Preparation method of REBCO superconducting thick film

Abstract

The invention discloses a preparation method of an 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 solution for rotary polishing to obtain an REBCO layer with a flat surface, and then repeating the steps of REBCO layer deposition, auxiliary polishing layer deposition and rotary polishing on the REBCO layer with the flat surface to obtain the REBCO superconducting thick film. And the REBCO superconducting thick film is obtained. The REBCO superconductive thick film with the thickness of the superconductive layer being larger than or equal to 4 microns and the Ic being linearly increased (namely Jc is not obviously reduced along with the increase of the thickness) can be obtained by adopting the method disclosed by the invention.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of superconducting materials, in particular to a preparation method of a REBCO superconducting thick film. 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. The critical current (I c ) of the REBCO superconducting tape is theoretically positively correlated with the thickness of the superconducting layer, but in practice, as the thickness of the deposited superconducting layer increases, the microstructure deterioration such as grain and grain boundary coarsening in the superconducting layer, increase in surface roughness and microporosity, growth of a-axis oriented grains and increase in residual tensile stress will cause the critical current density (J c ) to decrease significantly, which is known as the thickness effect. At present, there is still no effective method to remove the surface structure deterioration structure without causing damage to the REBCO superconducting layer. Considering the input-output ratio, the thickness of the superconducting layer of the REBCO tape produced by the current industry is usually not more than 3 microns, which seriously restricts the current-carrying capacity of the REBCO film. SUMMARY

[0003] The purpose of the application is to provide a preparation method of a REBCO superconducting thick film to solve the problems existing in the prior art.

[0004] To achieve the above purpose, the application provides the following solutions:

[0005] One of the technical solutions of the application is a preparation method of a REBCO superconducting thick film, comprising the following steps:

[0006] The REBCO layer is deposited on the base tape using a superconducting layer deposition method, then the auxiliary polishing layer is deposited, and then the rotating polishing is performed by adding the cleaning liquid to obtain the REBCO layer with a smooth surface. After that, the steps of depositing the REBCO layer, depositing the auxiliary polishing layer and rotating polishing are repeated on the REBCO layer with a smooth surface to obtain the REBCO superconducting thick film.

[0007] After the REBCO layer is deposited on the base tape and then the auxiliary polishing layer is deposited, the rotating polishing is performed, so that the REBCO layer with extremely high surface smoothness can be obtained. Then, the REBCO layer is continuously deposited, so that the problems of microstructure deterioration such as grain and grain boundary coarsening in the superconducting layer, increase in surface roughness and microporosity, growth of a-axis oriented grains and increase in residual tensile stress can be solved, and the technical effect that the critical current (I c ) of the REBCO tape increases with the increase of the thickness of the superconducting layer is realized.

[0008] Further, the thickness of each deposited REBCO layer is 500-1000 nm;

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

[0010] Further, the thickness of the auxiliary polishing layer is 2-10 nm;

[0011] The auxiliary polishing layer is in amorphous or nanocrystalline form.

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

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

[0014] Further, the material of the auxiliary polishing layer comprises CeO2 or Al2O3.

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

[0016] Further, the rotary polishing specifically comprises: rotating the auxiliary polishing layer towards the polishing cloth and applying a force of 0.1-5 N for rotary polishing until the surface root mean square roughness (R q ) <10 nm, and adding a cleaning liquid for cleaning during the polishing process, the cleaning liquid comprising ethanol, ethylene glycol or propylene glycol.

[0017] A force greater than 5 N used in the rotary polishing will result in excessive wear and poor planarization, and a force less than 0.1 N will not achieve polishing effect.

[0018] The rotary 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, silk polishing cloth or flocked polishing cloth.

[0020] A rotary polishing speed greater than 200 rpm will result in excessive wear, poor planarization, and will generate a large amount of heat affecting the superconducting layer, and a rotary polishing speed less than 50 rpm will not achieve polishing effect; a rotary polishing time greater than 5 min will result in excessive wear and poor planarization, and a rotary polishing time less than 1 min will not achieve polishing effect.

[0021] Currently, the preparation of REBCO thick film is basically by a multiple deposition method, and the thick film J cThe main reason for the decrease with thickness is that the surface structure deteriorates with the increase of thickness, which makes it difficult for the subsequent deposition of REBCO to form a biaxially textured REBCO phase by epitaxy. Due to the effect of weak connection of grain boundaries, these formed RECBO phases do not have the function of transmitting current, so removing the surface deterioration layer can help grow superconducting thick films.

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

[0023] Further, the REBCO layer includes a doped or undoped REBa2Cu3O 7-δ layer;

[0024] The doped components include BaMO3, Ba2(RE,Y)NO6, SiO2, BaCuO2, or non-superconducting phase rare earth oxide RE2O3, etc.

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

[0026] RE is selected from one or more of 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] The above REBCO layer provided by the application can realize the preparation of REBCO superconducting thick film by the method of the application, and realize I c Linearly increases with thickness, and improves the current carrying capacity of the tape.

[0030] Further, the base band is a metal base band coated with a single layer or multiple layers of oxide buffer layer;

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

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

[0033] The metal base strip coated with single or multi-layer oxide buffer layer can prevent oxygen diffusion to the base strip, form biaxially textured REBCO with no weak connection, and match the lattice of the base strip with REBCO when the REBCO superconducting thick film is prepared.

[0034] The second technical solution of the present application is the REBCO superconducting thick film prepared by the preparation method.

[0035] The present application has the following technical effects:

[0036] The multiple deposition method of the present application can make the thickness of the REBCO superconducting layer ≥4 μm, and the I c Linearly increases (i.e. c Without obvious decrease with the increase of thickness.

[0037] The method of the present application is a method for growing superconducting film by surface treatment of superconducting layer, which can realize I c Linearly increases with the thickness, and improves the current carrying capacity of the strip. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor on the basis of these drawings.

[0039] Figure 1 The atomic force microscope photo of the amorphous CeO2 surface polishing layer prepared for the embodiment 1 of the present application;

[0040] Figure 2 The I c Changes of the EuBCO films with different thicknesses prepared for the embodiment 1 of the present application. DETAILED DESCRIPTION

[0041] Now, various exemplary embodiments of the present application will be described in detail, which should not be considered as limiting the present application, but should be understood as a more detailed description of some aspects, characteristics and embodiments of the present application.

[0042] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. Additionally, for a range of values of, for example, concentrations, solvent amounts, and the like, it is to be understood that each intervening value, to the upper and lower limits of the ranges is also specifically disclosed. Each smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of these smaller ranges can independently be included or excluded in the range, and are also encompassed by the application, subject to any specifically excluded limit in the stated

[0043] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned herein are incorporated by reference to disclose and describe in detail the methods and / or materials which are related to the present application. In the case of conflict between the present specification and any document incorporated by reference, the present specification will control.

[0044] Many modifications and variations of the present application described in the specification are possible without departing from the scope or spirit of the application. Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples are illustrative only.

[0045] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", "contains", "containing", or variations thereof, are intended to be open-ended terms that mean inclusion, but not limited to, the listed material or step.

[0046] It is to be noted that the present application is not limited by what has been particularly shown and described hereinabove.

[0047] Deposition of REBCO films on the baseband in the present application uses the routine methods of those skilled in the art, as an example:

[0048] 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.

[0049] 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.

[0050] 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 and transport it to the substrate to realize thin film deposition in vacuum. 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. The process is a typical ex situ method, which can produce REBCO superconducting tapes at a relatively fast speed (120 meters / hour) and accurately control the element ratio.

[0051] The metal-organic decomposition (MOD) is a method for preparing thin film materials. The method mainly involves coating a metal-organic compound solution on a substrate, and then decomposing it to form an oxide film through heat treatment. The typical process for preparing a REBCO film is to dissolve a carboxylate salt (such as isooctanoate, etc.) that is not sensitive to hydrolysis, a nitrate salt or a β-diketone salt (such as acetylacetone, etc.) in a non-polar solvent (methanol, toluene, etc.) according to a certain stoichiometric ratio to prepare a precursor solution. The precursor solution is coated on the superconducting substrate, and then pyrolysis and sintering are performed to form a composite oxide film. Due to the release of CO2 and H2O during the pyrolysis process, 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 the pyrolysis process, which may cause the film to crack. The MOD method for REBCO film deposition can be divided into two types: trifluoroacetate metal-organic salt deposition (TFA-MOD) and fluorine-free metal-organic salt deposition (FF-MOD) according to the metal salt used.

[0052] For example, the REBCO superconducting thick film prepared in the present application can be a 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] Exemplarily, the film layer in the REBCO superconducting thick film prepared in the application can be 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, 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] Exemplarily, the doping amount of BaMO3 is 0-30 mole percent and is not 0; wherein M is selected from one or more of Zr, Hf, Sn and Ce.

[0055] Exemplarily, the film layer in the REBCO superconducting thick film prepared in the application can be 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-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] Exemplarily, the doping amount of Ba2(RE,Y)NO6 is 0-30 mole percent and is not 0; wherein RE is selected from one or more of rare earth elements; and N is selected from Nb and / or Ta.

[0057] Exemplarily, the metal base band used in the application is a nickel-based flexible metal base band coated with a single-layer MgO buffer layer, a copper-based flexible metal base band coated with a single-layer MgO buffer layer, a nickel-based flexible metal base band coated with a multi-layer oxide buffer layer, or a copper-based flexible metal base band coated with a multi-layer oxide buffer layer.

[0058] Exemplarily, the multi-layer oxide buffer layer can be one of CeO2 / YSZ / Y2O3 three-layer oxide buffer layer (the thickness of each layer can refer to the prior art), MgO single-layer oxide buffer layer, LaMnO3 / MgO / Y2O3 / Al2O3 four-layer oxide buffer layer (the thickness of each layer can refer to the prior art), CeO2 / LaMnO3 / MgO / Y2O3 / Al2O3 five-layer oxide buffer layer (the thickness of each layer can refer to the prior art), and 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 base band and the nickel-based flexible metal base band is 30-100 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] Exemplarily, the preparation method of the REBCO superconducting thick film is any one of the following methods:

[0061] Method 1: using a pulse laser deposition method (PLD) to deposit a 1 μm-thick EuBa2Cu3O 7-δlayer, then a 2 nm thick CeO2 assist polishing layer is deposited on the surface of the layer, then the assist polishing layer is directed towards a silk polishing cloth (W 0.25-0.5) and a force of 0.1 N is applied, and the polishing is performed at a rotation speed of 50 rpm, and ethanol cleaning solution is added during the polishing, and after 1 min of polishing, a YBa2Cu3O 7-δ layer with a surface root mean square roughness (R q ) < 10 nm is obtained. A 500 nm thick YBa2Cu3O 7-δ layer is deposited on the polished YBa2Cu3O 7-δ layer, and a 2 nm thick CeO2 assist polishing layer is again deposited and polishing is performed, and this is repeated to obtain a YBa2Cu3O 7-δ superconducting thick film (i.e., REBCO superconducting thick film).

[0062] Method 2, using a metal organic chemical vapor deposition method (MOCVD) to deposit a 500 nm thick YBa2Cu3O 7-δ layer on a nickel-based flexible metal base strip coated with a single layer of MgO buffer layer, then a 2 nm thick CeO2 assist polishing layer is deposited on the surface of the layer, then the assist polishing layer is directed towards a silk polishing cloth (W 0.25-0.5) and a force of 0.1 N is applied, and the polishing is performed at a rotation speed of 50 rpm, and ethanol cleaning solution is added during the polishing, and after 1 min of polishing, a YBa2Cu3O 7-δ layer with a surface root mean square roughness (R q ) < 10 nm is obtained. A 500 nm thick YBa2Cu3O 7-δ layer is deposited on the polished YBa2Cu3O 7-δ layer, and a 2 nm thick CeO2 assist polishing layer is again deposited and polishing is performed, and this is repeated to obtain a YBa2Cu3O 7-δ superconducting thick film (i.e., REBCO superconducting thick film).

[0063] Method 3, using a pulsed laser deposition method (PLD) to deposit a 1 μm thick GdBa2Cu3O 7-δ layer on a copper-based flexible metal base strip (commercial product) coated with a single layer of MgO buffer layer, then a 2 nm thick CeO2 assist polishing layer is deposited on the surface of the layer, then the assist polishing layer is directed towards a silk polishing cloth (W 0.25-0.5) and a force of 0.1 N is applied, and the polishing is performed at a rotation speed of 50 rpm, and ethanol cleaning solution is added during the polishing, and after 1 min of polishing, a YBa2Cu3O 7-δ layer with a surface root mean square roughness (R q<10 nm. After polishing the Y 7-δ GdBa2Cu3O 7-δ layer, a 2 nm thick CeO2 assist polishing layer was deposited again and polishing was performed, and this was repeated to obtain a GdBa2Cu3O 7-δ superconducting thick film (i.e., REBCO superconducting thick film).

[0064] Method 4, using a pulsed laser deposition method (PLD) to deposit a 1 μm thick Y x Gd 1-x Ba2Cu3O 7-δ layer, a 2 nm thick CeO2 assist polishing layer was deposited on the surface thereof, and then the assist polishing layer was directed toward a silk polishing cloth (W 0.25-0.5) and polishing was performed at a rotation speed of 50 rpm with a force of 0.1 N applied, with ethanol cleaning solution added during polishing, and a surface-finished Y x Gd 1- x Ba2Cu3O 7-δ layer, a 2 nm thick CeO2 assist polishing layer was deposited on the surface thereof, and then the assist polishing layer was directed toward a silk polishing cloth (W 0.25-0.5) and polishing was performed at a rotation speed of 50 rpm with a force of 0.1 N applied, with ethanol cleaning solution added during polishing, and a surface-finished Y q <10 nm. After polishing the Y x Gd 1-x Ba2Cu3O 7-δ layer, a 2 nm thick CeO2 assist polishing layer was deposited again and polishing was performed, and this was repeated to obtain a Y x Gd 1-x Ba2Cu3O 7-δ layer, a 2 nm thick CeO2 assist polishing layer was deposited again and polishing was performed, and this was repeated to obtain a Y x Gd 1-x Ba2Cu3O 7-δ superconducting thick film (i.e., REBCO superconducting thick film).

[0065] Method 5, using a pulsed laser deposition method (PLD) to deposit a 500 nm thick DyBa2Cu3O 7-δ layer, a 2 nm thick CeO2 assist polishing layer was deposited on the surface thereof, and then the assist polishing layer was directed toward a silk polishing cloth (W 0.25-0.5) and polishing was performed at a rotation speed of 50 rpm with a force of 0.1 N applied, with ethanol cleaning solution added during polishing, and a surface-finished DyBa2Cu3O 7-δ layer, a 2 nm thick CeO2 assist polishing layer was deposited on the surface thereof, and then the assist polishing layer was directed toward a silk polishing cloth (W 0.25-0.5) and polishing was performed at a rotation speed of 50 rpm with a force of 0.1 N applied, with ethanol cleaning solution added during polishing, and a surface-finished DyBa2Cu3O q <10 nm. After polishing the DyBa2Cu3O7-δ A 500nm thick layer of DyBa2Cu3O 7-δ A 2nm thick layer of CeO2 assist polishing layer was deposited on the layer again and polishing was performed, and the process was repeated to obtain a DyBa2Cu3O 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 by the same method, and can achieve I c Technical effect of linear increase with thickness.

[0067] The room temperature referred to in the embodiments of the present application is 20-30℃.

[0068] Embodiment 1

[0069] A method for preparing a REBCO superconducting thick film:

[0070] (1) A 1μm thick layer of BaZrO3 doped (BaZrO3 doping amount is 3mol%) EuBa2Cu3O 7-δ layer (i.e. EuBCO) was deposited on a CeO2 / LaMnO3 / MgO / Y2O3 / Al2O3 / C276 hastelloy metal substrate using a pulsed laser deposition method (PLD), and a 2nm thick amorphous CeO2 assist polishing layer was deposited on the surface of the layer at room temperature, then the assist polishing layer was placed towards the polishing cloth, and a force of 0.1N was applied to perform rotary polishing at a speed of 50rpm, and ethanol cleaning solution was added during the polishing process, and after 1min of polishing, a EuBCO layer with a smooth surface was obtained, with a root mean square roughness (R q ) of 5.0±0.02nm, and the thickness of the superconducting layer after polishing was about 0.95μm.

[0071] The atomic force microscope photo of the amorphous CeO2 assist polishing layer is shown in Figure 1 .

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

[0073] The I c changes of EuBCO films with different thicknesses obtained by different deposition times at 77K self-field are shown in 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 layer of 10 nm thick nanocrystalline CeO2 auxiliary polishing layer is deposited on the surface of the YBCO layer at room temperature, then the auxiliary polishing layer is directed towards the silk polishing cloth, and a force of 5 N is applied for rotary polishing at a speed of 200 rpm, with the addition of propylene glycol cleaning solution during polishing. After 1 min of polishing, the polishing cloth is replaced with a silk polishing cloth, a force of 0.5 N is applied for rotary polishing at a speed of 200 rpm, with the addition of ethylene glycol cleaning solution during polishing. After 4 min of polishing, a YBCO layer with a smooth surface is obtained, with a surface root mean square roughness (R q ) of 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 again on the surface thereof and polished, and this is repeated to obtain a YBCO superconducting thick film (i.e., REBCO superconducting thick film) with a thickness of 4.6 μm, I c of which can reach 900 A.

[0084] wherein a 1 μm thick YBa2Cu3O 7-δ layer (i.e., YBCO) is deposited once c increases by about 195 A, and the I c of the 4.6 μm superconducting film increases linearly with thickness.

[0085] Example 4

[0086] A method for preparing a REBCO superconducting thick film:

[0087] (1) A 500 μm thick BaHfO3 doped (BaHfO3 doping amount is 3.5 mol%) EuBa2Cu3O 7-δ layer (i.e., EuBCO) is deposited on a MgO / Cu metal base strip using a metal chemical vapor deposition method (MOCVD), a 2 nm thick amorphous CeO2 auxiliary polishing layer is deposited on the surface thereof at room temperature, then the auxiliary polishing layer is directed towards the silk polishing cloth, and a force of 0.1 N is applied for rotary polishing at a speed of 50 rpm, with the addition of ethanol cleaning solution during polishing. After 1 min of polishing, a EuBCO layer with a smooth surface is obtained, with a surface root mean square roughness (R q ) of 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 again on the surface thereof and polished, and this is repeated to obtain a EuBCO superconducting thick film (i.e., REBCO superconducting thick film) with a thickness of about 4.3 μm, I c of which can reach 822 A.

[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 for preparing a REBCO superconducting thick film, characterized in that, Includes the following steps: 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.

2. The preparation method according to claim 1, characterized in that, The thickness of the REBCO layer deposited each time is 500~1000 nm; And / or, the thickness of the REBCO superconducting thick film is ≥4μm.

3. The preparation method according to claim 1, characterized in that, The thickness of the auxiliary polishing layer is 2~10nm; And / or, the auxiliary polishing layer is in an amorphous or nanocrystalline morphology; And / or, the deposition temperature of the auxiliary polishing layer is room temperature.

4. The preparation method according to claim 1, characterized in that, The material of the auxiliary polishing layer includes CeO2 or Al2O3.

5. The preparation method according to claim 1, characterized in that, The rotary polishing specifically includes: facing the auxiliary polishing layer toward the polishing cloth and applying a force of 0.1~5N to perform rotary polishing until the root mean square roughness of the surface is <10nm, and using a cleaning solution during the rotary polishing process; And / or, the rotational polishing speed is 50~200 rpm, and the time is 1~5 min; And / or, the cleaning solution includes ethanol, ethylene glycol or propylene glycol; And / or, the polishing cloth is selected from silk polishing cloth, cashmere polishing cloth, velvet polishing cloth or flocked polishing cloth.

6. The preparation method according to claim 1, characterized in that, The superconducting layer deposition methods include pulsed laser deposition, metal-organic chemical vapor deposition, reactive electron beam co-evaporation-deposition reaction, or metal-organic salt decomposition.

7. The preparation method according to claim 1, characterized in that, The REBCO layer comprises doped or undoped REBa2Cu3O 7-δ layer; The doped components include BaMO3, Ba2(RE,Y)NO6, SiO2, BaCuO2, or 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 rare earth elements; N is selected from Nb and / or Ta; And / or, the rare earth elements are Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.

8. The preparation method according to claim 1, characterized in that, The baseband is a metal baseband coated with a single or multiple oxide buffer layer; And / or, the metal substrate includes a nickel-based or copper-based flexible metal substrate.

9. The preparation method according to claim 8, characterized in that, The structure of the oxide buffer layer includes one of CeO2 / YSZ / Y2O3, MgO, LaMnO3 / MgO / Y2O3 / Al2O3, CeO2 / LaMnO3 / MgO / Y2O3 / Al2O3, or CeO2 / MgO / Y2O3 / Al2O3.

10. A REBCO superconducting thick film prepared by the preparation method according to any one of claims 1 to 9.

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