Preparation method of high-density FeSe1-xTex superconducting target material

Abstract

The invention discloses a preparation method of a high-density FeSe1-xTex superconducting target material, which mainly comprises the following steps: taking Fe, Se and Te powder as raw materials, weighing the powder according to the stoichiometric ratio of FeSe1-xTex (x = 0.01-1), carrying out ball milling and mixing on the powder, and packaging in a vacuum quartz tube for sintering to obtain FST superconductor powder; sintering the FST superconductor powder by a self-service solvent method to obtain a single phase, uniformly mixing by a planetary ball milling method to obtain single-phase FST powder, loading the single-phase FST powder into a graphite grinding tool, and sintering into a target by low-temperature hot pressing to obtain the FST superconductor target material with high density, uniform components and high critical current density. According to the preparation method, FeSe1-xTex powder subjected to low-temperature pretreatment is adopted as precursor powder, single-crystal FeSe1-xTex powder is obtained through a self-service solvent method, uniform mixing and block powdering are conducted through planetary ball milling, then low-temperature hot pressing sintering is conducted, the grain connectivity compactness of the target material is improved, and therefore the critical current density of the target material is remarkably improved. The method is simple, is suitable for preparing the superconducting target material, is beneficial to large-scale popularization and application, and has huge commercial value.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-temperature superconducting material preparation methods, and specifically relates to a high-density FeSe 1-x Te x (Abbreviation: FST) method for preparing superconducting target materials. Background Art

[0002] High-temperature superconducting materials usually refer to superconductors that work above liquid nitrogen temperature (77 K), which is relative to low-temperature superconductors such as Hg and Pb. Its superconducting mechanism is still an unsolved mystery in the frontier research of condensed matter physics. Therefore, in order to completely unveil the veil of high-temperature superconductivity, people urgently need to find a new family of high-temperature superconductors to open up more research paths. Iron-based superconductors are the second type of high-temperature superconductors. Because of their advantages such as high upper critical field, superconducting transition temperature, high critical current density and low anisotropy, they have become ideal candidates for high-field applications of superconducting materials.

[0003] The "11" series in the iron-based superconductor family has become the preferred material for exploring the mechanism of high-temperature superconductivity and the application of high-field materials due to its advantages such as non-toxicity and easier preparation. At present, material preparation is mainly concentrated on bulk materials, wires and films. Bulk materials are easy to prepare, but the formation of multiple phases cannot be avoided. Wires have problems such as uneven reaction and brittleness. Compared with bulk materials and wires, superconducting films can prepare stable single phases in bulk materials, while solving the brittleness problem in wires. They are also more suitable for the manufacture of devices and superconducting targets. However, for high-quality films, the target material is the most critical factor. High-performance targets usually have a single phase, high density and high superconducting transition temperature to ensure the acquisition of high-quality films.

[0004] FeSe 1-x Te x (abbreviation: FST) superconductor is a typical high-temperature superconductor, the superconducting transition temperature T c =14~15K, H c2 At 4.2 K, it can reach up to 100 T, and the anisotropy is very small. Se in FST superconductors can be partially replaced by Te. H c2 The raw material cost is low and the preparation method is very simple. Therefore, it is considered to have potential application value in the field of high magnetic field superconducting target materials.

[0005] At present, the targets on the market are mainly made by mixing and sintering compound powders, such as FeSe2 powder and FeTe powder. After mixing evenly, they are sintered by solid phase combination and then hot pressed. It is difficult to prepare a single-phase film by mixing compound powders, so it is difficult to obtain a high-quality film. At present, most research groups use the solid phase synthesis polycrystalline method or direct hot pressing method to prepare iron-based targets. According to the Fe-Se phase diagram, the window for generating a single phase is very narrow, so it is difficult to obtain a single phase. Although the direct hot pressing method can effectively improve the density of the target material, it is difficult to control the phase formation. Therefore, the FST target prepared by the existing preparation method still cannot achieve the preparation of large-scale high-quality films. Based on the above situation, the present invention proposes a preparation method of a high-density FST superconducting target material suitable for industrial production. The method uses ordinary high-purity Fe, Se and Te powders as raw materials, which are then fully ball-milled and mixed, and then loaded into a quartz tube. They are first subjected to a low-temperature pre-reaction, then a high-temperature combination, and then the temperature is reduced to obtain a precursor superconducting powder; then, they are ground and mixed again, and finally hot-pressed at low temperature and high pressure to obtain a high-performance FST superconducting target material, which can meet the requirements of obtaining a single-phase high-quality thin film. Summary of the invention

[0006] The object of the present invention is to provide a method for preparing a high-density FST superconducting target material. The preparation method is simple and easy to promote, and can obtain single-phase high-quality thin film strips and device preparation.

[0007] The technical solution adopted by the present invention is: using Fe, Se and Te powder as raw materials, according to the stoichiometric ratio of FeSe 1-x Te x (x=0.1~1) The powder is weighed, the powder is mixed by ball milling, and then packaged in a vacuum quartz tube and sintered to obtain FST superconductor precursor powder; the FST superconductor precursor powder is then ball milled to obtain uniform FST powder, and the powder is loaded into a graphite mold, and then hot-pressed and sintered under vacuum conditions, and finally, after furnace heat and cold treatment, a FST superconducting target with high density, good grain connectivity and uniform composition is obtained.

[0008] The present invention is also characterized in that the FST superconducting powder pretreated at low temperature is used as raw material, a single-phase crystal is prepared by a high-temperature self-solvent method, and then sintered by low-temperature hot pressing to improve the problem of multiple impurities in the polycrystalline target superconductor, while ensuring the uniformity of the superconducting target composition. The preparation cost is low, the process is simple and the preparation cycle is short. Specifically, the following steps are included: Step 1: FST powder sintering Fe, Se and Te powders were used as raw materials. 1-x Te x The powders with a stoichiometric ratio of x = 0.01 to 0.99 were weighed, mixed evenly, and sealed in a vacuum quartz tube and heated to 600o C ~1100 o C, keep warm for 2 h~36 h to obtain FST superconductor precursor powder; Step 2: Single-phase FST superconducting powder preparation The FST superconductor precursor powder obtained in step 1 was mixed evenly for 5 min, sealed in a quartz tube again, and heated to 700 o C ~1100 o C, after cooling, the powder was subjected to planetary milling for 1 h to 10 h under Ar atmosphere protection at a ball weight ratio of 10:1 to obtain uniform and unreacted FST superconductor powder; Step 3: Hot pressing FST superconducting target preparation The FST superconducting powder obtained in step 2 is loaded into a graphite film mold, and then subjected to low-temperature pretreatment and hot-pressing sintering to obtain a high-density FST superconducting target.

[0009] In the above step 1, the particle size of Fe powder, Te powder and Se powder is 300-500 mesh, and the purity is greater than 99.9%; The single-phase FST superconducting powder obtained in step 2 above does not undergo any chemical reaction after planetary ball milling; The target hot pressing temperature in step 3 above is 500 o C~800 o C, pressure is 20-40 MPa, each hot pressing time is 1-10 h, and the final thickness of the target is 2 mm ~ 5 mm; The beneficial effects of the present invention are: a high-density FeSe 1-x Te x The method for preparing superconducting target material is to use low-temperature pretreated FST superconducting powder as raw material, prepare single-phase crystal by high-temperature self-solvent method, and then obtain high-density FST superconducting target material by low-temperature hot pressing sintering. This method solves the problems of uneven phase reaction, many residual impurities and low density in traditional methods, and significantly improves the critical current density of conventional FST superconductor target materials. J c This method is simple, suitable for the preparation of superconducting target materials, conducive to large-scale promotion and application, and has great commercial value. DETAILED DESCRIPTION

[0010] The present invention is described in detail below in conjunction with specific implementation modes. Example 1

[0011] Step 1: FST powder sintering Take Fe powder, Se powder and Te powder with a particle size of 300 mesh and a purity of 99.9%, and mix them according to the stoichiometric ratio of FeSe0.4 Te 0.6 Weigh and mix, seal the mixed powder in a vacuum quartz tube, and heat to 600 o C and keep warm for 36 h to obtain FST superconductor powder.

[0012] Step 2: Single-phase FST superconducting powder preparation The powders in step 1 were mixed for 5 min, and the mixed powders were sealed in a vacuum quartz tube again and heated at 980 o C sintering, after cooling, take 200g of FST superconductor powder according to the ball weight ratio of 10:1, and planetary mill for 10 hours under Ar atmosphere protection to obtain uniform single-phase FST superconductor powder; Step 3: Hot pressing FST superconducting target preparation The single-phase FST superconductor powder obtained in step 2 was placed in a graphite mold with an outer diameter of 20.0 mm for hot pressing and sintering at a hot pressing temperature of 600 o C, pressure of 20 MPa, holding time of 10 h. Then cooling in vacuum, a high-density FST superconducting target is obtained.

[0013] The crystal structure and composition tests of the obtained FST superconducting target showed that the crystallinity was very high, and the diffraction peak orientation was mainly along the c-axis. The SEM mapping test showed that its composition was uniform and there was a certain segregation of the Se component. Example 2

[0014] Step 1: FST powder sintering Take Fe powder, Se powder and Te powder with a particle size of 300 mesh and a purity of 99.9%, and mix them according to the stoichiometric ratio of FeSe 0.4 Te 0.6 Weigh and mix, seal the mixed powder in a vacuum quartz tube, and heat to 700 o C and keep warm for 36 h to obtain FST superconductor powder.

[0015] Step 2: Single-phase FST superconducting powder preparation The powders in step 1 were mixed for 5 min, and the mixed powders were sealed in a vacuum quartz tube again and heated at 985 o C sintering, after cooling, take 200g of FST superconductor powder according to the ball weight ratio of 10:1, and planetary mill for 10 hours under Ar atmosphere protection to obtain uniform single-phase FST superconductor powder; Step 3: Hot pressing FST superconducting target preparation The single-phase FST superconductor powder obtained in step 2 was placed in a graphite mold with an outer diameter of 20.0 mm for hot pressing and sintering at a hot pressing temperature of 600 oC, pressure of 20 MPa, holding time of 10 h. Then cooling in vacuum, a high-density FST superconducting target is obtained.

[0016] The crystal structure and composition tests of the obtained FST superconducting target showed that the crystallinity was very high, and the diffraction peak orientation was only along the a direction. The SEM mapping test showed that its composition was uniform and the Se content was seriously segregated. Example 3

[0017] Step 1: FST powder sintering Take Fe powder, Se powder and Te powder with a particle size of 300 mesh and a purity of 99.9%, and mix them according to the stoichiometric ratio of FeSe 0.4 Te 0.6 Weigh and mix, seal the mixed powder in a vacuum quartz tube, and heat to 750 o C and keep warm for 36 h to obtain PSMS superconductor powder.

[0018] Step 2: Single-phase FST superconducting powder preparation The powders in step 1 were mixed for 5 min, and the mixed powders were sealed in a vacuum quartz tube again for 1000 o C sintering, after cooling, take 200g of FST superconductor powder according to the ball weight ratio of 10:1, and planetary mill for 10 hours under Ar atmosphere protection to obtain uniform single-phase FST superconductor powder; Step 3: Hot pressing FST superconducting target preparation The single-phase FST superconductor powder obtained in step 2 was placed in a graphite mold with an outer diameter of 20.0 mm for hot pressing and sintering at a hot pressing temperature of 600 o C, pressure of 20 MPa, holding time of 10 h. Then cooling in vacuum, a high-density FST superconducting target is obtained.

[0019] The crystal structure and composition tests of the obtained FST superconducting target material showed that the crystallinity was very high and all the diffraction peaks were oriented along the c-axis, indicating that it had a high degree of preferential orientation. The SEM mapping test showed that its composition was uniform and the actual ratio was close to the nominal ratio. Example 4

[0020] Take Fe powder, Se powder and Te powder with a particle size of 300 mesh and a purity of 99.9%, and mix them according to the stoichiometric ratio of FeSe 0.4 Te 0.6 Weigh and mix, seal the mixed powder in a vacuum quartz tube, and heat to 800 o C and keep warm for 36 h to obtain PSMS superconductor powder.

[0021] Step 2: Single-phase FST superconducting powder preparation The powders in step 1 were mixed for 5 min, and the mixed powders were sealed in a vacuum quartz tube again for 1010 o C sintering, after cooling, take 200g of FST superconductor powder according to the ball weight ratio of 10:1, and planetary mill for 10 hours under Ar atmosphere protection to obtain uniform single-phase FST superconductor powder; Step 3: Hot pressing FST superconducting target preparation The single-phase FST superconductor powder obtained in step 2 was placed in a graphite mold with an outer diameter of 20.0 mm for hot pressing and sintering at a hot pressing temperature of 600 o C, pressure of 20 MPa, holding time of 10 h. Then cooling in vacuum, a high-density FST superconducting target is obtained.

[0022] The crystal structure and composition tests of the obtained FST superconducting target showed that the crystallinity was very high, the diffraction peak had c-axis orientation, and the SEM mapping test showed that its composition was uniform, and the Se / Te ratio had a certain segregation with the nominal ratio.

Claims

1. A high-density FeSe 1-x Te x A method for preparing a superconducting target material, characterized in that: It specifically includes the following steps: Step 1: FST powder sintering Fe, Se and Te powders were used as raw materials. 1-x Te x The powders with a stoichiometric ratio of x = 0.01 to 0.99 were weighed, mixed evenly, and sealed in a vacuum quartz tube and heated to 600 o C ~1100 o C, keep warm for 2 h~36 h to obtain FST superconductor precursor powder; Step 2: Single-phase FST superconducting powder preparation The FST superconductor precursor powder obtained in step 1 was mixed evenly for 5 min, sealed in a quartz tube again, and heated to 700 o C ~1100 o C. After cooling, the powder was subjected to planetary milling for 1 h to 10 h under Ar atmosphere protection at a ball-to-weight ratio of 10:1 to obtain uniform and unreacted FST superconductor powder; Step 3: Hot pressing FST superconducting target preparation The FST superconducting powder obtained in step 2 is loaded into a graphite film mold, and then subjected to low-temperature pretreatment and hot-pressing sintering to obtain a high-density FST superconducting target.

2. The method for preparing a high-density FST superconducting target material according to claim 1, characterized in that: In the step 1, the particle size of the Fe powder, Se powder and Te powder is 300-500 mesh, and the purity is greater than 99.9%.

3. The method for preparing a high-density FST superconducting target material according to claim 1, characterized in that: The single-phase FST superconducting powder obtained in step 2 is prepared by adopting a self-solvent method to obtain a single-phase single crystal bulk powder.

4. The method for preparing a high-density FST superconducting target material according to claim 1, characterized in that: The step 3 adopts a low-temperature hot pressing sintering method, which uses hot pressing to improve the density of the target material while maintaining a single phase, thereby improving the superconducting performance of the target material.