Preparation method of iron selenium tellurium superconducting target material

Abstract

The invention belongs to the technical field of preparation methods of iron-based superconducting materials, and provides a preparation method of an iron-selenium-tellurium superconducting material. The chemical formula of the iron-selenium-tellurium superconducting material is Fe < 1 + / -x > SeyTe1-y, x is greater than or equal to 0 and less than or equal to 0.2, and y is greater than 0 and less than or equal to 0.9. A discharge plasma sintering process is adopted, and the sintering time can be controlled within 1 hour, so that the sintering time is greatly shortened, and the preparation efficiency is remarkably improved; through high-voltage discharge, each part of the powder can be instantly and uniformly heated, so that the integral phase formation of the target material is uniform; in the sintering process, longitudinal high pressure is applied, the sintering temperature is reduced, the powder reaction rate is increased, the target density is remarkably improved, the target density is close to the theoretical density, and the mechanical performance is enhanced. The superconducting performance of the target material is effectively improved through the advantages.

Description

Technical Field

[0001] The invention belongs to the technical field of iron-based superconductor preparation, and in particular relates to a method for preparing an iron-selenium-tellurium superconducting material. Background Art

[0002] In February 2008, Professor H. Hosono's research group in Japan made a 1-x F x The discovery of superconductivity at 26K opened up a new field of research in iron-based superconductors. Iron-based superconductors were later divided into two categories: FeSe-based and FeAs-based. The superconducting layer of FeSe-based superconducting materials is composed of only -FeSe- layers, which is the simplest iron-based superconducting material known so far; while FeAs-based superconducting materials contain As elements, which limits their research and application. Compared with FeAs-based superconducting materials, FeSe-based superconducting materials have broader application prospects because they are safe and non-toxic during preparation and research.

[0003] Although the discovery of iron-based superconductors has been around for more than a decade, the preparation of high-performance FeSe-based superconducting targets is still difficult during the powder sintering process. The superconducting properties of FeSe-based superconducting targets are closely related to the ratio of elements before and after sintering, the target sintering process and other factors. Moreover, according to the phase diagram, the tetragonal phase with superconducting properties only appears in a very small element ratio and temperature range. Therefore, the preparation of FeSe-based superconducting targets with a high superconducting phase ratio is very difficult. Not only that, the conventional solid-phase sintering process often takes a long time, measured in days, and even post-processing requires more than ten days. The long sintering time and low preparation efficiency limit the subsequent sputtering use.

[0004] At present, the preparation of FeSe-based superconducting targets is mainly solid-phase sintering, or pressurizing the powder during sintering, that is, hot pressing. The time required for the aforementioned normal pressure sintering depends on the atomic migration rate, and it takes at least several days to sinter; although hot pressing effectively speeds up the reaction rate, it also takes more than ten hours. Since these two sintering processes are heated by hot coils and energy is transmitted through heat transfer, it is easy for the powder to be heated unevenly or the heating and cooling are delayed, affecting the phase formation. Therefore, it is necessary to explore new sintering processes that can not only shorten the sintering time and improve the preparation efficiency, but also make the target phase uniform, and can also increase the density of the target material and improve the utilization rate. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for quickly preparing high-performance FeSeTe superconducting target materials in view of the shortcomings of the above-mentioned sintering process, such as too long sintering time and uneven heating.

[0006] In order to solve the above technical problems, the present invention provides a method for preparing an iron-selenium-tellurium superconducting target material, wherein the chemical formula of the iron-selenium-tellurium superconducting material is Fe 1-x Se y Te 1-y or Fe 1+x Se y Te 1-y , wherein 0≤x≤0.2, 0<y≤0.9; comprising the following steps:

[0007] 1) Mix iron powder, selenium powder and tellurium powder evenly, put them into a quartz tube, evacuate and seal;

[0008] 2) sintering the quartz tube containing the mixed powder at a temperature of 500° C. to 700° C. for 30 to 60 hours, and then fully grinding it to obtain a precursor powder;

[0009] 3) placing the precursor powder in a graphite mold and keeping the surface flat;

[0010] 4) placing the mold horizontally on a sample table for spark plasma sintering, closing the door and evacuating the chamber;

[0011] 5) Control the longitudinal pressure, heating rate, sintering temperature, holding time and cooling time on the sintering platform program.

[0012] Preferably, in step 1), x may be 0, 0.05, 0.1, 0.15 or 0.2.

[0013] Preferably, in step 1), 0.4≤y≤0.6 or 0.4≤y≤0.5.

[0014] Preferably, in step 1), the vacuum is evacuated to a temperature not higher than 5×10 -4 Pa.

[0015] More preferably, the vacuum is evacuated to 1×10 -4 Pa, or 2×10 -4 Pa, 3×10 -4 Pa, 4×10 -4 Pa.

[0016] Preferably, in step 2), the temperature is 500-700°C.

[0017] More preferably, the temperature is 580°C to 620°C, and may be 580°C, 590°C, 600°C, 610°C or 620°C.

[0018] Preferably, in step 2), the sintering time is 30 to 60 hours.

[0019] More preferably, the sintering time is 35 h, 38 h, 40 h, 42 h or 45 h.

[0020] Preferably, in step 4), the vacuum is evacuated to a temperature not higher than 1×10 -4 Pa.

[0021] Preferably, in step 5), the longitudinal pressure is 25-50 MPa.

[0022] More preferably, in step 5), the longitudinal pressure is 40-50 MPa, or 25 MPa, 35 MPa, 40 MPa, 45 MPa, or 50 MPa.

[0023] Preferably, in step 5), the heating rate is 50°C / min to 100°C / min.

[0024] More preferably, in step 5), the heating rate is 80°C / min to 100°C / min, and may also be 60°C / min, 67°C / min, 80°C / min, or 100°C / min.

[0025] Preferably, in step 5), the sintering temperature is 500-700°C.

[0026] More preferably, in step 5), the sintering temperature may be 500°C, or 550°C, 580°C, 600°C, 650°C, or 700°C.

[0027] Preferably, in step 5), the insulation time is 5 to 15 minutes.

[0028] More preferably, in step 5), the insulation time can be 5 to 10 minutes, or can be 5 minutes, 7 minutes, 10 minutes, 12 minutes, or 15 minutes.

[0029] Preferably, in step 5), the cooling time is 6 to 10 minutes.

[0030] More preferably, in step 5), the cooling time is 8 to 10 minutes, or 8 minutes, 9 minutes, or 10 minutes.

[0031] The present invention adopts a discharge plasma sintering process. At the moment of discharge, each part of the powder generates heat evenly, so that the phase formation of each part of the target material is uniform, and the time required for heat generation is extremely short, which effectively reduces the preparation time; moreover, the sintering process continues to be longitudinally pressurized, the atomic migration rate is accelerated, the reaction rate is effectively increased, the sintering time is greatly reduced, and the density of the target material is significantly improved, and the mechanical properties of the target material are enhanced. The pressurization treatment of this process also reduces the reaction temperature. The sintering temperature is below 700°C, which avoids the gasification and enrichment of the Se element above the powder, so that it can fully react with each element. The preparation method of the present invention can significantly reduce the total sintering time to within 1 hour, which significantly improves the preparation efficiency of iron selenium telluride superconducting materials.

[0032] Preferably, step 1), step 2) and step 3) are all carried out in a protective atmosphere, and the protective atmosphere is one or both of nitrogen and an inert gas.

[0033] More preferably, the protective atmosphere is argon.

[0034] The technical solution of the present invention has the following beneficial effects:

[0035] 1. In this sintering method, a spark plasma sintering process is adopted, and the sintering time in this equipment can be controlled within 1 hour, which greatly shortens the sintering time and significantly improves the preparation efficiency.

[0036] 2. This preparation method can achieve instantaneous uniform heating of all parts of the powder through high-voltage discharge, making the overall phase of the target material uniform; during the sintering process, applying longitudinal high voltage not only reduces the sintering temperature and accelerates the powder reaction rate, but also significantly improves the density of the target material, making it close to the theoretical density and enhancing the mechanical properties. The above advantages effectively improve the superconducting performance of the target material. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The FeSe prepared in Example 2 of the present invention 0.4 Te 0.6 X-ray diffraction pattern of superconducting materials.

[0038] Figure 2 The FeSe prepared in Example 3 of the present invention 0.4 Te 0.6 X-ray diffraction pattern of superconducting materials.

[0039] Figure 3 The FeSe prepared in Example 6 of the present invention 0.4 Te 0.6 The resistance-temperature curve of a superconducting material. DETAILED DESCRIPTION

[0040] Before further describing the specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terms used in the examples of the present invention are intended to describe specific embodiments, rather than to limit the scope of protection of the present invention. The test methods in the following examples without specifying specific conditions are generally carried out under conventional conditions or under conditions recommended by the manufacturers.

[0041] When the embodiments give numerical ranges, it should be understood that, unless otherwise specified in the present invention, both endpoints of each numerical range and any numerical value between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those generally understood by those skilled in the art. In addition to the specific methods, equipment, and materials used in the embodiments, according to the grasp of the prior art by those skilled in the art and the record of the present invention, any methods, equipment, and materials of the prior art similar or equivalent to the methods, equipment, and materials described in the embodiments of the present invention can also be used to realize the present invention.

[0042] Example 1

[0043] In this embodiment, Fe 0.99 Se 0.4 Te 0.6 A specific example of a method for preparing a superconducting bulk material.

[0044] Step 1: In an argon-protected glove box, iron powder, selenium powder and tellurium powder were mixed in a molar ratio of 0.99:0.4:0.6 to obtain a mixed powder with a total mass of 4 g. 0.99 Se 0.4 Te 0.6 The powder was placed in a custom-made quartz tube with a reduced neck and a cylindrical quartz plug was used to clamp the reduced neck. Subsequently, the quartz tube was placed in a sealed bag protected by argon. The quartz tube was taken out and fixed on a tube sealing machine. The quartz tube was evacuated to 1×10 -4 Pa, stop evacuating the tube and use a hydrogen-oxygen torch to seal the quartz plug.

[0045] Step 2: Place the quartz tube containing the powder in a muffle furnace and sinter at 580°C for 45 hours.

[0046] Step 3: In an argon-protected glove box, break the quartz tube obtained in step 2, fully grind the obtained powder in a mortar to obtain a precursor powder, and evenly place the precursor powder into a graphite mold with an inner diameter of 1.6 cm to make the powder surface flat.

[0047] Step 4: Place the graphite mold described in step 3) horizontally on the sintering table of the spark plasma sintering equipment, lower the pressing rod to pre-press the powder, close the door and evacuate to no more than 0 Pa.

[0048] Step 5: On the sintering platform program, control the longitudinal pressure to 40 MPa, the heating rate to 80°C / min, the sintering temperature to 500°C, the holding time to 5 min, and the cooling time to 8 min.

[0049] The block target material prepared by the method of this embodiment has a dense and flawless appearance and a uniform phase after polishing.

[0050] Example 2

[0051] This embodiment is FeSe 0.4 Te 0.6 The first specific example of the preparation method of superconducting bulk material.

[0052] Step 1: In an argon-protected glove box, iron powder, selenium powder and tellurium powder were mixed in a molar ratio of 1:0.4:0.6 to obtain a mixed powder with a total mass of 4 g. The powder was FeSe 0.4 Te 0.6 The powder was placed in a custom-made quartz tube with a reduced neck and a cylindrical quartz plug was used to clamp the reduced neck. Subsequently, the quartz tube was placed in a sealed bag protected by argon. The quartz tube was taken out and fixed on a tube sealing machine. The quartz tube was evacuated to 1×10 -4 Pa, stop evacuating the tube and use a hydrogen-oxygen torch to seal the quartz plug.

[0053] Step 2: Place the quartz tube containing the powder in a muffle furnace and sinter at 600°C for 40 hours.

[0054] Step 3: In an argon-protected glove box, break the quartz tube obtained in step 2, fully grind the obtained powder in a mortar to obtain a precursor powder, and evenly place the precursor powder into a graphite mold with an inner diameter of 1.6 cm to make the powder surface flat.

[0055] Step 4: Place the graphite mold described in step 3) horizontally on the sintering table of the spark plasma sintering equipment, lower the pressing rod to pre-press the powder, close the door and evacuate to no more than 0 Pa.

[0056] Step 5: On the sintering platform program, control the longitudinal pressure to 50 MPa, the heating rate to 100°C / min, the sintering temperature to 500°C, the holding time to 10 min, and the cooling time to 8 min.

[0057] Figure 1 FeSe obtained by the preparation method of this embodiment 0.4 Te 0.6 X-ray diffraction spectrum of superconducting materials. It can be seen from the figure that FeSe was prepared under the conditions of longitudinal pressure of 50MPa, sintering temperature of 500℃ and holding time of 10min. 0.4Te 0.6 Superconducting materials greatly shorten the sintering time and significantly improve the preparation efficiency.

[0058] Example 3

[0059] This embodiment is FeSe 0.4 Te 0.6 A second specific example of a method for preparing a superconducting bulk material.

[0060] Step 1: In an argon-protected glove box, iron powder, selenium powder and tellurium powder were mixed in a molar ratio of 1:0.4:0.6 to obtain a mixed powder with a total mass of 4 g. The powder was FeSe 0.4 Te 0.6 The powder was placed in a custom-made quartz tube with a reduced neck and a cylindrical quartz plug was used to clamp the reduced neck. Subsequently, the quartz tube was placed in a sealed bag protected by argon. The quartz tube was taken out and fixed on a tube sealing machine. The quartz tube was evacuated to 2×10 -4 Pa, stop evacuating the tube and use a hydrogen-oxygen torch to seal the quartz plug.

[0061] Step 2: Place the quartz tube containing the powder in a muffle furnace and sinter at 600°C for 40 hours.

[0062] Step 3: In an argon-protected glove box, break the quartz tube obtained in step 2, fully grind the obtained powder in a mortar to obtain a precursor powder, and evenly place the precursor powder into a graphite mold with an inner diameter of 1.6 cm to make the powder surface flat.

[0063] Step 4: Place the graphite mold described in step 3) horizontally on the sintering table of the spark plasma sintering equipment, lower the pressing rod to pre-press the powder, close the door and evacuate to no more than 0 Pa.

[0064] Step 5: On the sintering platform program, control the longitudinal pressure to 50 MPa, the heating rate to 100°C / min, the sintering temperature to 700°C, the holding time to 15 min, and the cooling time to 8 min.

[0065] Figure 2 FeSe obtained by the preparation method of this embodiment 0.4 Te 0.6 X-ray diffraction spectrum of superconducting materials. It can be seen from the figure that FeSe was prepared in a short time under the conditions of longitudinal pressure of 50MPa, sintering temperature of 700℃ and holding time of 15min. 0.4 Te 0.6 Superconducting materials.

[0066] Example 4

[0067] This embodiment is FeSe 0.5 Te0.5 A specific example of a method for preparing a superconducting bulk material.

[0068] Step 1: In an argon-protected glove box, iron powder, selenium powder and tellurium powder were mixed in a molar ratio of 1:0.5:0.5 to obtain a mixed powder with a total mass of 4 g. The powder was FeSe 0.5 Te 0.5 The powder was placed in a custom-made quartz tube with a reduced neck and a cylindrical quartz plug was used to clamp the reduced neck. Subsequently, the quartz tube was placed in a sealed bag protected by argon. The quartz tube was taken out and fixed on a tube sealing machine. The quartz tube was evacuated to 2×10 -4 Pa, stop evacuating the tube and use a hydrogen-oxygen torch to seal the quartz plug.

[0069] Step 2: Place the quartz tube containing the powder in a muffle furnace and sinter at 610°C for 38 hours.

[0070] Step 3: In an argon-protected glove box, break the quartz tube obtained in step 2, fully grind the obtained powder in a mortar to obtain a precursor powder, and evenly place the precursor powder into a graphite mold with an inner diameter of 1.6 cm to make the powder surface flat.

[0071] Step 4: Place the graphite mold described in step 3) horizontally on the sintering table of the spark plasma sintering equipment, lower the pressing rod to pre-press the powder, close the door and evacuate to no more than 0 Pa.

[0072] Step 5: On the sintering platform program, control the longitudinal pressure to 45 MPa, the heating rate to 60°C / min, the sintering temperature to 600°C, the holding time to 7 min, and the cooling time to 10 min.

[0073] The block target material prepared by the method of this embodiment has a dense and flawless appearance and a uniform phase after polishing.

[0074] Example 5

[0075] This embodiment is FeSe 0.6 Te 0.4 A specific example of a method for preparing a superconducting bulk material.

[0076] Step 1: In an argon-protected glove box, iron powder, selenium powder and tellurium powder were mixed in a molar ratio of 1:0.6:0.4 to obtain a mixed powder with a total mass of 4 g. The powder was FeSe 0.6 Te 0.4 The powder was placed in a custom-made quartz tube with a reduced neck and a cylindrical quartz plug was used to clamp the reduced neck. Subsequently, the quartz tube was placed in a sealed bag protected by argon. The quartz tube was taken out and fixed on a tube sealing machine. The quartz tube was evacuated to 3×10 -4Pa, stop evacuating the tube and use a hydrogen-oxygen torch to seal the quartz plug.

[0077] Step 2: Place the quartz tube containing the powder in a muffle furnace and sinter at 620°C for 42 hours.

[0078] Step 3: In an argon-protected glove box, break the quartz tube obtained in step 2, fully grind the obtained powder in a mortar to obtain a precursor powder, and evenly put the precursor powder into a graphite mold with an inner diameter of 1.6 cm to make the powder surface flat;

[0079] Step 4: Place the graphite mold described in step 3) horizontally on the sintering table of the spark plasma sintering equipment, lower the pressing rod to pre-press the powder, close the door and evacuate to no more than 0 Pa.

[0080] Step 5: On the sintering platform program, control the longitudinal pressure to 35 MPa, the heating rate to 80°C / min, the sintering temperature to 550°C, the holding time to 12 min, and the cooling time to 9 min.

[0081] The block target material prepared by the method of this embodiment has a dense and flawless appearance and a uniform phase after polishing.

[0082] Example 6

[0083] This embodiment is FeSe 0.4 Te 0.6 A third specific example of the preparation method of superconducting bulk material.

[0084] Step 1: In an argon-protected glove box, iron powder, selenium powder and tellurium powder were mixed in a molar ratio of 1:0.4:0.6 to obtain a mixed powder with a total mass of 4 g. The powder was FeSe 0.4 Te 0.6 The powder was placed in a custom-made quartz tube with a reduced neck and a cylindrical quartz plug was used to clamp the reduced neck. Subsequently, the quartz tube was placed in a sealed bag protected by argon. The quartz tube was taken out and fixed on a tube sealing machine. The quartz tube was evacuated to 1×10 -4 Pa, stop evacuating the tube and use a hydrogen-oxygen torch to seal the quartz plug.

[0085] Step 2: Place the quartz tube containing the powder in a muffle furnace and sinter at 600°C for 40 hours.

[0086] Step 3: In an argon-protected glove box, break the quartz tube obtained in step 2, fully grind the obtained powder in a mortar to obtain a precursor powder, and evenly put the precursor powder into a graphite mold with an inner diameter of 1.6 cm to make the powder surface flat;

[0087] Step 4: Place the graphite mold described in step 3) horizontally on the sintering table of the spark plasma sintering equipment, lower the pressing rod to pre-press the powder, close the door and evacuate to no more than 0 Pa.

[0088] Step 5: On the sintering platform program, control the longitudinal pressure to 25 MPa, the heating rate to 100°C / min, the sintering temperature to 600°C, the holding time to 10 min, and the cooling time to 8 min.

[0089] Figure 3 FeSe obtained by the preparation method of this embodiment 0.4 Te 0.6 From the temperature-resistance curve of the superconducting material, it can be seen that the superconducting transition is obvious. The preparation method of the present invention greatly reduces the total sintering time and significantly improves the preparation efficiency.

[0090] Example 7

[0091] This embodiment is FeSe 0.4 Te 0.6 An example of a specific method for scaling up production of superconducting bulk materials.

[0092] Step 1: In an argon-protected glove box, iron powder, selenium powder and tellurium powder were mixed in a molar ratio of 1:0.4:0.6 to obtain a mixed powder with a total mass of 80 g. The powder was FeSe 0.4 Te 0.6 The powder was placed in a custom-made quartz tube with a reduced neck and a cylindrical quartz plug was used to clamp the reduced neck. Subsequently, the quartz tube was placed in a sealed bag protected by argon. The quartz tube was taken out and fixed on a tube sealing machine. The quartz tube was evacuated to a vacuum of no more than 3×10 -4 Pa, stop evacuating the tube and use a hydrogen-oxygen torch to seal the quartz plug.

[0093] Step 2: Place the quartz tube containing the powder in a muffle furnace and sinter at 600°C for 40 hours.

[0094] Step 3. In an argon-protected glove box, break the quartz tube obtained in step 2, grind the obtained powder in a mortar to obtain a precursor powder, and evenly place the precursor powder into a graphite mold with an inner diameter of 6.0 cm to make the powder surface flat; Step 4. Place the graphite mold described in step 3) horizontally on the sintering table of the spark plasma sintering equipment, lower the pressing rod to pre-press the powder, close the door and evacuate to no more than 0 Pa.

[0095] Step 5: On the sintering platform program, control the longitudinal pressure to 50 MPa, the heating rate to 67°C / min, the sintering temperature to 600°C, the holding time to 15 min, and the cooling time to 8 min.

[0096] The block target material prepared by the method of this embodiment has a dense and flawless appearance and a uniform phase after polishing. The preparation method of this patent can improve the preparation efficiency, increase the density of the target material, and improve the utilization rate. The above advantages effectively improve the superconducting performance of the target material.

Claims

1. A method for preparing an iron selenium tellurium superconducting material, characterized in that: The chemical formula of the iron selenium telluride superconducting material is Fe 1-x Se y Te 1-y or Fe 1+x Se y Te 1-y , wherein 0≤x≤0.2, 0<y≤0.9; comprising the following steps: 1) Mix iron powder, selenium powder and tellurium powder, put them into a quartz tube, evacuate and seal; 2) sintering the quartz tube containing the mixed powder at a temperature of 500° C. to 700° C. for 30 to 60 hours, and then grinding to obtain a precursor powder; 3) placing the precursor powder in a graphite mold and keeping the surface flat; 4) placing the mold horizontally on a spark plasma sintering platform, closing the door and evacuating the chamber; 5) Control the longitudinal pressure, heating rate, sintering temperature, holding time and cooling time on the sintering platform program.

2. The preparation method according to claim 1, characterized in that: In step 1), the vacuum is evacuated to ≤5×10 -4 Pa.

3. The preparation method according to claim 1, characterized in that: In step 2), the temperature is 500°C to 700°C. The preparation method according to claim 1 is characterized in that in step 2), the sintering time is 30 to 60 hours.

4. The preparation method according to claim 1, characterized in that: In step 4), the vacuum is evacuated to ≤0 Pa.

5. The preparation method according to claim 1, characterized in that: In step 5), the longitudinal pressure is 25-50 MPa.

6. The preparation method according to claim 1, characterized in that: In step 5), the heating rate is 50°C / min to 100°C / min.

7. The preparation method according to claim 1, characterized in that: In step 5), the sintering temperature is 500°C to 700°C.

8. The preparation method according to claim 1, characterized in that: In step 5), the insulation time is 5 to 15 minutes.

9. The preparation method according to claim 1, characterized in that: In step 5), the cooling time is 6 to 10 minutes.

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