Stéphanie Morlens

High-resolution transmission electron microscopy observations of La2Zr2O7 thin layers on LaAlO3 obtained by chemical methods

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. HRTEM observations of La2Zr2O7 thin layers on LaAlO3 obtained by chemical methods L. Rapenne, Carmen Jiménez, Tristan Caroff, C. Millon, Stéphanie Morlens, Pascale Bayle-Guillemaud, François Weiss

New YBCO superconducting wires obtained from narrow textured tubes

A conductor wire consisting of Ag/YBCO/LZO/Ni?5?at.%W RABITS has been processed as a cylindrical tube of millimetre diameter. Textured layers of LZO and YBCO were grown by chemical methods. Electron backscattered diffraction was used to characterize the texture of the LZO surface which was good enough to be used as a template for YBCO deposition. The YBCO layer was textured and had a superconducting transition at 88?K. However, the quality of both LZO and YBCO must be improved to consider practical applications in electrical current transport. On the other hand, this work demonstrates that epitaxial growth of oxides on a curved surface by using chemical methods is possible.

HRTEM observations of La2Zr2O7 thin layers on LaAlO3 obtained by chemical methods

La2Zr2O7 (LZO) films have been grown by metalorganic Decomposition (MOD) to be used as buffer layers for coated conductors. LZO can crystallize into two similarstructures: fluorite or pyrochlore. Coated conductor application focuses on pyrochlore structure because it is a good barrier against oxygen diffusion. Classical X-ray diffraction is not able to separate the contribution of these two structures. TEM and HRTEM were used to determine the local distribution of these two phases in epitaxial LZO layers grown on LaAlO3. A characteristic feature of LZO thin films deposited by MOD is the formation of nanovoids in an almost single crystal structure of LZO pyrochlore phase. Forcomparison, LZO layers deposited by Metalorganic Chemical Vapor Deposition (MOCVD) were also studied. In this last case, the film is compact without voids and thestructure corresponds to pyrochlore phase. Thus, the formation of nanovoids is a characteristic feature of MOD grown films.