• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2005년도 High Temperature Superconductivity Vol.XV
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• pp.69-69
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• 2005

• Progress in Superconductivity
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• 제5권1호
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• pp.1-4
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• 2003

A five-year project for Nb-based single flux quantum (SFQ) circuits supported by Japan's Ministry of Economy Trade and Industry (METI) in Japan was started in September 2002. Since April 2003, the New Energy and Industrial Technology Development Organization (NEDO) has supported this Superconductor Network Device Project. The aim of the project is to improve the integration level of Nb-based SFQ circuits to several ten thousand Josephson junctions, in comparison with their starting integration level of only a few thousand junctions. Actual targets are a 20 GHz dual processor module for the servers and a 0.96 Tbps switch module for the routers. Starting in April 2003, the Nb project was merged with SFQ circuit research using a high-T$_{c}$ superconductor (HTS). The HTS research targets are a wide-band AD converter for mobile-phone base stations and a sampling oscilloscope for wide-band waveform measurements.

• Progress in Superconductivity
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• 제3권1호
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• pp.41-44
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• 2001

We report the current transport properties of a normal metal/organic conductor/ superconductor tunnel junction as a novel high- $T_{c}$ superconducting three terminal device. The organic copper (II) phthalocyanine (Cu-Pc) layer was used far a polaronic quasiparticle (QP) injector. The injection of polaronic QP from the Cu-Pc interlayer into a superconductor $Bi_2$$Sr_2$$CaCu_2$ $O_{8+}$ $\delta$/(BSCCO) thin film generated a substantially larger nonequilibrium effect as compared to the normal QP injection current. The tunneling spectroscopy of an Au/cu-PC/BSCCO junction exhibited a zero bias conductance peak which may be due to Andreev reflection at a Cu-Pc/d-wave superconductor junction.n..

• 한국자기학회지
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• 제1권2호
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• pp.15-21
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• 1991

고온초전도체 $Y_{1}Ba_{2}Cu_{3-x}Sn_{x}O_{7-y}$에서 Cu 대신에 Sn 을 치환하면서 이들의 조성변화에 따른 자기적 특성을 vibrating sample magnetometer(VSM)와 torque magnetometer를 이용 하여 측정하였다. Cu 대신에 Fe, Ni 등의 원소를 치환했을 때와는 달리 x=0.36 까지 되어도 초전도 전이온도가 90 K 이상을 나타냄을 알 수 있었다. 온도와 외부자기장에 따른 자기 모우먼트 측정을 통하여 각 조성에 따른 lower critical field ($H_{c1}(T)$)과 upper critical field ($H_{c2}(T)$)를 측정하였다. 이 결과를 이용해 $H_{c1}(0)$과 $H_{c2}(0)$를 계산했으며, 간섭길이 (${\varepsilon}_{0}$), 침투깊이 (${\lambda}_{0}$), Ginzburg-Landau 상수 k등을 얻을 수 있었으며, 시료의 flux pinning 효과도 확인할 수 있었다.

• 한국초전도ㆍ저온공학회논문지
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• 제17권4호
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• pp.25-29
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• 2015

In 1987, M. K. Wu and Paul Chu discovered $Y_{1.2}Ba_{0.8}CuO_4$ (YBCO) with critical temperature ($T_c$) of 93 K. It has significantly lowered the cost of cooling of a material up to the point where superconductivity set in. Utilizing the cost reduction of attaining superconductivity and the vast amount of research to understand characteristics of high temperature oxide superconducting materials, there has been effort to use a high temperature superconductor as a coated conductor. It is important to characterize the materials precisely for stable performance before commercializing. We used polarized Raman scattering spectroscopy to study structural and stoichiometric information regarding $YBa_2Cu_3O_{7-x}$, $GdYBa_2Cu_3O_{7-x}$, and $GdBa_2Cu_3O_{7-x}$ produced by three leading groups of producing commercial grade high temperature superconductor coated conductors American Superconductor Corporation, Superpower, and SuNAM.

• 한국표면공학회지
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• 제29권5호
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• pp.415-423
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• 1996

Thin film technologies for fabricating SQUIDs involve etching and deposition procedures with the proper substrate materials and $YBa_2Cu_3O_{7-d}$ (YBCO) as the high $T_c$ superconductor. YBCO were prepared on various substrates of MgO, $SrTiO_3$, and $LaAlO_3$ by using off-axis magnetron sputtering methods and annealing in-situ. The parameters of film fabrication processes had been optimized to yield good quality films in terms of the critical temperature $T_c$ and the critical current density $J_c$. The optimized processes yielded $T_C$>90K along with $J_c$>$10_6A$$extrm{cm}^2$ at 77K and>$2\times10_7A/Cm^2$ at 5K. We fabricated step-edge type dc-SQUIDs and directly coupled magnetometers, producing step edges on MgO(100) substrates by etching with Ar-ion beam, depositing YBCO material on them, then patterning them by using ion-milling technique. Circuitizing washer-shape SQUIDs to possess a pair of step-edge junctions of 2-5$\mu$ line width with a high angle>$50^{\circ}C$ , we examined their I-V characteristics thoroughly and Shapiro steps clearly as we irradiate microwaves of 8-20 GHz frequency.

• Progress in Superconductivity
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• 제12권1호
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• pp.1-5
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• 2010

In this work we synthesized both MgB2 and Carbon doped MgB2 superconductor with Ag addition via high energy milling and substituent heat treatment. Heat treatments were performed at $900\;^{\circ}C$ for 30 min in flowing Ar gas. We varied amount of Ag powder. In a range of Ag powder was 0~5wt%. The effect of Ag was correlated with superconducting properties. The results show a slight decrease in critical temperature ($T_c$) and a reduction of critical current density ($J_c$) at high fields for the Ag-doped samples as compared to the un-doped samples. Reduction of $J_c$ may be due to the formation of MgAg compound.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2008년도 Asian Magnetics Conference
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• pp.107.1-107.1
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• 2008

• 한국초전도ㆍ저온공학회논문지
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• 제12권2호
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• pp.9-12
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• 2010

A lamination system using reflow soldering was developed to enhance the mechanical properties of high temperature superconductor (HTS) tape. The laminated coated conductor tape was fabricated using the continuous lamination process. The mean, maximum, and minimum tensile loads in a T-peel test of the laminated coated conductor were 9.9 N, 12.5 N, and 7.6 N, respectively. The critical current ($I_c$) distributions of the non-laminated and laminated coated conductor were compared using anon-contact Hall probe method. The transport $I_c$ nearly matched the non-contact $I_c$; however, some degraded Ic regions were found on the length of 800 cm of laminated coated conductor. We confirmed that the cause of the partially degraded $I_c$ was due to an increase in line tension by (1) solidification induced by a change of composition that usually occurs in molten brass (Cu, Zn) in solder, or (2) non-homogeneity of the thickness of the coated conductor or metal tapes. We suggest that reflow soldering is a promising method for reinforced HTS tape if the controlling solder thickness and lamination guide are modified.

• 한국결정성장학회지
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• 제14권2호
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• pp.68-72
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• 2004

Sm 원소가 첨가된 $(Sm/Y)_{1.8}Ba_{2.4}Cu_{3.4}O_{7-x}$[이하 (Sm/Y)1.8] 고온초전도체를 국부용융성장법을 이용해 대기 중에서 용융성장실험을 하였다. 초기 (Sm/Y)1.8 초전도체 시편은 rubber 몰드를 이용해 냉간정수압성형(CIP) 과정을 거쳐 길이 방향 원통형상으로 제조되었다. 이렇게 얻어진 (Sm/Y)1.8 초전도체는 용융온도 및 성장속도에 따라 광학현미경, TEM그리고 SQUID magnetometer를 이용해 미세구조 및 초전도특성을 평가하였다. 이 결과 (Sm/Y)1.8 초전도체의 최적의 용융온도 및 성장속도는 $1085^{\circ}C$에서 3.5mm/hr로 나타났다. 특히 일방향으로 용융성장된 (Sm/Y)1.8 초전도체의 광학현미경 및 TEM에 의하 미세구조 관측 결과, 초전도상인 (Sm/Y)123 matrix내에 비초전도상인 (Sm/Y)211 inclusions이 균질하게 분포되어 있는 것이 관측되었다. 초전도특성을 평가한 결과 용융성장된 (Sm/Y)1.8초전도체는 90K에서 임계온도가 시작되어 77K이상의 온도에서 포화되는 특성을 보였다.