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Rheinbach, Germany

Scheuerlein C.,CERN | Andrieux J.,University Claude Bernard Lyon 1 | Rikel M.O.,Nexans SuperConductors GmbH | Rikel M.O.,Deutsche Nanoschicht GmbH | And 9 more authors.
IEEE Transactions on Applied Superconductivity | Year: 2016

We have studied the influence of the oxygen partial pressure pO2 up to 5.5 bar on the phase changes that occur during the melt processing of a state-of-the-art Bi-2212 multifilamentary wire. Phase changes have been monitored in situ by high energy synchrotron X-ray diffraction. We found that the stability of the Bi-2212 phase is reduced with increasing pO2. For pO2 > 1 bar, a significant amount of the Bi-2212 phase decomposes upon heating in the range of 400 °C-650 °C. The extent of decomposition strongly increases with increasing pO2, and at pO2 = 5.5 bar Bi-2212 completely decomposes in the solid state. Textured Bi-2212 can be formed during solidification when pO2 is reduced to 0.45 bar when the precursor is molten. Since the formation of current-limiting second phases is very sensitive to pO2 when it exceeds 1 bar, we recommend to reduce the oxygen partial pressure below the commonly used pO2 = 1 bar, in order to increase the pO2 margins and to make the overpressure process more robust. © 2002-2011 IEEE.

Feys J.,Ghent University | Ghekiere B.,Ghent University | Lommens P.,Ghent University | Hopkins S.C.,University of Cambridge | And 7 more authors.
Materials Research Society Symposium Proceedings | Year: 2013

In this paper, we present ink-jet printing as an attractive alternative to lithography and etching methods for the development of multi-filamentary YBa2Cu3O7-δ coated conductors. Our research is mainly focused on the study of the influence of rheological parameters on the printability of water-based inks in order to produce superconducting patterns on SrTiO3 and CeO2-La 2Zr2O7-Ni5at%W substrates. An aqueous YBCO precursor ink with a total metal ion concentration of 1.1 mol/L with a viscosity of 6.79 mPa s and a surface tension of 67.9 mN/m is developed. Its printing behavior using several ink-jet printing devices is verified using a camera with strobed illumination to quantify droplet velocity and volume. After optimization of the deposition parameters, YBCO tracks with different dimensions could be printed on both types of substrates. Their shape and dimensions were determined using optical microscopy and non-contact profilometry, showing 100-200 nm thick and 40-200 μm wide tracks. Finally, resistivity measurements were performed on the widest tracks on SrTiO3 showing a clear drop in the resistivity starting from 88.6 K with a ΔTc of 1.4 K. © 2013 Materials Research Society.

Vermeir P.,University College Ghent | Vermeir P.,Ghent University | Feys J.,Ghent University | Pollefeyt G.,Ghent University | And 8 more authors.
Materials Research Society Symposium Proceedings | Year: 2013

Chemical solution deposition techniques are a very competitive low cost method to achieve coated conductors. Recently, fluorine-free CSD methods have made a great progress for the preparation of YBCO thin films and became a sustainable alternative for the well-known trifluoroacetate CSD approach. By elucidating the reaction mechanism behind this new approach, finally giving an answer to the question why it is possible to fabricate YBCO films without TFA, different processing routes were discovered giving rise to high superconducting YBCO films (>1MA.cm-2). Each route has it's own benefits. One specific route offers the opportunity to tune the crystallographic orientation. By changing one process parameter, a shift from complete c-axis to complete a-axis orientation is observed. This can be very useful for e.g. Josephson Junctions. We particularly investigated the fundamental reaction mechanism of each reaction route, with the focus on the corresponding barium compound. Although good superconducting properties are obtained, still one major drawback limits industrial implementation: thickness. It is observed that a critical thickness of ∼500 nm eliminates the superconducting properties. Therefore, this paper gives a summary of all progress made regarding to fluorine-free water-based CSD YBCO thin films with emphasis on the possibility to control the crystallization rate. Copyright © Materials Research Society 2013.

Hopkins S.C.,University of Cambridge | Mitchell-Williams T.B.,University of Cambridge | Vanden Bussche D.R.,University of Cambridge | Vanden Bussche D.R.,Ghent University | And 15 more authors.
IEEE Transactions on Applied Superconductivity | Year: 2016

Impressive performance has been achieved in (RE Ba2 Cu3O7-δ (REBCO) coated conductors, but for many applications, the high cost and ac losses remain prohibitive. Inkjet printing methods combine scalability and low equipment cost with high-resolution patterning, potentially addressing both issues by enabling the production of multifilamentary coated conductors without subtractive processing. The successful production of multifilamentary superconducting YBa2Cu3O7-δ (YBCO) structures by inkjet printing of a low-fluorine YBCO precursor solution on SS/ABAD-YSZ/CZO substrates is reported. Two approaches have been developed. In the first method, YBCO filaments were directly deposited on the buffered substrate by piezoelectric printing; and in the second approach, CeO2 tracks were first printed to pattern a subsequently overprinted YBCO film, creating a multifilamentary structure by an inverse technique. Scanning Hall probe measurements have been used to compare the filamentary structures and critical currents achieved by both methods, and a Jc of up to 3 MA cm-2 has been obtained at 77 K. For the inverse printing approach, the ac hysteresis losses have been also measured and compared with theoretical models. © 2016 IEEE.

Scheuerlein C.,CERN | Bjoerstad R.,CERN | Grether A.,CERN | Rikel M.O.,Nexans SuperConductors GmbH | And 5 more authors.
IEEE Transactions on Applied Superconductivity | Year: 2016

The electromechanical properties of different cuprate high-temperature superconductors, notably two ReBCO tapes, a reinforced and a nonreinforced Bi-2223 tape, and a Bi-2212 wire, have been studied. The axial tensile stress and strain, as well as the transverse compressive stress limits at which an irreversible critical current degradation occurs, are compared. The experimental setup has been integrated in a high-energy synchrotron beamline, and the self-field critical current and lattice parameter changes as a function of tensile stress and strain of a reinforced Bi-2223 tape have been measured simultaneously. Initially, the Bi-2223 filaments exhibit nearly linear elastic behavior up to the strain at which an irreversible degradation is observed. At 77 K, an axial Bi-2223 filament precompression of 0.09% in the composite tape and a Bi-2223 Poisson ratio ν=0.21 have been determined. © 2016 IEEE.

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