• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.2
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• pp.148-156
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• 1994

Three composition in the system of $YO_{1.5}-BaO-CuO$ were grown using a cold crucible (skull) melting technique with a 50 kW R.F. induction generator operating at 4 MHz as the power source. The starting materials were prepared by conventional ceramic powder processing methods, loaded into the skull, and melted at about $1200^{\circ}C$. For this study, compositions near the $YBa_2Cu_3O_X$ region were selected. The growth rates used ranged from 4 cm/hr to 0.25 cm/hr. The relation between the microstructures and the starting composition of each ingot was determined using metallograph, X-ray diffraction, and energy dispersive X-ray analysis. Both $YBa_2Cu_3O_X$ and $Y_2BaCuO_5$ needle-shaped crystals, aligned with the growth direction, were formed in the $CuO-BaCuO_2$ eutectic matrix of the $YBa_2Cu_7O_x and YBa_5Cu_{11}O_x$ ingot.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.351-354
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• 1998

The formation of the $YBa_2Cu_30_{7_\delta}$(Y123) thick films has been investigated by a surface diffusion Imcess between $3BaCu0_2$+2CuO composite coating powder and a $Y_2BaCuO_5$(Y211). This reaction has been studied in the temperature of $930^{\circ}C$ and $940^{\circ}C$ for 2h to 10h in an oxygen atmosphere. The Y211 substrates becomes covered by co-precipitation of Y123 grains and CuO inclusions. X-ray diflractotnctn. revealed that the lager consisted of an orthorhombic crystal structure. The maximum Jc of $400A/\textrm{cm}^2$ is abtained when the specimen was heat-treated at $930^{\circ}C$ for 6h on the Y211 substrate.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.6
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• pp.493-501
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• 1998

$YBa_2Cu_3O_X$ samples were fabricated by MPMG(Melt Powdered Melt Growth). Intitial composition of the mixed powders were prepared as follow ; $YBa_2Cu_3O_X$ : $Y_2BaCuO_5$ = 1:0, 1:0.2, 1:0.3, 1:0.4. After the first melt and cooling, 5wt% to 20wt% fo Ag power was added to the powder. Effects of the different initial $Y_2BaCuO_5$ and Ag addition amount on $J_c$ and magnetization of $YBa_2Cu_3O_X$ fabricated by MPMG method were investigated. The critical current density increased with the amount of $Y_2BaCuO_5$ and Ag. It was also observed that the difference between negative and positive magnetization in the magnetization hysteresis measurement at 77K was larger than the case where $Y_2BaCuO_5$and Ag were not added to the $YBa_2Cu_3O_X$ powders. It is concluded that $Y_2BaCuO_5$ sample with 40wt% amount of $Y_2BaCuO_5$ and 20wt% amount of Ag has not only the largest $J_c$ but also the improved pinning effect.

• Bulletin of the Korean Chemical Society
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• v.10 no.6
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• pp.504-509
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• 1989

The effect of oxygen-deficiency on the charge distributions and orbital energies for small copper oxide clusters representing the superconducting materials $YBa_2Cu_3O_x (6{\leq}x{\leq}7)$ were investigated by the extended Huckel molecular orbital (EHMO) method with the tight-binding model. Our calculations show +3 oxidation state of Cu(1) in the $CuO_3$ chain and +2 or +1 of Cu(2) in the $CuO_2$ layers for $YBa_2Cu_3O_7$ with the nominal charge of $Cu_3$ = +7 (or +5), while for $YBa_2Cu_3O_6$ +1 oxidation state of Cu(1) and +3 (or +2) of Cu(2) in the $CuO_2$ layers with the nominal charge of $Cu_3$ = +7 (or +5). For $Cu_3O_{12}$ cluster representing $YBa_2Cu_3O_7$ with the nominal charge of $Cu_3$ = +7 the Cu(2) $d_{{x^2}-{y^2}}$ orbitals in the $CuO_2$ layers is a typical Jahn-Teller $d^9$ system with the partial hole and the Cu(1) $d_{{_z2}-{_y2}}$ orbital in the $CuO_3$ chain contains hole occupancy. For $Cu_3O_{10}$ cluster representing $YBa_2Cu_3O_6$ with the nominal charge of Cu = +5 the orbital character of the highest partially occupied MO (HPOMO) and the lowest completely unoccupied MO (LCUMO) of $Cu_3O_{12}$ representing $YBa_2Cu_3O_7$ with the nominal charge of $Cu_3$ = +7 is reversed, and the character of Cu(1) $d{{x^2}-{y^2}}$ orbital of LCUMO of the $Cu_3O_{12} $cluster is vanished. It is suggested that the local crystal field environment of Cu(1) by the oxygens in the Cu(1) chain may play a vital role in conductivity and superconductivity, either alone or through cooperative electronic coupling with the Cu(2) layers in $YBa_2Cu_3O_7.$.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.44 no.8
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• pp.1063-1067
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• 1995

The superconducting properties of YBa$_{2}$Cu$_{3}$$O_{7-x}$(YBaCuO) thin films prepared by laser ablation have been investigated. The x-ray diffraction patterns and surface morphology of the films were substantially different from one another. The compositional ratios of YBaCuO films were controlled by the conditions of the target-substrate distance. The YBaCuO films manufactured on MgO(100) substrate were indicated T$_{c}$(zero)=91.2 K, T$_{c}$(onset)=93 K, and J$_{c}$=3.5*10$^{5}$ A/cm$^{2}$(at 77.3K). The optimum conditions were found to be a substrate temperature of 710 .deg. C, a energy density of 2 J/cm$^{2}$, and a target-substrate distance of 60 mm in an oxygen partial pressure of 200 mTorr.0 mTorr.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.263-266
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• 2003

The fine $YBa_2Cu_3O_x$ powder ($0.2{\sim}1.0\;{\mu}m$) is produced by sol-gel method, and electrophoresis deposition is used for the preparation of $YBa_2Cu_3O_x$ thick films which are deposited on Ag wire. The oriented $YBa_2Cu_3O_x$ was tried to be prepared by the zone-melting method under low oxygen partial pressure. The orientation and the phase composition were examined by the X-ray diffraction and the superconductivities were measured by 4 line method. The critical current densities are still quite low, which may be due to unsuitable technical parameters for zone-melting of $YBa_2Cu_3O_x$ thick films. Therefore the heat treatment condition and controlling of low oxygen partial pressure should be improved in the future experiment.

• Journal of the Speleological Society of Korea
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• no.76
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• pp.15-17
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• 2006

[ $YBa_2Cu_3O_{7-{\delta}}$ ] superconductor films have been prepared on silver substrates by electrophoretic deposition. As silver does not react with $YBa_2Cu_3O_{7-{\delta}}$ compound and has little influence on its superconductivity, it is usually doped in $YBa_2Cu_3O_7$ to improve the strength of the material and eliminate micro cracks. It has been proved that Ag additive can lower the melting temperature of $YBa_2Cu_3O_{7-{\delta}}$ and act as linking bridge among $YBa_2Cu_3O_{7-{\delta}}$ particles, thus in this paper Ag doped $YBa_2Cu_3O_{7-{\delta}}$ thick films are prepared by electrophoretic co deposition. As there are only some referenced experience formula and models for co electrophoretic deposition and does not exist unified explanation, the behavior of Ag particles during co electrophoretic deposition is also studied.

• Journal of the Korean Vacuum Society
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• v.1 no.3
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• pp.389-394
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• 1992

용액분무법으로 (100) MgO 단결정 기판위에 YBa2Cu3O7-x 초전도박막을 제조하 였다. YBa2Cu3O7-x 초전도 박막의 Y, Ba, Cu 원자의 상대적인 비는 EDX의 검출 한계내에 서 1 : 2 : 3이었고, 이는 분무 용액속의 금속이온의 비와 같았다. YBa2Cu3O7-x 초전도 박 막의 결정구조는 단일 상의 사방구조였으며, 기판에 수직인 c축의 방향으로 grain이 성장되 었고, 격자상수 c0는 11.678$\AA$였다. 95$0^{\circ}C$의 공기중에서 10분간 열처리한 박막의 Tc-on=100K, Tc-zero=80K, Jc=2.5 $\times$ 104A/cm2였고, 95$0^{\circ}C$의 흐르는 산소분위기에서 10분간 열처리한 박막의 Tc-on=103K, Tc-zero=80K, Jc=1.0 $\times$ 105A/cm2였다. 초전도 박막의 미세구 조, grain 크기와 grain 경계폭은 제조후 열처리(post-annealing) 시간과 가스 분위기에 강 한 영향을 받았다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.8
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• pp.1771-1776
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• 2011

In this paper, as an attempt to improve the preparation conditions of $YBa_2Cu_3Ox$ superconducting bulk samples, the properties of $YBa_2Cu_3Ox$ superconductor depending on the particle size of YBCO powder and $BaPbO_3$ as an additive have been investigated, and a study on the effects of additive to the density, grain alignment, and porosity of samples that affect the critical current of superconductor has been performed. In order to prepare superconductor, $YBa_2Cu_3Ox$ powder synthesized by sol-gel method, showing a size distribution of 0.2~1 ${\mu}m$ was used. The $BaPbO_3$ added to promote grain growth and to decrease porosities and weak links between grain boundaries of $YBa_2Cu_3Ox$ superconductors. In the samples prepared by sol-gel synthesized powder with 10, 20, and 30 wt% conductive $BaPbO_3$ additives, the sample with 20 wt% $BaPbO_3$ obtained the highest critical current of 4.74 A, showing 20 wt% higher critical current than that with solid state synthesized powder.

• Journal of the Korean Magnetics Society
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• v.4 no.1
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• pp.48-51
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• 1994

We have studied the room temperature anisotropy in the high $T_{c}$ superconductor $YBa_{2}Cu_{3}O_{7}$ by means of the $^{63}Cu$ nuclear quadrupole resonance (NQR). For the magnetically oriented powder samples, NQR signals were obtained only when the RF magnetic field is applied perpendicular to the direction of the crystalline c-axis. Significant differences in the spin-lattice relaxation times ($T_{1}$) and the lineshapes were observed between the unoriented powder sample and the magnetically oriented sample.