A method for producing a REBCO superconducting thick film

Abstract

The application discloses a preparation method of REBCO superconducting thick film and belongs to the technical field of superconducting materials. The preparation method of the REBCO superconducting thick film comprises the following steps: depositing an REBCO layer on a base band by using a superconducting layer deposition method, then depositing an auxiliary polishing layer, then adding a cleaning liquid to perform rotary polishing, obtaining the REBCO layer with a smooth surface, and then repeatedly depositing the REBCO layer, depositing the auxiliary polishing layer and performing the rotary polishing step on the REBCO layer with the smooth surface to obtain the REBCO superconducting thick film. The method can obtain the REBCO superconducting thick film with a thickness of greater than or equal to 4 microns, and the critical current density I c of the superconducting layer linearly increases (namely, J c does not obviously decrease with the increase of the thickness).

Description

Technical Field

[0001] This invention relates to the field of superconducting materials technology, and in particular to a method for preparing REBCO superconducting thick films. Background Technology

[0002] Second-generation high-temperature superconductor (REBa2Cu3O) 7-δ REBCO (where RE represents rare earth elements) superconducting 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 high current-carrying capacity. The critical current (Ic) of REBCO superconducting tapes is... c Theoretically, the critical current density (J / L) is positively correlated with the thickness of the superconducting layer. However, in reality, as the thickness of the deposited superconducting layer increases, microstructural degradation such as grain and grain boundary coarsening, increased surface roughness and microporosity, growth of a-axis oriented grains, and increased residual tensile stress leads to a decrease in the critical current density (J / L). c The current carrying capacity of REBCO films decreases significantly, a problem known as the thickness effect. Currently, there is a lack of effective methods to remove surface degradation structures with minimal damage to the REBCO superconducting layer. Considering the cost-benefit ratio, the thickness of the superconducting layer in industrially produced REBCO tapes is typically no more than 3 μm, which severely limits the current carrying capacity of REBCO films. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing REBCO superconducting thick films to solve the problems existing in the prior art.

[0004] To achieve the above objectives, the present invention provides the following solution:

[0005] One of the technical solutions of the present invention: a method for preparing a REBCO superconducting thick film, comprising the following steps:

[0006] A REBCO layer is deposited on a substrate using a superconducting layer deposition method, followed by the deposition of an auxiliary polishing layer. Then, a cleaning solution is added for spin polishing to obtain a smooth REBCO layer. The steps of depositing a REBCO layer, depositing an auxiliary polishing layer, and spin polishing are repeated on the smooth REBCO layer to obtain the REBCO superconducting thick film.

[0007] Depositing a REBCO layer on the baseband followed by an auxiliary polishing layer and then performing spin polishing yields a REBCO layer with extremely high surface smoothness. Continuing to deposit more REBCO layers addresses microstructural degradation issues within the superconducting layer, such as grain and grain boundary coarsening, increased surface roughness and microporosity, growth of a-axis oriented grains, and increased residual tensile stress. This ultimately enables the achievement of the critical current (IC) in the REBCO tape. c The technical effect increases with the increase of superconducting layer thickness.

[0008] Furthermore, the thickness of the REBCO layer deposited each time is 500~1000 nm;

[0009] The thickness of the REBCO superconducting thick film is ≥4μm.

[0010] Furthermore, the thickness of the auxiliary polishing layer is 2~10nm;

[0011] The auxiliary polishing layer is in the form of amorphous or nanocrystalline morphology;

[0012] The deposition temperature of the auxiliary polishing layer is room temperature (20~30℃).

[0013] A thickness greater than 10nm in the auxiliary polishing layer will result in excessive wear of the superconducting layer and poor flatness, while a thickness less than 2nm will not achieve the desired polishing effect.

[0014] Furthermore, the material of the auxiliary polishing layer includes CeO2 or Al2O3.

[0015] CeO2 and Al2O3 have suitable hardness, making them suitable for polishing to obtain a smooth REBCO layer, and CeO2 and Al2O3 do not react with the superconducting layer.

[0016] Further, the rotary polishing specifically includes: aligning the auxiliary polishing layer with the polishing cloth and applying a force of 0.1~5N to perform rotary polishing until the surface root mean square roughness (Rm) is achieved. q For particles smaller than 10nm, a cleaning solution is added during the polishing process. The cleaning solution may include ethanol, ethylene glycol, or propylene glycol.

[0017] Rotary polishing with a force greater than 5N will result in excessive wear and poor smoothness, while a force less than 0.1N will not achieve the desired polishing effect.

[0018] The rotational polishing speed is 50~200 rpm, and the time is 1~5 min;

[0019] The polishing cloth is selected from silk polishing cloth, cashmere polishing cloth, real silk velvet polishing cloth or flocked polishing cloth.

[0020] Rotary polishing speeds greater than 200 rpm will result in excessive wear, poor flatness, and a large amount of heat-affected superconducting layer; speeds less than 50 rpm will not achieve the desired polishing effect. Rotary polishing time greater than 5 minutes will result in excessive wear and poor flatness; speeds less than 1 minute will not achieve the desired polishing effect.

[0021] Currently, the preparation of REBCO thick films mainly employs a multiple deposition method, while thick film J cThe main reason for the decrease in thickness is the deterioration of the surface structure with increasing thickness, which makes it difficult for subsequently deposited REBCO to epitaxially grow into a REBCO phase with biaxial texture. Due to the effect of weak grain boundary connections, these formed REBCO phases do not have the function of carrying current. Therefore, removing the surface deterioration layer can help grow superconducting thick films.

[0022] Furthermore, the superconducting layer deposition method includes pulsed laser deposition (PLD), metal-organic chemical vapor deposition (MOCVD), reactive electron beam co-evaporation-deposition reaction (RCE-DR), or metal-organic salt decomposition (MOD), etc.

[0023] Furthermore, the REBCO layer comprises doped or undoped REBa2Cu3O 7-δ layer;

[0024] The doped components include non-superconducting phases such as BaMO3, Ba2(RE,Y)NO6, SiO2, BaCuO2, or rare earth oxides RE2O3;

[0025] M is selected from one or more of Zr, Hf, Sn and Ce;

[0026] RE is selected from one or more rare earth elements;

[0027] N is selected from Nb and / or Ta;

[0028] The rare earth elements are Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.

[0029] All of the REBCO layers provided by this invention can be used to prepare REBCO superconducting thick films using the method of this invention, and achieve I... c The effect of linearly increasing the thickness of the strip improves its current carrying capacity.

[0030] Furthermore, the baseband is a metal baseband coated with a single layer or multiple layers of oxide buffer layer;

[0031] The metal substrate includes a nickel-based or copper-based flexible metal substrate.

[0032] Furthermore, the structure of the oxide buffer layer includes one of the following: a CeO2 / YSZ / Y2O3 three-layer oxide buffer layer, a MgO single-layer oxide buffer layer, a LaMnO3 / MgO / Y2O3 / Al2O3 four-layer oxide buffer layer, a CeO2 / LaMnO3 / MgO / Y2O3 / Al2O3 five-layer oxide buffer layer, or a CeO2 / MgO / Y2O3 / Al2O3 four-layer oxide buffer layer.

[0033] When metal substrates coated with single or multiple oxide buffer layers are used to prepare REBCO superconducting thick films, oxygen diffusion to the substrate can be prevented, a biaxial texture of a single-crystal REBCO without weak connections can be formed, and the lattice of the substrate can be matched with that of REBCO.

[0034] The second technical solution of the present invention: a REBCO superconducting thick film prepared by the above preparation method.

[0035] The present invention discloses the following technical effects:

[0036] The multi-deposition method of this invention, which involves stepwise deposition of a superconducting layer, followed by deposition of an auxiliary polishing layer and spin polishing, can achieve a REBCO superconducting layer thickness ≥4 μm, and I c Linear increase (i.e., J) c It will not show a significant decrease as the thickness increases.

[0037] The method of the present invention is a method for growing superconducting films with a superconducting layer surface treatment, which can achieve I c The current carrying capacity of the strip increases linearly with thickness. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 An atomic force microscope image of the polished amorphous CeO2 surface layer prepared in Example 1 of this invention;

[0040] Figure 2 I represents EuBCO membranes of different thicknesses prepared in Example 1 of this invention. c change. Detailed Implementation

[0041] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0042] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0043] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0044] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0045] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0046] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0047] 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:

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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 the compound 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 nonpolar 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 used 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).

[0052] For example, the film layer in the REBCO superconducting thick film prepared in this invention can be doped or undoped ScBa2Cu3O 7-δ Layer, YBa2Cu3O 7-δ Layer, LaBa2Cu3O 7-δ Layer, CeBa2Cu3O 7-δ Layer, PrBa2Cu3O 7-δ Layer, NdBa2Cu3O 7-δ Layer, PmBa2Cu3O 7-δ Layer, SmBa2Cu3O 7-δ Layer, EuBa2Cu3O 7-δ Layer, GdBa2Cu3O 7-δ Layer, TbBa2Cu3O 7-δ Layer, DyBa2Cu3O7-δ Layer, HoBa2Cu3O 7-δ Layer, ErBa2Cu3O 7-δ Layer, TmBa2Cu3O 7-δ Layer, YbBa2Cu3O 7-δ Layer or LuBa2Cu3O 7-δ layer.

[0053] For example, the film layer in the REBCO superconducting thick film prepared in this invention can be ScBa2Cu3O doped with BaMO3. 7-δ Layer, YBa2Cu3O 7-δ Layer, LaBa2Cu3O 7-δ Layer, CeBa2Cu3O 7-δ Layer, PrBa2Cu3O 7-δ Layer, NdBa2Cu3O 7-δ Layer, PmBa2Cu3O 7-δ Layer, SmBa2Cu3O 7-δ Layer, EuBa2Cu3O 7-δ Layer, GdBa2Cu3O 7-δ Layer, TbBa2Cu3O 7-δ Layer, DyBa2Cu3O 7-δ Layer, HoBa2Cu3O 7-δ Layer, ErBa2Cu3O 7-δ Layer, TmBa2Cu3O 7-δ Layer, YbBa2Cu3O 7-δ Layer or LuBa2Cu3O 7-δ layer.

[0054] For example, the doping amount of BaMO3 is 0 to 30 molar percentage and is not 0; wherein M is selected from one or more of Zr, Hf, Sn and Ce.

[0055] For example, the film layer in the REBCO superconducting thick film prepared in this invention can be ScBa2Cu3O doped with Ba2(RE,Y)NO6. 7-δ Layer, YBa2Cu3O 7-δ Layer, LaBa2Cu3O 7-δ Layer, CeBa2Cu3O 7-δ Layer, PrBa2Cu3O 7-δ Layer, NdBa2Cu3O 7-δ Layer, PmBa2Cu3O 7-δ Layer, SmBa2Cu3O 7-δ Layer, EuBa2Cu3O 7-δ Layer, GdBa2Cu3O 7-δLayer, TbBa2Cu3O 7-δ Layer, DyBa2Cu3O 7-δ Layer, HoBa2Cu3O 7-δ Layer, ErBa2Cu3O 7-δ Layer, TmBa2Cu3O 7-δ Layer, YbBa2Cu3O 7-δ Layer or LuBa2Cu3O 7-δ layer.

[0056] For example, the doping amount of Ba2(RE,Y)NO6 is 0 to 30 molar percentage and is not 0; wherein RE is selected from one or more rare earth elements; and N is selected from Nb and / or Ta.

[0057] For example, the metal substrate used in this invention is a nickel-based flexible metal substrate coated with a single layer of MgO buffer layer, a copper-based flexible metal substrate coated with a single layer of MgO buffer layer, a nickel-based flexible metal substrate coated with multiple layers of oxide buffer layer, or a copper-based flexible metal substrate coated with multiple layers of oxide buffer layer.

[0058] For example, the multilayer oxide buffer layer can be one of the following: a CeO2 / YSZ / Y2O3 three-layer oxide buffer layer (the thickness of each layer can refer to the prior art), a MgO single-layer oxide buffer layer, a LaMnO3 / MgO / Y2O3 / Al2O3 four-layer oxide buffer layer (the thickness of each layer can refer to the prior art), a CeO2 / LaMnO3 / MgO / Y2O3 / Al2O3 five-layer oxide buffer layer (the thickness of each layer can refer to the prior art), and a CeO2 / MgO / Y2O3 / Al2O3 four-layer oxide buffer layer (the thickness of each layer can refer to the prior art).

[0059] Optionally, the thickness of the copper-based flexible metal substrate and the nickel-based flexible metal substrate is 30 μm to 100 μm; the thickness of the single-layer MgO buffer layer is about 300 nm; and the total thickness of the multi-layer oxide buffer layer is about 300 nm.

[0060] For example, the REBCO superconducting thick film can be prepared by any of the following methods:

[0061] Method 1: A 1 μm thick EuBa2Cu3O layer was deposited on a CeO2 / LaMnO3 / MgO / Y2O3 / Al2O3 / C276 Hastelloy metal substrate with a substrate structure of CeO2 / LaMnO3 / MgO / Y2O3 / Al2O3 / C276 using pulsed laser deposition (PLD). 7-δA layer was first deposited, and then a 2 nm thick CeO2 auxiliary polishing layer was deposited on its surface. Next, the auxiliary polishing layer was placed towards a silk polishing cloth (W 0.25-0.5), and a force of 0.1 N was applied. Rotary polishing was performed at 50 rpm, with ethanol cleaning solution added during the polishing process. After 1 minute of polishing, a smooth EuBa2Cu3O2 surface was obtained. 7-δ The layer has a root mean square roughness (R) of its surface. q <10nm. In the polished EuBa2Cu3O 7-δ A 1 μm thick layer of EuBa2Cu3O was deposited again on the layer. 7-δ A second 2nm thick CeO2-assisted polishing layer is deposited and polished. This process is repeated to obtain an EuBa2Cu3O layer with a thickness ≥4μm. 7-δ Superconducting thick film (i.e., REBCO superconducting thick film).

[0062] Method 2: Deposit a 500 nm thick layer of YBa2Cu3O on a nickel-based flexible metal substrate coated with a monolayer MgO buffer layer using metal-organic chemical vapor deposition (MOCVD). 7-δ A layer was first deposited, and then a 2 nm thick CeO2 auxiliary polishing layer was deposited on its surface. Next, the auxiliary polishing layer was placed towards a silk polishing cloth (W 0.25-0.5), and a force of 0.1 N was applied. Rotary polishing was performed at 50 rpm, with ethanol cleaning solution added during the polishing process. After 1 minute of polishing, a smooth YBa2Cu3O2 surface was obtained. 7-δ The layer has a root mean square roughness (R) of its surface. q <10nm. In the polished YBa2Cu3O 7-δ A 500 nm thick layer of YBa2Cu3O was deposited again on the layer. 7-δ A second 2nm thick CeO2-assisted polishing layer is deposited and polished. This process is repeated to obtain a YBa2Cu3O layer with a thickness ≥4μm. 7-δ Superconducting thick film (i.e., REBCO superconducting thick film).

[0063] Method 3: Deposit a 1 μm thick layer of GdBa2Cu3O on a copper-based flexible metal substrate (commercially available product) coated with a monolayer MgO buffer layer using pulsed laser deposition (PLD). 7-δ A layer was first deposited, and then a 2 nm thick CeO2 auxiliary polishing layer was deposited on its surface. Next, the auxiliary polishing layer was placed towards a silk polishing cloth (W 0.25-0.5), and a force of 0.1 N was applied. Rotary polishing was performed at 50 rpm, with ethanol cleaning solution added during the polishing process. After 1 minute of polishing, a smooth GdBa2Cu3O2 surface was obtained. 7-δ The layer has a root mean square roughness (R) of its surface. q<10nm. In the polished GdBa2Cu3O 7-δ A 1 μm thick layer of GdBa2Cu3O was deposited again on the layer. 7-δ A second 2nm thick CeO2-assisted polishing layer is deposited and polished. This process is repeated to obtain a GdBa2Cu3O layer with a thickness ≥4μm. 7-δ Superconducting thick film (i.e., REBCO superconducting thick film).

[0064] Method 4: Deposit a 1 μm thick Y-coated MgO layer on a nickel-based flexible metal substrate (commercially available product) coated with a monolayer MgO buffer layer using pulsed laser deposition (PLD). x Gd 1-x Ba2Cu3O 7-δ A layer was first deposited, followed by a 2nm thick CeO2 auxiliary polishing layer. Then, the auxiliary polishing layer was placed towards a silk polishing cloth (W 0.25-0.5), and a force of 0.1N was applied. Rotary polishing was performed at 50rpm, with ethanol cleaning solution added during the polishing process. After 1 minute of polishing, a smooth YO2 surface was obtained. x Gd 1- x Ba2Cu3O 7-δ The layer has a root mean square roughness (R) of its surface. q <10 nm. In the polished Y... x Gd 1-x Ba2Cu3O 7-δ A 1 μm thick layer of Y was deposited again on the layer. x Gd 1-x Ba2Cu3O 7-δ A second 2nm thick CeO2-assisted polishing layer is deposited and polished, and this process is repeated to obtain a Y layer with a thickness ≥4μm. x Gd 1-x Ba2Cu3O 7-δ Superconducting thick film (i.e., REBCO superconducting thick film).

[0065] Method 5: Deposit a 500 nm thick layer of DyBa2Cu3O on a nickel-based flexible metal substrate (commercially available product) coated with a monolayer MgO buffer layer using pulsed laser deposition (PLD). 7-δ A layer was first deposited, and then a 2 nm thick CeO2 auxiliary polishing layer was deposited on its surface. Next, the auxiliary polishing layer was placed towards a silk polishing cloth (W 0.25-0.5), and a force of 0.1 N was applied. Rotary polishing was performed at 50 rpm, with ethanol cleaning solution added during the polishing process. After 1 minute of polishing, a smooth DyBa2Cu3O2 surface was obtained. 7-δ The layer has a root mean square roughness (R) of its surface. q <10nm. In the polished DyBa2Cu3O7-δ A 500 nm thick layer of DyBa2Cu3O was deposited again on the layer. 7-δ A second 2nm thick CeO2-assisted polishing layer is deposited and polished. This process is repeated to obtain a DyBa2Cu3O layer with a thickness ≥4μm. 7-δ Superconducting thick film (i.e., REBCO superconducting thick film).

[0066] REBCO superconducting thick films containing other rare earth elements or using other metal substrates can also be prepared using the same method, all of which can achieve I0 c The effect of a technology that increases linearly with thickness.

[0067] In the embodiments of this invention, the room temperature refers to 20~30℃.

[0068] Example 1

[0069] A method for preparing REBCO superconducting thick films:

[0070] (1) A 1 μm thick layer of BaZrO3-doped EuBa2Cu3O3 was deposited on a CeO2 / LaMnO3 / MgO / Y2O3 / Al2O3 / C276 Hastelloy metal substrate using pulsed laser deposition (PLD). 7-δ A 2 nm thick amorphous CeO2 auxiliary polishing layer was deposited on the surface of a EuBCO layer at room temperature. The auxiliary polishing layer was then placed towards a flocked polishing cloth, and a force of 0.1 N was applied. Rotary polishing was performed at 50 rpm, with ethanol added as a cleaning agent during the polishing process. After 1 minute of polishing, a smooth EuBCO layer was obtained, with a root mean square roughness (R0) of [value missing]. q The wavelength is 5.0 ± 0.02 nm, and the thickness of the superconducting layer after polishing is approximately 0.95 μm.

[0071] Atomic force microscopy images of the amorphous CeO2-assisted polishing layer are shown below. Figure 1 .

[0072] (2) A 1 μm thick EuBCO layer is deposited again on the polished EuBCO layer, and a 2 nm thick amorphous CeO2 auxiliary polishing layer is deposited on its surface and polished. This process is repeated to obtain EuBCO superconducting thick films (i.e., REBCO superconducting thick films) with thicknesses of approximately 0.95, 1.91, 2.88, 3.85, and 4.8 μm, respectively. c It can reach 820A.

[0073] EuBCO films of different thicknesses obtained by different deposition cycles under a self-field at 77K c See changes Figure 2 .

[0074] from Figure 2 As can be seen from I c It increases linearly with thickness.

[0075] Example 2

[0076] A method for preparing REBCO superconducting thick films:

[0077] (1) A 500 nm thick layer of GdBa2Cu3O was deposited on a LaMnO3 / MgO / Y2O3 / Al2O3 / C276 metal substrate using the organometallic decomposition (MOD) method. 7-δ A 10 nm thick nanocrystalline Al2O3 auxiliary polishing layer (i.e., GdBCO) was deposited on its surface at room temperature. The auxiliary polishing layer was then placed on a silk polishing cloth, and a force of 1 N was applied. Rotary polishing was performed at 200 rpm, with ethylene glycol cleaning solution added during the polishing process. After 2 minutes of polishing, the polishing cloth was replaced with a cashmere polishing cloth, and a force of 1 N was applied again. Rotary polishing was performed at 200 rpm, with ethylene glycol cleaning solution added during the polishing process. After 2 minutes of polishing, a smooth GdBCO layer was obtained, with a root mean square roughness (R0) of [missing value]. q The thickness of the superconducting layer is 7.0 ± 0.05 nm, and the thickness of the superconducting layer after polishing is approximately 420 nm.

[0078] (2) A 500 nm thick GdBCO layer was deposited again on the polished GdBCO layer, and a 10 nm thick nanocrystalline Al2O3 auxiliary polishing layer was deposited on its surface and polished. This process was repeated to obtain a 5.8 μm thick GdBCO superconducting thick film (i.e., REBCO superconducting thick film). c It can reach 1000A.

[0079] Among them, a 500nm thick layer of GdBa2Cu3O was deposited in one step. 7-δ Layer (i.e., GdBCO) I c The growth rate is approximately 175 Å, with the Ig of the 5.8 μm superconducting film... c It increases linearly with thickness.

[0080] Example 3

[0081] A method for preparing REBCO superconducting thick films:

[0082] (1) A 1 μm thick layer of YBa2Cu3O was deposited on a LaMnO3 / MgO / Y2O3 / Al2O3 / C276 Hastelloy metal substrate using reactive electron beam co-evaporation-deposition (RCE-DR) method. 7-δA 10 nm thick nanocrystalline CeO2 auxiliary polishing layer was deposited on the surface of a YBCO layer at room temperature. The auxiliary polishing layer was then placed on a silk polishing cloth, and a force of 5 N was applied. Rotary polishing was performed at 200 rpm, with propylene glycol cleaning solution added during the polishing process. After 1 minute of polishing, the polishing cloth was replaced with a silk polishing cloth, and a force of 0.5 N was applied. Rotary polishing was performed at 200 rpm, with ethylene glycol cleaning solution added during the polishing process. After 4 minutes of polishing, a smooth YBCO layer was obtained, with a root mean square roughness (R0) of [value missing]. q The value is 3.0 ± 0.05 nm.

[0083] (2) A 1 μm thick YBCO layer is deposited again on the polished YBCO layer, and a 10 nm thick nanocrystalline CeO2 auxiliary polishing layer is deposited on its surface and polished. This process is repeated to obtain a 4.6 μm thick YBCO superconducting thick film (i.e., REBCO superconducting thick film). c It can reach 900A.

[0084] Among them, a 1μm thick layer of YBa2Cu3O was deposited in one step. 7-δ Layer (i.e. YBCO) I c The growth rate is approximately 195 Å, with the Ig of the 4.6 μm superconducting film. c It increases linearly with thickness.

[0085] Example 4

[0086] A method for preparing REBCO superconducting thick films:

[0087] (1) A 500 μm thick layer of BaHfO3-doped EuBa2Cu3O3 was deposited on a MgO / Cu metal substrate using metal chemical vapor deposition (MOCVD). 7-δ A 2 nm thick amorphous CeO2 auxiliary polishing layer (EuBCO) was deposited on the surface of the EuBCO layer at room temperature. The auxiliary polishing layer was then placed towards a silk polishing cloth, and a force of 0.1 N was applied. Rotary polishing was performed at 50 rpm, with ethanol added as a cleaning agent during the polishing process. After 1 minute of polishing, a smooth EuBCO layer was obtained, with a root mean square roughness (R0) of [value missing]. q The value is 5.0 ± 0.02 nm.

[0088] (2) A 1 μm thick EuBCO layer is deposited again on the polished EuBCO layer, and a 2 nm thick amorphous CeO2 auxiliary polishing layer is deposited on its surface and polished. This process is repeated to obtain a EuBCO superconducting thick film with a thickness of approximately 4.3 μm (i.e., a REBCO superconducting thick film). c It can reach 822A.

[0089] Among them, a 1 μm thick EuBCO layer I was deposited once. c The growth rate is approximately 190 Å, with the Ig of the 4.3 μm superconducting film... c It increases linearly with thickness.

[0090] Comparative Example 1

[0091] A method for preparing a REBCO membrane:

[0092] A 1 μm thick layer of BaZrO3-doped EuBa2Cu3O3 was deposited on a metal substrate using pulsed laser deposition (PLD). 7-δ A layer (i.e., EuBCO) is deposited, and then the superconducting layer is faced with a silk polishing cloth, and a force of 0.1N is applied. Rotary polishing is performed at 50 rpm, with ethanol cleaning solution added during the polishing process. After 1 minute of polishing, a smooth EuBCO layer is not obtained, and EuBCO deposition continues. The I of the EuBCO tape... c It will show a significant attenuation with increasing thickness, I c The value is 610A. The reason is that the uneven surface affects the subsequent epitaxial growth of the superconducting layer.

[0093] Comparative Example 2

[0094] A method for preparing a REBCO membrane:

[0095] A 1 μm thick layer of YBa₂Cu₃O was deposited on a metal substrate using a reactive electron beam co-evaporation-deposition (RCE-DR) method. 7-δ A 100 nm thick nanocrystalline CeO2 auxiliary polishing layer was deposited on the surface of the YBCO layer at room temperature. Then, the auxiliary polishing layer was placed on a silk polishing cloth, and a force of 5 N was applied. Rotary polishing was performed at 200 rpm, with propylene glycol cleaning solution added during the polishing process. After 1 minute of polishing, the polishing cloth was replaced with a silk polishing cloth, and a force of 0.5 N was applied. Rotary polishing was performed at 200 rpm, with ethylene glycol cleaning solution added during the polishing process, resulting in the YBCO layer. A 1 μm thick YBCO layer was then deposited on top of the polished YBCO layer, and the polishing operation was repeated. This process was continued until the superconducting layer thickness exceeded 3 μm. c The thickness no longer increases linearly. This is because surface degradation substances have not been eliminated, affecting subsequent epitaxial growth of the YBCO superconducting layer.

[0096] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method of preparing a REBCO superconducting thick film, characterized by, The method comprises the following steps: The REBCO layer is deposited on the base band by using a superconducting layer deposition method, then an auxiliary polishing layer is deposited, and then a cleaning solution is added for rotary polishing to obtain a surface-smooth REBCO layer, and then the steps of depositing the REBCO layer, depositing the auxiliary polishing layer and rotary polishing are repeated on the surface-smooth REBCO layer to obtain the REBCO superconducting thick film; The thickness of the REBCO superconducting thick film is 4-5.8 μm, and the Ic thereof increases linearly with the thickness; The thickness of the auxiliary polishing layer is 2-10 nm; The rotary polishing speed is 50-200 rpm, and the rotary polishing time is 1-5 min; The auxiliary polishing layer is in an amorphous or nanocrystalline form; The deposition temperature of the auxiliary polishing layer is room temperature; The thickness of each deposited REBCO layer is 500-1000 nm; The material of the auxiliary polishing layer comprises CeO2 or Al2O3; The rotary polishing specifically comprises: the auxiliary polishing layer is directed towards a polishing cloth, and a force of 0.1-5 N is applied for rotary polishing until the surface root mean square roughness is less than 10 nm, and a cleaning solution is used during the rotary polishing; The cleaning solution comprises ethanol, ethylene glycol or propylene glycol; The polishing cloth is selected from silk polishing cloth, cashmere polishing cloth, silk polishing cloth or flock polishing cloth.

2. The production method according to claim 1, characterized by, The superconducting layer deposition method comprises a pulsed laser deposition method, a metal organic chemical vapor deposition method, a reactive e-beam co-evaporation-deposition reaction method or a metal organic salt decomposition method.

3. The preparation method according to claim 1, characterized in that, The REBCO layer comprises a doped or undoped REBa2Cu3O 7-δ layer; The doped component comprises BaMO3, Ba2(RE,Y)NO6, SiO2, BaCuO2 or a rare earth oxide RE2O3 non-superconducting phase; M is selected from one or more of Zr, Hf, Sn and Ce; RE is selected from one or more of rare earth elements; N is selected from Nb and / or Ta; The rare earth elements are Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.

4. The method of claim 1, wherein, The base band is a metal base band coated with a single-layer or multi-layer oxide buffer layer; The metal base band comprises a nickel-based or copper-based flexible metal base band.

5. The preparation method according to claim 4, characterized in that, The structure of the oxide buffer layer comprises one of CeO2 / YSZ / Y2O3, MgO, LaMnO3 / MgO / Y2O3 / Al2O3, CeO2 / LaMnO3 / MgO / Y2O3 / Al2O3 or CeO2 / MgO / Y2O3 / Al2O3.

6. An REBCO superconducting thick film prepared by the preparation method of any one of claims 1-5.

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