• 제목/요약/키워드: superconducting transition

검색결과 228건 처리시간 0.029초

초전도 결정의 저온 비열 점프의 자기장 의존성 (Magnetic Field Dependence of Low Temperature Specific Heat Jump in Superconducting Crystal)

  • 김철호
    • 한국재료학회지
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    • 제21권2호
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    • pp.73-77
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    • 2011
  • Specific heat of a crystal is the sum of electronic specific heat, which is the specific heat of conduction electrons, and lattice specific heat, which is the specific heat of the lattice. Since properties such as crystal structure and Debye temperature do not change even in the superconducting state, the lattice specific heat may remain unchanged between the normal and the superconducting state. The difference of specific heat between the normal and superconducting state may be caused only by the electronic specific heat difference between the normal and superconducting states. Critical temperature, at which transition occurs, becomes lower than $T_{c0}$ under the influence of a magnetic field. It is well known that specific heat also changes abruptly at this critical temperature, but magnetic field dependence of jump of specific heat has not yet been developed theoretically. In this paper, specific heat jump of superconducting crystals at low temperature is derived as an explicit function of applied magnetic field H by using the thermodynamic relations of A. C. Rose-Innes and E. H. Rhoderick. The derived specific heat jump is compared with experimental data for superconducting crystals of $MgCNi_3$, $LiTi_2O_4$ and $Nd_{0.5}Ca_{0.5}MnO_3$. Our specific heat jump function well explains the jump up or down phenomena of superconducting crystals.

61심 BSCCO 2223 고온초전도 선재의 접합부 제조 (Fabrication of Superconducting Joints between 61 Filaments of BSCCO 2223 Tapes)

  • 김철진;박성창;유재무
    • 한국세라믹학회지
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    • 제35권2호
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    • pp.137-144
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    • 1998
  • 고온초전도체 61심 Bi-2223 선재간의 초전도 접합부위를 화학적 부식 및 열적· 기계적 반복 공정에 의하여 제조하였다. 초전도 선재 테이프의 은 피복재 한쪽 표면을 초전도체와 반응하지 않는 부식액(NH4OH:H2O2=1:1)으로 화학적으로 제거한 다음, 두 시편을 일출가압 성형하여 접합시편을 제조하였고 일련의 서로 다른 열적· 기계적 처리를 거쳐 접합부의 물성 및 미세구조를 분석하였다. 접합부를 따라 임계전류(Ic) 변화와 전류전압 곡선의 특성을 측정하기 위하여 여러 단자를 접합부 주위에 설치하여 부위별 I~V 특성을 측정한 결과 단심선재에 비하여 다심선재에서 선재 전체의 통전 능력을 좌우하는 천이구간의 임계전류값이 높았다. 그러나 단심에 비해 다심선재는 천이급속도를 나타내는 n값이 다심선재내 각각의 초전도 core들의 상호작용에 의하여 낮은 값을 나타내었다. 접합부의 임계전류 통전성은 반복적인 가압성형 공정과 서냉반응 열처리 공정에 의하여 향상되었다.

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Superconducting transitions of LuBa2Cu3O7-z heated under various atmospheres

  • Lee, M.S.;Lee, H.K.
    • 한국초전도ㆍ저온공학회논문지
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    • 제16권1호
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    • pp.6-8
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    • 2014
  • The influence of quenching temperature, heating atmosphere and annealing time on superconducting characteristics has been studied for $LuBa_2Cu_3O_{7-z}$ compound which has been recently synthesized in a nearly phase-pure form. Resistivity measurements for the as-prepared sample heated at $300^{\circ}C$ in oxygen and subsequently quenched into liquid nitrogen revealed that there is no significant change in $T_c$. On the other hand, $T_c$ of the sample slightly increased when the sample was heated at $300^{\circ}C$ either in air or in $N_2$ atmosphere. It was also found that $T_c$ of the sample decreased when the annealing temperature in $N_2$ atmosphere increased above $400^{\circ}C$. The experimental results indicated that the as-prepared sample is under overdoped state. The enhanced superconducting transition observed in the samples after heating at $300^{\circ}C$ in air or $N_2$ atmosphere was discussed in conjunction with a slight removal of oxygen and ordering of oxygen atoms in the as-prepared sample.

레이저 공정을 이용한 고온초전도 멀티플렉서의 제작과 특성 분석 (Investigation of Characterization and Fabrication High-Temperature Superconducting Multiplexer by Pulse laser Deposition)

  • 김철수;송석천;이상렬
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1999년도 하계학술대회 논문집 D
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    • pp.1858-1860
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    • 1999
  • To fabricate superconducting multiplexers with narrow pass band characteristics and reduce the physical size of device, we have designed multiplexer using hair-pin type filters with the center frequency of 13.6 GHz. Multiplexers have been fabricated superconductor(HTS), because It has low surface resistance. The $YBa_2Cu_3O_{7-{\delta}}$(YBCO) films were deposited on MgO substrates$(20{\times}20{\times}0.5mm^3)$ by using pulsed laser deposition and conventional photo-lithographic methods were used to pattern the multiplexer. Epitaxial YBCO films were grown on(100) MgO substrates and showed strongly c_axis orientations observed by X-ray diffraction technique. Superconducting transition temperatures were measured to be about 89K. Simulated results of superconducting multiplexer consisting of hair-pin type filters show the insertion loss of about 1.2dB. The measured frequency response will be compared with the simulated results.

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PSCAD/EMTDC를 이용한 저항형 초전도한류기의 계통적용분석 연구 (A Study on the Application Analysis of the Resistive type Superconducting Fault Current Limiters using PSCAD/EMTDC)

  • 허태전;방종현;배형택;박민원;유인근
    • 한국초전도ㆍ저온공학회논문지
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    • 제7권1호
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    • pp.25-31
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    • 2005
  • Since the discovery of the high temperature superconductors many researches have been performed for the practical applications of superconductivity technologies in various fields. As results, significant progress has been achieved. Especially, Superconducting Fault Current Limiter (SFCL) offers an attractive means In limit fault current in power systems. HTS resistive type SFCL is based on the ultra fast transition from the superconducting (non resistive) state to the normal (resistive) state by overstepping the critical current density, In this study, the simulation method of resistive type superconducting fault current limiter using EMTDC is proposed and the developed EMTDC model of SFCL is applied to the modeled power network using the Parameters of real system.

Superconducting transition in the Presence of Magnetic order in BaFe1.89Co0.11As2

  • Kim, K.W.;Wolf, T.;Bernhard, C.
    • 한국초전도ㆍ저온공학회논문지
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    • 제17권4호
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    • pp.21-24
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    • 2015
  • We report optical spectra of underdoped $BaFe_{1.89}Co_{0.11}As_2$ that hosts both of magnetic and superconducting orders. The temperature dependent evolution of optical conductivity shows finger prints of the magnetic order and the s-wave nature of the superconducting gaps. Careful inspection on the superconducting state reveals that the two orders compete but coexist in the ground state.

Enhanced Superconducting Properties in Melt-processed (Y0.33Sm0.33Nd0.33) Ba2Cu3Oy Oxides in Air

  • Kim, So-Jung;Park, Jong-Kuk
    • Transactions on Electrical and Electronic Materials
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    • 제6권6호
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    • pp.284-288
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    • 2005
  • We have systematically studied the superconducting properties and flux pinning enhancement of $(Y_{0.33}Sm_{0.33}Nd_{0.33})\;Ba_2Cu_3O_y$ [(YSN)-123] composite oxides by melt growth process in air. A sample prepared by this method showed well-textured microstructure, and $(Y_{0.33}Sm_{0.33}Nd_{0.33})\;BaCuO_5$ [(YSN)211] nonsuperconducting particles were uniformly dispersed in large (YSN) 123 superconducting matrix. The sample showed a sharp superconducting transition at 91 K. The magnetization measurements of the (YSN)-123 sample exhibited the enhanced flux pinning, compared with $YBa_2Cu_3O_y$ (Y-123) sample without Sm and Nd. Critical current densities of (YSN)-123 sample was $2.5{\times}10^4 A/cm^2$ at 2 T and 77 K.

나노구조 박막의 Morphology에 따른 초전도 특성 변화에 관한 연구 (Effects of Morphology on Nanostructured Superconducting Thin Film)

  • 고태준
    • 한국자기학회지
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    • 제16권1호
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    • pp.71-74
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    • 2006
  • 나노구조 초전도 박막의 모폴로지를 열처리를 통해 변화시키며 이에 따른 박막의 초전도 특성을 면저항과 터널링 측정을 통해 연구하였다. 면저항 측정결과 초전도 박막의 임계온도가 열처리 온도에 따라 증가함을 알 수 있었다. 터널링 측정방법을 통해 포논 스펙트럼을 분석한 결과 열처리 후 횡 포논 모드에 변화가 나타남을 알 수 있었다. 이러한 결과들을 통해 나노구조 박막의 모폴로지가 박막의 초전도 특성에 미치는 영향을 이해할 수 있다.

Bi system bulk의 superconducting properties (A Study on the Superconducting prperties of Bi system bulk)

  • 이상헌
    • 전기학회논문지
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    • 제59권2호
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    • pp.352-354
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    • 2010
  • The effects of Au addition on the structure and the superconducting properties of Bi system bulk have been investigated. Au exists in the metalic form in above materials. It does not affect the formation and structure of the BiSrCaCuO(2223) phase. The superconducting transition temperature Tc does not change for $Bi_{1.7}Pb_{0.3}Sr_2Ca_2Cu_3O$ composite However Au doping can make the grains smaller. Metallic Au can make gathers on the grains boundary and lead to the increment of critical transport current density. The current density of $Bi_{1.7}Pb_{0.3}Sr_2Ca_2Cu_3Au_{0.5}O$ was 1000A/$cm^2$ at liquid nitrogen temperature.

고온초전도동기모터의 전기적 손실에 따른 회전자의 유로 설계에 관한 연구 (A Study on the Analysis for Fluid Path Design of the Rotor considering Electrical Losses of High-Tc Superconducting Synchronous Motor)

  • 윤용수;송명곤;장원갑;장인배;이상진;고태국
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1998년도 하계학술대회 논문집 A
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    • pp.98-100
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    • 1998
  • This paper presents the fluid characteristics simulation and design guide line of the fluid path inside the rotor, which has an high-Tc superconducting field winding using Ag sheathed BSCCO-2223. The analysis was conducted with an equivalent model of the high-Tc superconducting synchronous motor under transition condition that occurs during the load varying from 250watt to 500watt. The results show that the designed fluid circulation system performs adequately in maintaining the superconducting state in the winding.

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