A method for reducing the thickness effect of REBCO coated conductors and REBCO coated conductors

Abstract

This invention discloses a method for reducing the thickness effect of REBCO coated conductors and a REBCO coated conductor, relating to the field of superconducting materials technology. Specifically, the method involves depositing a non-stoichiometric REBCO coating. The REBCO material satisfies the following general formula: RE 1+a Ba 2‑b Cu 3‑c O 7‑x Where RE represents rare earth elements; a, b, and c are composition control parameters. This invention starts from the design of the deposition source material composition and controls the supply of effective components to the growth surface throughout the entire thick film deposition process. This can reduce the compositional evolution and epitaxial degradation caused by the increase in thickness from the source, thereby reducing the thickness effect of the REBCO coating conductor.

Description

Technical Field

[0001] This invention relates to the field of superconducting materials technology, and in particular to a method for reducing the thickness effect of REBCO coated conductors and REBCO coated conductors. Background Technology

[0002] REBCO (REBa2Cu3O) 7-x RE (Rare Earth Element) coated conductor is a high-temperature superconducting wire structure formed by epitaxially growing a REBCO superconducting layer on a flexible metal substrate through a buffer layer. Its typical structure includes: metal substrate / buffer layer / REBCO superconducting layer / protective layer.

[0003] REBCO-coated conductors possess high critical current density, high irreversible magnetic field, and excellent magnetic field performance, making them important for applications in high-field superconducting magnets, controlled nuclear fusion devices, superconducting power transport, and magnetic levitation transportation.

[0004] To improve the engineering critical current of REBCO coated conductors, the thickness of the REBCO superconducting layer needs to be increased. However, a significant thickness effect is prevalent in thick film deposition, meaning that the critical current density per unit thickness gradually decreases as the thickness of the REBCO superconducting layer increases.

[0005] Studies have shown that the thickness effect is caused by factors such as elemental segregation, second phase precipitation, decreased epitaxial quality of thin films, and changes in growth kinetics.

[0006] Traditional solutions mainly include: (1) using multi-layered deposition; and (2) controlling deposition temperature and oxygen pressure. However, these methods mainly improve performance through microstructure control, and their control over the element supply ratio and growth kinetics during deposition remains limited.

[0007] Traditional REBCO coated conductors typically use the stoichiometric composition REBa2Cu3O. 7-x The target material is suitable, but due to the different evaporation behaviors of different elements in the high-temperature deposition environment, the composition evolution during the thick film growth process can easily lead to changes, thus affecting the quality of the superconducting layer.

[0008] Therefore, how to control the growth process of REBCO coated conductor superconducting layers through material composition design, thereby reducing the thickness effect, has become an important research direction in this field. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention provides a method for mitigating the thickness effect of REBCO-coated conductors and a REBCO-coated conductor itself. This method improves the stability of thick film deposition and reduces the thickness effect by employing a non-stoichiometric REBCO deposition source material to regulate the growth kinetics of the superconducting layer.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A method for reducing the conductor thickness effect of REBCO coating, wherein the method for reducing the conductor thickness effect of REBCO coating is specifically to deposit REBCO coating using REBCO material with a non-stoichiometric composition.

[0012] The REBCO material satisfies the following general formula: RE 1+a Ba 2-b Cu 3-c O 7-x ; where RE represents rare earth elements; a, b, and c are composition control parameters.

[0013] Among them, a, b, and c cannot all be 0 at the same time.

[0014] Where 0 ≤ a ≤ 0.40; 0.05 ≤ b ≤ 0.40; 0.10 ≤ c ≤ 0.80.

[0015] The RE element is selected from one or more of Y, Sm, Eu, Gd, Nd, and Yb.

[0016] The deposition methods include pulsed laser deposition (PLD), metal-organic chemical vapor deposition, or chemical solution deposition.

[0017] Preferably, when pulsed laser deposition is used, the deposition temperature is 850–1050℃, the oxygen partial pressure is 1–100 Pa, and the laser energy density is 0.5–5 J / cm².

[0018] The deposition source material of the REBCO-coated conductor also contains a BaMO3 pinned phase, wherein M is selected from at least one of Hf, Zr, Sn, and Ti, and the amount of BaMO3 pinned phase added is 0.5–15 mol% of the REBCO material. That is, the deposition source material of the REBCO-coated conductor includes a non-stoichiometric REBCO material and a BaMO3 pinned phase.

[0019] A REBCO-coated conductor includes a metal substrate, a buffer layer, and a REBCO coating. The REBCO coating is prepared using the method described above for reducing the thickness effect of the REBCO-coated conductor. The REBCO coating exhibits RE... 1+a Ba 2-b Cu 3- c O 7-x The components of the representation.

[0020] The thickness effect of the REBCO coated conductor is reduced.

[0021] The surface morphology of the REBCO coating is stepped.

[0022] The beneficial effects of this invention are as follows:

[0023] (1) This invention, starting from the design of the deposition source material composition, regulates the supply of effective components to the growth surface throughout the entire thick film deposition process. This can reduce the compositional evolution and epitaxial degradation caused by the increase in thickness from the source, thereby reducing the thickness effect of the REBCO coating conductor. The non-stoichiometric composition design of this invention does not require the final deposited film to reach the ideal REBa2Cu3O. 7-x Instead of relying on pre-defined compositions, this method utilizes deviations from the actual composition to adjust the growth kinetics, thus better reflecting the real growth behavior of thick film deposition processes.

[0024] (2) The present invention further employs RE-enriched, Ba-deficient and Cu-deficient deposition source materials, which can suppress performance degradation in the thickness direction and improve the stability of thick film deposition.

[0025] (3) The method of the present invention is simple and easy to implement.

[0026] (4) The method of the present invention is applicable to a variety of REBCO coated conductor systems. The present invention is compatible with existing artificial pinned phase design, buffer layer epitaxy technology and continuous winding fabrication process, and is suitable for the engineering fabrication of REBCO coated conductors. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the critical current density variation curve of the REBCO coated conductor obtained in Example 1 of the present invention.

[0028] Figure 2 This is a schematic diagram of the critical current density variation curves of the REBCO coated conductors obtained in Example 1 and Comparative Example 1 of the present invention.

[0029] Figure 3 This is a schematic diagram of the critical current density variation curves of the REBCO coated conductors obtained in Example 2 and Comparative Example 2 of the present invention.

[0030] Figure 4 This is a schematic diagram of the critical current density variation curves of the REBCO coated conductors obtained in Example 3 and Comparative Example 3 of the present invention.

[0031] Figure 5 This is a microstructure image of a REBCO-coated conductor with a thickness of 4 μm obtained in Example 1 of the present invention. Detailed Implementation

[0032] 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.

[0033] The inventors discovered that in actual thick film deposition processes, plume transport, surface reevaporation, elemental segregation, and the tendency for second-phase formation are not simply equivalent to the final film approximating an ideal stoichiometric composition. In other words, reducing the thickness effect does not require the final deposited film to be close to the ideal REBa2Cu3O. 7-x The composition is important, but more importantly, it is crucial to maintain a component supply state and growth window stability that are conducive to continuous epitaxial growth during the process of increasing thickness.

[0034] A method for mitigating the conductor thickness effect of REBCO coatings includes: depositing a REBCO superconducting layer on the surface of a substrate having a buffer layer using a non-stoichiometric REBCO deposition source material; wherein the non-stoichiometric composition satisfies the general formula RE 1+a Ba 2-b Cu 3-c O 7-x Where RE represents rare earth elements, and a, b, and c are composition control parameters, and at least one of a, b, and c is not 0. Preferably, 0 ≤ a ≤ 0.40, 0.05 ≤ b ≤ 0.40, and 0.10 ≤ c ≤ 0.80.

[0035] Preferably, the RE is selected from one or more of Y, Sm, Eu, Gd, Nd, and Yb. More preferably, the non-stoichiometric composition adopts a combination of RE enrichment, Ba deficiency, and Cu deficiency.

[0036] Preferably, the deposition source material is any one of a target material, an evaporation source material, or a chemical solution precursor; the deposition method is any one of pulsed laser deposition (PLD), metal-organic chemical vapor deposition (MOCVD), or chemical solution deposition (CSD).

[0037] Preferably, when using the PLD method, the deposition temperature is 850–1050℃, the oxygen partial pressure is 1–100 Pa, and the laser energy density is 0.5–5 J / cm³. 2 The above parameter range is used to ensure the feasibility of continuous epitaxial growth of REBCO thick films. The specific optimal parameters can be adjusted according to the target composition, equipment structure, and target thickness.

[0038] Preferably, a BaMO3-type pinning phase may be further added to the deposition source material, wherein M is selected from at least one of Hf, Zr, Sn, and Ti. The amount of the BaMO3-type pinning phase added is preferably 0.5–15 mol%, where mol% is a percentage relative to the amount of REBCO matrix material.

[0039] The present invention also provides a REBCO-coated conductor, which includes a metal substrate, a buffer layer and a REBCO coating, wherein the REBCO coating is prepared by the above method.

[0040] Example 1:

[0041] This embodiment prepares a REBCO-coated conductor. The metal substrate is a Hastelloy substrate, and the buffer layer is an IBAD-MgO buffer layer structure.

[0042] The REBCO coating is deposited using PLD deposition (pulsed laser deposition).

[0043] The target material used for deposition is Eu. 1.1 Ba 1.9 Cu 2.6 O 7-x +3.5mol% BHO, where “3.5mol% BHO” means that the amount of BaHfO3 added is 3.5mol% relative to the amount of REBCO matrix material.

[0044] Deposition conditions: Deposition temperature: 880 ℃; oxygen partial pressure: 20 Pa; laser energy density: 2 J / cm²; deposition thicknesses were 1 μm, 2 μm, 3 μm, 4 μm and 5 μm, respectively.

[0045] The specific process of REBCO coating deposition for the REBCO coated conductor in this embodiment of the invention is as follows: First, the metal substrate with a buffer layer is preheated; then, laser ablation is initiated under a set oxygen partial pressure, so that the plasma plume acts on the surface of the buffer layer to deposit and form a REBCO superconducting layer; after the target thickness is reached, the deposition is stopped, and subsequent cooling and oxidation treatments are performed to obtain a REBCO coated conductor sample.

[0046] Comparative Example 1:

[0047] The target material EuBa2Cu3O is composed using traditional stoichiometry. 7-x REBCO coatings with thicknesses of 1 μm, 2 μm, 3 μm, 4 μm, and 5 μm were prepared using 3.5 mol% BHO and the same deposition conditions as in Example 1.

[0048] Figure 1This is a schematic diagram of the critical current density variation curve of the REBCO-coated conductor obtained in Example 1 of the present invention. From... Figure 1 It can be seen that the deposition thickness has little effect on the critical current density Jc, indicating that the REBCO coated conductor prepared by the method of the present invention has a good epitaxial structure and exhibits a weak thickness effect.

[0049] Figure 2 This is a schematic diagram showing the critical current density variation curves of the REBCO-coated conductor obtained in Example 1 of the present invention and the REBCO-coated conductor obtained by the conventional method in Comparative Example 1. From... Figure 2 As can be seen, the critical current density of the comparative model decreases significantly with increasing thickness. In contrast, the coating conductor prepared by the method of this invention exhibits a significantly reduced thickness effect.

[0050] Figure 5 This is a microstructure image of a REBCO-coated conductor with a thickness of 4 μm obtained in Example 1 of the present invention. From... Figure 5 As can be seen, the surface of the REBCO coated conductor obtained in this embodiment has a stepped structure.

[0051] Example 2:

[0052] In this embodiment, Eu is used. 1.2 Ba 1.85 Cu 2.7 O 7-x REBCO coatings with thicknesses of 1 μm, 3 μm, and 5 μm were prepared using +4 mol% BHO as the non-stoichiometric REBCO deposition source material. The remaining substrate structure and deposition process were the same as in Example 1.

[0053] Comparative Example 2:

[0054] The target material EuBa2Cu3O is composed using traditional stoichiometry. 7-x REBCO coatings with thicknesses of 1 μm, 3 μm, and 5 μm were prepared using +4 mol% BHO and the same deposition conditions as in Example 1.

[0055] Figure 3 This is a schematic diagram showing the critical current density variation curves of the REBCO-coated conductors obtained in Example 2 and Comparative Example 2. Similarly, from... Figure 3 It can be seen that the coating conductor prepared by the method of the present invention has a significantly reduced thickness effect.

[0056] Example 3:

[0057] In this embodiment, Gd is used 1.10 Ba 1.90 Cu 2.70 O 7-xREBCO coatings with thicknesses of 1 μm, 2 μm, and 3 μm were prepared using 3 mol% BHO as the non-stoichiometric REBCO deposition source material, with the remaining conditions being the same as in Example 1.

[0058] Comparative Example 3:

[0059] GdBa2Cu3O target material with conventional stoichiometric composition 7-x REBCO coatings with thicknesses of 1 μm, 2 μm, and 3 μm were prepared using +3 mol% BHO and the same deposition conditions as in Example 1.

[0060] Figure 4 This is a schematic diagram showing the critical current density variation curves of the REBCO-coated conductors obtained in Example 3 and Comparative Example 3. Similarly, from... Figure 4 It can be seen that the coating conductor prepared by the method of the present invention has a significantly reduced thickness effect.

[0061] The above embodiments illustrate that the present invention is not limited to a single combination of Eu, Ba, and Cu deviation parameters. As long as the composition design principles described in this invention are met, they can all be used to reduce the thickness effect. Furthermore, this invention is applicable to REBCO coated conductors with different rare earth element systems.

[0062] 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 reducing the conductor thickness effect of REBCO coating, characterized in that, The method for reducing the conductor thickness effect of the REBCO coating is specifically to deposit the REBCO coating using a REBCO material with a non-stoichiometric composition.

2. The method for reducing the conductor thickness effect of REBCO coating according to claim 1, characterized in that, The REBCO material satisfies the following general formula: RE 1+a Ba 2-b Cu 3-c O 7-x ; Where RE represents rare earth elements; a, b, and c are composition control parameters, and a, b, and c cannot all be 0 at the same time.

3. The method for reducing the conductor thickness effect of REBCO coating according to claim 2, characterized in that, 0 ≤ a ≤ 0.40; 0.05 ≤ b ≤ 0.40; 0.10 ≤ c ≤ 0.

80.

4. The method for reducing the conductor thickness effect of REBCO coating according to claim 2, characterized in that, RE elements are selected from one or more of Y, Sm, Eu, Gd, Nd, and Yb.

5. The method for reducing the conductor thickness effect of REBCO coating according to claim 1, characterized in that, The deposition methods include pulsed laser deposition, metal-organic chemical vapor deposition, or chemical solution deposition.

6. The method for reducing the conductor thickness effect of REBCO coating according to claim 5, characterized in that, When pulsed laser deposition is used, the deposition temperature is 850–1050℃, the oxygen partial pressure is 1–100 Pa, and the laser energy density is 0.5–5 J / cm².

7. The method for reducing the conductor thickness effect of REBCO coating according to claim 1, characterized in that, The deposition source material of the REBCO coated conductor also contains a BaMO3 pinning phase, wherein M is selected from at least one of Hf, Zr, Sn, and Ti, and the amount of BaMO3 pinning phase added is 0.5 to 15 mol of REBCO material.

8. A REBCO-coated conductor, characterized in that, The product comprises a metal substrate, a buffer layer, and a REBCO coating, wherein the REBCO coating is prepared using the method for reducing the conductor thickness effect of the REBCO coating as described in any one of claims 1 to 7, and the REBCO coating has RE... 1+a Ba 2-b Cu 3-c O 7-x The components of the representation.

9. The REBCO-coated conductor according to claim 8, characterized in that, The thickness effect of the REBCO coated conductor is reduced.

10. The REBCO-coated conductor according to claim 8, characterized in that, The surface morphology of the REBCO coating is stepped.

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