• Title/Summary/Keyword: superconductors

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Milling Effects of $Y_2BaCuO_5$ Precursor Powder with $CeO_2$ Addition on the Critical Current Density of Liquid Infiltration Growth Processed $YBa_2Cu_3O_{7-y}$ Bulk Superconductors (액상 침투 성장법으로 제조된 $YBa_2Cu_3O_{7-y}$ 벌크 초전도체의 임계전류밀도에 대한 $CeO_2$ 첨가된 $Y_2BaCuO_5$ 분말의 밀링 효과)

  • Asif, Mahmood;Jun, Byung-Hyuk;Kim, Chan-Joong
    • Progress in Superconductivity
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    • v.12 no.1
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    • pp.6-11
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    • 2010

  • The milling effects of a precursor $Y_2BaCuO_5$ (Y211) powder having 1 wt.% $CeO_2$ on the microstructure and critical current density ($J_c$) of liquid infiltration growth (LIG) processed $YBa_2Cu_3O_{7-y}$ (Y-123) bulk superconductors were investigated. The microstructure analysis revealed that the Y211 size in the final Y-123 products decreased with increasing the milling time and a relatively high density and uniform distribution of Y211 inclusions were observed in the sample prepared using 8 h milled powder. However, the unexpected Y211 particles coarsening was observed from the 4 h milled sample which was further increased for 10 h milled sample. Critical current density ($J_c$) of the LIG processed Y-123 bulk superconductors was found to be dependent on the milling time of the Y211 precursor powder. The $J_c$ increased with the increase of milling time and reached up to a maximum at 8 h in the self field while 10 h milled sample showed lower $J_c$ at the same field which might be due to the exaggerated growth and non-uniform distribution of Y211 particles.

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Effects of artificial holes on the cooling efficiency of single grain Y1.5Ba2Cu3O7-y bulk superconductors (단결정 Y1.5Ba2Cu3O7-y 벌크 초전도체의 냉각효율에 대한 인공 구멍의 효과)

  • Kim, Kwang-Mo;Park, Soon-Dong;Jun, Byung-Hyuk;Ko, Tae-Kuk;Kim, Chan-Joong
    • Progress in Superconductivity and Cryogenics
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    • v.14 no.3
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    • pp.1-4
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    • 2012

  • Effects of artificial holes on the cooling efficiency of single grain YBCO bulk superconductors were studied. Single grain YBCO bulk superconductors without artificial holes, with six 2.4 mm holes and six holes filled with Bi-Pb-Cd-Sn metal solder were fabricated by a top-seeded melt growth process for powder compacts with/without holes. Simulation for the cooling rate to a liquid nitrogen temperature (77 K) of YBCO samples was carried out using a finite element method (FEM) and the results are compared with the actual cooling rates of samples in liquid nitrogen. The simulated cooling times for the YBCO sample without holes, with six holes and with six holes filled with the metal solder were 80, 47 and 75 sec. respectively, which are similar to the actual cooling times of 84, 52 and 78 sec. estimated for the same samples cooled in liquid nitrogen. The shorter cooling time of the sample with artificial holes are attributed to the increased surface areas associated with the presence of artificial holes. The metal filling into the holes did not give any remarkable effect on the cooling efficiency.

  • https://doi.org/10.9714/sac.2012.14.3.001 인용 PDF KSCI

Synthesis of YBa2Cu3O7-y Powder using a Powder Reaction Method and Fabrication of the Bulk Superconductors (분말 반응법에 의한 YBa2Cu3O7-y 합성과 벌크 초전도체의 제조)

  • Jeon, Young Ju;Park, Seung Yeon;You, Byung Youn;Park, Soon-Dong;Kim, Chan-Joong
    • Journal of Powder Materials
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    • v.20 no.2
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    • pp.142-147
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    • 2013

  • $YBa_2Cu_3O_{7-y}$ (Y123) powders for the fabrication of bulk superconductors were synthesized by the powder reaction method using $Y_2O_3$ (99.9% purity), $BaCO_3$ (99.75%) and CuO (99.9%) powders. The raw powders were weighed to the cation ratio of Y:Ba:Cu=1:2:3, mixed and calcined at $880^{\circ}C-930^{\circ}C$ in air with intermediate repeated crushing steps. It was found that the formation of Y123 powder was more sensitive to reaction temperature than reaction time. The calcined Y123 powder and a mixture of (Y123 + 0.25 mole $Y_2O_3$ + 1 wt.% $CeO_2$, $Y_{1.5}Ba_2Cu_3O_x$ (Y1.5)) were used as raw powders for the fabrication of poly-grain or single grain superconductors. The superconducting transition temperature ($T_{c,onset}$) of the sintered Y123 sample was 91 K and the transition width was as large as 11 K, whereas the $T_{c,onset}$ of the melt-grown Y1.5 sample was 90.5 K and the transition width was 3.5 K. The critical current density ($J_c$) at 77 K and 0 T of the sintered Y123 was 700 $A/cm^2$, whereas the $J_c$ of the top-seeded melt growth (TSMG) processed Y1.5 sample was $3.2{\times}10^4\;A/cm^2$. The magnetic flux density (H) at 77 K of the TSMG-processed Y123 and Y1.5 sample showed the 0.53 kG and 2.45 kG, respectively, which are 15% and 71% of the applied magnetic field of 3.5 kG. The high H value of the TSMG-processed Y1.5 sample is attributed to the formation of the larger superconducting grain with fine Y211 dispersion.

  • https://doi.org/10.4150/KPMI.2013.20.2.142 인용 PDF KSCI