• 한국자기학회지
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• 제8권4호
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• pp.203-209
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• 1998

Single phase garmet Y3-xBixFe5O12(x=0.0, 0.25, 0.5, 0.75, 1.0)을 ethylene glycol을 용매로 하여 sol-gel 법으로 합성후 x-ray diffraction, Mossbauer 분광기, vibrating sample magnetometer (VSM)를 이용하여 결정학적 및 자기적 특성을 연구하였다. Y과 Fe의 수화 반응을 통하여 얻은 Y3Fe5O12의 x-ray 회절 분석 결과는 결정구조가 cubic임을 알 수 있었고 Y에 Bi를 치환한 경우 또한 cubic 구조이었으며 Bi의 치환 량이 증가할수록 격자 상수가 선형적으로 증가함을 알수 있었다. Bi를 첨가한 Y3-xBixFe5O12 (x=0.0, 0.25, 0.5, 0.75, 1.0)의 단일상의 garnet이 형성되기 시작하는 온도는 80$0^{\circ}C$이고 secound phase (BiFeO3)가 생성되기 시작하는 온도는 x=0.75는 100$0^{\circ}C$이며 x-1.0은 95$0^{\circ}C$였다. Mossbauer 분광 실험과 VSM측정 결과 Birk 치환 될수록 포화 자화 값과 coercivity값이 감소하는 경향을 보였으며 Curic 온도는 Bi의 치환 양이 증가할수록 약간 증가하는 경향을 보임을 알 수 있었다.

• 마이크로전자및패키징학회지
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• 제10권4호
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• pp.47-52
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• 2003

PDP전극용 Ag전극 페이스트의 프릿으로 기존의 Pb-based 프릿을 대신 할 수 있는 Bi-based 조성의 새로운 유리조성의 가능성을 검토하였다. PDP디스플레이 응용을 위해 프릿의 저융점화 및 열팽창계수 제어를 행하였고, 이를 전극 페이스트 제조에 적용하여 스크린 프린팅된 전극을 평가하였다. $Bi_2O_3$를 50-60wt%이상 첨가된 $Bi_2O_3-B_2O_3-Al_2O_3$계 조성의 프릿은 연화점이 400∼$480^{\circ}C$, 열팽창계수가 7.31∼$10.02\times 10^{-6}/^{\circ}C$이며, 전극의 단자저항은 4.1∼4.8$\Omega$ 이었다. 본 연구에서 새로이 개발된 Bi계 프릿조성은 Pb계 조성의 프릿에 상당하는 물성을 얻을 수 있었으며, 이를 전극용 페이스트에 적용한 결과, 전극 프린팅에서 퍼짐성과 균일성이 우수하였다. PDP전극용 무연, 무 알카리 프릿으로 Bi계 조성의 적용가능성을 확인할 수 있었다.

• 한국세라믹학회지
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• 제36권12호
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• pp.1369-1373
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• 1999

• 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.

• 한국전기전자재료학회논문지
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• 제21권8호
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• pp.738-748
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• 2008

In this study, it has been investigated on the changing behavior of electrical properties in $ZnO-Bi_2O_3-Sb_2O_3$ (Sb/Bi=2.0, 1.0 and 0.5) ceramics. The samples were prepared by conventional ceramic process, and then characterized by I-V, C-V curve plots, impedance and modulus spectroscopy (IS & MS) measurement. The electrical properties of ZBS systems were strongly dependent on Sb/Bi. In ZBS systems, the varistor characteristics were deteriorated noticeably with increasing Sb/Bi and the donor density and interface state density were increased with increasing Sb/Bi. On the other hand, we observed that the grain boundary reacted actively with the ambient oxygen according to Sb/Bi ratio. Especially the grain boundaries of Sb/Bi=0.5 systems were divided into two types, i.e. sensitive to oxygen and thus electrically active one and electrically inactive intergranular one with temperature. Besides, the increased pyrochlore and $\beta$-spinel phase with Sb/Bi ratio caused the distributional inhomogeneity in the grain boundary barrier height and the temperature instability. To the contrary, the grain boundary layer was relatively homogeneous and more stable to temperature change and kept the system highly nonlinear at high Bi-rich phase contents.

• 한국표면공학회지
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• 제48권6호
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• pp.303-308
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• 2015

Pd-functionalized ${\beta}-Bi_2O_3$ nanowires are synthesized by thermal evaporation of Bi powder using VLS mechanism followed by Pd coating and annealing. In this study, sensing properties of Pd-functionalized ${\beta}-Bi_2O_3$ nanowires sensor to selected concentrations of $NO_2$ gas were examined. Scanning electron microscopy showed that the nanowires with diameters in a range of 100 - 200 nm and lengths of up to a few tens of micrometers. Transmission electron microscopy and X-ray diffraction confirmed that the products corresponded to the nanowires of ${\beta}-Bi_2O_3$ crystals and Pd nanoparticles. Pd-functionalized ${\beta}-Bi_2O_3$ nanowires sensor showed an enhanced sensing performance to $NO_2$ gas compared to as-synthesized ${\beta}-Bi_2O_3$ nanowires sensor. As synthesized and Pd-functionalized ${\beta}-Bi_2O_3$ nanowire sensors showed responses of 178% - 338% and 196% - 535% at $300^{\circ}C$, respectively, to 0.05 - 2 ppm $NO_2$. In addition, the underlying mechanism of the enhancement of the sensing properties of ${\beta}-Bi_2O_3$ nanowires by Pd-functionalization is discussed.

• The Korean Journal of Ceramics
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• 제5권2호
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• pp.183-188
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• 1999

The crystallization behavior and electrical conductivity of the $CuO-Bi_2O_3-V_2O_5$ glasses with various CuO content were investigated. The glass formation regin was 0~20 mol% Bi2O3, 5~55 mol% CuO, and 30~90 mol% $V_2O_5$ with Tg=$275^{\circ}C$~$290^{\circ}C$. Among glasses with various compositions, the 31CuO-$14Bi_2O_3-55V_2O_5$ (mol%) glass heat-treated at $358^{\circ}C$ for 8 h showed the highest conductivity of ~ at room temperature. The heat-treated glasses increased in electrical conductivity by the order of 104 compared to non heat-treated glass. The linear relationship between 1n($\sigma$T)and $T^{-1}$ indicated that electrical conduction in the 31CuO-$14Bi_2O_3-55V_2O_5$ (mol%) glass occurred by a small polaron hopping.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2002년도 춘계 학술발표강연 및 논문개요집
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• pp.129-129
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• 2002

• Journal of Electrochemical Science and Technology
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• 제10권4호
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• pp.424-432
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• 2019

Planar BiVO₄ and 3 wt% Mo-doped BiVO₄ (abbreviated as Mo:BiVO₄) film were prepared by the facile spin-coating method on fluorine doped SnO₂(FTO) substrate in the same precursor solution including the Mo precursor in Mo:BiVO₄ film. After annealing at a high temperature of 450℃ for 30 min to improve crystallinity, the films exhibited the monoclinic crystalline phase and nanoporous architecture. Both films showed no remarkably discrepancy in crystalline or morphological properties. To investigate the effect of surface passivation exploring the Al₂O₃ layer, the ultra-thin Al₂O₃ layer with a thickness of approximately 2 nm was deposited on BiVO₄ film using the atomic layer deposition (ALD) method. No distinct morphological modification was observed for all prepared BiVO₄ and Mo:BiVO₄ films. Only slightly reduced nanopores were observed. Although both samples showed some reduction of light absorption in the visible wavelength after coating of Al₂O₃ layer, the Al₂O₃ coated BiVO₄ (Al₂O₃/BiVO₄) film exhibited enhanced photoelectrochemical performance in 0.5 M Na₂SO₄ solution (pH 6.5), having higher photocurrent density (0.91 mA/㎠ at 1.23 V vs. reversible hydrogen electrode (RHE), briefly abbreviated as V_RHE) than BiVO₄ film (0.12 mA/㎠ at 1.23 V_RHE). Moreover, Al₂O₃ coating on the Mo:BiVO₄ film exhibited more enhanced photocurrent density (1.5 mA/㎠ at 1.23 V_RHE) than the Mo:BiVO₄ film (0.86 mA/㎠ at 1.23 V_RHE). To examine the reasons, capacitance measurement and Mott-Schottky analysis were conducted, revealing that the significant degradation of capacitance value was observed in both BiVO₄ film and Al₂O₃/Mo:BiVO₄ film, probably due to degraded capacitance by surface passivation. Furthermore, the flat-band potential (V_FB) was negatively shifted to about 200 mV while the electronic conductivities were enhanced by Al₂O₃ coating in both samples, contributing to the advancement of PEC performance by ultra-thin Al₂O₃ layer.

• 한국재료학회지
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• 제22권12호
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• pp.689-695
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• 2012

We have examined the co-doping effects of 1/2 mol% NiO and 1/4 mol% $Cr_2O_3$ (Ni:Cr = 1:1) on the reaction, microstructure, and electrical properties, such as the bulk defects and the grain boundary properties, of ZnO-$Bi_2O_3-Sb_2O_3$ (ZBS; Sb/Bi = 0.5, 1.0, and 2.0) varistors. The sintering and electrical properties of Ni,Cr-doped ZBS, ZBS(NiCr) varistors were controlled using the Sb/Bi ratio. Pyrochlore ($Zn_2Bi_3Sb_3O_{14}$), ${\alpha}$-spinel ($Zn_7Sb_2O_{12}$), and ${\delta}-Bi_2O_3$ were detected for all of compositions. For the sample with Sb/Bi = 1.0, the Pyrochlore was decomposed and promoted densification at lower temperature by Ni rather than by Cr. A homogeneous microstructure was obtained for all of the samples affected by ${\alpha}$-spinel. The varistor characteristics were not dramatically improved (non-linear coefficient, ${\alpha}$ = 5~24), and seemed to form ${Zn_i}^{{\cdot}{\cdot}}$(0.17 eV) and ${V_o}^{\cdot}$(0.33 eV) as dominant defects. From impedance and modulus spectroscopy, the grain boundaries were found to have been divided into two types, i.e., one is tentatively assigned to ZnO/$Bi_2O_3$ (Ni,Cr)/ZnO (0.98 eV) and the other is assigned to a ZnO/ZnO (~1.5 eV) homojunction.