Nanocrystalline iron-based superconducting material and preparation method thereof
By preparing nanocrystalline iron-based superconducting materials, the problem of low critical current density of iron-based superconducting materials was solved by using rapid cooling and single-roller spin quenching, thus improving the high current transmission capability.
Patent Information
- Application Number
- CN202510878910.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-27
- Publication Date
- 2025-08-15
AI Technical Summary
The low critical current density of existing iron-based superconducting materials limits their applications.
Nanocrystalline iron-based superconducting materials are prepared by rapid cooling and single-roller spin quenching, controlling the grain size to 20~200nm, suppressing phase separation, and improving superconducting performance.
Under the conditions of 4.2 K temperature and 50 kOe magnetic field, the critical current density of nanocrystalline iron-based superconducting materials reaches 1 × 10⁴ A/cm², which significantly improves the current transport capability of superconducting materials.
Smart Images
Figure CN120496948A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of superconducting materials, and in particular to a nanocrystalline iron-based superconducting material and a preparation method thereof. Background Art
[0002] Superconducting materials have unimpeded current carrying capacity and complete anti-magnetism, which makes them widely used in medicine, electronics, electricity, high energy physics, national defense and military, transportation and other fields. With the rapid development of modern science and technology, higher requirements are also put forward for the performance of superconducting materials. High superconducting transition temperature, high upper critical field, high critical current density J c , low anisotropy become the prerequisites for the application of superconducting materials. Since its discovery in 2008, iron-based superconducting materials have been widely used due to their high superconducting transition temperature T c , up to 100 T upper critical field, low anisotropy (γ = 1-2) and thermal fluctuations, showing extremely high application value.
[0003] Critical current density is a key metric in the practical application of iron-based superconducting materials. Currently, under the same conditions, the critical current density of iron-based superconductors is typically an order of magnitude lower than that of copper oxides, which limits their application. Therefore, there is a need for iron-based superconducting materials with higher critical current density. Summary of the Invention
[0004] In order to solve the above problems, the present invention provides a nanocrystalline iron-based superconducting material with an average grain size of 20-200 nm and a critical current density exceeding 1× 10 4 A / cm 2 .
[0005] The present invention also provides a method for preparing the nanocrystalline iron-based superconducting material.
[0006] The present invention adopts the following technical solutions to achieve the above purpose:
[0007] A nanocrystalline iron-based superconducting material, wherein the average grain size of the nanocrystalline iron-based superconducting material is 10 nm to 200 nm, and the proportion of the Se-rich phase generated by phase separation of the nanocrystalline iron-based superconducting material is less than 10%.
[0008] The transition width ΔT in the MT curve of the nanocrystalline iron-based superconducting material is c Less than 3 K, the nanocrystalline iron-based superconducting material has a strong Texture, texture factor , Not less than 0.5.
[0009] The method for preparing the above-mentioned nanocrystalline iron-based superconducting material comprises the following steps:
[0010] S1: Melting the iron-based superconducting pre-melted body to obtain a melt with a superheat greater than 150°C;
[0011] S2: Rapidly cooling the superconducting melt to rapidly solidify the superconducting melt to obtain the nanocrystalline iron-based superconducting material, wherein the cooling rate is 10 5 ~10 6 ℃ / s.
[0012] Wherein, before step S1, the step of crushing the iron-based superconducting pre-melted green body is also included.
[0013] The heating temperature for melting in step S1 is 1050-1550°C.
[0014] In step S2, the superconducting melt is rapidly cooled by a single-roll spinning method, and the linear speed of the copper roller in the single-roll spinning method is greater than 5 m / s, preferably greater than 9 m / s.
[0015] In step S2, the superconducting melt is sprayed onto the surface of the rotating water-cooled copper roller using pressurized gas.
[0016] The pressurized gas is nitrogen or argon, and the pressure of the pressurized gas is 0.3-2.0 MPa.
[0017] Wherein, the iron-based superconducting material component is Ba 1-x K x (Fe 1-y Co y )2As2, where 0.1≦x≦0.7, 0≦y≦0.2;
[0018] Or the iron-based superconducting material component is FeSe z Te 1-z , where 0≦z≦0.8.
[0019] Wherein, the iron-based superconducting pre-melted green body is prepared by a solid phase reaction method.
[0020] The beneficial effects of the present invention are as follows:
[0021] (1) The average grain size of the nanocrystalline iron-based superconducting material of the present invention is 20-200 nm, and the critical current density reaches 1 × 10 4 A / cm 2 .
[0022] (2) The present invention utilizes a rapid cooling method to control the solidification rate of the iron-based superconducting material, causing it to cool rapidly, thereby suppressing phase separation and improving its superconducting performance. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1 The microscopic morphology of the samples obtained in Examples 1 to 3 and Comparative Example 1 is shown in FIG. Figure 1 (a) and (b) are microscopic morphologies of the samples obtained in Comparative Example 1. Figure 1 (c) is the microscopic morphology of the sample obtained in Example 1. Figure 1 (d) is the microscopic morphology of the sample obtained in Example 2. Figure 1 (e) is the microscopic morphology of the sample obtained in Example 3.
[0024] Figure 2 This is the XRD pattern of the pre-melted body prepared in step S0.
[0025] Figure 3 This is the SEM image of the pre-melted green body prepared in step S0.
[0026] Figure 4 This is the XRD pattern of the sample obtained in Example 1.
[0027] Figure 5 This is the XRD pattern of the sample obtained in Example 2.
[0028] Figure 6 This is the XRD pattern of the sample obtained in Example 3.
[0029] Figure 7 This is the SEM image of the sample obtained in Example 1, wherein: Figure 7 (a) is the sample roller surface. Figure 7 (b) in the figure is the free surface of the sample.
[0030] Figure 8 This is the SEM image of the sample obtained in Example 2, wherein: Figure 8 (c) in the figure is the sample roller surface. Figure 8 (d) in the figure is the free surface of the sample.
[0031] Figure 9 This is the SEM image of the sample obtained in Example 3, wherein: Figure 9 (e) in the figure is the sample roller surface. Figure 9 (f) in the figure is the free surface of the sample.
[0032] Figure 10 EPMA cross-sectional views of the samples obtained in Examples 1 to 3, wherein: Figure 10 (a) is a cross-sectional view of the sample of Example 1. Figure 10(b) is a cross-sectional view of the sample of Example 2. Figure 10 (c) is a cross-sectional view of the sample of Example 3.
[0033] Figure 11 This is the SEM image of the sample obtained in Example 4.
[0034] Figure 12 This is the electron probe elemental analysis result of the sample obtained in Example 4.
[0035] Figure 13 This is the SEM image of the sample obtained in Example 5.
[0036] Figure 14 This is the SEM image of the sample obtained in Example 6.
[0037] Figure 15 The XRD patterns of Examples 2 and 4 are shown.
[0038] Figure 16 MT curves of the samples obtained in Example 4 and Example 5.
[0039] Figure 17 These are the critical current surface density test curves of the samples obtained in Example 2 and Example 4. DETAILED DESCRIPTION
[0040] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
[0041] The basic idea of preparing nanocrystalline iron-based superconducting materials in the present invention is to use rapid solidification to achieve grain refinement and increase the grain boundary flux pinning ability.
[0042] The specific implementation steps are as follows:
[0043] Preparation process of iron-based superconducting pre-melted green body: one-step solid-phase reaction method or two-step solid-phase reaction method is used for preparation. The raw material element powder is ball-milled and mixed multiple times, and then pressed and sealed under inert atmosphere. Then, the solid-phase reaction precursor is obtained by one or two sintering under flowing argon. The sintering temperature range is 550-1000 ℃, and the holding time is 15-40 h.
[0044] The present invention preferably achieves rapid solidification through single-roll melt spinning technology, and uses a high-vacuum single-roll spinning system to complete this process. The pre-melted blank is broken and placed in a container with micropores at the lower end. The container is fixed to the inside of the equipment's induction coil, and the upper end is connected to the high-pressure gas circuit. Taking into account the poor conductivity of some samples, a graphite sleeve can be added between the container and the coil, and the heating process is indirectly completed by induction heating of the graphite. After the inside of the equipment is evacuated, the water-cooled copper roller is turned on, and induction heating is started after the target speed is set. After the blank is completely melted, the container is lowered so that the lower end of the container is basically close to the copper roller. The melt injection is completed by turning on the high-pressure gas, and the material is finally solidified to obtain a nanocrystalline thin ribbon. The induction heating temperature range is 850-1500 ° C, and the copper roller linear speed is higher than 5 m / s.
[0045] Example 1
[0046] S0: Preparation of pre-melted green body: Use high purity iron powder, Se powder and Te powder to synthesize the target composition of FeSe 0.5 Te 0.5 Solid-state reaction sample. The three raw materials were weighed, mixed and pressed into tablets according to the stoichiometric ratio; sealed in a stainless steel tube in an argon environment, heated to 600 ° C at a rate of 1 ° C / min in a muffle furnace and kept warm for 20 hours, cooled to room temperature with the furnace, and the obtained powder was taken out, ground again and pressed into tablets, and then heated to 600 ° C at a rate of 5 ° C / min and kept warm for 20 hours, cooled to room temperature with the furnace to obtain a pre-melted green body. This step is prepared by the secondary sintering method. The first sintering is slowly heated to avoid the volatilization of Se and Te as much as possible. Since the sample sintered for the first time is relatively loose and has low superconducting performance, a second sintering is required to densify the sample.
[0047] S1: The crushed pre-melted green body is placed in a quartz tube with an open bottom end and melted by graphite induction heating to 1200°C in a high vacuum single-roll quenching machine to form a complete melt;
[0048] S2: The melted sample turns into droplets and drips from the opening at the lower end of the glass tube onto the high-speed rotating copper roller below. The linear speed of the copper roller is 9m / s (the rotation speed of the copper roller is 800r / s). After being thrown out, the sample changes from a droplet to a thin ribbon to form a thin ribbon-shaped nanocrystalline iron-based superconducting material.
[0049] Example 2
[0050] The preparation process of Example 2 is the same as that of Example 1, except that the roller linear speed is 11 m / s (the rotation speed of the copper roller is 1000 r / s).
[0051] Example 3
[0052] The preparation process of Example 3 is the same as that of Example 1, except that the roller linear speed is 13 m / s (the rotation speed of the copper roller is 1200 r / s).
[0053] Comparative Example 1
[0054] A solid-state reaction sample with the target composition of FeSe0.5Te0.5 was synthesized using a melting method using high-purity iron powder, Se powder, and Te powder. The three raw materials were weighed, mixed, and pressed into tablets according to the stoichiometric ratio. The sample was then sealed in an argon atmosphere in a stainless steel tube and heated to 600°C in a muffle furnace at a rate of 1°C / min for 20 hours. The sample was then cooled to room temperature to obtain a comparative sample.
[0055] Figure 1 The microscopic morphology of the samples obtained in Examples 1 to 3 and Comparative Example 1 is shown in FIG. Figure 1 (a) and (b) are microscopic morphologies of the samples obtained in Comparative Example 1. Figure 1 (c) is the microscopic morphology of the sample obtained in Example 1. Figure 1 (d) is the microscopic morphology of the sample obtained in Example 2. Figure 1 (e) is the microscopic morphology of the sample obtained in Example 3. It can be seen that the FeSe-based superconductor prepared by the melt method has obvious phase separation behavior. This is because the melt is slowly cooled, which gives Se and Te atoms enough time to diffuse and undergo phase separation behavior, forming micron-scale Se-rich phase and Te-rich phase regions. The obvious two-phase separation structure can be seen in the figure. This coarse phase separation structure will significantly reduce the transmission capacity of superconducting current. The FeSe prepared in Examples 1 to 3 of the present invention 0.5 Te 0.5 The superconductor phase separation behavior is fully suppressed. Figure 1 The phase separation areas in (c), (d), and (e) are significantly smaller than those obtained by the melting method, indicating that the extremely fast cooling rate inhibits atomic diffusion and, consequently, phase separation. In particular, there is almost no phase separation in Examples 2 and 3.
[0056] Figure 2 is the XRD pattern of the pre-melted green body prepared in step S0, Figure 3 This is the SEM of the pre-melted green body prepared in step S0. Figure 2 It can be seen that after the secondary sintering, the superconducting phase has been formed. 0.5 Te 0.5In addition to the main phase, a partial hexagonal FeSe phase also exists. This is likely the result of a combination of thermodynamic and kinetic factors. Thermodynamically, the solid solution of FeSe and FeTe at the x = 0.5 composition may exhibit a tendency toward phase separation, with localized Se-rich regions favoring the formation of a stable hexagonal phase rather than a tetragonal superconducting phase (β-FeSe). Due to the difference in diffusion rates between Se and Te: Te atoms are larger and diffuse slower than Se, if the reaction time is insufficient (i.e., without annealing), Se may preferentially combine with Fe to form FeSe, while Te may not fully integrate into the crystal lattice. Furthermore, due to this tendency toward phase separation, local fluctuations in Se and Te concentrations may lead to the formation of the FeSe phase in the Se-rich regions. Kinetically, insufficient solid-state diffusion or insufficient sintering temperature / time can lead to uneven Se / Te distribution, resulting in residual unreacted FeSe. Rapid cooling, on the other hand, may suppress the formation of the tetragonal phase, preserving the high-temperature stable hexagonal phase. Furthermore, due to the two sintering steps, if the initial sintering is not completely uniform, this may exacerbate phase separation and indirectly promote the growth of the hexagonal phase.
[0057] from Figure 3 The sample exhibits a distinct polycrystalline structure, with uneven grain size distribution ranging from micrometers to submicrometers, and frequent particle agglomeration. This is primarily due to differential grain growth caused by incomplete atomic diffusion during sintering. Layered or flaky morphologies can be observed in some areas, reflecting the PbO-type tetragonal structure characteristic of the "11" iron-based superconductor system. However, this layered structure is often discontinuous due to random grain orientation. Furthermore, the image shows widespread pores and microcracks, which may be related to both the volatilization of Se / Te elements (especially the volatile Te) during sintering and the shrinkage stress generated during cooling.
[0058] Figures 4 to 6 The XRD results of Example 1 to Example 3 are refined. Figures 4 to 6 As can be seen in the figure, atoms do not have enough time to arrange themselves along specific crystal directions (such as the c-axis), resulting in a decrease in the preferred orientation along the 00l direction. High-speed cooling inhibits grain growth, forming nanoscale grains (<50 nm). Crystallization leads to broadening of XRD peaks, especially for low-index crystal planes (such as 001). When the cooling rate exceeds a critical value, amorphous phases may form in some areas, resulting in a weakening of long-range ordered crystal diffraction peaks (such as the 00l peak) and an increase in the diffuse scattering background. At the same time, high rotation speeds inhibit the diffusion and separation of Se / Te elements, promote the formation of a uniform Fe(Se,Te) solid solution, reduce the separation of Se-rich and Te-rich phases, and thus weaken the 00l characteristic peak of the original tetragonal phase (P4 / nmm).
[0059] Figure 7 The SEM images of the sample obtained in Example 1, wherein (a) is the roller-attached surface of the sample, and (b) is the free surface of the sample; Figure 8 The SEM images of the sample obtained in Example 2, wherein (c) is the roller-attached surface of the sample, and (d) is the free surface of the sample; Figure 9 The SEM images of the sample obtained in Example 3, where (e) is the roller-attached surface of the sample and (f) is the free surface of the sample. Figures 7 to 9 It can be seen that the grains of the samples prepared in Examples 1 to 3 are all at the nanometer level. Due to the asymmetry of solidification, two significantly different surfaces will be formed, the roller surface and the free surface. The roller surface is the side of the sample that directly contacts the copper roller, with an extremely fast cooling rate and a smoother and flatter surface; the smooth surface is in contact with air or a protective atmosphere, and has a relatively slow cooling rate. It can be seen from the figure that the grain size of the roller surface with a faster cooling rate is smaller than the grain size of the free surface with a slower cooling rate. The grains on the roller surface are fine, and the grains on the free surface are coarser. At the same time, the grain size of the sample with a roller speed of 1200r in Example 3 is also smaller than that of the other two samples. And the average grain size of the nanocrystalline iron-based superconducting material is 10 nm~200nm.
[0060] We characterized the element distribution of the three different samples prepared in Example 1 to Example 3 by EPMA surface scanning. Figure 10 Shown are cross-sectional views of three samples from Example 1 to Example 3, wherein: Figure 10 (a) is a cross-sectional view of the sample of Example 1. Figure 10 (b) is a cross-sectional view of the sample of Example 2. Figure 10 (c) is a cross-sectional view of the sample of Example 3, which mainly shows the distribution of Fe, Se, and Te on the side of the ribbon. Figure 10 It was found that when the copper roller rotates at a low speed, that is, when the cooling speed is slow, the Se and Te elements aggregate. As the cooling speed gradually increases, the component segregation of the two gradually disappears, and the ratio of the two gradually tends to balance, indicating that the faster the cooling speed, the weaker the phase separation will be, indicating that rapid cooling can effectively inhibit phase separation. At the same time, it can be seen that there is a significant difference in the grain size between the free surface and the roller surface. The faster the cooling speed, the smaller the grain size. The thickness of the three samples was measured and it was found that as the cooling speed increases, the thickness of the sample gradually decreases. Figure 10 It can be seen that when the roller speed is greater than 800r, the phase separation phenomenon of the nanocrystalline iron-based superconducting material almost disappears, and the proportion of the Se-rich phase generated by the phase separation of the nanocrystalline iron-based superconducting material is less than 10%.
[0061] Example 4
[0062] S0: Preparation of pre-melted green body: Use high purity iron powder, Se powder and Te powder to synthesize the target composition of FeSe 0.5 Te 0.5Solid-state reaction sample. The three raw materials were weighed, mixed and pressed into tablets according to the stoichiometric ratio; sealed in a stainless steel tube in an argon environment, heated to 600 ° C at a rate of 1 ° C / min in a muffle furnace and kept warm for 20 hours, cooled to room temperature with the furnace, and the obtained powder was taken out, ground again and pressed into tablets, and then heated to 600 ° C at a rate of 5 ° C / min and kept warm for 20 hours, cooled to room temperature with the furnace to obtain a pre-melted green body. This step is prepared by the secondary sintering method. The first sintering is slowly heated to avoid the volatilization of Se and Te as much as possible. Since the sample sintered for the first time is relatively loose and has low superconducting performance, a second sintering is required to densify the sample.
[0063] S1: The crushed pre-melted green body is placed in a quartz tube with an open bottom end and melted by graphite induction heating to 1200°C in a high vacuum single-roll quenching machine to form a complete melt;
[0064] S2: Use 2.0 MPa high-pressure argon gas to spray the melt onto a high-speed rotating copper roller below. The linear speed of the copper roller is 9 m / s (the rotation speed of the copper roller is 800 r / s). After the sample is thrown out, it changes from a droplet to a thin ribbon to form a thin ribbon-shaped nanocrystalline iron-based superconducting material.
[0065] Figure 11 The SEM image of the sample obtained in Example 4 is as follows. Figure 11 It can be seen that the particle size of the nano-iron-based superconducting material formed after pressurized injection is about nanometer scale, and its particle size is between 19nm and 140nm. Figure 12 The electron probe element analysis results of the sample obtained in Example 4 are shown in FIG. Figure 12 It can be seen that the sample obtained in Example 4 has almost no phase separation and the element distribution is relatively uniform.
[0066] Example 5
[0067] S0: Preparation of pre-melted green body: Use high purity iron powder, Se powder and Te powder to synthesize the target composition of FeSe 0.2 Te 0.8 The solid-state reaction sample was prepared by weighing, mixing, and pressing the three raw materials according to the stoichiometric ratio. The mixture was sealed in a stainless steel tube under an argon atmosphere and heated to 700°C in a muffle furnace at a rate of 1°C / min and held there for 20 h. The mixture was then cooled to room temperature to obtain a pre-melted blank.
[0068] S1: The crushed pre-melted green body is placed in a quartz tube with an open bottom end and melted by graphite induction heating to 1200°C in a high vacuum single-roll quenching machine to form a complete melt;
[0069] S2: Use 0.5 MPa high-pressure argon gas to spray the melt onto a high-speed rotating copper roller below. The linear speed of the copper roller is 11 m / s. After being thrown out, the sample changes from a droplet to a thin ribbon with an average grain size of about 150 nm.
[0070] Figure 13 It is the SEM picture of the sample obtained in Example 5. Figure 13 It can be seen that the particle sizes of the nanocrystalline iron-based superconducting materials formed in this embodiment are all nanometer-scale.
[0071] Example 6
[0072] S0: Preparation of pre-melted green body: Use high purity iron powder, Se powder and Te powder to synthesize the target composition of FeSe 0.2 Te 0.8 The solid-state reaction sample was prepared by weighing, mixing, and pressing the three raw materials according to the stoichiometric ratio. The mixture was sealed in a stainless steel tube under an argon atmosphere and heated to 700°C in a muffle furnace at a rate of 1°C / min and held there for 20 hours. The mixture was then cooled to room temperature to obtain a pre-melted blank.
[0073] S1: The crushed pre-melted green body is placed in a quartz tube with an open bottom end and melted by graphite induction heating to 1150°C in a high vacuum single-roll quenching machine to form a complete melt;
[0074] S2: Use 0.5 MPa high-pressure argon gas to spray the melt onto a high-speed rotating copper roller below. The linear speed of the copper roller is 9 m / s. After being thrown out, the sample changes from a droplet to a thin ribbon with an average grain size of about 200 nm.
[0075] Figure 14 It is the SEM picture of the sample obtained in Example 6. Figure 14 It can be seen that the particle sizes of the nanocrystalline iron-based superconducting materials formed in this embodiment are all nanometer-scale.
[0076] Example 7
[0077] S0: Preparation of pre-melted blank: Use high purity iron powder, cobalt powder, arsenic powder and Ba chips to synthesize the target composition of Ba(Fe 0.92 Co 0.08 )2As2 solid-state reaction sample. The three raw materials were weighed, mixed, and pressed according to the stoichiometric ratio. The mixture was sealed in a stainless steel tube under an argon atmosphere and heated to 900°C in a muffle furnace at a rate of 5°C / min for 35 hours. The mixture was then cooled to room temperature to obtain a pre-melted blank.
[0078] S1: The crushed pre-melted green body is placed in an alumina crucible with an open bottom end and melted by graphite induction heating to 1550°C in a high vacuum single-roll quenching machine to form a complete melt;
[0079] S2: Use 0.2 MPa high-pressure argon gas to spray the melt onto a high-speed rotating copper roller below. The linear speed of the copper roller is 13 m / s. After being thrown out, the sample changes from a droplet to a thin ribbon with an average grain size of about 100 nm.
[0080] Figure 15 The XRD patterns of Examples 2 and 4 are shown in FIG. Figure 15 It can be seen that the nanocrystalline iron-based superconducting material has a strong Texture, texture factor , Not less than 0.5.
[0081] Figure 16 MT curves of the samples obtained in Example 4 and Example 5. Figure 16 It can be seen that the transition width ΔT in the MT curve of the nanocrystalline iron-based superconducting material after pressurized injection is c Less than 3K.
[0082] Figure 17 The critical current surface density test curves of the samples obtained in Example 2 and Example 4 are shown in FIG. Figure 17 It can be seen from the graph that the critical current density of the sample obtained by pressurized injection is higher than that of the sample obtained without pressurization.
[0083] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.
[0084] Any portions not described in detail in this specification are known in the art. The above embodiments are provided for illustrative purposes only and are not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims. Various equivalent substitutions and modifications that do not depart from the spirit and principles of the present invention are intended to be encompassed within the scope of the present invention.
Claims
1. A nanocrystalline iron-based superconducting material, characterized in that: The average grain size of the nanocrystalline iron-based superconducting material is 10 nm to 200 nm, and the proportion of the Se-rich phase generated by phase separation of the nanocrystalline iron-based superconducting material is less than 10%.
2. The nanocrystalline iron-based superconducting material according to claim 1, characterized in that: The transition width ΔT in the MT curve of the nanocrystalline iron-based superconducting material c Less than 3 K, the nanocrystalline iron-based superconducting material has a strong Texture, texture factor , Not less than 0.
5.
3. The method for preparing the nanocrystalline iron-based superconducting material according to claim 1 or 2, characterized in that: The steps include: S1: Melting the iron-based superconducting pre-melted body to obtain a melt with a superheat greater than 150°C; S2: Rapidly cooling the superconducting melt to rapidly solidify the superconducting melt to obtain the nanocrystalline iron-based superconducting material, wherein the cooling rate is 10 5 ~10 6 ℃ / s.
4. The method for preparing nanocrystalline iron-based superconducting material according to claim 3, characterized in that: Before step S1, the method further includes the step of crushing the iron-based superconducting pre-melt green body.
5. The method for preparing nanocrystalline iron-based superconducting material according to claim 3, characterized in that: The heating temperature for melting in step S1 is 1050-1550°C.
6. The method for preparing nanocrystalline iron-based superconducting material according to claim 3, characterized in that: In step S2, the superconducting melt is rapidly cooled by a single-roll spinning method, wherein the linear speed of the copper roller in the single-roll spinning method is greater than 5 m / s.
7. The method for preparing nanocrystalline iron-based superconducting material according to claim 3, characterized in that: In step S2, the superconducting melt is sprayed onto the surface of the rotating water-cooled copper roller using pressurized gas.
8. The method for preparing nanocrystalline iron-based superconducting material according to claim 7, characterized in that: The pressurized gas is nitrogen or argon, and the pressure of the pressurized gas is 0.2-2.0 MPa.
9. The method for preparing nanocrystalline iron-based superconducting material according to claim 3, characterized in that: The iron-based superconducting material component is Ba 1-x K x (Fe 1-y Co y )2As2, where 0.1≦x≦0.7, 0≦y≦0.2; Or the iron-based superconducting material component is FeSe z Te 1-z , where 0≦z≦0.
8.
10. The method for preparing nanocrystalline iron-based superconducting material according to claim 3, characterized in that: The iron-based superconducting pre-melted green body is prepared by a solid phase reaction method.