• Journal of the Korean Ceramic Society
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• v.35 no.1
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• pp.79-87
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• 1998

Melt spun YbBa2Cu3Agx(x=0, 5, 12, 16 and 53) precursor alloy ribbons were oxidized at 263-330$^{\circ}C$ and treated at 820$^{\circ}C$, 855$^{\circ}C$ and 885$^{\circ}C$ under 1.0 atm oxygen pressure. In the ribbons treated at 820$^{\circ}C$, 855$^{\circ}C$and 885$^{\circ}C$ 1-2-4 phase (YbBa2Cu4O8) and 1-2-3 phase (YbBa2Cu3O{{{{ OMICRON _7-$\delta$ }})were formed respectively. The shape of 1-2-4 phase was distorted or ellipsoid. The 2-4-7 and 1-2-3 phases tooked the shape of bar. All the ribbons showed zero critical current density Jc at 77K in zero magnetic field. By considering the shape and the highest critical temperature (among the three phases) of the 1-2-3 phase we tried to increase the critical current density of the ribbons treated at 885$^{\circ}C$ by press deformation. About tenribbons were stacked and coupled by press deformation and then treated at 885$^{\circ}C$ These 1-2-3 phase did not show any texture in any of the ribbons. However they exhibited weak texture in the multilayered specimens. Among the multilayered specimens YbBa2Cu3Ag16 exhibited a Jc of 180 A/cm2 Among the above ribbons YbBa2Cu3Ag16 ribbon has the optimum composition to produce textured superconducting oxide with improved Jc by press deformation. Onset critical temperatures Ton of the multilayered YbBa2Cu3Agx(x=5, 12, 16 and 53) were measured as 88-90 K.

• Progress in Superconductivity
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• v.6 no.1
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• pp.13-18
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• 2004

High-.ate in-situ$ YBa_2$Cu$Cu_3$$O_{7-x}$ (YBCO) film growth was demonstrated by means of the electron beam co-evaporation. Even though our oxygen pressure is low, ∼$5 ${\times}$10^{-5}$ Torr, we can synthesize as-grown superconducting YBCO films at a deposition rate of around 10 nm/s. Relatively high temperatures of around 90$0^{\circ}C$ was necessary in this process so far, and it suggests that this temperature at a given oxygen activity allows a Ba-Cu-O liquid formation along with an YBCO epitaxy. Local critical current density shows a clear correlation with local resistivity. Homogeneous transport properties with a large critical current density ($4 ∼ 5 MA/\textrm{cm}^2$ at 77K, 0T) are observed in top faulted region while it is found that the bottom part carries little supercurrent with a large local resistivity. Therefore, it is possible that thickness dependence of critical current density is closely related with a topological variation of good superconducting paths and/or grains in the film bodies. The information derived from it may be useful in the characterization and optimization of superconducting films for electrical power and other applications.

• Korean Journal of Materials Research
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• v.2 no.3
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• pp.202-206
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• 1992

The $CeO_2$-added Y-Ba-Cu-O oxides were prepared by the partial melt process involving the peritectic reaction, liquid + 2-1-1 phase ${\rightarrow}$ 1-2-3 phase, to investigate the effect of the dopant on microstructure and superconductivity. During the peritec reaction, all the added $CeO_2$ was converted to $BaCeO_3$ particles which were finely dispersed in large 1-2-3 grains. Superconducting transition temperature($T_{c}R=0$ point) of the partial-melted samples was as high as 90K regardless of $CeO_2$ content up to 5wt%, which is owing to the separation of the second phase from the 1-2-3 superconducting phase.

• Journal of the Korean Magnetics Society
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• v.12 no.5
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• pp.195-200
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• 2002

Low temperature sintering of Co$_2$Z type Ba ferrites with various oxide additives has been studied. Co$_2$Z phase was obtained by 2 step calcination and XRD peaks showed a good agreement with the peaks of the standard Co$_2$Z phase, except for some minor extra peaks. ZnO-B$_2$O$_3$ glass, ZnO-B$_2$O$_3$ and CuO, ZnO-B$_2$O$_3$ and Bi$_2$O$_3$, and ZnO-Bi$_2$O$_3$ glass were added to lower sintering temperatures. Specimens were sintered at the temperature range between 900 $^{\circ}C$ and 1000 $^{\circ}C$. In the single addition of ZnO-B$_2$O$_3$ glass, the specimen with 7.5 wt％ showed the highest shrinkage. Specimens with complex addition of ZnO-B$_2$O$_3$ glass with CuO or Bi$_2$O$_3$ showed higher shrinkages and initial permeabilities than single addition of ZnO-B$_2$O$_3$ glass. Shrinkages and initial permeabilities of the specimens with ZnO-Bi$_2$O$_3$ glass were higher than those of ZnO-B$_2$O$_3$ glass addition.

• Progress in Superconductivity
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• v.11 no.1
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• pp.42-46
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• 2009

With an aim of comparison, single grain Y-Ba-Cu-O (YBCO) bulk superconductors were fabricated using a liquid infiltration growth (LIG) process and a conventional melt growth (MTG) process with top seeding. The MTG process uses an $YBa_2Cu_3O_{7-x}$(Y123) powder as a precursor, while the LIG process uses $Y_2BaCuO_5(Y211)/Ba_3Cu_5O_8(Y035)$ pre-forms. The growth of a single Y123 domain on the top seed was successful in the both processes. Different feature between the two processes is the interior microstructure regarding the critical current density ($J_c$). The LIG-processed YBCO sample showed a lower porosity, more uniform distribution of Y211 particles and the enhanced Y211 refinement compared to the conventional MTG process. The $J_c$ improvement in the LIG process is attributed to the dispersion of finer Y211 particles as well as lower porosity within the Y123 superconducting matrix.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1247-1248
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• 2006

We fabricated YBCO film using a TFA-MOD method. In order to enhance the reaction kinetics and to control the formation of the second phases, $Y_2Ba_1Cu_1O_x$ and $Ba_3Cu_5O_8$ powders were used as precursors (the so called "211 process"). The films were calcined at $460^{\circ}C$ and then fired at $750^{\circ}C-800^{\circ}C$ in a 12.1% humidified $Ar-O_2$ atmosphere. We found that the microstructure varied significantly with the firing temperature. The textures of all of the films were similar and mainly biaxial. For the film fired at $775^{\circ}C$, the critical current was obtained to be 39 A/cm-width (corresponding critical current density is 2.0 MA/$cm^2$).

• Proceedings of the Materials Research Society of Korea Conference
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• 1992.05a
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• pp.16-16
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• 1992

We have studied the effect of platinum addition on the supercon ducting properties of YB $a_2$C $u_3$$O_{7-x}$ (123) compound and elucidated the mechanism of fine dispersion of $Y_2$BaCu $O_{5}$(211) particles in YB $a_2$C $u_3$$O_{7-x}$ superconductor prepared by melting method from the metallurgical point of view. In this study, BaCu $O_2$ and CuO-rich phase unreacted during the peritecitc reaction markedly decreased by the 211 powder addition. The 211 particle of Pt-fee sintered samples exhibited 8~10$\mu$m in size, but in 1wt%Pt-added sample, 211 particles were finely dispersed in 123 matrix and the size of 211 particle was about 1~2$\mu$m. And, the critical temperature( $T_{c. zero}$) of Pt doped samples was 91.5K and the transport critical current density ( $J_{c}$) of Pt-doped samples was much more than 10$^4$A/$\textrm{cm}^2$. The high $J_{c}$ and fine dispersion of 211 particles of Pt doped YB $a_2$C $u_3$$O_{7-x}$ superconductor are attributed to $Ba_4$CuP $t_2$ $O_{8}$ compounds formed during the partial melting, which were considered als nucleation sites of 211 particles, rather than Pt inself.han Pt inself.

• Journal of the Korean Ceramic Society
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• v.33 no.3
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• pp.313-320
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• 1996

We have fabricated an in-plane aligned a-axis oriented YBa2Cu3O7-x (a-YBCO) thin film on a LaSrGaO4(100) substrate with a PrBa2Cu3O7-x(PBCO) template layer by two step plused laser deposition using 308 nm XeCl excimer laser. A YBCO layer and PBCO layer grown at low temperatures were used as template layers. We have investigated the effect of the deposition temperature of template layers on the superconducting and struc-tural properties of in-plane aligned a-YBCO thin films. An optimal deposition temperature of the PBCO template layers was 630. In-plane aligned a-YBCO thin films showed an anisotropy ratio in resistivity of 11.5 and a zero resistance temperature of 88 K.

• Applied Chemistry for Engineering
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• v.7 no.4
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• pp.639-644
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• 1996

The $YBa_2Cu_{3-y}Ag_yO_{7-x}$ high-temperature superconductors were prepared by pyrophoric synthetic method from $Y_2O_3$, $BaCO_3$, CuO, and $AgNO_3$ powders. When we were partially substituted Ag for Cu in $YBa_3Cu_3O_{7-x}$, the superconducting properties of $YBa_2Cu_{3-y}Ag_yO_{7-x}$ were investigated with X-ray diffractometer, resisitivity measuring equipment, SEM, and Vickers Hardness. The Tc,zero of $YBa_2Cu_3O_{7-x}$ was 91K, the density was $5.2g/cm^3$, and the hardness was $590kg/mm^2$. When Ag was substituted below y=0.15, electrical property of $YBa_2Cu_{3-y}Ag_yO_{7-x}$ did not change but microstructure, density, and hardness were enhanced.

• Journal of the Korean institute of surface engineering
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• v.29 no.6
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• pp.829-833
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• 1996

Superconducting YBaCuO thin films were deposited on MgO (100) single crystal substrate by rf reactive sputtering method. Sputtering target was prepared by mixing the original powders of $Y_2O_3$, $BaCO_3$, and CuO at $830^{\circ}C$, and its composition was $YBa_2Cu_{3.3}O_x$ adding the excess CuO to compensate for the loss of Cu in the deposition process. The sputtering conditions for a high quality of YBCO thin film were: substrate temperature of 13$0^{\circ}C$; gas pressure of 10 mTorr; gas mixture ($O_2$: Ar =10: 90); distance of 2.5 inch; and rf power density of 4.87 W /$\textrm{cm}^2$. The deposition rate was 2.4~2.6 nm/min. From the RBS results, it was found that Cu and Ba contents in thin films decreased with the increase of substrate temperature. The increase of gas pressure resulted in significant deficiency of Ba elements.