• Bulletin of the Korean Chemical Society
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• v.11 no.6
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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.

• Progress in Superconductivity
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• v.11 no.2
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• pp.141-146
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• 2010

Phase stability diagram and boundary of a- and c-axis orientation of $SmBa_2Cu_3O_{7-y}$ (SmBCO) thin films grown by pulsed laser deposition (PLD) were reported with studies based on x-ray diffraction [1]. Four different samples are systematically analyzed: normal c-axis oriented orthorhombic $SmBa_2Cu_3O_{7-y}$, a-axis oriented $SmBa_2Cu_3O_{7-y}$, c-axis oriented orthorhombic $SmBa_2Cu_3O_{7-y}$ with $Sm_2BaCuO_5$ phase, and a mixture with c-axis oriented orthorhombic $SmBa_2Cu_3O_{7-y}$ and anomalously long-c tetragonal $SmBa_2Cu_3O_x$. Raman scattering spectroscopy equipped with polarization analysis elucidates the crystal orientation and the origin of the growth of the materials. It indicates that the technique can be used for quality control of conductor manufacturing processes as well as for enhancement of the materials properties.

• Korean Journal of Materials Research
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• v.5 no.7
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• pp.786-793
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• 1995

Ag-doped $Y_1$Ba$_2$Cu$_3$O$_{7-y}$ samples have been prepared by solid state reaction. High-Tc super conductivity, microstructure and mechanical property of the Ag-doped $Y_1$Ba$_2$Cu$_3$O$_{7-y}$ samples have been studied. As the Ag content increased, the grain size of $Y_1$Ba$_2$Cu$_3$O$_{7-y}$, increased and connectivity between the grains was improved, and the sample becomed denser and harder than the undoped. From the result, it is concluded that Ag addition reduced weak link and weak coupling between grains and led to the strong coupling. Furthermore, the anisotropy of crytstal structure was decreased and thermal stability, mechanical property of $Y_1$Ba$_2$Cu$_3$O$_{7-y}$-Ag were improved.mproved.

• Journal of the Korean Chemical Society
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• v.36 no.6
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• pp.818-823
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• 1992

2-Ethylhexanoate compounds which contained Y, Er, Yb, Ba, and Cu were prepared separately. These metallo-organic compounds were dissolved together in the common solvent and the solution was homogeneous. From these solution, high $T_c$ superconductors $YBa_2Cu_3O_{7-\delta}(Y_{123})$, $ErBa_2Cu_3O_{7-\delta}(Er_{123})$, and $YbBa_2Cu_3O_{7-\delta}(Yb_{123})$ were prepared. XRD analysis showed that these superconductors were not single phase and contained some impurity phases including $YBa_2Cu_4O_8(Y_{124})$. This was also confirmed from the magnetic susceptibility measurement. Generally, critical temperatures were higher than that of the superconductors prepared by ceramic method. Volume diamagnetic susceptibility showed little variation compared to the specimen made by ceramic method.

• Progress in Superconductivity and Cryogenics
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• v.4 no.1
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• pp.21-25
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• 2002

The effect of Ca-doping on the superconducting properties of Nd-Ba-Cu-O bulk superconductors, fabricated by the oxygen-controlled melt growth process, has been systematically investigated. Various c-axis textured bulk samples were grown using precursors with the nominal compositions of $Nd_{1.8-x}Ca_{x]Ba_{2.4}Cu_{3.4}O_{y}$ (x= 0.00, 0.02, 0.05, 0.10, 0.15) in a reduced oxygen atmosphere of 1%O$_2$ in Ar. Magnetization measurements revealed that the critical temperatures(Tc) were almost linearly depressed from 95K to 86K with increasing the Ca dopant from x : 0.0 to 0.15, respectively, and thus critical current densities(Jc) at 77K and for H//c-axis of specimens were gradually degraded with increasing x. Compositional analyses revealed that although the amounts of the Ca dopant both in $NdBa_2Cu_2O_y(Nd123) and Nd_4Ba_2Cu_2O_{10}(Nd422)$,/TEX> were increased with increasing x, only less than half of the initial Ca compositions were detected in melt-grown Ca-doped Nd-Ba-Cu-O bulk crystals. The supression of Tc is attributed to an increased Nd substitution for the Ba site in the Nd123 superconducting matrix with increasing the amount of the Ca dopant.

• Journal of the Korean Society for Heat Treatment
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• v.4 no.3
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• pp.47-53
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• 1991

In this study, the structural phase transition and decomposition of superconducting ceramic, Y-Ba-Cu-O system was studied. The results of the study are as follows. The high Tc superconductor $Y_2Ba_2Cu_3O_{7-x}$ is made in solid state reaction of $O_2$ atmosphere and the valve of X in $Y_2Ba_2Cu_3O_{7-x}$ is 0.1~0.2. The transition temperature of tetragonal-orthorhombic phase of $Y_2Ba_2Cu_3O_{7-x}$ appear at $790^{\circ}C-900^{\circ}C$. In the result of measuring the electrical resistance of sample annealed in $O_2$ atmosphere, the electrical resistance show zero at 92 K and the best superconductor, $Y_2Ba_2Cu_3O_{7-x}$(Y 123) can be mabe.

• Korean Journal of Materials Research
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• v.5 no.4
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• pp.433-444
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• 1995

BaCe$O_{3}$를 첨가하여 용융공정으로 제조한 단결정형 Y$Ba_{2}$$Cu_{3}$$O_{x}$(1-2-3) 초전도체의 온도에 대한 자화특성을 연구하였다. 고상반응법과 용융공정으로 0에서 30wt% BaCe$O_{3}$를 1-2-3 결정내에 미세 분산시켰다. 초전도체의 자화특성은 VSM(vibrating sample magnetometer)을 사용하여 77K, 60K, 40K와 20K, 2 Tesla 자장범위에서 측정하였다. BaCe$O_{3}$를 첨가하지 않은 겨우나 5wt% BaCe$O_{3}$를 첨가한 1-2-3 결정의 경우, 77K, 외부자장이 증가시 자화율 차이가 증가하는 비정상 자화특성이 관찰된다. 측정온도가 60K에서는 제2차 최대점이 나타나는 자장값이 고자장쪽으로 이동한다. 20K와 40K의 저온에서는 비정상자화특성이 2 T의 자장범위까지 관찰되지 않았다. 15wt%와 20wt% BaCe$O_{3}$첨가한 시편에서는 자장이 증가하면 자화율차이가 단순히 감소한다. Y-Ba-Cu-O의 flux pinning 기구를 BaCe$O_{3}$첨가에 의한 미세조직변화로 설명하였다.

• 한국기계연구소 소보
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• s.20
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• pp.65-70
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• 1990

The $Y_2 BaCuO_5$ phase was synthesized under various calcination temperatures and sintered. The $Y_2 BaCuO_5$ phase strarted to form at $850^{\circ}C$ for 6hours calcination time and, at $1000^{\circ}C$, all the X-ray diffraction peaks corresponded to $Y_2 BaCuO_5$. The sintered density of $Y_2 BaCuO_5$ was increased to 97 % of its theoretical density by the control of calcination temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.913-916
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• 2001

From 1994 the cooperation between NEU of China and MJU of South Korea for study of ReBaCuO (Re=Rare earth elements) superconductors has been carried out. The progress has been got in following projects. Critical current density ($J_c$) of YBaCuO superconductor prepared by Melting Textured Growth (MTG) was improved. In the preparation of textured YBaCuO, 20 wt.% of YBaCuO 211 phase was added, which would be climactic for the microcracks in the textured YBaCuO. The effects of the 211 phase and Ag content on the superconductivity were studied and discussed in detail. The improved $J_c$ value was reached to 8$\times$10^4 A/cm^2 (77K,0T). Single phase $YbBa_{2}Cu_{3}O_{x}$ superconductor was sintered by the traditional powder metallurgical method, and its reaction process was studied. In recent years, NdBaCuO superconductor is being performed. The behavior of $Nd_{4}Ba_{2}Cu_{2}O_{10}$(Nd422 phase) and the solid solubility, x in the superconductor $Nd_{1+x}Ba_{2-x}Cu_{3}O_{y}$ by the heat treatment in the low oxygen partial pressure (1%) or Ar at $950{\circ}C$ were investigated. The zone-melting process was used to make oriented NdBaCuO superconductor in order to increase the critical current density.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.85-88
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• 2001

The NdBaCuO superconductor samples were Zone-melted in low oxygen partial pressure (1% $O_{2}+ 99% Ar$ ). The Zone-melting temperature was decreased about $120^{\circ}C$ from $1060^{\circ}C$ the zone-melting temperature in air. Thus the loss of liquid phase ($BaCuO_{2}$ and CuO) was reduced during the zone-melting process. The content of non-superconducting phase Nd422 in zone-melted NdBaCuO samples was clearly decreased, so was the substitution of Nd for Ba. The superconductivity of zone-melted $Nd_{1+x}Ba_{2-x}Cu_{3}O_{y}$ prepared under low oxygen partial pressure was distinctively improved.