Investigations on the lead acetate addition in precursor solutions for YBCO superconducting film deposition

Chemical solution deposition is a promising technology to fabricate YBCO superconducting thin films due to its low-cost advantage. As found in our previous study, the addition of lead acetate in precursor solution could enhance the critical current density of YBCO films, since the deteriorating a/b-axis orientated grains could be suppressed. In this study, the precursor solutions with lead acetate weight percentages of 0%, 1%, 2% and 3% were prepared. The molar concentration of all metal ions was 2.0 mol/L for all solutions. Crystallization temperatures of 720°C, 740°C, 760°C, 780°C, 800°C and 820°C were used in the heat treatment. The thickness of the finally obtained YBCO films was about 400 nm. It was found that 1% of lead acetate addition was favorable to achieve high critical current at 77 K in self-field, and the critical current generally increased along with the crystallization temperature. The cross-sectional microstructure of YBCO thin films fabricated by using lead acetate addition was denser than that of the counterpart samples. In situ measurement of the film's resistance during the heat treatment was carried out to analyze the growth and nucleation processes of YBCO thin film deposition. The mechanism of lead acetate addition for the a/b-axis oriented grain suppression reported in our previous study was investigated.