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Réalisation de multicouches pour supraconducteurs à haute température critique par méthode chimique

Abstract : The aim of this research is to study buffer layers made of CeO2 and La2Zr2O7 for high Tc superconductors devoted to energy transportation (coated conductors). We used Metal Organic Decomposition method (MOD) for the synthesis of layers of CeO2/SrTiO3 and La2Zr2O7/LaAlO3, because it is a soft and economic method well adapted to manufacture buffers layers for coated conductors. The comparison of various precursors of Cerium was made with the aim of obtaining the adequate precursor for the MOD process. Spin coating was used for depositing precursor solutions of Ce(EH)3 and LZ(propionic) on various substrates. Thermal analyzes of these precursors allowed to determine their decomposition mode (weight loss analysis) according to the temperature, to estimate the quantity of absorbed moisture by the precursors and to determine the temperature of crystallization of the oxide. It was also used to discuss the mixed nature or not of the lanthanum-zirconium proprionate. The analyses of the microstructure and of the texture of CeO2 and La2Zr2O7 films are established by X-ray diffraction (scans q-2q, w-scan, f-scan and pole figures). AFM and MEB allowed us to study roughness, topology and morphology of the surface. Heat treatments of the layers of C(EH)3/SrTiO3 and (La(prop)3+ Zr(prop)4)/LAO , under various atmospheres enabled us to differentiate the poly-crystalline growth from the epitaxial growth. The elimination of residual carbon in the grain boundaries, blocking the grain growth, was carried out by a control of the partial pressure of oxygen at the stage of crystallization; this step makes possible an improvement of the layers' texture. The heating rate has an influence on the nucleation which was studied. Increasing the heating rate favor the heterogeneous nucleation and decreases the number of nuclei, supporting the growth of larger epitaxial grains. Finally, we carried out the multi-layers CeO2/La2Zr2O7/LaAlO3 and YBaCuO/CeO2/YSZ/IBAD to validate the obtained results.
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https://tel.archives-ouvertes.fr/tel-00542828
Contributor : Abdenacer Guibadj <>
Submitted on : Friday, December 3, 2010 - 4:24:11 PM
Last modification on : Friday, December 18, 2020 - 1:08:04 PM

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Abdenacer Guibadj. Réalisation de multicouches pour supraconducteurs à haute température critique par méthode chimique. Physique [physics]. Université Joseph-Fourier - Grenoble I, 2009. Français. ⟨tel-00542828⟩

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