REBCO (RE = rare earth) based high temperature superconducting (HTS) wires are now being utilized for the development of electric and electromagnetic devices for various industrial, scientific and medical applications. In the last several years, the increasing efforts in using the so-called second generation (2G) HTS wires for some of the applications require a further increase in their engineering current density (Je). The applications are those typically related to high magnetic fields where the higher Je of a REBCO wire, in addition to its higher irreversibility fields and higher mechanical strength, is already a major advantage over other superconducting wires. An effective way to increase the Je is to decrease the total thickness of a wire, for which using a thinner substrate becomes an obvious and attractive approach. By using our IBAD-MOCVD (ion beam assisted deposition-metal organic chemical vapor deposition) technology we have successfully made 2G HTS wires using a Hastelloy® C276 substrate that is only 30 μm in thickness. By using this thinner substrate instead of the typical 50 μm thick substrate and with a same critical current (Ic), the Je of a wire can be increased by 30% to 45% depending on the copper stabilizer thickness. In this paper, we report the fabrication and characterization of the 2G HTS wires made on the 30 μm thick Hastelloy® C276 substrate. It was shown that with the optimization in the processing protocol, the surface of the thinner Hastelloy® C276 substrate can be readily electropolished to the quality needed for the deposition of the buffer stack. Same in the architecture as that on the standard 50 μm thick substrate, the buffer stack made on the 30 μm thick substrate showed an in-plane texture with a Δϕ of around 6.7° in the LaMnO3 cap layer. Low-temperature in-field transport measurement results suggest that the wires on the thinner substrate had achieved equivalent superconducting performance, most importantly the Ic, as those on the 50 μm thick substrate. It is expected the 2G HTS wires made on the 30 μm thick Hastelloy® C276 substrate, the thinnest and with the highest Je to date, will greatly benefit such applications as high field magnets and high current cables.

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2018). Two level undercut-profile substrate-based filamentary coated conductors produced using metal organic chemical vapor deposition. I E E E Transactions on Applied Superconductivity, 28(4), [6601705]. https://doi.Abstract-The two level undercut-profile substrate (2LUPS) has been introduced as a concept for subdividing rare-earth-Ba2Cu3O7 coated conductors (CC) into narrow filaments that effectively reduces the AC losses and improves field stability for DC magnets. The 2LUPS consists of two levels of plateaus connected by a wall with an undercut-profile, which enables a physical separation of the superconducting layer between the plateaus without reducing the effective width of the superconducting layer.In this study we report for the first time the results of fabrication and characterization of a filamentary CC produced in an industrial setup by SuperPower Inc. using ion beam assisted deposition and metal organic chemical vapor deposition (IBAD-MOCVD) on a 2LUPS realized at the Technical University of Denmark (DTU), whereas previous studies discussed the fabrication using alternating beam assisted deposition and pulsed laser deposition (ABAD-PLD).We also present Hall probe scanning measurements performed using a standard THEVA TAPESTAR™ XL machine that is routinely employed for industrial critical current characterization of long length CCs. From these results is it clear that additional analysis of the measured field profiles are required when characterizing filamentary 2LUPS CC using a standard TAPESTAR™ setting. Using a model representation of the 2LUPS we calculated the expected magnetization response by means of finite element methods simulations and we find a good agreement with the experimentally observed magnetic profiles.  Index Terms-Multifilamentary superconductors, Hightemperature superconductors, Magnetic variables measurement, Finite element analysis.

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As an alternative to the introduction of flux pinning centers in RE-Ba-Cu-O (REBCO, RE = rare earth) films by the self-assembly process, we have explored prefabrication of metal nanorods on biaxially-textured templates on flexible substrates followed by REBCO film deposition. This approach provides an opportunity to control nanorod features such as size, shape, density, and orientation, which are difficult to achieve using self-assembly of nanoscale defects during in-situ growth. Successful growth of various metal nanorods such as Ni and Co on biaxially-textured substrates has been accomplished using high-energy ion bombardment of polycarbonate films for template formation followed by metal electrodeposition and polycarbonate removal. Ni nanorods of length up to 2 μm, diameter as small as 10-20 nm, variable orientation and density as high as 5 × 1010/cm2have been grown successfully on biaxially textured templates on flexible metal substrates. In order to provide a suitable interface between the metal nanorods and the subsequently deposited REBCO film, a strontium titanate (SrTiO3) film was deposited to the nanorods by solution spin coating, which was also (200) textured on the substrate surface.

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Single-crystalline-like germanium films have been demonstrated on flexible metal substrates. Using MgO templates made by ion beam assisted deposition (IBAD), germanium films with grain-to-grain misorientation as small as 1° have been demonstrated. The out-of-plane texture of the germanium film has been found to be sensitive to the intermediate buffer layers used in the architecture. Germanium films are grown epitaxially on CeO2 films which are deposited on the MgO templates without or with intermediate layers such as LaMnO3 and SrTiO3. It is found that the strongest preferred (400) orientation of Ge is achieved with SrTiO3 intermediate layer. Additionally, the highest hall mobility in the singlecrystalline-like germanium has been achieved in architectures with SrTiO3 intermediate layer.Hall mobility values of the germanium film are found to increase with film thickness and reach as high as 518 cm 2 /Vs. Cross sectional transmission electron microscopy (TEM) images of thick germanium films on IBAD templates show a high density of defects near the CeO2 interface and a decrease in defect density in the mid and top part of the film.