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Jaimoo Yoo,Young-Kuk Kim,Kookchae Chung,Jaewoong Ko,Xiaolin Wang,Shi Xue Dou Institute of Electrical and Electronics Engineers 2007 IEEE transactions on applied superconductivity Vol.17 No.2
<P>MOD solutions for YBCO coated conductors were synthesized with fluorine-free Y & Cu precursor. The fluorine content in the precursor solution was significantly reduced and a fast calcination profile was realized. A crack-free & thick precursor film was successfully obtained just after less than 2 hours of calcination in wet O<SUB>2</SUB> atmosphere. Optimization of the precursor solution with Sm addition enables further improvement of thickness and uniformity of precursor films. The calcinated precursor film was successfully converted to dense and uniform YBCO film after annealing in wet Ar/O<SUB>2</SUB> atmosphere. The measured critical current value was about 273 A/cm-w (J<SUB>c</SUB> ~ 3.8 MA/cm<SUP>2</SUP>), and well-developed microstructure was confirmed. Also discussed are recent developments in the reel-to-reel processing using the precursor solution with low fluorine-content. It was shown that employing fluorine-free Y & Cu precursor solution enabled uniform and fast processing of YBCO coated conductors.</P>
Yoo, Jaimoo,Ko, Jae-Woong,Kim, Young-Kuk,Chung, Kook-Chae IEEE 2005 IEEE transactions on applied superconductivity Vol.15 No.2
Homogeneous and fine BSCCO precursor powders were prepared by spray pyrolysis (SP) method starting from an aqueous solution of metal nitrates. The influence of solution concentration, furnace reaction temperature and types of spray on microstructure and average particle size were investigated. The synthesized precursor powders had a narrow particle size distribution and low carbon content. The reactivity of precursor powder by SP method is very high, attributed to the fine and narrow particle size distribution of precursor powders. The precursor powder by SP method promoted a very quick formation of the 2223 phase for short sintering time. The XRD result shows high possibility of reducing secondary phases such as large AEC and almost phase pure microstructure through more homogeneous reaction.
Chemical Modification of Precursor Solution for Long Length YBCO Coated Conductor Fabrication
Yoo, Jaimoo,Kim, Young-Kuk,Chung, Kookchae,Ko, Jaewoong,Hong, Gye-Won,Lee, Hee-Gyoun,Kim, Jin-Heung,Chung, Hyungsik,Wang, X L,Dou, S X Institute of Physics Publishing Ltd 2006 Journal of Physics: Conference Series Vol.43 No.-
<P>Long length MOD processing of YBCO conductor requires high performance precursor solution without degradation during the process. In this study, effect of chemical modification of precursor solution on MOD processing was investigated to meet the requirement. Highly stable YBCO precursor solution was synthesized with PVP (polyvinylpyrrolidone) and crack-free thick precursor film was successfully fabricated. However, annealed YBCO film shows porous microstructures originated from large HF gas generation from thick films and residual carbon from additives. Reduction of fluorine content is required to densify microstructures. In order to reduce fluorine content, F-free Cu-precursor solution was synthesized. YBCO film with J<SUB>c</SUB>&equal;0.8MA/cm<SUP>2</SUP> was grown on buffered RABiTS tape. Annealed YBCO film still contains pores and further reduction of pores is required to improve critical current (I<SUB>c</SUB>)</P>