• 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.

• 한국정보통신학회논문지
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• 제11권6호
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• pp.1115-1121
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• 2007

이온 빔 스퍼터법을 이용하여 저속성장으로 동시 증착에 의해 $Bi_2Sr_2Ca{_{n-1}}Cu_nO_x$(n=0,1,2) 박막을 제작하였다. Bi 2212 상은 기판온도 $750{\sim}795^{\circ}C$의 범위에서 나타났으며, $750^{\circ}C$보다 저온 측에서는 Bi 2201의 단일상이 존재하였다. 그러나, 조성과 관계되는 $PO_3$은 압력 변화에 대해서는 관찰되지 않았다. 그리고 $45{\sim}90K$의 임계온도(Tc)를 갖는 c축 배향한 고품질의 Bi 2212 박막을 얻었다. 소수의 박막에서는 소량의 CuO가 불순물로 관찰되었으며, 얻어진 모든 박막에서 $CaCuO_2$ 의 불순물 상은 관찰되지 않았다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2007년도 춘계종합학술대회
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• pp.524-527
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• 2007

이온 빔 스퍼터법을 이용하여 저속성장으로 동시 증착에 의해 $Bi_2Sr_2Ca_{n-1}Cu_nO_x$(n=0, 1, 2) 박막을 제작하였다. Bi 2212 상은 기판온도 $750\sim795^{\circ}C$의 범위에서 나타났으며, $750^{\circ}C$보다 저온 측에서는 Bi 2201의 단일강이 존재하였나. 그러나, 조성과 관계되는 $PO_3$에 대해서 크게 변하지 않았다. 그리고 임계온도(Tc)가 $45\sim90K$ 가지는 c축 배향한 고품질의 Bi 2212 박막을 얻었다. 소수의 박막에서는 소량의 CuO가 불순물로 관찰되었으며, 얻어진 모든 박막에서 $CaCuO_2$의 불순물 상은 관찰되지 않았다.

• 한국재료학회지
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• 제6권7호
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• pp.684-691
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• 1996

Bi-계 고온초전도체인 Bi2Sr2Ca2Cu3O10(Bi-2223)단일상을 반응시간을 줄이면서 합성하기 위하여 Bi-Sr-Ca-Cu-O계 내에 존재하는 Bi2Sr2Ca2Cu3O10(Bi-22o1), Bi2Sr2Ca2Cu3O10(Bi-2212), (Ca0.91Sr0.09)-CuO2의 혼합물, 특히 정확한 Bi1.7Pb0.4Sr2Ca2Cu3O10+x의 조성대신 (Ca0.91Sr0.09)CuO2가 많이 첨가된 조성의 혼합물에서 Bi-2223가 가장 쉽게 형성되었다. Bi-2223상은 86$0^{\circ}C$와 87$0^{\circ}C$에서 60시간 이내에 형성되었다. 소량의 Bi-2212상은 장시간의 반응후에도 여전히 존재하였다. 중간화합물을 이용한 합성방법이 통상의 소결방법에 비해 반응시간내에 소량의 불순물상들을 가진 Bi-2223상을 형성시킬 수 있다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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• pp.1208-1211
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• 2003

High quality $Bi_2Sr_2Ca_nCu_{n+1}O_x$ superconducting thin films fabricated by using the evaporation method at various substrate temperatures, $T_{sub}$, and ozone gas pressures, $pO_3$. The correlation diagrams of the $Bi_2Sr_2Ca_nCu_{n+1}O_x$ phases with $T_{sub}$ and $pO_3$ are established in the 2212 and 2223 compositional films. In spite of 2212 compositional sputtering, Bi2201 and Bi2223 as well as Bi2212 phases come out as stable phases depending on $T_{sub}$ and $pO_3$. From these results, the thermodynamic evaluation of ${\Delta}H$ and ${\Delta}S$, which are related with Gibbs' free energy change for single Bi2212 or Bi2223 phase, was performed.

• 한국세라믹학회지
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• 제38권4호
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• pp.360-364
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• 2001

고상반응법(solid-state reaction)으로 산화물 초전도체 Bi$_{2+x}$ Sr$_{1.8}$ $CaCu_2$$O_{8+\delta}$(-0.2$\leq$x$\leq$0.2)을 제조하여 조성변화에 따른 산소량과 Bi 이온의 하전가(valence)가 구조변조의 주기에 미치는 영향을 조사하였다. 2212상의 단일상 고용한계는 -0.1$\leq$x$\leq$0.1 영역이었다. 이 영역에서 x의 증가에 따라 격자상수 c는 감소를 보이며, 온셋 임계온도 Tc$^{on}$ 과 산소량은 증가하는 경향을 보였다. 또한, Bi 이온의 하전기와 구조변조의 주기는 단일상 고용한계 영역 내에서 x의 증가에 따라 감소하는 경향을 보이고 있다. 구조변조의 주기는 산소량이 증가함에 따라 감소하고 Bi 이온의 하전가 증가에 따라 증가함을 보였다. 즉, 산소의 절대량과 Bi 이온의 하전가에 따라 구조변조의 주기가 변화하는 것을 알 수 있었다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 추계학술발표대회 개요집
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• pp.262-264
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• 2005

$Bi_{2}Sr_{2}CaCu_{2}O_{x}$(Bi-2212) and $Bi_{2}Sr_{2}Ca_{2}Cu_{3}O_{y}$(Bi-2223) high-$T_{c}$ superconductor(HTS) coating have been prepared by plasma spraying and heaat treatment. The Bi-2212 HTS coating later is synthesized through the peritectic reaction between Sr-Ca-Cu oxide coating layer and Bi-Cu oxide coating later, and $Bi_{2}Sr_{2}CaCu_{2}O_{y}$(Bi-2212) superconducting phase grow by partial melting process. The superconducting characteristic depends strongly on the conditions of the partial melting process. the Bi-2212 HTS layer consists of the whiskers grown in the diffusion direction. Above the 2212 layer, Bi-2223 phase and secondary phase was observed. The secondary phase is distributed uniformly over the whole surface. This is caused to the microcrack on the coatings surface. Despite everything, the film shows superconducting with an onset $T_{c}$ of about 115K. There are two changes steps. One changes (1step) at 115K is due to the diamagnetism of the Bi-2223 phase and the other changes (2step) at 78K is due to the diamagnetism of the Bi-2212 phase.

• 한국세라믹학회지
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• 제37권8호
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• pp.787-791
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• 2000

Samples with the nominal composition, Bi2-xGexSr2CaCu2O8＋$\delta$ (x=0, 0.1, 0.2, 0.3, 0.4, 0.5) were prepared by the solid-state reaction method. We have studied the effect of substitution Ge for Bi and investigated the superconducting properties by changing oxygen content with Ge substitution. It was found that temperature difference, ΔK, between TCon and TCzero was considerably smaller in the samples prepared by the intermediate pressing method than that in the samples by the solid-state reaction method. We found the solubility limit of Ge to the 80 K single phase was around x=0.3. Within the solubility limit, lattice constant c decreased with the increase of x. In the region of the 80K single phase, the onset critical temperature TCon increased and excess oxygen content decreased with increase of x.

• Progress in Superconductivity
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• 제9권1호
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• pp.18-22
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• 2007

For interlayer tunneling spectroscopy using a small stack of $Bi_2Sr_2CaCu_2O_{8+x}$ (Bi-2212) intrinsic junctions in a high-bias range, large self-heating takes place due to the poor thermal conductivity of Bi-2212. In this study, we numerically estimate the self-heating around a Bi-2212 sample stack for I-V or dI/dV-V measurements. Our results show that the temperature discrepancy between the Bi-2212 sample stack and top Au electrodes due to bias-induced self-heating is small enough along the c-axis direction of Bi-2212. On the other hand, the lateral temperature discrepancy between the sample stack and the Bi-2212 on-chip thermometer stack can be as large as ${\sim}20\;K$ for the highest bias required to observe the pseudogap hump structure. We thus suggest a new in-situ ac thermometry, employing the Au current-bias electrode itself deposited on top of the sample stack as the resistive thermometer layer, which is supposed to allow safe temperature measurements for the interlayer tunneling spectroscopy.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2007년 추계학술발표대회 개요집
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• pp.282-284
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• 2007

The superconductor characteristics of BSCCO spray films by Heat treatment was studied. $Bi_2Sr_2CaCu_2O_x$(Bi-2212) is high-Tc superconductor(HTS) coatings have been prepared by Heat treatment. Where high current carrying capabilities are required and therefore thick film and bulk material are called for, the Bi2Sr2Ca1Cu2O8-d(Bi-2212)compound has evoleved as one of the most promising. and the Bi-2212 HTS coating layer is synthesized through the peritectic reaction between Sr-Ca-Cu oxide coating layer and Bi-Cu oxide coating layer by partial melting process. The superconducting characteristics depends on the spray distance which was related to the spray particle melt. The Bi-2212 HTS layer consists of the whisker growth and secondary phase in 2212 layer were observed.