• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 초전도 자성체 연구회
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• pp.80-83
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• 2003

$SrSO_4$ were systematically added on Bi2212 from 0 to 10wt% to study the effect of Bi2212 superconductor tube characteristics. After mixing, the melted solution of Bi2212 and $SrSO_4$ was initially poured into the cylinder type of steel mold preheated at $550^{\circ}C$ for 30min and rotated at 1000rpm. Following that, tube was annealed at $840^{\circ}C$ for 72hrs. The tube dimension was 60 in diameter, 60mm in length and 2mm in thickness. XRD data suggests that there was no typical segregation phase related with $SrSO_4$. Well textured grain with typical 2212 phase was observed and average size was $20{\mu}m$. The measured critical current and critical current density of Bi2212 tube added by 5% $SrSO_4$ at 77K were 495A and $202A/cm^2$ respectively.

• 한국재료학회지
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• 제1권2호
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• pp.71-76
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• 1991

The superconducting powders in $YBa_2Cu_3O_{7-x}$ and Bi-Pb-Sr-Ca-Cu-O system were easily prepared from water in oil type emulsion by loading each cation into the aqueous phase. In $YBa_2Cu_3O_{7-x}$ system, the superconducting orthorhombic phase was formed by calcining at $750^{\circ}C$ for 10h in $O_2$. The size of the superconducting phase powders was submicron. The density of the sintered specimen using this powders was about 95% of the theoretical density and the resistance sharply decreases at about 90K, In Bi-Pb-Sr-Ca-Cu-O system the low Tc phase($(Bi, Pb)_2Sr_2Ca_1Cu_2O_y$) was formed by calcining at $800^{\circ}C$ for 10h in a low oxygen partial pressure of 1/20 atm The shape of clacined powder is thin plate of which size is about $2\mu\textrm{m}$ and thickness is smaller than $\mu\textrm{m}$. It was observed that the high Tc phase ($(Bi, Pb)_2Sr_2Ca_2Cu_3O_y$) was formed by sintering at $850^{\circ}C$ for 30h in oxygen pressure of 1/20 atm without intermediary grinding. The above sintered sample exhibited superconductivity with a Tc(zero)=105K.

• 한국전기전자재료학회논문지
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• 제15권4호
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• pp.308-313
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• 2002

Samples with the norminal composition, $Bi_{2-x}Au_xSr_2CaCu_2O_{8+\delta}$ (x = 0, 0.05. 0.1, 0.15) were prepared by the solid-state reaction method. The superconducting properties, x-ray powder diffraction patterns, critical temperature and microstructure of surface were measured the samples. x-ray patterns show the single phase(2212) nature of the samples. But, the peaks of 2201 at $2\theta=30^{\circ}$ and Au peak at $2\theta=38.31^{\circ}$ are observed in the Au additive samples. The grain sire are enlarged with the increase of x. As the result of enlargement the grain size, the onset and offset critical temperature($T_c^{on}$,$T_c^{zero}$) increased with increase of x.

• 한국세라믹학회지
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• 제35권10호
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• pp.1007-1013
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• 1998

The samples of Bi2Sr2Ca1-xNaxCu2O8+y with various carrier concentration were synthesized by substituting Na for Ca ion. The superconducting properties hall coefficients and X-ray powder diffraction were measur-ed the sampled. Single phase samples were obtained for 0$\leq$x<0.3 of Bi2Sr2Ca1-xNaxCu2O8+y In the single phase the critical temperature. {{{{ { T}_{c } }} and carrier concentration increase with the increase of Na concentration pass through a maximum and then decreases. In the range of x$\geq$0.7 to the Na doped samples however we observed the metal-semiconductor transition. The c-axis seemed to decrease and a and b-axes increase with increasing Na concentration in the single phase. Decreasing of c-axis while increasing x is due to the smaller size of {{{{ {Na}^{+1 } }} ions to the {{{{ { Ca}^{+2 } }} ions. In the range of x>0.3 however the trend becomes ambiguous due to the inclusion of the 10K phase and impurity phase.

• 한국자기학회지
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• 제4권1호
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• pp.44-47
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• 1994

Laser ablation법으로 c-축 배향되도록 만든 Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7- .delta. / 박막으로 임계온도 근처에서 운반자들의 정보를 얻기위하여 Hall 효과를 연구하였다. 자기비저항은 Nernst 효과 때문에 자기장이 증가할 수록 offset 점의 온도가 낮았고, 자기비저항으로 부터 열자기적 효과를 고 려하여 계산한 Hall 비저항값과 실제 van der Pauw 법으로 측정한 Hall 비저항값을 비교해 본 결과 비교적 잘 일치하였다.

• Progress in Superconductivity
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• 제11권2호
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• pp.123-127
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• 2010

The properties of buffer layer for thermal and chemical stability in coated conductor is a very important issue. $CeO_2$ has desirable thermal and chemical stability as well as good lattice match. In this study, $CeO_2$ was deposited by electron beam deposition. The MgO(001) single crystal and LMO buffered IBAD substrate(LMO/IBAD-MgO/$Y_2O_3/Al_2O_3$/Hastelloy) were used as substrates, which have $\Delta\phi$ values of ${\sim}8.9^{\circ}$. The epitaxial $CeO_2$ films was deposited with high deposition rate of $12{\sim}16\;{\AA}/sec$. During deposition, the change of oxygen partial pressure(${\rho}O_2$) does not cause change in c-axis texture. In case of $CeO_2$ on MgO single crystal, the substrate temperature was optimized at $750^{\circ}C$ with superior $\Delta\phi$ and $\Delta\omega$ value. Otherwise, In case of LMO buffered IBAD substrate, It was optimized at $650^{\circ}C$ with increasing its deposition thickness of $CeO_2$, which was finally obtained with best $\Delta\phi$ value of $5.5^{\circ}$, $\Delta\omega$ value of $2^{\circ}$ and Ra value of 2.2 nm.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권4호
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• pp.221-225
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• 1999

This paper shows the parameters to affect the critical characteristic of YBaCuO superconducting bulk fabricated by MPMG (Melt Powdered Melt Growth)process. In order to investigate proper processing variables, the effect of the holding time at the melting temperature and that of the slow cooling time in $O_2\; ambient\; on\; the\; J_c$ were experimented. And then with the above obtained heat treatment conditions, the effects of addition of $Y_2BaCuO_5\; and\; Ag\; on\; the\; J_c$ were also investigated. A proper slow cooling time yields phase transformation from Tetragonal $(YBa_2Cu_3O_6)$ to Orthorhombic $(YBa_2Cu_3O_7)$ during an annealing time in $O_2$. Ag addition plays a role in increasing the $T_c\; and\; the J_c$, but the magnetization decreases. The $J_c$ and the magnetization increase with addition of Y211. $J_c$ of the sample added Ag 10wt% is superiorover 3000 G. Proper holding time, slow cooling time and amount of impurity addition are important parameters in fabricating the YBaCuO bulk by MPMG process with high $J_c$.

• Progress in Superconductivity
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• 제9권2호
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• pp.146-151
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• 2008

Measurements of surface resistance ($R_s$) of high temperature superconductor (HTS) films with accuracy are essential for microwave applications of HTS materials. In using the dielectric resonator method, uncertainties in the unloaded quality factor of the resonator cause significant errors in the measured $R_s$ of HTS films. We compare the Rs values of $YBa_2Cu_3O_{7-{\delta}}$ films calculated from the $Q_0$ as determined from the Lorentzian fit with that from the $Q_0$ as determined from the S-parameter circle-fit at temperatures between 15 K and 77 K. The two sets of values appeared to differ by 5%, 7%, 6%, and 11% at temperatures of 15, 60, 70, and 77 K, respectively, from each other, implying that careful error analysis needs to be performed in obtaining the $R_s$ of HTS films by using the Lorentzian-fit method, with the ones determined from the S-parameter circle-fit used as the reference.

• 공업화학
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• 제7권4호
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• pp.639-644
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• 1996

원료물질인 $Y_2O_3$, $BaCO_3$, CuO 및 $AgNO_3$ 분말로부터 Y계 고온초전도체를 발화합성법으로 제조하였다 $YBa_2Cu_3O_{7-x}$와 Cu를 Ag로 부분 치환한 $YBa_2Cu_{3-y}Ag_yO_{7-x}$의 특성을 X-ray diffractometer, resistivity measuring equipment, SEM, and Vickers Hardness 등으로 분석하였다. $YBa_2Cu_3O_{7-x}$의 Tc,zero는 91K였고, 밀도는 $5.2g/cm^3$, 경도는 $590kg/mm^2$였다. Cu를 Ag로 0.15몰 이하 부분 치환한 $YBa_2Cu_{3-y}Ag_yO_{7-x}$의 경우 임계온도(Tc)는 거의 변하지 않으면서 미세구조, 밀도 및 경도가 향상되었다.

• 한국결정학회지
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• 제7권2호
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• pp.147-155
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• 1996

할로겐 램프를 열원으로 이용하는 결정성장장치인 부유대역융로를 제작하여 고온초전도체 Bi2Sr2CaCu2O8의 성장에 이용하였다. 제작된 결정성장장치는 할로겐 램프를 초점에 위치시키기 위한 holder unit, 1kW의 할로겐 램프로서 최대 1800℃까지 사용이 가능한 image furnace, 냉각장치, 원료 물질을 공급하는 feeding unit, 성장된 단결정을 인상하는 pulling unit, 그리고 2mm/hr - 40mm/hr의 속도로 상하 이동 및 15rpm -120rpm의 회전이 가능한 제어부 등으로 구성되었다. 300W의 할로겐 램프를 이용하여 Bi2Sr2CaCu2O8 fiber를 성장시켰으며 성장된 fiber는 XRD, SEM, EDS 등으로 분석하였다. 성장조건은 공기분위기에서 성장속도 3∼4mm/hr, 상·하부축 회전속도 20∼25 rpm이었으며 성장된 fiber는 Bi2Sr2CaCu2O8 기지 내에 (Sr,Ca)CuO2 및 (Sr,Ca)2CuO3의 2차상을 포함하고 있었다.