Fabrication and Analysis of Tri-layer YBa2Cu3 O 7−δ Thick Films by Low-Fluorine MOD Method
Improving the thickness of superconducting layer in coated conductors is an effective way to enhance its critical current. In this work, tri-layer YBCO/YBCO/YDyBCO films were successfully deposited on buffered Hastelloy substrate using the multi-coating lowfluorine metal-organic decomposition (LF-MOD) method and the thickness of the films can be up to 2.4 μ m. The effects of high-temperature annealing time on microstructures and superconducting properties of the films were systematically studied. Energy dispersive X-ray spectroscopy (EDS) results reveal that there remains a large amount of F element in the upper layer of the film when the annealing time is too short. With increasing the annealing time, the fluoride-containing precursor converts to YBCO grains completely. But the coarsening of grains appeared, and the critical current density (J c) of the film dropped slightly when the annealing time is too long. The cross-sectional scanning electron microscope (SEM) image and EDS plane analysis were applied to investigate the microstructure and element distribution of the final triple-layer YBCO films, respectively. The critical current of the final YBCO superconducting film could reach 316 A (77 k, self-field) for 1.2-cm-wide tapes with the optimal annealing conditions.
KeywordsYBCO thick film LF-MOD Multi-coating Annealing time Critical current
We thank M.J. Sun and M. BOUBECHE for valuable discussions.
This work was supported in part by Shanghai Key Laboratory of High Temperature Superconductors (14DZ2260700), the Science and Technology Commission of Shanghai Municipality (16521108400, 16DZ0504300, and 14521102800), and the National Natural Science Foundation of China (51572165, 11174193, and 51202141).
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