Advanced TFA-MOD process of high critical current YBCO films for coated conductors

摘要

Although the metalorganic deposition (MOD) process using metal trifuluoroacetete (TFA) is considered to be a strong candidate due low cost and high J_c performance as a fabrication process for coated conductors of Yba_2Cu_3C_(7-x) (YBCO), the long calcination time of 10 h for 300 nm YBCO thickness was a problem that needed to be solved in the case of the MOD process using the TFA salts for all elements (all TFA solution). In this study, in order to shorten the calcination time, a new combination of starting materials was developed. Through the investigation of the generation rate of hydro fluoride (HF) gas during calcination, it was found that the high generation rate at a high heating rate is the reason for the bubbling which prevents an increase of the heating rate. Therefore, the amount of fluorine (F) in the starting material was reduced by using the Cu-salt without F while maintaining the basic crystallization reaction in this process. A new heating process using these materials has been developed. Consequently, the calcination time was shortened to 40 percent using the All TFA solution and an overall transport I_c value of 292 A for 1 cm width was obtained (77 K in self-field).