Fabrication of YBa₂Cu₃O_7-x films on buffered metal tapes fired at low temperature by MOD method using trifluoroacetate salts

Metalorganic deposition (MOD) using trifluoroacetates is considered to be one of the most promising methods for coated conductors, because it enables us to obtain very high J_c films with low-cost facilities. We have optimized various processing conditions in this method and successfully obtained critical current density (J_c) of 4.1MA/cm² (77K, 0T) for the YBa₂Cu₃O_7-x (YBCO) film of 1800Å in thickness on CeO₂ buffered YSZ single crystal, which was fired at 800°C. In the case of YBCO films on buffered metallic substrates, it is difficult to fabricate under the same deposition condition. Then low temperature heat treatment is required for deposition on metal substrate. On the other hand, such heat treatment also permits non-reacted BaF₂ in fired film, that leads to low J_c of the film. Therefore it is the key to fabricate YBCO film with entire reaction of BaF₂ by the low temperature heat treatment. We have investigated chemical reactions in firing and established a firing profile to fabricate YBCO film even at 725°C. With this profile, we can successfully fabricate the YBCO film at 725°C on CeO₂ buffered YSZ single crystal which has J_c of 3.0MA/cm² and the YBCO film on CeO₂ (sputtered) / YSZ (Ion-beam-assisted deposition: IBAD) buffered Ni based alloy (hastelloy) tape which has J_c of 0.81MA/cm².