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MOD-processed YBCO coated conductor on the IBAD-MgO template
신거명,고락길,송규정,유재무,오상수,문승현,유상임 한국초전도.저온공학회 2007 한국초전도저온공학회논문지 Vol.9 No.4
We report the results of MOD-processed YBCO coated conductors on the IBAD-MgO template. The precursor solution was coated on the CeO2-buffered IBAD-MgO template using a slot-die coating method, calcined at a temperature of 550oC, and fired at high temperatures for 2.5 h in a reduced oxygen atmosphere. The JC value of YBCO coated conductors was found to be very sensitive to the microstructure, and thus higher JC value could be achieved when the in-plane texture was higher and the difference in TC,zero was negligible. Optimally processed YBCO coated conductor exhibited JC value of 0.75 MA/cm2 at 77 K in self-field, which might be due to somewhat depressed TC,zero value of 87.3 K caused by possible Sm3+ substitution on the Ba2+ site.
Fabrication of YBCO films on metal tapes by the TFA-MOD process
신거명,송규정,박찬,문승현,유상임,Shin Geo-Myung,Song Kyu-Jung,Park Chan,Moon Seung-Hyun,Yoo Sang-Im The Korean Superconductivity Society 2005 Progress in superconductivity Vol.7 No.1
YBCO thin films on metal substrates were prepared by the metal-organic deposition using trifluoroacetates (TFA-MOD). To compensate the loss of Ba element from the precursor films due to the reaction with $CeO_2$ cap layer, we have employed Ba-excessive precursor solutions of $YBa_{2+x}Cu_{3}O_{7-{\delta}}$ ($0{\le}x{\le}0.1$). The precursor solutions were dip-coated on the metal substrates with $CeO_2$ cap layer, initially heated up to $400^{\circ}C$, and finally fired at the various high temperatures for 2 h in a reduced oxygen atmosphere. With this approach, YBCO films possessing critical temperature over 85 K could be successfully prepared on the metal substrates. The highest $T_{c,zero}$ value of 86 K was obtained from the Ba-excessive YBCO film of x=0.005 in $YBa_{2+x}Cu_{3}O_{7-{\delta}}$ fired at $750^{\circ}C$ for 2 h. However, unexpected $T_c$ suppression even in Ba-excessive YBCO samples requires further identification.
MOD-processed YBCO coated conductors on the CeO2-buffered IBAD-MgO template
신거명,고락길,오상수,문승현,유상임 한국초전도.저온공학회 2009 한국초전도저온공학회논문지 Vol.11 No.4
YBCO coated conductors (CC) on the CeO2-buffered IBAD-MgO template were fabricated by metal-organic deposition (MOD) process with Ba-trifluoroacetate and fluorine-free Y and Cu precursor materials. The precursor solution was coated on CeO2-buffered IBAD MgO templates using the multiple dip-coating method, decomposed into inorganic precursors by pyrolysis up to 400 oC within 3 h, and finally fired at 740~800 oC in a reduced oxygen atmosphere. Microstructure, texture, and superconducting properties of YBCO films were found highly sensitive to both the firing temperature and time. The high critical current density (JC) of 1.15 MA/cm2 at 77.3K in the self-field could be obtained from 1 μm thick YBCO CC, fired at 740 oC for 3.5 h, implying that high performance YBCO CC is producible on IBAD MgO template. Further enhancement of JC values is expected by improving the in-plane texture of CeO2-buffer layer and avoiding the metal substrate contamination.
Phase and microstructure evolution during the TFA-MOD process of YBCO films
위성훈,신거명,홍계원,유상임 한국초전도.저온공학회 2007 한국초전도저온공학회논문지 Vol.9 No.2
We report the phase and microstructureevolutions of metal trifluoroacetate (TFA) precursor films in the TFA-MOD process of YBCO films on the LAO (100) substrates. It was confirmed that the precursor films were decomposed into Y2O3, BaF2, and CuO nanoparticles after the initial heat treatment up to 400C. After a subsequent 850C for 2 h, these nano-sized phases are converted into YBCO films. High Jc(77K, sf)-YBCO thin films (over 2 MA/cm2) were successfully fabricated with firing temperatures ranging from 775 to 850oC for 2 h, where films were composed of dense microstructures with large grains.
Optical investigation of high critical-current Gd₁+xBa₂-xCu₃O7 coated conductors
김그라시아,조윌렴,박도형,정현식,신거명,유상임 한국초전도.저온공학회 2008 한국초전도저온공학회논문지 Vol.10 No.2
Gd₁+xBa₂-xCu₃O7 (GdBCO) coated conductors on IBAD-MgO templates have grown by pulsed laser deposition. Critical current of the films were measured as about 90 A/cm by a four-probe method. The optical response of the films was investigated by Raman scattering spectroscopy. According to the Raman scattering spectra, the peaks at 328 cm-¹, 451 cm-¹, 504 cm-1 were found and assigned to one B1g mode and two A1g modes, respectively. The high critical-current carrying behaviors of the GdBCO coated conductors are ascribed to their 123-structure without exchange of cation and incorporation of oxygen into the cuprates.