Superconducting nanocomposite films grown by chemical solution deposition: synthesis, microstructure and properties
- Autores: Anna Llordés Gil
- Directores de la Tesis: Xavier Obradors Berenguer (dir. tes.), Susagna Ricart Miró (codir. tes.)
- Lectura: En la Universitat Autònoma de Barcelona ( España ) en 2010
- Idioma: español
- Tribunal Calificador de la Tesis: Bernhard Holzapfel (presid.), Luis Escriche Martínez (secret.), Daniel Chateigner (voc.)
- Materias:
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- Resumen
This Thesis is focused on the preparation of novel functional metal-oxide nanocomposite films by solution-based deposition methodologies. One of the most outstanding results of this work is the capability to prepare epitaxial nanocomposite films with embedded randomly oriented nanoparticles leading to the formation of incoherent interfaces. Such incoherent interfaces had not been observed before in epitaxial nanocomposite films. Therefore, their influence on the surrounding matrix has been studied in detail in this work in terms of either nanostructure or physical properties.
The nanocomposites films are based on an epitaxial YBa2Cu3O7 superconducting matrix in which non-superconducting oxide nanoparticles (i.e. BaZrO3 and Y2O3) are embedded in order to enhance the magnetic flux pinning properties. A thorough study of the nanoparticles texture as well as of the matrix nanostructure has been carried out by X-ray diffraction (XRD) techniques. Such investigations have led to understand the complex microstructure-properties relationship in these novel materials. In particular, it has been found that the incoherent interfaces arisen between the epitaxial matrix and the randomly oriented nanoparticles are the responsible of inducing strain at the nanoscale level (i.e. nanostrain) on the YBa2Cu3O7 lattice. The fact that nanostrain is higher in YBa2Cu3O7-BaZrO3 nanocomposites becoming also isotropic leads to the most efficient flux pinning properties in these novel materials, turning thus YBa2Cu3O7-BaZrO3 nanocomposites very promising for high field power applications From the chemical viewpoint, it has been studied the Chemical Solution Deposition methodology, in particular the precursor decomposition reaction. The analysis of both the solid and gaseous phases has permitted to determine the complete decomposition chemical reaction which was so far unknown. In addition, the porosity development in the as-decomposed films has been studied, being possible to reduce and even eliminate the undesired pores by reducing the oxidation power of the atmosphere.
