• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.1
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• pp.89-94
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• 2007

High duality BiSrCaCuO thin films fabricated by using the i-beam sputtering method at various substrate temperatures, $T_{sub}$ and oxidation gas pressures, $pO_3$. The correlation diagrams of the BiSrCaCuO phases with Tsub and $pO_3$ are established in the 2212 and 2223 compositional films. In spite of 2212 compositional sputtering, Bi2201 and Bi2223 as well as Bi2212 phases come out as stable phases depending on $T_{sub}$ and $pO_3$. From these results, the thermodynamic evaluation of ${\Delta}H$ and${\Delta}S$, which are related with Gibbs' free energy change for single Bi2212 or Bi2223 phase, was performed.

• Progress in Superconductivity
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• v.10 no.2
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• pp.128-132
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• 2009

Polycrystalline samples of $(Ru_{0.8}Nb_{0.2})Sr_2(Gd_{1.5-x}Nd_xCe_{0.5})Cu_2O_z$($ 0{\leq}x{\leq}1.25$) have been synthesized by a solid-state reaction route. The X-ray diffraction data revealed that the Nd solubility limit can be placed between x=0.5 and x=0.75. The superconducting transition temperature decreased with increasing Nd content, confirming that Nd entered the lattice. Room-temperature thermoelectric power measurements showed that all the samples are in the underdoped state and the partial substitution of Nd for Gd resulted in a decrease in the carrier density on the superconducting layers.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.7
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• pp.766-772
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• 1992

Bi-Sr-Ca-Cu-O superconducting system has both the low and high Tc phases. We added Pb and sintered for 200hrs. in OS12T atmosphere in order to get the superconductor above critical temperature 100K. Superconducting properties of the Bi(Pb)SrCaCuO system doped Sb were also investigated. When Sb of 0.1mol is added, the sintering time becomes shorter than that doped Pb only. We could get the critical temperature 102K at the samples sintered for 24hrs. and 109K for 210hrs.

• Electrical & Electronic Materials
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• v.5 no.2
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• pp.175-181
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• 1992

Y-Ba-Cu-O계 보다 화학적 내구성이 좋은 Bi-Sr-Ca-Cu-O계 초전도체 wire를 중합 binder와 초전도체 파우더를 혼합하여 sol-gel법으로 제조하였다. 여러가지 혼합비와 열처리 조건하에서 제조한 wire의 특성분석 결과 Bi$_{2}$Sr$_{2}$Ca$_{2}$Cu$_{3}$O계 초전도체와 binder의 최적 혼합율은 22.25%이었고 가열비는 0.33.deg.C/min로 500.deg.C까지는 Ar gas와 $O_{2}$ gas분위기로 열처리하고 500.deg.C에서 835.deg.C까지는 $O_{2}$ gas분위기에서 40h동안 열처리하였을때 임계온도 98K를 갖는 초전도 선재를 얻을 수 있었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1993.05a
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• pp.22-27
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• 1993

we prepared 70K new BiPbAgSrCaCuO superconductor used diffusion of dual layer which composed of SrCaCuO and BiPbAgCuO compound. This method is used permeation and diffusion on partial melting point of BiPbAgCuO compound. Samples were analyzed by means of X-ray diffraction analysis, Thermal analysis, critical temperature and scanning electron microscopy. It was found that the best results were obtained for spread volume (A:B=1:0.6) and sintring time 210hours.

• 한국초전도학회:학술대회논문집
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• v.15
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• pp.40-40
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• 2005

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.1208-1211
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• 2003

High quality $Bi_2Sr_2Ca_nCu_{n+1}O_x$ superconducting thin films fabricated by using the evaporation method at various substrate temperatures, $T_{sub}$, and ozone gas pressures, $pO_3$. The correlation diagrams of the $Bi_2Sr_2Ca_nCu_{n+1}O_x$ phases with $T_{sub}$ and $pO_3$ are established in the 2212 and 2223 compositional films. In spite of 2212 compositional sputtering, Bi2201 and Bi2223 as well as Bi2212 phases come out as stable phases depending on $T_{sub}$ and $pO_3$. From these results, the thermodynamic evaluation of ${\Delta}H$ and ${\Delta}S$, which are related with Gibbs' free energy change for single Bi2212 or Bi2223 phase, was performed.

• Korean Journal of Materials Research
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• v.17 no.3
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• pp.147-151
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• 2007

Cu-free multi-component sol, of which final oxide composition becomes $Bi_{1.9}Pb{0.35}SrCaO,\;Bi_{1.8}Pb_{0.2}SrCaO\;and\;Bi_{1.5}SrCaO$, respectively, was prepared through sol-gel route and coated on a bare Cu substrate. Starting materials were metal-alkoxides as follows.; [$Bi(OC_{2}H_{5})_{3}\;Pb(O^{1}C_{3}H_{7})_{2},\;Sr(O^{i}C_{3}H_{7})_{2},\;Ca(OC_{2}H_{5})_{2}$] as a reagent grade. Transparent light yellowish sol was obtained in the case of $Bi_{1.9}Pb_{0.35}SrCaO\;and\;Bi_{1.8}Pb_{0.2}SrCaO$ composition and $Bi_{1.5}SrCaO$ composition's sol was light greenish. Each sol was repeatedly dip-coated on Cu substrate four times and pre-heated at $400^{\circ}C$ and finally heat-treated in the range of $740{\sim}900^{\circ}C$. In the results, crystalline phases confirmed by XRD were (2201) orthorhombic and monoclinic phases. However, only $Bi_{1.9}Pb_{0.35}SrCaO_{x}$ composition showed pseudo-superconductive behavior after heat-treatment at $900^{\circ}C$ for 12 seconds and then onset temperature was 77 K, even though it did not exhibit zero resistance below Tc.

• 한국초전도학회:학술대회논문집
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• v.10
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• pp.103-106
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• 2000

We have studied the magnetic properties in Bi$_2$Sr$_2$CaCu$_2$O$_8$ single crystal with columnar defects using micro Hall-probe array. We found that fold profiles inside sample were similar to the Bean's critical state model from the magnetic hysteresis measurement. In the magnetic relaxation measurement, the normalized relaxation rates were maximum near the center and decreased toward the edge of the sample expect zero gauss. The relaxation rates as a function of the temperature were maximum near the 40K and rapidly decreased both sides of the peak.

• Journal of the Korean Vacuum Society
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• v.3 no.1
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• pp.117-121
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• 1994

SrTiO3(100) 단결정을 3keV 아르곤이온으로 에칭하면 표면원소의 산화 상태가 환원되고 표면의 거칠기가 증가하는 것이 XPS와 SEM으로 측정되었다. 그러나 3keV의 산소이온으로 에칭하면 표면원소 의 화학적 상태도 변하지 않고 표면도 평탄한 상태로 계속 유지된다. 산소 이온에 의하여 에칭된 SrTiO3 기판상에 off-axis rf 스퍼트링 방법으로 성장된 YBa2Cu3Ox 박막이 아르곤 이온에 의하여 에칭 된 SrTiO3 기판상에 성장된 YBa2Cu3Ox 박막보다 높은 Tc,zero and Jc를 보여주었다. 이논문은 YBCO초전 도 박막의 성장과 전자공학적 활용을 위한 리토그라피 공정에서 이온밀링 공정의 조건은 매우 주의하여 선택되어야 함을 보여준다.