A method for preparing a molten salt assisted copper-based coated conductor and applications thereof

Abstract

A method for preparing a molten salt assisted copper-based coating superconductor and its application. By selecting a copper-based oxide superconducting material and a carrier and designing a molten salt component, an external reaction atmosphere and a heat treatment condition, the oxide precursor prepared according to the cation stoichiometry is mixed with a low-melting-point molten salt and placed on the surface of the carrier, and the precursor is dissolved and migrated in the molten salt under the condition of controlled atmosphere and temperature, and then deposited and crystallized on the surface of the carrier to form a superconducting coating in a non-uniform nucleation manner; after the reaction, the residual molten salt is removed by washing to obtain a coated superconductor, and the superconducting powder generated in the reaction is recovered and the molten salt is recycled for recycling. The present application can realize the controllable preparation of planar or curved coating in the thickness range of nanometer to hundred microns, and the multi-morphology coating structure of strip, fiber, porous body and microsphere array, and has good process window and coverage, and can be recycled to reduce cost. The obtained coating and powder can be used in the fields of superconducting wires and coated conductors, high-field magnets, microwave devices and quantum devices.

Description

Technical Field

[0001] This invention belongs to the field of superconducting functional materials and technology, specifically relating to a method and apparatus for preparing molten salt-assisted copper-based coated conductor materials. By introducing molten salt at low temperatures to ionize the precursors required for the growth of copper-based superconducting oxides and combining this with the design and control of the external chemical environment of the molten salt, the growth of copper-based superconducting oxides on a carrier with a surface possessing a similar two-dimensional crystal structure and lattice parameters can be achieved. The technology and apparatus provided by this invention can effectively prepare copper-based superconducting oxide coated conductors with controllable thickness and curvature, and have potential applications in strong magnetic field magnets, superconducting wires, magnets, microwave devices, and quantum interference devices. Background Technology

[0002] Copper-based high-temperature superconducting materials use CuO2 planes as functional units. Representative systems include La-, Bi-, Tl-, and Hg- systems, as well as barium copper oxides REBa2Cu3O with Y or rare earth cations. 7-δ Where 0≤δ<1, it is abbreviated as REBCO, and a typical representative is YBCO; since the discovery by JG Bednorz laid the foundation and was promoted by the subsequent work of KA Müller and MK Wu, copper-based superconducting systems have entered the research and engineering stage where they can be used in the liquid nitrogen temperature range [1-2]. Copper-based materials have both high T c High critical field and potential high critical current density J c However, it exhibits strong anisotropy, ceramic brittleness, and high sensitivity to grain boundaries and texture. Early work has pointed out that the grain boundary dislocation angle has a significant impact on J. c It has a severe inhibitory effect [3-4].

[0003] In terms of fabrication routes, physical vapor phase epitaxy (PVE), such as PLD, MBE, and magnetron sputtering, is commonly used to obtain high crystal quality and epitaxial orientation, but it is limited in terms of long dimensions, macroscopic uniformity, and micron-level thickness expansion [5-6]. Chemical vapor phase / solution methods, such as MOCVD and TFA-MOD, have become the main industrial routes for tape / coated conductors due to their cost and scalability, but they still face challenges in thick film stress management, grain coarsening, and pinning center retention [7-8]. Thicker and higher quality layers can be obtained through BaF2-substrate-ex-site conversion and liquid phase epitaxy (LPE) liquid phase routes, but the requirements for substrate and process window are strict [9]. The "molten salt-assisted" approach, which uses molten salt or other liquid phase media to reduce the nucleation energy barrier and enhance wetting and ion migration, can improve nucleation and coverage on incoherent or curved substrates.

[0004] Regarding the thickness-performance correlation, experiments and analysis show that J often occurs when the film thickness exceeds the range of approximately 0.5-2 μm. cAs thickness decreases, microstructure coarsens, second-phase segregation and the unfavorable evolution of stress and cracks limit the performance of thick-film conductors without sacrificing J. c Extensions under the premise [10-11]. In addition, on curved or high-curvature substrates, the inhomogeneity of precursor wettability, local chemical environment and ion diffusion can lead to local degradation of coating thickness, density and texture, making it difficult to directly transfer mature preparation processes on planar surfaces to carriers with complex morphologies

[12] .

[0005] In summary, copper-based high-temperature superconducting materials have inherent advantages in terms of system and performance as engineered coated conductors, but the existing processes have obvious limitations: the current preparation technology is difficult to achieve micron-thickness copper-based high-temperature superconducting material coating preparation, and it is difficult to achieve uniform coating on curved surfaces

[13] .

[0006] References 【1】BEDNORZ JG, MüLLER K A. Possible highTc superconductivity in theBa-La-Cu-O system [J]. Zeitschrift für Physik B Condensed Matter, 1986, 64(2): 189-93. 【2】WU MK, ASHBURN JR, TORNG CJ, et al. Superconductivity at 93 Kin a new mixed-phase Y-Ba-Cu-O compound system at ambient pressure [J]. Physical Review Letters, 1987, 58(9): 908-10. 【3】DIMOS D, CHAUDHARI P, MANNHART J, et al. Orientation Dependence ofGrain-Boundary Critical Currents in YBa2Cu3O 7-δ Bicrystals [J]. Physical Review Letters, 1988, 61(2): 219-22. 【4】HILGENKAMP H, MANNHART J. Grain boundaries in high- T csuperconductors [J]. Reviews of Modern Physics, 2002, 74(2): 485-549. 【5】MACMANUS-DRISCOLL J L, WIMBUSH S C. Processing and application ofhigh-temperature superconducting coated conductors [J]. Nature ReviewsMaterials, 2021, 6(7): 587-604. 【6】GUO Z, CHEN L, LI Y, et al. Recent Advances in Pulsed LaserDeposition of REBa2Cu3O 7-δ High-Temperature Superconducting Coated Conductorsand Artificial Flux Pinning [J]. Materials (Basel), 2025, 18(21). 【7】TAKESHI A, IZUMI H. Review of a chemical approach to YBa2Cu3O 7-x -coated superconductors-metalorganic deposition using trifluoroacetates [J].Superconductor Science and Technology, 2003, 16(11): R71. 【8】XU A, ZHANG Y, GHARAHCHESHMEH M H, et al. J e (4.2 K, 31.2 T) beyond1 kA / mm 2 of a ~3.2 μm thick, 20 mol% Zr-added MOCVD REBCO coated conductor[J]. Scientific Reports, 2017, 7(1): 6853. 【9】HOLESINGER T G, ARENDT P N, FEENSTRA R, et al. Liquid mediatedgrowth and the bimodal microstructure of YBa2Cu3O 7-δ films made by the ex situconversion of physical vapor deposited BaF2 precursors [J]. Journal ofMaterials Research, 2005, 20(5): 1216-33.

[10] MACMANUS-DRISCOLL J L, FOLTYN S R, JIA Q X, et al. Stronglyenhanced current densities in superconducting coated conductors of YBa2Cu3O 7-x + BaZrO3 [J]. Nature Materials, 2004, 3(7): 439-43.

[11] EMERGO R L S, WU J Z, AYTUG T, et al. Thickness dependence ofsuperconducting critical current densityin vicinal YBa2Cu3O 7-δ thick films [J].Applied Physics Letters, 2004, 85(4): 618-20.

[12] XU Y L, SHI D. A Review of Coated Conductor Development [J].Tsinghua Science and Technology, 2003, 8(3): 342-69.

[13] HORIDE T, OKUMURA ​​S, ITO S, et al. Integrated process-propertymodeling of YBa2Cu3O7 superconducting film for data and model driven processdesign [J]. Communications Engineering, 2025, 4(1): 114. Summary of the Invention

[0007] This invention provides a method for preparing molten salt-assisted copper-based coated superconductors and their applications. The main concept lies in introducing molten salt at low temperatures to ionize the precursors required for the growth of copper-based superconducting oxides, and then controlling their valence states by designing and controlling the external chemical environment of the molten salt. This allows the growth of copper-based superconducting oxides on a carrier with a surface possessing a similar two-dimensional planar crystal structure and lattice parameters. The technology and apparatus provided by this invention can effectively prepare planar and curved copper-based superconducting oxide coated conductors with thicknesses ranging from nanometers to hundreds of micrometers. The morphologies mainly include planar coated conductor films, cladding bodies, cladding fibers, and cladding tapes. Simultaneously, corresponding copper-based superconducting oxide powders are obtained, and the flux is recycled. The prepared copper-based coated superconducting composite materials and powder materials have potential application value in strong magnetic field magnets, superconducting wires, magnets, microwave devices, and quantum interference devices.

[0008] A method for preparing a molten salt-assisted copper-based coated superconductor, characterized by comprising the following preparation steps:

[0009] 1) Based on the application scenarios of coated superconductors, select copper-based oxide superconducting materials and carriers, and design corresponding molten salt components, synthesis chemical environment, and synthesis thermodynamic conditions;

[0010] 2) Weigh the corresponding metal element precursor powder according to the cation stoichiometry in the selected copper-based oxide superconducting material, mix it with the molten salt in the optimized ratio, and then place it evenly on the surface of the selected carrier.

[0011] 3) By designing the external reaction atmosphere of molten salt, the chemical environment of synthesis and the valence state of material ions are controlled. The precursor metal ions are heated to a certain temperature so that they dissolve in the molten salt and are deposited and grown in a non-uniform nucleation manner on the surface of a carrier with a similar two-dimensional crystal structure and lattice parameters to the copper-based oxide superconducting material. The thickness of the coating conductor is controlled by the reaction time.

[0012] 4) After the superconductor coating reaches the required thickness, the growth device is cooled to near room temperature. The prepared copper-based oxide coated superconductor composite material is then removed and residual flux is removed by solvent washing.

[0013] 5) Collect the remaining reaction products in the reaction device, separate the synergistically generated copper-based oxide superconducting material powder products by solvent washing, and separate the used flux and washing solvent from the recovered solvent to achieve recycling.

[0014] Furthermore, the copper-based oxide superconductor material includes: Ca 1-x Sr x CuO2, where 0 ≤ x ≤ 1; La 2- x Sr x CuO 4±δ Where 0 ≤ x ≤ 0.5 and 0 ≤ δ ≤ 0.2, Nd 2-x Ce x CuO 4±δ Where 0 ≤ x ≤ 0.5 and 0 ≤ δ ≤ 0.2; Bi2Sr2CuO 6+δ That is, Bi-22O1, where 0≤δ≤0.5; Bi2Sr2CaCu2O 8+δ That is, Bi-2212, where 0≤δ≤0.5; Bi2Sr2Ca2Cu3O 10+δ That is, Bi-2223, where 0≤δ≤0.5, Cu 1-x C x Ba2Ca3Cu4O 11+δ That is, (Cu,C)-1234, where 0≤x≤1 and 0≤δ≤0.5.

[0015] Furthermore, the carrier surface material system in contact with the coated superconductor includes: perovskite oxide, spinel oxide, quartz, magnesium oxide, gallium oxide, aluminum oxide, cerium oxide, mica, silicon, silicon carbide, germanium, gallium arsenide, and alloys; wherein the perovskite oxide is preferably: strontium titanate (SrTiO3), lanthanum aluminate (LaAlO3), and neodymium gallium oxide (NdGaO3); the spinel oxide is preferably: magnesium aluminum spinel, zinc aluminum spinel, and magnesium gallium spinel; the alloy is preferably: nickel-tungsten alloy Ni-W / RABiTS. The materials used in the process include strips, Hastelloy / Ni-based corrosion-resistant alloys, Inconel / Ni-Cr-based superalloys, 316L stainless steel, copper and copper-based alloys Cu / Cu-Ni / Monel, titanium and titanium alloys Ti / Ti-6Al-4V, and other engineered heat-resistant alloys. The surfaces of the above materials have similar two-dimensional crystal structures and lattice parameters to the specific crystal planes of the copper-based oxide superconducting material to be grown, which can trigger the non-uniform nucleation and growth of copper-based superconducting oxides on them. The carrier morphology includes single crystals, polycrystalline materials, porous ceramic bodies, whiskers or fibers of the above materials, or other materials with surface modifications of the above materials.

[0016] In preferred embodiment 1, a Bi-2212 coating with superconducting properties is grown on a lanthanum aluminate (LaAlO3) single-crystal substrate. The single-crystal substrate, polycrystalline ceramic substrate, surface-modified metal strip or foil, ceramic whiskers, ceramic fibers, ceramic spheres, ceramic bulk, and porous ceramic body are all selected as carriers. The surfaces of these carriers have similar two-dimensional crystal structures and lattice parameters to the specific crystal planes of the copper-based oxide superconducting material to be grown. This solves the problems of insufficient film adhesion, poor orientation, and difficulty in uniformly coating complex surfaces in existing technologies, thereby improving the continuity, uniformity, and carrier adaptability of the film or coating. Therefore, this invention is applicable not only to planar substrates but also to curved surfaces, fibers, and porous structures, offering greater application scalability.

[0017] Further, the morphology of the coating superconductor support includes: a single-crystal substrate for growing the coating superconductor film material, comprising strontium titanate (SrTiO3), lanthanum aluminate (LaAlO3), neodymium gallium oxide (NdGaO3), magnesium oxide (MgO), magnesium aluminum spinel (MgAl2O4), sapphire (Al2O3), silicon dioxide, quartz (SiO2), silicon (Si), germanium (Ge), and gallium arsenide (GaAs), preferably strontium titanate (SrTiO3), lanthanum aluminate (LaAlO3), neodymium gallium oxide (NdGaO3), magnesium oxide (MgO), and sapphire (Al2O3); for growing the coating superconductor film material. The polycrystalline substrate for the superconducting film material includes polycrystalline alumina (Al2O3), zirconium oxide-stabilized yttrium oxide (YSZ), polycrystalline magnesium oxide (MgO), glass ceramics, and other ceramic substrates. The substrate used to grow the superconducting film material contains a heterogeneous buffer layer, including cerium dioxide (CeO2), zirconium oxide-stabilized yttrium oxide (YSZ), lanthanum nickelate (LaNiO3), strontium ruthenium ruthenium oxide (SrRuO3), barium zirconate (BaZrO3), magnesium oxide (MgO), titanium nitride (TiN), and an amorphous / oriented buffer layer formed by ion beam-assisted deposition (IBAD). The system includes an IBAD-CeO2, preferably a cerium dioxide (CeO2) buffer layer; a bulk carrier for growing the coated superconductor coating, such as alumina (Al2O3) bulk, zirconia (ZrO2) ceramic bulk, titanium dioxide (TiO2) bulk, glass-ceramic and porous ceramic / foam ceramic porous bodies, densified ceramic substrates, or metal / ceramic composite bulk, preferably porous or foamed alumina (Al2O3) ceramic as the carrier; and a ceramic fiber carrier for growing the coated superconductor coated fibers, including α-alumina. Ceramic fibers, zirconium oxide or zirconium oxide-stabilized yttrium oxide fibers, silicon carbide fibers (SiC), mullite-based ceramic fibers, and other high-strength, high-temperature stable ceramic fiber materials, preferably α-alumina ceramic fibers; the substrate for growing coated superconductors includes metal strips and metal foils, containing nickel-tungsten strips (Ni-W / RABiTS), Hastelloy strips / nickel-based alloy strips, and stainless steel strips or copper strips / copper foils: preferably nickel-tungsten strips (Ni-W / RABiTS) containing a cerium dioxide (CeO2) buffer layer.

[0018] Further, the molten salt includes: alkali metal halides, alkali metal carbonates, alkali metal sulfates, and their eutectics, preferably potassium chloride (KCl), sodium chloride (NaCl), lithium chloride (LiCl), rubidium chloride (RbCl), cesium chloride (CsCl), potassium bromide (KBr), sodium bromide (NaBr), lithium fluoride (LiF), potassium fluoride (KF), KCl-NaCl eutectic, KCl-RbCl eutectic, KCl-CsCl eutectic, NaCl-RbCl eutectic, NaCl-CsCl eutectic, LiCl-KCl eutectic, potassium carbonate (K2CO3), sodium carbonate (Na2CO3), K2CO3-Na2CO3 eutectic, sodium sulfate (Na2SO4), potassium sulfate (K2SO4), NaCl-Na2SO4 eutectic, and KCl-K2SO4 eutectic.

[0019] In existing copper-based superconducting material preparation technologies, the precursor mass transfer efficiency is low, the phase formation process is limited, and it is difficult to simultaneously achieve the effective preparation of thin films, coatings, and powders. For complex supports such as curved surfaces, fibers, and porous bodies, existing methods suffer from poor coating uniformity and continuity. Therefore, the molten salt selected is characterized by not reacting with the oxide precursors used in the preparation of copper-based oxide superconducting materials. Its molten state can effectively dissolve the cations of the oxide precursors used to grow copper-based superconducting oxides, thereby significantly reducing the material synthesis temperature and improving film uniformity. At the same time, it solves the problems of insufficient reaction, low preparation efficiency, and limited product morphology in existing technologies, so that the target product can be formed on the support surface to obtain thin films or coatings, and can also be further obtained as powders, achieving the unification of thin film / coating and powder preparation. Thus, this invention has the characteristics of diverse product forms and wide process applicability.

[0020] Furthermore, the external reaction atmosphere design of the molten salt includes: oxygen O2, air, ozone O3, nitrogen N2, inert gas, carbon dioxide CO2, and a mixture of the above gases, preferably oxygen O2, air, argon Ar, and a CO2 / O2 mixture; for different copper-based oxide superconducting material systems, the valence state balance of copper and related cations can be adjusted by selecting the atmosphere, the oxygen content δ of the target phase can be precisely controlled, and the thermal stability of the carbonate or carbon-oxygen structure can be maintained when using carbonate molten salt or carbon-containing reservoir structure.

[0021] By synergistically regulating the reaction process through a molten salt system and an external atmosphere, the molten salt provides ion migration channels, while the external atmosphere regulates oxygen partial pressure and the valence states of related elements. This synergistic effect helps stabilize the target superconducting phase and suppress the formation of impurity phases, solving the problems of unstable phase formation, numerous impurity phases, and large performance fluctuations in existing technologies. Therefore, this invention features stable superconducting phase formation and good consistency in material properties.

[0022] Furthermore, the coordinated design of thermodynamic and kinetic parameters includes the coordinated optimization of reaction temperature, reaction pressure, reaction time, and the ratio of molten salt components to precursors. The specific selection of the reaction temperature should be determined based on the melting point and eutectic characteristics of the molten salt used, the thermodynamic formation region of the target copper-based superconducting phase, the thermal decomposition and diffusion characteristics of the precursor, and the selected atmosphere. By combining the design of the reaction temperature within the range of 500-1100 degrees Celsius, the selected molten salt is placed within the window of melting and generating effective liquid phase migration. By linking the reaction temperature with the selected atmosphere, it is possible to achieve fine adjustment of the liquid phase existence time, the solubility and migration rate of the precursor in the molten salt, the nucleation density and grain growth rate, the loss rate of volatile components, and the diffusion and reabsorption behavior of oxygen. This allows for controllable adjustment of coating thickness, grain size and morphology, density, porosity, stress state, and phase composition.

[0023] The temperature control is characterized by the formation of a stable liquid phase at lower temperatures to reduce volatilization loss and thermal stress, while simultaneously promoting grain growth and densification at higher temperatures. This balances the requirements of thickness growth and electrical performance during the process. In preferred embodiment 1, this temperature range is used to achieve the process effects of thick film densification and a higher critical current density. By controlling the reaction pressure within the range of approximately 0.1 MPa to several MPa, preferably at atmospheric pressure, the escape rate of volatile components, gas phase transport behavior, and redox balance can be regulated, thereby affecting the retention of precursor composition, the stability of the target phase, and the precise control of oxygen content δ. The pressure control is characterized by the ease of scale-up and reproducibility of the preparation process at atmospheric pressure. When it is necessary to suppress volatilization or change the phase stability domain, a pressurization strategy can be used to improve phase formation behavior. In preferred embodiment 10, good phase formation consistency has been achieved through the linkage of atmospheric pressure and atmosphere. By controlling the reaction time within the range of 1-72 hours, preferably 3-5 hours, and combining multiple short-time depositions with a medium-temperature densification strategy, controllable accumulation of deposition thickness, temporal regulation of grain size, and elimination of porosity can be achieved, thereby obtaining coatings that meet different thickness levels and microstructure requirements. The characteristics of this time control are that short-time processing helps suppress grain coarsening and supports layered, controllable growth, while extended holding time promotes thick-layer densification and improved grain connectivity, achieving simultaneous optimization of thickness and critical current density. Ultimately, thickness control can be achieved by adjusting the precursor concentration and molten salt / precursor ratio, segmented pulse feeding, multi-step heat treatment, and short-time high-temperature densification; morphology and orientation can be induced by optimizing the lattice matching and surface wettability of the substrate / buffer layer, the linked cooling rate, and the external oxygen partial pressure to induce directional nucleation and texture formation; the molten salt composition, by changing the solubility and diffusion coefficient of the precursor in the liquid phase, regulates the nucleation-growth kinetics and affects grain evolution and particle morphology.

[0024] Furthermore, the method for recovering molten salt and generating superconducting powder mainly includes stepwise washing and solid-liquid separation of the reaction products, dissolution and recrystallization recovery of the molten salt, and collection and reuse of the superconducting powder. After the reaction, the products are washed with deionized water or alcohol solvents to dissolve and remove soluble molten salt. Solid-liquid separation is achieved by filtration or centrifugation to obtain superconducting powder. The resulting molten salt-containing washing liquid is recovered and recycled by evaporation crystallization or membrane separation. The separated superconducting powder can be directly used as a functional powder or used in subsequent forming and sintering processes after drying and necessary heat treatment, thereby achieving synergistic recovery of molten salt medium and superconducting powder and reducing preparation costs and environmental impact.

[0025] Compared to existing technologies where the fluxing medium is difficult to recycle, this invention allows for the separation and recovery of superconducting powder and molten salt after product preparation, solving the problems of high resource waste and high costs. Therefore, this invention offers the advantages of high raw material utilization, low preparation cost, and suitability for large-scale application.

[0026] Furthermore, the applications of the coated superconductors prepared by this method mainly include quantum devices, superconducting electronic devices, coated superconducting wires and tapes, power electronic devices, high-field magnet coils, flexible superconducting cables, braidable transmission lines, bending sensors, microwave and terahertz devices, sensor arrays, and multifunctional electromagnetic structures.

[0027] The powder prepared by this method can be further sintered to form bulk or textured ceramic materials, or combined with metal matrices, ceramic matrices and polymer matrices to construct superconducting composite conductors, functionally graded materials, electromagnetic shielding structures and thermal management functional materials, and used in magnet filling structures, microwave absorbing materials and porous functional structures.

[0028] Furthermore, this method can prepare and adapt to a variety of structural morphologies, including continuous thin film and thick film structures, fiber or wire surface coating structures, microsphere or particle array coating structures, porous or foam block coating structures, heterogeneous multilayer and interface engineering structures, and micro-nano patterned coating structures, thereby meeting the needs of preparing Josephson junction devices, coated conductors and engineered magnets, flexible and braidable superconducting devices, microstructured electromagnetic functional devices, multilayer interface pinning reinforcement structures, and micro-nano device integration applications.

[0029] The advantages of this invention are as follows: By selecting copper-based oxide superconducting materials and a support, and designing the molten salt composition, external reaction atmosphere, and heat treatment conditions, the oxide precursor, prepared according to stoichiometric cations, is mixed with a low-melting-point molten salt and placed on the support surface. Under controlled atmosphere and temperature conditions, the precursor dissolves and migrates in the molten salt and deposits and crystallizes on the support surface in a non-uniform nucleation manner to form a superconducting coating. After the reaction, residual molten salt is removed by washing to obtain a coated superconductor. Simultaneously, the superconducting powder generated in the reaction and the molten salt are recovered for recycling. This invention can achieve planar or curved coatings with thicknesses ranging from nanometers to hundreds of micrometers, as well as controllable preparation of multi-morphological coating structures such as tapes, fibers, porous bodies, and microsphere arrays. The process window is adjustable, the coverage is good, and the recyclability reduces costs. The resulting coatings and powders can be used in the fields of superconducting wires and coated conductors, high-field magnets, microwave devices, and quantum devices. Attached Figure Description

[0030] Figure 1 This is a scanning electron microscope image of a Bi-2212 thin film grown on a lanthanum aluminate substrate LaAlO3 using the method of this invention.

[0031] Figure 2 The image shows the X-ray diffraction pattern of the Bi-2212 thin film grown on the lanthanum aluminate substrate LaAlO3 using the method of this invention.

[0032] Figure 3 The X-ray diffraction pattern is shown for the recovered powder after growing a Bi-2212 thin film on a lanthanum aluminate substrate LaAlO3 using the method of this invention.

[0033] Figure 4 The resistance-temperature relationship curves are shown for the recovered powder after growing a Bi-2212 thin film on a lanthanum aluminate substrate LaAlO3 using the method of this invention.

[0034] Figure 5 The resistance-temperature relationship curves are shown for the growth of Bi-2212 thin films on lanthanum aluminate substrate LaAlO3 using the method of the present invention. Detailed Implementation

[0035] Unless otherwise specified, all raw materials used in this invention can be obtained commercially available or prepared according to conventional methods in the art. Unless otherwise defined or stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of skill in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of this invention.

[0036] Other aspects of the invention will be apparent to those skilled in the art from the disclosure herein.

[0037] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer.

[0038] Testing methods: The prepared materials were characterized using XRD, SEM, CTA, and PPMS. The characterization methods were performed according to generally accepted standards in the field.

[0039] Example 1:

[0040] Bismuth oxide (Bi₂O₃), strontium oxide (SrO), calcium oxide (CaO), and copper oxide (CuO) were mixed in the manner of Bi₂Sr₂CaCu₂O. 8+δ The cations with a stoichiometric ratio of 2:2:1:2, where 0≤δ≤0.5, were weighed and potassium chloride (KCl) was added as flux to make the mass ratio of molten salt to precursor 2:1. The mixture was then ground in an agate mortar for 20 minutes until homogeneous. The mixed powder was evenly spread and brought into close contact with the surface of a lanthanum aluminate (LaAlO3) single crystal substrate, and then placed in a quartz tube. The temperature was raised to 850℃ under normal atmospheric pressure and held for 4 hours, allowing the precursor to dissolve and migrate in the molten KCl and to form Bi2Sr2CaCu2O2 on the substrate surface through heterogeneous nucleation. 8+δ coating. Figure 1 The image shows a scanning electron microscope (SEM) image of the Bi-2212 thin film prepared according to Example 1. After the reaction was completed and cooled to room temperature, the sample was removed and washed stepwise with deionized water to remove residual KCl, then rinsed with ethanol and dried to obtain the Bi-2212 superconducting thin film. Figure 2 The image shows the X-ray diffraction pattern of the Bi-2212 thin film. As can be seen from the image, the prepared film is a Bi-2212-based film with a thickness reaching micrometers and exhibiting excellent superconducting properties. After the reaction is complete and the substrate is removed, the remaining solid products in the reactor are collected along with the superconducting powder obtained through washing and separation. The powder is thoroughly washed with deionized water to remove molten salt and dried, then heat-treated to stabilize the crystalline phase. Subsequently, the powder is pressed into sheets and sintered to obtain Bi-2212 ceramic blocks, realizing the recovery and reuse of the superconducting powder generated in the reaction. Finally, the washing liquid is collected and KCl crystals are recovered through evaporation and crystallization; the recovered KCl is dried and reused as a flux in the next batch.

[0041] Example 2:

[0042] Bismuth oxide (Bi₂O₃), strontium oxide (SrO), calcium oxide (CaO), and copper oxide (CuO) were mixed in the manner of Bi₂Sr₂CaCu₂O. 8+δThe cations with a stoichiometric ratio of 2:2:1:2, where 0≤δ≤0.5, were weighed and potassium chloride (KCl) was added as flux to make the mass ratio of molten salt to precursor 2:1. The mixture was then ground in an agate mortar for 20 minutes until homogeneous. The mixed powder was evenly spread and brought into close contact with the surface of a lanthanum aluminate (LaAlO3) single crystal substrate, and then placed in a quartz tube. The temperature was raised to 850℃ under normal pressure in an air atmosphere and held for 3 hours, allowing the precursor to dissolve and migrate in the molten KCl and to form Bi2Sr2CaCu2O2 on the substrate surface through heterogeneous nucleation. 8+δ Coating. After the reaction was completed and cooled to room temperature, the sample was removed and washed stepwise with deionized water to remove residual KCl, followed by rinsing with ethanol and drying to obtain a Bi-2212 superconducting film with good superconducting properties. After the reaction was completed and the substrate was removed, the remaining solid products in the reactor and the superconducting powder obtained by washing and separation were collected. Figure 3 The X-ray diffraction pattern of the obtained superconducting powder is shown. The powder was thoroughly washed with deionized water to remove molten salt and dried, and then heat-treated to stabilize the crystal phase. Subsequently, the powder was pressed into sheets and sintered to obtain Bi-2212 ceramic blocks, realizing the recovery and reuse of the superconducting powder generated by the reaction, which has good superconducting properties. Figure 4 The resistance-temperature relationship curves for obtaining Bi-2212 ceramic bulk materials by sintering were shown. Finally, the washing liquid was collected and KCl crystals were recovered through evaporation and crystallization; the recovered KCl was dried and reused as flux in the next batch.

[0043] Example 3:

[0044] Bismuth oxide (Bi₂O₃), strontium oxide (SrO), calcium oxide (CaO), and copper oxide (CuO) were mixed in the manner of Bi₂Sr₂CaCu₂O. 8+δ The cations with a stoichiometric ratio of 2:2:1:2, where 0≤δ≤0.5, were weighed and potassium chloride (KCl) was added to make the mass ratio of molten salt to precursor 2:1. The mixture was then ground in an agate mortar for 20 minutes until homogeneous. The mixed powder was evenly spread and brought into close contact with the surface of a lanthanum aluminate (LaAlO3) single crystal substrate, and then placed in a quartz tube. The temperature was raised to 850℃ under normal atmospheric pressure and held for 5 hours, allowing the precursor to dissolve and migrate in the molten KCl and to form Bi2Sr2CaCu2O non-uniform nucleation on the substrate surface. 8+δ Coating. After the reaction was completed and cooled to room temperature, the sample was removed and washed stepwise with deionized water to remove residual KCl. Then it was rinsed with ethanol and dried to obtain a Bi-2212 superconducting film with good superconducting properties. Figure 5The resistance-temperature relationship curves for the Bi-2212 thin film are shown. After the reaction was completed and the substrate was removed, the remaining solid products in the reactor and the superconducting powder obtained from washing and separation were collected. The powder was thoroughly washed with deionized water to remove molten salt and dried, followed by heat treatment to stabilize the crystalline phase. Subsequently, the powder was pressed into sheets and sintered to obtain Bi-2212 ceramic blocks, realizing the recovery and reuse of the superconducting powder generated in the reaction, which exhibits good superconducting properties. Finally, the washing liquid was collected and KCl crystals were recovered by evaporation crystallization; the recovered KCl was dried and reused as a flux in the next batch.

[0045] Example 4:

[0046] Bismuth oxide (Bi₂O₃), strontium oxide (SrO), calcium oxide (CaO), and copper oxide (CuO) were mixed in the manner of Bi₂Sr₂CaCu₂O. 8+δ The cations with a stoichiometric ratio of 2:2:1:2, where 0≤δ≤0.5, were weighed and potassium chloride (KCl) was added to make the mass ratio of molten salt to precursor 2:1. The mixture was then ground in an agate mortar for 20 minutes until homogeneous. The mixed powder was evenly spread and brought into close contact with the surface of a strontium titanate (SrTiO3) single crystal substrate, and then placed in a quartz tube. The temperature was raised to 850℃ under normal atmospheric pressure and held for 3 hours, allowing the precursor to dissolve and migrate in the molten KCl and to form Bi2Sr2CaCu2O3 on the substrate surface through heterogeneous nucleation. 8+δ Coating. After the reaction was completed and cooled to room temperature, the sample was removed and washed stepwise with deionized water to remove residual KCl. It was then rinsed with ethanol and dried to obtain a Bi-2212 superconducting thin film with excellent superconducting properties. After the reaction was complete and the substrate was removed, the remaining solid products in the reactor and the superconducting powder obtained from washing were collected. The powder was thoroughly washed with deionized water to remove molten salt and dried, then heat-treated to stabilize the crystalline phase. The powder was then pressed into sheets and sintered to obtain Bi-2212 ceramic blocks, realizing the recovery and reuse of the superconducting powder generated in the reaction, which exhibits excellent superconducting properties. Finally, the washing liquid was collected and KCl crystals were recovered through evaporation crystallization. The recovered KCl was dried and reused as a flux in the next batch.

[0047] Example 5:

[0048] Bismuth oxide (Bi₂O₃), strontium oxide (SrO), calcium oxide (CaO), and copper oxide (CuO) were mixed in the manner of Bi₂Sr₂CaCu₂O. 8+δThe cations with a stoichiometric ratio of 2:2:1:2, where 0≤δ≤0.5, were weighed and potassium chloride (KCl) was added as flux to make the mass ratio of molten salt to precursor 2:1. The mixture was then ground in an agate mortar for 20 minutes until homogeneous. The mixed powder was evenly spread and brought into close contact with the surface of a strontium titanate (SrTiO3) single crystal substrate, and then placed in a quartz tube. The temperature was raised to 850℃ under normal atmospheric pressure and held for 5 hours, allowing the precursor to dissolve and migrate in the molten KCl and to form Bi2Sr2CaCu2O3 on the substrate surface through heterogeneous nucleation. 8+δ Coating. After the reaction was completed and cooled to room temperature, the sample was removed and washed stepwise with deionized water to remove residual KCl. It was then rinsed with ethanol and dried to obtain a Bi-2212 superconducting thin film with excellent superconducting properties. After the reaction was complete and the substrate was removed, the remaining solid products in the reactor and the superconducting powder obtained from washing were collected. The powder was thoroughly washed with deionized water to remove molten salt and dried, then heat-treated to stabilize the crystalline phase. The powder was then pressed into sheets and sintered to obtain Bi-2212 ceramic blocks, realizing the recovery and reuse of the superconducting powder generated in the reaction, which exhibits excellent superconducting properties. Finally, the washing liquid was collected and KCl crystals were recovered through evaporation crystallization. The recovered KCl was dried and reused as a flux in the next batch.

[0049] Example 6:

[0050] Bismuth oxide (Bi₂O₃), strontium oxide (SrO), calcium oxide (CaO), and copper oxide (CuO) were mixed in the manner of Bi₂Sr₂CaCu₂O. 8+δ The cations with a stoichiometric ratio of 2:2:1:2, where 0≤δ≤0.5, were weighed and potassium chloride (KCl) was added to make the mass ratio of molten salt to precursor 2:1. The mixture was then ground in an agate mortar for 20 minutes until homogeneous. The mixed powder was evenly spread and brought into close contact with the surface of a lanthanum aluminate (LaAlO3) single crystal substrate, and then placed in a quartz tube. The temperature was raised to 800℃ under normal pressure in an air atmosphere and held for 3 hours, allowing the precursor to dissolve and migrate in the molten KCl and to form Bi2Sr2CaCu2O non-uniform nucleation on the substrate surface. 8+δ Coating. After the reaction was completed and cooled to room temperature, the sample was removed and washed stepwise with deionized water to remove residual KCl. It was then rinsed with ethanol and dried to obtain a Bi-2212 superconducting thin film with excellent superconducting properties. After the reaction was complete and the substrate was removed, the remaining solid products in the reactor and the superconducting powder obtained from washing were collected. The powder was thoroughly washed with deionized water to remove molten salt and dried, then heat-treated to stabilize the crystalline phase. The powder was then pressed into sheets and sintered to obtain Bi-2212 ceramic blocks, realizing the recovery and reuse of the superconducting powder generated in the reaction, which exhibits excellent superconducting properties. Finally, the washing liquid was collected and KCl crystals were recovered through evaporation crystallization. The recovered KCl was dried and reused as a flux in the next batch.

[0051] Example 7:

[0052] Bismuth oxide (Bi₂O₃), strontium oxide (SrO), calcium oxide (CaO), and copper oxide (CuO) were mixed in the manner of Bi₂Sr₂CaCu₂O. 8+δ The cations with a stoichiometry of 2:2:1:2, where 0≤δ≤0.5, were weighed, and potassium chloride (KCl) was added as flux to make the mass ratio of molten salt to precursor 2:1. The mixture was then ground in an agate mortar for 20 minutes until homogeneous. The mixed powder was evenly spread and brought into close contact with the surface of a lanthanum aluminate (LaAlO3) single crystal substrate, and then placed in a quartz tube. The temperature was raised to 900℃ under normal atmospheric pressure and held for 3 hours, allowing the precursor to dissolve and migrate in the molten KCl and to form Bi2Sr2CaCu2O non-uniform nucleation on the substrate surface. 8+δ Coating. After the reaction was completed and cooled to room temperature, the sample was removed and washed stepwise with deionized water to remove residual KCl. It was then rinsed with ethanol and dried to obtain a Bi-2212 superconducting thin film with excellent superconducting properties. After the reaction was complete and the substrate was removed, the remaining solid products in the reactor and the superconducting powder obtained from washing were collected. The powder was thoroughly washed with deionized water to remove molten salt and dried, then heat-treated to stabilize the crystalline phase. The powder was then pressed into sheets and sintered to obtain Bi-2212 ceramic blocks, realizing the recovery and reuse of the superconducting powder generated in the reaction, which exhibits excellent superconducting properties. Finally, the washing liquid was collected and KCl crystals were recovered through evaporation crystallization. The recovered KCl was dried and reused as a flux in the next batch.

[0053] Example 8:

[0054] Bismuth oxide (Bi₂O₃), strontium oxide (SrO), calcium oxide (CaO), and copper oxide (CuO) were mixed in the manner of Bi₂Sr₂CaCu₂O. 8+δ The cations with a stoichiometric ratio of 2:2:1:2, where 0≤δ≤0.5, were weighed and potassium chloride (KCl) was added as flux to make the mass ratio of molten salt to precursor 2:1. The mixture was then ground in an agate mortar for 20 minutes until homogeneous. The mixed powder was evenly spread and brought into close contact with the surface of a lanthanum aluminate (LaAlO3) single crystal substrate, and then placed in a quartz tube. The temperature was raised to 800℃ under normal atmospheric pressure and held for 5 hours, allowing the precursor to dissolve and migrate in the molten KCl and to form Bi2Sr2CaCu2O2 on the substrate surface through heterogeneous nucleation. 8+δCoating. After the reaction was completed and cooled to room temperature, the sample was removed and washed stepwise with deionized water to remove residual KCl. It was then rinsed with ethanol and dried to obtain a Bi-2212 superconducting thin film with excellent superconducting properties. After the reaction was complete and the substrate was removed, the remaining solid products in the reactor and the superconducting powder obtained from washing were collected. The powder was thoroughly washed with deionized water to remove molten salt and dried, then heat-treated to stabilize the crystalline phase. The powder was then pressed into sheets and sintered to obtain Bi-2212 ceramic blocks, realizing the recovery and reuse of the superconducting powder generated in the reaction, which exhibits excellent superconducting properties. Finally, the washing liquid was collected and KCl crystals were recovered through evaporation crystallization. The recovered KCl was dried and reused as a flux in the next batch.

[0055] Example 9:

[0056] Bismuth oxide (Bi₂O₃), strontium oxide (SrO), calcium oxide (CaO), and copper oxide (CuO) were mixed in the manner of Bi₂Sr₂CaCu₂O. 8+δ The cations with a stoichiometric ratio of 2:2:1:2, where 0≤δ≤0.5, were weighed and potassium chloride (KCl) was added as flux to make the mass ratio of molten salt to precursor 2:1. The mixture was then ground in an agate mortar for 20 minutes until homogeneous. The mixed powder was evenly spread and brought into close contact with the surface of a lanthanum aluminate (LaAlO3) single crystal substrate, and then placed in a quartz tube. The temperature was raised to 900℃ under normal atmospheric pressure and held for 5 hours, allowing the precursor to dissolve and migrate in the molten KCl and to form Bi2Sr2CaCu2O2 on the substrate surface through heterogeneous nucleation. 8+δ Coating. After the reaction was completed and cooled to room temperature, the sample was removed and washed stepwise with deionized water to remove residual KCl. It was then rinsed with ethanol and dried to obtain a Bi-2212 superconducting thin film with excellent superconducting properties. After the reaction was complete and the substrate was removed, the remaining solid products in the reactor and the superconducting powder obtained from washing were collected. The powder was thoroughly washed with deionized water to remove molten salt and dried, then heat-treated to stabilize the crystalline phase. The powder was then pressed into sheets and sintered to obtain Bi-2212 ceramic blocks, realizing the recovery and reuse of the superconducting powder generated in the reaction, which exhibits excellent superconducting properties. Finally, the washing liquid was collected and KCl crystals were recovered through evaporation crystallization. The recovered KCl was dried and reused as a flux in the next batch.

[0057] Example 10:

[0058] Bismuth oxide (Bi₂O₃), strontium oxide (SrO), calcium oxide (CaO), and copper oxide (CuO) were mixed in the manner of Bi₂Sr₂CaCu₂O. 8+δThe cations with a stoichiometric ratio of 2:2:1:2, where 0≤δ≤0.5, were weighed and potassium chloride (KCl) was added as flux to make the mass ratio of molten salt to precursor 2:1. The mixture was then ground in an agate mortar for 20 minutes until homogeneous. The mixed powder was evenly spread and brought into close contact with the surface of a lanthanum aluminate (LaAlO3) single crystal substrate, and then placed in a quartz tube. The temperature was raised to 850℃ under atmospheric pressure and held for 4 hours under inert argon (Ar) gas, allowing the precursor to dissolve and migrate in molten KCl and heterogeneously nucleate on the substrate surface to form Bi2Sr2CaCu2O. 8+δ Coating. After the reaction, the sample was cooled to room temperature and washed stepwise with deionized water to remove residual KCl. It was then rinsed with ethanol and dried to obtain a Bi-2212 superconducting thin film. As shown in the figure, the prepared film is a Bi-2212-based film with a thickness reaching micrometers and exhibiting excellent superconducting properties. After the reaction was completed and the substrate was removed, the remaining solid products in the reactor and the superconducting powder obtained from washing and separation were collected. The powder was thoroughly washed with deionized water to remove molten salt and dried, then heat-treated to stabilize the crystalline phase. The powder was then pressed into sheets and sintered to obtain Bi-2212 ceramic blocks, realizing the recovery and reuse of the superconducting powder generated in the reaction. Finally, the washing liquid was collected and KCl crystals were recovered through evaporation crystallization. The recovered KCl was dried and reused as a flux in the next batch.

[0059] Example 11:

[0060] Bismuth oxide (Bi₂O₃), strontium oxide (SrO), calcium oxide (CaO), and copper oxide (CuO) were mixed in the manner of Bi₂Sr₂CaCu₂O. 8+δ The cations with a stoichiometric ratio of 2:2:1:2, where 0≤δ≤0.5, were weighed and potassium chloride (NaCl) was added as flux to make the mass ratio of molten salt to precursor 2:1. The mixture was then ground in an agate mortar for 20 minutes until homogeneous. The mixed powder was evenly spread and brought into close contact with the surface of a lanthanum aluminate (LaAlO3) single crystal substrate, and then placed in a quartz tube. The temperature was raised to 850℃ under atmospheric pressure with inert argon (Ar) and held for 4 hours, allowing the precursor to dissolve and migrate in molten NaCl and to form Bi2Sr2CaCu2O2 on the substrate surface through heterogeneous nucleation. 8+δCoating. After the reaction was completed and cooled to room temperature, the sample was removed and washed stepwise with deionized water to remove residual NaCl, followed by rinsing with ethanol and drying to obtain a Bi-2212 superconducting thin film. As shown in the figure, the prepared film is a Bi-2212-based film with a thickness reaching micrometers and exhibiting excellent superconducting properties. After the reaction was completed and the substrate was removed, the remaining solid products in the reactor and the superconducting powder obtained from washing and separation were collected. The powder was thoroughly washed with deionized water to remove molten salt and dried, followed by heat treatment to stabilize the crystalline phase; then the powder was pressed into sheets and sintered to obtain Bi-2212 ceramic blocks, realizing the recovery and reuse of the superconducting powder generated in the reaction. Finally, the washing liquid was collected and KCl crystals were recovered by evaporation crystallization; the recovered NaCl was dried and reused as a flux in the next batch.

[0061] Example 12:

[0062] Bismuth oxide (Bi₂O₃), strontium oxide (SrO), and copper oxide (CuO) were mixed in the manner of Bi₂Sr₂CuO. 6+δ The cations with 0 ≤ δ ≤ 0.5 were weighed in a stoichiometric ratio of 2:2:1, and potassium chloride (KCl) was added as flux to make the mass ratio of molten salt to precursor 2:1. The mixture was then ground in an agate mortar for 20 minutes until homogeneous. The mixed powder was evenly spread and brought into close contact with the surface of the magnesium oxide (MgO) single crystal substrate, and then placed in a quartz tube. The temperature was raised to 850℃ under normal atmospheric pressure and held for 4 hours, allowing the precursor to dissolve and migrate in the molten KCl and to form Bi₂Sr₂CuO through heterogeneous nucleation on the substrate surface. 6+δ Coating. After the reaction was completed and cooled to room temperature, the sample was removed and washed stepwise with deionized water to remove residual KCl. It was then rinsed with ethanol and dried to obtain a Bi-2201 superconducting thin film. The prepared film is a Bi-2201-based film with a thickness reaching micrometers and exhibiting excellent superconducting properties. After the reaction was completed and the substrate was removed, the remaining solid products in the reactor and the superconducting powder obtained from washing and separation were collected. The powder was thoroughly washed with deionized water to remove molten salt and dried, then heat-treated to stabilize the crystalline phase. Subsequently, the powder was pressed into sheets and sintered to obtain Bi-2201 ceramic blocks, realizing the recovery and reuse of the superconducting powder generated in the reaction. Finally, the washing liquid was collected and KCl crystals were recovered through evaporation and crystallization. The recovered KCl was dried and reused as a flux in the next batch.

[0063] Example 13:

[0064] Bismuth oxide (Bi₂O₃), strontium oxide (SrO), calcium oxide (CaO), and copper oxide (CuO) are mixed in the manner of Bi₂Sr₂Ca₂Cu₃O. 10+δThe cations with a stoichiometric ratio of 2:2:2:3, where 0 ≤ δ ≤ 0.5, were weighed and potassium chloride (KCl) was added as flux to make the mass ratio of molten salt to precursor 2:1. The mixture was then ground in an agate mortar for 20 minutes until homogeneous. The mixed powder was evenly spread and brought into close contact with the surface of a sapphire Al₂O₃ single crystal substrate, then placed in a quartz tube. The temperature was raised to 850℃ under normal atmospheric pressure and held for 4 hours, allowing the precursor to dissolve and migrate in the molten KCl and to form Bi₂Sr₂Ca₂Cu₃O₃ on the substrate surface through heterogeneous nucleation. 10+δ Coating. After the reaction was completed and cooled to room temperature, the sample was removed and washed stepwise with deionized water to remove residual KCl. It was then rinsed with ethanol and dried to obtain a Bi-2223 superconducting thin film. The prepared film is a Bi-2223-based film with a thickness reaching micrometers and exhibiting excellent superconducting properties. After the reaction was completed and the substrate was removed, the remaining solid products in the reactor and the superconducting powder obtained from washing and separation were collected. The powder was thoroughly washed with deionized water to remove molten salt and dried, then heat-treated to stabilize the crystalline phase. Subsequently, the powder was pressed into sheets and sintered to obtain Bi-2223 ceramic blocks, realizing the recovery and reuse of the superconducting powder generated in the reaction. Finally, the washing liquid was collected and KCl crystals were recovered through evaporation crystallization. The recovered KCl was dried and reused as a flux in the next batch.

[0065] Example 14:

[0066] Bismuth oxide (Bi₂O₃), strontium oxide (SrO), calcium oxide (CaO), and copper oxide (CuO) were mixed in the manner of Bi₂Sr₂CaCu₂O. 8+δ The cations with a stoichiometry of 2:2:1:2, where 0≤δ≤0.5, were weighed and mixed with a flux of potassium chloride (KCl) and sodium chloride (NaCl) to achieve a molten salt to precursor mass ratio of 1:1:1. The mixture was then ground in an agate mortar for 20 minutes until homogeneous. The mixed powder was then evenly spread and brought into close contact with the surface of a lanthanum aluminate (LaAlO3) single-crystal substrate, and placed in a quartz tube. The temperature was raised to 850℃ under normal atmospheric pressure and held for 4 hours, allowing the precursor to dissolve and migrate in the molten KCl and to form Bi2Sr2CaCu2O non-uniform nucleation sites on the substrate surface. 8+δCoating. After the reaction, the sample was cooled to room temperature and washed stepwise with deionized water to remove residual KCl and NaCl eutectic. It was then rinsed with ethanol and dried to obtain a Bi-2212 superconducting thin film. The prepared film, with Bi-2212 as the main phase, achieved a thickness of up to micrometers and exhibited excellent superconducting properties. After the reaction was complete and the substrate was removed, the remaining solid products in the reactor and the superconducting powder obtained from washing were collected. The powder was thoroughly washed with deionized water to remove molten salt and dried, then heat-treated to stabilize the crystalline phase. The powder was then pressed into sheets and sintered to obtain Bi-2212 ceramic blocks, realizing the recovery and reuse of the superconducting powder generated in the reaction. Finally, the washing liquid was collected and the KCl and NaCl eutectic was recovered through evaporation and crystallization. The recovered KCl and NaCl eutectic was dried and reused as a flux in the next batch.

[0067] Example 15:

[0068] Lanthanum oxide (La₂O₃), strontium oxide (SrO), and copper oxide (CuO) were mixed according to the La₂O₃ content. 2-x Sr x CuO 4±δ The cations with 0 ≤ x ≤ 0.5 and 0 ≤ δ ≤ 0.2 were stoichiometrically weighed, and potassium chloride (KCl) was added as flux to make the mass ratio of molten salt to precursor 2:1. The mixture was then ground in an agate mortar for 20 minutes until homogeneous. The mixed powder was evenly spread and brought into close contact with the surface of a strontium titanate (SrTiO3) single crystal substrate, and then placed in a quartz tube. The temperature was raised to 800℃ under normal pressure in an oxygen (O2) atmosphere and held for 5 hours, allowing the precursor to dissolve and migrate in molten KCl and heterogeneously nucleate on the substrate surface to form La. 2-x Sr x CuO 4±δ Coating. After the reaction was completed and cooled to room temperature, the sample was removed and washed stepwise with deionized water to remove residual KCl, followed by rinsing with ethanol and drying to obtain La. 2-x Sr x CuO 4±δ Thin film. After the reaction is complete and the substrate is removed, the remaining solid products in the reactor and the superconducting powder obtained from washing and separation are collected. The powder is thoroughly washed with deionized water to remove molten salt and dried, then heat-treated to stabilize the crystalline phase; subsequently, the powder is pressed into sheets and sintered to obtain ceramic blocks, realizing the recovery and reuse of the reaction-generated powder. Finally, the washing liquid is collected and KCl is recovered by evaporation and crystallization; the recovered KCl is dried and reused as a flux in the next batch.

[0069] Example 16:

[0070] Neodymium oxide (Nd₂O₃), cerium oxide (CeO₂), and copper oxide (CuO) were mixed according to Nd₂O₃. 2-x Ce x CuO 4±δThe cations with 0 ≤ x ≤ 0.5 and 0 ≤ δ ≤ 0.2 were stoichiometrically weighed, and potassium chloride (KCl) was added as flux to make the mass ratio of molten salt to precursor 2:1. The mixture was then ground in an agate mortar for 20 minutes until homogeneous. The mixed powder was uniformly spread and brought into close contact with the surface of a neodymium gallium oxide (NdGaO3) single crystal substrate, and then placed in a quartz tube. The temperature was raised to 800℃ under an argon atmosphere at ambient pressure and held for 5 hours to complete phase formation and film formation. This allowed the precursor to dissolve and migrate in molten KCl and to form NdGaO3 through heterogeneous nucleation on the substrate surface. 2-x Ce x CuO 4±δ Coating. After the reaction was completed and cooled to room temperature, the sample was removed and washed stepwise with deionized water to remove residual KCl, followed by rinsing with ethanol and drying to obtain Nd. 2-x Ce x CuO 4±δ The thin film exhibits superconducting properties. After the reaction is complete and the substrate is removed, the remaining solid products in the reactor are collected along with the powder obtained from washing and separation. The powder is then washed to remove salt, dried, and subjected to heat treatment to stabilize the crystalline phase before being pressed and sintered to achieve powder recycling and reuse. Finally, the washing liquid is collected and KCl is recovered through evaporation and crystallization for recycling.

[0071] Example 17:

[0072] Calcium oxide (CaO), strontium oxide (SrO), and copper oxide (CuO) were mixed according to the following formula: 1-x Sr x CuO2, with cations stoichiometrically weighed (0≤x≤1), is mixed with potassium chloride (KCl) as flux to achieve a molten salt to precursor mass ratio of 1:1. The mixture is then ground in an agate mortar for 20 minutes until homogeneous. The powder is evenly spread and brought into close contact with the surface of a lanthanum aluminate (LaAlO3) single-crystal substrate, then placed in a quartz tube. The tube is heated to 900℃ under normal pressure and maintained for 3 hours in an oxygen (O2) atmosphere, allowing the precursor to dissolve and migrate in the molten KCl and heterogeneously nucleate on the substrate surface to form CaO. 1-x Sr x CuO2 coating. After the reaction, the sample was cooled to room temperature, removed, and washed stepwise with deionized water to remove residual KCl, followed by rinsing with ethanol and drying to obtain Ca. 1-x Sr x CuO2 thin film. After the reaction is complete and the substrate is removed, the generated powder is collected and recovered. After washing, desalting, drying and heat treatment, it is pressed and sintered to achieve powder recycling and reuse. The washing liquid is evaporated and crystallized to recover KCl and recycled.

[0073] Example 18:

[0074] Nickel-tungsten strip (Ni-W) was selected, and a cerium dioxide (CeO2) buffer layer was pre-fabricated on its surface. Barium oxide (BaO), calcium oxide (CaO), and copper oxide (CuO) were then mixed according to Cu...1-x C x Ba2Ca3Cu4O 11+δ The system, where 0≤x≤1 and 0≤δ≤0.5, required stoichiometric cations were weighed. A eutectic mixture of potassium carbonate (K₂CO₃) and sodium carbonate (Na₂CO₃) was added as the main fluxing system, and the mixture was prepared at a mass ratio of K₂CO₃:Na₂CO₃:precursor = 1:1:1. The mixture was ground in an agate mortar for 20 minutes until homogeneous. The mixed powder was evenly spread and brought into close contact with the CeO₂ buffer layer surface, then placed in a quartz tube. The temperature was raised to 900℃ and held for 4 hours under a mixed atmosphere of carbon dioxide (CO₂) and oxygen (O₂) at ambient pressure, allowing the precursor to dissolve and migrate in the molten carbonate eutectic system and heterogeneously nucleate on the buffer layer surface to form a (Cu,C)-1234 related coating. After the reaction, the sample was cooled to room temperature, removed, and washed stepwise with deionized water to remove residual molten salt. It was then rinsed with ethanol and dried to obtain the coating structure. After the reaction is complete and the strip is removed, the remaining solid products in the reactor and the powder obtained from washing and separation are collected. The powder is washed to remove salt, dried, and then heat-treated to stabilize the crystalline phase before being pressed into sheets and sintered, thus achieving powder recycling and reuse. Finally, the washing liquid is collected and the K2CO3 and Na2CO3 eutectic system is recovered through evaporation and crystallization. After drying, it is reused as a fluxing system for the next batch.

[0075] Example 19:

[0076] Bismuth oxide (Bi₂O₃), strontium oxide (SrO), calcium oxide (CaO), and copper oxide (CuO) were mixed in the manner of Bi₂Sr₂CaCu₂O. 8+δThe cation stoichiometry was 2:2:1:2, and a mixture of potassium chloride (KCl) and sodium chloride (NaCl) flux was added to achieve a KCl:NaCl:precursor mass ratio of 1:1:1. The mixture was ground in an agate mortar for 20 minutes until homogeneous. Porous or foamed alumina (Al2O3) ceramic was selected as a three-dimensional carrier. The mixed powder was impregnated and coated to ensure full contact with the porous framework surface. The carrier was placed in a quartz tube, and the temperature was raised to 850℃ under normal atmospheric pressure and held for 4 hours. This allowed the precursor to dissolve and migrate in the molten KCl-NaCl eutectic system, forming a Bi-2212 coating layer on the framework surface through heterogeneous nucleation. After the reaction, the sample was cooled to room temperature, removed, and washed stepwise with deionized water to remove residual KCl and NaCl eutectic. It was then rinsed with ethanol and dried to obtain a coating structure with Bi-2212 as the main phase. The resulting coating layer thickness reached the micrometer scale and exhibited superconducting transition characteristics. After the reaction was completed and the support was removed, the remaining solid products in the reactor were collected along with the superconducting powder obtained through washing and separation. The powder was thoroughly washed with deionized water to remove molten salt and dried, then heat-treated to stabilize the crystalline phase. Subsequently, the powder was pressed into sheets and sintered to obtain Bi-2212 ceramic blocks, realizing the recovery and reuse of the superconducting powder generated in the reaction. Finally, the washing liquid was collected and the KCl and NaCl eutectic was recovered by evaporation and crystallization. The recovered KCl and NaCl eutectic was dried and reused as a fluxing system for the next batch.

[0077] Example 20:

[0078] Alumina microspheres modified with cerium dioxide (CeO2) were selected as the carrier. Bismuth oxide (Bi2O3), strontium oxide (SrO), calcium oxide (CaO), and copper oxide (CuO) were mixed in the manner of Bi2Sr2CaCu2O. 8+δThe cation was stoichiometrically weighed, and potassium chloride (KCl) was added as flux to achieve a molten salt to precursor mass ratio of 2:1. The mixture was ground in an agate mortar for 20 minutes until homogeneous. The mixed powder was applied to the surface of the microsphere array using a spreading or roller coating method to ensure full contact. The support was placed in a quartz tube, and the temperature was raised to 850℃ under normal air pressure and held for 4 hours. This allowed the precursor to dissolve and migrate in the molten KCl, forming a Bi-2212 coating on the microsphere array surface through heterogeneous nucleation. After the reaction, the sample was cooled to room temperature, removed, and washed stepwise with deionized water to remove residual KCl. It was then rinsed with ethanol and dried to obtain a microsphere array surface coating structure with Bi-2212 as the main phase. The prepared coating layer achieved a thickness on the micrometer scale and exhibited superconducting transition characteristics. After the reaction was complete and the microsphere array support was removed, the remaining solid products in the reactor were collected along with the superconducting powder obtained from washing and separation. The powder was thoroughly washed with deionized water to remove molten salt and dried, then heat-treated to stabilize the crystalline phase. Subsequently, the powder was pressed into sheets and sintered to obtain Bi-2212 ceramic blocks, achieving the recovery and reuse of the superconducting powder generated in the reaction. Finally, the washing liquid was collected and KCl was recovered through evaporation and crystallization; the recovered KCl was dried and reused as a flux in the next batch.

Claims

1. A method for preparing a molten salt-assisted copper-based coated superconductor, characterized in that, Includes the following steps: 1) Based on the application scenario of the coated superconductor, select copper-based oxide superconductor materials and carriers, and design the corresponding molten salt composition, synthesis chemical environment, and synthesis thermodynamic conditions; 2) Weigh the corresponding metal element precursor powder according to the cation stoichiometry in the selected copper-based oxide superconducting material, mix it with the molten salt in the optimized ratio, and then place it evenly on the surface of the selected carrier. 3) By designing the external reaction atmosphere of molten salt, the chemical environment of synthesis and the valence state of material ions are controlled. The precursor metal ions are heated to a certain temperature so that they dissolve in the molten salt and are deposited and grown in a non-uniform nucleation manner on the surface of a carrier with a similar two-dimensional crystal structure and lattice parameters to the copper-based oxide superconducting material. The thickness of the coating conductor is controlled by the reaction time. 4) After the superconductor coating reaches the required thickness, the growth device is cooled to near room temperature. The prepared copper-based oxide coated superconductor composite material is then removed and residual flux is removed by solvent washing. 5) Collect the remaining reaction products in the reaction device, separate the synergistically generated copper-based oxide superconducting material powder products by solvent washing, and separate the used flux and washing solvent from the recovered solvent to achieve recycling.

2. The method for preparing a molten salt-assisted copper-based coated superconductor as described in claim 1, characterized in that, The copper-based oxide superconductor material includes: Ca 1-x Sr x CuO2, where 0 ≤ x ≤ 1; La 2-x Sr x CuO 4±δ Where 0 ≤ x ≤ 0.5 and 0 ≤ δ ≤ 0.2, Nd 2-x Ce x CuO 4±δ Where 0 ≤ x ≤ 0.5 and 0 ≤ δ ≤ 0.2; Bi2Sr2CuO 6+δ That is, Bi-22O1, where 0≤δ≤0.5; Bi2Sr2CaCu2O 8+δ That is, Bi-2212, where 0≤δ≤0.5; Bi2Sr2Ca2Cu3O 10+δ That is, Bi-2223, where 0≤δ≤0.5, Cu 1-x C x Ba2Ca3Cu4O 11+δ That is, (Cu,C)-1234, where 0≤x≤1 and 0≤δ≤0.

5.

3. The method for preparing molten salt-assisted copper-based coated superconductors as described in claim 1, characterized in that, The carrier surface material system in contact with the coated superconductor includes: perovskite oxide, spinel oxide, quartz, magnesium oxide, gallium oxide, aluminum oxide, cerium oxide, mica, silicon, silicon carbide, germanium, gallium arsenide, and alloys; wherein the preferred perovskite oxides are: strontium titanate (SrTiO3), lanthanum aluminate (LaAlO3), and neodymium gallium oxide (NdGaO3); the preferred spinel oxides are: magnesium aluminum spinel, zinc aluminum spinel, and magnesium gallium spinel; and the preferred alloy is: nickel-tungsten alloy Ni-W / RABiTS. The materials used in the process include strips, Hastelloy / Ni-based corrosion-resistant alloys, Inconel / Ni-Cr-based superalloys, 316L stainless steel, copper and copper-based alloys Cu / Cu-Ni / Monel, titanium and titanium alloys Ti / Ti-6Al-4V, and other engineered heat-resistant alloys. The surfaces of the above materials have similar two-dimensional crystal structures and lattice parameters to the specific crystal planes of the copper-based oxide superconducting material to be grown, which can trigger the non-uniform nucleation and growth of copper-based superconducting oxides on them. The carrier morphology includes single crystals, polycrystalline materials, porous ceramic bodies, whiskers or fibers of the above materials, or other materials with surface modifications of the above materials.

4. The method and apparatus for preparing molten salt-assisted copper-based coated superconductors as described in claim 1, characterized in that, The substrate morphology of the coated superconductor includes: a single-crystal substrate for growing the coated superconductor film material, including strontium titanate (SrTiO3) and lanthanum aluminate (LaAlO3); a polycrystalline substrate for growing the coated superconductor film material, including polycrystalline alumina (Al2O3), zirconium oxide-stabilized yttrium oxide (YSZ), polycrystalline magnesium oxide (MgO), and glass ceramic; the substrate for growing the coated superconductor film material contains a heterogeneous buffer layer, including cerium dioxide (CeO2), zirconium oxide-stabilized yttrium oxide (YSZ), lanthanum nickelate (LaNiO3), strontium ruthenium ruthenium oxide (SrRuO3), barium zirconate (BaZrO3), magnesium oxide (MgO), titanium nitride (TiN), and an amorphous / oriented buffer layer system formed by ion beam assisted deposition (IBAD), wherein the amorphous / oriented buffer layer system includes I BAD-CeO2 and cerium dioxide CeO2 buffer layers; bulk carriers for growing coated superconductor coatings, including alumina Al2O3 bulk, zirconia ZrO2 ceramic bulk, titanium dioxide TiO2 bulk, glass-ceramic and porous ceramic / foam ceramic porous bodies, densified ceramic substrates or metal / ceramic composite bulks; ceramic fiber carriers for growing coated superconductor coating fibers, including α-alumina ceramic fibers, zirconia or zirconia-stabilized yttrium oxide fibers, silicon carbide fibers SiC, and mullite-based ceramic fibers; and tape carriers for growing coated superconductor coatings, including metal tapes and metal foils, specifically containing nickel-tungsten tapes Ni-W / RABiTS and stainless steel tapes or copper tapes / copper foils.

5. The method for preparing a molten salt-assisted copper-based coated superconductor as described in claim 1, characterized in that, The molten salt comprises: alkali metal halides, alkali metal carbonates, alkali metal sulfates, and their eutectics. The alkali metal halides include potassium chloride (KCl), sodium chloride (NaCl), lithium chloride (LiCl), rubidium chloride (RbCl), cesium chloride (CsCl), potassium bromide (KBr), sodium bromide (NaBr), lithium fluoride (LiF), potassium fluoride (KF), KCl-NaCl eutectic, KCl-RbCl eutectic, KCl-CsCl eutectic, NaCl-RbCl eutectic, NaCl-CsCl eutectic, and LiCl-KCl eutectic. The alkali metal carbonates include potassium carbonate (K2CO3), sodium carbonate (Na2CO3), and K2CO3-Na2CO3 eutectic. The alkali metal carbonates include sodium sulfate (Na2SO4), potassium sulfate (K2SO4), NaCl-Na2SO4 eutectic, and KCl-K2SO4 eutectic.

6. The method and apparatus for preparing a molten salt-assisted copper-based coated superconductor as described in claim 1, characterized in that, The external reaction atmosphere design of the molten salt includes: oxygen O2, air, ozone O3, nitrogen N2, inert gas, carbon dioxide CO2, and a mixture of the above gases; for different copper-based oxide superconducting material systems, the valence state balance of copper and related cations can be adjusted by atmosphere selection, the oxygen content δ of the target phase can be precisely controlled, and the thermal stability of the carbonate or carbon-oxygen structure can be maintained when using carbonate molten salt or carbon-containing reservoir structure.

7. The method for preparing a molten salt-assisted copper-based coated superconductor as described in claim 1, characterized in that, The coordinated design of thermodynamic and kinetic parameters includes the coordinated optimization of reaction temperature, reaction pressure, reaction time, and the ratio of molten salt components to precursors. The specific selection of reaction temperature should be determined based on the melting point and eutectic characteristics of the molten salt used, the thermodynamic formation region of the target copper-based superconducting phase, the thermal decomposition and diffusion characteristics of the precursor, and the selected atmosphere factors. Combined with the design of the reaction temperature within the range of 500-1100 degrees Celsius, the selected molten salt is placed within the window of melting and generating effective liquid phase migration, and the reaction temperature is linked with the selected atmosphere. This allows for fine adjustment of the liquid phase existence time, the solubility and migration rate of the precursor in the molten salt, the nucleation density and grain growth rate, the loss rate of volatile components, and the diffusion and reabsorption behavior of oxygen. This enables controllable adjustment of coating thickness, grain size and morphology, density, porosity, stress state, and phase composition.

8. The method for preparing a melt-assisted copper-based coated superconductor as described in claim 1, characterized in that, The method for recovering molten salt and generating superconducting powder mainly includes stepwise washing and solid-liquid separation of reaction products, dissolution and recrystallization recovery of molten salt, and collection and reuse of superconducting powder. After the reaction, the product is washed with deionized water or alcohol solvent to dissolve and remove soluble molten salt. Solid-liquid separation is achieved by filtration or centrifugation to obtain superconducting powder. The resulting molten salt-containing washing liquid is recovered and recycled by evaporation crystallization or membrane separation. The separated superconducting powder can be directly used as functional powder or used in subsequent forming and sintering processes after drying and necessary heat treatment, thereby achieving synergistic recovery of molten salt medium and superconducting powder and reducing preparation costs and environmental impact.

9. The application of the molten salt-assisted copper-based coated superconductor as described in claim 1, characterized in that, The applications of the coated superconductors prepared by this method mainly include quantum devices, superconducting electronic devices, coated superconducting wires and tapes, power electronic devices, high-field magnet coils, flexible superconducting cables, braidable transmission lines, bending sensors, microwave and terahertz devices, sensor arrays, and multifunctional electromagnetic structures. The powder prepared by this method can be further sintered to form bulk or textured ceramic materials, or combined with metal, ceramic, and polymer matrices to construct superconducting composite conductors, functionally graded materials, electromagnetic shielding structures, and thermal management functions. This method can be used to fabricate and adapt diverse structural morphologies, including continuous thin and thick film structures, fiber or wire surface coating structures, microsphere or particle array coating structures, porous or foam block coating structures, heterogeneous multilayer and interface engineering structures, and micro / nano patterned coating structures. These structures can meet the needs of fabricating Josephson junction devices, coated conductors and engineered magnets, flexible and braidable superconducting devices, microstructured electromagnetic functional devices, multilayer interface pinning reinforcement structures, and micro / nano device integration applications.

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