• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.200-201
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• 2007

The SBT($SrBi_2Ta_2O_9$) thin films with $Bi_2O_3$ buffer layer were deposited on Pt/Ti/$SiO_2$/Si substrate by R.F. magnetron sputtering method in order to improve the ferroelectric characteristics. In SBT thin films, the deficiency of bismuth during the process due to its volatility results in an obvious non stoichiometry of the films and the presence of secondary phases. $Bi_2O_3$ buffer layer was found to be effective to achieve the low temperature crystallization and improve the ferroelectric properties of SBT thin films. Ferroelectric properties and crystallinities of SBT thin films with various post annealing of $Bi_2O_3$ buffer layer were observed as various annealing temperature, using X-Ray Diffraction (XRD), scanning electron microscopy (SEM), Keithley 237 and HP 4192A Impedance Analyzer.

• 자원리싸이클링
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• 제21권5호
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• pp.50-57
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• 2012

황산동 용액중에 불순물로 존재하는 Sb, Bi 및 As를 제거하기 위해 Aminophosphosphonic acid를 관능기로 함유한 이온교환수지를 사용하여 비교 실험을 실시하였다. 이들 불순물 제거 반응에 영향을 미칠 수 있는 반응온도, 반응시간, 이온교환수지양 등에 대하여 고찰하였다. 기초 실험 결과 약 88%의 Sb 및 94%의 Bi가 이온교환수지에 흡착되어 황산동용액으로부터 제거가 가능하였다. 그러나 As의 경우는 제거율이 10% 이하로 미미하였다. 한편, Bi 와 Sb가 흡착된 수지에서 황산과 염산용액을 이용하여 선택적으로 세출이 가능하였다. 연속흡착실험 결과 Sb 와 Bi의 경우는 2BV 후에는 98.1%와 96.6%의 높은 흡착율을 보였다.

• 한국안광학회지
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• 제8권1호
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• pp.17-22
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• 2003

$PbO-Bi_2O_3-B_2O_3-SiO_2$ 유리계의 DTA 곡선과 FT-IR 스펙트럼을 조사하였다. 유리전이 온도의 조성비 의존성은 60 mol% $Bi_2O_3$에서 유리계의 구조가 변화하는 것으로 나타났다. 높은 비스무스 함량을 가지는 시료의 FT-IR 스펙트럼 조사에서 무거운 양이온 $Bi^{3+}$의 단위구조와 관계되는 결합이 우세했으며 그리고 고함량의 $Bi_2O_3$ 시료에서도 역시 붕소원자의 3배위와 4배위 진동이 있었다. PbO함량이 높은 유리계의 경우, 비가교 산소밴드의 낮은 강도는 PbO의 망목형성제 역할에 기인 한 것으로 생각된다. 유리의 흡수대는 결정화상태에서 강도가 매우 큰 변화를 보였다.

• 한국전기전자재료학회논문지
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• 제25권9호
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• pp.692-701
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• 2012

Recently, many lead-free piezoelectric materials have been investigated for the replacement of existing Pb-based piezoelectric ceramics because of globally increasing environmental interest. There has been remarkable improvement in piezoelectric properties of some lead-free ceramics such as $(Bi,Na)TiO_3-(Bi,K)TiO_3-BaTiO_3$, $(Na,K)NbO_3-LiSbO_3$, and so on. However, no one still has comparable piezoelectric properties to lead-based materials. Therefore, new lead-free piezoelectric ceramics are required. $BiFeO_3$ has a rhombohedrally distorted perovskite structure at room temperature and a very high Curie temperature ($T_C$= 1,100 K). And a very large electric polarization of 50 ~ 60 ${\mu}C/cm^2$ has been reported both in epitaxial thin film and single crystal $BiFeO_3$. Therefore, a high piezoelectric effect is expected also in a $BiFeO_3$ ceramics. The recent research activities on $BiFeO_3$ or $BiFeO_3$-based solid solutions are reviewed in this article.

• 한국분말재료학회지
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• 제22권4호
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• pp.254-259
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• 2015

$Bi_2Te_3$ related compounds show the best thermoelectric properties at room temperature. However, n-type $Bi_2Te_{2.7}Se_{0.3}$ showed no improvement on ZT values. To improve the thermolectric propterties of n-type $Bi_2Te_{2.7}Se_{0.3}$, this research has Cu-doped n-type powder. This study focused on effects of Cu-doping method on the thermoelectric properties of n-type materials, and evaluated the comparison between the Cu chemical and mechanical doping. The synthesized powder was manufactured by the spark plasma sintering(SPS). The thermoelectric properties of the sintered body were evaluated by measuring their Seebeck coefficient, electrical resistivity, thermal conductivity, and hall coefficient. An introduction of a small amount of Cu reduced the thermal conductivity and improved the electrical properties with Seebeck coefficient. The authors provided the optimal concentration of $Cu_{0.1}Bi_{1.99}Se_{0.3}Te_{2.7}$. A figure of merit (ZT) value of 1.22 was obtained for $Cu_{0.1}Bi_{1.9}Se_{0.3}Te_{2.7}$ at 373K by Cu chemical doping, which was obviously higher than those of $Cu_{0.1}Bi_{1.9}Se_{0.3}Te_{2.7}$ at 373K by Cu mechanical doping (ZT=0.56) and Cu-free $Bi_2Se_{0.3}Te_{2.7}$ (ZT=0.51).

• 한국재료학회지
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• 제27권3호
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• pp.144-148
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• 2017

The effects of an excess of Bi on the piezoelectric and dielectric properties of $0.60Bi_{1+x}FeO_3-0.40BaTiO_3$ (x = 0, 0.01, 0.03, 0.05, 0.07) were investigated. The ceramics were processed through a conventional solid state reaction method and then quenched after sintering at different temperatures in the range of $980{\sim}1070^{\circ}C$. A single perovskite structure without any secondary phase was confirmed for all compositions and temperatures. It was found that excess Bi reduced the sintering temperatures, acted as a sintering aid and enhanced the properties in combination with quenching. Curie temperature ($T_C$) was found to slightly increase due to the presence of excess Bi; electrical properties were also improved by quenching. At x = 0.03 and $1030^{\circ}C$, remnant polarization ($2P_r$) was as high as $45.4{\mu}C/cm^2$ and strain at 40 kV/cm was up to 0.176 %.

• 분석과학
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• 제11권1호
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• pp.42-46
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• 1998

고리화펜타디엔이 ${\pi}$-결합된 최초의 비스무트 화합물$({\eta}^5-C_5Me_5)_2BiCl$이 에데르 용매하에서 칼륨펜타메틸고리화펜타다이엔과 삼염화비스무트의 반응결과 짙은 보라색의 결정이 30%의 수율로 얻어졌다. 이 화합물의 분해 생성물로서 pentamethylcyclopentadienylbismuth chloride($PCpBiCl_2$)가 얻어졌으며 $({\eta}^5-C_5Me_5)_2BiCl$은 칼륨펜타메틸고리화펜타다이엔과 $-78^{\circ}C$에서 반응하지 않음을 확인하였다. $({\eta}^5-C_5Me_5)_2BiCl$의 구조가 192K에서 X선 단결정 구조분석 방법에 의해 밝혀졌다: triclinic crystal, space group p1, Z=2. $C_{20}H_{30}$의 이탈반응이 확인되었으며 고리화펜타다이엔의 두 고리가 C-C ${\sigma}$-단일 결합으로 이루어져 있다는 것이 X선 단결정 구조분석 방법에 의해 밝혀졌다.

• Korean Journal of Chemical Engineering
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• 제35권12호
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• pp.2442-2451
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• 2018

Novel highly active visible-light photocatalysts in the form of zinc bismuth oxide ($ZnBi_2O_4$) and graphite hybrid composites were prepared by coupling via a co-precipitation method followed by calcination at $450^{\circ}C$. The asprepared $ZnBi_2O_4$-graphite hybrid composites were tested for the degradation of rhodamine B (RhB) solutions under visible-light irradiation. The existence of strong electronic coupling between the two components within the $ZnBi_2O_4$-graphite heterostructure suppressed the photogenerated recombination of electrons and holes to a remarkable extent. The prepared composite exhibited excellent photocatalytic activity, leading to more than 93% of RhB degradation at an initial concentration of $50mg{\cdot}L^{-1}$ with 1.0 g catalyst per liter in 150 min. The excellent visible-light photocatalytic mineralization of $ZnBi_2O_4-1.0graphite$ in comparison with pristine $ZnBi_2O_4$ could be attributed to synergetic effects, charge transfer between $ZnBi_2O_4$ and graphite, and the separation efficiency of the photogenerated electrons and holes. The photo-induced $h^+$ and the superoxide anion were the major active species responsible for the photodegradation process. The results demonstrate the feasibility of $ZnBi_2O_4-1.0graphite$ as a potential heterogeneous photocatalyst for environmental remediation.

• Bulletin of the Korean Chemical Society
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• 제25권2호
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• pp.233-236
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• 2004

Total impurity analysis of a primary standard solution is one of the essential procedures to determine an accurate concentration of the standard solution by the gravimetry. Bi impurity is determined in Pb standard solutions by inductively coupled plasma mass spectrometry (ICP-MS). The direct nebulization of the Pb standard solution produces a significant amount of the Pb matrix-induced molecular ions which give rise to a serious spectral interference to the Bi determination. In order to avoid the spectral interference from the interferent $^{208}PbH^+$, the hydride generation method is employed for the matrix separation. The Bi hydride vapor is generated by reaction of the sample solution with 1% sodium borohydride solution. The vapor is then directed by argon carrier gas into the ICP after separation from the mixture solution in a liquid-gas separator made of a polytetrafluoroethylene membrane tube. The presence of 1000 ${\mu}$g/mL Pb matrix caused reduction of the bismuthine generation efficiency by about 40%. The standard addition method is used to overcome the chemical interference from the Pb matrix. Optimum conditions are investigated for the hydride-generation ICPMS. The detection limit of this method is 0.5 pg/mL for the sample solutions containing 1000 ${\mu}$g/mL Pb matrix.

• 한국전기전자재료학회논문지
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• 제23권12호
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• pp.949-955
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• 2010

Nd and Ti co-doped bismuth ferrite $(Bi_{1-x}Nd_x)(Fe_{1-y}Ti_y)O_3$ (x, y = 0, 0.05, 0.1, 0.2) ceramics and thin films were synthesized through the conventional mixed-oxide process and pulsed laser deposition (PLD), respectively. Nd and Ti co-doping effect was examined with emphasis on how these impurities affect phase formation behavior as there could be the improvement in leakage current problems often associated with multiferroic $BiFeO_3$ (BFO) thin films. The lattice constants of BFO ceramics decreased with Nd doping concentration up to 10mol%, while they further decreased with Nd and Ti co-doping to about 20%. BFO thin films obtained by the PLD process revealed random polycrystalline structure. Similar to bulk BFO ceramic, Nd and Ti co-doping effectively suppressed the formation of unwanted secondary phase and thus stabilized the perovskite phase in BFO thin films.