A method for preparing a high-density EuBCO superconducting target by low-rare earth induced liquid phase sintering, the high-density EuBCO superconducting target and application

Abstract

The application discloses a method for preparing a high-density EuBCO superconducting target by low-rare earth induced liquid phase sintering, a high-density EuBCO superconducting target and application. The method is to reduce the Eu proportion in the raw material powder of the EuBCO superconducting target, generate a Ba-Cu-O low-melting-point liquid phase by Eu deficiency induction, and promote sintering densification. The preparation method of the high-density EuBCO superconducting target does not need to add an additional sintering agent, is an in-situ liquid phase sintering method based on rare earth defect induction, and specifically reduces the stoichiometric ratio of Eu to 0.7-0.9 to make the system spontaneously generate a Ba-Cu-O low-melting-point liquid phase at a sintering temperature. The liquid phase is generated by the redistribution of internal elements of the system, does not need to be externally added, and thus does not introduce additional impurities. The existence of the liquid phase can significantly improve the material migration efficiency, fill the inter-particle pores, promote the wetting and connection of the grain boundaries, and inhibit the abnormal growth of the grains.

Description

Technical Field

[0001] This invention relates to the field of high-temperature superconducting material preparation technology, and in particular to a method for preparing high-density EuBCO superconducting targets by low rare earth induced liquid phase sintering, as well as the high-density EuBCO superconducting targets and their applications. Background Technology

[0002] REBCO (rare earth barium copper oxide) high-temperature superconducting materials are known for their high current-carrying capacity in the liquid nitrogen temperature range and their ability to maintain a high critical current density under high magnetic fields. c Its unique advantages have made it the preferred material system for second-generation high-temperature superconducting tapes. Currently, almost all companies producing over 1000 kilometers of high-performance tapes annually use pulsed laser deposition (PLD) technology. The core of PLD technology lies in the high-energy pulsed laser bombarding of the REBCO target to form a plasma plume, which is then deposited on the buffer layer substrate. Therefore, the density, grain size, phase purity, and elemental distribution uniformity of the target directly determine the critical current density J of the superconducting thin film. c Superconducting transition temperature T c and long-term stability.

[0003] Among the many REBCO systems, EuBCO has become the mainstream target material for PLD coating due to its excellent pinning performance and good lattice matching. Currently, commercial EuBCO targets mainly adopt the atmospheric pressure solid-state sintering process, namely, mixing, pressing, and atmospheric pressure high-temperature sintering. Although the equipment is simple, this process has prominent problems such as low density (relative density generally does not exceed 90%), coarse grains (to promote densification, the sintering temperature needs to be increased to above 950℃, resulting in abnormal grain growth), and copper-rich phase segregation (incomplete decomposition of BaCO3 and differences in element diffusion lead to the aggregation of copper-rich phase at grain boundaries).

[0004] To overcome the above problems, existing technologies have tried a variety of improvement strategies. Although hot pressing sintering can significantly increase the density to over 95%, it requires large equipment investment, has high mold costs, and is prone to introducing carbon contamination (carbon content can reach thousands of ppm) that contaminates the superconducting phase. Although powder refining can improve sintering activity, relying solely on powder refining not only makes it difficult to break through the densification limit of atmospheric pressure solid phase sintering, but also makes it difficult to achieve stable batch preparation. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for preparing high-density EuBCO superconducting targets using low-rare-earth-induced liquid-phase sintering. This method prepares high-density EuBCO superconducting targets by reducing the rare-earth content and inducing liquid-phase sintering.

[0006] A further technical problem to be solved by the present invention is to provide a high-density EuBCO superconducting target and its application.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing high-density EuBCO superconducting targets by low rare earth induced liquid phase sintering is disclosed. The method involves reducing the Eu ratio in the raw material powder of the EuBCO superconducting target and utilizing Eu deficiency to induce the generation of a low-melting-point Ba-Cu-O liquid phase, thereby promoting sintering densification.

[0009] The chemical structural formula of the EuBCO superconducting target is Eu. x Ba2Cu3O 7-δ Where 0.7 ≤ x ≤ 0.9. δ is the non-stoichiometric ratio of oxygen, usually 0 ≤ δ ≤ 1.

[0010] The method specifically includes the following steps:

[0011] (1) Ingredients: According to the chemical formula Eu x Ba2Cu3O 7-δ Weigh Eu2O3, BaCO3 and CuO powders, where 0.7 ≤ x ≤ 0.9;

[0012] (2) Mixing and grinding: Mix and grind the weighed powder to obtain a uniformly mixed precursor powder;

[0013] (3) Press molding: Press the precursor powder into a blank;

[0014] (4) Liquid phase sintering: The billet is placed in a sintering furnace and sintered at 850-950℃ for 10-30 hours to generate a low-melting-point Ba-Cu-O liquid phase in situ within the billet, which promotes particle rearrangement and densification.

[0015] (5) Cooling: Cool to room temperature with the furnace to obtain high-density EuBCO superconducting target.

[0016] In step (2), the grinding method can be agate ball milling, high-energy ball milling or mechanical crushing.

[0017] The heating rate for liquid phase sintering is 2-10℃ / min. Liquid phase sintering is carried out at atmospheric pressure.

[0018] The atmosphere for liquid phase sintering is air or flowing oxygen.

[0019] The precursor powder has a particle size of 0.5-15 μm.

[0020] In step (3), the pressing pressure is 50-300 MPa and the holding time is 1-10 minutes.

[0021] A high-density EuBCO superconducting target is prepared by the above-mentioned method of preparing high-density EuBCO superconducting target by low rare earth induced liquid phase sintering; the relative density of the EuBCO superconducting target is ≥90%.

[0022] The above-mentioned high-density EuBCO superconducting target is used in the preparation of high-field superconducting thin films with excellent performance using PLD technology.

[0023] The beneficial effects of this invention are as follows:

[0024] (1) The preparation method of the high-density EuBCO superconducting target of the present invention does not require the addition of external sintering aids. It is based on the in-situ liquid-phase sintering method induced by rare earth defects. Specifically, the stoichiometry of Eu is deliberately reduced to 0.7-0.9 (chemical formula Eu). x Ba2Cu3O 7-δ This allows the system to spontaneously generate a low-melting-point Ba-Cu-O liquid phase at the sintering temperature. This liquid phase is generated by the redistribution of elements within the system and does not require external addition, thus preventing the introduction of additional impurities. The presence of the liquid phase can significantly improve the efficiency of mass migration, fill the pores between particles, promote grain boundary wetting and connection, and inhibit abnormal grain growth.

[0025] (2) The preparation method of the high density EuBCO superconducting target of the present invention can achieve a relative density of the target material exceeding 90% under normal pressure and without the need for hot pressing equipment. It provides a practical and feasible technical path for the preparation of low-cost, high-density, and high-performance EuBCO superconducting targets and is suitable for industrial promotion. Attached Figure Description

[0026] Figure 1 SEM images of the high-density EuBCO superconducting target prepared in Example 1 of the present invention; wherein, Figure 1 (a) shows the surface morphology under a 500x electron microscope; Figure 1 (b) shows the surface morphology under a 2kx electron microscope; Figure 1 (c) shows the surface morphology under a 10kx electron microscope.

[0027] Figure 2 The EDS elemental surface distribution results of the high-density EuBCO superconducting target prepared in Example 1 of the present invention.

[0028] Figure 3 SEM image of the EuBCO superconducting target prepared for comparison under a 500x electron microscope. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0030] Example 1

[0031] A method for preparing high-density EuBCO superconducting targets by low rare-earth induced liquid-phase sintering includes the following steps:

[0032] (1) Ingredients: According to the chemical formula Eu 0.8 Ba2Cu3O 7-δ Weigh out Eu2O3, BaCO3 and CuO powders;

[0033] (2) Mixing and grinding: The weighed raw material powder is placed in an agate ball mill jar and ball milled with anhydrous ethanol as the medium. The ball milling time is 12 hours and the ball milling speed is 300 rpm. After ball milling, the powder is dried and sieved to obtain precursor powder.

[0034] (3) Press molding: Take 20 g of precursor powder and press it into a φ20 mm blank under a pressure of 200 MPa, and hold the pressure for 2 minutes;

[0035] (4) Liquid phase sintering: The billet is placed in a box furnace and heated to 920°C at a heating rate of 5°C / min, and sintered in air atmosphere for 20 hours;

[0036] (5) Cooling: Cool to room temperature with the furnace to obtain high-density EuBCO superconducting target.

[0037] The density of the EuBCO superconducting target prepared in Example 1 was measured to be 6.24 g / cm³. 3 The relative density is 90.4% (based on a theoretical density of 6.9 g / cm³). 3 count).

[0038] Figure 1 SEM images of the high-density EuBCO superconducting target prepared in Example 1 of the present invention; wherein Figure 1 (a) shows the surface morphology under a 500x electron microscope; Figure 1 (b) shows the surface morphology under a 2kx electron microscope; Figure 1 (c) shows the surface morphology under a 10kx electron microscope. Figure 1 The SEM images show that the average grain size is 8.73 μm, the grains are tightly connected, and there are very few pores.

[0039] Figure 2 The EDS elemental surface distribution results of the high-density EuBCO superconducting target prepared in Example 1 of the present invention. Figure 2 The EDS surface distribution in the image shows a uniform distribution of Eu, Ba, Cu, and O elements. The distribution characteristics of Ba and Cu at the grain boundaries indicate the presence of a low-melting-point Ba-Cu-O liquid phase.

[0040] Example 2

[0041] The chemical formula of the EuBCO superconducting target in Example 2 is Eu 0.75 Ba2Cu3O 7-δ The other preparation process is the same as in Example 1.

[0042] The density of the EuBCO superconducting target in Example 2 was measured to be 6.38 g / cm³. 3 The relative density is 92.4%.

[0043] Example 3

[0044] The chemical formula of the EuBCO superconducting target in Example 3 is Eu 0.90 Ba2Cu3O 7-δ The sintering temperature was increased to 940℃, and other conditions were the same as in Example 1.

[0045] The density of the EuBCO superconducting target in Example 3 was measured to be 6.20 g / cm³. 3 The relative density is 90.0%.

[0046] Comparative Example

[0047] According to the chemical formula Eu 1.0 Ba2Cu3O 7-δ The precursor powder was prepared under the same conditions as in Example 1.

[0048] The density of the comparative EuBCO superconducting target was measured to be 5.610 g / cm³. 3 The relative density is 81.3%.

[0049] Figure 3 SEM image of the EuBCO superconducting target prepared for comparison under a 500x electron microscope. From Figure 1 and Figure 3 It can be seen that there are obvious pores in the EuBCO superconducting target prepared in the comparative example.

[0050] This invention achieves a significant increase in target density by reducing the Eu ratio in the raw material powder and utilizing Eu deficiency to induce the formation of a low-melting-point Ba-Cu-O liquid phase, thereby promoting sintering densification. The liquid-phase sintered EuBCO target prepared using this method can achieve a relative density of over 90%, making it suitable for the large-scale preparation of high-performance high-temperature superconducting tapes.

[0051] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention. The above embodiments are provided only for the purpose of describing the present invention and are not intended to limit the present invention. Parts not described in detail in this specification are well-known in the art and are not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims. All equivalent substitutions and modifications made without departing from the spirit and principle of the present invention should be covered within the scope of the present invention.

Claims

1. A method for preparing high-density EuBCO superconducting targets by low rare-earth-induced liquid-phase sintering, characterized in that, This method involves reducing the Eu ratio in the raw material powder of EuBCO superconducting target and utilizing the Eu deficiency to induce the formation of a low-melting-point Ba-Cu-O liquid phase, thereby promoting sintering densification.

2. The method for preparing high-density EuBCO superconducting targets by low rare-earth-induced liquid-phase sintering according to claim 1, characterized in that, The chemical structural formula of EuBCO superconducting target is Eu x Ba2Cu3O 7-δ Where 0.7≤x≤0.

9.

3. The method for preparing high-density EuBCO superconducting targets by low-rare-earth-induced liquid-phase sintering according to claim 2, characterized in that, The method specifically includes the following steps: (1) Ingredients: According to the chemical formula Eu x Ba2Cu3O 7-δ Weigh Eu2O3, BaCO3 and CuO powders, where 0.7 ≤ x ≤ 0.9; (2) Mixing and grinding: Mix and grind the weighed powder to obtain a uniformly mixed precursor powder; (3) Press molding: Press the precursor powder into a blank; (4) Liquid phase sintering: The billet is placed in a sintering furnace and sintered at 850-950℃ for 10-30 hours to generate a low-melting-point Ba-Cu-O liquid phase in situ within the billet, which promotes particle rearrangement and densification. (5) Cooling: Cool to room temperature with the furnace to obtain high-density EuBCO superconducting target.

4. The method for preparing high-density EuBCO superconducting targets by low-rare-earth-induced liquid-phase sintering according to claim 3, characterized in that, The grinding method in step (2) can be agate ball milling, high-energy ball milling or mechanical crushing.

5. The method for preparing high-density EuBCO superconducting targets by low-rare-earth-induced liquid-phase sintering according to claim 3, characterized in that, The heating rate for liquid phase sintering is 2-10℃ / min.

6. The method for preparing high-density EuBCO superconducting targets by low-rare-earth-induced liquid-phase sintering according to claim 3, characterized in that, The atmosphere for liquid phase sintering is air or flowing oxygen.

7. The method for preparing high-density EuBCO superconducting targets by low-rare-earth-induced liquid-phase sintering according to claim 3, characterized in that, The precursor powder has a particle size of 0.5-15 μm.

8. The method for preparing high-density EuBCO superconducting targets by low-rare-earth-induced liquid-phase sintering according to claim 3, characterized in that, In step (3), the pressing pressure is 50-300 MPa, and the holding time is 1-10 minutes.

9. A high-density EuBCO superconducting target, characterized in that, The high-density EuBCO superconducting target was prepared by the method of low rare earth induced liquid phase sintering as described in any one of claims 1 to 8; the relative density of the EuBCO superconducting target is ≥90%.

10. The application of the high-density EuBCO superconducting target as described in claim 9 in the preparation of superconducting thin films with excellent high-field performance using PLD technology.

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