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Développement de conducteurs à base d'YBaCuO
sur des substrats flexibles par MOCVD

Abstract : The stake of this study was to realize low cost superconducting wires for current transport and current limitation, using original and inexpensive processes like rolling for the elaboration of the substrate, and chemical deposition methods MOD (metal organic decomposition) and MOCVD (metal organic chemical vapor deposition) for the different layers (buffer layers and superconducting film).
Pulsed injection MOCVD technique is well adapted for coated conductor processing: it allows obtaining reproducible epitaxial YBCO films and can be extrapolated for long length conductors. However the deposition of buffer layers by MOCVD on flexible metallic substrates causes its oxidation and destroys its crystalline structure. The combination of both MOD and MOCVD solves this issue: the deposition of a first La2Zr2O7 (LZO) buffer layer by MOD under reducing atmosphere (Ar + 5%H2) avoid the oxidation of the substrate during the following depositions by MOCVD. Two architectures have been developed and characterized: NiWRABiTS/LZOMOD/YBCOMOCVD and NiWRABiTS/LZOMOD/CeO2MOCVD/YBCOMOCVD. The study of these conductors proved such architectures can reach high critical current densities: JcLZO/LZO/YBCO = 0.8 MA/cm2 with
Ic/cm = 34 A/cm, and JcNW/LZO/CeO2/YBCO = 1.2 MA/cm2 with Ic/cm = 54 A/cm, on 800 nm thick YBCO conductors.
A TEM study allowed us to understand the growth of the LZO film and to observe the formation of pores during the pyrolysis of the precursors. Combined EBSD and MO studies demonstrated that the microstructure of the substrate (grain boundaries, scratches ...) is transferred to the superconducting film, what has a negative influence YBCO inter-grain connectivity and thus on YBCO film quality. The deposition of thick buffers layers (> 150 nm) smoothes these defects and improves superconducting properties of the conductors.
Finally, successful tests in current limitation and in current transport under strain validated the fabrication process for such specific application.
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Contributor : Tristan Caroff <>
Submitted on : Thursday, November 27, 2008 - 1:58:38 PM
Last modification on : Thursday, November 19, 2020 - 12:59:39 PM
Long-term archiving on: : Saturday, November 26, 2016 - 2:35:48 AM

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Tristan Caroff. Développement de conducteurs à base d'YBaCuO
sur des substrats flexibles par MOCVD. Supraconductivité [cond-mat.supr-con]. Institut National Polytechnique de Grenoble - INPG, 2008. Français. ⟨tel-00342414⟩

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