A 122-type iron-based superconductor precursor powder, a preparation method and application thereof, and a preparation method of a 122-type iron-based superconductor

Abstract

This invention belongs to the field of superconducting materials technology, specifically relating to a type 122 iron-based superconductor precursor powder, its preparation method and application, and a method for preparing type 122 iron-based superconductors. This invention uses two or more superconducting powders with the same crystal structure but different lattice constants in the type 122 iron-based superconductor precursor powder. Without introducing non-superconducting phases, an elemental concentration difference is formed at the grain boundaries, resulting in element diffusion at the grain boundaries during subsequent annealing. Ultimately, a good fusion state is formed at the grain boundaries, significantly improving the connectivity between grains. Simultaneously, due to the difference in lattice constants between the two or more superconductors, lattice defects are generated in the final superconductor, thereby increasing the flux pinning force of the type 122 iron-based superconductor and reducing the dependence of the transmission current on the magnetic field.

Description

Technical Field

[0001] This invention belongs to the field of superconducting materials technology, specifically relating to a type 122 iron-based superconductor precursor powder, its preparation method and application, and the preparation method of type 122 iron-based superconductor. Background Technology

[0002] In 2008, the Tokyo Institute of Technology in Japan published a paper titled "[Iron-based layered superconductor LaO]". 1-x F x FeAs (x=0.05-0.12) with T c =26 K J. Am. Chem. Sco. LaO was found in 130 (2008) 3296-3297) 1-x F x The superconductivity of FeAs materials up to 26 K sparked a surge of research into novel iron-based superconductors. Currently, the highest superconducting transition temperature for iron-based superconductors has reached 55 K, and they possess advantages such as high upper critical field, large critical current, and low anisotropy, making them a promising new high-temperature superconducting material with significant application potential in the 20–30 K temperature range. While exploring their superconducting mechanisms, scientists also place great emphasis on their practical applications. Compared to copper oxide high-temperature superconductors, iron-based superconductors have lower material and fabrication costs, attracting widespread attention from the international superconducting community.

[0003] Currently, the existing technology "High transport current superconductivity in powder-in-tube Ba" 0.6 K 0.4 The paper "Fe2As2tapes at 27 T" (Supercond. Sci. Technol. 31 (2018) 015017) discloses that the critical current density of type 122 iron-based superconducting wire reaches 150,000 A / cm² under a 10T magnetic field. 2 This demonstrates promising application prospects. However, to meet the practical application requirements of iron-based superconducting materials in strong magnetic fields, it is necessary to continuously improve their flux pinning force and critical current density. The flux pinning force of iron-based superconducting materials mainly originates from crystal defects in the material, while their critical current density is primarily affected by grain connectivity. In previous studies, to improve the superconducting properties of iron-based superconducting materials, researchers typically used various methods to prepare high-purity, single-component superconducting precursor powders. However, experiments have shown that iron-based superconductors prepared using the same type of precursor powder exhibit poor grain connectivity, resulting in lower critical current densities. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a type 122 iron-based superconductor precursor powder, its preparation method and application, and a method for preparing a type 122 iron-based superconductor. The type 122 iron-based superconductor precursor powder provided by the present invention can improve the magnetic flux pinning force and critical current density of the type 122 iron-based superconductor and reduce the magnetic field dependence.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a type 122 iron-based superconductor precursor powder, comprising at least two of precursor powder 1, precursor powder 2, and precursor powder 3; The chemical composition of the precursor powder 1 is A 1-x G x Fe2As2, where A is Ba or Sr, G is Cs or K, and x = 0.1~0.6; The chemical composition of the precursor powder 2 is J 1-y D y Fe2As2, J is Ca or Eu, D is Na, Ce or Pr, y = 0.1~0.6; The chemical composition of the precursor powder 3 is E(Fe) 1-z M z )2As2, E is Ba or Sr, M is Co or Ni, z=0.1~0.6.

[0006] Preferably, the type 122 iron-based superconductor precursor powder includes two types: precursor powder 1 and precursor powder 2, and the molar ratio of precursor powder 1 to precursor powder 2 is (0.1~1):(0.1~1); Alternatively, the type 122 iron-based superconductor precursor powder may include two types: precursor powder 1 and precursor powder 3, wherein the molar ratio of precursor powder 1 to precursor powder 3 is (0.1~1):(0.1~1); Alternatively, the 122-type iron-based superconductor precursor powder may include two types: precursor powder 2 and precursor powder 3, with a molar ratio of (0.1~1):(0.1~1).

[0007] Preferably, the 122-type iron-based superconductor precursor powder includes three types: precursor powder 1, precursor powder 2, and precursor powder 3, and the molar ratio of precursor powder 1, precursor powder 2, and precursor powder 3 is (0.1~0.3):(0.1~0.3):(0.4~0.8).

[0008] This invention also provides a method for preparing the 122-type iron-based superconductor precursor powder described in the above technical solution, comprising the following steps: Under a protective gas atmosphere, the raw materials corresponding to the elements are mixed according to the chemical composition of the precursor powder 1, and the first sintering is carried out to obtain the precursor powder 1. Under a protective gas atmosphere, the raw materials corresponding to the elements are mixed according to the chemical composition of the precursor powder 2, and a second sintering is carried out to obtain the precursor powder 2. Under a protective gas atmosphere, the raw materials corresponding to the elements are mixed according to the chemical composition of the precursor powder 3, and a third sintering is carried out to obtain the precursor powder 3. At least two of the precursor powder 1, precursor powder 2 and precursor powder 3 are mixed to obtain the 122 type iron-based superconductor precursor powder.

[0009] Preferably, the temperature of the first sintering is 600~1000℃, and the holding time is 1~50h.

[0010] Preferably, the second sintering temperature is 600~1000℃ and the holding time is 1~50h.

[0011] Preferably, the temperature of the third sintering is 600~1000℃, and the holding time is 1~50h.

[0012] The present invention also provides the application of the type 122 iron-based superconductor precursor powder described in the above technical solution or the type 122 iron-based superconductor precursor powder prepared by the preparation method described in the above technical solution in the preparation of type 122 iron-based superconductors.

[0013] This invention also provides a method for preparing a type 122 iron-based superconductor, comprising the following steps: After the 122-type iron-based superconductor precursor powder is processed into a material, it is annealed under inert gas protection or in a vacuum environment to obtain the 122-type iron-based superconductor. The type 122 iron-based superconductor precursor powder is the type 122 iron-based superconductor precursor powder described in the above technical solution or the type 122 iron-based superconductor precursor powder prepared by the preparation method described in the above technical solution.

[0014] Preferably, the annealing temperature is 300~1100℃ and the holding time is 0.5~50h.

[0015] This invention provides a type 122 iron-based superconductor precursor powder, comprising at least two of precursor powder 1, precursor powder 2, and precursor powder 3; the chemical composition of precursor powder 1 is A. 1-x G x Fe2As2, A is Ba or Sr, G is Cs or K, x = 0.1~0.6; the chemical composition of the precursor powder 2 is J 1-y D y Fe2As2, J is Ca or Eu, D is Na, Ce, or Pr, y = 0.1~0.6; the chemical composition of the precursor powder 3 is E(Fe 1-z M z)2As2, E is Ba or Sr, M is Co or Ni, z=0.1~0.6.

[0016] This invention utilizes two or more superconducting powders with the same crystal structure but different lattice constants in the precursor powder of a type 122 iron-based superconductor. Without introducing a non-superconducting phase, an elemental concentration difference is created at the grain boundaries, leading to element diffusion at these boundaries during subsequent annealing. This ultimately results in a well-fused state at the grain boundaries, significantly improving the connectivity between grains. Simultaneously, due to the difference in lattice constants between the two or more superconductors, lattice defects such as bulk defects introduced by the second phase and planar defects caused by stacking faults are generated in the final superconductor. These increased lattice defects can act as flux pinning centers, effectively increasing the flux pinning force of the type 122 iron-based superconductor. This, in turn, increases the critical current density of the iron-based superconductor under a magnetic field, mitigating the inhibitory effect of increased magnetic fields on the transmission performance of the iron-based superconductor and reducing the dependence of the transmission current on the magnetic field. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of element diffusion in two crystals with the same crystal structure but different lattice parameters. Figure 2 This is a scanning electron microscope image of the 122-type iron-based superconductor prepared in Example 1 of the present invention. Detailed Implementation

[0018] This invention provides a type 122 iron-based superconductor precursor powder, comprising at least two of precursor powder 1, precursor powder 2, and precursor powder 3; The chemical composition of the precursor powder 1 is A 1-x G x Fe2As2, where A is Ba or Sr, G is Cs or K, and x = 0.1~0.6; The chemical composition of the precursor powder 2 is J 1-y D y Fe2As2, J is Ca or Eu, D is Na, Ce or Pr, y = 0.1~0.6; The chemical composition of the precursor powder 3 is E(Fe) 1-z M z )2As2, E is Ba or Sr, M is Co or Ni, z=0.1~0.6.

[0019] Unless otherwise specified, the present invention does not have special requirements on the source of raw materials used, and commercially available products well known to those skilled in the art can be used.

[0020] The 122-type iron-based superconductor precursor powder provided by the present invention includes at least two of precursor powder 1, precursor powder 2 and precursor powder 3, preferably precursor powder 1 and precursor powder 2, precursor powder 1 and precursor powder 3, or precursor powder 2 and precursor powder 3.

[0021] In this invention, the chemical composition of the precursor powder 1 is A. 1-x G x Fe2As2, where A is Ba or Sr, preferably Ba, G is Cs or K, preferably K, and x = 0.1~0.6, preferably 0.2~0.5. In this embodiment of the invention, the chemical composition of the precursor powder 1 is preferably Ba. 0.5 K 0.5 Fe2As2 or Ba 0.6 K 0.4 Fe2As2.

[0022] In this invention, the chemical composition of the precursor powder 2 is J 1-y D y Fe2As2, where J is Ca or Eu, preferably Ca, D is Na, Ce, or Pr, preferably Ce, and y = 0.1~0.6, preferably 0.2~0.5. In this embodiment of the invention, the chemical composition of the precursor powder 2 is preferably Eu. 0.6 Na 0.4 Fe2As2 or Ca 0.5 Ce 0.5 Fe2As2.

[0023] In this invention, the chemical composition of the precursor powder 3 is E(Fe) 1-z M z )2As2, E is Ba or Sr, preferably Sr, M is Co or Ni, preferably Ni, z=0.1~0.6, more preferably 0.2~0.5.

[0024] In this embodiment of the invention, the chemical composition of the precursor powder 3 is preferably Ba(Fe) 0.5 Co 0.5 )2As2 or Sr(Fe 0.5 Ni 0.5 )2As2.

[0025] In this invention, the type 122 iron-based superconductor precursor powder includes two types: precursor powder 1 and precursor powder 2. The molar ratio of precursor powder 1 to precursor powder 2 is preferably (0.1~1):(0.1~1), more preferably 1:1; or the type 122 iron-based superconductor precursor powder includes two types: precursor powder 1 and precursor powder 3. The molar ratio of precursor powder 1 to precursor powder 3 is preferably (0.1~1):(0.1~1), more preferably 1:0.7; or the type 122 iron-based superconductor precursor powder includes two types: precursor powder 2 and precursor powder 3. The molar ratio of precursor powder 2 to precursor powder 3 is preferably (0.1~1):(0.1~1), more preferably 1:0.5.

[0026] In this invention, the 122-type iron-based superconductor precursor powder includes three types: precursor powder 1, precursor powder 2, and precursor powder 3. The molar ratio of precursor powder 1, precursor powder 2, and precursor powder 3 is preferably (0.1~0.3):(0.1~0.3):(0.4~0.8), and more preferably 0.2:0.2:0.6.

[0027] All three precursor powders belong to the ThCr2Si2 type tetragonal crystal system with space group 14 / mmm. They are composed of alternating layers of intercalating element A ions and FeAs layers along the C-axis, collectively referred to as the FeAs122 phase. However, due to the different atomic radii of the intercalating element A between the FeAs layers, the lattice constants of the three precursor powders differ to some extent.

[0028] This invention utilizes two or more superconducting powders with the same crystal structure but different lattice constants in the 122-type iron-based superconductor precursor powder. Without introducing non-superconducting phases, an elemental concentration difference is created at the grain boundaries, leading to element diffusion at these boundaries during subsequent annealing. This ultimately results in a well-fused state at the grain boundaries, significantly improving the connectivity between grains. Simultaneously, the difference in lattice constants between the two or more superconductors creates lattice defects in the final superconductor, thereby increasing the flux pinning force of the 122-type iron-based superconducting material and reducing the dependence of the transmission current on the magnetic field.

[0029] This invention also provides a method for preparing the 122-type iron-based superconductor precursor powder described in the above technical solution, comprising the following steps: Under a protective gas atmosphere, the raw materials corresponding to the elements are mixed according to the chemical composition of the precursor powder 1, and the first sintering is carried out to obtain the precursor powder 1. Under a protective gas atmosphere, the raw materials corresponding to the elements are mixed according to the chemical composition of the precursor powder 2, and a second sintering is carried out to obtain the precursor powder 2. Under a protective gas atmosphere, the raw materials corresponding to the elements are mixed according to the chemical composition of the precursor powder 3, and a third sintering is carried out to obtain the precursor powder 3. At least two of the precursor powder 1, precursor powder 2 and precursor powder 3 are mixed to obtain the 122 type iron-based superconductor precursor powder.

[0030] In this invention, the protective gas is preferably argon; the concentration of the argon is preferably 99.9~99.999%, more preferably 99.999%; the preparation of the 122-type iron-based superconductor precursor powder is preferably completed in a glove box.

[0031] In this invention, the raw materials corresponding to Ba element in the chemical composition of precursor powder 1, precursor powder 2 and precursor powder 3 are preferably Ba shavings, Sr element is preferably Sr shavings, Cs element is preferably Cs powder, K element is preferably K block, Ca element is preferably Ca shavings, Eu element is preferably Eu shavings, Na element is preferably Na block, Ce element is preferably Ce block or Pr element is preferably Pr block, Co element is preferably Co powder, Ni element is preferably Ni block, Fe element is preferably Fe powder and As element is preferably As powder.

[0032] In this embodiment of the invention, the raw materials corresponding to the elements in the chemical composition of the 122-type iron-based superconductor precursor powder are specifically Ba shavings, K blocks, Fe powder, As powder, Eu shavings and Na blocks, or Ca shavings, Ce blocks, Fe powder, As powder, Ba shavings and Co powder, or Ba shavings, K blocks, Fe powder, As powder, Sr shavings and Ni blocks.

[0033] In this invention, the temperature of the first sintering is preferably 600~1000℃, more preferably 700~900℃, and the holding time is preferably 1~50h, more preferably 10~35h.

[0034] In this invention, the second sintering temperature is preferably 600~1000℃, more preferably 700~900℃, and the holding time is preferably 1~50h, more preferably 10~35h.

[0035] In this invention, the temperature of the third sintering is preferably 600~1000℃, more preferably 700~900℃, and the holding time is preferably 1~50h, more preferably 10~35h.

[0036] The present invention also provides the application of the type 122 iron-based superconductor precursor powder described in the above technical solution or the type 122 iron-based superconductor precursor powder prepared by the preparation method described in the above technical solution in the preparation of type 122 iron-based superconductors.

[0037] This invention also provides a method for preparing a type 122 iron-based superconductor, comprising the following steps: After the 122-type iron-based superconductor precursor powder is processed into a material, it is annealed under inert gas protection or in a vacuum environment to obtain the 122-type iron-based superconductor. The type 122 iron-based superconductor precursor powder is the type 122 iron-based superconductor precursor powder described in the above technical solution or the type 122 iron-based superconductor precursor powder prepared by the preparation method described in the above technical solution.

[0038] The present invention processes the 122-type iron-based superconductor precursor powder to obtain a profile; In this invention, the profile preferably includes a block, a wire, or a strip, and more preferably a block.

[0039] When the profile is in the form of a block, the preferred processing method is to place the 122-type iron-based superconductor precursor powder in a mold and press it into a block. In this invention, the mold is preferably a cylindrical pressing mold; the pressing equipment is preferably a pressing machine; the pressing pressure is preferably 1~30MPa, more preferably 10~15MPa.

[0040] When the profile is a wire, the preferred processing method is to fill the sleeve with the 122-type iron-based superconductor precursor powder, seal both ends of the sleeve, and then perform rotary forging and drawing on the resulting tube-mounted composite in sequence. The sleeve is preferably a metal tube, a composite metal tube, or an alloy tube, more preferably a metal tube. The metal tube is preferably a silver tube or an Nb tube. The length of the silver tube is preferably 10-12 cm, more preferably 12 cm, the inner diameter is preferably 5-6 mm, more preferably 5 mm, and the outer diameter is preferably 8 mm. The sealing is preferably done with an Nb plug. The rotary forging is preferably done with a rotary forging machine. The diameter of the wire obtained by rotary forging is preferably 2-5 mm, more preferably 3.4 mm. The diameter of the wire obtained by drawing is preferably 1-2 mm, more preferably 1.65 mm. The pass rate of drawing is preferably 4-10%, more preferably 5-8%. The number of drawing passes is preferably 30-42, more preferably 32-36.

[0041] When the profile is strip, the preferred processing method is to fill the sleeve with the 122-type iron-based superconductor precursor powder, seal both ends of the sleeve, and then perform rotary forging, drawing, and rolling on the resulting tube-mounted composite in sequence. The rotary forging and drawing are as described above and will not be repeated here. The rolling is preferably flat roll rolling. The thickness of the rolled strip is preferably 0.2~0.6mm, more preferably 0.3mm. The width of the rolled strip is preferably 3~5mm, more preferably 3.5~4.7mm. The rolling pass rate is preferably 5~20%, more preferably 10%. The rolling passes are preferably 3~10, more preferably 5.

[0042] After obtaining the profile, the present invention anneals the profile under inert gas protection or in a vacuum environment to obtain a type 122 iron-based superconductor.

[0043] In this invention, the vacuum level of the vacuum environment is preferably 10. -1 ~10 -5 Pa, more preferably 10 Pa -3 ~10 -5 Pa; the inert gas preferably includes argon; the concentration of the inert gas is preferably 99~99.999%, more preferably 99.999%.

[0044] In this invention, the annealing temperature is preferably 300~1100℃, more preferably 500~1100℃, the holding time is preferably 0.5~50h, more preferably 20~50h, and the heating rate to the annealing temperature is preferably 5~20℃ / min, more preferably 10℃ / min.

[0045] Figure 1 This diagram illustrates the diffusion of elements in two crystals with the same crystal structure but different lattice parameters. Figure 1 As shown, due to the difference in lattice constants between the two precursor powders, the β phase embedded in the α phase exists as a lattice defect within the α phase, forming stacking faults at the interface of the two superconducting phases. These stacking faults are crystal defects that can act as flux pinning centers, preventing the movement of magnetic field lines and thus improving the material's flux pinning ability, thereby enhancing its critical current characteristics under a magnetic field.

[0046] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0047] Example 1 In an argon atmosphere (argon concentration of 99.999%) glove box, Ba shavings, K blocks, Fe powder, and As powder were mixed according to the chemical formula Ba 0.5 K 0.5 Fe₂As₂ was uniformly mixed according to the atomic molar ratio shown, and sintered at 900℃ for 35 h to obtain precursor powder 1. Then, Eu shavings, Na blocks, Fe powder and As powder were mixed according to the chemical formula Eu 0.6 Na 0.4 Fe2As2 was uniformly mixed at the atomic molar ratio shown and sintered at 900℃ for 35 h to obtain precursor powder 2. Precursor powder 1 and 2 were uniformly mixed at a molar ratio of 1:1, and then placed into a cylindrical tableting mold and pressed into blocks using a tableting machine at a pressure of 15 MPa. The blocks were then placed in a quartz tube, and the sealed quartz tube was placed in an annealing furnace and evacuated to 100℃. -3After Pa, high-purity argon gas (concentration of 99.999%) is introduced, and the temperature is increased to 500℃ at 10℃ / min and held for 5h. Then, the temperature is increased to 900℃ at 10℃ / min and held for 35h. The furnace is then cooled to room temperature to obtain type 122 iron-based superconductor bulk material.

[0048] The superconducting properties of the 122-type iron-based superconductor bulk sample were measured using a comprehensive physical property measurement system, and its magnetization critical current density was found to be greater than 2 × 10⁻⁶. 5 A / cm 2 (4.2 K, 0 T), the flux pinning potential can reach 9000 K (0.5 T), demonstrating a strong flux pinning capability.

[0049] Example 2 Under an argon atmosphere (argon concentration of 99.999%), Ca shavings, Ce blocks, Fe powder, and As powder were mixed according to the chemical formula Ca... 0.5 Ce 0.5 Fe2As2 was uniformly mixed at the atomic molar ratio shown, and sintered at 850℃ for 20 h to obtain precursor powder 2; then Ba shavings, Co powder, Fe powder and As powder were mixed according to the chemical formula Ba(Fe2As2)2. 0.5 Co 0.5 The precursor powder 3 is prepared by uniformly mixing the atomic molar ratio of 2As2 and sintering at 850℃ for 20 hours. Precursor powders 2 and 3 are then uniformly mixed at a molar ratio of 1:0.5 and used to fill a 12cm long silver tube with an inner diameter of 5mm and an outer diameter of 8mm. Both ends of the silver tube are sealed with Nb plugs. The tube-filled composite is then forged to 3.4mm using a rotary forging machine, and then drawn to 1.65mm. The drawing pass rate is 8%, and the preferred number of drawing passes is 36. The resulting wire is then placed in a vacuum annealing furnace and evacuated to 10℃. -3 After Pa, high-purity argon gas (argon concentration of 99.999%) is introduced, and the temperature is increased to 900℃ at 10℃ / min and held for 20h. The furnace is then cooled to room temperature to obtain type 122 iron-based superconductor wire.

[0050] The critical current of the 122-type iron-based superconductor wire sample was measured using the standard four-lead method, and its critical current density was found to be greater than 5 × 10⁻⁶. 4 A / cm 2 (4.2 K, 10 T), the flux pinning potential can reach 7100 K (0.5 T), demonstrating strong flux pinning capability.

[0051] Example 3 Under an argon atmosphere (argon concentration of 99.999%), Ba shavings, K blocks, Fe powder, and As powder were mixed according to the chemical formula Ba 0.6 K 0.4Fe₂As₂ was uniformly mixed according to the atomic molar ratio shown, and sintered at 900℃ for 30 h to obtain precursor powder 1; then Sr chips, Ni blocks, Fe powder and As powder were mixed according to the chemical formula Sr(Fe) 0.5 Ni 0.5 The precursor powder 3 was prepared by uniformly mixing the atomic molar ratio shown in 2As2 and sintering at 900℃ for 30h. The precursor powders 1 and 3 were uniformly mixed at a molar ratio of 1:0.7 and filled into a silver tube with a length of 10cm, an inner diameter of 6mm, and an outer diameter of 8mm. The two ends of the silver tube were sealed with Nb plugs. The tube-filled composite was forged to 3.4mm using a rotary forging machine and then drawn to 1.65mm. The drawing pass rate was 6%, and the number of drawing passes was preferably 42. Then, the wire was rolled into a strip with a width of 4mm and a thickness of 0.3mm using a flat roll mill. The rolling pass rate was 10%, and the number of rolling passes was 5. The obtained strip was placed in an argon atmosphere (argon concentration of 99.999%) annealing furnace and heated to 1100℃ at 10℃ / min and held for 50h. It was then cooled to room temperature in the furnace to obtain type 122 iron-based superconductor strip.

[0052] The obtained iron-based superconducting tape was subjected to critical current measurement using the standard four-lead method, and its critical current density was found to be greater than 3 × 10⁻⁶. 4 A / cm 2 (4.2 K, 14 T), the flux pinning potential can reach 7000 K (0.5 T), demonstrating strong flux pinning capability.

[0053] Comparative Example 1 In an atmosphere with an argon concentration of 99.999%, Ba shavings, K blocks, Fe powder, and As powder were mixed according to the chemical formula Ba 0.6 K 0.4 Fe2As2 was uniformly mixed in the atomic molar ratio shown, and sintered at 900℃ for 30h to obtain precursor powder; The precursor powder was used to fill a 10cm long silver tube with an inner diameter of 6mm and an outer diameter of 8mm. Both ends of the silver tube were sealed with Nb plugs. The tube-filled composite was then forged to 3.4mm using a rotary forging machine, and then drawn to 1.65mm. The drawing pass rate was 6%, and the number of drawing passes was preferably 42. Then, the wire was rolled into a strip with a width of 4mm and a thickness of 0.3mm using a flat roll mill. The rolling pass rate was 10%, and the number of rolling passes was 5. The obtained strip was placed in an annealing furnace with an argon concentration of 99.999%, heated to 900℃ at 10℃ / min and held for 10h. It was then cooled to room temperature in the furnace to obtain type 122 iron-based superconductor strip.

[0054] The obtained iron-based superconducting tape was subjected to critical current measurement using the standard four-lead method, and its critical current density was found to be 10. 4 A / cm 2(4.2 K, 14 T), the flux pinning potential is 4000 K (0.5 T).

[0055] Microstructure characterization Electron microscopy was performed on the 122-type iron-based superconductor prepared in Example 1 of this invention, and the results are as follows: Figure 2 As shown.

[0056] Depend on Figure 2 It is known that when two precursor powders with the same crystal structure but different lattice constants are mixed, a large elemental concentration gradient is formed at the grain boundary due to the different intercalation elements between the FeAs layers. Therefore, solid solution diffusion occurs at the grain boundaries between the grains during the subsequent heat treatment process, and good fusion is formed at the grain boundaries, which significantly improves the effective area for superconducting current transmission. This is very beneficial for the transmission of superconducting current and can effectively improve the transmission performance of superconducting materials.

[0057] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A type 122 iron-based superconductor precursor powder, characterized in that, Includes at least two of the following: precursor powder 1, precursor powder 2, and precursor powder 3; The chemical composition of the precursor powder 1 is A 1-x G x Fe2As2, where A is Ba or Sr, G is Cs or K, and x = 0.1–0.6; The chemical composition of the precursor powder 2 is J 1-y D y Fe2As2, J is Ca or Eu, D is Na, Ce or Pr, y = 0.1 to 0.6; The chemical composition of the precursor powder 3 is E(Fe) 1-z M z )2As2, E is Ba or Sr, M is Co or Ni, z = 0.1~0.

6.

2. The type 122 iron-based superconductor precursor powder according to claim 1, characterized in that, The 122-type iron-based superconductor precursor powder includes two types: precursor powder 1 and precursor powder 2, and the molar ratio of precursor powder 1 to precursor powder 2 is (0.1~1):(0.1~1). Alternatively, the type 122 iron-based superconductor precursor powder may include two types: precursor powder 1 and precursor powder 3, wherein the molar ratio of precursor powder 1 to precursor powder 3 is (0.1~1):(0.1~1); Alternatively, the 122-type iron-based superconductor precursor powder may include two types: precursor powder 2 and precursor powder 3, with a molar ratio of (0.1-1):(0.1-1).

3. The 122-type iron-based superconductor precursor powder according to claim 1, characterized in that, The 122-type iron-based superconductor precursor powder includes three types: precursor powder 1, precursor powder 2, and precursor powder 3. The molar ratio of precursor powder 1, precursor powder 2, and precursor powder 3 is (0.1-0.3):(0.1-0.3):(0.4-0.8).

4. A method for preparing the 122-type iron-based superconductor precursor powder according to any one of claims 1 to 3, comprising the following steps: Under a protective gas atmosphere, the raw materials corresponding to the elements are mixed according to the chemical composition of the precursor powder 1, and the first sintering is carried out to obtain the precursor powder 1. Under a protective gas atmosphere, the raw materials corresponding to the elements are mixed according to the chemical composition of the precursor powder 2, and a second sintering is carried out to obtain the precursor powder 2. Under a protective gas atmosphere, the raw materials corresponding to the elements are mixed according to the chemical composition of the precursor powder 3, and a third sintering is carried out to obtain the precursor powder 3. At least two of the precursor powder 1, precursor powder 2 and precursor powder 3 are mixed to obtain the 122 type iron-based superconductor precursor powder.

5. The preparation method according to claim 4, characterized in that, The first sintering temperature is 600-1000℃, and the holding time is 1-50h.

6. The preparation method according to claim 4, characterized in that, The second sintering temperature is 600–1000℃, and the holding time is 1–50 h.

7. The preparation method according to claim 4, characterized in that, The third sintering temperature is 600–1000℃, and the holding time is 1–50 h.

8. The application of the type 122 iron-based superconductor precursor powder according to any one of claims 1 to 3 or the type 122 iron-based superconductor precursor powder prepared by the preparation method according to any one of claims 4 to 7 in the preparation of type 122 iron-based superconductors.

9. A method for preparing a type 122 iron-based superconductor, characterized in that, Includes the following steps: After the 122-type iron-based superconductor precursor powder is processed into a material, it is annealed under inert gas protection or in a vacuum environment to obtain the 122-type iron-based superconductor. The type 122 iron-based superconductor precursor powder is the type 122 iron-based superconductor precursor powder according to any one of claims 1 to 3 or the type 122 iron-based superconductor precursor powder prepared by the preparation method according to any one of claims 4 to 7.

10. The preparation method according to claim 9, characterized in that, The annealing temperature is 300–1100℃, and the holding time is 0.5–50 h.

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