Crystal Growth of Ba Concentration Controlled YBCO Films by TFA-MOD Process

YBCO films grown by the starting solution with Ba-poor (cation ratio as Y:Ba:Cu = 1:1.5:3) have been reported to have higher J _c than that for YBCO films with stoichiometric composition due to smaller and less pores in TFA-MOD YBCO. In this study, Ba concentration in the Ba-poor YBCO films was controlled in film thickness direction, and influences of the Ba concentration gradient on microstructures and J _c properties were investigated to realize higher J _c. Precursor films with Ba-poor composition and with Ba-rich composition in the thickening direction were prepared and then the films were crystallized. Increasing the Ba concentration in thickening direction led to higher J _c than that of Ba-poor YBCO. Cross sectional TEM observations showed that the effective YBCO thickness increased for YBCO film with higher Ba concentration in comparison to the previous Ba-poor YBCO film.