• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.05a
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• pp.26-30
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• 1995

We describe the preparation and characterization of epitaxial thin films made with high temperature superconductor, $YBa_2Cu_3O_{7-\delta}$. The influence of processing parameters for YBCO thin films on MgO substrates in-situ grown by the pulsed laser deposition, including parameters of a laser beam energy, oxygen pressure, substrate temperature, target-substrate dis-tance is discussed. The characteristics of YBCO thin films were analyzed by using XRD, R-T measurement, AFM, crosssectional TEM, and RBS. For examples of microwave device applications, The fabrication and characterization of the microstrip lowpass filter and bandpass filter are also presented.

• Journal of the Korean Ceramic Society
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• v.30 no.12
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• pp.1007-1014
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• 1993

YBa2Cu3Ox(YBCO) thick films were prepared by a screen printing of the powders, obtained by a coprecipitation in oxalic acid, on the Y2O3-stabilized zirconia substrates and their superconducting properties were determined. TC, JC and the orientation factor of the thick films increased with increasing temperature up to 103$0^{\circ}C$ and then the superconducting properties disappeared with further heat treatments. The optimization of JC was achieved by heating thick films at 103$0^{\circ}C$ for 7min. In this case the TC of the thick film was determined to be 87.5K. It was observed that TC of thick films depends on the orthorhombicity and JC is likely governed by a microstructure of YBCO rather than by the orientation factor.

• Journal of the Korean Ceramic Society
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• v.26 no.3
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• pp.395-401
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• 1989

The concentrations of Cu(II), Y(III) and Ba(II) ionic species in aqueous solution due to the formation of Cu2+-oxalate-complex have been theoretically calculated with respect to pH and their solubility diagrams could be obtained. It was verified from the calculation that the excess of Cu2+ and Ba2+ should be added in order to obtain oxalate coprecipitates with the molar ratio of Y : Ba : Cu=1 : 2 : 3. The exact amount of excess species has been calculated with respect to the initial concentrations of metal ions and pH.

• Journal of the Korean Ceramic Society
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• v.25 no.2
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• pp.154-160
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• 1988

Almost single phase of Y1Ba2Cu3Ox, which exhibits the onset of superconducting transition at 90K, has been prepared via a conventional ceramic processing route followed by an anneal for a period of 10 hours at 45$0^{\circ}C$ in an atmosphere of 100% O2. The mean value for the oxygen content has been determined as x=6.85$\pm$0.02 by an iodometric titration technique. X-ray photoemission spectra are found to be consistent with a mixture of the d8(Cu3+) and d9(Cu2+) as the ground state and reveals that the local concentration of Cu3+ decreases with depth from the surface where x corresponds to 7.0. This is explained as being associated with the intercalation of oxygen during cooling from the annealing temperature.

• Progress in Superconductivity
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• v.6 no.2
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• pp.129-132
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• 2005

The formation behavior of $YBa_2Cu_3O_{7-x}$(Y123) and CuO phases in the heat-treated Cu-sheathed YBCO thick films was studied. The thick films were prepared by screen-printing method using $BaCO_3$ and Y211 powders on Cu tapes. The screen-printed thick films were placed at the center of the tube furnace, heated to $930^{\circ}C$ in air atmosphere and then maintained at the temperature for 60 sec - 300 sec. The microstructure and phases formed in the thick films were investigated by using optical microscope, X-ray diffraction (XRD) and SEM image analysis. During the heat treatment, partial melting occurred rapidly in the printed layers by peritectic reaction between CuO and precursor powders, and then YBCO superconducting phases nucleated from the Cu tapes and grew in a form of thick films.

• Proceedings of the KIEE Conference
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• 1989.07a
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• pp.299-301
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• 1989

This study presents a method of preparing $YBa_2Cu_3O_{7-x}$ ceramic and chlorine doping in it for the purpose of Jc enhancement us ins sol-gel process.Tetramethylammonium-hydroxide and pottasium carbonate solution were added to the aqueous solution of Yttrium nitrate, Barium chloride and Copper nitrate for pH control as well as forming hydroxy-carbonate precipitation. Instead of Barium nitrate, Barium chloride was used for doping chloride impurities in the specimen. The resulted materal showed good high Tc-superconductivity after calcination. Tc and Jc value are 92 K and 120.8 $A/cm^2$ respectively.

• Journal of the Korean Ceramic Society
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• v.28 no.1
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• pp.37-45
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• 1991

The critical current density, electrical conductivity, critical magnetic field, Meissner effect, apparent density, and microstructure of YBa2Cu3O7-x ceramic superconductor prepared by polymeric precursor, while varing calcining and sintering conditions, were investigated. The best superconducting properties could be obtained from the body sintered at 93$0^{\circ}C$ for 10h after calcining at 90$0^{\circ}C$ for 10h, which gave 383A/$\textrm{cm}^2$ of critical current density(Jc), 96K of onset temperature(Tonset), 94. 8K of zero temperature (Tzero) 225 Oe of critical magnetic field (Hc1), 72.8% of superconducting volume fraction measured by Meissner effect and 6.28g/㎤ of apparent density.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.85-88
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• 1999

We fabricated resistive superconducting fault current lmiters based on YBa$_2$Cu$_3$O$_{7}$ thin films and investigated their quench propagation characteristics. The YBa$_2$Cu$_3$O$_{7}$ film was coated with a gold layer and patterned into 1 mm wide meander lines by photolithography. The limiters were tested with simulated fault currents of various fault angles and amplitudes. The quench propagation characteristics were explained based on the heat transfer within the film as well as between the film and the surrounding liquid nitrogen. The quench completion time strongly depended on the potential fault current. It was 1 msec at the peak fault current of 76 A/peak/ and corresponding quench propagation speed was 43 m/sec (film cross section: 4 x 10$^{-6}$ $\textrm{cm}^2$).

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 1999.02a
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• pp.43-46
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• 1999

The microstructure of Top Seed Milt-Processed $YBa_{2}$$Cu_{3}$$O_{7-\delta}$ single crystal was studied. It was presumed that the segregation of Y211 is due to the difference of growth rates between a, b axis and c axis in crystal direction. Corn kernel lide structure which was grown by the diffusion of Y211 was observed. At the near corner of the seed crystal, the diagonal line on Y123 cry crystal is formed by the corn kernel like structure.

• Proceedings of the KIEE Conference
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• 1990.11a
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• pp.143-149
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• 1990

A sol-gel processing of $YBa_2Cu_3O_{7-x}$ superconductor using metal nitrate salts and sodium hydroxide as the starting materials has been investigated because of the need to produce pure, hompgeneous superconducting materials. Since the precipitation of barium hydroxides can be obtained only at high basicities, the process has to be carried out Ca. pH 13 to get the simultaneous coprecipitation with the other metal hydroxides. The involved reaction mechanisms were investigated and intermediate and final products were characterized by means of thermogravimetric analysis(TGA), infra-red(IR) spectroscopy, X-ray diffraction(XRD) analysis, scanning electron microscopy(SEM), thermal mechanical analysis(TMA) and electrical measurement.