A single-phase Cu1234 superconductor and its preparation method

Abstract

The present invention relates to a single-phase Cu1234 superconductor and a preparation method thereof, belonging to the technical field of superconducting materials, and is used to solve the problem that the method of the prior art cannot prepare a single-phase Cu1234 sample. The method of the present invention prepares a single-phase Cu1234 superconductor, which 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 has low cost. The method of the present invention breaks through the technical difficulties of being difficult to prepare a single-phase Cu1234 superconductor through process optimization and technical improvements, such as by changing raw materials, improving precursor synthesis processes, optimizing stoichiometric ratios and high-pressure synthesis processes, and successfully masters the single-phase Cu1234 superconductor preparation process, and realizes the ability to stably prepare single-phase samples of Cu1234 superconductors, laying a foundation for subsequent Cu1234 superconductor application research.

Description

Technical Field

[0001] The invention relates to the technical field of superconducting materials, and in particular to a single-phase Cu1234 superconductor and a preparation method thereof. Background Art

[0002] Superconducting materials have two major characteristics, zero resistance and complete anti-magnetism, and show broad and far-reaching application prospects in the fields of energy, transportation, medical care, 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. At present, humans have discovered thousands of superconducting materials. Among them, copper-based superconductors represented by copper oxides are currently the only superconducting materials that break through the liquid nitrogen temperature zone under normal pressure conditions, and have great practical value.

[0003] Copper-based superconductors include multiple material systems, each of which has its own characteristics. Although the "thallium" and "mercury" systems have higher critical transition temperatures, they contain volatile and toxic elements, which is not conducive to material preparation and practical application. At present, only the "yttrium" and "bismuth" copper-based superconducting materials have achieved preliminary applications. However, due to the large anisotropy and small irreversible field of the "bismuth" copper-based superconducting materials, its critical current density drops sharply with the increase of temperature and magnetic field, and is not suitable for high-temperature and high-field scenarios. The critical current density of the "yttrium" copper-based superconducting materials decreases slowly with the increase of temperature, which is better than the "bismuth" copper-based superconducting materials and is the first choice for application in high-temperature and high-field environments. However, the superconducting transition temperature of the "yttrium" 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 the "bismuth", "thallium" and "mercury" superconducting materials. In addition, the "yttrium-based" copper-based superconducting materials contain rare earth metal yttrium, and the wire and strip preparation process is complicated. The high manufacturing cost also limits its practical application to a certain extent. Therefore, there is an urgent need for the development of copper-based superconducting materials with simple components, environmental friendliness, low cost, stable properties, and both high superconducting transition temperature and high critical current density.

[0004] "Copper system" copper-based superconductor (chemical formula: CuBa2Ca n-1 Cu n O 2n+2+δ, n=1,2,3……) is one of the important systems in the copper-based superconductor family. According to the naming rules of copper-based superconducting systems, it can be abbreviated as Cu12(n-1)n, where "Cu" is the characteristic metal element in the charge pool, "1" is the number of characteristic metal element layers in the charge pool, "2" is the number of charge pools connected to the superconducting layer, "n-1" is the number of Ca atomic layers in the superconducting layer, and "n" is the number of [CuO2] surfaces in the superconducting layer. Compared with other systems, "copper-based" copper-based superconductors only contain copper, oxygen, and alkaline earth metal elements, with simple components, environmental friendliness, and low cost. "Copper-based" copper-based superconductors contain multiple members, such as Cu1212(CuBa2CaCu2O 6+δ ), Cu1223(CuBa2Ca2Cu3O 8+δ ),Cu1234(CuBa2Ca3Cu4O 10+δ ), Cu1245(CuBa2Ca4Cu5O 12+δ ), etc., in which the Cu1234 in this system has four layers of [CuO2] faces and exhibits the following characteristics: (I) High T c :The critical superconducting transition temperature can reach 118K under normal pressure; (II) High J c :It has a high critical current density in the liquid nitrogen temperature range, and the evolution behavior of critical current density with temperature is better than that of "bismuth series" and comparable to that of "yttrium series" with the best comprehensive superconducting performance; (III) High H irr : The irreversible field in the liquid nitrogen temperature zone is as high as ~20T, which is the highest value in the copper-based superconductor family so far. In addition, although Cu1234 requires high pressure and high temperature conditions for synthesis, it can be recycled under normal pressure conditions, and its superconducting properties remain stable for a long time in an air environment.

[0005] Given that Cu1234 superconductors have intrinsic "three high" characteristics, they have shown great application prospects and are the most likely carrier for the application of high-temperature and high-field superconducting materials in the future liquid nitrogen temperature zone. However, in the process of promoting the practical application of Cu1234 superconductors, there are still many technical difficulties and challenges. One of the most important problems is the difficulty in obtaining high-purity Cu1234 superconducting materials. The presence of impurities seriously affects the current-carrying performance of Cu1234 superconductors, limiting the research progress of Cu1234 superconductors. The chemical formula of Cu1234 superconductors is CuBa2Ca3Cu4O 10+δ, which contains Ba, Ca, Cu and O elements. These elements can form different reactants under different temperature and pressure conditions, that is, they have a complex phase diagram. Take Ca-Cu-O as an example. Under normal pressure and different temperatures, products such as Ca2CuO3 and CaCu2O3 can be generated; under high pressure and different temperatures, products such as tetragonal CaCuO2(Ⅰ) and monoclinic CaCuO2(Ⅱ) can be generated (Journal of solid state chemistry 132, 274-283, 1997). The Ba-Cu-O system also has a complex phase diagram. As a member of the Ba-Ca-Cu-O quaternary phase space, how to obtain high-purity Cu1234 superconductors is a difficulty in the field of material preparation, and it is also the technical bottleneck that currently restricts the practical research of Cu1234 superconductors. In the early research progress, the technical level was low, and the product contained a large amount of Cu1223, Cu1245 and BaCuO2 and other impurities (Physica C 224, 69-74, 1994; Jpn. J. Appl. Phys. 33, L503-506, 1994). In the recent research progress, the technical level has been improved, but the product still contains a small amount of CaCuO2 and other impurities (for example, Sci. Adv. 2018; 4: eaau0192; Patent: CN117819959A), and single-phase Cu1234 superconducting samples are still not available.

[0006] The existing preparation technology of Cu1234 superconductors is not yet mature, and the Cu1234 superconductors prepared by different researchers using different process flows contain different impurity phases. The Cu1234 superconductors obtained by some preparation processes contain other superconducting phases, such as Cu1223 and Cu1245, resulting in multiple superconducting transitions on the magnetic susceptibility curve; the Cu1234 superconductors obtained by some preparation processes contain other non-superconducting phases, such as CaCuO2, BaCuO2, etc., resulting in a large number of impurity diffraction peaks on the X-ray diffraction spectrum; the Cu1234 superconductors obtained by some preparation processes also contain some unknown impurity phases. Therefore, the Cu1234 superconductors prepared by the existing technology all have impurities, which seriously affect the current-carrying performance of the Cu1234 superconductors, and therefore cannot be used in the practical research of Cu1234 superconductors.

[0007] For example: Previously, some studies reported that Ba2CaCu2O5 was used as a precursor and Ag2O was used as an oxidant to prepare Cu1234 superconductors at 5GPa and 1200°C. The products contained a large amount of Cu1223 impurities (Physica C 224, 69-74). In addition, some studies reported that Ba2CaCu5O8, Ba2CaCu4O7, Ba2Ca3Cu4O9 were used as precursors and CaO2 was used as an oxidant to prepare Cu1234 superconductors at 5GPa and 1100°C. The products contained a large amount of Cu1245 and BaCuO2 impurities (Jpn. J. Appl. Phys. 33, L503-506, 1994). In addition, some studies reported that BaCuO 2.13 The Cu1234 superconductor prepared by using Ca2CuO3 as precursor and Ag2O as oxidant at 3.5GPa and 1100-1150℃ contains about 7% CaCuO2 impurity (Sci.Adv.2018;4:eaau0192). The Cu1234 superconductors prepared by the prior art all contain impurities, and single-phase Cu1234 superconductors cannot be obtained. Summary of the invention

[0008] In view of the above analysis, the present invention aims to provide a single-phase Cu1234 superconductor and a preparation method thereof, so as to solve the problems that the single-phase Cu1234 superconductor synthesized by the existing method is accompanied by a large amount of symbiotic phases such as Cu1223 and Cu1245, and the single-phase Cu1234 superconductor cannot be accurately prepared.

[0009] In the first aspect, the present invention provides a method for preparing a single-phase Cu1234 superconductor, comprising using CaO2 as an oxidant, BaCuO2 and Ca2CuO3 as precursors, mixing BaCuO2, Ca2CuO3, CuO, CaO and CaO2 to obtain a mixed powder, and subjecting the mixed powder to a high-pressure synthesis reaction to obtain the single-phase Cu1234 superconductor.

[0010] Furthermore, the pressure of the high-pressure synthesis is 5-8 GPa, the synthesis temperature is 1100-1200° C., and the synthesis time is 10-100 min.

[0011] Furthermore, the heating rate in the high pressure synthesis is 1000-2000°C / min.

[0012] Furthermore, the molar ratio of BaCuO2, Ca2CuO3, CuO, CaO and CaO2 is 2:1:x:(1-y):y, wherein 1.6≤x≤2.0, 0.5≤y≤1.

[0013] Furthermore, the BaCuO2 is prepared by the following method: BaO and CuO are used as raw materials, BaO and CuO are mixed in a molar ratio of 1:1, pre-pressed into discs, sintered to obtain sample A, repeatedly grinding the sample A, pressing it into discs, and sintering the step at least 3 times to obtain single-phase BaCuO2.

[0014] Further, sample A is obtained by sintering at 700-1000°C for 12-96h.

[0015] Furthermore, Ca2CuO3 is prepared by the following method: using CaO and CuO as raw materials, CaO and CuO are mixed in a molar ratio of 2:1, pre-pressed into discs, sintered to obtain sample B, repeatedly grinding the sample B, pressing it into discs, and sintering the step at least 3 times to obtain single-phase Ca2CuO3.

[0016] Further, sample B is obtained by sintering at 800-1100°C for 12-36h.

[0017] Furthermore, the mixed powder is pressed into a disc shape, sealed with a gold cylinder, and placed in the cavity of a six-sided top press to perform a high-pressure synthesis reaction.

[0018] In a second aspect, the present invention provides a single-phase Cu1234 superconductor prepared by the above method, wherein the molecular formula of the single-phase Cu1234 superconductor is Cu x-1 Ba2Ca3Cu4O 10+δ , where 1.6≤x≤2.0, 0≤δ≤1.

[0019] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0020] The method of the present invention prepares a single-phase Cu1234 superconductor, which 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 has low cost. The method of the present invention breaks through the technical difficulties of preparing single-phase Cu1234 superconductors through process optimization and technical improvements, such as changing raw materials, improving precursor synthesis processes, optimizing stoichiometric ratios and high-pressure synthesis processes, and successfully masters the single-phase Cu1234 superconductor preparation process, achieves the ability to stably prepare single-phase Cu1234 superconductors, and lays a foundation for subsequent Cu1234 superconductor application research.

[0021] 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

[0022] 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.

[0023] Figure 1 The X-ray diffraction spectrum of the single-phase BaCuO2 prepared in Example 1 of the present invention;

[0024] Figure 2 The X-ray diffraction spectrum of the single-phase Ca2CuO3 prepared in Example 1 of the present invention;

[0025] Figure 3 This is a schematic diagram of the mixed powder in the gold cylinder according to Example 1 of the present invention;

[0026] Figure 4 This is a physical picture of the single-phase Cu1234 superconductor sample prepared in Example 1 of the present invention;

[0027] Figure 5 X-ray diffraction spectra of the Cu1234 superconductors prepared in Example 1 and Comparative Example 5 of the present invention;

[0028] Figure 6 This is a fitting diagram of the X-ray diffraction spectrum of the single-phase Cu1234 superconductor prepared in Example 1 of the present invention;

[0029] Figure 7 This is a test diagram of the magnetic susceptibility of a single-phase Cu1234 superconductor prepared in Example 1 of the present invention;

[0030] Figure 8 A comparison chart of X-ray diffraction spectra of samples prepared in Comparative Examples 1-4 and Example 1 of the present invention;

[0031] Fig. 9 These are the standard XRD patterns of Cu1223 superconductor, Cu1245 superconductor and Cu1234 superconductor. DETAILED DESCRIPTION

[0032] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention 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.

[0033] A specific embodiment of the present invention discloses a method for preparing a single-phase Cu1234 superconductor, comprising using CaO2 as an oxidant, BaCuO2 and Ca2CuO3 as precursors, mixing BaCuO2, Ca2CuO3, CuO, CaO and CaO2 to obtain a mixed powder, and subjecting the mixed powder to a high-pressure synthesis reaction to obtain the single-phase Cu1234 superconductor.

[0034] Compared with the prior art, the present invention uses CaO2 as an oxidant and BaCuO2 and Ca2CuO3 as precursors for a high-pressure synthesis reaction to obtain a single-phase Cu1234 superconductor.

[0035] In a specific embodiment, the pressure of high pressure synthesis is 5-8 GPa, for example, 5 GPa, 5.5 GPa, 6 GPa, 6.5 GPa, 7 GPa, 7.5 GPa, 8 GPa, the synthesis temperature is 1100-1200° C. For example, 1100° C., 1110° C., 1120° C., 1130° C., 1140° C., 1150° C., 1160° C., 1170° C., 1180° C., 1190° C., 1200° C., and the synthesis time is 10-100 min, for example, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min.

[0036] In a specific embodiment, the heating rate in the high pressure synthesis is 1000-2000°C / min, for example, 1000°C / min, 1100°C / min, 1200°C / min, 1300°C / min, 1400°C / min, 1500°C / min, 1600°C / min, 1700°C / min, 1800°C / min, 1900°C / min, 2000°C / min.

[0037] It should be noted that, after a large number of experiments, the inventors found that the use of the above-mentioned high-pressure reaction condition parameters can greatly increase the high-pressure synthesis heating rate, reduce and inhibit the generation of impurities during the heating process, and is conducive to the preparation of single-phase Cu1234 superconductors.

[0038] In a specific embodiment, the molar ratio of BaCuO2, Ca2CuO3, CuO, CaO and CaO2 is 2:1:x:(1-y):y, wherein 1.6≤x≤2.0, for example, x is 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2, and 0.5≤y≤1, for example, y is 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.

[0039] There are some Cu and O vacancies in the charge reservoir layer of Cu1234 superconductor. The number of copper and oxygen vacancies is closely related to the initial stoichiometric ratio of raw materials and the content of oxidant. A large number of experiments have shown that when the Cu content of the charge reservoir layer is 1.6-2.0 and the content of oxidant CaO2 is 0.5-1.0, the prepared sample does not contain impurities, so the above ratio is conducive to the preparation of single-phase Cu1234 superconductor.

[0040] In a specific embodiment, BaCuO2 is prepared by the following method: BaO and CuO are used as raw materials, BaO and CuO are mixed in a molar ratio of 1:1, pre-pressed into discs, sintered to obtain sample A, repeatedly grinding the sample A, pressing it into discs, and sintering the step at least 3 times to obtain single-phase BaCuO2.

[0041] In a specific embodiment, sample A is obtained by sintering at 700-1000°C (for example, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C) for 12-96h (for example, 12h, 15h, 20h, 25h, 30h, 35h, 40h, 45h, 50h, 55h, 60h, 65h, 70h, 75h, 80h, 85h, 90h, 96h).

[0042] In a specific embodiment, Ca2CuO3 is prepared by the following method: using CaO and CuO as raw materials, CaO and CuO are mixed in a molar ratio of 2:1, pre-pressed into discs, sintered to obtain sample B, repeatedly grinding the sample B, pressing it into discs, and sintering the step at least 3 times to obtain single-phase Ca2CuO3.

[0043] Specifically, through the above-mentioned repeated sintering and pre-pressing into discs, the powders can be fully contacted to participate in the solid phase reaction to obtain single-phase BaCuO2 and single-phase Ca2CuO3, which is more conducive to the subsequent high-pressure synthesis reaction to prepare a single-phase Cu1234 superconductor.

[0044] In a specific embodiment, the sample B is obtained by sintering at 800-1100°C (for example, 800°C, 820°C, 840°C, 860°C, 880°C, 900°C, 920°C, 940°C, 960°C, 980°C, 1000°C, 1020°C, 1040°C, 1060°C, 1080°C, 1100°C) for 12-36h (for example, 12h, 14h, 16h, 18h, 20h, 22h, 24h, 26h, 28h, 30h, 32h, 34h, 36h).

[0045] In a specific embodiment, the mixed powder is pressed into a disc shape, sealed with a gold cylinder, and placed in the cavity of a six-sided top press to perform a high-pressure synthesis reaction.

[0046] It should be noted that the function of sealing is to ensure that the oxygen released by CaO2 during the reaction does not overflow and fully participates in the synthesis reaction of Cu1234 superconductor. The purity of BaO, CuO and CaO is ≥99.9%. In addition, the entire reaction process of the present invention needs to be carried out in an inert atmosphere.

[0047] Another specific embodiment of the present invention discloses a single-phase Cu1234 superconductor prepared by the above method, wherein the molecular formula of the single-phase Cu1234 superconductor is Cu x-1 Ba2Ca3Cu4O 10+δ , where 1.6≤x≤2.0, 0≤δ≤1.

[0048] In the present invention, the molar ratio of BaCuO2, Ca2CuO3, CuO, CaO and CaO2 is controlled to be 2:1:x:(1-y):y, and the ingredients are prepared, thereby obtaining a molecular formula of Cu x-1 Ba2Ca3Cu4O 10+δ The stoichiometric ratio is closer to the actual ratio of each element in the Cu1234 material, which prevents the segregation of element ratios and causes the generation of impurities.

[0049] A single-phase Cu1234 superconductor is prepared by the method of the present invention. The superconductor 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 has low cost. The method of the present invention breaks through the technical difficulties of preparing a single-phase Cu1234 superconductor through process optimization and technical improvement, by changing raw materials, improving precursor synthesis process, optimizing stoichiometric ratio and high-pressure synthesis process and other methods, successfully masters the preparation process of a single-phase Cu1234 superconductor, realizes the ability to stably prepare a single-phase Cu1234 superconductor, and lays a foundation for subsequent Cu1234 superconductor application research.

[0050] It should be noted that the single-phase Cu1234 superconductor prepared in the present invention refers to a mixed phase that does not contain superconducting phases such as Cu1245 and Cu1223 and non-superconducting phases such as CaCuO2 and BaCuO2.

[0051] The technical solution of the present invention is further explained below in conjunction with specific embodiments.

[0052] Example 1

[0053] A method for preparing a single-phase Cu1234 superconductor in this embodiment comprises the following steps:

[0054] (1) In an inert gas argon atmosphere glove box, BaO and CuO were used as raw materials. BaO and CuO were mixed uniformly in a molar ratio of 1:1, and pre-pressed into discs so that the powder particles were fully contacted to participate in the solid phase reaction. The sample A was sintered at 700°C for 96 hours to obtain sample A. The sample A was taken out and fully ground, pressed into discs again, and then sintered again. The sintering was repeated 3 times to obtain single-phase BaCuO2. The X-ray diffraction spectrum of the single-phase BaCuO2 is shown in FIG. Figure 1 As shown;

[0055] (2) In an inert gas argon atmosphere glove box, CaO and CuO were used as raw materials. CaO and CuO were mixed uniformly in a molar ratio of 2:1, and pre-pressed into discs so that the powder particles were fully contacted to participate in the solid phase reaction. The sample was sintered at 800°C for 36 hours to obtain sample B. The sample B was taken out and fully ground, pressed into discs again, and then sintered again. The sintering was repeated 3 times to obtain single-phase Ca2CuO3. The X-ray diffraction spectrum of the single-phase Ca2CuO3 is as shown in FIG. Figure 2 As shown;

[0056] (3) In an inert gas argon atmosphere glove box, single-phase BaCuO2 and single-phase Ca2CuO3 are mixed as precursors with CuO, CaO and CaO2 to obtain a mixed powder, wherein the molar ratio of BaCuO2, Ca2CuO3, CuO, CaO and CaO2 is 2:1:x:(1-y):y, x=1.6, y=1.0;

[0057] (4) Pressing the mixed powder into a disc, and sealing the disc in a gold cylinder, such as Figure 3 As shown, the mixed powder wrapped in the gold tube is placed in the cavity of a six-sided top press, and high-pressure synthesis is carried out for 10 minutes at a pressure of 5 GPa, a temperature of 1150°C, and a heating rate of 1200°C / min. After the high-pressure synthesis is completed, the sample is taken out, and the gold tube sealed outside the sample is peeled off to obtain a single-phase Cu1234 superconductor.

[0058] The molecular formula of the single-phase Cu1234 superconductor prepared in this embodiment is Cu 0.6 Ba2Ca3Cu4O 10

[0059] The actual picture of the single-phase Cu1234 superconductor sample prepared in this example is as follows Figure 4 The X-ray diffraction spectrum is shown in Figure 5 As shown, the X-ray diffraction spectrum of the single-phase Cu1234 superconductor prepared in this embodiment was analyzed and fitted, and the results were as follows Figure 6 The standard XRD patterns of Cu1223 superconductor, Cu1245 superconductor and Cu1234 superconductor are shown in Figure 2. Fig. 9 As shown, from Figure 6 and9 It can be seen that the synthesized Cu1234 superconductor does not contain Cu1223 and Cu1245 phases.

[0060] The magnetic properties of the single-phase Cu1234 superconductor prepared in this embodiment were tested, and the results were as follows: Figure 7 As shown, the results show that the magnetic susceptibility is -1, indicating that it has complete anti-magnetism, indicating that the prepared samples are all superconducting Cu1234 single phase and do not contain other impurities, indicating that the synthesized Cu1234 sample is a single-phase superconductor.

[0061] Example 2

[0062] A method for preparing a single-phase Cu1234 superconductor in this embodiment comprises the following steps:

[0063] (1) In an inert gas argon atmosphere glove box, BaO and CuO were used as raw materials, BaO and CuO were mixed uniformly in a molar ratio of 1:1, and pre-pressed into discs so that the powder particles were fully contacted to participate in the solid phase reaction, and sintered at 1000° C. for 12 h to obtain sample A. The sample A was taken out and fully ground, pressed into discs again, and then sintered again. The sintering was repeated 3 times to obtain single-phase BaCuO2. The X-ray diffraction spectrum of the single-phase BaCuO2 was basically consistent with that of Example 1;

[0064] (2) In an inert gas argon atmosphere glove box, using CaO and CuO as raw materials, CaO and CuO were mixed uniformly in a molar ratio of 2:1, pre-pressed into discs so that the powder particles were fully in contact and participated in the solid phase reaction, and sintered at 1100° C. for 12 h to obtain sample B. The sample B was taken out and fully ground, pressed into discs again, and then sintered again. The sintering was repeated 3 times to obtain single-phase Ca2CuO3. The X-ray diffraction spectrum of the single-phase Ca2CuO3 was basically consistent with that of Example 1;

[0065] (3) In an inert gas argon atmosphere glove box, single-phase BaCuO2 and single-phase Ca2CuO3 are mixed as precursors with CuO, CaO and CaO2 to obtain a mixed powder, wherein the molar ratio of BaCuO2, Ca2CuO3, CuO, CaO and CaO2 is 2:1:x:(1-y):y, x=1.7, y=0.8;

[0066] (4) Pressing the mixed powder into a disc, sealing the disc inside a gold tube, placing the mixed powder wrapped in the gold tube in the cavity of a six-sided press, performing high-pressure synthesis for 100 minutes at a pressure of 8 GPa, a temperature of 1100°C, and a heating rate of 2000°C / min. After the high-pressure synthesis is completed, take out the sample, peel off the gold tube sealed outside the sample, and obtain a single-phase Cu1234 superconductor.

[0067] The molecular formula of the single-phase Cu1234 superconductor prepared in this embodiment is Cu 0.7 Ba2Ca3Cu4O 10.3 .

[0068] The physical image of the single-phase Cu1234 superconductor sample prepared in this embodiment is basically consistent with that in Example 1, and the X-ray diffraction spectrum is basically consistent with that in Example 1. The X-ray diffraction spectrum of the single-phase Cu1234 superconductor prepared in this embodiment is analyzed and fitted, and the results are basically consistent with those in Example 1, indicating that the synthesized Cu1234 superconductor is a single-phase sample.

[0069] The magnetic properties of the single-phase Cu1234 superconductor prepared in this example were tested, and the results were basically consistent with those in Example 1. The results showed that the magnetic susceptibility was -1, indicating that the synthesized Cu1234 sample was a single-phase superconductor.

[0070] Example 3

[0071] A method for preparing a single-phase Cu1234 superconductor in this embodiment comprises the following steps:

[0072] (1) In an inert gas argon atmosphere glove box, BaO and CuO were used as raw materials, BaO and CuO were mixed uniformly in a molar ratio of 1:1, and pre-pressed into discs so that the powder particles were fully contacted to participate in the solid phase reaction, and sintered at 800° C. for 60 h to obtain sample A. The sample A was taken out and fully ground, pressed into discs again, and then sintered again. The sintering was repeated 3 times to obtain single-phase BaCuO2. The X-ray diffraction spectrum of the single-phase BaCuO2 was basically consistent with that of Example 1;

[0073] (2) In an inert gas argon atmosphere glove box, CaO and CuO were used as raw materials, CaO and CuO were mixed uniformly in a molar ratio of 2:1, and pre-pressed into discs so that the powder particles were fully contacted to participate in the solid phase reaction, and sintered at 900°C for 30 hours to obtain sample B. The sample B was taken out and fully ground, pressed into discs again, and then sintered again. The sintering was repeated 3 times to obtain single-phase Ca2CuO3. The X-ray diffraction spectrum of the single-phase Ca2CuO3 was basically consistent with that of Example 1;

[0074] (3) In an inert gas argon atmosphere glove box, single-phase BaCuO2 and single-phase Ca2CuO3 are mixed as precursors with CuO, CaO and CaO2 to obtain a mixed powder, wherein the molar ratio of BaCuO2, Ca2CuO3, CuO, CaO and CaO2 is 2:1:x:(1-y):y, x=1.8, y=0.6;

[0075] (4) Pressing the mixed powder into a disc, sealing the disc inside a gold tube, placing the mixed powder wrapped in the gold tube in the cavity of a six-sided press, and performing high-pressure synthesis for 60 minutes at a pressure of 6 GPa, a temperature of 1150° C., and a heating rate of 1500° C. / min. After the high-pressure synthesis is completed, the sample is taken out, and the gold tube sealed outside the sample is peeled off to obtain a single-phase Cu1234 superconductor.

[0076] The molecular formula of the single-phase Cu1234 superconductor prepared in this embodiment is Cu 0.8 Ba2Ca3Cu4O 10.6 .

[0077] The physical image of the single-phase Cu1234 superconductor sample prepared in this embodiment is basically consistent with that in Example 1, and the X-ray diffraction spectrum is basically consistent with that in Example 1. The X-ray diffraction spectrum of the single-phase Cu1234 superconductor prepared in this embodiment is analyzed and fitted, and the results are basically consistent with those in Example 1, indicating that the synthesized Cu1234 superconductor is a single-phase sample.

[0078] The magnetic properties of the single-phase Cu1234 superconductor prepared in this example were tested, and the results were basically consistent with those in Example 1. The results showed that the magnetic susceptibility was -1, indicating that the synthesized Cu1234 sample was a single-phase superconductor.

[0079] Example 4

[0080] A method for preparing a single-phase Cu1234 superconductor in this embodiment comprises the following steps:

[0081] (1) In an inert gas argon atmosphere glove box, BaO and CuO were used as raw materials, BaO and CuO were mixed uniformly in a molar ratio of 1:1, and pre-pressed into discs so that the powder particles were fully contacted to participate in the solid phase reaction, and sintered at 900° C. for 30 hours to obtain sample A. The sample A was taken out and fully ground, pressed into discs again, and then sintered again. The sintering was repeated 3 times to obtain single-phase BaCuO2. The X-ray diffraction spectrum of the single-phase BaCuO2 was basically consistent with that of Example 1;

[0082] (2) In an inert gas argon atmosphere glove box, using CaO and CuO as raw materials, CaO and CuO were mixed uniformly in a molar ratio of 2:1, pre-pressed into discs so that the powder particles were fully contacted to participate in the solid phase reaction, and sintered at 1000° C. for 20 h to obtain sample B. The sample B was taken out and fully ground, pressed into discs again, and then sintered again. The sintering was repeated 3 times to obtain single-phase Ca2CuO3. The X-ray diffraction spectrum of the single-phase Ca2CuO3 was basically consistent with that of Example 1;

[0083] (3) In an inert gas argon atmosphere glove box, single-phase BaCuO2 and single-phase Ca2CuO3 are mixed as precursors with CuO, CaO and CaO2 to obtain a mixed powder, wherein the molar ratio of BaCuO2, Ca2CuO3, CuO, CaO and CaO2 is 2:1:x:(1-y):y, x=2.0, y=0.5;

[0084] (4) Pressing the mixed powder into a disc, sealing the disc inside a gold tube, placing the mixed powder wrapped in the gold tube in the cavity of a six-sided top press, and performing high-pressure synthesis for 30 minutes at a pressure of 7 GPa, a temperature of 1150°C, and a heating rate of 1200°C / min. After the high-pressure synthesis is completed, take out the sample, peel off the gold tube sealed outside the sample, and obtain a single-phase Cu1234 superconductor.

[0085] The molecular formula of the single-phase Cu1234 superconductor prepared in this embodiment is Cu 0.9 Ba2Ca3Cu4O 11 .

[0086] The physical image of the single-phase Cu1234 superconductor sample prepared in this embodiment is basically consistent with that in Example 1, and the X-ray diffraction spectrum is basically consistent with that in Example 1. The X-ray diffraction spectrum of the single-phase Cu1234 superconductor prepared in this embodiment is analyzed and fitted, and the results are basically consistent with those in Example 1, indicating that the synthesized Cu1234 superconductor is a single-phase sample.

[0087] The magnetic properties of the single-phase Cu1234 superconductor prepared in this example were tested, and the results were basically consistent with those in Example 1. The results showed that the magnetic susceptibility was -1, indicating that the synthesized Cu1234 sample was a single-phase superconductor.

[0088] Comparative Example 1

[0089] The method for preparing the Cu1234 superconductor in this comparative example is the same as that in Example 1, except that in step (1), only one sintering is used to prepare BaCuO2.

[0090] Comparative Example 2

[0091] The method for preparing the Cu1234 superconductor in this comparative example is the same as that in Example 1, except that in step (2), only one sintering is used to prepare Ca2CuO3.

[0092] Comparative Example 3

[0093] The method for preparing the Cu1234 superconductor in this comparative example is the same as that in Example 1, except that in step (3), x=0.3.

[0094] Comparative Example 4

[0095] The method for preparing the Cu1234 superconductor in this comparative example is the same as that in Example 1, except that in step (4), the pressure is 3 GPa and the temperature is 900°C.

[0096] Comparative Example 5

[0097] The Cu1234 superconducting bulk material was prepared according to the method of Example 1 in patent CN117819959A.

[0098] The XRD of the Cu1234 superconducting bulk material prepared in this comparative example is compared with the XRD of the Cu1234 superconductor prepared in Example 1. Figure 5 As shown, (* in the figure indicates impurity phase). It can be seen from the figure that the Cu1234 superconducting bulk material prepared in Comparative Example 5 has impurity phase compared with Example 1. The main reason is that the decomposition temperature of CaO2 in Example 1 is relatively low, and it can decompose and produce oxygen at 315°C, which fully participates in the Cu1234 synthesis reaction and inhibits the generation of impurity phase.

[0099] Test Example 1

[0100] The XRD of Cu1234 superconductors prepared in Comparative Examples 1-4 were tested respectively and compared with that in Example 1. The results are as follows: Figure 8 As shown in the figure, it can be seen that the samples prepared in Comparative Examples 1-4 all contain a large amount of impurity phases (the impurity phases are represented by * in the figure).

[0101] 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 single-phase Cu1234 superconductor, characterized in that: The method comprises using CaO2 as an oxidant, BaCuO2 and Ca2CuO3 as precursors, mixing BaCuO2, Ca2CuO3, CuO, CaO and CaO2 to obtain a mixed powder, and subjecting the mixed powder to a high-pressure synthesis reaction to obtain the single-phase Cu1234 superconductor; The pressure of high-pressure synthesis is 5-8GPa, and the synthesis temperature is 1100-1200℃; The heating rate in high pressure synthesis is 1000-2000℃ / min; The molar ratio of BaCuO2, Ca2CuO3, CuO, CaO and CaO2 is 2:1:x:(1-y):y, wherein 1.6≤x≤2.0, 0.5≤y≤1; The BaCuO2 is prepared by the following method: BaO and CuO are used as raw materials, BaO and CuO are mixed in a molar ratio of 1:1, pre-pressed into discs, sintered to obtain sample A, and the sample A is repeatedly ground, pressed into discs, and sintered at least 3 times to obtain single-phase BaCuO2; Ca2CuO3 is prepared by the following method: using CaO and CuO as raw materials, CaO and CuO are mixed in a molar ratio of 2:1, pre-pressed into discs, sintered to obtain sample B, repeatedly grinding the sample B, pressing it into discs, and sintering the step at least 3 times to obtain single-phase Ca2CuO3.

2. The method for preparing a single-phase Cu1234 superconductor according to claim 1, characterized in that: The synthesis time is 10-100min.

3. The method for preparing a single-phase Cu1234 superconductor according to claim 1, characterized in that: Sinter at 700-1000°C for 12-96h to obtain sample A.

4. The method for preparing a single-phase Cu1234 superconductor according to claim 1, characterized in that: Sinter at 800-1100°C for 12-36h to obtain sample B.

5. The method for preparing a single-phase Cu1234 superconductor according to claim 1, characterized in that: The mixed powder is pressed into a disc shape, sealed with a gold cylinder, and placed in the cavity of a six-sided top press to perform a high-pressure synthesis reaction.

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