• E2M - 전기 전자와 첨단 소재
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• 제4권4호
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• pp.330-337
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• 1991

y의 크기가 0.02에서부터 2.0까지의 두 차수만큼 변하게 불소가 첨가된 YBa$_{2}$Cu$_{3}$$O_{7-x}$F$_{y}$ 초전도물질을 금속질산염과 수산화나트륨 및 불화나트륨을 써서 졸-겔법으로 제조하였다. 불소함유양들을 이온-선택 전극을 사용하여 측정하였다. 반응물질로 첨가된 불소전부가 최종시료속에 존재한다는 것을 알았다. XRD 관측으로부터 y.leq.0.2인 시료들은 단지 단상 페로브스카이트 구조로 되었고 반면 y.geq.0.5인 것들은 최종시료속에 BaF$_{2}$ YF$_{3}$및 CuO와 같은 화합물들과 함께 생성되어져 있다고 결론지을 수가 있다. 더구나 고체 $^{19}$ F 핵자기공명관측이 불소가 정말로 격자위치들 속에 혼입되어 있는지 여부를 확인하기 위하여 행해졌는데 실험결과로부터 YBa$_{2}$Cu$_{3}$$O_{7-x}$ 격자위치속에 혼입된 불소의 몰비는 화합물 1몰당 약 0.2라는 것을 보여주었다. 또한 전기저항률의 측정은 개시감계온도가 y.leq.0.2와 같이, 지정된 첨가율이 적은 영역에서는 y의 증가에 따라 약간씩 증가하는 경향이 있음을 보여주고 있다.

• Progress in Superconductivity
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• 제6권1호
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• pp.13-18
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• 2004

High-.ate in-situ$ YBa_2$Cu$Cu_3$$O_{7-x}$ (YBCO) film growth was demonstrated by means of the electron beam co-evaporation. Even though our oxygen pressure is low, ∼$5 ${\times}$10^{-5}$ Torr, we can synthesize as-grown superconducting YBCO films at a deposition rate of around 10 nm/s. Relatively high temperatures of around 90$0^{\circ}C$ was necessary in this process so far, and it suggests that this temperature at a given oxygen activity allows a Ba-Cu-O liquid formation along with an YBCO epitaxy. Local critical current density shows a clear correlation with local resistivity. Homogeneous transport properties with a large critical current density ($4 ∼ 5 MA/\textrm{cm}^2$ at 77K, 0T) are observed in top faulted region while it is found that the bottom part carries little supercurrent with a large local resistivity. Therefore, it is possible that thickness dependence of critical current density is closely related with a topological variation of good superconducting paths and/or grains in the film bodies. The information derived from it may be useful in the characterization and optimization of superconducting films for electrical power and other applications.

• E2M - 전기 전자와 첨단 소재
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• 제9권4호
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• pp.357-363
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• 1996

The superconducting properties of YBa$_{2}$Cu$_{3}$$O_{7-x}$(YBaCuO) thin films prepared by laser ablation have been investigated. The x-ray diffraction patterns of the films were substantially different from one another. The Y and Ba oxides are formed by the collisions with oxygen molecules. On the other hand, the Cu oxide is mainly formed at initial stage of the laser irradiation. The YBaCuO films manufactured on MgO(100) substrate were indicated T$_{c}$(zero)=90 K, T$_{c}$(onset)=92 K, and J$_{c}$=3.5*10$^{5}$ A/cm$^{2}$(at 77.3K). The optimum conditions were found to be a substrate temperature of 710.deg. C, an energy density of 2 J/cm$^{2}$, and a target-substrate distance of 60mm in an oxygen partial pressure of 200 mTorr.0 mTorr.

• 대한전자공학회논문지
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• 제27권5호
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• pp.724-728
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• 1990

The X-ray diffraction pattern, electrical resistance, density and critical temperature of a series of YBa2(Cu3-xNix)O7-\ulcornersamples (0\ulcorner\ulcorner.5) were investigated with the increase of the Ni content. The samples show a principal 1.2.3-like phase with well resolved orthorhombic peaks. The final pattern of the x=0.1 sample appears to be well reacted orthorhombic YBa2(Cu,Ni)3O7-\ulcornerwith minor impurities and an appreciable amorphous fraction. From the above results, we conclude that Ni does not play an important role for the superconductivity in the Y-Ba-Cu-O system.

• Journal of Magnetics
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• 제2권2호
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• pp.35-37
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• 1997

A sample of YBa2Cu3O7-x fluorinated by a high temperature (400$^{\circ}C$) gas exchange technique has been investigated by means of 19F NMR (nuclear magneti resonance) measurements in both superconducting and normal state. As a result, behaviors characteristic of the superconductor, including a peculiarity in the spin-lattice relaxation rate (1/T1) around 250 K, were observed.

• Bulletin of the Korean Chemical Society
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• 제10권1호
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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.

• 대한화학회지
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• 제34권6호
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• pp.555-560
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• 1990

$YBa_2Cu_3O_{7-x}$ 초전도 필름을 초음파에 의한 aerosol spray 법을 이용하여 YSZ (yttria stabilized zirconia) 및 SrTi$O_3$의 (100) 결정면 위에 만들었다. 초전도상은 세 단계의 과정을 거쳐서 형성되었다 : (가) 이트륨, 바륨, 구리의 질산염을 화학 양론비로 섞어 만든 용액을 250$^{\circ}C$로 가열된 기질에 분무하여, (나) 형성된 필름을 공기 중에서 550$^{\circ}C$로 예열하고, (다) 흐르는 산소 분위기에서 950$^{\circ}C$로 소결한 뒤 노냉하였다. 필름의 저하을 dc four-point probe 법으로 측정하여 액체질소 온도 이상에서 초전도성을 확인하였다.

• 한국초전도ㆍ저온공학회논문지
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• 제17권4호
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• pp.25-29
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• 2015

In 1987, M. K. Wu and Paul Chu discovered $Y_{1.2}Ba_{0.8}CuO_4$ (YBCO) with critical temperature ($T_c$) of 93 K. It has significantly lowered the cost of cooling of a material up to the point where superconductivity set in. Utilizing the cost reduction of attaining superconductivity and the vast amount of research to understand characteristics of high temperature oxide superconducting materials, there has been effort to use a high temperature superconductor as a coated conductor. It is important to characterize the materials precisely for stable performance before commercializing. We used polarized Raman scattering spectroscopy to study structural and stoichiometric information regarding $YBa_2Cu_3O_{7-x}$, $GdYBa_2Cu_3O_{7-x}$, and $GdBa_2Cu_3O_{7-x}$ produced by three leading groups of producing commercial grade high temperature superconductor coated conductors American Superconductor Corporation, Superpower, and SuNAM.

• Bulletin of the Korean Chemical Society
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• 제11권5호
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• pp.460-463
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• 1990

The normal and fluorinated high-Tc superconducting materials, $YBa_2Cu_3O_{7-x}F_y$with $0.25{\leq}x{\leq}0.55\;and\;0.00{\leq}y{\leq}0.30$, were synthesized to investigate the dopping effect of fluorine atom on the superconductivity of Y123 and studied by X-ray diffraction analysis and electron probe microanalysis, resistivity and thermopower measurements, and polarized micro-Raman spectroscopy. The reproducible micro-Raman spectra were recorded and analyzed. The coherent assignments could be suggested for the spectra of normal and fluorinated samples. The fluorine atoms introduced were found to be substituted for oxygen in pyramidal Cu-O units rather than in Cu-O chains. The unit cell parameters were decreased upon the substitution of oxygen by fluorine atom. From the decreasing cell parameters and Tc, the increasing thermopower, and the possible assignments of the vibrational modes, it could be suggested that the dopping of fluorine atom localizes the superconducting electrons in Y123.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2004년도 High Temperature Superconductivity Vol.XIV
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• pp.72-72
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• 2004