A high-temperature superconducting raw material hafnium source and its preparation method and application

Abstract

The invention discloses a high-temperature superconducting raw material hafnium source and a preparation method and application thereof. The invention uses hafnium n-propoxide, 2,2,6,6-tetramethyl-3,5-heptanedione and tetrahydrofuran as raw materials, and generates tetra(2,2,6,6-tetramethyl-3,5-heptanedione) hafnium source by reacting hafnium ions with heptanedione (tmhd). In the process of synthesizing the hafnium source, "low temperature and slow speed" is adopted to control the adhesion of Hf(tmhd)4 source particles in the synthesis process, so as to obtain hafnium source crystal particles with small particles and narrow particle size distribution. The hafnium source can be used as a superconducting layer raw material with a yttrium source, a barium source and a copper source, and a YBCO film is prepared by MOCVD method, so that Hf ions are pinned in the YBCO film, and a high-temperature superconducting tape with high electrical properties under low temperature and strong magnetic field is obtained, and no agglomeration phenomenon occurs in the hafnium source during film preparation, and the deposition effect and thermal stability are good.

Description

Technical Field

[0001] The invention belongs to the technical field of superconducting materials, and in particular relates to a hafnium source, a raw material for high-temperature superconducting, and a preparation method and application thereof. Background Art

[0002] In 1987, MK Wu et al. discovered YBa 2 Cu 3 O 7-d (YBCO), T C Since then, high-temperature superconducting materials have shown great potential in the fields of electricity, magnetic fields, and supercomputing, relying on the three functions of "super-strong conductivity, complete anti-magnetism, and Josephson effect", which has attracted extensive research interest from scientists all over the world. 2 Cu 3 O 7-d This high-temperature superconducting thin film material has broad application prospects because it can achieve superconductivity in a relatively cheap liquid nitrogen environment.

[0003] Production of YBa 2 Cu 3 O 7-d The process routes of high temperature superconducting materials include PLD, MOD, MOCVD, RCE, etc. Among them, SuperPower Company produces YBa with IBAD+MOCVD process. 2 Cu 3 O 7-d Superconducting tape, the critical current of superconducting tape is higher at 77K and 0T, but the critical current advantage is not obvious at 30K and 3T.

[0004] In order to solve the above problems existing in the prior art, the present invention is provided. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a high-temperature superconducting raw material hafnium source and a preparation method and application thereof. The present invention uses hafnium ions to react with 2,2,6,6-tetramethyl-3,5-heptanedione (TMHD) to generate tetrakis(2,2,6,6-tetramethyl-3,5-heptanedione) hafnium source. The hafnium source can be used as a superconducting layer raw material with a yttrium source, a barium source and a copper source. MOCVD is used to prepare a YBCO film, so that Hf ions are pinned in the YBCO film, and a high-temperature superconducting tape with high electrical properties under low temperature and strong magnetic field is obtained.

[0006] The technical solution of the present invention is:

[0007] The present invention relates to a method for preparing a hafnium source as a high-temperature superconducting raw material, comprising the following steps:

[0008] S1, adding tetrahydrofuran and 2,2,6,6-tetramethyl-3,5-heptanedione into a reaction kettle and mixing, and exhausting the air in the kettle;

[0009] S2, turn on the stirring device, turn on the circulating heating device, and when the solution in the kettle reaches 75-80°C, slowly add hafnium n-propoxide to the kettle, keep the temperature at 75-80°C for 5-6 hours, stop stirring, turn off the circulating heating device, and naturally cool down to below 30°C;

[0010] S3, filtering the product obtained in step S2, and then adding the yellow liquid into a single-necked flask in batches, installing it on a rotary evaporation device, adjusting the lifter, allowing the single-necked flask to tilt in the water of a water bath, turning on the vacuum pump to draw negative pressure, turning on the condensation system, setting the temperature gradient, and when all the hafnium source semi-finished products in the flask are agglomerated, shutting down the rotary device and stopping the rotary evaporation;

[0011] S4. Take out the semi-finished hafnium source and dry it to obtain the product hafnium source Hf(tmhd) 4 .

[0012] Preferably, the volume ratio of tetrahydrofuran to hafnium n-propoxide is 15-16:3-3.5; the volume ratio of 2,2,6,6-tetramethyl-3,5-heptanedione to hafnium n-propoxide is 5.5-6.2:3-3.5.

[0013] Preferably, in step S13, the temperature gradient is: 2 hours at 40-45°C, 1.5 hours at 60-70°C, and 0.5 hours at 80-85°C.

[0014] The invention also relates to a high-temperature superconducting raw material hafnium source, which is prepared by the above-mentioned preparation method.

[0015] The present invention also relates to the application of the above-mentioned high-temperature superconducting raw material hafnium source in the preparation of superconducting thin films. After adding the hafnium source, Hf ions form pinning in the YBCO thin film, and the electrical properties are excellent especially at low temperature and strong magnetic field.

[0016] The present invention also relates to a method for preparing a superconducting film, wherein the hafnium source Hf(tmhd) is mixed according to the ratio of each metal element. 4 With Y (tmhd) 3 、Ba(tmhd) 2 、Cu(tmhd) 2Add tetrahydrofuran, stir evenly and filter, make superconducting film on MOCVD, silver plate and anneal. The invention uses tetra(2,2,6,6-tetramethyl-3,5-heptanedione)hafnium source, yttrium source, barium source and copper source as raw materials of superconducting layer, uses MOCVD method, mainly controls the flow rate of source liquid and oxygen partial pressure of reaction chamber, makes metal organic liquid phase sources such as Y, Ba, Cu, Hf realize continuous and stable gasification and liquid, makes metal organic matter react with oxygen in advance, prepares YBCO film by MOCVD, makes Hf ions form pinning in YBCO film, and obtains high-performance YBCO film.

[0017] Preferably, the molar ratio of each metal element is Hf:Y:Ba:Cu=0.05-0.08:1-1.2:1.52-1.62:1.60-1.65.

[0018] Preferably, in the method for preparing a superconducting thin film, the concentration of the mixed solution formed by adding each metal organic compound into tetrahydrofuran is 0.22-0.25 mol / L.

[0019] The beneficial effects of the present invention are:

[0020] (1) In the process of synthesizing the hafnium source, the present invention adopts "low temperature and slow speed" to control the Hf(tmhd) in the synthesis process. 4 The hafnium source particles are adhered to each other, thereby obtaining hafnium source crystal particles with small particles and narrow particle size distribution. The hafnium source has no agglomeration phenomenon during film making, and has good deposition effect and thermal stability.

[0021] (2) The 2,2,6,6-tetramethyl-3,5-heptanedione (tmhd) used in the present invention has large steric hindrance and strong chelating ability, and can form chelates with many metal ions with high volatility and thermal stability. The chelate Hf(tmhd) formed by the 2,2,6,6-tetramethyl-3,5-heptanedione and the Hf ions is 4 It not only has high volatility and thermal stability, but also has good compatibility and no pollution to the preparation of thin films; it accelerates the reaction, and the atoms (molecules) of the growing material form atomic clusters, which then continuously absorb new atoms to gradually grow into crystal nuclei, while generating effective (BHO) pinning centers of BaHfO, which further combine with each other to form a continuous BCO single crystal thin layer;

[0022] (3) The present invention introduces Hf ions into the YBCO film to generate Ba 2 HkDJ 4 A strong pinning effect is formed in the film, thereby obtaining a YBCO film with high electrical properties and excellent critical current performance, which can meet the needs of ultra-high field magnet applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0024] Figure 1 This is the dried tetrakis(2,2,6,6-tetramethyl-3,5-heptanedione)hafnium source image;

[0025] Figure 2 This is the thermogravimetric analysis diagram of the hafnium source sample. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0027] Example 1

[0028] Hafnium source Hf(tmhd) 4 Preparation:

[0029] S1, add 16L of THF (tetrahydrofuran) and 5500g of 2,2,6,6-tetramethyl-3,5-heptanedione into a reaction kettle and mix, and exhaust the air in the kettle through argon;

[0030] S2. Turn on the stirring device and the circulating heating device, adjust the temperature to 75°C, and when the solution in the kettle reaches 75°C, add 3000mL of hafnium n-propoxide (HfC 12 H 28 O 4 ) is slowly added into the kettle, kept at a constant temperature of 75°C for 5 hours, then stirring is stopped, the circulating heating device is turned off, and the temperature is naturally reduced to below 30°C;

[0031] S3, filter with K49 filter paper, then add the yellow liquid into a single-necked flask in batches, install it on the rotary evaporation equipment, adjust the lifter, let the single-necked flask tilt in the water of the water bath, turn on the vacuum pump to draw negative pressure, turn on the condensation system, set the temperature gradient from 40°C for 2 hours, 60°C for 1.5 hours, and 80°C for 0.5 hours. When the hafnium source semi-finished product in the flask is completely agglomerated, shut down the rotary equipment and stop the rotary evaporation;

[0032] S4. Move the block semi-finished product in the single-mouth flask into an enamel tray, and evenly distribute it in the enamel tray with a horn medicine spoon to a thickness of about 1mm. Then move the enamel tray containing the hafnium source semi-finished product into a small drying oven, set the temperature to 105℃, and keep the temperature constant for 4 hours; then turn off the power and cool it naturally. When the temperature in the oven is close to room temperature, take out the enamel tray and crush the source in the tray into powder with a plastic shovel to obtain the finished product. The dried tetra(2,2,6,6-tetramethyl-3,5-heptanedione) hafnium source is as follows Figure 1In addition, the thermogravimetric analysis of the hafnium source sample is shown in Figure 2 As shown, the weight loss steps analyzed by TGA thermogravimetric analyzer all reached a purity of more than 97.80%.

[0033] Preparation of superconducting film: Calculate the corresponding mass of hafnium source, yttrium source, barium source and copper source according to the molar ratio of Hf:Y:Ba:Cu=0.05:1:1.52:1.63, and then add Hf(tmhd) 4 (The corresponding molecular formula is HfC 44 H 76 O 8 , full name is tetrakis (2,2,6,6-tetramethyl-3,5-heptanedione) hafnium), Y (tmhd) 3 (YC 33 H 57 O 6 , full name is tris(2,2,6,6-tetramethyl-3,5-heptanedione)yttrium), Ba(tmhd) 2 (BaC 46 H 54 O 4 N 4 , full name is bis(2,2,6,6-tetramethyl-3,5-heptanedione)barium·bis(1,10-phenanthroline)), Cu(tmhd) 2 (CuC 22 H 38 O 4 , full name is di(2,2,6,6-tetramethyl-3,5-heptanedione)copper) was added to tetrahydrofuran to prepare a mixed solution with a concentration of 0.22 mol / L. After stirring and filtering, a superconducting thin film was made on MOCVD. After silver plating and annealing, the test results were as follows: film thickness 2.352μm, Ic(77K, 0T)732A / 12㎜, Ic(30K, 3T)2049A / 12㎜.

[0034] Example 2

[0035] The hafnium source, yttrium source, barium source and copper source in Example 1 were used.

[0036] According to the molar ratio of Hf:Y:Ba:Cu=0.07:1:1.52:1.63, the corresponding masses of hafnium source, yttrium source, barium source and copper source are calculated, and then Hf(tmhd) 4 、Y(tmhd) 3 、Ba(tmhd) 2 、Cu(tmhd) 2Add tetrahydrofuran to prepare a mixed solution with a concentration of 0.22 mol / L. After stirring and filtering, a superconducting thin film was made on MOCVD. After silver plating and annealing, the test results are as follows: film thickness 2.36μm, Ic (77K, 0T) 765.10A / 12㎜, Ic (30K, 3T) 2517.2A / 12㎜.

[0037] Example 3

[0038] The hafnium source, yttrium source, barium source and copper source in Example 1 were used.

[0039] According to the molar ratio of Hf:Y:Ba:Cu=0.08:1:1.52:1.63, the corresponding masses of hafnium source, yttrium source, barium source and copper source are calculated, and then Hf(tmhd) 4 、Y(tmhd) 3 、Ba(tmhd) 2 、Cu(tmhd) 2 Add tetrahydrofuran to prepare a mixed solution with a concentration of 0.22 mol / L, stir evenly and filter, then make a superconducting thin film on MOCVD. After silver plating and annealing, the test results are as follows: film thickness 2.361μm, Ic (77K, 0T) 710A / 12㎜, Ic (30K, 3T) 2130A / 12㎜.

[0040] Comparative Example 1

[0041] The yttrium source, barium source and copper source in Example 1 were used.

[0042] According to the molar ratio of Y:Ba:Cu=1:1.52:1.63, the corresponding masses of yttrium source, barium source and copper source are calculated, and then Y(tmhd) 3 、Ba(tmhd) 2 、Cu(tmhd) 2 Add tetrahydrofuran to prepare a mixture with a concentration of 0.22 mol / L, stir evenly, filter, and then do YBa on MOCVD 2 Cu 3 O 7-d The test results of the superconducting film after silver plating and annealing are as follows: (film thickness 2.35μm), Ic (77K, 0T) 720A / 12㎜, Ic (30K, 3T) 1800A / 12㎜.

[0043] From the above results, it can be seen that if the hafnium source is not added, the electrical properties of the superconducting tape will change under low temperature and strong magnetic field. After adding the hafnium source, Hf ions form pinning in the YBCO film, and the electrical properties are excellent especially under low temperature and strong magnetic field.

[0044] It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all changes and modifications that fall within the scope and boundaries of the appended claims, or the equivalent forms of such scope and boundaries.

Claims

1. A method for preparing a superconducting thin film, characterized in that: According to the ratio of each metal element, hafnium source Hf(tmhd)4, Y(tmhd)3, Ba(tmhd)2, Cu(tmhd)2 are added to tetrahydrofuran, stirred evenly and filtered, and then a superconducting film is made on MOCVD, and silver-plated and annealed; wherein the molar ratio of each metal element is Hf:Y:Ba:Cu=0.05~0.08: 1~1.2:1.52~1.62:1.60~1.65; The preparation method of the hafnium source comprises the following steps: S1, adding tetrahydrofuran and 2,2,6,6-tetramethyl-3,5-heptanedione into a reaction kettle and mixing, and exhausting the air in the kettle; S2. Turn on the stirring device and the circulating heating device. When the solution in the kettle reaches 75-80°C, slowly add hafnium n-propoxide to the kettle. Keep the temperature at 75-80°C for 5-6 hours. Stop stirring, turn off the circulating heating device, and cool naturally to below 30°C. S3, filtering the product obtained in step S2, and then adding the yellow liquid into a single-necked flask in batches, installing it on a rotary evaporation device, adjusting the lifter, allowing the single-necked flask to tilt in the water of a water bath, turning on the vacuum pump to draw negative pressure, turning on the condensation system, setting the temperature gradient, and when all the hafnium source semi-finished products in the flask are agglomerated, shutting down the rotary device and stopping the rotary evaporation; S4, taking out the semi-finished hafnium source and drying it to obtain the product hafnium source Hf(tmhd)4.

2. The method for preparing a superconducting thin film according to claim 1, characterized in that: In the method for preparing a superconducting thin film, the concentration of the mixed solution formed by adding each metal organic compound into tetrahydrofuran is 0.22-0.25 mol / L.

3. The method for preparing a superconducting thin film according to claim 1, characterized in that: The volume ratio of tetrahydrofuran to hafnium n-propoxide is 15-16:3-3.5; the volume ratio of 2,2,6,6-tetramethyl-3,5-heptanedione to hafnium n-propoxide is 5.5-6.2:3-3.

5.

4. The method for preparing a superconducting thin film according to claim 1, characterized in that: In step S3, the temperature gradient is: 2 hours at 40-45°C, 1.5 hours at 60-70°C, and 0.5 hours at 80-85°C.

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