Preparation method of YBa2Cu3O7-delta superconducting material

Abstract

The invention discloses a preparation method of a YBa2Cu3O7-delta superconducting material, and relates to a preparation method of a superconductor material, which comprises the following steps: dissolving Y2 (CO3) 3, Ba (NO3) 2 and CuSO4. 5H2O in deionized water according to a molar ratio, uniformly stirring, firstly adding citric acid, then adding ethylene glycol, then adding ammonia water to adjust the pH value, carrying out microwave heating and stirring to form sol, carrying out vacuum drying, and grinding into particles, thereby obtaining the YBa2Cu3O7-delta superconducting material. Carrying out gradient sintering in an oxygen atmosphere, and continuously carrying out microwave treatment in the sintering process; and carrying out gradient cooling in an oxygen atmosphere, and carrying out ball milling, screening and drying after cooling. According to the process method, the microwave-assisted low-temperature calcination technology and the sol combustion method are combined, energy consumption is remarkably reduced, the preparation period is obviously shortened, material element distribution is more uniform, the superconductive critical temperature Tc is larger than or equal to 72K, the technical problems that a traditional process is high in high-temperature energy consumption and uneven in component are solved, and the method can be applied to the fields of superconductive power grids, quantum devices and the like on a large scale.

Description

Technical Field

[0001] This invention relates to a method for preparing superconducting materials, and particularly to a YBa2Cu3O 7-δ Methods for preparing superconducting materials. Background Technology

[0002] Since its discovery in 1987, YBa2Cu3O 7-δ Y123, as a representative of second-generation high-temperature copper oxide superconductors, has attracted much attention due to its critical temperature (Tc≈90 K) breaking through the liquid nitrogen temperature range (77 K). Y123's unique layered perovskite structure (consisting of alternating CuO2 superconducting layers and yttrium barium oxide layers) endows it with excellent current-carrying capacity and magnetic field stability, showing great potential in fields such as superconducting cables, high-field magnets, and quantum computing. However, traditional methods for preparing Y123 struggle to achieve a balance between material uniformity, mechanical strength, and cost-effectiveness. Furthermore, its cryogenic operation relies on liquid nitrogen refrigeration systems, resulting in high economic and technological barriers for large-scale applications, which severely limits the widespread use of Y123.

[0003] To address this challenge, researchers both domestically and internationally have made some breakthroughs. For example, Furukawa Electric Corporation of Japan and AMSC Corporation of the United States developed Y123 thin-film wires using single-crystal growth and thin-film technology, achieving a conduction current density (Jc) of 150 MA / cm² under an 18 T magnetic field, setting a world record. MIT has achieved high-frequency applications of Y123 thin films in quantum computing through gradient coupler design. A European team utilized an elemental doping strategy, optimizing the magnetic flux pinning ability of Y123 by doping with rare earth elements such as Gd and Sm, increasing Jc to 5 × 10⁴ A·cm⁻² under a high magnetic field (2 T), significantly higher than traditional Y123 materials. A Polish team successfully prepared porous Y123 foam materials using a polyurethane skeleton combined with top seed infiltration growth (TSIG) topological structure design, and found that a high-density skeleton can promote the formation of the Y123 phase, while a flexible skeleton hinders the transformation of Y211 to Y123, providing a new method for multi-scale structure design. However, the preparation process of Y123 still faces three major challenges: (1) Solid-state reaction method: This method requires multiple calcinations at temperatures above 1000℃ to obtain the product. It is not only energy-intensive, but also prone to producing impurities such as Y2BaCuO5.

[0004] (2) Sol-gel method: This method is relatively complicated. The organic solvent added during the preparation process cannot be effectively removed and is easy to remain in the material, resulting in more impurities in the material.

[0005] (3) Coprecipitation method: This method requires strict control of pH value and reaction conditions, and the product changes with the concentration, resulting in insufficient structural uniformity of the product.

[0006] Therefore, developing low-temperature, efficient, and environmentally friendly preparation processes remains a current research hotspot. Summary of the Invention

[0007] The purpose of this invention is to provide a YBa2Cu3O 7-δ A novel method for preparing superconducting materials is proposed. This method is based on the synergistic optimization of sol-gel combustion and gradient sintering processes. By synthesizing high-purity Y123 superconducting materials at temperatures below 850℃, it solves the technical problems of high energy consumption and uneven composition in traditional processes. This method can be applied on a large scale in fields such as superconducting grids and quantum devices to meet the requirements for superconducting critical temperature and critical current.

[0008] The present invention is achieved through the following technical solutions: This invention discloses a YBa2Cu3O 7-δ The preparation method of superconducting materials, the specific preparation steps are as follows: S1, weigh Y2(CO3)3, Ba(NO3)2 and CuSO4·5H2O according to the molar ratio of 1:4:6, dissolve them in deionized water, stir evenly to form a mixed solution; S2. Weigh citric acid and ethylene glycol separately according to a molar ratio of 1:2. First, add citric acid to the mixed solution in step S1 and stir evenly. Then add ethylene glycol and stir evenly. Then add ammonia water to adjust the pH to 6.5-7.5. Microwave heat and stir to form a sol. S3. The obtained sol is vacuum dried, then cooled to room temperature and ground into particles; S4. The obtained granular material is placed in an oxygen atmosphere for gradient sintering, and microwave treatment is continued during the sintering process. S5. Continue to cool down in an oxygen atmosphere until room temperature is reached; S6. After the cooled sintered material is ball-milled, it is sieved and then dried again.

[0009] In preferred steps S1 and S2, the molar ratio of citric acid to Y2(CO3)3 is 3-5:1.

[0010] In the preferred step S2, the microwave heating conditions are: heating to 80°C under millimeter microwave conditions and stirring for 4 hours.

[0011] As a further embodiment of the present invention, in step S3, the obtained sol is placed in a vacuum drying oven at 40°C for drying for 4-6 hours.

[0012] As a further aspect of the present invention, in step S4, the oxygen atmosphere conditions are: a constant flow rate of 200 mL / min and a pressure of 0.1-0.2 kPa.

[0013] As a further embodiment of the present invention, in step S4, the gradient sintering conditions are: heating to 500°C at a heating rate of 5°C / min for 2-3 hours, and then heating to 780-820°C at a heating rate of 10°C / min for 3-5 hours, with millimeter microwave treatment during the sintering process.

[0014] As a further aspect of the present invention, in step S5, the cooling conditions are: first at 5℃ / min The temperature was cooled to 500°C at a cooling rate of 1°C / min, then cooled to 200°C at a cooling rate of 1°C / min, and then allowed to cool naturally to room temperature.

[0015] As a further embodiment of the present invention, in step S6, the cooled sintered material is taken out and placed in an agate jar at a ball-to-material ratio of 1:2. The jar is then placed in a planetary ball mill for ball milling. The powder is sieved through a 120-mesh sieve and then dried in an oven at 100°C for 12 hours.

[0016] The beneficial effects of this invention are: 1. This invention employs microwave-assisted low-temperature calcination technology, overcoming the thermodynamic barrier of traditional high-temperature solid-state reactions requiring temperatures above 1000℃. It achieves efficient energy transfer through the microwave heating effect, enabling the YBa2Cu3O... 7-δ The main phase formation temperature of (Y123) is reduced by more than 200°C, significantly reducing energy consumption (by up to 40%), while shortening the reaction time to 2 hours (compared to 144 hours in the traditional process), thus improving synthesis efficiency.

[0017] 2. This invention optimizes and constructs a novel sol-gel synthesis pathway through a citric acid-ethylene glycol complexation system: citric acid acts as a multidentate chelating agent, coordinating with Y... 3+ Ba 2+ Cu 2+ It forms stable complexes and inhibits the hydrolysis and aggregation of metal ions; ethylene glycol, as a polymerizing agent, crosslinks with citric acid through esterification to form a three-dimensional network gel, achieving atomic-scale mixing, solving the problem of component segregation in traditional wet milling, and significantly improving the uniformity of element distribution.

[0018] 3. This invention utilizes a dynamic oxygen atmosphere control process and designs a segmented oxygen post-treatment procedure. During the calcination process, a constant flow of 200 mL / min oxygen is introduced. By adjusting the cooling rate (5℃ / min → 1℃ / min), the oxygen content (δ value) in the Y123 crystal path is precisely controlled, promoting the full oxidation of the superconducting active phase (CuO2 surface). Ultimately, the superconducting critical temperature Tc can reach a maximum of 95K (fully superconducting in the liquid nitrogen temperature range), with performance improved by 3-5K compared to traditional processes. Attached Figure Description

[0019] Figure 1 shows YBa2Cu3O from Example 1. 7-δ XRD patterns of superconducting materials; Figure 2 shows YBa2Cu3O from Example 1. 7-δ Scanning electron microscope images of superconducting materials at 200 μm, 100 μm, 20 μm, and 10 μm; Figure 3 shows YBa2Cu3O from Example 1. 7-δ Critical current density curve of superconducting materials; Figure 4 shows YBa2Cu3O from Example 1. 7-δ Diagram of the superconducting critical transition temperature Tc of superconducting materials. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the present invention is not limited to these embodiments. The chemical raw materials used, including Y2(CO3)3, Ba(NO3)2, and CuSO4·5H2O, as well as citric acid and ethylene glycol, are all commercially available. The experimental equipment and testing methods used are all laboratory equipment. Example 1

[0021] YBa2Cu3O 7-δ Preparation of superconducting materials S1. Weigh 0.1 mol of Y2(CO3)3, 0.4 mol of Ba(NO3)2 and 0.6 mol of CuSO4·5H2O, dissolve them in 500 mL of deionized water, stir well to form a mixed solution; S2. Weigh 0.4 mol of citric acid and 0.8 mol of ethylene glycol. First, add the citric acid to the mixed solution in step S1 and stir until homogeneous. Then add the ethylene glycol and stir thoroughly. Add ammonia water to adjust the pH to 6.5-7.5. Stir at 80℃ and under millimeter microwave conditions for 4 hours to form a sol. S3. Place the obtained sol in a vacuum drying oven at 40℃ for 5 hours, and then grind it into particles at room temperature. S4. The obtained powder is placed in a calcining furnace at 800℃ under an oxygen atmosphere for gradient sintering. Microwave treatment is continued during the sintering process. The oxygen atmosphere conditions are: constant flow rate of 200mL / min and pressure of 0.15kPa. The gradient sintering conditions are: heating to 800℃ at a heating rate of 5℃ / min for 4h, and millimeter microwave treatment during the sintering process. S5. Continue to perform gradient cooling in an oxygen atmosphere. The cooling conditions are: first cool to 500℃ at a cooling rate of 5℃ / min, then cool to 200℃ at a cooling rate of 1℃ / min, and then cool naturally to room temperature. S6. Take out the cooled sintered material and put it into an agate jar at a ball-to-material ratio of 1:2. Place it in a planetary ball mill for ball milling. Sieve the powder through a 120-mesh sieve. Then dry the sieved powder in an oven at 100°C for 12 hours.

[0022] XRD analysis of the yttrium barium copper oxide superconductor powder material prepared in Example 1 is shown in Figure 1. It can be seen that the material has high purity and few impurities.

[0023] Scanning electron microscope (SEM) images of the yttrium barium copper oxide superconducting powder material prepared in Example 1 at different scales are shown below. Figure 2 As shown in the figure, the material has an integral particle structure with an average particle size of <30μm, and the material particles also have a porous three-dimensional structure.

[0024] The YBa2Cu3O prepared in Example 1 was analyzed by electrical measurement method. 7-δ The superconducting material was tested, and its superconducting critical temperature Tc and critical current Jc were measured (using the Lepi-system). Figure 3 shows that the prepared superconducting material can achieve a Jc of 5.97 MA / cm² under the conditions of 0 T and 77 K. Figure 4 shows that the superconducting critical transition temperature Tc of this material is 95 K. Example 2

[0025] The difference between Example 2 and Example 1 is that the gradient sintering temperature in step S4 is 780°C. Example 3

[0026] The difference between Example 3 and Example 1 is that the gradient sintering temperature in step S4 is 820°C. Example 4

[0027] The difference between Example 4 and Example 1 is that the amount of citric acid in step S2 is 0.3 mol and the amount of ethylene glycol is 0.6 mol. Example 5

[0028] The difference between Example 5 and Example 1 is that the amount of citric acid in step S2 is 0.5 mol and the amount of ethylene glycol is 1.0 mol.

[0029] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that citric acid is not added in step S2, only ethylene glycol is added.

[0030] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that only citric acid is added in step S2, and ethylene glycol is not added. Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that there is no millimeter-microwave processing in step S2.

[0031] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the powder is calcined in air in step S4.

[0032] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that the gradient sintering temperature in step S4 is 770°C.

[0033] Comparative Example 6 The difference between Comparative Example 6 and Example 1 is that the gradient sintering temperature in step S4 is 830°C.

[0034] Comparative Example 7 The difference between Comparative Example 7 and Example 1 is that no millimeter-microwave processing was performed in step S4.

[0035] Comparative Example 8 YBa2Cu3O was prepared by traditional calcination method. 7-δ superconductor materials S1. Raw material mixing and pre-calcination: Weigh Y2O3, Ba2CO3 and CuO powders according to a molar ratio of 1:2:6, grind and mix them evenly using a wet grinding method, dry the powder in an oven, and then transfer it to a crucible for calcination at 900℃ for 48 hours. S2, Secondary calcination and grinding: The powder obtained from the first calcination is ground, and then calcined again at 900℃ for 48 hours. The above grinding and calcination steps are repeated, and a third calcination is carried out at 900℃ for 48 hours to further promote the reaction and homogenization of the material. S3. Sieving and Drying: The powder that has undergone three calcinations and grindings is sieved through a 120-mesh sieve to remove particles that do not meet the particle size requirements. The sieved powder is then dried in an oven at 100℃ for 12 hours to obtain the final YBa2Cu3O. 7-δ Superconductor materials.

[0036] The superconducting materials prepared in Examples 1-5 and the materials prepared in Comparative Examples 1-8 were tested to obtain their superconducting critical temperature Tc and critical current Jc, as shown in Table 1.

[0037] Table 1. Properties of the superconducting materials prepared in Examples 1-5 and the materials prepared in Comparative Examples 1-8 Superconducting critical temperature Tc / K Critical current Jc / (MA / cm2) Example 1 95 5.97 Example 2 93 4.38 Example 3 93 4.64 Example 4 92 3.21 Example 5 92 3.06 Comparative Example 1 91 1.84 Comparative Example 2 91 1.66 Comparative Example 3 90 1.21 Comparative Example 4 90 0.98 Comparative Example 5 88 0.13 Comparative Example 6 85 0.056 Comparative Example 7 91 1.32 Comparative Example 8 86 0.09 As shown in Table 1, in Example 1 of this invention, after sintering at 800℃ and adding a sol-gel system containing citric acid and ethylene glycol, the superconducting material prepared achieved a superconducting critical temperature of 95K, reaching its optimal state. Examples 2-3 and Comparative Examples 3-7 show that as the gradient sintering temperature increases or decreases, the superconducting critical temperature decreases, and the critical current first increases and then decreases. Furthermore, microwave heating is performed during the gradient sintering process, achieving efficient energy transfer through the microwave heating effect, thereby promoting the critical temperature and conductivity of the superconducting material. Simultaneously, it can also improve the performance of YBa2Cu3O. 7-δ The main phase formation temperature of (Y123) is reduced by more than 200°C, which significantly reduces energy consumption, shortens reaction time, and improves synthesis quality and efficiency.

[0038] As can be seen from Examples 1, 4, 5, Comparative Example 1, and Comparative Example 2, this invention optimizes the construction of a novel sol-gel synthesis pathway by introducing a citric acid-ethylene glycol complex system, thereby improving the uniformity of the superconducting material and thus increasing the superconducting critical temperature. This is because citric acid, as a multidentate chelating agent, interacts with γ-ethylene glycol through coordination. 3+ Ba 2+ Cu 2+It forms stable complexes and inhibits the hydrolysis and aggregation of metal ions; ethylene glycol, as a polymerizing agent, crosslinks with citric acid through esterification to form a three-dimensional network gel, achieving atomic-scale mixing, solving the problem of component segregation in traditional wet milling, and improving the uniformity of element distribution to over 99.5%, thereby enabling superconducting materials to have better superconducting critical temperature and conductivity.

[0039] Furthermore, during gradient sintering and cooling, a segmented oxygen post-treatment program is designed by dynamically controlling the oxygen atmosphere and introducing constant flow oxygen during calcination. By adjusting the heating and cooling rates, the oxygen content (δ value) in the Y123 crystal path is controlled, which promotes the full oxidation of the superconducting active phase (CuO2 surface). Ultimately, the superconducting critical temperature Tc can reach up to 95K (fully superconducting in the liquid nitrogen temperature range), with performance improved by 3-5K compared to traditional processes.

[0040] The method of the present invention is not limited to the parameter changes mentioned in the above embodiments. The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A YBa2Cu3O 7-δ A method for preparing superconducting materials, characterized in that, The method includes the following preparation process: S1. Weigh out Y2(CO3)3, Ba(NO3)2 and CuSO4·5H2O in a molar ratio of 1:4:6, dissolve them in deionized water, stir well to form a mixed solution; S2. Weigh citric acid and ethylene glycol separately according to a molar ratio of 1:

2. First, add citric acid to the mixed solution in step S1 and stir evenly. Then add ethylene glycol and stir evenly. Then add ammonia water to adjust the pH to 6.5-7.

5. Microwave heat and stir to form a sol. S3. The obtained sol is vacuum dried, then cooled to room temperature and ground into particles; S4. The obtained granular material is placed in an oxygen atmosphere for gradient sintering, and microwave treatment is continued during the sintering process. S5. Perform gradient cooling to cool to room temperature; S6. After the cooled sintered material is ball-milled, it is sieved and then dried again.

2. The YBa2Cu3O according to claim 1 7-δ A method for preparing superconducting materials, characterized in that, In steps S1 and S2, the molar ratio of citric acid to Y2(CO3)3 is 3-5:

1.

3. The YBa2Cu3O according to claim 1 7-δ A method for preparing superconducting materials, characterized in that, In step S2, the microwave heating conditions are: heating to 80°C under millimeter microwave conditions and stirring for 4 hours.

4. The YBa2Cu3O according to claim 1 7-δ A method for preparing superconducting materials, characterized in that, In step S3, the obtained sol is placed in a vacuum drying oven at 40°C for 4-6 hours to dry.

5. The YBa2Cu3O according to claim 1 7-δ A method for preparing superconducting materials, characterized in that, In step S4, the oxygen atmosphere conditions are: a constant flow rate of 200 mL / min and a pressure of 1-2 kPa.

6. The YBa2Cu3O according to claim 1 7-δ A method for preparing superconducting materials, characterized in that, In step S4, the gradient sintering conditions are: heating to 780-820℃ at a heating rate of 5℃ / min and calcining for 3-5 hours, with millimeter microwave treatment during the sintering process.

7. The YBa2Cu3O according to claim 1 7-δ A method for preparing superconducting materials, characterized in that, In step S5, the cooling conditions are as follows: first, cool to 500°C at a cooling rate of 5°C / min, then cool to 200°C at a cooling rate of 1°C / min, and then allow to cool naturally to room temperature.

8. The YBa2Cu3O according to claim 1 7-δ A method for preparing superconducting materials, characterized in that, In step S6, the cooled sintered material is taken out and placed in an agate jar at a ball-to-material ratio of 1:

2. The jar is then placed in a planetary ball mill for ball milling. The powder is sieved through a 120-mesh sieve and then dried in an oven at 100°C for 12 hours.

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