• 한국세라믹학회지
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• 제32권1호
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• pp.83-89
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• 1995

YBa2Cu3O7-$\delta$, Y2BaCuO5, and binary compounds in the Ba-Cu-O system with the nominal composition of Ba2CuO3, BaCuO2, Ba3Cu4O7, Ba3Cu5O8 were synthesized to investigate the heat evolutions and crystalline phases in the hydration reaction of orthorhombic YBa2Cu3O7-$\delta$ phase. The observed crystalline phases were YBa2Cu3O7-$\delta$, Y2BaCuO5, and BaCuO2, or Ba2Cu3O5＋x, and some amount of noncrystalline phase in the Ba-Cu system comounds. In contact with distilled water, YBa2Cu3O7-$\delta$ and Y2BaCuO5 did not have considerable heat liberation, but in the binary compounds of the Ba-Cu-O system, the amount of total heat liberation was increased with respect to the Cu content. It might be that the reaction of high temperature superconductor YBa2Cu3O7-$\delta$ with water and/or moisture originated from the unusual oxidation state of Cu ion and the presence of amorphous Ba-Cu oxide compound. The degradation of high Tc superconductor by moisture and water could be controlled by restricting the heterogeneous distribution of Tc comlposition and the formation of second phase, such as stable Y2BaCuO5, and the resulting unstable Ba-Cu oxide compound.

• Transactions on Electrical and Electronic Materials
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• 제5권2호
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• pp.81-85
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• 2004

High T$\_$c/ (Sm/Y)$\_$1.8/Ba$\_$2.4/Cu$\_$3.4/O$\_$7-$\delta$/ ［(Sm/Y)］ superconductor, a combination of Y and Sm(50% each), was systematically investigated by the zone melt growth process. A sample prepared by this method showed well-textured microstructure, and (Sm/Y)$_2$BaCuO$\_$5/［(Sm/Y)211］inclusions were uniformly dispersed in large (Sm/Y)Ba$_2$Cu$_3$O$\_$y/ ［(Sm/Y)123］matrix. The sample showed a sharp superconducting transition at 91 K. The magnetization measurements of the (Sm/Y)1.8 sample exhibited the enhanced flux pinning, compared with Y$\_$1.8/Ba$\_$2.4/Cu$\_$3.4/O$\_$7-$\delta$/(Y1.8) sample without Sm. Critical current densities of (Sm/Y) 1.8 sample was 3.5${\times}$10$^4$A/$\textrm{cm}^2$ at 1 T and 77 K.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 1999년도 추계학술강연 및 발표대회 강연 및 발표논문 초록집
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• pp.16-16
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• 1999

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2002년도 High Temperature Superconductivity Vol.XII
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• pp.75-75
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• 2002

• 한국재료학회지
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• 제4권8호
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• pp.870-876
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• 1994

$Y_{1}Ba_{2}Cu_{3}O_{7-\delta}$계에서 211상의 성장거동을 관찰하기 위하여 123시편을 $1100^{\circ}C$에서 유지시간을 변화시켜 MgO다결정 기판과 MgO 단결정 기판위에 놓고 소결시킨 후 공냉하였다. 211입자는 유지 시간이 증가함에 따라 성장하였으며MgO단결정 기판보다 MgO다결정 기판을 사용했을때 더 큰 성장을 보였다. CuO양을 변화시키면서 만든 $Y_{2}Ba_{1+X}Cu_{3}O_{5+\delta}$ 시편에서 211입자는 CuO양이 증가함에 따라 조대해졌으며 0.6mol CuO가 더 첨가된 시편에서 가장 큰 211입자가 관찰되었다. $Y_{2}Ba_{1+X}Cu_{3}O_{5+\delta}$시편에서 211입자는 아주 미세하고 균일하게 분포되었다. $SnO_{2}$첨가로 인한 211입자의 성장억제 효과는 ($BaCuO_{2}$+ CuO)액상에서보다 CuO액상에서 더 크게 나타났다.

• 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.

• Bulletin of the Korean Chemical Society
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• 제11권6호
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• pp.564-567
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• 1990

A lithiated compound $Li_{0.1}Pr^{3+}Ba_2Cu_3O_y$ has been successfully prepared by electrochemical method, which is achieved with a two electrode cell of the type: Metal(Li)/($Li^+\;,\;ClO_4^-$) + propylene carbonate/$PrBa_2Cu_3O_y$. All Pr ions in the lithiated compound are stabilized with a trivalent state as the other rare earths (Ⅲ) substituted in the 90K superconductor lattice ($Y_{1-x}Ln_x^-Ba_2Cu_3O_{7-{\delta}}$). Powder X-ray diffraction analysis shows that both compounds, $PrBa_2Cu_3O_y$ and $Li_{0.1}PrBa_2Cu_3O_y$ are isostructural with the 90 K superconductor, ($YBa_2Cu_3O_{7-{\delta}}$), nevertheless both of them are non-metallic and also non-superconducting down to 10 K. Magnetic susceptibility ${\chi}$ vs. temperature data indicate that Curie contribution from the magnetic ions (Pr and Cu) is weakened on the one hand, but on the other hand temperature-independent part of susceptibility ${\chi}_o$ increases depending upon the rate of lithium intercalation in $PrBa_2Cu_3O_y$ lattice.

• Bulletin of the Korean Chemical Society
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• 제10권1호
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• pp.5-8
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• 1989

Conventional ceramic method has been used to prepare the green phase, $Y_2BaCuO_5$, commonly observed in 90-K superconductor $YBa_2Cu_3O_P{7-{\delta}}$as an impurity phase. The powder X-ray diffraction analysis indicates that $Y_2BaCuO_5$ has an orthorhombic symmetry with lattice parameter of a = 12.2 $\AA$, b = 5.61 $\AA$, and c = 7.14 $\AA.$ The average g-value 2.13 observed in ESR spectrum is attributable to Cu2+ stabilized in $C_{4v}$ field. From the magnetic susceptibility ($\mu$eff = 2.29 BM) and the ESR measurements, it is confirmed that Cu(II) $3d^9$ electrons in $Y_2BaCuO_5$ are localized and can be characterized by Curie-Weiss behavior. Optical reflectance spectrum shows a broad absorption peak around 680 nm due to dxy ${\rightarrow}$ $dx^2-y^2$ eletronic transition.

• 한국자기학회지
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• 제4권1호
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• pp.44-47
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• 1994

Laser ablation법으로 c-축 배향되도록 만든 Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7- .delta. / 박막으로 임계온도 근처에서 운반자들의 정보를 얻기위하여 Hall 효과를 연구하였다. 자기비저항은 Nernst 효과 때문에 자기장이 증가할 수록 offset 점의 온도가 낮았고, 자기비저항으로 부터 열자기적 효과를 고 려하여 계산한 Hall 비저항값과 실제 van der Pauw 법으로 측정한 Hall 비저항값을 비교해 본 결과 비교적 잘 일치하였다.

• 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.