• 제목/요약/키워드: ${\Delta}nd$

검색결과 130건 처리시간 0.029초

NdBCO 벌크 HTS 초전도 특성 (Superconducting Properties of NdBCO Bulk HTS)

  • 소대화;이영매;번점국
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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    • pp.91-94
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    • 2002
  • The conditions of zone-melting method such as a sample travel speed in a furnace, content of Nd422, control of melting temperature, and heat-treatment with/without Ar gas for $NdBa_{2}Cu_{3}O_{7-\delta}$ superconductor was optimized, As a results, a $NdBa_{2}Cu_{3}O_{7-\delta}$ sample with a surface area of $25mm^{2}$ showed a good superconducting properties when its travel speed was 6 mm/h, The improvement of superconductivity added with 10~20 wt% of Nd422 phase increasing pinning effect was also shown. The critical current density, $J_{c}$ was remarkable affected by the condition of heat-treatment temperature of $NdBa_{2}Cu_{3}O_{7-\delta}$superconductor with/without Ar ambient gas.

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수렴성전자회절에 의한 n-형 세라믹 초전도체 $Nd_{2-x}Ce_xCuO_{4-\upsilon}$의 결정구조 전이 연구 (Inestigation on the Structural Transition of n-type Ceramic Superconductor, $Nd_{2-x}Ce_xCuO_{4-\upsilon}$ System of CBED)

  • 김정식;유광수
    • 한국세라믹학회지
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    • 제34권2호
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    • pp.139-144
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    • 1997
  • 결정학적으로 T' 구조인 Nd2-xCexCuO4-$\delta$ 회토류 구리산화물 초전도체는 지금까지 매우 복잡한 미세구조를 지닌 것으로써 잘 알려져 있다. 이 구리산화물 초전도체가 초전도 특성을 띠려면, Nd3+ 이온이 Ce4+ 이온에 의해 소량 치환되고 동시에 산소환원이 필요하다. 본 연구에서는 투과전자현미경의 수렴성 전자회절(CBED)패턴을 이용하여 Nd2-xCexCuO4-$\delta$ 의 Ce 미량 첨가와 미량의 산소환원에 따른 결정구조의 전이 발생 여부에 관하여 고찰하였다. 세 가지의 서로 다른 시편 Nd2CuO3,Nd1.85Ce0.15CuO4 와Nd1.85Ce0.15CuO3.965을 고상소결에 의하여 만들어 이들 각각 시편에 대한 CBED패턴을 주사투과전자현미경(STEM)으로 관찰하였다. 그리고 실험에 의하여 얻은 이들 HOLZ선들과 컴퓨터 계산에 의해 그려진 이론적인 HOLZ선들과 비교하는 방법에 의하여 Nd1.85Ce0.15CuO4의 격자상수를 구하였다.

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$(Nd_{1-x}R_x)_2Fe_{14}B$ (R=Y, Pr)의 자기특성 (Magnetic properties of $(Nd_{1-x}R_x)_2Fe_{14}B$ (R=Y, Pr))

  • 김만중;김윤배;김희태;김택기
    • 한국자기학회지
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    • 제8권5호
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    • pp.271-274
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    • 1998
  • 자장중 정렬된(Nd1-xRx)2Fe14B (R=Y, Pr) 다결정 분말을 사용하여 스핀재배열현상과 결정자기이방성을 연구하였다. 이 화합물에서 스핀재배열온도(TSR)는 R=Pr인 경우 0$\leq$x$\leq$0.75 의 조성범위에서 Pr 치환량이 증가함에 따라 $\Delta$TSR=-1.35 K/Pr at.%의 비율로 단순 감소하였으나 R=Y인 경우에는 초기 소량의 감소 후 다시 약간 증가한다. 4.2 K에서 스핀재배열각(SRA)은 Y과 Pr 치환량의 증가에 따라 0$\leq$x$\leq$0.5의 범위에서 $\Delta$SRA=-0.073$^{\circ}$/T at.%와 $\Delta$SRA=-0.258$^{\circ}$/Pr at.% 비율로 감소한다. 4.2 K에서 결정자기이방성상수의 조사결과 R=Y인 경우 x=0.9 이상에서 R=Pr인 경우에는 x=0.8 이상에서 스핀재배열현상이 사라질 것으로 예측되었다.

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Nd2-xSrxNiO4+δ/GDC(x = 0, 0.4, 0.6) 공기극의 전기화학특성 평가 (Electrochemical Performance of a Nd2-xSrxNiO4+δ/GDC(x = 0, 0.4, 0.6) as a SOFC Cathode Material)

  • 이경진;서정욱;임예솔;황해진
    • 한국세라믹학회지
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    • 제51권1호
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    • pp.51-56
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    • 2014
  • Mixed ionic and electronic conducting $K_2NiF_4$-type oxide, $Nd_{2-x}Sr_xNiO_{4+\delta}$ (x = 0, 0.4, 0.6) powders were synthesized by a solid-state reaction technique and solid oxide fuel cells consisting of a $Nd_{2-x}Sr_xNiO_{4+\delta}-GDC$ cathode, a Ni-YSZ anode and 8YSZ as an electrolyte were fabricated. The effect of strontium substitution for neodymium on the electrical and electrochemical properties was examined. The electrical conductivity increased with an increase in the Sr doping content, while it appears that the excess oxygen (${\delta}$) decreased. Sr doping into $Nd_2NiO_{4+\delta}$ resulted in an increase in the cathode polarization resistance and an decrease in the power density of the cell. These phenomena may be associated with the decreased amount of excess oxygen noted in the $Nd_{2-x}Sr_xNiO_{4+\delta}$ cathode.

Heat Treatment Condition for Preparing $Nd_{1+x}Ba_{2-x}Cu_{3}O_{7-\delta}$ Superconductors

  • Fan Zhan guo;wha, Soh-Dea;zhan, Si-Ping;Li Yingmel;Lim Byongjae
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2001년도 하계학술대회 논문집
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    • pp.624-627
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    • 2001
  • Two kinds of Nd$_{1+x}$Ba$_{2-x}$Cu$_3$O$_{7-{\delta}}$, the sintering samples and zone melting samples, were heat treated under pure Ar at 95$0^{\circ}C$. The substitution of Nd ion for Ba ion in the Nd$_{1+x}$Ba$_{2-x}$Cu$_3$O$_{7-{\delta}}$ before and after the heat treatment were investigated by XRD. In order to know the effects of the heat treatment, the T$_{c}$ and J$_{c}$ of samples with the heat treatment and those without the heat treatment by Ar were comparatively studied. The results show that the substitution of Nd for Ba decreased, T$_{c}$, and J$_{c}$ increased after the treatment under Ar at 95$0^{\circ}C$. The Nd$_{1+x}$Ba$_{2-x}$Cu$_3$O$_{7-{\delta}}$ samples were oxygenated under pure oxygen at 30$0^{\circ}C$. From the XRD pattern it was found that the sample with x< 0.4 could transfer from tetragonal phase to orthorhombic phase after the oxygenation, but the sample with x>0.4 could not make the phase transition even after a long time oxygenation.ion even after a long time oxygenation.ation.n.ation.ation.

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Effect of oxygen pressure on properties of $NdBa_2Cu_3O_{7-{\delta}}$ films on $SrTiO_3$ (100) substrates grown by pulsed laser deposition

  • Wee, Sung-Hun;Moon, Seung-Hyun;Park, Chan;Yoo, Sang-Im
    • 한국초전도ㆍ저온공학회논문지
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    • 제6권4호
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    • pp.9-12
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    • 2004
  • We report a successful fabrication of high-$J_C$ $NdBa_2Cu_3O_{7-{\delta}}$ (NdBCO) films on (100) $SrTiO_3$ substrates by pulsed laser deposition (PLD) in high oxygen pressures ranging from 400 to 800 mTorr. Fabricated NdBCO films exhibited only c-axis orientation, good out-of-plane and in-plane textures, and also excellent superconducting properties, including critical temperature ($T_C$) and critical current density ($J_C$) of above 90 K and the highest of $3.1MA/cm^2$ at 77 K in self-field, implying that NdBCO is a perspective alternative to YBCO for coated conductor. In low oxygen pressures ranging from 100 to 200 mTorr, however, the films showed a-, c-mixed orientation and degraded $T_{C,zero}$ values due to the formation of $Nd_{1+x}Ba_{2-x}Cu_3O_{7-{\delta}}$-type solid solutions with an excessive substitution of $Nd^{3+}$ ions for the $Ba^{2+}$ sites.

QSPR Analysis of Solvent Effect on Selectivity of 18-Crown-6 between $Nd^{3+}$ and $Eu^{3+}$ Ions: a Monte Carlo Simulation Study

  • Kim, Hag-Sung
    • Bulletin of the Korean Chemical Society
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    • 제27권12호
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    • pp.2011-2018
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    • 2006
  • We have investigated the solvent effects on $\Delta log\;K_s $(the difference of stability constant of binding) and the different free energies of binding of $Nd^{3+}$ and $Eu^{3+}$ ions to 18-crown-6, i.e., the selectivity of $Nd^{3+}$ and $Eu^{3+}$ ions to 18-crown-6 using a Monte Carlo simulation of statistical perturbation theory (SPT) in diverse solvents. The stability constant ($\Delta log\;K_s $) of binding of $Nd^{3+}$ and $Eu^{3+}$ ions to 18-crown-6, in $CH_3OH$ was calculated in this study as -1.06 agrees well with the different experimental results of -0.44~-0.6, respectively. We have reported here the quantitative solvent-polarity relationships (QSPR) studied on the solvent effects the relative free energies of binding of $Nd^{3+}$ and $Eu^{3+}$ ions to 18-crown-6. From the calculated coefficients of QSPR, we have noted that solvent polarity (ET) and Kamlet -Tafts solvatochromic parameters (b ) dominate the differences in relative solvation Gibbs free energies of $Nd^{3+}$ and $Eu^{3+}$ ions but basicity (Bj) dominates the negative values in differences in the stability constant ($\Delta log\;K_s $) as well as the relative free energies of binding of $Nd^{3+}$ and $Eu^{3+}$ ions to 18-crown-6 and acidity (Aj) dominates the positive values in differences in the stability constant ($\Delta log\;K_s $) as well as the relative free energies of binding of $Nd^{3+}$ and $Eu^{3+}$ ions to 18-crown-6.

Nd1+XBa2-XCu3O7-δ Bulk Superconductor by Zone-melt Process

  • Soh, Dea-Wha;Guo, Fan-Zhan
    • Transactions on Electrical and Electronic Materials
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    • 제3권3호
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    • pp.21-24
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    • 2002
  • Two kinds of $Nd_{1+X}Ba_{2-X}Cu_3O_{7-{\delta}}$, the sintering samples and zone melting samples, were heat-treated under pure Ar at 950$^{circ}C$. The substitution of Nd ion for Ba ion in the $Nd_{1+X}Ba_{2-X}Cu_3O_{7-{\delta}}$ before and after the heat treatment was investigated by XRD. In order to confirm the effects of the heat treatment, the Tc and Jc of samples with/without the heat treatment under Ar were comparatively studied. $Nd_{1+X}Ba_{2-X}Cu_3O_{7-{\delta}}$ samples were oxygenated under pure oxygen at $300^{circ}C$. From the XRD pattern it was found that the sample with x<0.4 was transferred from tetragonal phase to orthorhombic phase after the oxygenation, while the sample with x>0.4 did not show the phase transition even after a long time oxygenation. Therefore, the low oxygen partial pressure (Ar+1 % O$_2$) was used for the ambient atmosphere of the zone-melting samples, which could reduce the melting temperature and depress the substitution of Nd for Ba. After the improvement in the zone-melting process, the Jc value was increased to 2 x $10^4$A/$cm^2$ (0 T, 78 K). The particle orientation and the structure of zone-melted NdBaCuO were studied by the XRD and SEM analysis.

고굴절 네마틱 액정에서의 액정 디스플레이의 고속응답 특성 (Fast Response Characteristics in Liquid Crystal Display in the High birefringence nematic liquid crystal)

  • 김종환;황정연;서대식
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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    • pp.498-501
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    • 2003
  • We investigated response characteristics of twisted nematic (TN) cell with different nematic liquid crystals (NLCs) and cell gap d on a rubbed polyimide (PI) surface. High transmittance and fast response time of the TN cell on the rubbed PI surface were achieved by using high birefringence (${\Delta}n$) and low cell gap d. The transmittance and response time of the TN cell on the rubbed PI surface decreased with decreasing ${\Delta}nd$. The fast response time of TN cell using high birefringence with ${\Delta}nd=0.363$ on the rubbed PI surface was measured 5.1 ms.

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