Study On Properties Of YBCO Thin Films Doping With Different Impurity Ion

YBCO thin film has got a lot of attention, due to its excellent properties and potential price advantage. In recent years, the YBCO thin film has a very broad application prospects in the industrial production and other fields. However, the lower critical current density in applied filed limits its application in some fields severely. The purpose of this thesis is to improve the peoperties of YBCO thin films in applied filed.In this thesis, YBa2Cu3-xRxO7-z (R=Li, Ni and x=0,0.0005,0.001,0.0015 and 0.002) thin films were prepared by a fluorine-free polymer-assisted metal organic deposition method. Their crystal structure, surface morphology and peoperties were investigated by X-ray Diffraction, Scanning Electron Microscope, Physical Property Measurement System and Magnetic Property Measurement System. The results shows that the crystal structure and surface morphology of YBCO thin films with dilute Li+ and Ni2+ doping won’t change obviously; With the increase of doping amount, superconducting transition temperature of the YBCO thin films is gradually reduced; the YBCO thin films with dilute Li+ and Ni2+ doping can enhance the flux pinning performance in high applied filed at low temperature and high temperature within the whole applied filed, and improve the peoperties in applied filed effectively. Compared with the YBCO thin film with Ni2+ doping, the YBCO thin film with Li+ doping has stronger flux pinning performance and higher critical current density in applied filed. In addition, the flux pinning mechanism of pure and doping with dilute Li+ and Ni2+ were analyzed. It can be drawn that surface pinning of normal phase is the main source of flux pinning in pure YBCO thin films and surface pinning of normal phase and point pinning of normal phase is the main source of flux pinning in YBCO thin films doping with dilute Li+ and Ni2+ doping.In the next section, the YBCO thin films with dilute Ca2+ doping Y site and Cr3+ doping Cu site and co-doping were prepared through the above process. Their crystal structure, surface morphology and peoperties were investigated by X-ray Diffraction, Scanning Electron Microscope and Magnetic Property Measurement System. The results shows that the crystal structure and surface morphology of YBCO thin films with dilute impurity ions single-phase doping and co-doping won’t change obviously; co-doping have greater inhibitory effect than single-phase doping on superconducting transition temperature of YBCO thin films; the flux pinning performance of co-doping YBCO thin films in the applied magnetic field is better than single phase doping YBCO thin films, which leads to its critical current density in the applied magnetic field is greater than single-phase doping YBCO thin films. In addition, the flux pinning mechanism of YBCO thin films with dilute impurity ions single-phase doping and co-doping were analyzed. In YBCO thin films with dilute impurity ions single-phase doping, the normal phase point defect is homogeneously distributed; but, in YBCO thin films with dilute impurity ions co-doping, due to the interaction between the normal phase point defect, they formed a columnar defects spontaneously, so as to make the YBCO thin films of flux pinning strength greatly enhanced.