• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2002년도 High Temperature Superconductivity Vol.XII
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• pp.36-36
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• 2002

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2005년도 High Temperature Superconductivity Vol.XV
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• pp.13-13
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• 2005

• 한국재료학회지
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• 제24권2호
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• pp.116-122
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• 2014

$Bi_2Sr_2CaCu_2O_x$(Bi-2212) and $Bi_2Sr_2Ca_2Cu_3O_y$(Bi-2223) high-Tc superconductors(HTS) have been manufactured by plasma spraying, partial melt process(PMP) and annealing treatment(AT). A Bi-2212/2223 HTS coating layer was synthesized through the peritectic reaction between a 0212 oxide coating layer and 2001 oxide coating layer by the PMP-AT process. The 2212 HTS layer consists of whiskers grown in the diffusion direction. The Bi-2223 phase and secondary phase in the Bi-2212 layer were observed. The secondary phase was distributed uniformly over the whole layer. As annealing time goes on, the Bi-2212 phase decreases with mis-orientation and irregular shape, but the Bi-2223 phase increases because a new Bi-2223 phase is formed inside the pre-existing Bi-2212 crystals, and because of the nucleation of a Bi-2223 phase at the edge of Bi-2212 crystals by diffusion of Ca and Cu-O bilayers. In this study the spray coated layer showed superconducting transitions with an onset Tc of about both 115 K, and 50 K. There were two steps. Step 1 at 115 K is due to the diamagnetism of the Bi-2223 phase and step 2 at 50 K is due to the diamagnetism of the Bi-2212 phase.

• 한국세라믹학회지
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• 제40권5호
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• pp.405-409
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• 2003

The effect of substitution of Gd ions for Ca ions in the B $i_{1.84}$P $b_{0.34}$S $r_{1.91}$(C $a_{1-x}$ G $d_{x}$)$_{2.03}$ C $u_{3.06}$ $O_{ 10+{\delta}}$/ (x=0.0~0.06) was investigated by measuring x-ray diffraction patterns, lattice constants, do resistivity and Hall effect. We found the solubility limit of Gd in the 110 K phase to be x < 0.015. Within the solubility limit, the c-axis seemed to decrease with increasing x. In the region of the 110 K single phase, the critical temperature $T_{c}$ gradually decreased with an increasing the Gd concentration x, corresponding to a small change of the carrier concentration.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 추계학술대회 논문집
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• pp.30-34
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• 2003

For an inhomogeneous superconductor, we reveal a relation of an observed superconducting gap, $\Delta$$_{obs}$ and the intrinsic true gap, $\Delta$$_{i}$, $\Delta$$_{obs}$(equation omitted) where band filling, 0＜$\rho$<$\leq$1. $\Delta$$_{obs}$ is the effect of measurement when 0＜$\rho$＜1. The true gap is observed only when $\rho$=1. Parring symmetry analyzed by a coherence-peak shape of density of states, observed in B $i_2$S $r_2$CaC $u_2$ $O_{8}$＋$\chi$ superconductors, is s- wave.X> $O_{8}$＋$\chi$ superconductors, is s- wave. wave.

• 한국전기전자재료학회논문지
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• 제11권11호
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• pp.1014-1021
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• 1998

We evaluated the effect of processing variables on microstructural evolution interface irregularity between Ag sheath and superconductor core and resultant critical current density(J$_{c}$) of (Bi,Pb)$_2$Sr$_2$Ca$_2$Cu$_3$O$_{x}$(2223) superconductor tape. The value of J$_{c}$ was significantly influenced by the interface irregularity, degree of texturing and relative 2223 content. The interface became more irregular(sausage effect), while the degree of texturing gradually improved as the dimension of tape decreased during forming process. As the dimension of wire/tape were changed from diameter of 3.25 mm to thickness of 0.20 mm, J$_{c}$ value was observed to be increased by 10 times. In addition, optimum sintering temperature for improved J$_{c}$ was observed to be 835$^{\circ}C$ in a ambient atmosphere probably due to combined effect of both improved texturing and high 2223 content. Microstructural investigation showed the degree of texturing was degraded by the existence of both second phases and interface irregularity. It was observed that larger grain size and better texturing was developed near relatively flat interface compared to those inside superconducting core.ting core.

• Progress in Superconductivity
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• 제7권1호
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• pp.1-5
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• 2005

A pseudogap in the normal-state quasiparticle density of states of $high-T_c$ superconductors has been revealed in many different kinds of experiments. The existence of the pseudogap and the superconducting gap, and the correlation between them has attracted considerable attention because they are believed to be a key to understanding the mechanism of the $high-T_c$ superconductivity. The interlayer tunneling spectroscopy, excluding the surface-dependent effect, is one of the most accurate means to examine the electron spectral characteristics both in the superconducting and the normal states. In this study, a new constant-temperature intrinsic tunneling spectroscopic technique, excluding the overheating effect using the in-situ temperature monitoring combined with the digital proportional-integral-derivative control, is introduced. The implication on the $high-T_c$ superconductivity of the detailed temperature dependencies of the observed spectral weight in $Bi_{2}Sr_{2}CaCu_{2}O_{8+x}\;high-T_c$ material for overdoped and underdoped levels is discussed.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 춘계학술대회 논문집
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• pp.252-255
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• 1996

Superconducting current lead is one of the promising applications of the oxide high-Tc superconductors, because they have the advantage of decreasing heat conduction to low temperature region, comparing with a conventional cooper alloy lead. High critical current density is a key factor for the applications such as current lead. (Bi,Pb)$_2$Sr$_2$Ca$_2$Cu$_3$O$\_$x/ high Tc superconductor haute been investigated in terms of critical current density. Bi-2223 superconducting current lead made by CIP and solid state sintering process. Bi-2223 current lead that heat treated at 836$^{\circ}C$ for 240 h in 1/13 P$\_$O$_2$/ had over 150 A/$\textrm{cm}^2$ of critical current density at 77K. We knew that the superconducting properties of tube type current leads were better than rods type of them. And we investigated the relation of Bi-2223 formation and heat treatment condition by XRD and SEM analysis.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 C
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• pp.924-925
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• 1999

Bi-system high-$T_c$ superconductors with the nominal composition $(Bi_{0.7}Pb_{0.3})_2-Sr_{2}Ca_{2}Cu_{3}O_{x}$ have been prepared by PJL method. The critical temperature (offset temperature) of the sample annealed for 13 hours in air was 102K. And the results of X-ray diffraction(XRD) patterns, scanning electron microscope (SEM) images and energy dispersive X-ray (EDX) spectra analyses, it was found that PJL method is so effective to reduce the heat treatment period.

• 수산해양기술연구
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• 제25권3호
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• pp.143-153
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• 1989

산화물 초전도체에 있어서 고천이 임계온도를 갖는 미소영역을 추출하여 이를 분석하기 위하여 La-Ba-Cu-O 계, Y-Ba-Cu-O 계 및 Bi-Pb-Sr-Ca-Cu-O 계의 초전도체를 고상법 및 nitrate solution method로 제조하였다. 제조된 시료들에 대해서 x선회절분석과 저항을 측정하였다. 이들 시료 중에서 고천이온도를 나타내는 미소부분을 Meissner효과를 이용한 추출법으로 분리 해내고 EDAX로 이를 분석하였으며, 이들 결과를 요약하면 다음과 같다. nitrate solution method를 적용하면 YBCO계에 있어서 비교적 단시간에 치밀한 미세조직을 갖는 천이 온도 90K의 초전도체를 제조할 수 있다. Meissner효과를 이용하여 고천이온도에서 추출해낸 미소영역의 EDAX분석 결과는 고상법을 사용한 YBCO-23S와 nitrate solution method으로 제조한 YBCO-23N 및 YBCO-36N 에서는 초기의 조성과 거의 같았으며, 고천이 온도에서 추출된 미소영역은 조성보다는 산소 결함의 차이에 기인한 것으로 생각된다. 공침법으로 제조한 YBCO-23NA 에서는 과도한 Ba의 조성을 보였으며, 천이온도 100K 인 Bi계에서는 약한 반자성효과 때문에 추출이 불가능하였다.