Development of YBCO film approached by TFA-MOD method using the Y2Ba1Cu1Ox and Ba3Cu5O8 powders
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0946-HH08-06
Development of YBCO Film Approached by TFA-MOD Method Using the Y2Ba1Cu1Ox and Ba3Cu5O8 Powders Jun Hyung Lim1, Seok Hern Jang1, Kyung Min Yoon1, Jinho Joo1, Seung-Boo Jung1, and Wansoo Nah2 1 School of Advanced Materials Science and Engineering, Sungkyunkwan University, 300 cheoncheon, Jangan, Suwon, Gyeonggi, 440-746, Korea, Republic of 2 School of Electrical and computer Engineering, Sungkyunkwan University, 300 cheoncheon, Jangan, Suwon, Gyeonggi, 440-746, Korea, Republic of
ABSTRACT The YBCO films were fabricated by TFA-MOD method in route of “211 process” and evaluated the phase formation, texture evolution, and critical current and critical temperature as a function of the humidity firing process. In the fabrication process, Y2Ba1Cu1Ox and Ba3Cu5O8 powders, instead of Y-, Ba- and Cu-based acetates, were used as precursors. In order to evaluate the effect of humidity during the firing process, the films calcined at 430℃ were fired at 775℃ in dry Ar(0%), 4.2%, 8.0%, 12.1%, and 20.0% humidified Ar gas mixed with 1000 ppm oxygen. We observed that the amount of BaF2 phase was effectively reduced and that a sharp and strong biaxial texture formed under a humidified atmosphere, leading to increased critical properties. The film became denser and the degree of texture and phase purity varied as the humidity increased. For the film fired in 0% humidity, the measured value of Tc(onset) was found to be 82.5 K, but the Tc(zero) could not be measured. When the humidity was increased to 4.2%, the corresponding Tc(onset) and Tc(zero) were increased to 91.5 K and 88.6 K, respectively. For the films in the humidity range of 12.1-20.0%, the critical current density was found to be 1.54 MA/cm2. INTRODUCTION In order to obtain phase purity and a strong biaxial texture in the YBCO coated conductors (CCs), many thin film deposition processes have been devoted such as coevaporation, PLD, BaF2 process, MOCVD, and metal organic deposition (MOD), etc. Most of them use high vacuum techniques requiring expensive equipment. On the other hand, the MOD process has received a great deal of attention, because of wide flexibility to coating materials and non-vacuum approach. Recently, the MOD method using trifluoroacetic acid (TFA-MOD) is considered to be one of the most promising processes since it exhibited the highest critical current density (Jc) of 3.6 × 106 A/cm2[1]. In the TFA-MOD method, the acetates of Y, Ba, and Cu dissolved in TFA are used as the precursor and BaF2 is formed as an intermediate phase during the decomposition procedure. It is known to be difficult to depress the formation of the BaF2 phase, unless the processing conditions are precisely controlled, with the result that this method has low reproducibility. To this end, it would be desirable to develop a new synthetic method involving the use of a more reproducible and stable reaction by selecting other precursors and/or solutions. In the fabrication of YBCO bulk superconductors, Y2Ba1Cu1OX (Y211) and Ba3Cu5O8
powders have been used as the precursors (
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