Growth process of Ba-poor YBCO film fabricated by TFA-MOD process

Abstract: Metal organic deposition process using trifluoroacetates (TFA-MOD) is one of the most promising processes to fabricate YBCO film. It has been reported that YBCO films grown by the starting solution with Ba-poor (cation ratio as Y:Ba:Cu=1:1.5:3) have higher JC value and has smaller and less pores than those of the YBCO film with stoichiometric composition. It is important to investigate the growth mechanism of YBCO crystals to obtain a high JC film by controlling the crystal structures. In this study, YBCO films were fabricated under various Ba concentrations in the TFA starting solution, and the influences of Ba composition on the growth process and microstructures were investigated. As a result, the Ba-poor YBCO film with Ba/Y=1.5 and high JC had less a-axis oriented Y123 in comparison with the film with Ba/Y=2. Furthermore, pores in the Ba-poor film were less than that in the stoichiometric composition film. This decrease of pores in the Ba-poor film was considered to be caused by the smaller size of non-reacted phases especially such as Ba–F rich particles entrapped by growing Y123 in the growing Y123 layer. It is considered that both the reductions of a-axis oriented Y123 and pores were the reasons of improving JC values in Ba-poor film. [Copyright &y& Elsevier]