Method for improving purity of iron-based superconducting material and iron-based superconducting material

Abstract

The invention discloses a method for improving the purity of an iron-based superconducting material and the iron-based superconducting material, and relates to the technical field of superconducting materials. The method comprises the following steps: performing high-temperature sintering on an adsorption material and an iron-based superconducting material raw powder blank in sintering equipment; wherein the adsorption material and the iron-based superconducting material raw powder blank are both located in an inner cavity of the sintering equipment; the temperature of the high-temperature sintering is 800-1200 DEG C, and the time of the high-temperature sintering is 1-120 hours. According to the method, through introduction of the porous or fiber adsorption material, impurities are effectively adsorbed in the high-temperature sintering process, impurity phases in the superconducting material are remarkably reduced, the method is more efficient than traditional vacuum sintering or inert atmosphere protection, and the purity and performance of the superconducting material can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of superconducting materials, and in particular to a method for improving the purity of an iron-based superconducting material and the iron-based superconducting material. Background Art

[0002] As an important branch of the high-temperature superconducting system, iron-based superconducting materials have become one of the new high-temperature superconducting materials that are most likely to achieve high-field and high-power applications since they were discovered in 2008, thanks to their high transition temperature, high critical current density, high upper critical field, low anisotropy and low cost. The iron-based superconducting material system is huge. According to the differences in crystal structure, there are multiple systems such as 1111, 122, 111, and 11. The 122-type iron-based superconductor has become the most widely studied and most practical iron-based superconducting system due to its unique crystal structure, high critical current density, low anisotropy and mature preparation process. The stable preparation of high-quality iron-based superconducting materials is the prerequisite for the practical application and industrialization of iron-based superconductors.

[0003] However, since iron-based superconducting materials generally contain nitrogen (such as arsenic) or sulfur (such as sulfur, selenium, tellurium) elements in addition to iron, and may contain alkaline earth metals, alkali metal elements or other elements (such as rare earths and transition metals), component volatilization and stoichiometric imbalance are prone to occur during the high-temperature synthesis process, which in turn leads to three key material defects: (1) segregation of lattice doping elements; (2) formation of non-stoichiometric compounds; (3) precipitation of a large amount of residual second phases such as iron-arsenic impurities, iron particles, arsenic elements, barium oxide, potassium arsenide, etc. These structural defects not only lead to a decrease in the purity of the superconducting phase, but also seriously restrict the improvement of the critical current carrying capacity and flux pinning characteristics of the material, becoming one of the main technical bottlenecks hindering the large-scale application of iron-based superconducting materials. Summary of the invention

[0004] In view of this, the object of the present invention is to provide a method for increasing the purity of an iron-based superconducting material. The iron-based superconducting material prepared by the method provided by the present invention has stable chemical composition, uniform element distribution, and no obvious impurity phase.

[0005] A further technical problem to be solved by the present invention is to provide an iron-based superconducting material.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme:

[0007] A method for improving the purity of an iron-based superconducting material, the method comprising: sintering an adsorption material and a green powder of the iron-based superconducting material together at high temperature in a sintering device; wherein the adsorption material and the green powder of the iron-based superconducting material are both located in an inner cavity of the sintering device; the temperature of the high-temperature sintering is 800-1200° C., and the time of the high-temperature sintering is 1-120 hours.

[0008] Among them, the distance between the adsorption material and the green compact of the iron-based superconducting material is 0 cm - 15 cm (preferably 0 cm - 10 cm).

[0009] Among them, the adsorption material is coated on the surface of the green compact of the iron-based superconducting material, or the adsorption material is placed above, below, to the left, to the right, and around the green compact of the iron-based superconducting material.

[0010] Among them, the adsorption material is a porous adsorption material or a fibrous adsorption material.

[0011] Among them, the porous adsorption materials include: carbon-based porous materials, inorganic porous materials, polymer porous materials, composite and modified materials, biological substances and natural porous materials, and other new materials; the fibrous adsorption materials include inorganic fibers, natural fibers, or synthetic fibers.

[0012] Among them, the ratio of the mass of the adsorption material to the mass of the green compact of the iron-based superconducting material is (0.01~1):(0.01~1), preferably (0.05~1):(0.25~1).

[0013] Among them, the high-temperature sintering is carried out in an inert atmosphere or a vacuum environment with a pressure of 10 -3 Pa - 0.1 MPa.

[0014] Among them, the sintering procedure of the high-temperature sintering is: heating up to 400 - 700 °C at a rate of 50 - 1000 °C / h and holding for 0.5 - 25 hours, and then heating up to 800 - 1200 °C at a rate of 50 - 800 °C / h and holding for 1 - 120 hours.

[0015] An iron-based superconducting material is prepared by the method for improving the purity of the iron-based superconducting material as described above, and the purity of the superconducting material is greater than 99.6%.

[0016] The beneficial effects of the present invention are as follows:

[0017] (1) By introducing a porous or fibrous adsorption material, the method of the present invention effectively adsorbs impurities (such as iron arsenide heterophase, iron particles, barium oxide, residual alkaline earth / alkali metals, etc.) during the high-temperature sintering process, significantly reducing the internal heterophase of the superconducting material. This method is more efficient than traditional vacuum sintering or inert atmosphere protection, and can effectively improve the purity and performance of the superconducting material.

[0018] (2) The method of the present invention is applicable to various iron-based superconducting materials, such as "1111" type, "11" type, "122" type, "111" type, and "1144" type, "12442" type and other various iron-based superconducting systems, and has universality and strong application extensibility.

[0019] (3) The method of the present invention only requires vacuum or atmospheric pressure sintering, without the need for high-pressure equipment and without multiple sinterings. The process is simple and reliable, and significantly reduces the preparation cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is the X-ray diffraction pattern of the iron-based superconducting material prepared in Example 4 of the present invention and the standard X-ray diffraction pattern of BaK122.

[0021] Figure 2 It is the SEM pattern of the product obtained in the comparative example of the present invention (sintered without adding an adsorbent material).

[0022] Figure 3 It is the SEM pattern of the iron-based superconducting material prepared in Example 4 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be 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 used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0024] Unless otherwise specified, the raw materials and equipment used in the embodiments of the present invention are all commercially available.

[0025] A method for improving the purity of an iron-based superconducting material, wherein the method is to perform high-temperature sintering of an adsorbent material and a green compact of the iron-based superconducting material together in a sintering device; wherein both the adsorbent material and the green compact of the iron-based superconducting material are located in the inner cavity of the sintering device; the temperature of the high-temperature sintering is 800-1200 °C, and the time of the high-temperature sintering is 1 to 120 hours.

[0026] Among them, the green compact of the iron-based superconducting material can be the green powder obtained by uniformly mixing the raw materials, or the green compact obtained by pressing and forming. The pressing and forming specifically includes the following steps:

[0027] (1) In an inert atmosphere, the raw materials are proportioned and mixed uniformly according to the chemical formula of the iron-based superconducting material to obtain an unreacted green powder. The raw materials can be alkaline earth metal elements or compounds, rare earth metal elements or compounds, alkali metal elements or compounds, iron elements or compounds, arsenic elements or compounds;

[0028] (2) The green powder of the iron-based superconducting material can be obtained by pressing the green powder in step (1) in an inert atmosphere. The pressure used for pressing is 0.1 MPa - 1 GPa. For example, the pressure used for pressing is 0.1 MPa, 10 MPa, 30 MPa, 500 MPa or 1 GPa. The shape of the formed sample includes cylindrical, cuboid or spherical.

[0029] Preferably, the distance between the adsorbent material and the green powder of the iron-based superconducting material is 0 cm - 15 cm (for example, 0.01 cm, 0.02 cm, 0.04 cm, 0.1 cm, 0.5 cm, 1 cm, 3 cm, 8 cm, 10 cm or 15 cm).

[0030] Furthermore, the adsorbent material is coated on the surface of the green powder of the iron-based superconducting material, or the adsorbent material is placed above, below, on the left side, on the right side and around the green powder of the iron-based superconducting material.

[0031] Among them, the adsorbent material is a porous adsorbent material or a fibrous adsorbent material.

[0032] Furthermore, the porous adsorbent materials in step (3) include: carbon-based porous materials (such as activated carbon, activated carbon fiber, graphene-based materials, carbon nanotubes, porous carbon aerogel), inorganic porous materials (such as zeolite molecular sieve, silica gel, activated alumina, bentonite, metal-organic framework), polymer porous materials (such as adsorption resin, hypercrosslinked polymer, porous rubber / foam plastic), composite and modified materials (such as MOF-based composite materials, carbon-inorganic hybrid materials, aerogel composite materials), biological substances and natural porous materials (such as biochar, diatomite, natural zeolite) and other new materials (such as porous ceramics, metal foam materials); fiber materials include inorganic fibers (such as quartz glass fiber, boron fiber, ceramic fiber, metal fiber, etc.), natural fibers (such as plant fiber and animal fiber), synthetic fibers (such as polyester fiber, polyaramide fiber, etc.).

[0033] Among them, the ratio of the mass of the adsorbent material to the mass of the green powder of the iron-based superconducting material is (0.01~1):(0.01~1).

[0034] Further, the porosity of the porous or fibrous adsorption material can be selected according to process requirements from porous adsorption materials with different porosities. When the mass of the raw iron-based superconducting material powder is greater than or equal to 3 kg, a super-high porosity (>80%) adsorption material is preferably selected, such as metal-organic frameworks, activated carbon fibers, and aerogels; when the mass of the raw iron-based superconducting material powder is greater than or equal to 1 kg, a high porosity (60%-80%) adsorption material is preferably selected, such as conventional activated carbon, mesoporous silica, and porous polymer resins; when the mass of the raw iron-based superconducting material powder is greater than or equal to 0.1 kg, a medium porosity (30%-60%) adsorption material is preferably selected, such as zeolite molecular sieves and sintered metal porous materials; when the mass of the raw iron-based superconducting material powder is less than 0.1 kg, a low porosity (<30%) adsorption material is preferably selected, such as dense ceramic materials.

[0035] Preferably, the high-temperature sintering is carried out in an inert atmosphere or a vacuum environment with a pressure of 10 -3 Pa - 0.1 MPa.

[0036] Further, the high-temperature sintering procedure is as follows: heating at a rate of 50 - 1000 °C / h (for example, at a rate of 100 °C / h, 200 °C / h, 300 °C / h, 400 °C / h, 500 °C / h, 600 °C / h, 700 °C / h, 800 °C / h, 900 °C / h or 1000 °C / h) to 400 - 700 °C (for example, 400 °C, 450 °C, 500 °C, 550 °C, 600 °C, 650 °C or 700 °C) and holding for 0.5 - 25 hours, then heating at a rate of 50 - 800 °C / h (for example, at a rate of 100 °C / h, 150 °C / h, 200 °C / h, 250 °C / h, 300 °C / h, 350 °C / h, 400 °C / h, 450 °C / h, 500 °C / h, 550 °C / h or 600 °C / h) to 800 - 1200 °C (for example, 800 °C, 850 °C, 900 °C, 950 °C, 1000 °C, 1050 °C, 1100 °C, 1150 °C or 1200 °C) and holding for 1 - 120 hours.

[0037] Preferably, the sintering procedure of the high-temperature sintering is: heating at a rate of 50 - 900 °C / h to 450 - 700 °C and holding for 0.5 - 25 hours, then heating at a rate of 50 - 780 °C / h to 820 - 1200 °C and holding for 1.5 - 120 hours.

[0038] Example 1:

[0039] A method for improving the purity of an iron-based superconducting material, comprising the following steps:

[0040] (1) In an argon atmosphere, barium, potassium, iron and arsenic elements are combined according to the chemical formula Ba 0.6 K 0.5Mix Fe₂As₂ in proportion and mix evenly to obtain unreacted raw powder;

[0041] (2) In an argon atmosphere, press the raw powder in step (1) into a cylindrical shape under a pressure of 10 MPa;

[0042] (3) Select activated carbon as the adsorbent material. The ratio of the mass of activated carbon to the mass of the pressed raw powder is 0.05:1, and place the activated carbon 5 cm above the pressed raw powder;

[0043] (4) In an argon atmosphere with a pressure of 0.03 MPa, sinter the activated carbon and the pressed raw powder in step (3) at high temperature together. The powder is sintered into a bulk material. The sintering process is as follows: heat up to 500 °C at a rate of 50 °C / h and hold for 18 hours, then heat up to 850 °C at a rate of 100 °C / h and hold for 100 hours.

[0044] The obtained iron-based superconducting material is tested by synchrotron X-ray diffraction, and it is found that the purity of the superconducting phase is as high as 99.65%. Through scanning electron microscope testing, it is found that the grain distribution of the sample is uniform and there is no obvious impurity phase between grains. Through scanning electron probe testing, it is found that there is no segregation phenomenon in the sample, and the measured actual chemical composition is Ba 0.501 K 0.409 Fe 2.003 As 1.998 .

[0045] Example 2:

[0046] A method for improving the purity of iron-based superconducting materials, including the following steps:

[0047] (1) In a nitrogen atmosphere, mix strontium, sodium, iron and arsenic elements according to the chemical formula Sr 0.83 Na 0.23 Fe₂As 2.05 in proportion and mix evenly to obtain unreacted raw powder;

[0048] (2) In a nitrogen atmosphere, press the raw powder in step (1) into a cuboid shape under a pressure of 0.1 MPa;

[0049] (3) Select activated alumina as the adsorbent material. The ratio of the mass of activated alumina to the mass of the pressed raw powder is 1:0.25, and place the activated carbon 0.5 cm below the pressed raw powder;

[0050] (4) In a vacuum environment with a pressure of 0.1 Pa, sinter the activated alumina and the pressed raw powder in step (3) at high temperature together. The powder is sintered into a bulk material. The sintering process is as follows: heat up to 600 °C at a rate of 400 °C / h and hold for 15 hours, then heat up to 820 °C at a rate of 300 °C / h and hold for 66 hours.

[0051] The obtained iron-based superconducting material was tested by synchrotron X-ray diffraction, and it was found that the purity of the superconducting phase was as high as 99.73%. Through scanning electron microscope testing, it was found that the sample grain distribution was uniform and there was no obvious impurity phase between grains. Through scanning electron probe testing, it was found that there was no segregation phenomenon in the sample, and the measured actual chemical composition was Sr 0.806 Na 0.195 Fe 1.997 As 2.001 。

[0052] Example 3:

[0053] A method for improving the purity of an iron-based superconducting material, comprising the following steps:

[0054] (1) In an argon atmosphere, barium arsenide, potassium arsenide, iron arsenide and arsenic were proportioned according to the chemical formula Ba 0.7 K 0.35 Fe2As 2.01 and mixed evenly to obtain unreacted raw powder;

[0055] (2) In an argon atmosphere, the raw powder in step (1) was pressed into a spherical shape under a pressure of 500 MPa;

[0056] (3) Porous graphene was selected as the adsorbent material, and the mass ratio of porous graphene to the pressed raw powder was 0.35:0.73. The graphene was coated on the surface of the pressed raw powder, and the surface spacing was 0 cm;

[0057] (4) In an argon atmosphere with a pressure of 0.01 MPa, the porous graphene and the pressed raw powder in step (3) were sintered at high temperature together, and the powder was sintered into a bulk material. The sintering procedure was: heating to 700 °C at a rate of 900 °C / h and holding for 0.5 hour, then heating to 1050 °C at a rate of 150 °C / h and holding for 70 hours.

[0058] The obtained iron-based superconducting material was tested by synchrotron X-ray diffraction, and it was found that the purity of the superconducting phase was as high as 99.81%. Through scanning electron microscope testing, it was found that the sample grain distribution was uniform and there was no obvious impurity phase between grains. Through scanning electron probe testing, it was found that there was no segregation phenomenon in the sample, and the measured actual chemical composition was Ba 0.701 K 0.315 Fe 2.006 As 1.986 。

[0059] Example 4:

[0060] A method for improving the purity of an iron-based superconducting material, comprising the following steps:

[0061] (1) In a nitrogen atmosphere, barium arsenide, potassium arsenide, iron, and arsenic are proportioned and mixed evenly according to the chemical formula Ba 0.65 K 0.45 Fe 1.98 As 2.06 to obtain unreacted raw powder;

[0062] (2) In a nitrogen atmosphere, the raw powder in step (1) is pressed into a cylindrical shape under a pressure of 500 MPa;

[0063] (3) Select aluminosilicate ceramic fiber as the adsorbent material. The mass ratio of aluminosilicate ceramic fiber to the pressed raw powder is 0.1:0.75, and the aluminosilicate ceramic fiber is placed 8.5 cm to the right of the pressed raw powder;

[0064] (4) In an argon atmosphere with a pressure of 0.05 MPa, the aluminosilicate ceramic fiber and the pressed raw powder in step (3) are sintered at high temperature together, and the powder is sintered into a bulk material. The sintering procedure is as follows: heating up to 450 °C at a rate of 450 °C / h and holding for 12 hours, then heating up to 1200 °C at a rate of 350 °C / h and holding for 1.5 hours.

[0065] The obtained iron-based superconducting material is tested by synchrotron X-ray diffraction, and it is found that the purity of the superconducting phase is as high as 99.69%. Through scanning electron microscope testing, it is found that the grain distribution of the sample has no obvious impurity phase between grains. Through scanning electron probe testing, it is found that there is no segregation phenomenon in the sample, and the measured actual chemical composition is Ba 0.647 K 0.437 Fe 1.968 As 1.996 .

[0066] Comparative Example

[0067] The preparation steps are the same as those in Example 4, except that no adsorbent is used.

[0068] Figure 1 This is the X-ray diffraction pattern of the iron-based superconducting material prepared in Example 4 of the present invention and the standard X-ray diffraction pattern of BaK122. The diffraction height peaks of the two coincide and do not contain impurity phase peaks, indicating that the superconducting material has high purity.

[0069] Figure 2 This is the SEM image of the product obtained by sintering without adding an adsorbent material in the comparative example of the present invention. It can be seen from Figure 2 that most of the grains of the product obtained without adding an adsorbent material are irregular flakes, and there are many flocculent impurity phases between grains and on the grain surfaces, which is particularly obvious at the red circle mark.

[0070] Figure 3 This is the SEM image of the iron-based superconducting material prepared in Example 4 of the present invention, compared withFigure 2 It can be seen from the comparison that the superconducting material prepared by the present invention has a uniform grain distribution, and there are no obvious impurity phases between grains and on the grain surfaces.

[0071] Example 5:

[0072] A method for improving the purity of an iron-based superconducting material, comprising the following steps:

[0073] (1) In an argon atmosphere, barium, rubidium, iron and arsenic elements are proportioned according to the chemical formula Ba 0.4 Rb 0.7 Fe2As 2.02 and mixed evenly to obtain unreacted raw powder;

[0074] (2) In an argon atmosphere, the raw powder in step (1) is pressed into a sphere under a pressure of 60 MPa;

[0075] (3) Select natural zeolite as the adsorbent material. The ratio of the mass of natural zeolite to the mass of the pressed raw powder is 1:1, and the natural zeolite is placed 4.5 cm behind the left rear of the pressed raw powder;

[0076] (4) In a vacuum environment with a pressure of 10 -3 Pa, the natural zeolite and the pressed raw powder in step (3) are heated together, and the powder is sintered into a bulk material. The sintering program is: heating to 620 °C at a rate of 550 °C / h and holding for 4.5 hours, and then heating to 1120 °C at a rate of 780 °C / h and holding for 3.5 hours.

[0077] The obtained iron-based superconducting material was tested by synchrotron X-ray diffraction, and it was found that the purity of the superconducting phase was as high as 99.78%. Through scanning electron microscope testing, it was found that the grain distribution of the sample was uniform and there were no obvious impurity phases between grains. Through scanning electron probe testing, it was found that there was no segregation phenomenon in the sample, and the measured actual chemical composition was Ba 0.401 Rb 0.617 Fe 1.993 As 2.002 .

[0078] Example 6:

[0079] A method for improving the purity of an iron-based superconducting material, comprising the following steps:

[0080] (1) In a nitrogen atmosphere, strontium, potassium arsenide, iron and arsenic are proportioned according to the chemical formula Sr 0.6 K 0.5 Fe 1.95 As 2.08 and mixed evenly to obtain unreacted raw powder;

[0081] (2) In a nitrogen atmosphere, the raw powder in step (1) is pressed into a cuboid shape under a pressure of 0.25 GPa;

[0082] (3) Select quartz wool as the adsorbent material. The ratio of the mass of quartz wool to the mass of the pressed raw powder is 0.07:0.86. Place the quartz wool 1.5 cm directly below the pressed raw powder;

[0083] (4) In a nitrogen atmosphere environment with a pressure of 0.025 MPa, the quartz wool and the pressed raw powder in step (3) are sintered at high temperature together. The powder is sintered into a bulk material. The sintering procedure is: heat up to 550 °C at a rate of 200 °C / h and hold for 2 hours, then heat up to 1050 °C at a rate of 50 °C / h and hold for 100 hours.

[0084] The obtained iron-based superconducting material is tested by synchrotron X-ray diffraction, and it is found that the purity of the superconducting phase is as high as 99.83%. Through scanning electron microscope testing, it is found that the grain distribution of the sample is such that there are no obvious impurity phases between the grains. Through scanning electron probe testing, it is found that there is no segregation phenomenon in the sample. The measured actual chemical composition is Sr 0.569 K 0.436 Fe 1.933 As 2.075 .

[0085] Example 7:

[0086] A method for improving the purity of an iron-based superconducting material, comprising the following steps:

[0087] (1) In a nitrogen atmosphere, iron, tellurium and selenium are proportioned and mixed evenly according to the chemical formula FeTe 0.8 Se 0.2 to obtain unreacted raw powder;

[0088] (2) In a nitrogen atmosphere, the raw powder in step (1) is pressed into a cylindrical shape under a pressure of 20 MPa;

[0089] (3) Select activated carbon as the adsorbent material. The ratio of the mass of activated carbon to the mass of the pressed raw powder is 0.1:1. Place the activated carbon 5 cm to the right of the pressed raw powder;

[0090] (4) In an argon atmosphere environment with a pressure of 0.05 MPa, the activated carbon and the pressed raw powder in step (3) are sintered at high temperature together. The powder is sintered into a bulk material. The sintering procedure is: heat up to 550 °C at a rate of 250 °C / h and hold for 10 hours, then heat up to 1100 °C at a rate of 300 °C / h and hold for 3 hours.

[0091] The obtained iron-based superconducting material was tested by synchrotron X-ray diffraction, and it was found that the superconducting phase purity was as high as 99.66%. Through scanning electron microscope testing, it was found that the sample grain distribution had no obvious impurity phase between grains. Through scanning electron probe testing, it was found that there was no segregation phenomenon in the sample, and the measured actual chemical composition was FeTe 0.802 Se 0.199 。

[0092] Example 8:

[0093] A method for improving the purity of iron-based superconducting materials, comprising the following steps:

[0094] (1) In an argon atmosphere, LaAs, Fe2As, RbAs and NaAs were proportioned and mixed evenly according to the chemical formula (La,Na)RbFe4As4 to obtain unreacted raw powder;

[0095] (2) A porous ceramic was selected as the adsorbent material, and the ratio of the mass of the porous ceramic to the mass of the unreacted raw powder was 0.3:1. The porous ceramic was placed 0.5 cm below the pressed raw powder;

[0096] (4) In a vacuum environment with a pressure of 10 -3 Pa, the porous ceramic and the unreacted raw powder in step (3) were subjected to high-temperature sintering treatment together. The sintering procedure was: heating to 700 °C at a rate of 200 °C / h and holding for 25 hours, and then heating to 1200 °C at a rate of 250 °C / h and holding for 55 hours.

[0097] The obtained iron-based superconducting material was tested by synchrotron X-ray diffraction, and it was found that the superconducting phase purity was as high as 99.78%. Through scanning electron microscope testing, it was found that the sample grain distribution had no obvious impurity phase between grains. Through scanning electron probe testing, it was found that there was no segregation phenomenon in the sample, and the measured actual chemical composition was (La,Na)RbFe4As4.

[0098] Example 9:

[0099] A method for improving the purity of iron-based superconducting materials, comprising the following steps:

[0100] (1) In an argon atmosphere, LnAs, Fe powder, Fe2O3 powder and FeF3 powder were proportioned and mixed evenly according to the chemical formula LnO 0.9 F 0.11 FeAs to obtain unreacted raw powder;

[0101] (2) In an argon atmosphere, the raw powder in step (1) was pressed into a cylindrical shape under a pressure of 15 MPa;

[0102] (3)Select aluminum silicate fiber as the adsorbent material. The mass ratio of aluminum silicate fiber to the pressed raw powder is 0.05:0.78. Place the aluminum silicate fiber 2.5 cm above the pressed raw powder.

[0103] (4)In an argon atmosphere environment with a pressure of 0.06 MPa, sinter the aluminum silicate fiber and the pressed raw powder in step (3) at high temperature. The powder is sintered into a bulk material. The sintering procedure is as follows: Heat up to 500 °C at a rate of 150 °C / h and hold for 15 hours, then heat up to 980 °C at a rate of 240 °C / h and hold for 30 hours.

[0104] The obtained iron-based superconducting material is tested by synchrotron X-ray diffraction. It is found that the purity of the superconducting phase is as high as 99.73%. Through scanning electron microscope testing, it is found that the grain distribution of the sample is such that there are no obvious impurity phases between grains. Through scanning electron probe testing, it is found that there is no segregation phenomenon in the sample. The measured actual chemical composition is LnO 0.9 F 0.101 FeAs.

[0105] Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

[0106] The parts not elaborated in detail in the specification of the present invention belong to the well-known technology in the art. The above embodiments are provided only for the purpose of describing the present invention and are not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims. All equivalent replacements and modifications made without departing from the spirit and principles of the present invention shall be covered within the scope of the present invention.

Claims

1. A method for improving the purity of iron-based superconducting materials, characterized in that, The method is to perform high-temperature sintering on the adsorbent material and the green compact of the iron-based superconducting material together in a sintering device; wherein both the adsorbent material and the green compact of the iron-based superconducting material are located in the inner cavity of the sintering device; the temperature of the high-temperature sintering is 800 - 1200 °C, and the time of the high-temperature sintering is 1 - 120 hours.

2. The method for improving the purity of the iron-based superconducting material according to claim 1, wherein The distance between the adsorbent material and the green compact of the iron-based superconducting material is 0 cm - 15 cm.

3. The method for improving the purity of the iron-based superconducting material according to claim 2, characterized in that The adsorbent material is laid on the surface of the green compact of the iron-based superconducting material, or the adsorbent material is placed above, below, on the left side, on the right side, and around the green compact of the iron-based superconducting material.

4. The method for improving the purity of the iron-based superconducting material according to claim 1, wherein The adsorbent material is a porous adsorbent material or a fibrous adsorbent material.

5. The method for improving the purity of the iron-based superconducting material according to claim 4, characterized in that The porous adsorbent material includes: carbon-based porous materials, inorganic porous materials, polymer porous materials, composite and modified materials, biological substances and natural porous materials, and other new materials; the fibrous adsorbent material includes inorganic fibers, natural fibers, or synthetic fibers.

6. The method for improving the purity of the iron-based superconducting material according to claim 1, characterized in that The ratio of the mass of the adsorbent material to the mass of the green compact of the iron-based superconducting material is (0.01 - 1):(0.01 - 1).

7. The method for improving the purity of the iron-based superconducting material according to claim 1, wherein The high-temperature sintering is carried out in an inert atmosphere or a vacuum environment with a pressure of 10 -3 Pa - 0.1 MPa.

8. The method for improving the purity of the iron-based superconducting material according to claim 1, wherein The sintering procedure of the high-temperature sintering is: heating up to 400 - 700 °C at a rate of 50 - 1000 °C / h and holding for 0.5 - 25 hours, and then heating up to 800 - 1200 °C at a rate of 50 - 800 °C / h and holding for 1 - 120 hours.

9. A iron-based superconducting material, characterized in that The iron-based superconducting material is prepared by using the method for improving the purity of the iron-based superconducting material according to any one of claims 1 to 8, and the purity of the iron-based superconducting material is greater than 99.6%.

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