Research On YBCO Composite Structure And Flux Pinning

High temperature superconducting YBCO thin films and its related devices with wide application field and high potential economic value,especially with high critical current density?Jc>1MA/cm²,0T?,is considered to be the most potential materials for high-tempe rature superconducting in power application field.But the critical current density exponentially reduced with the increase of the magnetic field,which greatly limits the application process of YBCO thin film.Therefore,to improve the superconducting properties of high-temperature superconductors has become the problem which need to solve.In the experiment,the micro pattern were prepraed on the substrate by using the micro-fabrication method which combined sol-gel method with chemical modification,then the YBCO composite structure were prepared by growing YBCO film in the fine pattern,and discusses this fine patterning of the composite structure effect on the superconductivity of YBCO,and further study the flux pinning effect in the composite structure.Main research achievements are as follows:?1?The YBCO films were prepared by non-fluorine sol-gel method with an optimized heat-treatment process.XRD and superconductivity test results show that the YBCO film has single c-axis orientation and good superconducting properties,which provides favorable advantagement for the fabrication of YBCO composite structure.?2?The YBCO/graphical PZT-LaCoO₃ composite structure was fabricated on LAO single crystal substrate.XRD analysis and superconducting properties measurements show a chemical reaction occurs among PZT-LaCoO₃ and YBCO films,leading to the formation of impurities BaZrO₃ and ZrO₂ phase.These impurities produce more defects in YBCO films,resulting in an increase in the number of non-c-axis orientation YBCO grain,thereby failure to improve the YBCO films flux pinning properties effectively.?3?The YBCO/graphical Y₂O₃ composite structure was fabricated on LAO single crystal substrate.XRD and HRTEM analysis show that the introduction of Y₂O₃ fine figure to YBCO thin films produce some nanoscale crystal defects,resulting in some crystal plane bending phenomenon occurs,thereby forming a number of stacking faults,crystal lattice distortion and other defects.The superconducting properties measurements show the rate of J_c decrease for YBCO/graphical Y₂O₃ composite structure with magnetic field is less than the rate of the pure YBCO thin film,which indicates the introducing of Y₂O₃ fine figure in YBCO thin films.improve flux pinning capability.