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The role of diethanolamine (DEA) as a chelating agent was investigated in a fluorine-free precursor solution for the growth of superconducting YBa2Cu3O7 (YBCO) thin films via chemical solution deposition. Infrared spectroscopy and thermal analyses were employed to elucidate the interactions between the chelating agent and propionate-based coating solution. The physical properties of the as-obtained YBCO films were investigated to assess the effect of DEA addition on film growth. Special emphasis was placed on the determination of superconducting transport properties. These have been investigated in wide magnetic field (0-18 T) and temperature (4.5-77 K) ranges to account for various possible application scenarios. The 100 nm thick YBCO film deposited on a (001) SrTiO3 single-crystal substrate exhibited a critical current density of 4 MA cm-2 at 77 K in self-field., This work was carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom program 2014–2018 and 2019–2020 under Grant Agreement No. 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. A D acknowledges the financial support of the 'Entrepreneurial skills and research excellence in doctoral and postdoctoral programs -ANTREDOC'—POCU/380/6/13/123927 project. M N and T P Jr acknowledge the financial support of a grant of the Romanian Ministry of Education and Research, CNCS-UEFISCDI, project number PN-III-P1-1.1-TE-2021-1777, within PNCDI III., With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).

YBa2Cu3O7−x (YBCO) nanocomposites for wire applications need to operate in a broad range of frequencies, ranging from dc in magnets to GHz in cavities and screenings of future particle accelerators. We have investigated the in-field and angular vortex pinning performance in dc and at 50 GHz of two types of nanocomposites, pulsed laser deposition (PLD) YBCO with mixed Ba2YNbO6 + Ba2YTaO6 (BYNTO) nanorods and chemical solution deposited (CSD) YBCO with BaHfO3 (BHO) nanoparticles (NPs), and the pristine counterpart films, grown on top of single-crystalline substrates. Transport measurements performed up to 9 T between 5 and 77 K show that CSD nanocomposites exhibit a smooth field decay and increased single-to-collective crossover field H* compared to pristine samples, associated to the enhanced isotropic pinning contribution induced by the NPs, while PLD films exhibit unchanged H* and superior critical current densities up to higher irreversibility fields, associated to the anisotropic contribution introduced by the rods. Microwave in-field measurements of the pinning constant kp revealed CSD NCs exhibit a qualitatively similar, but smoother kp(H) than pristine samples, whereas for PLD samples, a growing kp(H) dependence is observed as a result of the increased relevance of the stiffness of the fluxons pinned by nanorods., This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom Research and Training Programme 2014–2018 and 2019–2020 under grant agreement No 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. We acknowledge financial support from Spanish Ministry of Economy and Competitiveness through the Severo Ochoa Programme for Centres of Excellence in R&D (SEV-2015-0496), SUMATE project RTI2018-095853-B-C21, cofinanced by the European Regional Development Fund, COST-Nanocohybri CA16218, DWARFS project (MAT2017-83468-R) and Catalan Government with 2017-SGR-1519 and XRE4S.

Cable-in-conduit conductors comprised of twisted stacks of high-temperature superconducting (HTS) tapes constitute a very promising technology by virtue of their easy manufacturing process, flexibility capabilities, and high current densities. In a cable, the current distribution among tapes is one of the key parameters affecting the cable performances. The distribution of current is affected mainly by the self-field configuration (ultimately related to the cable layout) and the termination resistances. In this paper we present a 2D finite element (FE) model, based on the T-A formulation, which computes the magnetic field and current distribution in stacked tapes. This model has been used to describe the experimental V–I results obtained in cables in which different current distributions among tapes are expected. The first case refers to V–I curves of stacks of HTS tapes inserted into ducts formed in the extruded aluminium cylindrical core for a straight cable. The excellent agreement between the experimental findings and the simulation results can be explained in terms of uniform current distribution within the tapes stack, up to the superconducting to normal transition. The second sample, an Al-slotted core Cable-In-Conduit-Conductor, has been bent down to a radius of 0.15 m, and from the measured V–I characteristic of each individual tape, a different tape degradation depending on the tape position within the stack was recorded. The model is able to reconstruct the V–I of the stacks from the characteristic curves of the individual tapes with a satisfactory agreement. The finite element analysis reveals non-uniform current distribution among the tapes, which could expose the cable to a potentially irreversible damage during operation. The proposed FE model constitutes a useful tool for the analysis and predictions of HTS CIC conductor performances and represents a suitable basis for the implementation of more complex models aimed at the design of specific and large applications of this conductor in the next future.

In this paper we study the feasibility of Fe(Se, Te) coated conductors on a simple rolling-assisted biaxially textured substrate (RABiTS) template. Starting from commercially available Ni-5 at% W tapes which show an out-of-plane orientation of about 7° and an in-plane orientation around 5°, we realized a RABiTS template for Fe(Se, Te) coated conductor fabrication by depositing CeO2 thin films on the metallic tape. The oxide buffer layers, deposited via pulsed laser ablation, exhibit an out-of-plane and an in-plane orientation suitable for Fe(Se, Te) deposition and act as a chemical barrier against Ni diffusion. Fe(Se, Te) thin films deposited on such a simple template show a superconducting transition at 16 K and very high upper critical field values with a ΔT c,0 of only 3 K in 18 T. The transport critical current reaches values of 1.7 × 105 A cm-2 at 4.2 K in self-field and is reduced by less than one order of magnitude up to 18 T, remaining isotropic with respect to the magnetic field direction.

The critical current density Jc as a function of the temperature T, magnetic field intensity H and angle ? between the direction of applied magnetic field and the c-axis of the samples was measured on epitaxial 10?at.% Ca-substituted YBa2Cu3O7?? (YCBCO) thin films grown by the pulsed laser deposition technique on (001)-SrTiO3 (STO) and CeO2 buffered r-cut Al2O3 (CAO) substrates. Films exhibited comparable values of critical temperature (Tc~78?K) while higher self-field Jc values for SrTiO3 were observed. Dissipation regimes related to growth boundary and intra-grain pinning mechanisms showed a qualitatively similar contribution for YCBCO films deposited on both substrates when the applied magnetic field direction is parallel to the c-axis (? = 0?). However, a weaker efficiency of pinning related to growth boundaries as well as a wider field range where this dissipation mechanism is active were observed for films grown on CeO2-buffered sapphire. These films exhibited a broad peak centred at ? = 0? in the Jc versus angle behaviour, not observed using a SrTiO3 substrate. The analysis of the Jc(H) dependences collected at ? = 90? revealed that this feature can be partially ascribed to a dramatic decrease of the intrinsic pinning efficiency.

The realization of YBCO-based coated conductors with high critical current density involves the deposition of highly biaxially textured YBCO films. The use of epitaxial growth shifts this requirement to the template used for YBCO deposition. In the rolling-assisted biaxially textured substrate (RABiTS) approach, an appropriately oriented template is provided by a cube-textured substrate. The development of a cube texture is the result of recrystallization occurring in a heavily deformed tape, which is activated by high-temperature annealing. In the case of Ni-based alloys, thermal treatment at temperatures ranging from 900 to 1150??C for at least 30?min is commonly used. The determination of the minimum conditions for thermal treatments in terms of temperature?time involved in the recrystallization process is therefore of practical interest. In this work, Ni?5 at.% W alloy has been studied as a substrate for YBCO-coated conductors. 100??m thick tapes have been obtained through heavy cold rolling, followed by annealing in high vacuum. Different thermal treatments with rates of 20??C?min?1 have been performed in order to study the formation and the evolution of the cube texture. Moreover, the annealing time has been varied in order to inspect the thermal stability of the substrate microstructure at the relatively high deposition temperature of YBCO films. It is found that the substrate begins recrystallizing at 700??C and that the cube texture is fully developed at temperatures higher than 800??C, while annealing at 900??C for 1?h produces a stable microstructure at the typical YBCO deposition conditions.

Pd films were deposited on rolling assisted biaxially textured substrate (RABiTS) Ni?5?at.% W in order to exploit the Pd effect of the texture sharpening with respect to that of the substrate, for the development of YBa2Cu3O7?x (YBCO) coated conductors. The Pd sharpening effect was relevant in the out-of-plane direction where the reduction for the ?-scans' full width at half maximum (FWHM) ranged from 55 to 65%, depending on the substrate roughness. The obtained minimum values of the FWHM in the transverse rolling direction of the (002) Pd ?-scan and in the (111) Pd -scan were of about 2.5? and 5?, respectively. The CeO2/YSZ/CeO2 (YSZ is Y2O3-stabilised ZrO2) heterostructure of the buffer layer was developed by pulsed laser deposition (PLD). In order to transfer the sharp orientation of the Pd film, both the seed CeO2 layer and the YSZ layer were deposited at low temperatures (450??C), low enough to avoid Pd/Ni?W interdiffusion. The YBCO, films deposited by both PLD and metal-organic deposition (MOD) using metal trifluoroacetate acid (TFA), exhibited rolling direction (005) ?-scan and the (113) -scan FWHM values of about 2? and 5?, respectively. In spite of the complete interdiffusion between Ni and Pd during the YBCO film deposition, the coated conductors exhibit good adherence, as well as a smooth and crack-free surface. A zero-resistance critical temperature (TC0) of 90.8?K for the MOD-TFA YBCO films and critical current-density (JC) up to 2.2?MA?cm?2 at 77?K and self-field for PLD YBCO films have been obtained.

The structural and transport properties of YBa2Cu3O7-x films grown by pulsed laser deposition with mixed 2.5 mol% Ba2YTaO6 (BYTO) and 2.5 mol% Ba2YNbO6 (BYNO) double-perovskite secondary phases are investigated in an extended film growth rate, R = 0.02-1.8 nm s-1. The effect of R on the film microstructure analyzed by TEM techniques shows an evolution from sparse and straight to denser, thinner and splayed continuous columns, with mixed BYNO + BYTO (BYNTO) composition, as R increases from 0.02 nm s-1 to 1.2 nm s-1. This microstructure results in very efficient flux pinning at 77 K, leading to a remarkable improvement in the critical current density (J c) behaviour, with the maximum pinning force density F p(Max) = 13.5 GN m-3 and the irreversibility field in excess of 11 T. In this range, the magnetic field values at which the F p is maximized varies from 1 T to 5 T, being related to the BYNTO columnar density. The film deposited when R = 0.3 nm s-1 exhibits the best performances over the whole temperature and magnetic field ranges, achieving F p(Max) = 900 GN m-3 at 10 K and 12 T. At higher rates, R > 1.2 nm s-1, BYNTO columns show a meandering nature and are prone to form short nanorods. In addition, in the YBCO film matrix a more disordered structure with a high density of short stacking faults is observed. From the analysis of the F p(H, T) curves it emerges that in films deposited at the high R limit, the vortex pinning is no longer dominated by BYNTO columnar defects, but by a new mechanism showing the typical temperature scaling law. Even though this microstructure produces a limited improvement at 77 K, it exhibits a strong J c improvement at lower temperature with F p = 700 GN m-3 at 10 K, 12 T and 900 GN m-3 at 4.2 K, 18 T.