• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 추계학술대회 논문집
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• pp.90-92
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• 2003

Effects of organic additives on YBCO coated conductor prepared by MOD-TFA method were investigated. YBCO thin films were deposited on (100)-oriented single crystalline LaAlO$_3$substrates by conventional MOD-TFA process. The microstructures of YBCO thin films show labyrinth-like patterns. The origin of this microstructure was delineated by compositional inhomogeneity during the pyrolysis process of MOD process and it was shown that organic additives changes the microstructure and texture development of grown YBCO films

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 추계학술대회 논문집
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• pp.87-89
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• 2003

YBa$_2$Cu$_3$$O_{7-x}$ thin films were fabricated by MOD-TFA process via dipping method on LaAlO$_3$(LAO) single crystalline substrates. In this study, we investigated effect of solvent on the microstructure and crystallinity of YBCO thin films. The YBCO films derived from solvent with low boiling point has good surface morphologies.s.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 광주전남지부
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• pp.33-34
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• 2006

The effects of Ba and Ce addition has been investigated in YBCO prepared by trifluoroacetate (TFA) metalorganic depostition (MOD) method. Precursor solutions with cation ratios of Y:Ba:Cu:Ce = 1:2+x:3:x (x = 0, 0.05, 0.1 and 1.5) have been prepared by adding an excess amount of cerium and barium. Coated film was calcined at lower temperature and conversion heat treatment at temperature of $780{\sim}810^{\circ}C$. It has been shown that the critical current (Ic) of YBCO film was degraded by doping of Ba and Ce atoms. But Ic was increased as the amount of doped Ba and Ce content increased from 5 % to 15 %. It was observed that there was little increase of a flux pinning force with Ba and Ce addition in YBCO film prepared by TFA-MOD process.

• 한국초전도ㆍ저온공학회논문지
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• 제10권1호
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• pp.1-5
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• 2008

The effect of $BaCeO_3$ doping on the critical current density of YBCO film by TFA-MOD method was studied. $BaCeO_3$ doping was made by two method; one is direct addition of $BaCeO_3$ nano-sized powder prepared by citrate process followed by grinding with planetary ball mill for 10 hours. Another is addition of Ba-Ce precursor solution prepared with Ba-acetate and Ce acetate dissolved in TFA to the YBCO-TFA precursor solution. The film was made by standard dip coating and heat treatment process with conversion temperature of $790^{\circ}C$ in 1000 ppm oxygen containing moisturized Ar gas atmosphere. The direct addition of $BaCeO_3$ powder resulted in YBCO film with good epitaxial growth and no evidence of second phase formation. The addition through precursor solution resulted in the increase of critical current density upto 30 at% doping and uniform dispersion of $BaCeO_3$ fine inclusion was confirmed by SEM-EDX.

• Progress in Superconductivity
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• 제5권1호
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• pp.84-87
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• 2003

$YBa_2$$Cu_3$$O_{7-x}$ (YBCO) thin films were fabricated by MOD-TFA process via dip-coating method on LaAlO$_3$, (LAO) single crystalline substrates. In this study, we investigated effect of annealing temperature and solvent on the microstructure and texture of YBCO thin films. The precursor films were annealed at various temperature to improve surface morphologies and phase purities. It was shown that the films annealed at relatively lower and higher temperature exhibit low phase purity and crystallinity. The effect of various solvents on surface morphologies and second phase has been investigated.

• Progress in Superconductivity
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• 제7권1호
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• pp.77-82
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• 2005

We report a successful fabrication of high-quality $SmBa_{2}Cu_{3}O_{7-{\delta}}$ (SmBCO) thin films on $LaAlO_3$(LAO)(100) single crystalline substrates by a modified TFA-MOD method. After the pyrolysis heat treatment of spin-coated films up to $400^{\circ}C$, SmBCO films were fired at various temperatures ranging from 810 to $850^{\circ}C$ in a reduced oxygen atmosphere (10 ppm $O_2$ in Ar). Optimally processed SmBCO films exhibited the zero-resistance temperature ($T_{c,zero}$) of 90.2 K and the critical current density ($J_c$) of $0.8\;MA/cm^2$ at 77K in self-field. Compared with the $J_c$ values (normally, > $2\;MA/cm^2$ at 77 K) of MOD-TFA processed YBCO films, rather depressed $J_c$ values in SmBCO films are most probably attributed to the existence of ${\alpha}$-axis oriented grains.

• Progress in Superconductivity
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• 제8권1호
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• pp.87-92
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• 2006

The effects of Ba and Ce addition has been investigated in YBCO prepared by trifluoroacetate(TFA) metalorganic depostition(MOD) method. Precursor solutions with cation ratios of Y:Ba:Cu:Ce=1:2+x:3:x(x=0, 0.05, 0.1 and 1.5) have been prepared by adding an excess amount of cerium and barium. Coated film was calcined at lower temperature under a moisture-containing oxygen atmosphere. Superconducting YBCO films have been obtained by performing conversion heat treatment at temperature of $780{\sim}810^{\circ}C$ under a moisture-containing Ar(1,000 ppm oxygen) atmosphere. It has been shown that the critical current($I_c$) of YBCO film was degraded by doping of Ba and Ce atoms. But $I_c$ was increased as the amount of doped Ba and Ce content increased from 5% to 15 %. It was observed that there was little increase of a flux pinning force with Ba and Ce addition in YBCO film prepared by TFA-MOD process.

• 한국초전도ㆍ저온공학회논문지
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• 제6권1호
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• pp.12-17
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• 2004

High critical current density. $J_c$ over $1MA/cm^2$ at 77 K in a self field was successfully achieved from the YBCO film prepared on (100) $SrTiO_3$ single-crystal substrates by the TFA-MOD process. Unlike a normal TFA-MOD process, we prepared the TFA precursor solution by dissolving YBCO powder into the trifluoroacetic acid. A significant amount of the second phases, including $BaF_2$, was observed in the films fired at $700-725^{\circ}C$ for 2 h under $P(O_2)=10^{-3}$ atm and $P(H_2O)=4.2%$, most probably due to an insufficient reaction time, and hence $T_c$ was greatly degraded. However the films fired at $750-800^{\circ}C$ for 2 h were composed of strongly c-axis oriented YBCO grams without any second phases. and exhibited the $T_c$ values of 89.5 ~ 91 K with a sharp transition. With increasing the firing temperature from 750 to $800^{\circ}C$ average grain size of YBCO was increased and grain connectivity was enhanced. The highest $J_c$ value of $1.1MA/cm^2$ was obtained from the YBCO film fired at $800^{\circ}C$.

• 한국초전도ㆍ저온공학회논문지
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• 제8권3호
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• pp.13-17
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• 2006

The effect of the addition of the nano size $Y_2O_3$ powder on the microstructurte and superconducting properties of YBCO thin film deposited on LAO single crystalline substrate by TFA-MOD method was studied. Nano size $Y_2O_3$ powder was added to the stoichiometric precursor solution with a cation ratio of Y : Ba . Cu = 1 : 2 : 3 prepared using TFA as chelating agent. Precursor solutions with and without $Y_2O_3$ addition were coated on $LaAlO_3(100)$ single crystalline substrates by dip coating method. Calcination and conversion heat treatments were performed in controlled atmosphere containing moisture Current carrying capacity(Jc) of YBCO film was enhanced about 50% by $Y_2O_3$ doping and it is thought to be due to the better connectivity of YBCO grains and/or the flux pinning by the $Y_2O_3$ particles embedded in YBCO grains.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2005년도 High Temperature Superconductivity Vol.XV
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• pp.76-76
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• 2005