• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2001년도 학술대회 논문집
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• pp.21-24
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• 2001

A series of superconducting Hg$Ba_{2}$Cu$O_{4+7}$ materials, containing $Ag_{x}$ additions with molar fraction x = 0, 0.05, 0.1, 0.3, and 0.5, have been studied. This study has showed that Ag additions lead to changes in superconducting properties of Hg-1201 materials. In addition, according to the amount of $Ag_{x}$ additions with molar fraction x up to 0.5, both $T_{c}$ and $J_{c}$ of Hg-1201 materials generally decrease with Ag-content. These and other results are discussed in this paper.

• 한국초전도ㆍ저온공학회논문지
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• 제2권1호
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• pp.1-6
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• 2000

The effects of partial substitution of fluorine on physical properties were studied in Ag-sheathes tapes of $Tl_{0.8}Pb_{0.2}Sr_{1.8}Ba_{0.2} Ca_{2.2}Cu_3O_yF_x (0{\leq}x{\leq}1)$ nominal compositions. The tapes were prepared using the powder-in-tube method incorporating an in-situ reaction method. $CuF_2$ was used as a source of F. It was found that F-doping in Tl-1223 system resulted in a decrease in formation temperatire of Tl-1223 phase. and thus significantly deteriorated their superconducting properties. Such disadvantages seem to originate by the fromation of non-beneficial phases such as SrF2 in the early stage of the powder preparation process.

• 한국전기전자재료학회논문지
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• 제21권10호
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• pp.950-953
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• 2008

YBCO coated conductor called the second-generation superconducting tapes have resistance increase significantly more than BSCCO tapes in terms of the speed or amount when quench occurs, they may have different ranges of application. Such characteristics are thought to get different properties by selection of stabilizing materials in manufacturing superconducting tapes. It is important in selecting superconducting tapes which will be applied to power devices in the future. In this study, one kind of BSCCO tapes and two kinds of YBCO CC with different stabilizing materials and one kind of YBCO CC with non stabilizing materials were used to compare and examine transport characteristics in flux-flow state and quench state with each tape joint of HTS tapes.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2000년도 High Temperature Superconductivity Vol.X
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• pp.70-75
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• 2000

We report results of a comparative study of the normal-state and superconducting properties in the GdBa$_2$(Cu$_{2.9}$Al$_{0.1}$)O$_z$ system with substitutions by Pr for the Gd and Ba sites. It is observed that, fur both Pr-doped systems, the superconducting transition temperature(T$_c$) decreases almost linearly with the Pr-content, but Pr at Ba sites results in a faster T$_c$ drop than that of Pr at Gd sites. The thermoelectric power measurements indicate that there is a strong correlation between the T$_c$ and the room temperature value of thermoelectric power. The experimental results are discussed in connection with existing models.

• 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.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1992년도 추계학술대회 논문집
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• pp.81-83
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• 1992

The superconducting thin films deposited on $SiO_x$ substrate by R.F magnetron sputter using $YBa_2Cu_3O_x$ single target have been made and annealed at $940^{\circ}C$ for 30 min. The thickness of films were 1000-2000${\AA}$ with a rate of 20-25${\AA}/min$ and superconducting properties of thin films depended on the compositions of pre-annealed the thin films. It has been analyzed by SEM photo-analysis and X-ray diffraction patterns of these samples obtained under the various conditions of this sputtering methods. and recognized the supperconducting thin films by electric properties.

• Progress in Superconductivity
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• 제10권1호
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• pp.17-22
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• 2008

We have examined the effect of ball-milling on the superconducting properties of $MgB_2$ doped with C. The ball-milling of pre-reacted $MgB_2$ powder was carried out in dry or wet state using C or diethylenetriamine ($C_{4}H_{13}N_3$) as additives. The diethylenetriamine, whose chemical formula contains no oxygen, was chosen to avoid an excess oxidation during doping. The superconducting transition temperature (Tc) of the ball-milled or doped $MgB_2$ powders was only slightly smaller than that of undoped $MgB_2$. The critical current density (Jc) of the highly ball-milled $MgB_2$ was higher than that of C-doped $MgB_2$. The addition of diethylenetriamine was detrimental to Jc, although Tc was almost unchanged.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권7호
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• pp.315-319
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• 2003

We improved quench properties of a superconducting fault current limiter (SFCL) based on YBCO thin films by their serial and parallel combinations. The SFCL consisted of 6 switching elements fabricated of 4 inch-diameter YBCO thin films. The quench currents of the switching elements were distributed between 33.9 A and 35.6 A. Simple serial connection resulted in imbalanced power dissipation between switching elements even at the quench current difference of 0.6 A. On the other hand, $2{\times}2$ and $3{\times}2$ stack combinations produced simultaneous quenches. The $3{\times}2$ stack combination showed better simultaneous quench behavior than the $2{\times}2$ stacks. This is suggested to be because the currents between switching elements in parallel connection of the $3{\times}2$ stacks were more effectively redistributed than the $2{\times}2$ stacks.

• 한국세라믹학회지
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• 제28권1호
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• pp.37-45
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• 1991

The critical current density, electrical conductivity, critical magnetic field, Meissner effect, apparent density, and microstructure of YBa2Cu3O7-x ceramic superconductor prepared by polymeric precursor, while varing calcining and sintering conditions, were investigated. The best superconducting properties could be obtained from the body sintered at 93$0^{\circ}C$ for 10h after calcining at 90$0^{\circ}C$ for 10h, which gave 383A/$\textrm{cm}^2$ of critical current density(Jc), 96K of onset temperature(Tonset), 94. 8K of zero temperature (Tzero) 225 Oe of critical magnetic field (Hc1), 72.8% of superconducting volume fraction measured by Meissner effect and 6.28g/㎤ of apparent density.

• 한국초전도ㆍ저온공학회논문지
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• 제19권3호
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• pp.23-26
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• 2017

We have studied magnetic and transport properties of NbN/FeN/Cu/FeN/FeMn spin-valve structure. In-plane magnetic moment exhibited typical hysteresis loops of spin valves in the normal state of NbN film at 20 K. On the other hand, the magnetic hysteresis loop in the superconducting state exhibited more complex behavior in which exchange bias provided by antiferrmagnetic FeMn layer to adjacent FeN layer was disturbed by superconductivity. Because of this, the ideal superconducting spin-valve effect was not detected. Instead the stray field originated from unsaturated magnetic states dominated the transport properties of NbN/FeN/Cu/FeN/FeMn multilayer.