• 한국세라믹학회지
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• 제31권10호
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• pp.1123-1132
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• 1994

Bi-Sr-Ca-Cu-O superconductor thin films were prepared on MgO and LaAlO3 substrates by MOCVD technique. The films deposited on MgO and LaAlO3 substrates became superconducting at 64 K and 70 K respectively. The measured critical current density of thin film deposited on LaAlO3 substrate was around 104 A/$\textrm{cm}^2$. After annealing at $700^{\circ}C$ for 3 hours, the critical transition temperature(Tc) of films deposited on LaAlO3 was changed from 70 K to 74 K.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2000년도 KIASC Conference 2000 / 2000년도 학술대회 논문집
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• pp.85-88
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• 2000

Cu-free Bi-Sr-Ca-O powder mixtures were screen-printed on Cu tapes and heat-treated at 850-$870^{\circ}C$ for several minutes in air, oxygen, nitrogen and low oxygen pressure. Cu-free precursors were composed of Bi_{x}$SrCaO_{y}$ (x=1.2-2). In order to obtain the optimum heat-treatment condition, we studied on an effect of the precursor composition, the printing thickness and the heat-treatment atmosphere on the superconducting properties of Bi2212 films and the reaction mechanism of their rapid formation. Microstructures and phases of thick films were analyzed by optical microscope and XRD. The electric properties of superconducting films were examined by the four probe method. At heat-treatment temperature, the thick films were in a partially molten state by liquid reaction between CuO in the oxidized copper tape and the precursors which were printed on Cu tapes.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 C
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• pp.915-917
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• 1999

We investigated the effects of doping elements on the Bi system superconductor. The doping elements can be classified into two groups depending on their supeconducting characteristics in the Bi-Sr-Ca-Cu-O structure. The first group of doping elements(P and K) have a tendency to decompose the superconducting phase and reduce the optimal sintering temperature. The second group of doping elements(B, Si, Sn and Ba) almost uneffected the superconductivity of the 2223 and 2212 phase.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2002년도 학술대회 논문집
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• pp.98-100
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• 2002

We developed the Centrifugal Forming Process(CFP) for HTS tube fabrication. The self-designed equipment for CFP is devided into 3 main parts depending on its role and functions. the melting part by heating of high inductive frequency, centrifugal forming part for the tube and efficient microstructure control of Bi2212 phase and molding part for tube detachment after heat treatment. In this paper we will introduce self designed Centrifugal Forming Process for HTS tube fabrication and discuss about the results related mold materials in terms of high Tc superconductor.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2007년도 High Temperature Superconductivity Vol.XVII
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• pp.13-13
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• 2007

• Progress in Superconductivity
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• 제5권1호
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• pp.5-8
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• 2003

We studied the effect of spin injection on tunneling conduction properties of intrinsic Josephson junctions formed in $Bi_2$$Sr_2$$CaCu_2$$O_{ 8＋x}$ single crystals. properties of an identical stack (10${\times}$5.0${\times}$0.030 $\mu\textrm{m}^3$) of intrinsic Josephson junctions were compared for the bias current injected through Au and Co electrodes. The suppression of the superconducting gap in the $_2$ double layers and the interlayer Josephson critical current was manifested in the tunneling current-voltage characteristics of the stacks. This effect appears to be caused by the pair breaking associated with spin-polarized carriers injected from the Co electrode into the $Bi_2$$Sr_2$$_2$O$CaCu_{ 8＋x}$ single crystal. This study may provide valuable information on clarifying the mechanism of high- $T_{c}$ superconductivity.y.y.

• Progress in Superconductivity
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• 제3권2호
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• pp.140-145
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• 2002

An enhancement of the c-axis differential conductance around the zero-bias voltage near the superconducting transition temperature $T_{c}$ has been observed in $Au/Bi_2$$Sr_2$$CaCu_2$$O_{8+x}$ junctions. We attribute such an enhancement to the Andreev reflection (AR) between the surface Cu-O bilayer with suppressed superconductivity and the next superconducting Cu-O bilayer. The continuous evolution of the differential conductance, from gap like depression to an AR-like peak structure, around the zero-bias voltage points to weakening of the barrier strength of the nonsuperconducting layer between adjacent Cu-O bilayers as temperature approaches $T_{c}$ from below. The peak structure disappeared just below the bulk $T_{c}$ value of underdoped Bi2212 single crystals, whereas it survived up to ~1 K above $T_{c}$ in Junctions prepared on slightly overdosed crystals. According to a recently proposed theoretical consideration, a wider temperature range of the AR a bone $T_{c}$ is expected in the underdoped regime when phase-incoherent preformed pairs emerge in the pseudogap state. Our result is in contradiction to the preformed pair scenario. scenario.o.

• Progress in Superconductivity
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• 제3권1호
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• pp.36-40
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• 2001

We have studied vortex dynamics in$ Bi_2$$Sr_2$$CaCu_2$O$_{8}$single crystals of unirradiated and irradiated samples by using 100 $\times$ $100\mu\textrm{m}^2$Hall sensor. Doses equivalent magnetic fields are 20 G, 100 G and 1 kG. In the magnetization measurement, a second magnetization peak (SMP) was observed in unirradiated, 20 G dose and 100 G dose samples in contrast to 1 kG dose sample. In the unirradiated sample, the SMP was observed in the range of 18 K ~ 35 K and the amplitude of the SMP decreased with increasing temperature. With increase of the irradiation dose, temperature region and sharpness of the SMP were reduced. In the magnetic relaxation measurement, we observed that the normalized relaxation rate S decreased with increasing the irradiation dose. Our results suggest that the vortex dynamics is not greatly affected by low-density columnar defects.s.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2006년도 High Temperature Superconductivity Vol.XVI
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• pp.85-85
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• 2006

• Bulletin of the Korean Chemical Society
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• 제23권9호
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• pp.1304-1323
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• 2002

Superconducting BiSrCaCu(Ni)O ceramicss have been prepared by the gel method using an aqueous solution containing a tartaric acid. The aqueous solution of metal salts was concentrated without precipitation. The precursor so prepared was homogeneou s and calcined at $825^{\circ}C$ for 24 h to produce superconducting phase. The thermal decomposition of gels, the formation of superconducting phase, and their ceramic microstructure were studied using IR, TGA, XRD, resistance measurements, and SEM. This method is highly reproducible and leads to powders with excellent homogeneity and small particle size for easy sinterability. The nickel dopant substituting for Cu gives rise to the gradual decrease of the Tc. Phase pure 2212 ceramics were obtained at 825 $^{\circ}C$ for 24 h. SEM pictures showed that liquid phase was formed when the samples were sintered temperatures higher than 825 $^{\circ}C$.