• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 1999년도 제1회 학술대회논문집(KIASC 1st conference 99)
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• pp.51-53
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• 1999

The crystallization mechanism of an amorphous $Bi_{2}$$Sr_{2}$$Ca_{2 x}$$Cd_{x}$$Cu_{3}$$O_{y}$ phase were studied from the relations between crystallization and volume changes by dilatometry. Further, the effect of addition of CdO on the crystallization mechanism and superconductivity was discussed. The shrinkage of the amorphous $Bi_{2}$$Sr_{2}$$Ca_{2 x}$$Cd_{x}$$Cu_{3}$$O_{y}$ occurred with the crystallization of $Bi_{2}$$Sr_{2}$Cu$O_{6}$ phase decrease with increasing CdO content with a minimum at x=0.4. Better superconductivity was obtained in the specimens formation less amount of the$Bi_{2}$$Sr_{2}$Cu$O_{6}$ phase during the crystallization process.

• Bulletin of the Korean Chemical Society
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• 제30권11호
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• pp.2559-2562
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• 2009

The lattice vibration and crystal structure of alkaline earth metal-substituted $RuSr_{1.9}A_{0.1}GdCu_{2}O_{8}$ (A = Ca, Sr, and Ba) have been investigated with micro-Raman spectroscopy. The present $RuSr_{1.9}A_{0.1}GdCu_{2}O_{8}$ materials show not only several weak Raman peaks corresponding to the vibrations of $O_{Cu}$ and $O_{Ru}$ but also strong characteristic phonon lines related to $O_{Sr}$ vibration mode. A comparison between the frequency of $O_{Sr}$ vibration and the bond distances of (Ru$O_{Sr}$) and (Cu‒$O_{Sr}$) in the present ruthenocuprates reveals that the vibration energy of $O_{Sr}$ is mainly dependent on the bond distance of (Ru‒$O_{Sr}$). The peak splitting of the $O_{Sr}$ phonon lines was observed for the unsubstituted $RuSr_{1.9}A_{0.1}GdCu_{2}O_{8}$, suggesting the existence of two different (Ru‒$O_{Sr}$) bond distances. Such a peak splitting caused by the appearance of low-energy shoulder reflects the presence of internal charge transfer pathway from the $RuO_2$ plane to the superconductive $CuO_2$ one. After the substitution of Sr with Ca or Ba, the low-energy shoulder peak of $O_{Sr}$ vibration becomes suppressed, underscoring the depression of internal charge transfer between the $RuO_2$ and $CuO_2$ planes. The weakened role of $RuO_2$ layer as charge reservoir in the $RuSr_{1.9}A_{0.1}GdCu_{2}O_{8}$8 (A = Ca, Ba) would be responsible for the depression of $T_c$ upon the Ca/Ba substitution.

• 한국결정학회지
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• 제7권1호
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• pp.20-29
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• 1996

(Sr1-xCax)CuO2 단결정을 융제법으로 제조하고 단결정 X-선 회절법을 이용하여 그 결정구조를 밝혔다. 이 화합물의 결정축계는 사방정계(orthorhombic system)이며, 공간군은 Cmcm(63), 그리고 격자상수 a, b, c는 각각 3.4645Å, 16.1417Å, 3.8727Å이었다. (Sr1-xCax)CuO2 화합물에서 Sr대신 치환되는 Ca이온의 한계를 구조적인 관점에서 연구하였다. 이를 위해 X-선 회절(CAD4), energy dispersive X-ray fluorescence (EDAX) and electron probe micro-analysis (EPMA) 등을 사용하였다. Ca가 치환됨에 따른 Cu-O 결합길이의 변화로부터 Ca의 치환한계를 결정하였는데 그 한계치는 Xca≒0.73이었다.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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• pp.300-304
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• 1999

To tap the feasibility of exploiting the 2$^{nd}$ phases as flux-pinning centers in the (Bi,Pb)$_2Sr_2Ca_2CuO_{10}$ superconductor, the size and the distribution of the precipitates have been controlled by changing reaction temperature and time, oxygen partial pressure Po$_2$ and annealing condition. Various annealing heat treatments were also conducted on the as-received 61 filament Bi-2223 tapes with Bi$_{1.8}Pb_{0.4}Sr_2Ca_{2.2}Cu_3O_8$ starting composition and annealed specimen were analyzed with XRD, SEM, EDS and TEM.. The grain size of (Ca,Sr)$_2$(BiPb)O$_4$ or Bi$_{0.5}Pb_3Sr_2Ca_2CuO_{\delta}$ was controllable by optimizing the heat treatment condition and critical current density (J$_c$) showed dependence on the size of the 2$^{nd}$ phases.

• 한국재료학회지
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• 제6권6호
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• pp.543-554
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• 1996

Bi-Sr-Ca-Cu-O 계에서 상형성에 관해 연구하였다. 임계온도가 80K인 초전도체는 Bi-Sr-Ca-Cu의 몰비율이 2:2:1:2의 성분으로부터 solid state synthesis의 방법으로 합성하였다. 이때 이상에 대한 x-ray diffraction pattern은 모두 색인하였다. 2:2:1를 기본으로한 solid solution의 형성을 Bi2Sr2-xCa1+yCu2O8+$\delta$으로 단일상(single phase)을 형성하고 있으며, 이때 x와 y의 범위는 0

• 한국결정성장학회지
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• 제9권3호
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• pp.299-302
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• 1999

$La_{2-x}Sr_{x}CuO_{4}$ single-crystalline films were prepared on bulk single crystals of Zn-doped $La_{2-x}Sr_{x}CuO_{4}$ as the substrates by LPE technique using two deferent methods. When prepared using an alumina crucible in normal electrical furnace, the $La_{2-x}Sr_{x}CuO_{4}$ films were contaminated with less than 3 at% aluminum from the alumina crucibles. Aluminum contamination either reduced or completely destroyed the superconductivity of the $La_{2-x}Sr_{x}CuO_{4}$ films, For LPE growth by modified TSFZ method using an infrared heating furnace without crucibles, the $La_{2-x}Sr_{x}CuO_{4}$ films of x=0.11 showed superconducting with $Tc_{onset}=36\;K$, which is 10 K higher than that in the $La_{2-x}Sr_{x}CuO_{4}$ bulk single crystals.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 1999년도 제1회 학술대회논문집(KIASC 1st conference 99)
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• pp.47-50
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• 1999

The orientation mechanism of an amorphous $Bi_{2}$$Sr_{2}$$Ca_{2 x}$$Cd_{x}$$Cu_{3}$$O_{y}$ phase were studied by using the dilatometry. The amorphous $Bi_{2}$$Sr_{2}$$Ca_{2 x}$$Cd_{x}$$Cu_{3}$$O_{y}$ samples brought about a volume shrinkage at the onset of the crystallization of a $Bi_{2}$$Sr_{2}$$CaCu_{2}$$O_{6}$phase around $400^{\circ}C$. The random crystal growth of $Bi_{2}$$Sr_{2}$$CaCu_{2}$$O_{8}$ phase around $800^{\circ}C$. yielded a rapid volume expansion and after then samples shrinmed, accompanied with the crystal orientation. The$Bi_{2}$$Sr_{2}$$Ca_{2 x}$$Cd_{x}$$Cu_{3}$$O_{y}$ (x=0.4) sample exhibited the best-oriented structure because the liquid phase formed seemed to have the lowest viscosity which would contributed to the easy collapse of the card-house structure.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.276-279
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• 2002

$Bi_{2}Sr_{2}CaCu_{2}O_{x}$ was prepared by the conventional method of solid state reaction and SHS method. The samples were annealed in different atmosphere in order to examine the influence of atmospheres on the carbon contents in the $Bi_{2}Sr_{2}CaCu_{2}O_{x}$ compound. The lowest carbon content in $Bi_{2}Sr_{2}CaCu_{2}O_{x}$ could be attended when the sample was annealed in $O_{2}$ at $800^{\circ}C$ for 100 hours. The $CO_{2}$ in air pollute the samples and increase the carbon content in the sintering process. The critical current density of the $Bi_{2}Sr_{2}CaCu_{2}O_{x}$ samples will decrease with the increasing carbon contents in the samples. The impurity carbon will deposit in the grain boundary, which makes critical current density lower.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.47-47
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• 2008

P-type transparent semiconductor $SrCu_2O_2$ thin films have been prepared by RF sputtering using low-alkali glass for LCD and quartz as substrates. Single phase of $SrCu_2O_2$ powder was obtained by heating a stoichiometric mixture of CuO and $SrCO_3$ at 1223K for 96h under N2 gas flow, and target was fabricated at 1243K for 24h. Room temperature conductivity of the sintered body was about 0.02S/cm, and the activation energy in the temperature range of $-50^{\circ}C$~RT and RT~$150^{\circ}C$ were 0.18eV, 0.07eV, respectively. Effects of deposition pressure and post-annealing temperature on the electrical and optical properties of the obtained thin film have been investigated.

• 한국전기전자재료학회논문지
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• 제16권4호
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• pp.343-350
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• 2003

Using Bi$_2$Sr$_2$Ca$_2$.$_2$Cu$_3$ $O_{x}$ powders prepared by solid state reaction and spray drying method, the nucleation and growth behaviors of superconducting and second phases were investigated during isothermal heat treatment. When the spray drying power was used in contrast with solid state reaction powder, Bi$_2$Sr$_2$Ca$_2$.$_2$Cu$_3$ $O_{x}$ (2223) phase could be formed at the relatively shot time and second phases were much bigger. Quantitative analysis showed that as the heat treatment time increased, more Bi$_2$Sr$_2$Ca$_2$.$_2$Cu$_3$ $O_{x}$ (2212) changed to 2223 and the major second phase was changed from (Sr,Ca)$_{14}$Cu$_{24}$ $O_{x}$(14:24) to (Sr,Ca)$_2$Cu$_1$ $O_{x}$ (2:l). The superconducting phase formed at the relatively short time 14:24 phase. Following the Bi-free phase of 14:24 Phase, but long time was needed in places far from the 14:24 phase. Following the formation of the 2212 phase near the 14:24 phase, the 2223 phase nucleated preferentially at the interface between the 2212 and 14:24 phases. The preferential nuclcation of 2223 was explained by its structural similarity and low Interfacial energy with both the Bi-free and 2212 Phases.12 Phases.