The Research On Advanced Calcinations Treatment Process Of YBCO Thin Film

In this thesis, fluorine-free chemical solution deposition (CSD) method was used to prepare YBCO superconducting thin film, which was developed in our group as reported before. To impove the efficiency and meet the industrial demand, the calcinations route was studied and optimized.It was found out that there were two stages in the decomposition process:volatilization and decomposition. The two procedures were studied separately in this thesis, while they were proceed in the same heat treatment of traditional calcinations.In order to volatilize rapidly, the coated film was put directly at a temperature near the boiling point of the solvent at the stage of volatilization. In the stage of decomposition, differential thermal analysis was used to investigate the reason of the low heating rate in traditional calcinations route. From the results of differential thermal analysis, it was discovered that the melting point of copper acetate was much lower than its decomposition temperature, led to a widespread melting state causing the low heating rate in traditional calcinations. According to this conclusion, the YBCO precursor film was put at a temperature much higher than the decomposition temperature of copper acetate after rapid volatilization. Therefore the copper acetate would decompose in solid state. Thus the precursor film was in a completely solid state. Finally the calcinations were accomplished at a higher heating rate.In this thesis, the optimal process of advanced calcinations was as follows:heated at138℃for30min, then heated at290℃for10min, then increased to500℃at a ramp rate of8℃/min. Thus the advanced calcinations could be completed in1h or so with a smooth and dense surface. Comparing to the traditional process (>13h), the time-consuming was greatly shortened. The YBCO precursor film were crystallized and oxygenized after the advanced calcinations. Only intense (001) peaks were observed in the XRD results indicated high c-orientation. Still, the SEM result showed standard epitaxial microstructure with a superconducting transition temperature Tc up to92K.