• Journal of Powder Materials
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• v.7 no.4
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• pp.205-211
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• 2000

Distribution of $Y_2BaCuO_5$ (211) Particles within $YBa_2Cu_3O_{7-x}/$ (123) grains of melt infiltration processed YBCO oxides was investigated. Processing parameters were a temperature, atmosphere (air and $O_2$) and initial 211 size. The 211 particles were distributed randomly within the 123 grains when the initial 211 size was large, while they made x-like pattern and/or butterfly-like patterns when the 211 size was small. The 211 patterns were more clearly observed in the samples prepared at higher temperatures and under $O_2$ atmosphere. The 211 distribution was explained in terms of the interfacial energy relationship among the solid, particle and melt.

• Journal of the Korean Vacuum Society
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• v.4 no.1
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• pp.40-45
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• 1995

직경 2인치의 YBa2Cu3O7-y 타겟을 사용하여 높은 스퍼터링 기체 압력 하에서 off-axis DC-마그네트론 스퍼터링 방법으로 MgO(100) 단결정 기판 위에 YBa2Cu3O7-y 박막을 c축 방향으로 in-냐셔 성장시킬 때 기판의 접지 여부와 인가전류의 양이 박막 성장에 미치는 여향을 연구하였다. 그 결과 접지 여부는 박막의 초전도 변환온도, 전기수송 특성, 결정 구조적 특성에는 영향을 거의 주지 않는 반면 표면상태에는 상당한 영향을 미치며, 인가전류의 양은 초전도 특성에 많은 영향을 미침을 발견하였다. 기판온도 $670^{\circ}C$, 스퍼터링 기체압력 300mTorr, 아르곤 대 산소 분압비 5:1의 조건에서 인가전류의 최적량은 300-500 mA이었으며 평균 박막 성장속도는 $0.11-0.14AA$/s로 매우 낮았다. 기판의 접지 효과와 낮은 성장속도의 원인에 대해 고찰해 본다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.6
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• pp.438-441
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• 2021

The electrical characteristics of single-crystal composite superconductors produced by a melting process were studied by neutron irradiation. In order to improve the current characteristics of the YBa₂Cu₃O_7-y superconductor, it is necessary to form an effective flux pinning center inside the superconductor. In this study, an increase in flux pinning was attempted through neutron irradiation onto YBa₂Cu₃O_7-y superconductors. The neutron irradiation was performed at 30 MeV for 500 sec, The electrical properties of the superconductors were measured in a magnetic field of 5 Tesla at 50 K using a magnetic properties measurement system (MPMS). After neutron irradiation, the critical current density of the YBa₂Cu₃O_7-y superconductor in a 1 Tesla magnetic field was 1×10⁵ A/cm². Once neutrons were irradiated at 30 MeV and 10 μA for 500 sec, the critical current density was observed to increase significantly. When neutrons are irradiated to a superconductor, micro-defects are created in the superconductor, and they act as flux pinning centers that hold the magnetic field generated when an electric current flows.

• Journal of the Korean Ceramic Society
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• v.31 no.3
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• pp.312-320
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• 1994

Effect of the laser shot number on the particulates density of the pulsed laser deposited YBa2Cu3O7-x thin films and the laser irradiated surface morphology of the YBa2Cu3O7-x bulk target have been investigated. Until 100 laser shots of cumulative irradiation, the films has the particulates density of ~103 mm-2. However, after 100 laser shots, the density was increased more than 10 times. This results has been explained by the change of particulate ejection path with the development of conical structure at the target surface.

• Proceedings of the Materials Research Society of Korea Conference
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• 1993.11a
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• pp.9-9
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• 1993

• Journal of the Korean Vacuum Society
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• v.4 no.2
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• pp.189-193
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• 1995

$YBa_2Cu_3O_{7-y}$ 박막을 c축 방향으로 성장시키는데 고압 스퍼터링 방법이 저압 스퍼터링 방법에 비해 효과적인 것으로 알려져 있다. 우리는 500mtorr의 고압 스퍼터링 방법을 사용하여 $YBa_2Cu_3O_{7-y}$ 박막을 $\alpha$축으로 성장시키는 연구를 수행하였다. 저압 스퍼터링 방법을 사용할 때보다 낮은 기판온도에 $\alpha$축 방향 성장이 이루어지며, 저압 스퍼터링 성장의 경우와는 달리 산소분압의 크기에 따라 성장 방향이 달라지지 않음을 발견하였다. 성장된 박막은 기대와 달리 매우 낮은 초전도 전이온도와 열등한 구조적 특성표면 특성을 보였다.

• Electrical & Electronic Materials
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• v.6 no.4
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• pp.318-323
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• 1993

본 연구에서는 rf magnetron 스퍼터링으로 (100) 사파이어 기판에 퇴적시킨 YBa$_{2}$Cu$_{3}$$O_{7-x}$박막을 열처리하기 위하여 급속 열처리 방법을 사용하였다. XRD, AES, 그리고 4단자 비저항 측정법을 사용하여 급속 열처리로 형성시킨 초전도체 박막과 기판사이의 상호확산을 조사하였다. 제조된 박막은 91K에서 Tc(onset)를 80K에서 Tc(zero)를 나타내었다. AES 분석 결과, 급속 열처리 방법의 경우 YBa$_{2}$Cu$_{3}$$O_{7-x}$ HTS 박막과 기판사이의 계면에서 항호확산이 감소되는 것을 확인하였다. XRD 분석 결과, 급속 열처리에 의해 형성된 HTS 박막은 주로 c-축이 기판의 표면에 수직인 구조를 가지고 있었다.

• Progress in Superconductivity
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• v.2 no.2
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• pp.71-75
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• 2001

The effect of annealing step-edges of LaAlO$_3$ and MgO single crystal substrates on YBa$_2$Cu$_3$O$_{7}$ junction has been studied. The step-edge was fabricated by argon ion milling and was annealed at 105$0^{\circ}C$ in 1 attn oxygen pressure. We compared AFM image near step-edge of the substrates between before and after annealing process. And YBa$_2$Cu$_3$O$_{7}$ thin film was deposited on the step-edge by a standard pulsed laser deposition. The step-edge junctions were characterized by current-voltage curves at 77 K. The annealing of step-edges of MgO substrate improved the current-voltage characteristic of Josephson junction: double steps in the current-voltage characteristic disappeared. However the annealing for LaAlO$_3$ did not improve the junction property.rty.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.4
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• pp.221-225
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• 1999

This paper shows the parameters to affect the critical characteristic of YBaCuO superconducting bulk fabricated by MPMG (Melt Powdered Melt Growth)process. In order to investigate proper processing variables, the effect of the holding time at the melting temperature and that of the slow cooling time in $O_2\; ambient\; on\; the\; J_c$ were experimented. And then with the above obtained heat treatment conditions, the effects of addition of $Y_2BaCuO_5\; and\; Ag\; on\; the\; J_c$ were also investigated. A proper slow cooling time yields phase transformation from Tetragonal $(YBa_2Cu_3O_6)$ to Orthorhombic $(YBa_2Cu_3O_7)$ during an annealing time in $O_2$. Ag addition plays a role in increasing the $T_c\; and\; the J_c$, but the magnetization decreases. The $J_c$ and the magnetization increase with addition of Y211. $J_c$ of the sample added Ag 10wt% is superiorover 3000 G. Proper holding time, slow cooling time and amount of impurity addition are important parameters in fabricating the YBaCuO bulk by MPMG process with high $J_c$.

• Journal of the Korean Ceramic Society
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• v.28 no.1
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• pp.86-89
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• 1991