A method for mass production of high purity superconducting target material

Abstract

The present application relates to a kind of methods for preparing high-purity superconducting target material in large quantities.The present application first finds out that in the calcination process of large-scale preparation of superconducting target material, CO2 exhaust gas cannot be discharged and the temperature field uniformity is poor, which leads to the decline of the superconducting performance of the target material.Based on this, the present application proposes three processes for preparing high-purity superconducting target material in large quantities, constructs a forced convection field covering the entire reaction cavity, greatly improves the reaction efficiency and uniformity, significantly improves the superconducting performance of the target material, and overcomes the technical defects of poor performance in the large-scale preparation of superconducting target material in the field;Among them, the side dispersion process is simple and easy to realize large-scale production;The multi-hole ceramic carrier from the bottom air process can improve the powder accumulation thickness and improve the production efficiency;The bottom pulse air flow spiral rising process has strong exhaust capacity and avoids CO2 accumulation more thoroughly.

Description

Technical Field

[0001] This invention belongs to the field of second-generation high-temperature superconducting technology and relates to a method for mass production of high-purity superconducting targets. Background Technology

[0002] The large-scale production of second-generation high-temperature superconducting tapes urgently requires large-area, high-performance REBCO ceramic targets. These targets are typically used in pulsed laser deposition (PLD) or magnetron sputtering, and their uniformity, stoichiometric accuracy, and high density directly determine the superconducting properties of the thin film. Currently, traditional processes (such as patent CN119263808A) prepare superconducting powders using rare earth oxides, barium carbonate, and copper oxide as raw materials. This method mainly involves ball milling and multiple calcinations, with the advantage of relatively straightforward process steps, suitable for scale-up production. However, the repeated crushing and calcination processes for purification can easily lead to uneven distribution of copper oxide, forming enriched small regions, resulting in an uneven target composition and the inclusion of other impurities. Ultimately, the composition of the film deposited using this target will deviate from the expected ratio, directly resulting in unstable superconducting properties (especially the critical current density Jc), posing a significant challenge to improving tape yield and ensuring performance consistency. To improve target uniformity, the industry typically employs the following traditional methods, but each has its limitations: For example, the co-precipitation method involves completely dissolving the raw materials in acid according to a stoichiometric ratio, adding oxalic acid while controlling the pH value, and controlling the precipitation of all components. The superconducting powder is then obtained through calcination. As described in patent CN118930225A, the raw materials are dissolved in an acid solution, where the acid solution is one or more combinations of hydrochloric acid, nitric acid, or sulfuric acid, to obtain a mixed solution. Excess oxalic acid is then added, and the pH value is adjusted with ammonia. After heating and aging to generate a precipitate, the powder undergoes washing, drying, and calcination to obtain REBCO single-phase powder. However, the method used to prove that the obtained powder is single-phase is not specified. The provided XRD pattern shows a strong diffraction peak of secondary copper oxide at approximately 35.5°, and two diffraction peaks of the 211 phase (Y2BaCuO5) at approximately 30°, which do not belong to the YBCO phase. This indicates that this method does not yield single-phase REBCO powder.

[0003] For example, the sol-gel method involves dissolving raw materials in acetic acid (or using acetate) according to a stoichiometric ratio. The solution is then concentrated into a gel by stirring at a specific temperature and adjusting the pH. The gel is then calcined to obtain superconducting powder. As described in patent CN101492291A, nitrates are used as a raw material, urea is added, and water is evaporated to form a gel. This gel is then sintered multiple times to obtain superconducting phase powder. However, the gel contains a large amount of nitrogen (N), which decomposes at high temperatures to produce large amounts of harmful NO2 and other waste gases. This requires additional exhaust gas treatment equipment, resulting in high costs and hindering cost reduction and efficiency improvement in large-scale industrial production.

[0004] However, a key challenge remains in large-scale production: the difficulty in avoiding microscopic chemical segregation, particularly the localized enrichment of copper (Cu). This problem stems primarily from two aspects: 1. Initial uneven mixing: Traditional dry mixing or ordinary ball milling struggles to achieve uniform mixing of raw materials at the submicron / nanometer scale, and compositional fluctuations create potential problems for subsequent reactions. 2. Selective behavior during calcination: Significant differences in diffusion rates and volatility among components at high temperatures (e.g., CuO is prone to volatility and migration) amplify initial inhomogeneities, leading to Cu enrichment at grain boundaries or in localized areas, forming harmful impurity phases such as CuO and BaCuO2.

[0005] Therefore, the technical problem to be solved by this invention is how to optimize the calcination process in large-scale production to improve reaction efficiency and uniformity, and to avoid the presence of BaCO3 impurity phase residues in the target material, thereby improving the superconducting performance of the target material. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for mass production of high-purity superconducting targets. This invention is the first to discover that during the calcination process of large-scale superconducting target production, problems such as the inability to expel CO2 waste gas and poor temperature field uniformity exist, leading to a decline in the superconducting performance of the target material. Based on this, this invention proposes three processes for mass production of high-purity superconducting targets, constructing a forced convection field covering the entire reaction chamber, which greatly improves reaction efficiency and uniformity, significantly enhancing the superconducting performance of the target material and overcoming the technical defects of poor performance in large-scale superconducting target production that have existed in the field. Among them, the side-dispersion inlet process is simple and easy to scale up; the bottom-ventilation process using a porous ceramic carrier can increase the powder accumulation thickness and improve production efficiency; and the bottom pulse-type ventilation-airflow spiral ascent process has strong exhaust capacity and more thoroughly avoids CO2 accumulation.

[0007] The objective of this invention can be achieved through the following methods: In a first aspect, the present invention provides a method for mass production of high-purity superconducting targets, the method employing a side-diffusion injection process, specifically including the following steps: S1. After spray granulation of a slurry containing a large amount of rare earth oxides, copper source and barium source, preheated air or oxygen is introduced by side dispersion and calcined to obtain powder. S2. Crush the powder and press it onto the target to obtain the final product.

[0008] In one embodiment of the present invention, in step S1, the "large quantity" refers to a quantity of 50 kilograms or more.

[0009] In one embodiment of the present invention, in step S1, the rare earth oxide includes one of europium oxide, gadolinium oxide, samarium oxide, and yttrium oxide; the copper source includes one of copper oxide and copper nitrate; and the barium source includes one of barium carbonate, barium oxide, and barium hydroxide.

[0010] As one embodiment of the present invention, in step S1, the molar ratio of the rare earth oxide, copper source and barium source is (0.5±0.05):(2±0.2):(3±0.3).

[0011] As one embodiment of the present invention, in step S1, the method for preparing the slurry containing a large amount of rare earth oxides, copper source and barium source is as follows: a large amount of rare earth oxides, copper source and barium source are weighed as raw materials and milled to obtain the slurry.

[0012] Furthermore, the ball mill used in the sand mill has a diameter of 0.2~0.5mm and is made of zirconium oxide.

[0013] Furthermore, the dispersion medium used in the sand milling includes ultrapure water, and the dispersant includes one or more of the following aqueous dispersants: ammonium polyacrylate, polyacrylic acid, polycarboxylate, alginate, etc.; the amount of the dispersant added is 0.2 wt.% to 2 wt.%.

[0014] Furthermore, the grinding time is 0.5 to 3 hours.

[0015] As one embodiment of the present invention, in step S1, the inlet air temperature is 200~250℃, the outlet air temperature is 90~120℃, and the rotation speed of the atomizer is 15000~24000RPM.

[0016] In one embodiment of the present invention, in step S1, the preheating temperature is 300~500℃.

[0017] The purpose of preheating the air in this invention is to eliminate cold source disturbances caused by cold air, ensuring extreme temperature stability and spatial uniformity in the core area, thereby guaranteeing the stable and smooth progress of reactions in all spatially distributed areas. Without a stable temperature field, any precise chemical ratios and mixing process advantages may be lost due to uneven reaction temperatures, ultimately leading to the segregation of elements such as Cu in the product, the formation of impurity phases, and the non-reproducibility of batch performance. If the preheating temperature is below 300℃, the effect of eliminating cold sources will not be achieved, resulting not only in energy loss but also in a sudden drop in local temperature and uneven spatial temperature within the furnace. This thermal disturbance will severely disrupt the uniform thermodynamic conditions necessary for the solid-phase reaction of multi-component oxides, leading to fluctuations in reaction rates and uneven diffusion, which in turn exacerbates the microscopic segregation of elements such as copper (Cu) and the formation of impurity phases, directly affecting the chemical composition consistency of the target material and the final superconducting performance.

[0018] In one embodiment of the present invention, in step S1, the flow rate of the air or oxygen is 100-1000 L / min.

[0019] In this invention, if the flow rate is too low, an effective oxidizing atmosphere cannot be established, and reaction byproducts cannot be removed in time. This mainly manifests as insufficient local oxygen partial pressure inside the furnace, leading to the reduction of barium (Ba) and copper (Cu). Specifically, the reduction of Ba occurs under oxygen-deficient conditions. 2+ It may be reduced to form non-superconducting, stable BaO or react with CO2 to form BaCO3, which would severely hinder the formation of the RE-123 phase; Cu reduction: Cu 2+ (CuO) will be reduced to Cu + Even metallic Cu, Cu2O and Cu are extremely difficult to completely re-oxidize in subsequent processes, and they react with BaO to form stable impurity phases (such as BaCu2O2), permanently disrupting the stoichiometry and crystal structure of the superconducting phase. The reaction process releases CO2; if the flow rate is too low, these gases cannot be quickly removed from the reaction zone, forming a "gas film" on the surface of the powder particles. This hinders the diffusion of oxygen into the particle interior and the contact of fresh reactants, significantly slowing down or even inhibiting the solid-phase reaction. For example, the decomposition of BaCO3 (BaCO3→BaO+CO2) is a reversible process. If CO2 cannot be removed in time, the reaction will proceed to the left (in the direction of BaCO3 formation), resulting in incomplete decomposition of BaCO3, which ultimately remains in the target material as a harmful impurity phase.

[0020] In one embodiment of the present invention, in step S1, the calcination temperature is 930~960℃ and the time is 40~80h.

[0021] In one embodiment of the present invention, in step S2, the particle size of the crushed powder is 5~25μm.

[0022] In one embodiment of the present invention, in step S2, the hot-pressing temperature of the pressure target is 820~920℃, the hot-pressing holding time is 0.5-2h, the hot-pressing pressure is 5~20MPa, and the hot-pressing atmosphere is vacuum or inert gas, wherein the vacuum degree is less than 10Pa, and the inert gas includes nitrogen and argon. A slight positive pressure is maintained in the cavity during ventilation.

[0023] This invention proposes a "preheated air / oxygen - high flow rate - side diffusion introduction" scheme, which constructs a forced convection field covering the entire reaction chamber. This can continuously and rapidly strip CO2 generated by reactions such as BaCO3 decomposition from the surface of powder particles and carry it away from the reaction zone, thereby maintaining an extremely low CO2 partial pressure at the reaction interface. This avoids reaction inhibition and BaCO3 impurity phase residue caused by local CO2 accumulation. At the same time, the preheated air / oxygen significantly reduces the temperature difference between the inlet gas and the high-temperature zone of the furnace, fundamentally eliminating the local temperature drop caused by cold gas acting as a "heat sink". Combined with the spherical particles after spray granulation, it provides a large number of gas channels. At the same time, each sphere is an individual target material reaction center, which greatly improves the reaction efficiency and reaction uniformity, thereby significantly improving the superconducting performance of the target material.

[0024] In principle, the high-flow-rate gas, combined with side-diffuse inlet, first constructs a forced convection field covering the entire reaction chamber. This flow field acts like a highly efficient "gas sweeping system," continuously and rapidly stripping CO2 generated by reactions such as BaCO3 decomposition from the surface of powder particles and carrying it away from the reaction zone, thereby maintaining an extremely low CO2 partial pressure at the reaction interface. This thermodynamically drives the forward BaCO3 decomposition reaction, avoiding reaction inhibition and BaCO3 impurity phase residue caused by local CO2 accumulation, and ensuring stoichiometric accuracy. Simultaneously, preheating the gas to 300-500℃ before introduction is crucial for controlling thermal disturbance. Preheating significantly reduces the temperature difference between the inlet gas and the high-temperature zone (950℃) of the furnace, fundamentally eliminating the localized temperature drop caused by cold gas acting as a "heat sink." The preheated high-flow-rate gas is uniformly introduced from the side, creating a strong "gas stirring" effect throughout the furnace. This forces heat to be rapidly transferred from the high-temperature zone to the low-temperature zone under convection, thereby achieving dynamic temperature homogenization in the three-dimensional direction of the reaction space. This provides all materials with completely consistent heat. Combined with the granulated spherical particles, a large number of gas channels are provided. At the same time, each sphere is an individual target material reaction center, which greatly improves the reaction efficiency and reaction uniformity.

[0025] The aforementioned synergistic mechanism ultimately translates into a comprehensive improvement in the performance of the target material. Chemically, extremely high purity of the main phase and precise stoichiometry are achieved, and the proportions of key metal elements are strictly guaranteed. Microscopically, the uniformity of the reaction environment promotes fine grains with a normal distribution, effectively eliminating structural defects and density gradients. Ultimately, the superconducting thin films deposited using this target material exhibit superior and more consistent superconducting properties, including higher critical current densities and sharper superconducting transitions, due to the precise and uniform transfer of composition to the substrate.

[0026] Secondly, this invention provides a method for mass production of high-purity superconducting targets, wherein the method employs a bottom-venting process using a porous ceramic carrier, specifically including the following steps: S1. After spray granulation of a slurry containing a large amount of rare earth oxides, copper source and barium source, the slurry is placed in a porous ceramic carrier and preheated air or oxygen is introduced from bottom to top for calcination to obtain powder. S2. Crush the powder and press it onto the target to obtain the final product.

[0027] In one embodiment of the present invention, in step S1, the "large quantity" refers to a quantity of 50 kilograms or more.

[0028] In one embodiment of the present invention, in step S1, the rare earth oxide includes one of europium oxide, gadolinium oxide, samarium oxide, and yttrium oxide; the copper source includes one of copper oxide and copper nitrate; and the barium source includes one of barium carbonate, barium oxide, and barium hydroxide.

[0029] As one embodiment of the present invention, in step S1, the molar ratio of the rare earth oxide, copper source and barium source is (0.5±0.05):(2±0.2):(3±0.3).

[0030] As one embodiment of the present invention, in step S1, the method for preparing the slurry containing a large amount of rare earth oxides, copper source and barium source is as follows: a large amount of rare earth oxides, copper source and barium source are weighed as raw materials and milled to obtain the slurry.

[0031] Furthermore, the ball mill used in the sand mill has a diameter of 0.2~0.5mm and is made of zirconium oxide.

[0032] Furthermore, the dispersion medium used in the sand milling includes ultrapure water, and the dispersant includes one or more of the following aqueous dispersants: ammonium polyacrylate, polyacrylic acid, polycarboxylate, alginate, etc.; the amount of the dispersant added is 0.2 wt.% to 2 wt.%.

[0033] Furthermore, the grinding time is 0.5 to 3 hours.

[0034] As one embodiment of the present invention, in step S1, the inlet air temperature is 200~250℃, the outlet air temperature is 90~120℃, and the rotation speed of the atomizer is 15000~24000RPM.

[0035] As one embodiment of the present invention, in step S1, the porous ceramic includes open-cell alumina foam ceramic.

[0036] This invention adjusts the carrier for the powder to be fired to a porous ceramic, so that gas is transmitted to the powder through the porous ceramic. The gas is preheated in the middle process, and uniform gas flow is achieved through pores at specific locations.

[0037] In one embodiment of the present invention, in step S1, the preheating temperature is 300~500℃.

[0038] In one embodiment of the present invention, in step S1, the flow rate of the air or oxygen is 100-1000 L / min.

[0039] In one embodiment of the present invention, in step S1, the calcination temperature is 930~960℃ and the time is 40~80h.

[0040] In one embodiment of the present invention, in step S2, the particle size of the crushed powder is 5~25μm.

[0041] In one embodiment of the present invention, in step S2, the hot-pressing temperature of the pressure target is 820~920℃, the hot-pressing holding time is 0.5-2h, the hot-pressing pressure is 5~20MPa, and the hot-pressing atmosphere is vacuum or inert gas, wherein the vacuum degree is less than 10Pa, and the inert gas includes nitrogen and argon. A slight positive pressure is maintained in the cavity during ventilation.

[0042] This invention can also select the "preheated air / oxygen - high flow rate - bottom ventilation using a porous ceramic carrier" scheme. Using porous ceramic as the carrier for the powder to be fired, and combined with spherical powder prepared by spray granulation as a foundation, a high-quality sintering environment with uniform gas distribution and stable temperature promotes reaction is constructed. First, the powder to be fired is made into spherical particles using a spray granulation process. After the spherical powder is stacked, it forms regular, interconnected, and uniformly distributed permeable gap channels between the particles, completely solving the problems of pore blockage, ventilation blind spots, and uneven gap density that easily occur with irregular powder stacking. This provides a stable and sufficient permeable foundation for subsequent gas penetration and flow, which is the core prerequisite for achieving uniform ventilation throughout the entire process and ensuring sufficient gas-solid contact. Second, during the process, the reaction gas achieves uniform gas distribution throughout the bottom area via the porous ceramic carrier. Furthermore, the gas can be preheated during the process of penetrating the porous ceramic, avoiding the problem of low-temperature direct airflow in traditional direct ventilation, and preventing localized temperature drops in the furnace and materials. The preheated, high-flow-rate gas penetrates the spherical powder material layer from bottom to top, effectively carrying away the CO2 generated by the material reaction and rapidly expelling it upwards. Simultaneously, the porous ceramic's permeable structure, combined with the regular permeable channels formed by the spherical powder, eliminates any dead zones, completely preventing the accumulation of waste gas in the material gaps. This effectively eliminates the inhibitory effect of CO2 on the sintering forward reaction, ensuring a continuous and stable forward reaction. At the same time, the preheated gas diffuses out through the micropores of the porous ceramic, exhibiting uniform airflow distribution and a gentle flow velocity. This fully drives the heat circulation and exchange within the furnace, effectively breaking down localized high and low temperature zones in the furnace and material layer, achieving overall furnace temperature field balance and significantly improving temperature stability. The uniform and stable atmosphere and balanced overall temperature field, combined with the dual permeable structure of full-area gas distribution at the bottom of porous ceramics and gas guidance between spherical powder gaps, allow every part of the material to be burned in the furnace to be in full and uniform contact with the reaction gas. This makes the heating conditions and gas-solid reaction conditions of all materials highly consistent, ultimately greatly improving the overall reaction rate and uniformity of powder sintering, and effectively improving the consistency and quality stability of the sintered product.

[0043] Compared to traditional sintering support structures, the combination of a porous ceramic carrier and spray-granulated spherical powder offers the following technical advantages: The accumulation of spherical powder forms regular and interconnected permeable channels, effectively avoiding uneven powder accumulation, blockage, and dead zones, providing a stable structural foundation for uniform gas distribution. Gas is fully dispersed throughout the bottom of the porous ceramic carrier and preheated during its flow, preventing localized temperature drops caused by direct low-temperature airflow and resulting in a more uniform temperature distribution within the furnace, eliminating localized high and low temperature differences. The uniform upward airflow effectively removes CO2 generated during sintering, preventing waste gas from accumulating in the material gaps, effectively relieving the inhibitory effect of CO2 on the forward sintering reaction, and ensuring continuous and stable reaction.

[0044] Thirdly, this invention provides a method for mass production of high-purity superconducting targets, the method employing a bottom-pulse ventilation-airflow spiral ascent process, specifically including the following steps: S1. After spray granulation of a slurry containing a large amount of rare earth oxides, copper source and barium source, preheated air or oxygen is introduced in a bottom pulse manner and the airflow is kept spiraling upward for calcination to obtain powder. S2. Crush the powder and press it onto the target to obtain the final product.

[0045] In one embodiment of the present invention, in step S1, the "large quantity" refers to a quantity of 50 kilograms or more.

[0046] In one embodiment of the present invention, in step S1, the rare earth oxide includes one of europium oxide, gadolinium oxide, samarium oxide, and yttrium oxide; the copper source includes one of copper oxide and copper nitrate; and the barium source includes one of barium carbonate, barium oxide, and barium hydroxide.

[0047] As one embodiment of the present invention, in step S1, the molar ratio of the rare earth oxide, copper source and barium source is (0.5±0.05):(2±0.2):(3±0.3).

[0048] As one embodiment of the present invention, in step S1, the method for preparing the slurry containing a large amount of rare earth oxides, copper source and barium source is as follows: a large amount of rare earth oxides, copper source and barium source are weighed as raw materials and milled to obtain the slurry.

[0049] Furthermore, the ball mill used in the sand mill has a diameter of 0.2~0.5mm and is made of zirconium oxide.

[0050] Furthermore, the dispersion medium used in the sand milling includes ultrapure water, and the dispersant includes one or more of the following aqueous dispersants: ammonium polyacrylate, polyacrylic acid, polycarboxylate, alginate, etc.; the amount of the dispersant added is 0.2 wt.% to 2 wt.%.

[0051] Furthermore, the grinding time is 0.5 to 3 hours.

[0052] As one embodiment of the present invention, in step S1, the inlet air temperature is 200~250℃, the outlet air temperature is 90~120℃, and the rotation speed of the atomizer is 15000~24000RPM.

[0053] As one embodiment of the present invention, in step S1, the pulse period of the bottom pulse is 5 to 30 seconds and the duty cycle is 30% to 70%.

[0054] This invention employs a bottom pulse method to allow gas to enter the reaction zone, forming a basic upward airflow; at the same time, a swirling guide structure is set at the top of the reaction zone to make the airflow spiral upward, thereby significantly improving the coupling uniformity of the oxygen concentration field and temperature field in the reaction zone.

[0055] In one embodiment of the present invention, in step S1, the preheating temperature is 300~500℃.

[0056] In one embodiment of the present invention, in step S1, the flow rate of the air or oxygen is 100-1000 L / min.

[0057] In one embodiment of the present invention, in step S1, the calcination temperature is 930~960℃ and the time is 40~80h.

[0058] In one embodiment of the present invention, in step S2, the particle size of the crushed powder is 5~25μm.

[0059] In one embodiment of the present invention, in step S2, the hot-pressing temperature of the pressure target is 820~920℃, the hot-pressing holding time is 0.5-2h, the hot-pressing pressure is 5~20MPa, and the hot-pressing atmosphere is vacuum or inert gas, wherein the vacuum degree is less than 10Pa, and the inert gas includes nitrogen and argon. A slight positive pressure is maintained in the cavity during ventilation.

[0060] This invention can also employ a "preheated air / oxygen - high flow rate - bottom pulse ventilation - spiral upward airflow" scheme. First, bottom pulse ventilation creates intermittent, strong airflow impacts, combined with continuous high-flow-rate purging, effectively entraining the CO2 waste gas generated in the reaction. The spiral upward flow channel design within the furnace extends the gas path, enhances overall convection, and prevents localized accumulation and stagnation of waste gas, achieving rapid and thorough discharge. Second, using preheated air / oxygen as the gas source ensures the introduced gas itself has a stable temperature, preventing localized temperature drops caused by the introduction of cold air. The high-flow-rate spiral upward airflow forms orderly circulating convection within the furnace, breaking up localized thermal stagnation zones and ensuring sufficient heat exchange throughout the furnace, effectively optimizing the overall temperature field uniformity. Finally, timely CO2 discharge eliminates the inhibitory effect of the reverse reaction, stabilizing the forward reaction. A uniform temperature field and sufficient contact between materials and the reaction atmosphere ensure consistent reaction conditions for all materials, ultimately improving the overall reaction rate and reaction uniformity.

[0061] The present invention's "preheated air / oxygen - high flow rate - bottom pulse ventilation - spiral upward airflow" scheme has strong exhaust capacity and completely avoids the impact of CO2 accumulation on the reaction; the preheated gas source combined with the spiral airflow has a uniform temperature field distribution, actively guides the gas to form a vortex and discharges it in time, resulting in good material reaction consistency; the airflow organization is reasonable, the gas-solid contact is sufficient, and the reaction efficiency is high.

[0062] Fourthly, the present invention provides a high-purity superconducting target material prepared by the method described above.

[0063] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention is the first to discover that during the calcination process of large-scale preparation of superconducting targets, problems such as the inability to expel CO2 waste gas and poor temperature field uniformity exist, leading to a decline in the superconducting performance of the target material. This technical defect of poor performance in large-scale preparation of superconducting targets has been difficult to overcome. Based on this, this invention proposes a "preheated air / oxygen - high flow rate - side-diffuse introduction" scheme, constructing a forced convection field covering the entire reaction chamber. This continuously and rapidly strips CO2 generated by reactions such as BaCO3 decomposition from the surface of the powder particles and carries it away from the reaction zone, avoiding reaction inhibition and BaCO3 impurity phase residue caused by localized CO2 accumulation. Simultaneously, preheating the air / oxygen before introduction significantly reduces the temperature difference between the inlet gas and the high-temperature zone of the furnace. Combined with the spherical particles after spray granulation, this provides numerous gas channels, and each sphere serves as an independent target reaction center, greatly improving reaction efficiency and uniformity, thereby significantly enhancing the superconducting performance of the target material.

[0064] 2. This solution has simple steps and is easy to scale up for production.

[0065] 3. The present invention can also select the "preheated air / oxygen - high flow rate - porous ceramic carrier for bottom ventilation" scheme, using porous ceramic as the carrier for the powder to be sintered, and at the same time, using spherical powder prepared by spray granulation as the basis, to construct a high-quality sintering environment with uniform gas distribution and stable temperature to promote reaction. It can timely encapsulate the CO2 generated by the material reaction and quickly discharge it upward, effectively eliminating the inhibitory effect of CO2 on the forward sintering reaction, ensuring the continuous and stable forward progress of the reaction, thereby greatly improving the overall reaction rate and overall reaction uniformity of powder sintering, and significantly improving the superconducting performance of the target material.

[0066] 4. This solution can make the heating and atmosphere conditions of materials in each area more consistent, and the gas-solid contact more sufficient and uniform, which can significantly improve the sintering reaction rate and reaction uniformity, effectively improve the batch sintering consistency, and improve the overall sintering quality and stability of the product.

[0067] 5. Alternatively, the present invention can select the "preheated air / oxygen - high flow rate - bottom pulse ventilation - spiral upward airflow" scheme. The bottom pulse ventilation forms an intermittent strong airflow impact, which, combined with the continuous purging of the high flow rate airflow, can promptly entrain the CO2 waste gas generated by the reaction. The timely discharge of CO2 eliminates the inhibitory effect of the reverse reaction and stabilizes the forward reaction. At the same time, the spiral upward flow channel design of the airflow along the furnace extends the gas path, enhances the overall convection, avoids the local accumulation and retention of waste gas, and achieves rapid and thorough discharge of waste gas.

[0068] 6. This solution has strong exhaust capacity, completely avoiding the impact of CO2 accumulation on the reaction; the preheated gas source combined with the spiral airflow ensures uniform temperature distribution, actively guides the gas to form a swirling flow and discharges it in a timely manner, resulting in good material reaction consistency; the airflow organization is reasonable, the gas-solid contact is sufficient, and the reaction efficiency is high. Attached Figure Description

[0069] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of air being introduced via side diffusion in Example 1; Figure 2 This is a schematic diagram of air being introduced from bottom to top in Comparative Example 3; Figure 3 Here is a SEM image of the powder in Example 1; Figure 4 The image shows the XRD pattern of the powder in Example 1. Figure 5 Here is a SEM image of the powder in Example 2; Figure 6 The image shows the XRD pattern of the powder in Example 2. Figure 7 This is a schematic diagram of air being introduced from bottom to top in Example 6; Figure 8 Here is a SEM image of the powder in Example 6; Figure 9 The image shows the XRD pattern of the powder in Example 6. Figure 10 This is a schematic diagram of air being introduced via a bottom pulse method in Example 7; Figure 11 Here is a SEM image of the powder in Example 7; Figure 12 The image shows the XRD pattern of the powder in Example 7. Figure 13 Here is a SEM image of the powder in Comparative Example 1; Figure 14 The XRD pattern of the powder in Comparative Example 1; Figure 15 Here is a SEM image of the powder in Comparative Example 2; Figure 16 The XRD pattern of the powder in Comparative Example 2; Figure 17 To show the C content at different sampling locations of the powder in Comparative Example 3; Figure 18 The image shows the XRD pattern of the powder in Comparative Example 3. Detailed Implementation

[0070] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, providing detailed implementation methods and specific operating procedures, which will help those skilled in the art to further understand the present invention. It should be noted that the scope of protection of the present invention is not limited to the following embodiments; any adjustments and improvements made under the concept of the present invention are all within the scope of protection of the present invention.

[0071] Example 1 This embodiment provides a method for mass production of high-purity superconducting targets, including the following steps: S1. Weigh out 50 kg of europium oxide, copper oxide and barium carbonate as raw materials, mix the raw materials and grind them in a sand mill for 1 hour to obtain a slurry; wherein the molar ratio of europium oxide, copper oxide and barium carbonate is 0.5:2:3; Among them, the sand milling is carried out by using a zirconia ball mill with a diameter of 0.2 mm, using ultrapure water as the dispersion medium, the solid content of the slurry is 55 wt.%, and using a peristaltic pump to add ammonium polyacrylate as a dispersant at a uniform rate, with a final addition amount of 1 wt.%, and the sand milling time is 1 h. S2. After spray granulation of the slurry, it is introduced through side dispersion (e.g.) Figure 1 As shown), preheated air at 300℃ (flow rate of 800 L / min) is introduced, and the mixture is calcined at 950℃ for 50 hours, then crushed to obtain 5-25μm powder, such as... Figure 3 As shown; from Figure 4 It can be seen that the powder XRD shows no impurities.

[0072] The inlet air temperature for spray granulation is 200℃, the outlet air temperature is 80℃, and the atomizer speed is 20000RPM. S3. Under an argon atmosphere, the powder is pressed into a target (hot pressing temperature is 880℃, hot pressing time is 1h, hot pressing pressure is 10MPa) to obtain a superconducting target material.

[0073] Example 2 This embodiment provides a method for mass production of high-purity superconducting targets, including the following steps: S1. Weigh out 100 kg of europium oxide, copper oxide and barium carbonate as raw materials, mix the raw materials and grind them in a sand mill for 1 hour to obtain a slurry; wherein the molar ratio of europium oxide, copper oxide and barium carbonate is 0.5:2:3; Among them, the sand milling is carried out by using a zirconia ball mill with a diameter of 0.2 mm, using ultrapure water as the dispersion medium, the solid content of the slurry is 55 wt.%, and using a peristaltic pump to add ammonium polyacrylate as a dispersant at a uniform rate, with a final addition amount of 1 wt.%, and the sand milling time is 1 h. S2. After spray granulation of the slurry, preheated air at 500℃ (flow rate of 800 L / min) is introduced through side diffusion, and the mixture is calcined at 950℃ for 60 hours, then crushed to obtain 5-25μm powder; Figure 5 As shown, the powder has fine grains and exhibits a normal distribution; from Figure 6 It can be seen that the powder XRD shows no impurities.

[0074] The inlet air temperature for spray granulation is 200℃, the outlet air temperature is 80℃, and the atomizer speed is 20000RPM. S3. Under an argon atmosphere, the powder is pressed into a target (hot pressing temperature is 880℃, hot pressing time is 1h, hot pressing pressure is 10MPa) to obtain a superconducting target material.

[0075] Example 3 The preparation method of this embodiment is basically the same as that of Example 1, except that europium oxide in step S1 is replaced with gadolinium oxide; the calcination temperature in step S2 is replaced with 945°C, and the hot pressing temperature in step 3 is replaced with 875°C.

[0076] Example 4 The preparation method of this embodiment is basically the same as that of Example 1, except that europium oxide in step S1 is replaced with samarium oxide; the calcination temperature in step S2 is replaced with 955°C; and the hot pressing temperature in step 3 is replaced with 880°C.

[0077] Example 5 The preparation method of this embodiment is basically the same as that of Example 1, except that europium oxide in step S1 is replaced with yttrium oxide; the calcination temperature in step S2 is replaced with 935°C; and the hot pressing temperature in step 3 is replaced with 860°C.

[0078] Example 6 This embodiment provides a method for mass production of high-purity superconducting targets, including the following steps: S1. Weigh out 50 kg of europium oxide, copper oxide and barium carbonate as raw materials, mix the raw materials and grind them in a sand mill for 1 hour to obtain a slurry; wherein the molar ratio of europium oxide, copper oxide and barium carbonate is 0.5:2:3; Among them, the sand milling is carried out by using a zirconia ball mill with a diameter of 0.2 mm, using ultrapure water as the dispersion medium, the solid content of the slurry is 55 wt.%, and using a peristaltic pump to add ammonium polyacrylate as a dispersant at a uniform rate, with a final addition amount of 1 wt.%, and the sand milling time is 1 h. S2. After spray granulation of the slurry, place it in a porous alumina foam ceramic carrier, using a bottom-to-top method (e.g., ...). Figure 7As shown), preheated air at 300℃ (flow rate of 800 L / min) is introduced, and the mixture is calcined at 950℃ for 50 hours, then crushed to obtain 5-25μm powder, such as... Figure 8 As shown, the powder has fine grains and exhibits a normal distribution; from Figure 9 It can be seen that the powder XRD shows no impurities.

[0079] The inlet air temperature for spray granulation is 200℃, the outlet air temperature is 80℃, and the atomizer speed is 20000RPM. S3. Under an argon atmosphere, the powder is pressed into a target (hot pressing temperature is 880℃, hot pressing time is 1h, hot pressing pressure is 10MPa) to obtain a superconducting target material.

[0080] Example 7 This embodiment provides a method for mass production of high-purity superconducting targets, including the following steps: S1. Weigh out 50 kg of europium oxide, copper oxide and barium carbonate as raw materials, mix the raw materials and grind them in a sand mill for 1 hour to obtain a slurry; wherein the molar ratio of europium oxide, copper oxide and barium carbonate is 0.5:2:3; Among them, the sand milling is carried out by using a zirconia ball mill with a diameter of 0.2 mm, using ultrapure water as the dispersion medium, the solid content of the slurry is 55 wt.%, and using a peristaltic pump to add ammonium polyacrylate as a dispersant at a uniform rate, with a final addition amount of 1 wt.%, and the sand milling time is 1 h. S2. After spray granulation of the slurry, preheated air (flow rate of 800 L / min) at 300℃ is introduced in a bottom pulse manner (pulse period of 15 s, duty cycle of 50%), and a swirl guide structure is set at the upper part of the reaction zone to make the airflow rise in a spiral (e.g., Figure 10 As shown), the sample was calcined at 950℃ for 50 hours and then crushed to obtain 5-25μm powder, as shown. Figure 11 As shown, the powder has fine grains and exhibits a normal distribution; from Figure 12 It can be seen that the powder XRD shows no impurities.

[0081] The inlet air temperature for spray granulation is 200℃, the outlet air temperature is 80℃, and the atomizer speed is 20000RPM. S3. Under an argon atmosphere, the powder is pressed into a target (hot pressing temperature is 880℃, hot pressing time is 1h, hot pressing pressure is 10MPa) to obtain a superconducting target material.

[0082] Comparative Example 1 The preparation method of this comparative example is basically the same as that of Example 1, except that in step S2, unheated air is introduced. Figure 13It can be seen that in Comparative Example 1, the lack of preheated air resulted in a large temperature difference within the cavity, leading to uneven reaction. The high-temperature zone exhibited large grain growth, while the low-temperature zone had small, unevenly distributed grains. For example... Figure 14 It can be seen that the powder XRD contains BaCO3 residue.

[0083] Comparative Example 2 The preparation method of this comparative example is basically the same as that of Example 1, except that the air flow rate in step S2 is 40 L / min. Figure 15 It can be seen that the ventilation flow rate of Comparative Example 2 was too small, failing to remove the CO2 waste gas generated by the reaction in time, resulting in the reaction not proceeding in the forward direction and significant differences in powder particle size. For example... Figure 16 It can be seen that the powder XRD contains BaCO3 residue.

[0084] Comparative Example 3 The preparation method of this comparative example is basically the same as that of Example 1, except that in step S2, the side-diffuse air introduction method is replaced with the traditional bottom-up air introduction method (e.g., Figure 2 As shown). Figure 17-18 It can be seen that the ventilation method of Comparative Example 3 is from top to bottom, which leads to the complete reaction in the upper layer and less reaction in the lower layer during powder synthesis. From the surface to the inside, the XRD becomes worse and worse, BaCO3 appears, and the C content increases.

[0085] Performance testing The performance of the target material was evaluated by preparing superconducting tapes using actual PLD deposition. The critical current Jc and critical transition temperature of the superconducting tape with a thickness of 1 μm were compared under the same conditions, and the results are shown in Table 1. It is important to emphasize that for REBCO, the critical transition temperature Tc increases almost linearly with the increase of the ionic radius r. Furthermore, the critical current density Jc at 77 K is affected by Tc, increasing with the increase of the RE ionic radius. That is, the Jc and Tc of YBCO are relatively lower than those of SmBCO, EuBCO, and GdBCO.

[0086] Table 1

[0087] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for mass production of high-purity superconducting targets, characterized in that, The method employs a side-diffuse infiltration process, specifically including the following steps: S1. After spray granulation of a slurry containing a large amount of rare earth oxides, copper source and barium source, preheated air or oxygen is introduced by side dispersion and calcined to obtain powder. S2. Crush the powder and press it onto the target to obtain the final product.

2. The method according to claim 1, characterized in that, In step S1, the preparation method of the slurry containing a large quantity of rare earth oxides, copper source, and barium source is as follows: a large quantity of rare earth oxides, copper source, and barium source are weighed as raw materials and milled to obtain a slurry; the large quantity is 50 kg or more; the rare earth oxides include one of europium oxide, gadolinium oxide, samarium oxide, and yttrium oxide; the copper source includes one of copper oxide and copper nitrate; the barium source includes one of barium carbonate, barium oxide, and barium hydroxide; the molar ratio of rare earth oxides, copper source, and barium source is (0.5±0.05):(2±0.2):(3±0.3); the diameter of the ball mill used for milling is 0.2~0.5 mm, and the material includes zirconium oxide; the milling time is 0.5~3 h.

3. The method according to claim 1, characterized in that, In step S1, during the spray granulation process, the inlet air temperature is 200~250℃, the outlet air temperature is 90~120℃, and the atomizer rotation speed is 15000~24000RPM.

4. The method according to claim 1, characterized in that, In step S1, the preheating temperature is 300~500℃; the air or oxygen flow rate is 100-1000 L / min; and the calcination temperature is 930~960℃ for 40~80h.

5. The method according to claim 1, characterized in that, In step S2, the particle size of the crushed powder is 5~25μm; in the pressure target, the hot pressing temperature is 820~920℃, the hot pressing holding time is 0.5-4h, the hot pressing pressure is 5~20MPa, and the hot pressing atmosphere is vacuum or inert gas, wherein the vacuum degree is less than 10Pa, and the inert gas includes nitrogen and argon.

6. A method for mass production of high-purity superconducting targets, characterized in that, The method employs a bottom-ventilation process using a porous ceramic carrier, specifically including the following steps: S1. After spray granulation of a slurry containing a large amount of rare earth oxides, copper source and barium source, the slurry is placed in a porous ceramic carrier and preheated air or oxygen is introduced from bottom to top for calcination to obtain powder. S2. Crush the powder and press it onto the target to obtain the final product.

7. The method according to claim 6, characterized in that, In step S1, the porous ceramic includes open-cell alumina foam ceramic.

8. A method for mass production of high-purity superconducting targets, characterized in that, The method employs a bottom pulse ventilation-airflow spiral ascent process, specifically including the following steps: S1. After spray granulation of a slurry containing a large amount of rare earth oxides, copper source and barium source, preheated air or oxygen is introduced in a bottom pulse manner and the airflow is kept spiraling upward for calcination to obtain powder. S2. Crush the powder and press it onto the target to obtain the final product.

9. The method according to claim 8, characterized in that, In step S1, the bottom pulse mode has a pulse period of 5 to 30 seconds and a duty cycle of 30% to 70%.

10. A high-purity superconducting target material obtained by the preparation method according to any one of claims 1-9.

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