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Polyethyleneimine (PEI) with an amount of -NH2 groups used in precursor solution could effectively reduce Cu2+ volatilization during the pyrolysis process. Thermogravimetric analysis shows that the temperature window of low-temperature pyrolysis for precursor solution with PEI (PEI-YBCO) is widened significantly. The slower pyrolysis process can enrich Cu2+ and improve critical current density (Jc) of PEI-YBCO films. The highest Jc is 3.03 MA/cm2 at 77 K when the amount of PEI is 0.5 g/10 mL and the film thickness is 400 nm. Then the thickness increases from 0.4 to 2.0 μm by changing the coating times. The Jc values of PEI-YBCO films decrease gradually with the thickness increase. However, the critical current (Ic) can be up to 197 A/cm (at 77 K, self-field) and Jc can still keep 1.68 MA/cm2 at 1.2 μm. [ABSTRACT FROM AUTHOR]

Thick YBaCuO (YBCO) films grown by metallorganic deposition (MOD) are very significant for high-performance superconducting wires. In the present work, the modified MOD method with reduced fluorine content in precursor solution (namely LF-MOD in the following) is applied to prepare the YBCO films with the purpose of reducing the processing time as well as increasing thickness. Five-layer YBCO films with a thickness of more than 2.5 μm are achieved after the effect of high-temperature annealing time ( t) on the morphology and texture of YBCO films is systematically investigated. It is suggested that an annealing time as long as 6 h appears necessary to achieve a good performance for such a thick YBCO film. To understand the evolution of texture with thickness, plasma etching is employed to characterize the profile morphology at different depths inside the films, revealing the a-axis grains together with the impurity phases arising from the incomplete reaction mostly present at the top surface only. [ABSTRACT FROM AUTHOR]

This work presents a study of the evolution of the phases in the intermediate heat treatment process (IHP) which was after the pyrolysis process and before the crystallization of YBCO superconducting thin films. It was shown that the evolution of the solid solution could always take place whether with or without water vapor and oxygen. When water vapor is present in the atmosphere, the evolution temperature of the intermediate phase was lower than the one without vapor. The intermediate phase of YCuO with the vapor was observed at 680 °C. By calculating the changes of Gibbs free energy of reactions possibly involved in the IHP, the priority reaction with water vapor was CuF>YF>BaF when CuF, YF, and BaF coexisted while CuF and YF prefer to react with BaO to form BaF while they coexisted. The appearance of intermediate phase features could be illustrated through the calculation. [ABSTRACT FROM AUTHOR]