• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.189-191
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• 1994

YBCO bulks for levitation have fabricated using MPMG method. The superconducting properties and repulsive/attractive force against permanent magnet were investigated for the specimens annealed at various periods after MPMG. A linear induction motor type levitation - traveling vehicle using the pinning force of MPMG processed YBCO bulk has fabricated. The floating or hanging small vehicle mounted with two YBCO pellets was confirmed to travel stabley on the Nd-Fe-B permanent magnet track. The traveling speed of the vehicle was confirmed to depend on AC frequency linearly. At 200 Hz, the travel ins speed was found to be 110 cm/sec.

• Journal of Magnetics
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• 제19권2호
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• pp.140-145
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• 2014

The electrical transport properties of YBCO single layers thin film have been investigated using different physical techniques. For the purpose, the physical properties are probed numerically with help of simulation modelling. The physical transport properties were also estimated with temperature and magnetic fields limits using thermally-activated flux flow model with some modifications. The result of present simulation modelling indicated that the magnitude of activation energy depends on temperature and magnetic field. The simulations revealed thickness dependent physical transport properties including electrical and magnetic properties of deposited YBCO single layers thin films. Furthermore, it shows the temperature dependence of the pinning energy. In the nutshell, the result can be used to improve the Superconducting Properties ($T_c$) of the YBCO single layers thin films.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.288-288
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• 2008

The flux-coupling type superconducting fault current limiter(SFCL) is composed of a series transformer and superconducting unit of the YBCO thin films. The primary and secondary coils in the transformer were wound in series each other through an iron core and the YBCO thin film was connected with secondary coil in parallel. In a normal condition, the flux generated from a primary coil is cancelled out by its structure and the zero resistance of the YBCO thin films. When a fault occurs, the resistance of the YBCO thin films was generated and the fault current was limited by the SFCL. In this paper, we investigated the fault current limiting characteristics according to fault current level in the flux-coupling type SFCL. The experiment results that the fault current limiting characteristics was improved according to increase of the fault current level.

• 한국전기전자재료학회논문지
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• 제11권7호
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• pp.541-545
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• 1998

(PZT, PST, PT)/ YBCO structured have been grown on single crystal $LaAlO_3$ using in-situ Nb:YAG pulsed laser deposition technique. The optimum conditions of fabrication for high quality films have been established under various oxygen pressure. TBCO was used as a metallic electrode for polarizing ferroelectric thin fillms. Lattice mismatch of these materials were found to be with in 3%. As a result XRD patterns and rocking curves, (PZT, PST, PT)/ YBCO multiayered thin films on $LaAlO_3$ substrates showed preferred orientation to c-axis. For invastigation on electrical properties of ferroelectric thin films, remanent polaiztion $P_r$ and coercive field $E_c$ were measured for three samples. At each optimum condition, they showed the values of P_r=60 \mu C/cm^2 and E_c=240kV/ cm for PT, 30\mu C/cm^2 and 105kV/cm for PZT, 1.5\mu C/cm^2$ and 15kV/cm for PST. Frequency dependence of dielectric properties of ferroelectric thin fillms was also investigated. As a result, it showed the frequency dependence was relatively small in the range of 10Hz~10kHz.

• 한국초전도ㆍ저온공학회논문지
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• 제13권4호
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• pp.22-25
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• 2011

A single-coat $YBa_2Cu_3O_{7-{\delta}}$ (YBCO) film of high critical currents ($I_c$) could be successfully fabricated by optimizing the viscosity of the coating solution in the metal-organic deposition (MOD) process. From a Ba-deficient coating solution (Y: Ba: Cu = 1: 1.5: 3) having the viscosity of 212 $mPa{\cdot}sec$, 0.9 ${\mu}m$-thick single coat YBCO film with the $I_c$ value of 289 A/cm-width ($J_c$ = 3.2 MA/$cm^2$) at 77 K was achievable on the $SrTiO_3$ (STO) substrate, which was superior to that of our previous report for 0.8 ${\mu}m$-thick single coat YBCO film from a stoichiometric coating solution (Y: Ba: Cu = 1: 2: 3) on the $LaAlO_3$ (LAO) substrate. This result might be attributed to denser and more homogeneous microstrcuture in the case of the YBCO film from the Ba-deficient coating solution.

• 한국초전도ㆍ저온공학회논문지
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• 제21권4호
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• pp.19-23
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• 2019

A large grain YBCO bulk superconductor is fabricated by the top-seeded melt growth (TSMG) method. In the TSMG process, the seed crystal is placed on the top surface of a partially melted compact and therefore the seed crystal is frequently tilted during the melt process due to intrinsic unstable nature of Y211 particle +liquid phase mixture. In this work, we report the successful growth of single-domain YBCO bulk superconductors by a bottom-seeded melt growth (BSMG) method. Investigations on the trapped magnetic field and the microstructures of the synthesized specimens show that a bottom-seeded melt growth method has hardly affected on the crystal growth behavior, the microstructure development and the magnetic properties of the large grain YBCO bulk superconductors. The bottom-seeded melt growth method is clearly beneficial for the stable control of seed orientation through the melt process for the fabrication of a large grain YBCO bulk superconductor.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.259-262
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• 2003

Superconducting flux flow transistor(SFFT) is based on a control of the Abrikosov vortex flowing along a channel. The induced voltage by moving of the Abrikosov vortex in SFFT is greatly affected by the thickness and width, of channel. In order to fabricate a reproducibility channel in SFFT, we have researched the variation of the critical characteristics of YBCO thin films with the etching time using ICP(Inductively coupled plasma) system. It was certified that the velocity of vortex decreased with increasing the width of channel and was saturated faster in low bias from a simulation. An etching mechanism of YBCO thin films by ICP system was also certified by AFM(Atomic Force Microscope) and by measuring the critical current density with etching time. As measurement result, we could analyze that we should optimize the etching thickness of channel part to construct a flux flow transistor with desired characteristics.

• 한국초전도ㆍ저온공학회논문지
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• 제11권3호
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• pp.10-14
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• 2009

Since a stabilizer of YBCO coated conductor (CC) plays a very important role of bypassing over-current and transferring heat generated in the moment of fault, it is one of big issues to determine the material of the stabilizer and its dimension for the high performance of the HTS power application system. Especially, in the case of a superconducting fault current limiter (SFCL), which requires it to react immediately to the occurrence of fault, characteristics of stabilizer are decisive in limiting fault current and recovering superconducting properties during and after quenching. In this paper, the quench / recovery characteristics of YBCO CCs with various thickness of stabilizer were analyzed. The quench/recovery test carried out at 20 $V_{rms}$, 5 cycles (60 Hz) and results showed that as the thickness of the stabilizer decreased, both the final approach temperature and the recovery time decreased.

• 한국초전도ㆍ저온공학회논문지
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• 제11권4호
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• pp.20-24
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• 2009

YBCO coated conductors (CC) on the $CeO_2$-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 $CeO_2$-buffered IBAD MgO templates using the multiple dip-coating method, decomposed into inorganic precursors by pyrolysis up to $400^{\circ}C$ within 3 h, and finally fired at $740{\sim}800^{\circ}C$ 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 ($J_C$) of $1.15\;MA/cm^2$ at 77.3K in the self-field could be obtained from $1\;{\mu}m$ thick YBCO CC, fired at $740^{\circ}C$ for 3.5 h, implying that high performance YBCO CC is producible on IBAD MgO template. Further enhancement of $J_C$ values is expected by improving the in-plane texture of $CeO_2$-buffer layer and avoiding the metal substrate contamination.

• 한국초전도ㆍ저온공학회논문지
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• 제11권3호
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• pp.15-19
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• 2009

Recently, it is proposed to make striations on the YBCO coated conductor and to transpose each other as one of the solutions to decrease the perpendicular magnetization loss. For large power application using HTS, the stacked conductor packing the YBCO coated conductors should be used because single conductor is limited in flowing of demanded large current. In this paper, we research the affect of the striation and continuously transposed stacking geometry on the magnetization loss in perpendicularly exposed magnetic field. Several short samples having different number of striation and continuously transposed stack are prepared and tested in perpendicularly exposed magnetic field for the magnetization loss characteristics. The magnetization loss of striated sample was lower than sample without striation. The reduction effect on magnetization loss by the striation is obviously appeared in higher field and lower number of stack and decreased as increasing the transposed stacking number. Also, the reduction effect by transposed stack is obviously appeared in lower field at lower number of striation and isn't appeared at higher striation number and higher magnetic field.