A method for preparing high-temperature superconducting thin film based on hetero-site element doping

Abstract

The application provides a preparation method of a high-temperature superconducting thin film based on ex situ element doping, and mainly solves the problem that in the process of preparing a YBCO superconducting thin film by a TFA-MOD method, with the increase of the added amount of the doping element, a large number of a axes appear, thereby affecting the current transmission of the YBCO thin film. A layer of undoped layer is added below the doping layer as a seed layer, so as to serve as a growth template of the doping layer and induce the c-axis growth of the doping layer. By using the preparation method, the added amount of the doping element in the obtained YBCO superconducting thin film can be increased to 10%, and meanwhile, the c-axis texture can be maintained.

Description

Technical Field

[0001] This invention belongs to the field of superconducting material design and processing technology, specifically relating to a method for preparing high-temperature superconducting thin films based on ex-situ elemental doping. Background Technology

[0002] Yttrium barium copper oxide (YBa2Cu3O) 7-δ High-temperature superconducting thin films (hereinafter referred to as YBCO) have always been a research hotspot in the field of practical superconductivity due to their excellent performance and potential price advantages. However, the practical application of YBCO superconducting thin films still faces two major problems: First, the existence of Josephson-type weak connections between grain boundaries in YBCO superconducting thin films results in different current-carrying capacities between the superconductor grain interior and grain boundaries, limiting the improvement of critical current density; second, the relatively low critical current density under an applied magnetic field also limits the application of YBCO superconducting thin films in many fields. Therefore, it is essential to improve their on-field performance.

[0003] To improve the electrical transport performance of YBCO superconducting thin films under an applied magnetic field, researchers have introduced magnetic flux pinning centers within the YBCO superconducting thin films using artificial means to pin the movement of magnetic flux vortex lines. Methods for introducing artificial pinning centers include: (1) irradiating high-temperature YBCO superconductors with high-energy heavy particle beams to generate c-axis aligned line defects; (2) depositing a layer of nanoparticles on a metal substrate followed by epitaxial growth of YBCO; and (3) adding second-phase nanoparticles, including BaMO3 (M = Zr, Hf, Sn, etc.) perovskite structure compounds. Currently, adding second-phase nanoparticles is an effective method. However, regardless of whether in-situ or ex-situ methods are used to add second-phase nanoparticles, it directly affects the preparation and growth of the YBCO thin film, resulting in more a-axis pins that affect current transport. Therefore, it is necessary to adjust the process parameters in a timely manner.

[0004] In the preparation of YBCO superconducting thin film tapes using trifluoroacetic acid-organic metal deposition (TFA-MOD), a common method to improve their electrical transport performance under an applied magnetic field is to add elements such as Zr, Hf, and Sn to form BaMO3 (M = Zr, Hf, Sn, etc.) in the YBCO film. However, with increasing element doping amounts, the texture of the YBCO superconducting film usually changes, resulting in a large number of α-axis doping. The presence of α-axis doping affects the current transport of the YBCO film. Therefore, the addition amount of these elements is usually low, generally around 8%. Summary of the Invention

[0005] The technical problem this invention aims to solve is to address the shortcomings of the prior art by providing a method for preparing high-temperature superconducting thin films based on ex-situ elemental doping. In the TFA-MOD method for preparing YBCO superconducting thin films, this invention innovatively adds an undoped layer as a seed layer beneath the doped layer, serving as a growth template for the doped layer and inducing c-axis growth. This allows for increasing the amount of dopant added to 10% while maintaining good c-axis texture. This invention also effectively solves the problem that as the amount of dopant added increases, a large amount of a-axis appears, thus affecting the current transport of YBCO thin films.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing high-temperature superconducting thin films based on ex-situ elemental doping, characterized in that the method includes the following steps:

[0007] S1. Prepare YBCO seed layer precursor solution, including the following steps:

[0008] S101. Dissolve yttrium acetate and barium acetate in deionized water, stir thoroughly at 40℃~60℃ until dissolved, add trifluoroacetic acid, and react thoroughly at 40℃~60℃ for 1h~2h to obtain precursor solution A;

[0009] S102. Dissolve copper acetate in deionized water, add propionic acid, and stir in a water bath at 70℃~90℃ for 1h~2h to obtain precursor solution B;

[0010] S103. Mix precursor solution A and precursor solution B, and distill under reduced pressure at 60°C to remove water. Add anhydrous methanol to the residue to dissolve it, and distill under normal pressure at 65°C. Repeat this process 3 times. Finally, dissolve it with anhydrous methanol to obtain YBCO seed layer precursor solution.

[0011] S2. Preparation of YBCO doped layer precursor solution, including the following steps:

[0012] S201. Dissolve yttrium acetate, barium acetate and the organometallic salt of the doped element in deionized water. After stirring and dissolving thoroughly at 40℃~60℃, add trifluoroacetic acid and react thoroughly at 40℃~60℃ for 1h~2h to obtain precursor solution C.

[0013] S202. Dissolve copper acetate in deionized water, add propionic acid, and stir in a water bath at 70℃~90℃ for 1h~2h to obtain precursor solution D;

[0014] S203, mixed precursor solution C and precursor solution D, were distilled under reduced pressure at 60℃ to remove water; anhydrous methanol was added to the residue for dissolution, and the mixture was distilled under normal pressure at 65℃. This process was repeated 3 times, and finally dissolved in anhydrous methanol to obtain the YBCO doped layer precursor solution.

[0015] S3. Coating: The YBCO seed layer precursor solution obtained in S1 and the YBCO doped layer precursor solution obtained in S2 are sequentially coated onto the growth substrate to obtain the precursor film.

[0016] S4. Low-temperature pyrolysis treatment: The precursor membrane obtained in S3 is subjected to low-temperature pyrolysis treatment by introducing wet oxygen and heating it to 240°C at a rate of 5°C / min, and then heating it to 500°C at a rate of 3°C / min and holding it at that temperature for 5 min to obtain a pyrolysis membrane; the wet oxygen is obtained by passing oxygen at a flow rate of 0.2 L / min through 20°C deionized water.

[0017] S5. High-temperature treatment: The pyrolysis film obtained in S4 is subjected to high-temperature crystallization. The temperature is increased to 780℃~820℃ at a rate of 25℃ / min, the oxygen partial pressure is 150ppm~300ppm, nitrogen is used as the filling gas, the water vapor partial pressure is 4.2%~5.6%, and the temperature is kept constant for 2h to obtain YBCO film.

[0018] S6. Oxygen absorption treatment: The YBCO film obtained in S5 is kept at 400℃~500℃ for 1 hour in an oxygen atmosphere, and finally cooled to room temperature to obtain a high-temperature superconducting film based on ex-situ element doping.

[0019] Preferably, the molar ratio of yttrium acetate to trifluoroacetic acid in S1 and S2 is 1:0.84; and the molar ratio of yttrium acetate, barium acetate, and copper acetate is 1:2:3.

[0020] Preferably, the total cation concentration of the YBCO seed layer precursor solution in S103 is 1.5 mol / L.

[0021] Preferably, the doping element in S201 includes hafnium (Hf), zirconium (Zr), or tin (Sn); the molar ratio of yttrium acetate to the organometallic salt of the doping element is 1:(0.01~0.1), which means that the amount of doping element added is 1%~10%.

[0022] Preferably, the total cation concentration of the YBCO doped layer precursor solution in S203 is 2.5 mol / L.

[0023] Preferably, the coating method described in S3 includes spin coating, lift coating, or cast coating.

[0024] Preferably, the substrate used for coating in S3 is a metal substrate, LaMnO3 / MgO / Al2O3 / Y2O3 / Hastalloy, LaAlO3, or SrTiO3 single crystal substrate.

[0025] Preferably, the thickness of the high-temperature superconducting thin film in S6 is 0.6 to 1.2 μm.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] 1. This invention discloses a method for preparing high-temperature superconducting thin films based on ex-situ elemental doping. In the process of preparing YBCO superconducting thin films by the TFA-MOD method, an undoped layer is first added below the doped layer as a seed layer. Both the doped layer and the seed layer are initially wet films. Subsequently, the seed layer grows together with the doped layer, which is simple to operate.

[0028] 2. The preparation method of the present invention uses the seed layer as a growth template for the doped layer to induce the c-axis growth of the doped layer, which can increase the amount of dopant added in the YBCO superconducting thin film to 10% while maintaining a good c-axis texture; it effectively solves the problem that as the amount of dopant added increases, the a-axis appears in large quantities, thus affecting the current transport of the YBCO superconducting thin film.

[0029] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. Attached Figure Description

[0030] Figure 1 This is a surface morphology (SEM) image of the high-temperature superconducting thin film prepared in Example 1 (with a seed layer of 10% Hf doping).

[0031] Figure 2 These are XRD comparison images of the high-temperature superconducting thin films prepared in Examples 1 and 2 (with seed layer and 8% Hf doping) and Comparative Example 1 (without seed layer and 8% Hf doping).

[0032] Figure 3 The critical current (Ic) of the high-temperature superconducting thin films prepared in Example 2 and Comparative Example 1 is... c Comparison chart.

[0033] Figure 4 This is a (103)-phi scan of the high-temperature superconducting thin film prepared in Example 2.

[0034] Figure 5 This is a (103)-phi scan of the high-temperature superconducting thin film prepared in Comparative Example 1.

[0035] Figure 6 This is a surface morphology (SEM) image of the high-temperature superconducting thin film prepared in Example 5 (with a seed layer of 10% Zr doping).

[0036] Figure 7 These are XRD comparison images of the high-temperature superconducting thin films prepared in Examples 5 and 6 (with seed layer and 8% Zr doping) and Comparative Example 2 (without seed layer and 8% Zr doping).

[0037] Figure 8 The critical current (Ic) of the high-temperature superconducting thin films prepared in Example 6 and Comparative Example 2 is... c Comparison chart. Detailed Implementation

[0038] Example 1

[0039] This embodiment describes a method for preparing a high-temperature superconducting thin film with a seed layer of 10% Hf doping. The method is as follows:

[0040] S1. Prepare YBCO seed layer precursor solution, including the following steps:

[0041] S101. Dissolve yttrium acetate and barium acetate in deionized water at a molar ratio of 1:2. After stirring and dissolving thoroughly at 40°C, add trifluoroacetic acid at a molar ratio of yttrium acetate to trifluoroacetic acid of 1:0.84. React thoroughly at 40°C for 2 hours to obtain precursor solution A.

[0042] S102. Dissolve copper acetate in deionized water at a molar ratio of yttrium acetate to copper acetate of 1:3, add propionic acid, and stir in a water bath at 70°C for 2 hours to obtain precursor solution B.

[0043] S103. Mix precursor solution A and precursor solution B, and distill under reduced pressure at 60℃ until the water is removed. Dissolve in anhydrous methanol, and distill three times under normal pressure at 65℃. Finally, make up to volume with anhydrous methanol to obtain YBCO seed layer precursor solution with a total cation concentration of 1.5 mol / L.

[0044] S2. Preparation of YBCO doped layer precursor solution, including the following steps:

[0045] S201. Yttrium acetate, barium acetate, and hafnium acetylacetonate are dissolved in deionized water in a molar ratio of 1:2:0.1. After being thoroughly dissolved by stirring at 40°C, trifluoroacetic acid is added in a molar ratio of yttrium acetate to trifluoroacetic acid of 1:0.84. The mixture is then reacted at 40°C for 2 hours to obtain precursor solution C.

[0046] S202. Dissolve copper acetate in deionized water at a molar ratio of yttrium acetate to copper acetate of 1:3, add propionic acid, and stir in a water bath at 70°C for 2 hours to obtain precursor solution D.

[0047] S203, mixed precursor solution C and precursor solution D, were distilled under reduced pressure at 60℃ to remove water; then dissolved in anhydrous methanol and distilled three times under normal pressure at 65℃. Finally, the solution was brought to a final volume with anhydrous methanol to obtain a YBCO doped layer precursor solution with a total cation concentration of 2.5 mol / L.

[0048] S3. Coating: The YBCO seed layer precursor solution obtained in S1 and the YBCO doped layer precursor solution obtained in S2 are sequentially coated onto the LaMnO3 / MgO / Al2O3 / Y2O3 / Hastalloy substrate using spin coating to obtain the precursor film; the coating rotation speed is 3000 r / min and the coating time is 2 min.

[0049] The LaMnO3 / MgO / Al2O3 / Y2O3 / Hastalloy substrate was provided by Shanghai Shangchuang Superconducting Technology Co., Ltd.

[0050] S4. Pyrolysis treatment: The precursor membrane obtained in S3 is subjected to low-temperature pyrolysis treatment. Wet oxygen is introduced through 20℃ deionized water at a gas flow rate of 0.2L / min. The temperature is increased to 240℃ at a rate of 5℃ / min, and then increased to 500℃ at a rate of 3℃ / min. The temperature is held for 5min to obtain the pyrolysis membrane.

[0051] S5. Crystallization treatment: The pyrolysis film prepared in S4 is subjected to high-temperature crystallization by heating to 780℃ at a rate of 25℃ / min and holding for 120min to obtain a YBCO film; a wet nitrogen-oxygen mixture is introduced for the first 90min, with an oxygen partial pressure of 150ppm and a water vapor partial pressure of 5.6%; and a dry nitrogen-oxygen mixture is introduced for the last 30min, with an oxygen partial pressure of 150ppm.

[0052] S6. Oxygen absorption treatment: The YBCO thin film obtained in S5 is kept at 450℃ for 1 hour in an oxygen atmosphere, and finally cooled to room temperature to obtain a 10% Hf-doped YBCO superconducting thin film.

[0053] Figure 1 This is a surface morphology (SEM) image of the high-temperature superconducting thin film prepared in this embodiment. As can be seen from the figure, the surface of the Hf-doped film is relatively dense and has a small number of a-axis. This is due to the large difference between the heterophase formed by Hf and the YBCO matrix.

[0054] In this embodiment, the thickness of the YBCO superconducting thin film is 0.8 μm, and the critical current Ic is... c It is 180A.

[0055] Example 2

[0056] This embodiment describes a method for preparing a high-temperature superconducting thin film with 8% Hf doping in a seed layer. The method is the same as in Example 1, except that the molar ratio of yttrium acetate, barium acetate, and hafnium acetylacetonate in S201 is 1:2:0.08. The prepared thin film has a thickness of 0.8 μm and a critical current I0. c It is 200A.

[0057] Comparative Example 1

[0058] A high-temperature superconducting thin film with 8% Hf doping and no seed layer was prepared using the same method as in Example 1, except that: (1) the preparation of the seed layer precursor solution in S1 and the coating of the seed layer precursor solution in S3 were removed; (2) the molar ratio of yttrium acetate, barium acetate, and hafnium acetylacetone in S201 was 1:2:0.08. The resulting YBCO superconducting thin film had a thickness of 0.6 μm and a critical current Ic. c It is 150A.

[0059] Figure 2 These are XRD comparison images of the high-temperature superconducting thin films prepared in Examples 1 and 2 and Comparative Example 1. As can be seen from the figures, the a-axis of the YBCO superconducting thin film prepared by the Hf element doping method is significantly reduced after the seed layer is introduced. This is related to the heterophase formed by element doping and the lattice mismatch of the YBCO matrix.

[0060] Figure 3 The critical current (Ic) of the high-temperature superconducting thin films prepared in Example 2 and Comparative Example 1 is... c (Comparison diagram.) As shown in the diagram, the critical current Ic of the YBCO superconducting thin film with an 8% Hf seed layer is... c (200A) is significantly higher than the critical current I of 8% Hf-doped YBCO superconducting thin films without a seed layer. c (150A).

[0061] Figure 4 and Figure 5 The figures show the (103)-phi scans of the high-temperature superconducting thin films prepared in Example 2 and Comparative Example 1, respectively. As can be seen from the figures, the average in-plane half-width at half-maximum (WHaV) of the YBCO superconducting thin film with an 8% Hf seed layer is 2.2°, while the average WHaV of the YBCO superconducting thin film without an 8% Hf seed layer is 2.7°.

[0062] Example 3

[0063] This embodiment describes a method for preparing a high-temperature superconducting thin film with a seed layer of 5% Hf doping. The method is the same as in Example 1, except that: (1) the molar ratio of yttrium acetate, barium acetate, and hafnium acetylacetonate in S201 is 1:2:0.05; (2) in S3, the YBCO seed layer precursor solution obtained in S1 and the YBCO doping layer precursor solution obtained in S2 are sequentially coated onto an Ag metal substrate using a casting method; the thickness of the obtained YBCO superconducting thin film is 0.8 μm, and the critical current Ic is... c It is 220A.

[0064] Example 4

[0065] This embodiment describes a method for preparing a high-temperature superconducting thin film with a seed layer of 1% Hf doping. The method is the same as in Example 1, except that the molar ratio of yttrium acetate, barium acetate, and hafnium acetylacetonate in S201 is 1:2:0.01; the resulting YBCO superconducting thin film has a thickness of 0.8 μm and a critical current I0. c It is 180A.

[0066] Example 5

[0067] This embodiment describes a method for preparing a high-temperature superconducting thin film with a seed layer of 10% Zr doping. The method is as follows:

[0068] S1. Prepare YBCO seed layer precursor solution, including the following steps:

[0069] S101. Dissolve yttrium acetate and barium acetate in deionized water at a molar ratio of 1:2. After stirring and dissolving thoroughly at 60°C, add trifluoroacetic acid at a molar ratio of yttrium acetate to trifluoroacetic acid of 1:0.84. React thoroughly at 60°C for 1 hour to obtain precursor solution A.

[0070] S102. Dissolve copper acetate in deionized water at a molar ratio of yttrium acetate to copper acetate of 1:3, add propionic acid, and stir in a water bath at 90°C for 1 hour to obtain precursor solution B.

[0071] S103. Mix precursor solution A and precursor solution B, and distill under reduced pressure at 60℃ until the water is removed. Dissolve in anhydrous methanol, and distill three times under normal pressure at 65℃. Finally, make up to volume with anhydrous methanol to obtain YBCO seed layer precursor solution with a total cation concentration of 1.5 mol / L.

[0072] S2. Preparation of YBCO doped layer precursor solution, including the following steps:

[0073] S201. Yttrium acetate, barium acetate, and zirconium acetylacetonate are dissolved in deionized water in a molar ratio of 1:2:0.1. After being thoroughly dissolved by stirring at 60°C, trifluoroacetic acid is added in a molar ratio of yttrium acetate to trifluoroacetic acid of 1:0.84. The mixture is then reacted at 60°C for 1 hour to obtain precursor solution C.

[0074] S202. Dissolve copper acetate in deionized water at a molar ratio of yttrium acetate to copper acetate of 1:3, add propionic acid, and stir in a water bath at 90°C for 1 hour to obtain precursor solution D.

[0075] S203, mixed precursor solution C and precursor solution D, were distilled under reduced pressure at 60℃ to remove water; then dissolved in anhydrous methanol and distilled three times under normal pressure at 65℃. Finally, the solution was brought to a final volume with anhydrous methanol to obtain a YBCO doped layer precursor solution with a total cation concentration of 2.5 mol / L.

[0076] S3. Coating: The YBCO seed layer precursor solution prepared in S1 and the YBCO doped layer precursor solution prepared in S2 are sequentially coated onto the SrTiO3 substrate using the Czochralski method to obtain the precursor film; the Czochralski speed is 500 μm / s.

[0077] S4. Pyrolysis treatment: The precursor membrane obtained in S3 is subjected to low-temperature pyrolysis treatment. Wet oxygen is introduced through 20℃ deionized water at a gas flow rate of 0.2L / min. The temperature is increased to 240℃ at a rate of 5℃ / min, and then increased to 500℃ at a rate of 3℃ / min. The temperature is held for 5min to obtain the pyrolysis membrane.

[0078] S5. Crystallization treatment: The pyrolysis film prepared in S4 is subjected to high-temperature crystallization by heating to 820℃ at a rate of 25℃ / min and holding for 120min to obtain a YBCO film; a wet nitrogen-oxygen mixture is introduced for the first 90min, with an oxygen partial pressure of 300ppm and a water vapor partial pressure of 4.2%; and a dry nitrogen-oxygen mixture is introduced for the last 30min, with an oxygen partial pressure of 300ppm.

[0079] S6. Oxygen absorption treatment: The YBCO thin film obtained in S5 is kept at 500℃ for 1 hour in an oxygen atmosphere, and finally cooled to room temperature to obtain a 10% Zr-doped YBCO superconducting thin film.

[0080] Figure 6 This is a surface morphology (SEM) image of the high-temperature superconducting thin film prepared in this embodiment. As can be seen from the image, the surface of the thin film is relatively dense and there is no obvious a-axis.

[0081] In this embodiment, the thickness of the YBCO superconducting thin film is 0.8 μm, and the critical current Ic is... c It is 230A.

[0082] Example 6

[0083] This embodiment describes the preparation method of a high-temperature superconducting thin film with 8% Zr doping in the seed layer. The method is the same as in Example 5, except that the molar ratio of yttrium acetate, barium acetate, and zirconium acetylacetonate in S201 is 1:2:0.08. The prepared thin film has a thickness of 0.8 μm and a critical current I0. c It is 250A.

[0084] Comparative Example 2

[0085] A high-temperature superconducting thin film with 8% Zr doping and no seed layer was prepared using the same method as in Example 5, except that: (1) the preparation of the seed layer precursor solution in S1 and the coating of the seed layer precursor solution in S3 were removed; (2) the molar ratio of yttrium acetate, barium acetate, and zirconium acetylacetone in S201 was 1:2:0.08. The resulting YBCO superconducting thin film had a thickness of 0.8 μm and a critical current Ic. c It is 190A.

[0086] Figure 7 These are XRD comparison images of the high-temperature superconducting thin films prepared in Examples 5 and 6 and Comparative Example 2. As can be seen from the figures, the heterophase formed by Zr doping has a good lattice match with the YBCO matrix. Under the induction of the seed layer, even when the addition amount is increased to 10%, the a-axis is not clearly observed.

[0087] Figure 8 The critical current (Ic) of the high-temperature superconducting thin films prepared in Example 6 and Comparative Example 2 is... c (Comparison diagram.) As shown in the diagram, the critical current Ic of the 8% Zr-doped YBCO superconducting thin film with a seed layer is... c (250A) is significantly higher than the critical current I of the 8% Zr-doped YBCO superconducting thin film without a seed layer. c (190A).

[0088] Example 7

[0089] This embodiment describes a method for preparing a high-temperature superconducting thin film with a 10% Sn-doped seed layer. The method is as follows:

[0090] S1. Prepare YBCO seed layer precursor solution, including the following steps:

[0091] S101. Dissolve yttrium acetate and barium acetate in deionized water at a molar ratio of 1:2. After stirring and dissolving thoroughly at 50°C, add trifluoroacetic acid at a molar ratio of yttrium acetate to trifluoroacetic acid of 1:0.84. React thoroughly at 50°C for 1.5 hours to obtain precursor solution A.

[0092] S102. Dissolve copper acetate in deionized water at a molar ratio of yttrium acetate to copper acetate of 1:3, add propionic acid, and stir in an 80°C water bath for 1.5 h to obtain precursor solution B.

[0093] S103. Mix precursor solution A and precursor solution B, and distill under reduced pressure at 60℃ until the water is removed. Dissolve in anhydrous methanol, and distill three times under normal pressure at 65℃. Finally, make up to volume with anhydrous methanol to obtain YBCO seed layer precursor solution with a total cation concentration of 1.5 mol / L.

[0094] S2. Preparation of YBCO doped layer precursor solution, including the following steps:

[0095] S201. Yttrium acetate, barium acetate, and tin acetate are dissolved in deionized water in a molar ratio of 1:2:0.1. After being thoroughly dissolved by stirring at 50°C, trifluoroacetic acid is added in a molar ratio of yttrium acetate to trifluoroacetic acid of 1:0.84. The mixture is then reacted at 50°C for 1.5 hours to obtain precursor solution C.

[0096] S202. Dissolve copper acetate in deionized water at a molar ratio of yttrium acetate to copper acetate of 1:3, add propionic acid, and stir in an 80°C water bath for 1.5 h to obtain precursor solution D.

[0097] S203, mixed precursor solution C and precursor solution D, were distilled under reduced pressure at 60℃ to remove water; then dissolved in anhydrous methanol and distilled three times under normal pressure at 65℃. Finally, the solution was brought to a final volume with anhydrous methanol to obtain a YBCO doped layer precursor solution with a total cation concentration of 2.5 mol / L.

[0098] S3. Coating: The YBCO seed layer precursor solution prepared in S1 and the YBCO doped layer precursor solution prepared in S2 are sequentially coated onto the LaAlO3 substrate using the casting method to obtain the precursor film.

[0099] S4. Pyrolysis treatment: The precursor membrane obtained in S3 is subjected to low-temperature pyrolysis treatment. Wet oxygen is introduced through 20℃ deionized water at a gas flow rate of 0.2L / min. The temperature is increased to 240℃ at a rate of 5℃ / min, and then increased to 500℃ at a rate of 3℃ / min. The temperature is held for 5min to obtain the pyrolysis membrane.

[0100] S5. Crystallization treatment: The pyrolysis film prepared in S4 is subjected to high-temperature crystallization by heating to 800℃ at a rate of 25℃ / min and holding for 120min to obtain a YBCO film; a wet nitrogen-oxygen mixture is introduced for the first 90min, with an oxygen partial pressure of 225ppm and a water vapor partial pressure of 4.9%; and a dry nitrogen-oxygen mixture is introduced for the last 30min, with an oxygen partial pressure of 225ppm.

[0101] S6. Oxygen absorption treatment: The YBCO thin film obtained in S5 is kept at 400℃ for 1 hour in an oxygen atmosphere, and finally cooled to room temperature to obtain a 10% Sn-doped YBCO superconducting thin film.

[0102] In this embodiment, the thickness of the YBCO superconducting thin film is 1.2 μm, and the critical current Ic is... c It is 210A.

[0103] Example 8

[0104] This embodiment describes a method for preparing a high-temperature superconducting thin film with an 8% Sn-doped seed layer. The method is the same as in Example 7, except that the molar ratio of yttrium acetate, barium acetate, and tin acetate in S201 is 1:2:0.08. The prepared thin film has a thickness of 1.0 μm and a critical current I0. c It is 230A.

[0105] Comparative Example 3

[0106] A high-temperature superconducting thin film with 8% Sn doping and no seed layer was prepared using the same method as in Example 7, except that: (1) the preparation of the seed layer precursor solution in S1 and the coating of the seed layer precursor solution in S3 were removed; (2) the molar ratio of yttrium acetate, barium acetate, and tin acetate in S201 was 1:2:0.08. The resulting YBCO superconducting thin film had a thickness of 1.0 μm and a critical current Ic. c It is 200A.

[0107] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing high-temperature superconducting thin films based on ex-situ elemental doping, characterized in that, The method is as follows: S1. Prepare YBCO seed layer precursor solution, including the following steps: S101. Dissolve yttrium acetate and barium acetate in deionized water, stir and dissolve at 40℃~60℃, add trifluoroacetic acid, and react at 40℃~60℃ for 1h~2h to obtain precursor solution A; S102. Dissolve copper acetate in deionized water, add propionic acid, and stir in a water bath at 70℃~90℃ for 1h~2h to obtain precursor solution B; S103. Mix precursor solution A and precursor solution B, and distill under reduced pressure at 60°C to remove water. Add anhydrous methanol to the residue to dissolve it, and distill under normal pressure at 65°C. Repeat this process 3 times. Finally, dissolve it with anhydrous methanol to obtain YBCO seed layer precursor solution. S2. Preparation of YBCO doped layer precursor solution, including the following steps: S201. Dissolve yttrium acetate, barium acetate and the organometallic salt of the doped element in deionized water, stir and dissolve at 40℃~60℃, add trifluoroacetic acid, and react at 40℃~60℃ for 1h~2h to obtain precursor solution C. S202. Dissolve copper acetate in deionized water, add propionic acid, and stir in a water bath at 70℃~90℃ for 1h~2h to obtain precursor solution D; S203, mixed precursor solution C and precursor solution D, were distilled under reduced pressure at 60℃ to remove water; anhydrous methanol was added to the residue for dissolution, and the mixture was distilled under normal pressure at 65℃. This process was repeated 3 times, and finally dissolved in anhydrous methanol to obtain the YBCO doped layer precursor solution. S3. Coating: The YBCO seed layer precursor solution obtained in S1 and the YBCO doped layer precursor solution obtained in S2 are sequentially coated onto the growth substrate to obtain the precursor film. S4. Pyrolysis treatment: The precursor membrane obtained in S3 is subjected to pyrolysis treatment by introducing wet oxygen and heating it to 240°C at a rate of 5°C / min, and then heating it to 500°C at a rate of 3°C / min and holding it at that temperature for 5 min to obtain a pyrolysis membrane; the wet oxygen is obtained by passing oxygen at a flow rate of 0.2 L / min through 20°C deionized water. S5. Crystallization treatment: The pyrolysis film obtained in S4 is subjected to crystallization treatment by heating to 780℃~820℃ at a rate of 25℃ / min, with an oxygen partial pressure of 150ppm~300ppm, using nitrogen as the filling gas, and a water vapor partial pressure of 4.2%~5.6%. After holding at this temperature for 2 hours, a YBCO film is obtained. S6. Oxygen absorption treatment: The YBCO film obtained in S5 is kept at 400℃~500℃ for 1 hour in an oxygen atmosphere, and finally cooled to room temperature to obtain a high-temperature superconducting film based on ex-situ element doping.

2. The method according to claim 1, characterized in that, The molar ratio of yttrium acetate to trifluoroacetic acid in S1 and S2 is 1:0.84; the molar ratio of yttrium acetate, barium acetate, and copper acetate is 1:2:

3.

3. The method according to claim 1, characterized in that, The total cation concentration of the YBCO seed layer precursor solution described in S103 is 1.5 mol / L.

4. The method according to claim 1, characterized in that, The doping element in S201 includes Hf, Zr or Sn, and the molar ratio of yttrium acetate to the organometallic salt of the doping element is 1:(0.01~0.1).

5. The method according to claim 1, characterized in that, The total cation concentration of the YBCO doped layer precursor solution in S203 is 2.5 mol / L.

6. The method according to claim 1, characterized in that, The coating method described in S3 includes spin coating, dip coating, or cast coating.

7. The method according to claim 1, characterized in that, The growth substrate used for coating S3 is LaMnO3 / MgO / Al2O3 / Y2O3 / Hastalloy, a metal substrate, or a LaAlO3 or SrTiO3 single crystal substrate.

8. The method according to claim 1, characterized in that, The thickness of the high-temperature superconducting thin film described in S6 is 0.6–1.2 μm.

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