHfO3 nanocomposite films: Self-assembly structure modulation and flux pinning behaviors[J], Materials & Design, 2022, 224: 111406), a 2 nm thick auxiliary layer (CeO2) is first deposited, then the auxiliary layer is directed towards the sandpaper (5000 mesh) and a certain force (0.5 N) is applied, and the cleaning liquid (ethanol) is rotated and ground (5 min, 50 rpm), so as to introduce high-density dislocations into the EuBCO superconducting layer, and the dislocation density is 2.1×10 14 / m 2 Then, the cleaning liquid is cleaned, the silver layer is deposited after cleaning, and then the oxygen absorption treatment is performed, the critical current density (J c ) is 2.5 MA / cm 2 , which is nearly doubled compared with the critical current density 1.3 MA / cm 2 of the original sample.

[0050] Embodiment 2

[0051] On the surface of GdBa2Cu3O 7-δ(GdBCO) superconducting film (see reference for superconducting film preparation method Shi Jiangtao, Zhao Yue, Jiang Guangyu, et al., Deposition of REBCO with different rare earth elements on CeO2 buffered technical substrates by fluorine-free metal organic decomposition route[J], Journal of the European Ceramic Society, 2021, 41:5223-5229.) first deposited a 10 nm thick auxiliary layer (CeO2) on the surface, then the auxiliary layer was faced to the sandpaper (2000 mesh) and a certain force (5N) was applied, and the cleaning liquid (propylene glycol) was rotated and ground (1 min 200 rmp), so as to introduce high density dislocations in the GdBCO superconducting layer, and the dislocation density was 5×10 14 / m 2 , then washed with cleaning liquid, deposited silver layer after washing, then oxygen absorption treatment, critical current density (Jc) of 3.2 MA / cm J c at 50K Kelvin temperature and 5T magnetic field magnetic induction intensity. 2 .

[0052] Example 3

[0053] Y x Pr 1-x Ba2Cu3O 7-δ (Y x Pr 1-xBCO, 0<x<1) superconducting film (see reference literature 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.) surface first deposited a 10 nm thick auxiliary layer (Al2O3), then the auxiliary layer towards the sandpaper (5000 mesh) and apply a certain force (5N), add cleaning fluid (propylene glycol) rotary grinding (3 min, 100 rmp), so as to Y x Pr 1-x High-density dislocations are introduced into the BCO film, and the dislocation density is 1.5×10^ 14 / m 2 , then washed with cleaning fluid, then deposited silver layer, then oxygen absorption treatment, critical current density (Jc) is 1.8 MA / cm J c at 50K Kelvin temperature and 5T magnetic field magnetic induction intensity. 2

[0054] Comparative Example 1

[0055] The surface of the GdBCO superconducting film is not deposited with an auxiliary layer, and it is directed towards the sandpaper (2000 mesh) and a certain force (5N) is applied, and cleaning fluid (propylene glycol) is added for rotary grinding (1 min, 200 rmp), then washed with cleaning fluid, then deposited silver layer, and high-density dislocations cannot be generated in the GdBCO superconducting layer, and after oxygen absorption treatment, the critical current density (Jc) is the same as the original sample, only 1.1 MA / cm J c at 50K Kelvin temperature and 5T magnetic field magnetic induction intensity. 2

[0056] Comparative Example 2

[0057] ​​A 2 nm thick auxiliary layer (CeO2) was first deposited on the surface of EuBCO superconducting film doped with BHO (doping ratio 3.5 mol%), then the auxiliary layer was directed towards the sandpaper (500 mesh) and a certain force (20 N) was applied, and the cleaning liquid (ethanol) was rotated and ground (10 min, 500 rpm), and then washed with cleaning liquid, and after washing, a silver layer was deposited, and high-density dislocations could not be generated in the EuBCO superconducting layer after oxygen absorption treatment, and the critical current density (Jc) of the sample was 1.3 MA / cm2 at a kelvin temperature of 50 K and a magnetic field magnetic induction intensity of 5 T, which was the same as that of the original sample. J c ) with the original sample. 2 .

[0058] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection 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 polished on sandpaper with a cleaning solution to introduce dislocations on the surface of the REBCO superconducting layer. After the polished REBCO superconducting layer is cleaned with a cleaning solution, a silver layer is deposited, and then oxygen absorption treatment is performed to obtain the final REBCO superconducting tape. The auxiliary layer is made of CeO2 or Al2O3; 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.

2. The method according to claim 1, characterized in that, The auxiliary layer was deposited using magnetron sputtering at a pressure of 100 Pa and a frequency of 300 Hz.

3. 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.

4. 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.

5. 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.

6. 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.

7. The method according to claim 4, 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.

8. The method according to claim 4, characterized in that, The metal substrate is a nickel-based or copper-based flexible metal substrate.

9. The method according to claim 6, characterized in that, The REBCO superconducting layer may or may not have been irradiated with ions.

Images