Research On The Fabrication Of YBCO Superconducting Thin Film Using Non-Fluorine Chemical Solution Deposition

YBCO superconducting film is fabricated on the single crystal LaAlO₃ substrates using non-fluorine chemical solution deposition.The final structure and superconductivity performance of the YBCO film are directly associated with some processing parameters.In this thesis,we explored the connection between parameters like rates of temperature rising,the duration of heating, partial pressure of water,heating temperature,spinning control and so on,and microstructure and superconductivity of the film.DSC/TG analysis was used to find the temperature zone of volatilization of the solvent and that of decomposition of metal organics.XRD 2θscan indicated that the films have strong c-axis orientation.SEM images determined no pore space and no second phase separation inside the thin films.The changes of the thickness of the film were detected by the combination of the profilometer measurement and the secondary electron image and the backscattered electron image of cross section of the thin film.Magnetic measurement by MPMS indicated that the critical transition temperature was 85K which is lower than reported 91K because of the impurity of the orthogonal crystallization.With the combination of YBCO phase diagram and the thermodynamics of crystallization,two temperature points,at which the value of growth rate to nucleation rate reached maximum,were discovered.The connection between the generation of pores and decomposition rate was figured out.The relationship between the phenomenon of spot separation and processing parameters like drying rate of the precursor solution,duration of melting and melting temperature,were found out.Effective solutions to eliminate the defects like pores and separation were proposed.By the means of controlling the processing conditions like moving atmosphere and water partial pressure, we successfully avoided the formation of BaCO₃ spots,during the non-fluorine chemical solution deposition approach.A feasible suggestion that based on the processing parameters was arisen to introduce the flux pinning center from BaCO₃ dots.The variety of the thickness of the film during the phase transformation was characterized under single-coated circumstance.The density and contact effect of the film were improved by the introduction of a transitory high temperature treatment ahead of epitaxial growth.