A Cu1223 superconductor and preparation method thereof

Abstract

The present invention relates to a Cu1223 superconductor and a preparation method thereof, belonging to the technical field of superconducting materials, and is used to solve the problems that a large amount of Cu1234 intergrowth phases are present in the Cu1223 superconductor synthesized by the existing method, and the Cu1223 superconductor cannot be accurately prepared. The present invention uses KClO4 as an oxidant, adopts a sandwich structure for assembly, and the mixed powder is wrapped with gold foil to prevent the decomposition product KCl from entering the sample and causing pollution. By accurately adjusting the synthesis condition parameters, a Cu1223 superconductor without intergrowth phases is prepared.

Description

Technical Field

[0001] The invention relates to the technical field of superconducting materials, and in particular to a Cu1223 superconductor and a preparation method thereof. Background Art

[0002] Superconducting materials have two major characteristics, namely zero resistance and complete anti-magnetism, and show 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. Although humans have discovered thousands of superconducting materials, 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. They are also the only carrier for superconducting applications in the liquid nitrogen temperature zone and have high practical value.

[0003] Copper-based superconductors include multiple material systems, such as "yttrium system", "bismuth system", "thallium system", "mercury system" and "copper system". Each of these systems contains multiple members according to the number of copper-oxygen surface layers contained in the unit cell. For example, the chemical formula of the "bismuth system" is Bi2Sr2Ca n-1 Cu n O 2n+4+δ According to the different number of copper-oxygen layers in the unit cell, the "bismuth system" includes Bi2201 (chemical formula Bi2Sr2CuO 6+δ ), Bi-2212 (chemical formula is Bi2Sr2CaCu2O 8+δ ), Bi-2223 (chemical formula is Bi2Sr2Ca2Cu3O 10+δ )、Bi-2234 (chemical formula is Bi2Sr2Ca3Cu4O 12+δ )、Bi-2245(chemical formula is Bi2Sr2Ca4Cu5O 14+δ )、Bi-2256 (chemical formula is Bi2Sr2Ca5Cu6O 16+δ ) and many other members. The crystal structures of multiple members of the same copper-based superconductor system are similar, and the superconducting properties are similar. The only difference is the number of copper-oxygen planes contained in the unit cell. Therefore, the copper-based material family with multiple members is an important tool for studying the superconductivity mechanism and clarifying the factors that determine the superconducting transition temperature (T c ) is an ideal material system with key intrinsic factors. Since the discovery of high T in copper-based superconductors c Since superconductivity, the copper-based superconducting T c The general empirical law is that the T of multiple members of the same system c,max As the number of copper-oxygen surfaces (n) in the unit cell changes, when n = 3, T c,max Highest.

[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 ) and Cu1256(CuBa2Ca5Cu6O 14+δ ), etc. Their crystal structures are Figure 1 As shown. The copper-based superconducting system of the "copper system" has a full perovskite configuration, especially the charge reservoir layer has a compressed [CuO6] octahedral coordination configuration, which shortens the interlayer distance and significantly enhances the interlayer coupling. This coupling reduces the superconducting anisotropy, effectively improves the flux pinning strength, and significantly improves the evolution of the critical current density with temperature and magnetic field, ensuring that the "copper system" has excellent high-temperature and high-field current-carrying performance, and is one of the potential mainstream material systems for future superconducting applications in the liquid nitrogen temperature zone.

[0005] In addition, in copper-based superconductors, the copper-oxygen plane plays a decisive role in superconductivity. The unit cell of "copper-based" copper-based superconductors contains copper-oxygen planes with different coordination configurations, such as [CuO6] octahedron, [Cu O5] pyramid and [CuO4] quadrilateral, etc. Figure 2 As shown, these copper-oxygen surfaces with different coordination configurations provide rich materials for studying the mechanism of copper-based superconductivity. Therefore, "copper-based" superconductors are an ideal material system for studying the mechanism of copper-based superconductivity.

[0006] Cu1223(CuBa2Ca2Cu3O 8+δ) has copper-oxygen coordination configurations such as hexacoordinated octahedron, pentacoordinated pyramid and tetracoordinated planar quadrilateral. At the same time, a single unit cell of the material contains three layers of copper-oxygen planes (n=3). According to empirical rules, Cu1223 should have the highest superconducting transition temperature in the system. Therefore, this superconducting material has always been one of the superconducting materials that people pay close attention to. However, in actual research, it is found that it is currently impossible to prepare single-phase Cu1223 superconducting materials. The main reason is that the elements contained in each member of the "copper series" superconducting family are the same and the crystal structure is similar, resulting in similar synthesis conditions, which is very easy to produce symbiosis, and it is difficult to obtain single-phase Cu1223 materials. For example, in the process of synthesizing Cu1223, the product is accompanied by a large amount of Cu1234 superconducting phase and non-superconducting impurities such as CaCuO2 (Physica C 224, 69-74, 1994; Jpn. J. Appl. Phys. 33, L503-506, 1994). The above symbiotic phenomenon also frequently occurs in other copper-based superconducting systems, and is a technical challenge in the field of copper-based superconducting research. How to achieve accurate preparation of Cu1223 superconductors and break through and master the preparation method of Cu1223 is a technical challenge. Summary of the invention

[0007] In view of the above analysis, the present invention aims to provide a Cu1223 superconductor and a preparation method thereof, so as to solve the problems that the Cu1223 superconductor synthesized by the existing method is accompanied by a large amount of Cu1234 and Cu1245 symbiotic phases, and the Cu1223 superconductor cannot be accurately prepared.

[0008] In a first aspect, the present invention provides a Cu1223 superconductor, wherein the molecular formula of the Cu1223 superconductor is Cu x Ba2Ca2Cu3O 8+δ , where 0.6≤x≤0.9, 0≤δ≤1.

[0009] Furthermore, the Cu1223 superconductor is synthesized under high pressure using KClO4 as an oxidant and BaCuO2 and Ca2CuO3 as precursors.

[0010] Furthermore, the molar ratio of BaCuO2, Ca2CuO3 and CuO is 2:1:x, wherein 0.6≤x≤0.9.

[0011] Furthermore, the pressure of the high pressure synthesis is 4.5-5.5 GPa, the temperature is 980-1020°C, and the reaction time is 10-60 min.

[0012] In a second aspect, the present invention provides a method for preparing a Cu1223 superconductor, comprising KClO4 as an oxidant, BaCuO2 and Ca2CuO3 as precursors, and specifically comprising the following steps:

[0013] (1) mixing BaCuO2, Ca2CuO3 and CuO to obtain an initial mixed powder;

[0014] (2) After 1 / 2 weight of KClO4 is loaded into the bottom of the gold cylinder, the initial mixed powder is put into the middle of the gold cylinder, and the remaining 1 / 2 weight of KClO4 is added to the top of the gold cylinder to form a sandwich structure, and the KClO4 and the initial mixed powder are sealed and isolated with silver foil;

[0015] (3) The gold cylinder containing the sandwich structure is sealed and subjected to high pressure synthesis to obtain a Cu1223 superconductor.

[0016] Furthermore, in step (2), the mass ratio of the mixed powder to KClO4 is 1:y, wherein 0.5≤y≤1.

[0017] 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, and ground, and the above-mentioned tableting, sintering, and grinding steps are repeated at least 3 times to obtain single-phase BaCuO2.

[0018] Furthermore, the sintering temperature is 700-1000° C. and the sintering time is 12-96 hours.

[0019] Furthermore, the 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, and ground, and the above-mentioned tableting, sintering, and grinding steps are repeated at least 3 times to obtain single-phase Ca2CuO3.

[0020] Furthermore, the sintering temperature is 800-1100° C., and the sintering time is 12-36 hours.

[0021] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0022] (1) The present invention uses KClO4 as an oxidant, adopts a sandwich structure for assembly, and the mixed powder is wrapped with gold foil to prevent the decomposition product KCl from entering the sample and causing pollution. By accurately adjusting the synthesis condition parameters, a Cu1223 superconductor without a symbiotic phase is prepared;

[0023] (2) The present invention prepares a Cu1223 superconductor without intergrowth phases such as Cu1234 by precisely adjusting the synthesis parameters, providing a high-quality carrier for subsequent research on the performance and application of Cu1223 superconductors. The method of the present invention breaks through the technical difficulties in preparing Cu1223 superconductors by optimizing the process and improving the technology, changing the raw materials, improving the precursor synthesis process, optimizing the stoichiometric ratio and the high-pressure synthesis process.

[0024] 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

[0025] 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.

[0026] Figure 1 This is a crystal structure diagram of the "copper series" copper-based superconductor;

[0027] Figure 2 The copper-oxygen surface diagram of the copper-based superconductor unit cell with different coordination configurations;

[0028] Figure 3 is a schematic diagram of a sandwich structure formed in the present invention;

[0029] Figure 4 This is the X-ray diffraction pattern of the Cu1223 superconductor prepared in Example 1 of the present invention;

[0030] Figure 5 This is a fitting diagram of the X-ray diffraction spectrum of the Cu1223 superconductor prepared in Example 1 of the present invention;

[0031] Figure 6 This is a test diagram of the magnetic susceptibility of the Cu1223 superconductor prepared in Example 1 of the present invention;

[0032] Figure 7 A comparison chart of X-ray diffraction spectra of samples prepared in Comparative Examples 1-6 and Example 1 of the present invention;

[0033] Figure 8 The X-ray diffraction spectrum of the single-phase BaCuO2 prepared in Example 1 of the present invention;

[0034] Fig. 9 The X-ray diffraction spectrum of the single-phase Ca2CuO3 prepared in Example 1 of the present invention;

[0035] Fig.10 These are the standard XRD patterns of Cu1223 superconductor, Cu1245 superconductor and Cu1234 superconductor. DETAILED DESCRIPTION

[0036] 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.

[0037] Another specific embodiment of the present invention discloses a Cu1223 superconductor prepared by the above method, wherein the molecular formula of the Cu1223 superconductor is Cu x Ba2Ca2Cu3O 8+δ , where 0.6≤x≤0.9, 0≤δ≤1.

[0038] In a specific embodiment, the Cu1223 superconductor is synthesized under high pressure using KClO4 as an oxidant and BaCuO2 and Ca2CuO3 as precursors.

[0039] Another specific embodiment of the present invention discloses a method for preparing the above-mentioned Cu1223 superconductor, comprising KClO4 as an oxidant, BaCuO2 and Ca2CuO3 as precursors, and specifically comprising the following steps:

[0040] (1) mixing BaCuO2, Ca2CuO3 and CuO to obtain an initial mixed powder;

[0041] (2) After 1 / 2 weight of KClO4 is loaded into the bottom of the gold cylinder, the initial mixed powder is placed in the middle of the gold cylinder, and the remaining 1 / 2 weight of KClO4 is added to the top of the gold cylinder to form a sandwich structure, and the KClO4 and the initial mixed powder are sealed and isolated with silver foil. Figure 3 As shown;

[0042] (3) The gold cylinder containing the sandwich structure is sealed and subjected to high pressure synthesis to obtain a Cu1223 superconductor.

[0043] The present invention uses KClO4 as an oxidant, assembles the raw material and the oxidant in a sandwich structure, and uses a gold cylinder to seal and wrap, so as to prevent the decomposition product KCl from entering the sample to cause pollution, thereby obtaining a Cu1223 superconductor free of Cu1234 phase and Cu1245 phase.

[0044] In a specific embodiment, in step (1), the molar ratio of BaCuO2, Ca2CuO3 and CuO is 2:1:x, wherein 0.6≤x≤0.9, for example, x is 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9.

[0045] Under ideal ratio of Cu1223 superconductor, one unit cell contains 4 copper atoms. In fact, there are some Cu vacancies in the charge reservoir layer of this material, which makes the content of Cu atoms in the unit cell low. A large number of experiments have shown that when the Cu content of the charge reservoir layer is 0.6-0.9, the prepared sample has high purity and less impurities, so the above ratio is conducive to the preparation of Cu1223 superconductor.

[0046] In a specific embodiment, in step (2), the mass ratio of the mixed powder to KClO4 is 1:y, wherein 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, or 1.

[0047] The valence state of Cu in Cu1245 superconductor, Cu1234 superconductor and Cu1223 superconductor increases gradually under the same doping amount. Therefore, more oxidants are needed when preparing Cu1223 superconductor. 1 mol KClO4 can release 4 mol O by decomposition, so KClO4 is selected as the oxidant, and its ratio is controlled between 0.5-1. When the oxidant is too much or too little, Cu1212 or Cu1234 phase is easily generated.

[0048] In a specific embodiment, in step (3), the pressure of high pressure synthesis is 4.5-5.5 GPa, for example, 4.5 GPa, 4.8 GPa, 5.0 GPa, 5.2 GPa, 5.5 GPa, the temperature is 980-1020°C, for example, 980°C, 990°C, 1000°C, 1010°C, 1020°C, and the reaction time is 10-60 min, for example, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min.

[0049] It should be noted that after a large number of experiments, the inventors found that the use of the above-mentioned high-pressure reaction conditions and parameters can greatly improve the yield of high-pressure synthesis of Cu1223 superconductors, reduce and inhibit the formation of Cu1234 phases during high-pressure synthesis, and is conducive to the preparation of Cu1223 superconductors.

[0050] In a specific embodiment, 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, and ground, and the above-mentioned tableting, sintering, and grinding steps are repeated at least 3 times to obtain single-phase BaCuO2.

[0051] In a preferred embodiment, the sintering temperature is 700-1000°C, for example, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, and the time is 12-96h, for example, 12h, 20h, 30h, 40h, 50h, 60h, 70h, 80h, 90h, 96h.

[0052] In a specific embodiment, the 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, and ground, and the above-mentioned tableting, sintering, and grinding steps are repeated at least 3 times to obtain single-phase Ca2CuO3.

[0053] In a preferred embodiment, the sintering temperature is 800-1100°C, for example, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, and the sintering time is 12-36h, for example, 12h, 16h, 20h, 24h, 28h, 32h, 36h.

[0054] Specifically, through the above-mentioned repeated sintering and pre-pressing into discs, the powder can be fully contacted to participate in the solid phase reaction to obtain single-phase BaCuO2 and single-phase Ca2CuO3. It is more conducive to the subsequent high-pressure synthesis reaction to prepare Cu1223 superconductors without Cu1245 and Cu1234 phases.

[0055] It should be noted that the purity of BaO, CuO and CaO in the present invention is ≥99.9%. In addition, the entire reaction process of the present invention needs to be carried out in an inert atmosphere.

[0056] In a specific embodiment, in step (3), the high-pressure synthesis reaction is carried out in the cavity of a six-sided top press.

[0057] By precisely adjusting the synthesis parameters, a Cu1223 superconductor free of symbiotic phases such as Cu1234 was prepared, providing a high-quality carrier for subsequent research on the performance and application of Cu1223 superconductors.

[0058] The method of the present invention breaks through the technical difficulty of preparing Cu1223 superconductors by optimizing the process and improving the technology, changing the raw materials, improving the precursor synthesis process, optimizing the stoichiometric ratio and the high-pressure synthesis process, and the like.

[0059] It should be noted that the Cu1223 superconductor prepared in the present invention does not contain symbiotic superconducting phases such as Cu1245 and Cu1234.

[0060] The technical solution of the present invention is further explained below in conjunction with specific embodiments:

[0061] Example 1

[0062] A method for preparing a Cu1223 superconductor 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 evenly in a molar ratio of 1:1, pre-pressed into discs to allow the powder particles to fully contact and participate in the solid phase reaction, sintered at 700°C for 96 hours, fully ground, pressed into discs again, and sintered again. This 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 8 As shown;

[0064] (2) In an inert gas argon atmosphere glove box, CaO and CuO were used as raw materials. CaO and CuO were mixed evenly 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, sintered at 800°C for 36 hours, fully ground, pressed into discs again, and sintered again. This sintering was repeated 3 times to obtain single-phase Ca2CuO3. The X-ray diffraction spectrum of single-phase Ca2CuO3 is shown in Fig. 9 As shown;

[0065] (3) In an inert gas argon atmosphere glove box, single-phase BaCuO2, single-phase Ca2CuO3 and CuO are mixed in a molar ratio of 2:1:x, wherein x=0.6, to obtain an initial mixed powder, and the initial mixed powder is sealed and wrapped with gold foil;

[0066] (4) According to the mass ratio of the initial mixed powder to KClO4 being 1:y, where y=1, KClO4 is weighed, 1 / 2 of the weight of KClO4 is loaded into the bottom of the gold tube, the initial mixed powder is put into the middle of the gold tube, and the remaining 1 / 2 of the weight of KClO4 is added to the top of the gold tube to form a sandwich structure, and the KClO4 and the initial mixed powder are sealed and isolated with silver foil;

[0067] (5) The gold cylinder containing the sandwich structure is sealed to ensure that the oxygen released by KClO4 during the reaction does not escape, and the sealed gold cylinder is placed in the cavity of a six-sided top press, and high-pressure synthesis is performed for 10 minutes at a pressure of 4.5 GPa and a temperature of 1020° C. to obtain a Cu1223 superconductor.

[0068] The Cu1223 superconductor prepared in this example was ground into powder and tested for X-ray diffraction. The results are as follows: Figure 4 As shown, the X-ray diffraction spectrum of the Cu1223 superconductor prepared in this embodiment was analyzed and fitted, and the results were as follows Figure 5 The standard XRD patterns of Cu1223 superconductor, Cu1245 superconductor and Cu1234 superconductor are shown in Figure 2. Fig.10 As shown. Figure 5 and 10 It can be seen that the synthesized Cu1223 superconductor does not contain Cu1245 and Cu1234 phases.

[0069] The magnetic properties of the Cu1223 superconductor prepared in this embodiment were tested. Figure 6 As shown, the results show that the superconducting transition temperature is 70 K. No other temperature superconducting transitions were observed in the magnetic test, which indirectly proves that the sample does not contain Cu1234 phase and Cu1223 phase.

[0070] The molecular formula of the Cu1223 superconductor prepared in this embodiment is Cu 0.6 Ba2Ca2Cu3O 8.0 .

[0071] Example 2

[0072] A method for preparing a Cu1223 superconductor comprises the following steps:

[0073] (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, sintered at 800°C for 72h, fully ground, pressed into discs again, and sintered again. The sintering was repeated 3 times to obtain single-phase BaCuO2;

[0074] (2) In an inert gas argon atmosphere glove box, CaO and CuO are used as raw materials. CaO and CuO are mixed evenly in a molar ratio of 2:1, pre-pressed into discs so that the powder particles are fully in contact and participate in the solid phase reaction, sintered at 900°C for 24h, fully ground, pressed into discs again, and sintered again. This sintering process is repeated 3 times to obtain single-phase Ca2CuO3;

[0075] (3) In an inert gas argon atmosphere glove box, single-phase BaCuO2, single-phase Ca2CuO3 and CuO are mixed in a molar ratio of 2:1:x, wherein x=0.7, to obtain an initial mixed powder, and the initial mixed powder is sealed and wrapped with gold foil;

[0076] (4) KClO4 is weighed according to a mass ratio of the initial mixed powder to KClO4 of 1:y, where y=0.8, and 1 / 2 of the weight of KClO4 is loaded into the bottom of the gold tube, and then the initial mixed powder is put into the middle of the gold tube, and the remaining 1 / 2 of the weight of KClO4 is added to the top of the gold tube to form a sandwich structure, and the KClO4 and the initial mixed powder are sealed and isolated with silver foil;

[0077] (5) The gold cylinder containing the sandwich structure is sealed to ensure that the oxygen released by KClO4 during the reaction does not escape, and the sealed gold cylinder is placed in the cavity of a six-sided top press, and high-pressure synthesis is performed for 30 minutes at a pressure of 4.8 GPa and a temperature of 1010° C. to obtain a Cu1223 superconductor.

[0078] The molecular formula of the Cu1223 superconductor prepared in this embodiment is Cu 0.7 Ba2Ca2Cu3O 8.3 .

[0079] The physical image of the Cu1223 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 Cu1223 superconductor prepared in this embodiment is analyzed and fitted, and the results are basically consistent with those in Example 1, indicating that the synthesized Cu1223 superconductor does not contain Cu1245 and Cu1234 phases.

[0080] The magnetic properties of the Cu1223 superconductor prepared in this embodiment are basically consistent with those in Example 1.

[0081] Example 3

[0082] A method for preparing a Cu1223 superconductor comprises the following steps:

[0083] (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, sintered at 900°C for 36 hours, fully ground, pressed into discs again, and sintered again. The sintering was repeated 3 times to obtain single-phase BaCuO2;

[0084] (2) In an inert gas argon atmosphere glove box, CaO and CuO are used as raw materials. CaO and CuO are mixed evenly in a molar ratio of 2:1, pre-pressed into discs so that the powder particles are fully in contact and participate in the solid phase reaction, sintered at 1000°C for 20h, fully ground, pressed into discs again, and sintered again. This sintering is repeated 3 times to obtain single-phase Ca2CuO3;

[0085] (3) In an inert gas argon atmosphere glove box, single-phase BaCuO2, single-phase Ca2CuO3 and CuO are mixed in a molar ratio of 2:1:x, wherein x=0.8, to obtain an initial mixed powder, and the initial mixed powder is sealed and wrapped with gold foil;

[0086] (4) KClO4 is weighed according to a mass ratio of the initial mixed powder to KClO4 of 1:y, where y=0.6, and 1 / 2 of the weight of KClO4 is loaded into the bottom of the gold tube, and then the initial mixed powder is put into the middle of the gold tube, and the remaining 1 / 2 of the weight of KClO4 is added to the top of the gold tube to form a sandwich structure, and the KClO4 and the initial mixed powder are sealed and isolated with silver foil;

[0087] (5) The gold cylinder containing the sandwich structure is sealed to ensure that the oxygen released by KClO4 during the reaction does not escape, and the sealed gold cylinder is placed in the cavity of a six-sided top press, and high-pressure synthesis is performed for 40 minutes at a pressure of 5.0 GPa and a temperature of 1000° C. to obtain a Cu1223 superconductor.

[0088] The molecular formula of the Cu1223 superconductor prepared in this embodiment is Cu 0.8 Ba2Ca2Cu3O 8.6 .

[0089] The physical image of the Cu1223 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 Cu1223 superconductor prepared in this embodiment is analyzed and fitted, and the results are basically consistent with those in Example 1, indicating that the synthesized Cu1223 superconductor does not contain Cu1245 and Cu1234 phases.

[0090] The magnetic properties of the Cu1223 superconductor prepared in this embodiment are basically consistent with those in Example 1.

[0091] Example 4

[0092] A method for preparing a Cu1223 superconductor comprises the following steps:

[0093] (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, sintered at 1000°C for 12h, fully ground, pressed into discs again, and sintered again. The sintering was repeated 3 times to obtain single-phase BaCuO2;

[0094] (2) In an inert gas argon atmosphere glove box, CaO and CuO are used as raw materials. CaO and CuO are mixed evenly in a molar ratio of 2:1, pre-pressed into discs so that the powder particles are fully in contact and participate in the solid phase reaction, sintered at 1100°C for 12 hours, fully ground, pressed into discs again, and sintered again. This sintering process is repeated 3 times to obtain single-phase Ca2CuO3;

[0095] (3) In an inert gas argon atmosphere glove box, single-phase BaCuO2, single-phase Ca2CuO3 and CuO are mixed in a molar ratio of 2:1:x, wherein x=0.9, to obtain an initial mixed powder, and the initial mixed powder is sealed and wrapped with gold foil;

[0096] (4) KClO4 is weighed according to a mass ratio of the initial mixed powder to KClO4 of 1:y, where y=0.5, and 1 / 2 of the weight of KClO4 is loaded into the bottom of the gold tube, and then the initial mixed powder is put into the middle of the gold tube, and the remaining 1 / 2 of the weight of KClO4 is added to the top of the gold tube to form a sandwich structure, and the KClO4 and the initial mixed powder are sealed and isolated with silver foil;

[0097] (5) The gold cylinder containing the sandwich structure is sealed to ensure that the oxygen released by KClO4 during the reaction does not escape, and the sealed gold cylinder is placed in the cavity of a six-sided top press, and high-pressure synthesis is performed for 60 minutes at a pressure of 5.5 GPa and a temperature of 980° C. to obtain a Cu1223 superconductor.

[0098] The molecular formula of the Cu1223 superconductor prepared in this embodiment is Cu 0.9 Ba2Ca2Cu3O 9.0 .

[0099] The physical image of the Cu1223 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 Cu1223 superconductor prepared in this embodiment is analyzed and fitted, and the results are basically consistent with those in Example 1, indicating that the synthesized Cu1223 superconductor does not contain Cu1245 and Cu1234 phases.

[0100] The magnetic properties of the Cu1223 superconductor prepared in this embodiment are basically consistent with those in Example 1.

[0101] Comparative Example 1

[0102] The method for preparing the Cu1223 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.

[0103] Comparative Example 2

[0104] The method for preparing the Cu1223 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.

[0105] Comparative Example 3

[0106] The method for preparing the Cu1223 superconductor in this comparative example is the same as that in Example 1, except that in step (3), x=1.1.

[0107] Comparative Example 4

[0108] The method for preparing the Cu1223 superconductor in this comparative example is the same as that in Example 1, except that in step (4), the pressure is 5.6 GPa and the temperature is 950°C.

[0109] Comparative Example 5

[0110] The method for preparing the Cu1223 superconductor in this comparative example is the same as that in Example 1, except that in step (4), y=1.1.

[0111] Comparative Example 6

[0112] The method for preparing the Cu1223 superconductor in this comparative example is the same as that in Example 1, except that in step (4), 1 / 3 of the weight of KClO4 is first loaded into the bottom of the gold cylinder, and then the initial mixed powder is placed in the middle of the gold cylinder, and the remaining 2 / 3 of the weight of KClO4 is added to the top of the gold cylinder to form a sandwich structure.

[0113] Test Example 1

[0114] The XRD of Cu1223 superconductors prepared in Comparative Examples 1-6 were tested respectively and compared with Example 1. The results are as follows: Figure 7 As shown in the figure, it can be seen that the samples prepared in Comparative Examples 1-6 all contain a large amount of impurity phases (the impurity phases are represented by * in the figure).

[0115] 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 Cu1223 superconductor, characterized in that: The molecular formula of the Cu1223 superconductor is Cu x Ba2Ca2Cu3O 8+δ , where 0.6≤x≤0.9, 0≤δ≤1.

2. A Cu1223 superconductor according to claim 1, characterized in that: The Cu1223 superconductor is synthesized under high pressure by using KClO4 as an oxidant and BaCuO2 and Ca2CuO3 as precursors.

3. A Cu1223 superconductor according to claim 2, characterized in that: The molar ratio of BaCuO2, Ca2CuO3 and CuO is 2:1:x, wherein 0.6≤x≤0.

9.

4. A Cu1223 superconductor according to claim 2, characterized in that: The pressure of high-pressure synthesis is 4.5-5.5 GPa, the temperature is 980-1020°C, and the reaction time is 10-60 min.

5. A method for preparing a Cu1223 superconductor, characterized in that: The method comprises KClO4 as an oxidant and BaCuO2 and Ca2CuO3 as precursors, and specifically comprises the following steps: (1) mixing BaCuO2, Ca2CuO3 and CuO to obtain an initial mixed powder; (2) After 1 / 2 weight of KClO4 is loaded into the bottom of the gold cylinder, the initial mixed powder is put into the middle of the gold cylinder, and the remaining 1 / 2 weight of KClO4 is added to the top of the gold cylinder to form a sandwich structure, and the KClO4 and the initial mixed powder are sealed and isolated with silver foil; (3) The gold cylinder containing the sandwich structure is sealed and subjected to high pressure synthesis to obtain a Cu1223 superconductor.

6. The method for preparing a Cu1223 superconductor according to claim 5, characterized in that: In step (2), the mass ratio of the mixed powder to KClO4 is 1:y, wherein 0.5≤y≤1.

7. The method for preparing a Cu1223 superconductor according to claim 5, characterized in that: 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, and ground, and the above-mentioned tableting, sintering, and grinding steps are repeated at least 3 times to obtain single-phase BaCuO2.

8. The method for preparing a Cu1223 superconductor according to claim 7, characterized in that: The sintering temperature is 700-1000°C and the sintering time is 12-96h.

9. The method for preparing a Cu1223 superconductor according to claim 5, characterized in that: The 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, and ground, and the above-mentioned tableting, sintering, and grinding steps are repeated at least 3 times to obtain single-phase Ca2CuO3.

10. The method for preparing a Cu1223 superconductor according to claim 9, characterized in that: The sintering temperature is 800-1100°C and the sintering time is 12-36h.

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