A large-size Cu1234 superconducting bulk material and preparation method thereof

Abstract

The present invention relates to a large-size Cu1234 superconducting bulk material and a preparation method thereof, belonging to the technical field of superconducting materials, and solving the problem that the method of the prior art prepares the Cu1234 superconducting material in a small size, which limits the application of the Cu1234 superconducting material. The method of the present invention adopts pre-pressing molding technology to improve the density of the precursor, prevent the large-size sample from shrinking violently during the high-pressure and high-temperature synthesis process, and cause the sample size to be reduced; adopts secondary sealing technology to seal the pre-pressed precursor to prevent the loss of oxygen during the high-pressure and high-temperature synthesis; adding an insulation layer reduces the temperature gradient, effectively ensures the stability of the temperature during synthesis, and ensures that the sample has excellent superconducting performance. An industrial-grade six-sided top press is used as a device for high-pressure and high-temperature synthesis, providing a cavity size space of up to 4-5 cm, significantly increasing the sample space in the high-pressure and high-temperature test, and ensuring the preparation of centimeter-level Cu1234 superconductors.

Description

Technical Field

[0001] The present invention relates to the technical field of superconducting materials, and in particular to a large-size Cu1234 superconducting bulk material and a preparation method thereof. Background Art

[0002] Superconducting materials have both zero resistance and complete anti-magnetism, and they have shown broad and far-reaching application prospects in the fields of energy, transportation, medical treatment, power transmission, aerospace, etc. In the more than 100 years since the discovery of the superconductivity phenomenon, people have continuously explored and discovered new superconducting materials, such as single element superconductors, alloy superconductors, heavy fermion superconductors, copper-based superconductors, iron-based superconductors, hydrogen-rich compound superconductors, etc. Among them, Müller and Bednorz et al. first discovered the La-Ba-Cu-O superconducting material with a superconducting transition temperature of about 35K in 1986, which opened the era of copper oxide superconductivity research. In 1987, the teams of Zhu Jingwu and Zhao Zhongxian and others independently discovered the "yttrium series" Y-Ba-Cu-O superconducting system with a superconducting transition temperature of about 90K. This was the first time in the world that a superconducting material exceeding the liquid nitrogen temperature range (77K) was discovered. Subsequently, several series of copper-based superconducting materials were discovered, including "bismuth series", "thallium series", "mercury series", "copper series", etc. At present, the copper-based superconducting material with the highest superconducting transition temperature is recognized as the "mercury series" (Hg-Ba-Ca-Cu-O) superconductor, which can reach 135K under normal pressure. After more than 30 years of development, the research on high-temperature superconductivity of copper oxides has achieved remarkable results in mechanism exploration and practical application. Copper-based superconductors are currently the only superconducting materials that have broken through the liquid nitrogen temperature zone under normal pressure conditions, and have great practical value.

[0003] Among copper-based superconducting materials, although the "thallium series" and "mercury series" have higher critical transition temperatures, they are not conducive to material preparation and practical application because they contain volatile and toxic elements. At present, only two types of copper-based superconducting materials, "yttrium series" and "bismuth series", have achieved preliminary applications. However, the critical current density of "bismuth series" copper-based superconducting materials decreases sharply with increasing temperature, and is only suitable for low-temperature and high-field environments; the critical current density of "yttrium series" copper-based superconducting materials decreases slowly with increasing temperature, which is better than "bismuth series" copper-based superconducting materials and is the first choice for application in high-temperature and high-field environments. However, the superconducting transition temperature of "yttrium series" copper-based superconducting materials is only 93K, which is only 16K higher than the liquid nitrogen temperature zone (77K), and is much lower than the critical transition temperature of "bismuth series", "thallium series" and "mercury series" superconducting materials. In addition, "yttrium series" copper-based superconducting materials contain rare earth metal yttrium, and the high manufacturing cost also limits its practical application to a certain extent. Therefore, there is an urgent need for practical applications to develop copper-based superconducting materials that have simple components, are environmentally friendly, low cost, stable properties, and have both high superconducting transition temperature and high critical current density.

[0004] The "copper series" is an important member of the copper-based superconductor family. The chemical formula of the copper-based superconductor is Cuba2Ca n-1 Cu n O 2n+2+δ According to the naming rules of copper-based superconductors, it is abbreviated as Cu12(n-1)n: "Cu" is the characteristic heavy metal element contained in the charge reservoir, "1" represents the number of characteristic heavy metal layers, "2" represents the number of charge reservoir layers adjacent to the [CuO2] surface, "n" represents the number of [CuO2] conductive plane layers contained in the unit cell, and "(n-1)" represents the number of isolation layers between [CuO2] conductive planes. "Copper-based" superconductors can form CuBa2Ca1Cu2O depending on the number of [CuO2] planes contained in the unit cell. 6+δ (Cu1212),CuBa2Ca2Cu3O 8+δ (Cu1223),CuBa2Ca3Cu4O 10+δ (Cu1234) and other series of structural components. In the "copper series" superconductor family, Cu1234 is not only easy to prepare, but also has the best superconducting properties.

[0005] Cu1234 superconductors cannot be prepared by solid-phase sintering under normal pressure conditions, but can only be prepared by high-temperature and high-pressure synthesis. In the prior art, the research on Cu1234 superconducting materials is mainly based on laboratory miniaturization research. Due to the limitation of the cavity size of the laboratory small-scale high-temperature and high-pressure synthesis device, the diameter and height of the high-temperature superconducting block of Cu1234 superconducting material synthesized in a single batch are only 2-3 mm. The small size greatly limits the practical application of Cu1234 superconductors. Since Cu1234 superconductors require high-pressure synthesis, in the process of amplification and preparation, it is not a simple size enlargement, but also a series of problems such as the excessive volume shrinkage of large-size samples under high pressure, the sealing of samples, and the uniformity of samples need to be solved. At present, there is no relevant research and report on the preparation of centimeter-level Cu1234 superconducting materials. Summary of the invention

[0006] In view of the above analysis, the purpose of the present invention is to provide a large-sized Cu1234 superconducting bulk material and a preparation method thereof, so as to solve the problem that the Cu1234 superconducting material prepared by the prior art method is small in size, which limits the application of the Cu1234 superconducting material.

[0007] In a first aspect, the present invention provides a method for preparing a large-size Cu1234 superconducting bulk material, comprising the following steps:

[0008] (1) mixing, grinding and synthesizing BaO2 powder and CuO powder to obtain BaCuO2 compound powder;

[0009] (2) mixing, grinding and synthesizing CaO powder and CuO powder to obtain Ca2CuO3 compound powder;

[0010] (3) mixing the BaCuO2 compound powder, the Ca2CuO3 compound powder, CaO powder, CuO powder and BaO2 powder to obtain a superconducting phase starting reaction mixture;

[0011] (4) pressing the superconducting phase starting reaction mixture into a cylindrical shape to obtain a cylindrical sample;

[0012] (5) Wrapping the cylindrical sample with gold foil to achieve primary sealing, and placing it in a container made of metal molybdenum to achieve secondary sealing to obtain a sealed sample;

[0013] (6) Arranging a thermal insulation layer around the sealed sample to obtain a high-pressure assembly block;

[0014] (7) Placing the high-pressure assembly block in an industrial-grade six-sided top press to perform a high-pressure and high-temperature synthesis reaction to obtain the large-sized Cu1234 superconducting bulk material.

[0015] Furthermore, in step (1), the molar ratio of BaO2 powder to CuO powder is 1:1, the synthesis temperature is 300-1200°C, and the synthesis time is 1-80h.

[0016] Furthermore, in step (1), the heating rate of the synthesis is 0.1-100°C / min.

[0017] Furthermore, in step (2), the molar ratio of CaO powder to CuO powder is 2:1, the synthesis temperature is 300-1200° C., and the synthesis time is 1-80 h.

[0018] Furthermore, in step (2), the heating rate of the synthesis is 0.1-100°C / min.

[0019] Furthermore, in step (3), the molar ratio of BaCuO2 compound powder, Ca2CuO3 compound powder, CaO powder, CuO powder and BaO2 powder is 2:1:1:2:δ, wherein δ is 0-1.

[0020] Furthermore, in step (4), the superconducting phase starting reaction mixture is pressed into a cylindrical shape at a pressure of 10-15 MPa, wherein the diameter of the cylinder is 0.1-2 cm and the height is 0.1-2 cm.

[0021] Furthermore, in step (6), the insulation layer is made of dolomite and zirconia.

[0022] Further, in step (7), the synthesis pressure is 2-10 GPa, for example, 2 GPa, 3 GPa, 4 GPa, 5 GPa, 6 GPa, 7 GPa, 8 GPa, 9 GPa, 10 GPa, the temperature is 800-1400°C, for example, 800°C, 900°C, 1000°C, 1100°C, 1200°C, 1300°C, 1400°C, and the synthesis time is 0.1-5h, for example, 0.1h, 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h.

[0023] In a second aspect, the present invention provides a large-size Cu1234 superconducting bulk material prepared by the method, wherein the chemical formula of the Cu1234 superconducting bulk material is CuBa2Ca3Cu4O 10+2δ , the diameter of the Cu1234 superconducting bulk material is 0.1-2cm and the height is 0.1-2cm.

[0024] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0025] (1) The method of the present invention adopts pre-pressing technology to improve the density of the precursor and prevent large-sized samples from shrinking drastically during high-pressure and high-temperature synthesis, which causes the sample size to shrink; adopts secondary sealing technology to seal the pre-pressed precursor to prevent the loss of oxygen during high-pressure and high-temperature synthesis; adding an insulation layer reduces the temperature gradient, effectively ensuring the temperature stability during synthesis, and ensuring that the sample has excellent superconducting properties. An industrial-grade six-sided top press is used as a high-pressure and high-temperature synthesis device, providing a cavity size space of up to 4-5 cm, significantly increasing the sample space in high-pressure and high-temperature tests, and ensuring the preparation of centimeter-level Cu1234 superconductors;

[0026] (2) Compared with the traditional laboratory synthesis process, the method of the present invention can effectively increase the macroscopic size of the superconducting block while maintaining relatively high superconducting performance parameters; the method is simple and feasible, has low manufacturing cost, does not contain toxic elements, has simple components and is environmentally friendly, and is suitable for large-scale industrial production.

[0027] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0029] Figure 1 This is a physical picture of a cylindrical sample prepared in Example 1 of the present invention;

[0030] Figure 2 A schematic diagram of a high-voltage assembly block prepared in Example 1 of the present invention;

[0031] Figure 3 This is a physical picture of the large-sized Cu1234 superconducting bulk material prepared in Example 1 of the present invention;

[0032] Figure 4 This is an X-ray diffraction pattern of a large-sized Cu1234 superconducting bulk material prepared in Example 1 of the present invention;

[0033] Figure 5 This is a crystal structure diagram of a large-sized Cu1234 superconducting bulk material prepared in Example 1 of the present invention;

[0034] Figure 6 The resistance diagram of the large-sized Cu1234 superconducting bulk material prepared in Example 1 of the present invention;

[0035] Figure 7 This is an information diagram of the transition temperature, diamagnetism and superconducting volume fraction of a large-sized Cu1234 superconducting bulk material prepared in Example 1 of the present invention;

[0036] Figure 8 This is an information diagram of the transition temperature, diamagnetism and superconducting volume fraction of the Cu1234 superconducting bulk material prepared in Comparative Example 1 of the present invention;

[0037] Fig. 9 Information diagram of transition temperature, diamagnetism and superconducting volume fraction of Cu1234 superconducting bulk material prepared in Comparative Example 2 of the present invention;

[0038] Fig.10 Information diagram of transition temperature, diamagnetism and superconducting volume fraction of Cu1234 superconducting bulk material prepared in Comparative Example 3 of the present invention;

[0039] Fig.11 Information diagram of transition temperature, diamagnetism and superconducting volume fraction of the Cu1234 superconducting bulk material prepared in Comparative Example 4 of the present invention. DETAILED DESCRIPTION

[0040] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0041] A specific embodiment of the present invention discloses a method for preparing a large-size Cu1234 superconducting bulk material, comprising the following steps:

[0042] (1) mixing, grinding and synthesizing BaO2 powder and CuO powder to obtain BaCuO2 compound powder;

[0043] (2) mixing, grinding and synthesizing CaO powder and CuO powder to obtain Ca2CuO3 compound powder;

[0044] (3) mixing the BaCuO2 compound powder, the Ca2CuO3 compound powder, CaO powder, CuO powder and BaO2 powder to obtain a superconducting phase starting reaction mixture;

[0045] (4) pressing the superconducting phase starting reaction mixture into a cylindrical shape to obtain a cylindrical sample;

[0046] (5) Wrapping the cylindrical sample with gold foil to achieve primary sealing, and placing it in a container made of metal molybdenum to achieve secondary sealing to obtain a sealed sample;

[0047] (6) Arranging a thermal insulation layer around the sealed sample to obtain a high-pressure assembly block;

[0048] (7) Placing the high-pressure assembly block in an industrial-grade six-sided top press to perform a high-pressure and high-temperature synthesis reaction to obtain the large-sized Cu1234 superconducting bulk material.

[0049] In the prior art, the research on Cu1234 superconducting materials is mainly based on laboratory research. At present, the commonly used miniaturized high-temperature and high-pressure synthesis devices in the laboratory include the DIA-type cubic hexahedron high-pressure device and the Walker-type 6-8 two-stage propulsion press. These high-temperature and high-pressure synthesis devices can achieve high-temperature and high-pressure conditions of 50,000 to 200,000 atmospheres and 2000°C, which meet the preparation conditions of Cu1234 superconducting materials. However, the sample cavities of these high-temperature and high-pressure synthesis devices in the laboratory are relatively small, generally only 2-3 mm. Due to the limitation of the cavity size of the laboratory high-temperature and high-pressure synthesis device, the diameter and height of the high-temperature superconducting blocks of Cu1234 superconducting materials synthesized in a single batch are only in the order of millimeters. The small size not only limits the research on the performance of Cu1234 superconducting materials, but also greatly limits the promotion of the practical application of Cu1234 superconductors. The defect of insufficient preparation capacity of single-batch Cu1234 superconducting materials urgently needs to be improved and broken through.

[0050] The mainstream high-temperature and high-pressure synthesis device currently used in industrial production is a hinged six-sided top press, whose pressure and temperature can reach 50,000-60,000 atmospheres and 2000°C, and the sample cavity size can reach a maximum diameter of 4-5 cm and a maximum height of 3-4 cm. Therefore, the single-batch sample preparation capacity of an industrial-grade high-temperature and high-pressure synthesis device is dozens to hundreds of times that of a laboratory device. The present invention improves the synthesis process, designs and develops a synthesis assembly to achieve ultra-high oxygen pressure, and uses an industrial-grade high-temperature and high-pressure synthesis device to prepare centimeter-scale Cu1234 superconducting materials for the first time.

[0051] Compared with the prior art, the method of the present invention adopts pre-pressing molding technology, which can not only make it molded, but also improve the density of the precursor, prevent large-sized samples from shrinking too much during high-pressure and high-temperature synthesis, causing the sample size to shrink, resulting in a smaller synthesized sample size; adopt secondary sealing technology to seal the pre-pressed precursor to prevent the loss of oxygen during high-pressure and high-temperature synthesis, and ensure that the sample has excellent superconducting properties; adding an insulation layer reduces the temperature gradient, effectively ensuring the stability and uniformity of the temperature during synthesis, and ensuring that the sample has excellent superconducting properties. An industrial-grade six-sided top press is used as a high-pressure and high-temperature synthesis device, providing a cavity size space of up to 4-5 cm, significantly increasing the sample space in high-pressure and high-temperature tests, and ensuring the preparation of centimeter-level Cu1234 superconductors.

[0052] Compared with the traditional laboratory synthesis process, the method of the present invention can effectively increase the macroscopic size of the superconducting bulk material while maintaining relatively high superconducting performance parameters. The method is simple and feasible, has low manufacturing cost, does not contain toxic elements, has simple components and is environmentally friendly, and is suitable for large-scale industrial production.

[0053] It should be noted that the industrial-grade six-sided top press described in the present invention adopts the structure in the prior art.

[0054] In a specific embodiment, in step (1), the molar ratio of BaO2 powder to CuO powder is 1:1, the synthesis temperature is 300-1200°C, and the synthesis time is 1-80h.

[0055] In a preferred embodiment, in step (1), the synthesis temperature is 600-900° C. and the synthesis time is 20-28 h.

[0056] Exemplarily, in step (1), the synthesis temperature is 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, and the synthesis time is 1h, 4h, 8h, 12h, 16h, 20h, 24h, 28h, 32h, 36h, 40h, 44h, 48h, 52h, 56h, 60h, 64h, 68h, 72h, 76h, 80h.

[0057] In a specific embodiment, in step (1), the heating rate of synthesis is 0.1-100°C / min, and exemplary, the heating rate is 1°C / min, 5°C / min, 10°C / min, 15°C / min, 20°C / min, 25°C / min, 30°C / min, 35°C / min, 40°C / min, 45°C / min, 50°C / min, 55°C / min, 60°C / min, 65°C / min, 70°C / min, 75°C / min, 80°C / min, 85°C / min, 90°C / min, 95°C / min, 100°C / min. Preferably, the heating rate is 2-6°C / min.

[0058] In a specific embodiment, in step (2), the molar ratio of CaO powder to CuO powder is 2:1, the synthesis temperature is 300-1200° C., and the synthesis time is 1-80 h.

[0059] In a preferred embodiment, in step (2), the synthesis temperature is 900-1100° C. and the synthesis time is 20-28 h.

[0060] Exemplarily, in step (2), the synthesis temperature is 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, and the synthesis time is 1h, 4h, 8h, 12h, 16h, 20h, 24h, 28h, 32h, 36h, 40h, 44h, 48h, 52h, 56h, 60h, 64h, 68h, 72h, 76h, 80h.

[0061] In a specific embodiment, in step (2), the heating rate of synthesis is 0.1-100°C / min, and exemplary, the heating rate is 1°C / min, 5°C / min, 10°C / min, 15°C / min, 20°C / min, 25°C / min, 30°C / min, 35°C / min, 40°C / min, 45°C / min, 50°C / min, 55°C / min, 60°C / min, 65°C / min, 70°C / min, 75°C / min, 80°C / min, 85°C / min, 90°C / min, 95°C / min, 100°C / min. Preferably, the heating rate is 2-6°C / min.

[0062] In a specific embodiment, in step (3), the molar ratio of BaCuO2 compound powder, Ca2CuO3 compound powder, CaO powder, CuO powder and BaO2 powder is 2:1:1:2:δ, wherein δ is 0-1.

[0063] In a specific embodiment, in step (4), the superconducting phase starting reaction mixture is pressed into a cylindrical shape at a pressure of 10-15 MPa, and the diameter of the cylinder is 0.1-2 cm and the height is 0.1-2 cm.

[0064] In a specific embodiment, in step (6), the insulation layer is made of dolomite and zirconia.

[0065] It should be noted that in step (6), a zirconia insulation layer and a dolomite insulation layer are sequentially arranged around the sealed sample. The thickness of the dolomite insulation layer is 1-2 mm, and the thickness of the zirconia insulation layer is 1-2 mm.

[0066] In a specific embodiment, in step (7), the synthesis pressure is 2-10 GPa, exemplarily, the synthesis pressure is 2 GPa, 3 GPa, 4 GPa, 5 GPa, 6 GPa, 7 GPa, 8 GPa, 9 GPa, 10 GPa, the temperature is 800-1400°C, exemplarily, the temperature is 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, 1250°C, 1300°C, 1350°C, 1400°C, and the synthesis time is 0.1-5h, exemplarily, the synthesis time is 0.1h, 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h.

[0067] Another specific embodiment of the present invention discloses a large-sized Cu1234 superconducting bulk material prepared by the method, wherein the chemical formula of the Cu1234 superconducting bulk material is CuBa2Ca3Cu4O 10+2δ, the diameter of the Cu1234 superconducting bulk material is 0.1-2cm and the height is 0.1-2cm.

[0068] The Cu1234 superconducting bulk material prepared by the method of the present invention contains only copper (Cu), oxygen (O) and two alkaline earth (Ca, Ba) elements, does not contain toxic, volatile, precious metals and other elements, has simple components, is environmentally friendly and low cost. The method of the present invention is based on an industrial-grade high-pressure and high-temperature synthesis device and a synthesis method thereof, has a simple process and a high yield. After being prepared by an industrial-grade high-temperature and high-pressure synthesis device, the Cu1234 superconducting material can be recovered under normal pressure conditions, and can maintain long-term stability of superconducting performance in an air environment, and is suitable for large-scale industrial production and practical applications.

[0069] The technical solution of the present invention is further explained below in conjunction with specific embodiments. The raw materials used in the present invention are all of high purity.

[0070] Example 1

[0071] A method for preparing a large-size Cu1234 superconducting bulk material comprises the following steps:

[0072] (1) In an inert gas argon atmosphere glove box, high-purity BaO2 powder and high-purity CuO powder were mixed in a molar ratio of 1:1, fully ground and poured into a corundum crucible, placed in a tube furnace, and oxygen was introduced, and the temperature was increased from room temperature to 750°C at a heating rate of 4°C / min, and synthesized at 750°C for 24 hours. After synthesis, the mixture was taken out and transferred into a glove box, and the synthesized block was ground into powder to obtain BaCuO2 compound powder;

[0073] (2) in an inert gas argon atmosphere glove box, high-purity CaO powder and high-purity CuO powder were mixed in a molar ratio of 2:1, fully ground and poured into a corundum crucible, placed in a tube furnace, introduced with oxygen, and heated from room temperature to 1000° C. at a heating rate of 4° C. / min, synthesized at 1000° C. for 24 h, and after synthesis, taken out and transferred into a glove box, and the synthesized block was ground into powder to obtain Ca2CuO3 compound powder;

[0074] (3) in an inert gas argon atmosphere glove box, the BaCuO2 compound powder, the Ca2CuO3 compound powder, high-purity CaO powder, high-purity CuO powder and high-purity BaO2 powder are mixed in a molar ratio of 2:1:1:2:1 to obtain a superconducting phase starting reaction mixture;

[0075] (4) Using a tablet press at a pressure of 10 MPa, the superconducting phase starting reaction mixture is pressed into a dense cylindrical shape with a diameter of 1.5 cm and a height of 1.5 cm to obtain a cylindrical sample, such as Figure 1 As shown;

[0076] (5) Wrapping the cylindrical sample with gold foil to achieve primary sealing, and placing it in a container made of metal molybdenum to achieve secondary sealing to obtain a sealed sample;

[0077] (6) A zirconia insulation layer and a dolomite insulation layer are sequentially arranged around the sealed sample, wherein the thickness of the dolomite insulation layer is 1 mm and the thickness of the zirconia insulation layer is 1 mm, to obtain a high-pressure assembly block, such as Figure 2 As shown;

[0078] (7) Placing the high-pressure assembly block in an industrial-grade six-sided top press to perform a high-pressure and high-temperature synthesis reaction at a synthesis pressure of 5 GPa, a temperature of 1000° C., and a synthesis time of 0.5 h to obtain the large-sized Cu1234 superconducting bulk material.

[0079] The large-sized Cu1234 superconducting bulk material prepared in this embodiment is as follows Figure 3 As shown, the chemical formula is CuBa2Ca3Cu4O 12.0 The large-size Cu1234 superconducting bulk material prepared in this embodiment has a diameter of 1.2 cm and a height of 1.2 cm.

[0080] The large-sized Cu1234 superconducting bulk material prepared in this embodiment was ground into powder and tested for X-ray diffraction. The X-ray diffraction pattern was as follows: Figure 4 The crystal structure of the sample is obtained as shown. Figure 5 The obtained unit cell parameters and atomic position information are shown in Table 1.

[0081] The resistance of the large-size Cu1234 superconducting bulk material prepared in this embodiment was tested to obtain the superconducting transition temperature information of the sample. Figure 6 As shown. Since the superconducting transition temperature is an important parameter to characterize superconducting materials, when the temperature is lower than the superconducting transition temperature, the superconducting material exhibits zero resistance characteristics. Figure 6 It shows the change of the resistance of the sample with temperature. Figure 6 It can be seen that the initial transition temperature of the obtained superconducting sample is 117K, which indicates that the large-size Cu1234 superconducting bulk material prepared by the present invention has good superconducting properties.

[0082] The large-size Cu1234 superconducting bulk material prepared by the present invention is tested for magnetic properties, and the superconducting transition temperature, diamagnetism and superconducting volume fraction information are obtained, such as Figure 7 As shown, Figure 7 It shows the change of magnetic susceptibility of the obtained sample with temperature. Figure 7 It can be seen that the initial transition temperature of the obtained superconducting sample is 117K.

[0083] Table 1

[0084]

[0085] Space group P4 / mmm (No.123), lattice parameters: Unit cell volume:

[0086] Example 2

[0087] A method for preparing a large-size Cu1234 superconducting bulk material comprises the following steps:

[0088] (1) In an inert gas argon atmosphere glove box, high-purity BaO2 powder and high-purity CuO powder were mixed in a molar ratio of 1:1, fully ground and poured into a corundum crucible, placed in a tube furnace, introduced with oxygen, and heated from room temperature to 300°C at a heating rate of 0.1°C / min, synthesized at 300°C for 1 hour, and after synthesis, taken out and transferred into a glove box, and the synthesized block was ground into powder to obtain BaCuO2 compound powder;

[0089] (2) in an inert gas argon atmosphere glove box, high-purity CaO powder and high-purity CuO powder were mixed in a molar ratio of 2:1, fully ground and poured into a corundum crucible, placed in a tube furnace, introduced with oxygen, and heated from room temperature to 300° C. at a heating rate of 0.1° C. / min, synthesized at 300° C. for 1 h, and after synthesis, taken out and transferred into a glove box, and the synthesized block was ground into powder to obtain Ca2CuO3 compound powder;

[0090] (3) in an inert gas argon atmosphere glove box, the BaCuO2 compound powder, the Ca2CuO3 compound powder, high-purity CaO powder, high-purity CuO powder and high-purity BaO2 powder are mixed in a molar ratio of 2:1:1:2:0.7 to obtain a superconducting phase starting reaction mixture;

[0091] (4) using a tablet press at a pressure of 13 MPa, pressing the superconducting phase starting reaction mixture into a dense cylindrical shape with a diameter of 0.1 cm and a height of 0.1 cm to obtain a cylindrical sample;

[0092] (5) Wrapping the cylindrical sample with gold foil to achieve primary sealing, and placing it in a container made of metal molybdenum to achieve secondary sealing to obtain a sealed sample;

[0093] (6) A zirconia insulation layer and a dolomite insulation layer are sequentially arranged around the sealed sample, wherein the thickness of the dolomite insulation layer is 2 mm, and the thickness of the zirconia insulation layer is 2 mm, to obtain a high-pressure assembly block;

[0094] (7) Placing the high-pressure assembly block in an industrial-grade six-sided top press to perform a high-pressure and high-temperature synthesis reaction at a synthesis pressure of 2 GPa, a temperature of 1000° C., and a synthesis time of 0.5 h to obtain the large-sized Cu1234 superconducting bulk material.

[0095] The chemical formula of the large-sized Cu1234 superconducting bulk material prepared in this embodiment is CuBa2Ca3Cu4O 11.4 The large-size Cu1234 superconducting bulk material prepared in this embodiment has a diameter of 0.1 cm and a height of 0.1 cm.

[0096] The large-size Cu1234 superconducting bulk material prepared in this embodiment is tested with reference to the method of Example 1. The initial transition temperature of the sample is specifically 116K. Due to limited space, they are not listed one by one.

[0097] Example 3

[0098] A method for preparing a large-size Cu1234 superconducting bulk material comprises the following steps:

[0099] (1) In an inert gas argon atmosphere glove box, high-purity BaO2 powder and high-purity CuO powder are mixed in a molar ratio of 1:1, fully ground and poured into a corundum crucible, placed in a tube furnace, and oxygen is introduced, and the temperature is increased from room temperature to 500°C at a heating rate of 10°C / min, and synthesized at 500°C for 10 hours. After synthesis, the mixture is taken out and transferred into a glove box, and the synthesized block is ground into powder to obtain BaCuO2 compound powder;

[0100] (2) in an inert gas argon atmosphere glove box, high-purity CaO powder and high-purity CuO powder were mixed in a molar ratio of 2:1, fully ground and poured into a corundum crucible, placed in a tube furnace, introduced with oxygen, and heated from room temperature to 500° C. at a heating rate of 10° C. / min, and synthesized at 500° C. for 10 h. After synthesis, the mixture was taken out and transferred into a glove box, and the synthesized block was ground into powder to obtain a Ca2CuO3 compound powder;

[0101] (3) in an inert gas argon atmosphere glove box, the BaCuO2 compound powder, the Ca2CuO3 compound powder, high-purity CaO powder, high-purity CuO powder and high-purity BaO2 powder are mixed in a molar ratio of 2:1:1:2:0.5 to obtain a superconducting phase starting reaction mixture;

[0102] (4) using a tablet press to press the superconducting phase starting reaction mixture into a dense cylindrical shape with a diameter of 0.5 cm and a height of 0.5 cm at a pressure of 15 MPa to obtain a cylindrical sample;

[0103] (5) Wrapping the cylindrical sample with gold foil to achieve primary sealing, and placing it in a container made of metal molybdenum to achieve secondary sealing to obtain a sealed sample;

[0104] (6) A zirconia insulation layer and a dolomite insulation layer are sequentially arranged around the sealed sample, wherein the thickness of the dolomite insulation layer is 1.5 mm, and the thickness of the zirconia insulation layer is 1.5 mm, to obtain a high-pressure assembly block;

[0105] (7) Place the high-voltage assembly block

[0106] In an industrial-grade six-sided top press, a high-pressure and high-temperature synthesis reaction is carried out, the synthesis pressure is 10 GPa, the temperature is 1000° C., and the synthesis time is 0.5 h, to obtain the large-sized Cu1234 superconducting bulk material.

[0107] The chemical formula of the large-sized Cu1234 superconducting bulk material prepared in this embodiment is CuBa2Ca3Cu4O 11.0 The large-size Cu1234 superconducting bulk material prepared in this embodiment has a diameter of 0.4 cm and a height of 0.4 cm.

[0108] The large-size Cu1234 superconducting bulk material prepared in this embodiment is tested with reference to the method of Example 1 to obtain an initial transition temperature of 116.5 K. Due to limited space, they are not listed one by one.

[0109] Example 4

[0110] A method for preparing a large-size Cu1234 superconducting bulk material comprises the following steps:

[0111] (1) In an inert gas argon atmosphere glove box, high-purity BaO2 powder and high-purity CuO powder are mixed in a molar ratio of 1:1, fully ground and poured into a corundum crucible, placed in a tube furnace, and oxygen is introduced, and the temperature is increased from room temperature to 1000°C at a heating rate of 50°C / min, and synthesized at 1000°C for 50 hours. After synthesis, the mixture is taken out and transferred into a glove box, and the synthesized block is ground into powder to obtain BaCuO2 compound powder;

[0112] (2) in an inert gas argon atmosphere glove box, high-purity CaO powder and high-purity CuO powder were mixed in a molar ratio of 2:1, fully ground and poured into a corundum crucible, placed in a tube furnace, introduced with oxygen, and heated from room temperature to 1000° C. at a heating rate of 50° C. / min, synthesized at 1000° C. for 50 h, taken out after synthesis and transferred into a glove box, and the synthesized block was ground into powder to obtain Ca2CuO3 compound powder;

[0113] (3) in an inert gas argon atmosphere glove box, the BaCuO2 compound powder, the Ca2CuO3 compound powder, high-purity CaO powder, high-purity CuO powder and high-purity BaO2 powder are mixed in a molar ratio of 2:1:1:2:0.3 to obtain a superconducting phase starting reaction mixture;

[0114] (4) using a tablet press to press the superconducting phase starting reaction mixture into a dense cylindrical shape with a diameter of 1.0 cm and a height of 1.0 cm at a pressure of 10 MPa to obtain a cylindrical sample;

[0115] (5) Wrapping the cylindrical sample with gold foil to achieve primary sealing, and placing it in a container made of metal molybdenum to achieve secondary sealing to obtain a sealed sample;

[0116] (6) A zirconia insulation layer and a dolomite insulation layer are sequentially arranged around the sealed sample, wherein the thickness of the dolomite insulation layer is 1 mm, and the thickness of the zirconia insulation layer is 2 mm, to obtain a high-pressure assembly block;

[0117] (7) Placing the high-pressure assembly block in an industrial-grade six-sided top press to perform a high-pressure and high-temperature synthesis reaction at a synthesis pressure of 5 GPa, a temperature of 800° C., and a synthesis time of 5 h to obtain the large-sized Cu1234 superconducting bulk material.

[0118] The chemical formula of the large-sized Cu1234 superconducting bulk material prepared in this embodiment is CuBa2Ca3Cu4O 10.6 The large-size Cu1234 superconducting bulk material prepared in this embodiment has a diameter of 0.9 cm and a height of 0.9 cm.

[0119] The large-size Cu1234 superconducting bulk material prepared in this embodiment is tested with reference to the method of Example 1. The initial transition temperature of the sample is specifically 116.8K. Due to limited space, they are not listed one by one.

[0120] Example 5

[0121] A method for preparing a large-size Cu1234 superconducting bulk material comprises the following steps:

[0122] (1) In an inert gas argon atmosphere glove box, high-purity BaO2 powder and high-purity CuO powder are mixed in a molar ratio of 1:1, and after being fully ground, the mixture is poured into a corundum crucible, and then placed in a tube furnace and oxygen is introduced, and the temperature is increased from room temperature to 1200° C. at a heating rate of 100° C. / min, and synthesized at 1200° C. for 80 h. After the synthesis, the mixture is taken out and transferred into a glove box, and the synthesized block is ground into powder to obtain a BaCuO2 compound powder;

[0123] (2) in an inert gas argon atmosphere glove box, high-purity CaO powder and high-purity CuO powder were mixed in a molar ratio of 2:1, fully ground and poured into a corundum crucible, placed in a tube furnace, introduced with oxygen, and heated from room temperature to 1200° C. at a heating rate of 100° C. / min, synthesized at 1200° C. for 80 h, taken out after synthesis and transferred into a glove box, and the synthesized block was ground into powder to obtain Ca2CuO3 compound powder;

[0124] (3) in an inert gas argon atmosphere glove box, the BaCuO2 compound powder, the Ca2CuO3 compound powder, high-purity CaO powder, high-purity CuO powder and high-purity BaO2 powder are mixed in a molar ratio of 2:1:1:2:0 to obtain a superconducting phase starting reaction mixture;

[0125] (4) using a tablet press to press the superconducting phase starting reaction mixture into a dense cylindrical shape with a diameter of 2.0 cm and a height of 2.0 cm at a pressure of 15 MPa to obtain a cylindrical sample;

[0126] (5) Wrapping the cylindrical sample with gold foil to achieve primary sealing, and placing it in a container made of metal molybdenum to achieve secondary sealing to obtain a sealed sample;

[0127] (6) A zirconia insulation layer and a dolomite insulation layer are sequentially arranged around the sealed sample, wherein the thickness of the dolomite insulation layer is 2 mm, and the thickness of the zirconia insulation layer is 1 mm, to obtain a high-pressure assembly block;

[0128] (7) Placing the high-pressure assembly block in an industrial-grade six-sided top press to perform a high-pressure and high-temperature synthesis reaction at a synthesis pressure of 5 GPa, a temperature of 1400° C., and a synthesis time of 0.1 h to obtain the large-sized Cu1234 superconducting bulk material.

[0129] The chemical formula of the large-sized Cu1234 superconducting bulk material prepared in this embodiment is CuBa2Ca3Cu4O 10.0 The large-size Cu1234 superconducting bulk material prepared in this embodiment has a diameter of 1.8 cm and a height of 1.8 cm.

[0130] The large-size Cu1234 superconducting bulk material prepared in this embodiment is tested with reference to the method of Example 1 to test the starting transition temperature of the sample, which is specifically 117K. Due to limited space, they are not listed one by one.

[0131] Comparative Example 1

[0132] The preparation method of the Cu1234 superconducting bulk material in this embodiment is the same as that in Embodiment 1, except that, in step (5), only one sealing is used, and no secondary sealing is performed.

[0133] The resistance diagram of the Cu1234 superconducting bulk material obtained in this comparative example is as follows: Figure 8 As shown in the figure, it can be seen that the superconducting transition temperature is only 67K, which is far lower than 117K in Example 1, indicating that the superconducting performance of the superconducting block material obtained by only using one sealing is poor.

[0134] Comparative Example 2

[0135] The preparation method of the Cu1234 superconducting bulk material in this embodiment is the same as that in Embodiment 1, except that in step (5), the cylindrical sample is directly placed in a metal molybdenum container and sealed, and the sample is not wrapped with gold foil.

[0136] The resistance diagram of the Cu1234 superconducting bulk material obtained in this comparative example is as follows: Fig. 9 As shown in the figure, it can be seen that the superconducting transition temperature of the obtained sample is 114K, which is lower than 117K, and the magnetic susceptibility value is only one tenth of that of the sample in Example 1, indicating that there are a large number of non-superconducting phases in the sample.

[0137] Comparative Example 3

[0138] The preparation method of the Cu1234 superconducting bulk material in this embodiment is the same as that in Embodiment 1, except that, in step (5), only a zirconium oxide thermal insulation layer is provided, and no dolomite thermal insulation layer is provided.

[0139] The resistance diagram of the Cu1234 superconducting bulk material obtained in this comparative example is as follows: Fig.10 As shown, due to the poor thermal insulation of the method in Comparative Example 3, a large temperature gradient results, and the obtained sample is uneven, containing two superconducting phases, and the superconducting transition temperatures are 66K and 115K, respectively.

[0140] Comparative Example 4

[0141] The preparation method of the Cu1234 superconducting bulk material in this embodiment is the same as that in Embodiment 1, except that, in step (5), only a dolomite insulation layer is provided, and no zirconia insulation layer is provided.

[0142] The resistance diagram of the Cu1234 superconducting bulk material obtained in this comparative example is as follows: Fig.11 As shown. Because the method of comparative example 4 has poor thermal insulation, resulting in a large temperature gradient, the obtained sample is uneven and contains two superconducting phases, and the superconducting transition temperatures are 53K and 116K respectively.

[0143] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a large-size Cu1234 superconducting bulk material, characterized in that: The steps include: (1) BaO2 powder and CuO powder are mixed, ground and synthesized to obtain BaCuO2 compound powder; (2) mixing, grinding and synthesizing CaO powder and CuO powder to obtain Ca2CuO3 compound powder; (3) mixing the BaCuO2 compound powder, the Ca2CuO3 compound powder, CaO powder, CuO powder and BaO2 powder to obtain a superconducting phase starting reaction mixture; (4) pressing the superconducting phase starting reaction mixture into a cylindrical shape to obtain a cylindrical sample; (5) Wrapping the cylindrical sample with gold foil to achieve primary sealing, and placing it in a metal molybdenum container to achieve secondary sealing to obtain a sealed sample; (6) Arranging a thermal insulation layer around the sealed sample to obtain a high-pressure assembly block, wherein the thermal insulation layer is made of dolomite and zirconia; (7) Placing the high-pressure assembly block in an industrial-grade six-sided top press to perform a high-pressure and high-temperature synthesis reaction to obtain the large-sized Cu1234 superconducting bulk material.

2. The method according to claim 1, characterized in that In step (1), the molar ratio of BaO2 powder to CuO powder is 1:1, the synthesis temperature is 300-1200°C, and the synthesis time is 1-80h.

3. The method according to claim 1 or 2, characterized in that: In step (1), the heating rate of the synthesis is 0.1~100℃ / min.

4. The method according to claim 1, characterized in that: In step (2), the molar ratio of CaO powder to CuO powder is 2:1, the synthesis temperature is 300-1200° C., and the synthesis time is 1-80 h.

5. The method according to claim 1 or 4, characterized in that: In step (2), the heating rate of the synthesis is 0.1-100°C / min.

6. The method according to claim 1, characterized in that In step (3), the molar ratio of BaCuO2 compound powder, Ca2CuO3 compound powder, CaO powder, CuO powder and BaO2 powder is 2:1:1:2:δ, wherein 0<δ≤1.

7. The method according to any one of claims 1, 2, 4 or 6, characterized in that: In step (4), the superconducting phase starting reaction mixture is pressed into a cylindrical shape at a pressure of 10-15 MPa, wherein the diameter of the cylinder is 0.1-2 cm and the height is 0.1-2 cm.

8. The method according to claim 1, characterized in that In step (7), the synthesis pressure is 2-10 GPa, the temperature is 800-1400 °C, and the synthesis time is 0.1-5 h.

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