• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.503-506
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• 2000

YBCO superconducting thick films were prepared on Ag wire by electrophoresis in acetone and ethanol with chemically modified suspension. The addition of organic compounds, such as PEG, EG into suspension solution for improving critical current density was investigated. Surface state, deposition condition, pore distribution and cracks were investigated by using SEM photographs. Controlling preparation conditions were studied for reducing these defects. As a results, in acetone solution, the surface crack of samples was decreased with increasing PEG. On the contrary, the surface crack of sample was increasing with increasing the amount of EG. In ethanol solution without I$_2$, which was generally used for an electrolyte, the deposition time was longer than this of acetone. For that reason the sample deposition in ethanol time was needed with enough stirring time for suspending YBCO powder and deposition time.

• Bulletin of the Korean Chemical Society
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• v.15 no.1
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• pp.20-22
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• 1994

The preparation of $YBa_2Cu_4O_8$ thick film on Ag substrate by electrophoretic deposition was directly studied. Electrophoretic deposition was carried out in solution, which was composed of presintered $YBa_2Cu_4O_8$ powder, sodium, and 2-propanol as a solvent. The deposited thick films were heat-treated in $O_2$ at 815$^{\circ}$C for 12 hours and at 450$^{\circ}$C for 12 hours. We succeeded in obtaining superconducting $YBa_2Cu_4O_8$ films on Ag substrate. Even though the chemical reactions at the $YBa_2Cu_4O_8$/Ag interface occurred in the range of 10 ${\mu}$m, superconductivity was not depressed. The thickness of the films was in the range of 60-80 ${\mu}$ m. The characteristics of the films were examined by electric resistance measurements, X-ray diffraction, and SEM observations.

• Journal of Powder Materials
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• v.15 no.1
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• pp.6-12
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• 2008

[ $YBa_2Cu_3O_{7-y}$ ](123) powders were synthesized by the solid state reaction method using two different purity $BaCO_3$ powders (99.75% and 99.7% purity) and $Y_2O_3$ (99.9%) and CuO (99.9%) powders. The effect of $BaCO_3$ purity on the formation of a 123 phase and the superconducting properties were investigated. The mixtures of raw powders were calcined at temperature ranges of $800^{\circ}C-880^{\circ}C$ in air and finally made into a single grain samples by a melt processing with top seeding. It was found that a 123 phase was well formed at temperature above $870^{\circ}C$, but the purity effect on the 123 formation was negligible. The single-grain 123 samples prepared from the different $BaCO_3$ powders showed the same $T_c$ value of 90.5 K and similar $J_c$ values about $10^4\;A/cm^2$ at 0 T and 77 K, and $10^3\;A/cm^2$ at 2 T and 77 K. This result indicates that the low purity, cheap price $BaCO_3$ powder can be used as a raw material for the fabrication of single-grain, high-$J_c$ superconducting levitator.

• Korean Journal of Materials Research
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• v.24 no.9
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• pp.465-468
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• 2014

The crystallization effects of boron (B) powder on the phase, full width at half maximum (FWHM) values, and critical properties were investigated for in-situ reacted $MgB_2$ bulk superconductors. The semi-crystalline B powder was heat-treated at different temperatures of 1000, 1300 and $1500^{\circ}C$ for 5 hours in an Ar atmosphere. Then, using as-received and heat-treated B powders, the $MgB_2$ samples were prepared at $600^{\circ}C$ for 40 hours in an Ar atmosphere. As the heat-treatment temperature of the B powder increased, both the particle size of the B powder and crystalline phase increased. In the case of $MgB_2$ samples using B powders heat-treated at above $1300^{\circ}C$, unreacted magnesium (Mg) and B remained due to the improved crystallinity of the B powder. As the heat-treatment temperature of B powder increased, the critical current density of $MgB_2$ decreased continuously due to the reduction of grain boundary density and superconducting volume caused by unreacted Mg and B.

• Progress in Superconductivity
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• v.5 no.2
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• pp.124-127
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• 2004

Many of research efforts have been focused on the improvement of critical current density (Jc) of silver-sheathed Bi-2223 tapes far practical applications. In this study, the transformation of Bi-2212 phase was investigated, which was transformed to orthorhombic from tetragonal through pre-annealing during powder packing and drawing process. The relationship between hardness of Bi-2212 orthorhombic phase and workability of Bi-2223/Ag tape was investigated. Bi-2223 superconducting wires with 55 filaments were fabricated by stacking and drawing process with different heat-treatment histories. Before rolling process, round wires were pre-annealing at 76$0^{\circ}C$ and in a low oxygen partial pressure. We confirmed that pre-annealing step was to transform to Bi-2212 orthorhombic structure from Bi-2212 tetragonal structure and to reduce the formation of second phases. However the breakages were created at Ag-alloy clad during rolling for pre-annealed Bi-22231Ag tapes. Several pre-annealing scenarios were introduced to reduce the breakages during rolling process. Microstructure and critical current density of pre-annealed Bi-2223 superconducting tapes were investigated. We could achieve proper pre-annealing conditions for Ag-alloy clad Bi-2223 superconducting tapes.

• 한국초전도학회:학술대회논문집
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• 2009.07a
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• pp.41-41
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• 2009

• 한국초전도학회:학술대회논문집
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• 2009.07a
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• pp.51-51
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• 2009

• 한국초전도학회:학술대회논문집
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• 2008.08a
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• pp.7-7
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• 2008

• 한국초전도학회:학술대회논문집
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• 2008.08a
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• pp.82-82
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• 2008

• Progress in Superconductivity and Cryogenics
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• v.5 no.3
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• pp.6-10
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• 2003

Silver nano-powder was added to Ma $B_2$ to make (Ag)$_{(x)wt.%}$(Mg $B_2$)$_{(l00-x)wt.%}$ (A $g_{x}$-Mg $B_2$) (10 $\leq$ x $\leq$ 50) composite superconductors to investigate the effect of the Ag nano-powder on the vortex pinning. Pellets made out of the mixed powder were put inside stainless steel tubes, which were sintered at 85$0^{\circ}C$ in Ar atmosphere. No impurity phase was identified for as-rolled samples. However, both the Mg $B_2$ and the A $g_{x}$-Mg $B_2$ composite pellets, when sintered, contain small amount of Mg $B_4$ and MgAg impurity phases. From the magnetization study, it was found that the flux pinning was improved in the high magnetic field region (> 3 T) only when 10w/o Ag was added to Mg $B_2$. The "two step" structures in ZFC M(T) curve gradually increased as the amount of Ag added increased. Pinning centers can be created by adding a suitable amount of Ag nano-powder which is not too large to increase the decoupling between the Mg $B_2$ grains.crease the decoupling between the Mg $B_2$ grains.