• Proceedings of the Korea Crystallographic Association Conference
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• 2003.05a
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• pp.12-12
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• 2003

초전도 선재로의 응용을 위하여 Pulsed laser deposition(PLD)법으로 고온 초전도 체 YBa₂Cu₃O/sub 7-δ/(YBCO) coated conductor를 제조하였다. coated conductor는 금속기판/완충층/초전도층의 구조를 이루고 있는데 완충층은 금속 기판의 집합조직을 초전도층까지 전달하는 역할과 금속기판의 금속이 초전도층으로 확산되어 초전도층의 전기적 특성을 열화시키는 것을 막아주는 확산장벽으로의 역할 등을 수행한다. 완충층의 박막 성장이 제대로 이루어지지 않으면 우수한 초전도 특성을 가지는 초전도층을 얻을 수 없다. 완충층은 금속기판과의 lattice match, thermal match등이 요구되고, 화학적으로 금속기판 및 초전도층과 반응하지 않아야 하며, 긍속기판의 산화없이 epitaxial하게 박막증착이 이루어질 수 있는 재료이어야 한다. 이러한 조건을 만족하는 YBCO, CeO₂, YSZ 등이 주로 사용되고 있다. 전기연구원에서 YBCO coated conductor 선재를 제조하기 위하여 사용하고 있는 다층 박막의 구조는 YBCO/CeO₂/YSZ/CeO₂/Ni(002)과 YBCO/CeO₂/YSZ/Y₂O₃/Ni(002)이며, 최적의 증착조건을 찾기 위하여 성장시 챔버의 산소분압, 완충층의 두께, 기판 온도 등을 변화시켰다. 증착된 완충층 및 초전도층의 집합 조직은 D8-Discover with GADDS(General Area Detector Diffraction System)로 XRD분석을 했고, 미세구조는 SEM으로 관찰하였으며 4단자법을 이용하여 초전도 특성을 측정하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.290-291
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• 2008

Recently High Temperature Superconductor(HTS) Tape is limelight of the applied superconducting machines. Mainly used superconducting tape are BSCCO tape and YBCO coated tape. These superconducting tape are applied such as SMES, superconducting generator and MAGLEV. Actually superconductor tape's experimental gauge is short. For this reason, experiment was conducted. Firstly length of 50cm BSCCO, YBCO Coated conductor@Cu and YBCO coated conductor@sus are prepared. and flow the over-current. Secondly, BSCCO and Coated conductor connected with lenth of 25cm and flow the over-current. Coupled line of HTS tape was compared with single line of HTS tape and these overcurrent characteristics was investigated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05a
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• pp.30-33
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• 2003

YBCO coated conductor, also called the 2nd generation high temperature superconducting wire, consists of oxide multi-layer hetero-epitaxial thin films. Pulsed laser deposition (PLD) is one of many film deposition methods used to make coated conductor, and is the one known to be the best to make superconducting layer so far. As a part of the effort to make long length coated conductor, the optimum deposition condition of YBCO film on single crystal substrate (SrTiO3) was investigated using PLD. Substrate temperature, oxygen partial pressure, and laser fluence were varied to find the best combination to grow high quality YBCO film.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.1998-2000
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• 2005

The effects of the addition of nanocrystalline Y2O3 powder on the microstructure and superconducting properties have been investigated in YBCO films prepared by TFA-MOD process. Precursor solution doped with extra $Y_2O_3$ Powder was prepared by adding $Y_2O_3$ powder into a stoichiometic precursor solution with a cation ratio of Y:Ba:Cu=1:2:3. Coating solutions with and without $Y_2O_3$ doping were coated on $LaAlO_3(100)$ single crystal by a dip coating method, cacination and conversion heat treatments were performed at the controlled atmosphere containing water vapor Current carry capacity(Jc) of YBCO film was enhanced about 50% by $Y_2O_3$ doping. It is thought that the enhancement of Jc is due to the better connectivity of YBCO grains and/or the flux pinning by the presence of nanocrystalline $Y_2O_3$ Particles embedded in YBCO grains.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.12a
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• pp.33-34
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• 2006

The effects of Ba and Ce addition has been investigated in YBCO prepared by trifluoroacetate (TFA) metalorganic depostition (MOD) method. Precursor solutions with cation ratios of Y:Ba:Cu:Ce = 1:2+x:3:x (x = 0, 0.05, 0.1 and 1.5) have been prepared by adding an excess amount of cerium and barium. Coated film was calcined at lower temperature and conversion heat treatment at temperature of $780{\sim}810^{\circ}C$. It has been shown that the critical current (Ic) of YBCO film was degraded by doping of Ba and Ce atoms. But Ic was increased as the amount of doped Ba and Ce content increased from 5 % to 15 %. It was observed that there was little increase of a flux pinning force with Ba and Ce addition in YBCO film prepared by TFA-MOD process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.268-269
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• 2005

YBCO 박막형 초전도체(coated conductor) 제조를 위해서는 여러 층의 완충층이 필요하다. 현재 일반적인 완충층의 구조는 seed layer로써 $Y_2O_3$, diffusion barrier로 YSZ, capping layer로 $CeO_2$가 사용되고 있다. 특히, capping layer로 $CeO_2$는 YBCO와 lattice mismatch가 매우 우수한 산화물로 이용되고 있다 본 연구에서는 $CeO_2$ capping layer가 증착 방법에 따라 그 위에 증착되어지는 초전도층의 특성에 어떤 영향을 미치는지 연구하였다. $CeO_2$를 thermal evaporation과 PLD (pulsed laser deposition) 증착 방법으로 증착 한 후 그 위에 PLD 방법으로 YBCO를 증착하여 coated conductor의 성능을 평가하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.10
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• pp.860-863
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• 2009

YBCO bulks with fine $Y_2BaCuO_5$(Y211) particles have been prepared by the top-seed modified powder melting process method, Solid-Liquid Melt Growth(SLMG), with $Y_2O_3$, $BaCuO_2$ and CuO mixing precursor. By using $Y_2O_3$ instead of $Y_2BaCuO_5$ as precursor, the processing became to be simpler and cheaper than the current powder melting process. The microstructures, trapped field and critical current density of the various conditioned YBCO bulks have been analyzed and the effect of Pt additive was studied. The different trapped magnetic field values of the several samples have been explained in the viewpoint of their microstructures. The fabrication of large-sized YBCO single domain has been conducted.

• Progress in Superconductivity and Cryogenics
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• v.21 no.3
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• pp.27-31
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• 2019

Large grain YBCO bulk superconductors are fabricated by the top-seeded melt growth (TSMG) or top-seeded infiltration growth (TSIG) method. Both growth methods use at least one of $YBa_2Cu_3O_{7-{\delta}}$, $Y_2BaCuO_5$, $BaCuO_3$ pre-reacted precursor powders. However, the synthesis of the pre-reacted powders includes multiple calcination runs which are cost-bearing and time-consuming. In this work, we report the successful growth of single-domain YBCO bulk superconductors directly by using the powder compact that has been pressed from the mixture of $Y_2O_3$, $BaCuO_3$ and CuO powders without any intermediate grinding step. Single-domain YBCO bulk superconductor has been also prepared by using $Y_2O_3$, $BaO_2$ and CuO powders without intermediate grinding step. Investigations on the trapped magnetic field and microstructure of the melt-processed specimen show that the elimination of the repeated processes of calcinations and pulverization has hardly affected on the crystal growth and the magnetic properties of the grown YBCO bulk superconductors. However, it is thought that the presence of residual carbon affects on the size of Y211 particles in melt-processed YBCO bulk superconductor.

• Progress in Superconductivity and Cryogenics
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• v.22 no.4
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• pp.14-19
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• 2020

Here we present the comparative experimental study of the stability of the superconducting state in 4 mm YBCO tapes with copper lamination against local heat disturbances at 77 K. The samples are either directly cooled by immersing a bare YBCO tape into a liquid nitrogen pool or operate in nearly-adiabatic conditions when the tape is covered by a 0.6 mm layer of Kapton insulation. Main quench characteristics, i.e. minimum quench energies (MQEs) and normal zone propagation (NZP) velocities for both samples are measured and compared. Minimum NZP currents are determined by a low ohmic resistor technique eligible for obtaining V - I curves with a negative differential resistance. The region of transport currents satisfying the stationary stability criterion is found for the different cooling conditions. Finally, we use the critical temperature margin as a universal scaling parameter to compare the MQEs obtained in this work for YBCO tapes at 77 K with those taken from literature for low-temperature superconductors in vacuum at 4.2 K, as well as for MgB2 wires cooled with a cryocooler down to 20 K.

• Progress in Superconductivity and Cryogenics
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• v.12 no.3
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• pp.7-11
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• 2010

For many large-scale applications of high-temperature superconducting materials, large critical current density($J_c$) in high applied magnetic fields are required. A number of methods have been reported to introduce artificial pinning centers(APCs) in $YBa_2Cu_3O_{7-\delta}$(YBCO) films for enhancement of their $J_c$. In this work, we investigated electric characteristic of YBCO films on $SrTiO_3$ (100) substrates whose surfaces were modified by the introduction of Au nanoparticles (AuNPs). Au nanoparticles were uniformly dispersed on STO substrates with one of typical solution techniques, self assembled monolayer. After heating the STO substrates with Au nanoparticles, the size of Au nanoparticles was around 29~32 nm in height and 41~49 nm in diameter. XRD diffraction patterns taken on the YBCO film with Au nanoparticles show the c-axis orientation. The measured $T_c$ of YBCO /AuNPs films was around 89K and the $J_c$ was 0.75 MA/$cm^2$ at 65 K and 1 T.