Un enfocament híbrid per obtenir nanocristalls d'alta qualitat de perovskites bamo₃ per nanocompòsits superconductors de yba₂cu₃ o7 − δ

Resumen

This thesis describes the synthesis and characterization of novel perovskite BMO3 nanocrystals and its application improving properties of superconducting material. The developed synthesis protocols allowed to tune nanocrystals’ size and achieve long-time stability in solutions with high salt media content. These new properties in the nanocrystals were exploited to embed them into a superconducting material, YBa2Cu3O7−δ, enhancing the superconducting properties of the material. The general trends of BMO₃ have been unravel using a hybrid solvothermal methodology based on the specific combination of aqueous sol-gel and solvothermal treatments. Using this methodology we reported a general, easy, fast and reproducible synthesis route of BMO₃ nanocrystals. Moreover, we present detailed studies of different synthetic conditions as well as insights in the mechanism of the nanocrystal’s formation. Considering previous approximations to this perovskite family, our methodology provides highly crystalline shape-defined nanocrystals with a drastic reduction on reaction time. Through the study of BaZrO₃ nanocrystals we postulated the governing mechanism tunning the sizes of the nanocrystals. This proposed mechanism proved to be not only specific to this case but also applicable to other perovskites. Our hybrid methodology demonstrated the successful synthesis of BaMO₃ M= (Ti4+, Zr4+ and Hf4+) nanocrystals, besides of, obtaining SrTiO3 when changing the divalent cation for Sr2+. We have studied the applications of the synthesized nanocrystals improving the superconducting properties of nanocomposites films prepared by chemical solution deposition using precursor solution of Yttrium, Barium and Copper salts. Additionally, the nanocrystals showed long term high stability in different YBa2Cu3O7−δ precursor solutions even at high nanocrystals concentration. Herein, we demonstrate for the first time, that non-reactive BMO₃ (M= Zr4+ and Hf4+) nanocrystals are suitable for growing high quality thin and thick films using chemical solution deposition. Furthermore, we also demonstrated that the composition and sizes of the nanocrystals are a crucial factor for tailoring vortex pinning performances in applied magnetic fields. In conclusion, we not only present the achievement of easily tunable-size and high-stable BMO₃ perovskite nanocrystals but demonstrated their effectiveness to enhance the superconducting properties when the nanocrystals are mixed into YBa2Cu3O7 matrix. Given the novelty and potential relevance of our hybrid method in a deep range of nanoscale systems.