Effect of Ba/Y ratio in starting solution on microstructure evolution of YBCO films deposited by advanced TFA-MOD process

We have found that high critical current (IC) values of YBa2Cu3O7-y (YBCO) films are achieved by using the starting solution with the Ba/Y ratio less than 2.0 in the advanced TFA-MOD process. TEM observation revealed that there are few large pores in the YBCO final films with the Ba/Y ratio less than 2.0. Furthermore, from results of investigation of quenched films prepared by cooling rapidly during the calcination process, low Ba content in the starting solution was found to have an effect on attaining the precursor film with low porosity and uniform elemental distribution of cations. As for the crystallization process, there was no significant difference in phases and sizes of non-superconducting precipitates generated before YBCO epitaxial growth, irrespective of the Ba/Y ratio. However, homogeneity of lateral growth rate of the YBCO film is improved, when the starting solution with Ba/Y ratio less than 2.0 is used.