Preparation Of SmBOC Superconducting Film By Fluorite-Free Polymer-Assisted Metal Organic Deposition

In this thesis, SmBa2Cu3O7-x (SmBCO) superconducting films were prepared on (001) LaAlO3 single crystal substrate by self-developed fluorine-free polymer-assisted metal organic deposition (PA-MOD) approach. High performance SmBCO superconducting films were prepared by adjusting the synthesis parameters of coating solutions. The different kinds of magnetic flux pinning centers were introduced into the SmBCO system to improve the current carrying capacity of the superconducting films.In chapter 1, the background of this research was introduced by combing the research status, types, applications and superconducting film introduction. Furthermore, the main research contents of this thesis were proposed based on the actual applications and basic research.In chapter 2, the characterization methods and experimental design process of this thesis were described. Details of the fluorine-free polymer-assisted metal organic deposition method of SmBCO films in the experimental process were designated, including coating solution preparation, coating process and heat treatment process. Moreover, the characterization of microstructure, crystal structure, magnetic and electrical transport properties are introduced in detail.In chapter 3, effects of different coating solutions synthesis parameters (including cation concentration and viscosity) on biaxial texture, microstructure and superconductivity of SmBCO superconducting films were studied. Cation concentration with 1.35mol/L, 1.15mol/L, 1.0mol/L and 0.8mol/L (with the cationic stoichiometry ratio of 1:2:3) superconducting films were prepared on LaA103 substrates by the method of self-developed fluorine-free PA-MOD. The Experiment results showed that the film with cation concentration of 1.0mol/L has good surface microstructure and biaxial texture, high superconducting transition temperature (about 91.2K) and the zero field critical current density (over 1MA/cm2). This cation concentration is the best cation concentration ratio of preparing high performance SmBCO superconducting film. Moreover, in this paper, PVB (polyvinyl butyral) was used as polymer additives to study the effects on biaxial texture, microstructure and superconductivity of SmBCO superconducting films. The results show that film with 4% addition has good biaxial texture, smooth and no cracks microstructures. In addition, Tc and Jc of this film is 89.5K and over 1MA/cm2 (65K, 0T), indicating excellent superconducting properties.In chapter 4, effects of Co3+ doping and second phase particles BaZrO3 on biaxial texture, microstructure and superconductivity on SmBCO superconducting thin film were discussed. The results show that Tc of Co34-doping film was reduced because of the decrease of carrier concentration of the system. But JJJc(0) values of Co3+-doped SmBCO films are higher than that of pure films at different temperatures and magnetic fields. The Tc of SmBCO thin films with introduced BaZrO3 was 90.5K. JJJc(0) values of SmBCO films are higher than that of pure films at different temperatures and magnetic fields. This may be because the particles which matched with the superconducting coherence length and the local lattice distortion caused by BaZrO3 second phase particles worked as the effective pinning centers.