Superconductor flux pinning without columnar defects.

Abstract

A superconducting article exists that includes a superconducting film having a substrate, one or more buffer layers, and a high temperature superconducting (HTS) layer. The superconducting layer has the chemical composition REBa2Cu3O 7-x where RE is one or more rare earth elements, such as Y, La, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. The superconductor layer is fabricated using photoassisted metalorganic chemical vapor deposition (PAMOCVD) and includes non-superconducting nanoparticles. The nanoparticles are provided substantially in the ab plane and are naturally oriented. The non-superconducting nanoparticles provide flux pinning centers that improve the critical current characteristics of the superconducting film.

Description

[Technical field]

[0001] This application claims priority to and the benefit of U.S. Provisional Patent Application No. 62 / 745,373, filed October 14, 2018, for “High Flux Pinning Superconductor REBCO Wire Without Columnar Pinning Doping,” and U.S. Provisional Patent Application No. 62 / 745,372, filed October 14, 2018, for “High Growth Rate Photo-Assisted MOCVD (PAMOCVD) for Fabrication of Improved Superconductors,” the contents of both of which are incorporated herein by reference in their entireties.

[0002] SUMMARY OF THE DISCLOSURE

[0004] Embodiments of the subject matter disclosed herein generally relate to compositions and structures of fabricated high temperature superconductors that incorporate non-superconducting materials to provide high flux pinning centers, and methods of making the same. [Background technology]

[0003] Since the first discovery of superconductivity in 1911, many superconducting materials have been discovered. In 1986, the first material with superconducting properties at liquid nitrogen temperature (77 K) was determined. This material, YBa2Cu3O 7-x YBCO (YBCO) is one of a group of oxide-based superconductors called high temperature superconductors (HTS). High temperature superconductors offer the possibility of developing superconductor components at higher operating temperatures compared to conventional superconductors that operate at liquid helium temperatures (4.2K). Superconductors that operate at higher temperatures offer the ability to develop superconductor components and products more economically. After the initial discovery of the YBCO superconductor, other superconductors were discovered that have a similar chemical composition but in which Y is replaced by other rare earth elements. This family of superconductors is often referred to as REBCO, where RE can include Y, La, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu.

[0004] The first commercial HTS wires did not use REBCO material for the superconducting medium. 8+y or Bi2Sr2Ca2Cu3O 10+y "First generation HTS" wires, using materials with the chemical composition of REBCO, required the use of large amounts of expensive precious metals, namely silver (Ag), as the containment and stabilization medium. Thus, "second generation HTS (2G)" wires were made using REBCO as the superconducting material. Called coated conductors, these wires use textured metal substrates onto which a textured thin film of REBCO is deposited, providing a more cost-effective method for producing HTS wires with acceptable critical currents at the temperatures and magnetic fields desired for the application.

[0005] There are several methods for the deposition of thin film REBCO in the production of REBCO wires, including metalorganic chemical vapor deposition (MOCVD), pulsed laser deposition (PLD), reactive co-evaporation (RCE), and metalorganic deposition (MOD). Many methods within the category of physical vapor deposition (PVD) techniques generally suffer from low growth rates, high vacuum requirements, continuous source replacement, moderate area coverage, and a limitation to line-of-sight deposition only. Such limitations, especially low growth rates, are problematic for the commercialization of YBCO film technology for HTS wires and tapes. MOCVD overcomes many of these shortcomings and can produce thin and thick YBCO films of high superconducting quality for coated conductor applications.

[0006] MOCVD, first developed in the early 1970s, is now the dominant thin film fabrication technique in the semiconductor-based microelectronics industry. Given the industrial history of MOCVD, the technique has been directly transferred to YBCO film growth and has been shown to produce high quality YBCO samples. The first work on the application of MOCVD to YBCO thin film growth began in the early days of high temperature superconductivity research. While initial efforts yielded peripheral materials, several groups began growing YBCO films through the application of standard microelectronics-developed MOCVD techniques at the time, modified for higher temperatures, oxidizing atmospheres, and lower vapor pressure precursors (Zhang et.al.).

[0007] The higher temperatures (>200 K higher than for semiconductor III-V compounds) required improved reactor designs and improved heaters, and the lower vapor pressure precursors necessitated enhanced attention to precursor vapor flow control and stability. Initial results are promising, with Tc>90 K and Jc>10 for films grown on single crystal oxide substrates. 6 A / cm 2 was realized (Schulte et al.).

[0008] Photoirradiation has also been applied to MOCVD, as organometallic precursors are sensitive to photodissociation. Early work focused on excimer laser irradiation of the reaction in an attempt to increase the precursor dissociation rate (Higashiyama et al.). This only marginally improved the superconducting properties, but there was some improvement in producing surface smoothness and a-axis surface alignment for YBCO growth.

[0009] The basic architecture of all wires is generally based on a similar thin film structure. The superconducting layer in all these wires is typically biaxially textured with the a and b crystallographic axes of REBCO aligned coplanar with the surface of the film and the c axis normal to the surface of the film, as shown in Figure 1. Due to the anisotropy of the superconductor thin film structure, and the inherent anisotropy of the superconducting properties of the REBCO material, the Ic of these wires generally exhibits anisotropic properties.

[0010] With the discovery of high temperature superconductor (HTS) materials, one of the focuses has been on the development of HTS wires for high power electrical applications. Such applications include, but are not limited to, transmission cables, distribution cables, electric motors, generators, electromagnets, fault current limiters, transformers, and energy storage. For HTS wires to be successful as a solution for these high power electrical applications, they need to meet the high power electrical requirements of the various applications while at the same time being low enough cost to meet the commercial requirements of these applications. One of the main electrical properties of interest is the critical current of the HTS wire. The critical current (Ic) is the current at which a superconductor loses its superconducting properties and becomes non-superconducting. The critical current of a superconductor is affected by the temperature and magnetic field to which the superconductor is subjected. The higher the temperature and magnetic field, the lower the critical current. To be able to meet the technical requirements of the various applications, the HTS wire needs to have a sufficiently high critical current at the temperatures and magnetic fields that these applications experience.

[0011] One of the important approaches to increase the critical current capacity of superconductors is by introducing flux pinning materials into the superconductor. At higher magnetic fields, type II superconductors allow magnetic flux to enter quantized packets surrounded by supercurrent vortices. These penetration sites are known as flux tubes. Flux pinning is a phenomenon in which the free motion of flux tubes in type II superconductors is hindered due to interactions with defects in the superconducting material. Flux tubes adjacent to or surrounding such defects have their energy altered and their motion through the superconducting material is hindered. Flux pinning allows the penetration of magnetic field lines into type II superconductors and attempts to take advantage of two critical magnetic fields that limit performance characteristics. The increased anisotropy and decreased current capacity are due to unpinned flux tubes that aid in flux penetration. Therefore, in high-temperature superconductors, flux pinning is desirable to prevent "flux creep", which induces voltage and effective resistance in the conductor and reduces the critical current Ic and critical current density Jc.

[0012] Thus, the inclusion of pinning sites or centers within the superconductor that act as flux pinning centers aids in improving the critical current capacity. Pinning centers are now comprised of specific compositions of non-superconducting material with specific orientations. Such centers may be commonly referred to as pinning sites or centers, flux pinning centers, defects, or defect centers. The presence of these flux pinning centers provides the wire with the ability to improve the critical current even in high magnetic fields.

[0013] As with other superconducting wires, one of the primary objectives is to improve the flux pinning properties and, in turn, the Ic of the REBCO wire. Many processes have been investigated to fabricate REBCO superconducting films that contain nanoparticles as pinning centers to further improve current carrying capacity. The fabrication process of REBCO has been modified to naturally produce non-superconducting impurities such as Y2O3 and Y2BaCuO5 in specific orientations relative to the superconducting layer to improve flux pinning and the corresponding Ic.

[0014] Other materials that are not part of the REBCO group of elements are known to be introduced into the superconductor layer to produce non-superconducting particles. Materials such as BaMO3, where M can be Ti, Zr, Al, Hf, Ir, Sn, Nb, Mo, Ta, Ce, V, are added as doping materials to produce non-superconducting nanoparticles.

[0015] Current methods for achieving flux pinning generally introduce secondary phase particles as pinning materials. For example, U.S. Patent No. 7,737,087 describes the addition of Group 4 or 5 metals with close lattice match to the HTS material, which results in the introduction of strain into the film, thereby inducing dislocations in the REBCO film that result in flux pinning.

[0016] Other methods, described for example in U.S. Patent No. 8,926,868, rely on the creation of specific nanostructures in the HTS layer by high energy bombardment to produce randomly distributed nanoholes that are then used to form nanorods, and U.S. Patent No. 8,119,571 provides self-assembled nanodots and nanorods in the form of preferentially c-axis oriented columns of nanodots and / or nanorods, as shown in FIG.

[0017] This doping of foreign matter combined with a columnar distribution of preferentially c-axis oriented nanoparticles has resulted in REBCO wires with improved performance and increased Ic, especially at high magnetic fields, compared to undoped material. However, the manufacturing methods for producing these nanodots and nanorods are highly complex in order to deposit the doped material in a specific superstructure (e.g., column) and orientation relative to the superconductor layer. The difficulty in achieving the correct preferred orientation of the doping material limits the growth rate of the wire, which adds to the manufacturing time and the associated costs and complexity. It would therefore be highly valuable to develop superconducting articles and manufacturing processes that do not require foreign matter doping or specific oriented growth of nanoparticles, while producing high performance HTS wires that meet the Ic requirements of high power applications, even at high magnetic fields. It is a further objective to produce superconductors that can meet these requirements at high growth rates so that they can be manufactured with commercially attractive economics. Summary of the Invention

[0018] According to an embodiment, there is a thin film composite high temperature superconductor. The superconductor includes a high temperature superconducting layer comprising a substrate; a buffer layer; and a non-superconducting material. The non-superconducting material is distributed along the ab-plane of the superconducting layer.

[0019] According to another embodiment there is a method for forming a high temperature superconductor, the method including providing a substrate; depositing a buffer layer on the substrate; depositing a high temperature superconductor layer on the buffer layer; and co-depositing a non-superconducting material layer, where the non-superconducting material is randomly distributed within the superconductor layer and lacks a substantial vertically oriented component.

[0020] According to yet another embodiment, there is a thin film composite high temperature superconducting article. The superconducting article includes a substrate; a buffer layer; a high temperature superconducting layer with non-superconducting material preferentially distributed along the ab-plane coplanar with the superconducting layer; and a lift factor at 4 K and 20 T of 2 or greater.

[0021] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate one or more embodiments and, together with the description, explain these embodiments. [Brief description of the drawings]

[0022] [Figure 1] 1 shows axes and planes of reference for a high temperature superconducting film. [Diagram 2] 1 shows a prior art superconductor having vertical columns of defects. [Diagram 3] 1 illustrates an exemplary architecture of a high temperature superconductor. [Figure 4] 1 shows a transmission electron microscope image of an exemplary YBCO superconductor material having nanoparticles produced by the method of the present invention. [Diagram 5] 1 shows an X-ray diffraction (XRD) pattern of an exemplary HTS YBCO material of the present invention. [Figure 6A] 1 illustrates different aspects of an exemplary PAMOCVD deposition system. [Figure 6B] 1 illustrates different aspects of an exemplary PAMOCVD deposition system. [Figure 6C] 1 illustrates different aspects of an exemplary PAMOCVD deposition system. [Figure 7]For example, the lift factor performance of HTS wires produced by the presently disclosed methods is shown. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The following description of the embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description is not intended to limit the invention. Instead, the scope of the invention is defined by the appended claims. The following embodiments are discussed for simplicity with respect to high temperature superconductors having Y2O3 non-superconducting centers deposited using photo-assisted MOCVD fabrication techniques. However, the embodiments discussed herein are not limited to such elements.

[0024] References throughout this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the disclosed subject matter. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification do not necessarily refer to the same embodiment. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0025] The REBCO HTS superconductor tape and wire embodiments of the present invention may include nano-sized particles distributed in the ab-plane of the superconducting layer of the wire to provide high Ic at high magnetic fields. In this context, said particles in the ab-plane shall mean in a plane that is coplanar with the superconducting layer (see FIG. 1). The ab-plane may include particles that are completely surrounded by the superconductor layer, or particles that extend above, below, or on top of the upper or lower boundaries defined by the upper and lower thin film boundaries of the superconductor layer, or at multiple locations in the ab-plane.

[0026] Preferred embodiments of the method for producing high Ic wires according to the present disclosure do not require c-axis oriented HTS layers or preferentially vertically aligned columns of nanodots or nanorods, nor do they require preferentially vertically aligned second phases, dopants, or stacking faults as described by the prior art.

[0027] The method embodiments disclosed herein result in non-superconducting nanoparticles that are substantially preferentially distributed along the ab plane in the HTS layer, without any particular vertical or near-vertical alignment. High Ic can be obtained at high magnetic fields and low temperatures using the presently disclosed nanoparticles that are trapped in the ab plane in the HTS layer and do not have a particular vertical (c-axis) orientation. The reduced criticality of the nanoparticle c-axis orientation reduces costs, as the manufacturing process is not limited by the need to orient the crystals or introduce rod-shaped non-superconducting dopants into the process.

[0028] Epitaxial REBCO high temperature superconductor (HTS) wires are processed, in certain preferred embodiments, by using metal-organic chemical vapor deposition (MOCVD) or other suitable deposition processes known in the art of superconductor fabrication. The wires typically have a thin film composite architecture, an example of which is shown in FIG. 3. In this example, the architecture includes a substrate 300, at least one buffer layer (two shown in this example as 310 and 320), at least one superconducting layer (one shown in this example as 330), and at least one capping or stabilization layer 340. Other layers can be readily envisioned by one of ordinary skill in the art and provide additional purposes to the basic architecture described herein.

[0029] The architecture may have a crystallographic orientation in which the a-axis and b-axis are oriented along the surface of the film while the c-axis is oriented perpendicular to the film surface. This crystallographic orientation of the REBCO layer is typically obtained by using an atomically textured substrate 300 consisting of a metal foil with one or more atomically textured buffer layers deposited on the metal.

[0030] The substrate metal 300 is typically in the form of a flexible foil or tape, and is typically constructed from a metal-based alloy, including but not limited to stainless steel alloys and nickel-based metal alloys. The metal-based substrate may have a tape structure with a high relative width and length compared to its thickness. A typical width may be 12 mm, but may exceed 100 mm, and the length may be hundreds of meters or more. This metal substrate 300 may be processed to form a biaxial texture using a rolling assisted biaxially textured substrate (RABiTS) process or other processes known in the art to be suitable for texturing metal substrates.

[0031] In certain preferred embodiments, the metal layer is not textured, e.g., Hastelloy, Inconel, or other alloy, and instead of directly texturing the metal surface, the substrate metal layer 300 may have at least one or more deposited buffer layers 310 and 320 on top of the biaxially textured metal layer 300. Such layers cause the crystallographic axes of the buffers to be aligned in a plane and perpendicular to the surface of the metal layer.

[0032] Deposition-based biaxial texturing of one or more buffer layers can be achieved via ion beam assisted deposition (IBAD), pulsed laser deposition (PLD), or inclined substrate deposition (ISD) or other methods. Biaxially textured films can have a rock salt (halite)-like crystal structure. Biaxial texturing is necessary for proper crystallographic alignment of the REBCO superconductor layer when deposited on the substrate 300 for optimal superconducting performance. The buffer material can be specified to ensure the desired lattice mismatch between the buffer (310, 320) and the REBCO HTS layer 330 to promote the development of nanoparticles, which will be discussed later.

[0033] High temperature superconducting (HTS) layer 330 is typically constructed from HTS materials known in the art that are capable of producing superconducting behavior above 77 K, which corresponds to the temperature of liquid nitrogen. Suitable materials include YBa2Cu3O4, among others. 7-X (YBCO) or BiSr2CaCu2. Y2Ba4Cu7O 14+X Other stoichiometries of YBCO are known, including, but not limited to, YBa2Cu4O8, YBa2Cu4O8, and the like, and are also contemplated by this disclosure and are generally and hereafter referred to as YBCO materials. In other embodiments, other rare earth elements may be substituted for Y, and are generally referred to as materials REBa2Cu3O 7-x (REBCO) family, where RE can include Y, La, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu.

[0034] For second generation (2G) high temperature superconductors (HTS), the flux pinning force is related to the density, size, and dimension of the introduced defects. In a preferred embodiment, the non-superconducting flux pinning particles are randomly distributed within the superconducting layer. The material composition of the non-superconducting flux pinning sites includes, but is not limited to, RE2O3 and BaMO3. For RE2O3, RE may include Y, La, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu. For BaMO3, BaMO3 nanoparticle formation in REBCO requires an additional element of M, where M includes one or more elements of Ti, Zr, Al, Hf, Ir, Sn, Nb, Mo, Ta, Ce, and V.

[0035] FIG. 4 shows a transmission electron microscope image of an exemplary YBCO superconductor 400 material with non-superconducting nanoparticles 410 produced by the method of the present invention. The nanoparticles 410 are distributed along the crystallographic ab-plane 420 instead of the c-axis 430. Note that in this example, the sample was prepared by sectioning the HTS tape, thus exposing the depth (c-axis) of the HTS layer. Given that in certain embodiments the layer can be tens to thousands of nanometers or more thick, multiple sub-planes in the ab-plane may become apparent. In this example, the non-superconducting nanoparticles appear as dark stripes randomly distributed in the ab-plane of the HTS superconductor. Also, in this example, there is no observable substantial orientation or distribution of the non-superconducting particles along the c-axis 430 perpendicular to the ab-plane 420, since the c-axis is off the page.

[0036] 5 shows an X-ray diffraction (XRD) pattern 500 of an exemplary HTS YBCO material of the present invention, showing characteristic diffraction peaks 530 and 540 of high intensity (Y-axis 510) corresponding to the characteristic two-theta (2θ) positions (X-axis 520) of Y2O3 in the YBCO superconductor material 330. The XRD data indicates that the nanoparticles found distributed along the ab-plane 420 are composed of Y2O3 non-superconducting material.

[0037] The size of the non-superconducting flux pinning particles can range up to 100 nm in diameter or more. The RE2O3 nanoparticles are formed in the ab-plane of the REBCO layer without the need for additional elements other than those typically included in the precursor vapor source for growing the REBCO superconducting material. Thus, in a preferred embodiment, the non-superconducting flux pinning particles are co-deposited with the superconducting material without the introduction of foreign matter. The lack of substantial c-axis orientation of the particles is a further feature of the presently disclosed superconducting wire and method of manufacture.

[0038] The formation of these ab-plane distributed nanoparticles can be achieved in certain preferred embodiments using a photoassisted metalorganic chemical vapor deposition (PAMOCVD) process without slowing down the growth rate, as typically occurs with other growth methods that produce preferentially vertically oriented nanoparticles such as those shown in FIG. 6.

[0039] FIG. 6A shows an exemplary PAMOCVD system in which application of UV and visible light provides an energy source to the reaction process to increase the mobility of the incoming atoms to form non-superconducting nanoparticles during deposition and distribution of both non-superconducting and superconducting materials. A UV / visible radiation source 610 is typically enclosed within a low-pressure reaction chamber or vessel 620 maintained at a target pressure by one or more external vacuum pumps 630. The source 610 may be comprised of one or more lamps emitting a desired wavelength or range of wavelengths. The lamps may be positioned adjacent or in close proximity to an inlet showerhead 640 that provides injection of precursors from a supply line 650 for the precursor starting material. The source 610 is typically focused on the growth surface of a moving metal foil substrate 300. Such substrates are generally provided in a reel-to-reel continuous supply system with the substrate passing through a slit 660 in the wall of the reaction vessel 620.

[0040] The REBCO deposition surface in certain preferred embodiments is continuously irradiated with a UV / visible radiation flux from radiation source 610 while the REBCO film is growing, with the radiation striking the tape substrate on which the REBCO film is growing at a substantially normal angle of incidence as shown in FIG. 6B. The normal orientation of the radiation results in the highest radiation density at the surface, since a non-normal radiation configuration results in a lower radiation density. When one or more radiation sources 610 are arranged in a hemispherical pattern around the inlet showerhead 640, the exposure can have both normal and non-zero angle radiation striking the surface, as shown, for example, in FIG. 6C.

[0041] UV / visible radiation at the surface of the growing film energetically excites the surface atoms to increase their surface mobility, thus enabling more rapid attainment of their lowest energy configuration, resulting in a highly crystalline structure in the growing film. It is the highly crystalline structure in the ab plane (i.e., primarily in the plane of the substrate) of REBCO that promotes high current carrying capacity and high performance. Furthermore, the localization of energy facilitating the growth of the REBCO film at the growth surface by supplying energy from above the growing film eliminates the thermal delay associated with supplying energy from below the tape substrate, as when using a typical heated substrate susceptor.

[0042] The UV / visible radiation present at the growth surface of the growing REBCO layer greatly enhances the growth rate of highly textured REBCO. Rates of 1.2 microns per minute (μm / min) and above are possible while maintaining the high performance quality of the REBCO tape. The high growth rates are proposed to be due to physicochemical effects including enhanced surface diffusion of the accreted elements forming the REBCO unit cell on the buffer layer surface. It is important to note that for REBCO films, high performance (high current carrying capacity) is determined primarily by the atomic order of the atoms in the growing REBCO film. Enhanced atomic diffusion by UV / visible radiation as it descends on the growth surface allows the atoms to move more quickly to the lowest energy positions on the surface, thus facilitating the growth of the highly crystalline surface required for high performance REBCO films.

[0043] As described above, direct radiation exposure of the growth surface results in REBCO (e.g., YBCO) films that can be grown at rates of 1.2 μm / min or more and as low as 0.01 μm / min, as desired. The REBCO films are grown with a high degree of texturing, as determined by X-ray diffraction parameters of Δφ between 2° and 7°, and Δω between 1° and 4°, in certain preferred exemplary embodiments. The performance, as measured by the current carrying capacity of the resulting exemplary YBCO wire or tape, can exceed 500 A / cm width or more at 77 K. Such high growth rates enable industrial production of high performance REBCO wires with commercially attractive economics.

[0044] In other preferred embodiments, the flow rates and stoichiometry of the starting precursor materials are controlled to co-produce RE2O3 or BaMO3 nanoparticles within the REBCO film for flux pinning. The growth rate is adjusted by control of the precursor flow rates and source energy input to ensure the proper amount, size, and distribution of nanoparticles. In addition, the stoichiometry of the MOCVD precursor vapor contributes to determining the composition of the secondary phase non-superconducting particles that act as pinning centers. The non-superconducting particles of the present invention can be produced in certain embodiments by adding excess RE precursor or excess Ba and introducing fresh M precursor into the vapor stream.

[0045] In one exemplary embodiment, Y2O3 non-superconducting particles are co-deposited on YBCO as flux pinning centers via PAMOCVD process, resulting in 20 atomic % excess yttrium in the final coating. The deposition growth rate of the HTS material in this example was about 0.2 μm / min on a CeO2 capped IBAD buffer substrate. In another embodiment, YBCO is deposited with 40 atomic % excess yttrium during coating. The deposition growth rate of the HTS material in this example was about 0.25 μm / min on a LaMnO3 capped IBAD buffer substrate.

[0046] As noted above, the density of pinning centers is a key factor in determining performance, and critical current can be limited by a low density of pinning centers. The presently disclosed method allows for tuning of performance by targeting a specific density of pinning centers through control of the process parameters described above. The presently disclosed non-superconducting particles deposited in the ab plane without a specific c-axis orientation at high growth rates allows for significant increases in production speed and cost efficiency.

[0047] As discussed above, YBCO HTS materials with non-superconducting flux pinning centers can be produced by MOCVD from precursor supplies according to the following reactions:

[0048] Y2O3+4BaCO3+6CuO→2YBa2Cu3O 6.5 +4CO2

[0049] Y2O3(XS)+4BaCO3+6CuO→2YBa2Cu3O 6.5 +4CO2+Y2O3

[0050] Known systems for precursor delivery include gas, liquid, solid, and slurry-based approaches. In preferred embodiments using MOCVD, particularly PAMOCVD-based deposition, precursors may be delivered as organometallic compounds, as flash evaporated solids, or as solvated gas-phase molecules using tetrahydrofuran (THF) or other suitable organic solvents.

[0051] The crystal structure of REBCO, in which the CuO2 component in the unit cell may consist of two-dimensional planes adjacent to the RE atoms, also further enhances the formation of non-superconducting nanoparticles (mainly oxide particles) between two CuO2 planes, as they can act as a trapping mechanism for particles in certain embodiments.

[0052] The key performance metric for this wire is achieving high critical currents in wires with HTS layers containing nanoparticles for flux pinning distributed along the ab plane of the HTS layer without any specific perpendicular or near perpendicular alignment. When the magnetic field is perpendicular to the tape surface (H / / c), critical currents of over 450 A per cm width and 0.11 mm HTS tape thickness at 4 K and 19 T can be achieved.

[0053] The following table shows the composition YBa2Cu3O 7-X 1 shows Ic(A) measurements at 4 K for a magnetic field perpendicular to the tape surface according to an embodiment of the invention comprising a superconducting material having a thickness of 1.0 mm. In this embodiment, the tape width is 4 mm, and the corresponding Ic / cm width at 19 T is 463.8 A / cm width. [Table 1]

[0054] The performance of HTS wires in a magnetic field is also often characterized by a measurement commonly referred to as the lift factor. The lift factor is usually defined as the ratio between the critical current at 77K, self-field and the critical current at a distinct temperature and field, such as 4K and 20T. Unlike the critical current, which is an absolute value, the lift factor provides a relative relationship between the two values. Certain exemplary embodiment wires of the present disclosure exhibit lift at 4K, 20T (Ic(4K, 20T) / Ic(77K, self-field)), which corresponds to a lift factor of 2 or greater.

[0055] The ability to maintain high critical current performance at high growth rates is crucial to the commercial viability of HTS products. REBCO superconductor layer thicknesses can be grown at rates of 0.2 μm / min, 1.0 μm / min, 1.2 μm / min, 1.5 μm / min and higher while maintaining critical currents (Ic) of over 450 A / cm width and corresponding Ic of 40,000 A / cm width at 4 K and 20 T. 2 or higher engineering critical current density J EHere, we can maintain a high magnetic flux pinning, which leads to an engineering critical current density J E is defined as the critical current Ic divided by the total cross-sectional area of ​​the HTS layers.

[0056] 7, for example, illustrates the lift factor performance of HTS wires produced by the presently disclosed methods. Lift factor (Y-axis 710) Ic was measured at 4.2K compared to Ic at 77K, self-field, for a range of B-field strengths (X-axis 720) measured in Tesla.

Claims

1. substrate; A buffer layer; and a high temperature superconducting layer including a non-superconducting material; the non-superconducting material is distributed preferentially along the a-b plane coplanar with the high temperature superconducting layer, and randomly within the a-b plane, lacking substantial vertical alignment; Thin film composite high temperature superconducting articles.

2. The superconducting article of claim 1 , wherein the non-superconducting material is comprised of nanoparticles.

3. The superconducting article of claim 1 , wherein the non-superconducting material is amorphous.

4. The non-superconducting material has an RE that includes one or more of the following elements: Y, La, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu. ２ O ３ The superconducting article of claim 1 , comprising:

5. The non-superconducting material is BaMO, where M includes one or more of the following elements: Ti, Zr, Al, Hf, Ir, Sn, Nb, Mo, Ta, Ce, and V. ３ The superconducting article of claim 1 , comprising:

6. 10. The superconducting article of claim 1, wherein the buffer layer and the high temperature superconducting layer are selected to ensure a lattice mismatch between the two layers.

7. 1. A method of forming a high temperature superconductor, comprising: providing a substrate; depositing a buffer layer on the substrate; depositing a high temperature superconducting layer on said buffer layer; and co-depositing a non-superconducting material preferentially distributed along the a-b plane coplanar with the high temperature superconducting layer; A method wherein said non-superconducting material is randomly distributed in said ab plane and lacks substantial vertical alignment.

8. The non-superconducting material has an RE that includes one or more of the following elements: Y, La, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu. ２ O ３ The method of claim 7, comprising:

9. The non-superconducting material is BaMO, where M includes one or more of the following elements: Ti, Zr, Al, Hf, Ir, Sn, Nb, Mo, Ta, Ce, and V. ３ The method of claim 7, comprising:

10. The method of claim 8, wherein the non-superconducting material is deposited by introducing an atomic excess of RE during co-deposition with the high temperature superconducting layer.

11. 10. The method of claim 9, wherein the non-superconducting material is deposited by introducing an atomic excess of Ba and a new element M, where M comprises one or more of the following elements: Ti, Zr, Al, Hf, Ir, Sn, Nb, Mo, Ta, Ce, and V, during co-deposition with the high temperature superconducting layer.

12. 8. The method of claim 7, wherein the buffer layer, the high temperature superconducting layer and the non-superconducting material are deposited by photo-assisted MOCVD (PAMOCVD).

13. 13. The method of claim 12, wherein the growth rate of the high temperature superconducting layer is 1.0 μm / min or greater.

14. substrate; Buffer layer; High-temperature superconducting layer; non-superconducting material distributed preferentially along and randomly within the a-b plane coplanar with said superconducting layer and lacking substantial vertical alignment; and Lift factor at 4K, 20T (Ic(4K, 20T) / Ic(77K, self-field)) of 2 or more; A thin film composite high temperature superconducting article comprising:

15. 15. The superconducting article of claim 14, wherein the lift factor is 3 or greater.

16. 15. The superconducting article of claim 14, further comprising a critical current (Ic) at 4K and 20T of 450 A / cm width or greater.

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