• Journal of the Korean Ceramic Society
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• v.32 no.1
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• pp.83-89
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• 1995

YBa2Cu3O7-$\delta$, Y2BaCuO5, and binary compounds in the Ba-Cu-O system with the nominal composition of Ba2CuO3, BaCuO2, Ba3Cu4O7, Ba3Cu5O8 were synthesized to investigate the heat evolutions and crystalline phases in the hydration reaction of orthorhombic YBa2Cu3O7-$\delta$ phase. The observed crystalline phases were YBa2Cu3O7-$\delta$, Y2BaCuO5, and BaCuO2, or Ba2Cu3O5＋x, and some amount of noncrystalline phase in the Ba-Cu system comounds. In contact with distilled water, YBa2Cu3O7-$\delta$ and Y2BaCuO5 did not have considerable heat liberation, but in the binary compounds of the Ba-Cu-O system, the amount of total heat liberation was increased with respect to the Cu content. It might be that the reaction of high temperature superconductor YBa2Cu3O7-$\delta$ with water and/or moisture originated from the unusual oxidation state of Cu ion and the presence of amorphous Ba-Cu oxide compound. The degradation of high Tc superconductor by moisture and water could be controlled by restricting the heterogeneous distribution of Tc comlposition and the formation of second phase, such as stable Y2BaCuO5, and the resulting unstable Ba-Cu oxide compound.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.351-354
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• 1998

The formation of the $YBa_2Cu_30_{7_\delta}$(Y123) thick films has been investigated by a surface diffusion Imcess between $3BaCu0_2$+2CuO composite coating powder and a $Y_2BaCuO_5$(Y211). This reaction has been studied in the temperature of $930^{\circ}C$ and $940^{\circ}C$ for 2h to 10h in an oxygen atmosphere. The Y211 substrates becomes covered by co-precipitation of Y123 grains and CuO inclusions. X-ray diflractotnctn. revealed that the lager consisted of an orthorhombic crystal structure. The maximum Jc of $400A/\textrm{cm}^2$ is abtained when the specimen was heat-treated at $930^{\circ}C$ for 6h on the Y211 substrate.

• Bulletin of the Korean Chemical Society
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• v.10 no.1
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• pp.5-8
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• 1989

Conventional ceramic method has been used to prepare the green phase, $Y_2BaCuO_5$, commonly observed in 90-K superconductor $YBa_2Cu_3O_P{7-{\delta}}$as an impurity phase. The powder X-ray diffraction analysis indicates that $Y_2BaCuO_5$ has an orthorhombic symmetry with lattice parameter of a = 12.2 $\AA$, b = 5.61 $\AA$, and c = 7.14 $\AA.$ The average g-value 2.13 observed in ESR spectrum is attributable to Cu2+ stabilized in $C_{4v}$ field. From the magnetic susceptibility ($\mu$eff = 2.29 BM) and the ESR measurements, it is confirmed that Cu(II) $3d^9$ electrons in $Y_2BaCuO_5$ are localized and can be characterized by Curie-Weiss behavior. Optical reflectance spectrum shows a broad absorption peak around 680 nm due to dxy ${\rightarrow}$ $dx^2-y^2$ eletronic transition.

• Electrical & Electronic Materials
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• v.5 no.3
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• pp.278-283
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• 1992

123 초전도체에 마그네틱 모멘트가 큰 Ni불순물을 도핑하여 제작한 $Y_{1}$ Ba(C $u_{2.9}$ $N_{0.1}$) $O_{7-{\delta}}$ 초전도체의 X-ray diffraction pattern, susceptibility, 온도변화등에 따른 전류-전압관계, 임계온도 등에 대하여 연구하였다. 제작된 시료는 매우 뚜렷한 orthorhombic 피크를 가진 123상을 나타내고 있었다. N=0.1의 시료에서는 적은 양의 Ni 불순물과 단면적인 무정형상태의 잘 반응된 YBa(Cu, Ni)$_{3}$ $O_{7-{\delta}}$의 orthorhombic구조를 나타내고 있다. 전반적인 실험 결과로 부터 Ni는 Y-Ba-Cu-O 초전도 시스템에서 초전도에 중요한 역할을 담당하지 않는다는 결론을 얻었다.얻었다.다.

• Progress in Superconductivity and Cryogenics
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• v.1 no.1
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• pp.1-6
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• 1999

The microstructures of top seed mult processde $\textrm{YBa}_2\textrm{Cu}_3\textrm{O}_7$.$\delta$ single crystal were studied. Although shape of the seed was not faceted. the growth shape of Y123 single crystal was faceted. It was observed that Y211 phases were trapped in specific spaces of the faceted region. From the microstructural investigation. it was suggested that the segregation of Y211 is due to the difference of growth rates in crystal direction. When a single crystal was grown by the single seed with stepped multi surfaces. a microstrue was grown from multi-seed. The microstructure show the possibility of multi-seed growth. Corn kernel like structure without Y211 phase was observed and seemed to be formed by the diffusion reaction between Y211 phase in crystal and liquid wetted on the crystal. the diagonal line on Y123 crystal was observed that it was formed by the corn kernel like structure.

• Progress in Superconductivity
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• v.2 no.2
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• pp.92-96
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• 2001

We have fabricated a modified hairpin-type YBa$_2$Cu$_3$O$_{7-{\delta}}$ (YBCO) 2-pole microstrip bandpass filter with the center frequency of 5.8 GHz. We designed a hairpin-type filter with interdigital-coupled inner poles to improve the filter performance. Compared to a typical hairpin-type filter of the same size, the center frequency, the bandwidth and the insertion loss appeared smaller by 14.5% ,29.6%, and 0.55 dB, respectively. The dimensions of the filter were 13.7mm ${\times}$3.3 mm. YBCO films deposited on r-cut sapphire buffered with a CeO$_2$thin layer were used fur making the filter.

• 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.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.782-785
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• 1995

In this paper, $Mn^{2+}$ ion was doped in Y-Ba-Cu-O as an EPR probe. The following samples were prepared by conventional solid-state reaction method : $YBa_{2}Cu_{2.96}Mn_{0.04}O_{7-\delta}$ (MN-I), annealed $YBa_{2}Cu_{2.96}Mn_{0.04}O_{7-\delta}$ (AMN) and $YBa_{2}Cu_{2.94}Mn_{0.06}O_{7-\delta}$ (MN-II). AMN sample was obtained from MN-I by annealing for 1 hr under the Ar gas atmosphere at $600^{\circ}C$. X-band (~9.05 GHz) EPR spectra were measured from 103 K to room temperature by employing a JES-RE3X spectroscopy with a $TE_{0.11}$ cylindrical cavity and 100 kHz modulation frequency. In MN-I we have observed only the $Cu^{2+}$ signal. The fact that no $Mn^{2+}$ signal was observed, in spite of $Mn^{2+}$ being a very sensitive EPR probe, indicates that most likely isolated $Mn^{2+}$ ions don't exist in the MN-I sample. Most probably $Mn^{2+}$ ions in the MN-I sample interact antiferromagnetically and hence are EPR silent. The AMN spectra of at room temperature and 103 K indicate not only the $Cu^{2+}$ signal but also an extra signal, which increases with decreasing temperature. It is suggested that the extra signal originates from Mn ions that were antiferromagnetically coupled before the annealing process. In MN-II, from 103 K to room temperature, also, the extra signal was observed together with the $Cu^{2+}$ signal. The extra signal in MN-II, however, decreases with decreasing temperature and nearly disappears at 103 K. The signal originates from Mn ions in impurity phases that include $Mn^{2+}$ ions. We suppose that there exist at least two $Mn^{2+}$ doped phases in Y-Ba-Cu-O. The $Mn^{2+}$ signal of one phase is undectable at all temperature and that of another phase decreases with decreasing temperature and disappears around 103 K.

• Progress in Superconductivity and Cryogenics
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• v.13 no.4
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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.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.873-875
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• 1999

We have fabricated good quality superconducting $YBa_{2}Cu_{3}O_{7-\delta}$ thin films on Hastelloy(Ni-Cr-Mo alloys) metallic substrate with $CeO_2$ and $BaTiO_3$ buffer layers in-situ by pulsed laser deposition in a multi-target processing chamber. We have chosen $CeO_2$ as a buffer layer which has cubic structure of $5.41{\AA}$ lattice parameter and only 0.2% of lattice mismatch with YBCO. $CeO_2$ layer may be helpful for power transmission due to its conducting property. In order to enhance the crystallization of YBCO films on metallic substrates. we deposited $CeO_2$ and $BaTiO_3$ buffer layers at various temperatures. The YBCO superconducting tape fabricated with $BaTiO_3$ and $CeO_2$ buffer layers shows 85K of transition temperature and about $8.4{\times}10^4A/cm^2$ of critical current density at 77K.