• Title/Summary/Keyword: $Bi^{3+}$

Search Result 3,927, Processing Time 0.029 seconds

Fabrication of Mg3Sb2 and Mg3Bi2 Compounds and their composites by mechanical alloying (기계적 합금법에 의한 Mg3Bi2와 Mg3Sb2 화합물 및 복합체의 제조)

  • Kim, In-Ki
    • Journal of the Korean Crystal Growth and Crystal Technology
    • /
    • v.23 no.4
    • /
    • pp.189-194
    • /
    • 2013
  • Single phase crystalline powders of $Mg_3Sb_2$ and $Mg_3Bi_2$ were prepared by mechanical alloying Mg, Sb and Bi metals with planetary ball milling for 24~48 h. The compositions of starting raw materials for single phase $Mg_3Sb_2$ and $Mg_3Bi_2$ were 3Mg : 1.8Sb and 3Mg : 1.6Bi, respectively. Two types of mechanically alloyed powders obtained were mixed at some ratios for the fabrication of $Mg_3Sb_2-Mg_3Bi_2$ composites and then hot pressed under uniaxial pressure of 70 MPa at 723 K for 1 h. The main phase of composites was a stable phase similar to $Mg_3Bi_2$ phase with a small amount of Bi phase. The distributions of Sb and Bi elements on EDS mapping images were discontinuous and their compositional contours were clear, which means that the hot pressed specimens were composites composed of two compounds of $Mg_3Sb_2$ and $Mg_3Bi_2$.

Visible-light Photocatalytic Activity of BiOCl/Bi3O4Cl Nanocomposites

  • Gao, Bifen;Chakraborty, Ashok Kumar;Yang, Ji-Min;Lee, Wan-In
    • Bulletin of the Korean Chemical Society
    • /
    • v.31 no.7
    • /
    • pp.1941-1944
    • /
    • 2010
  • The heterojunction structures of BiOCl/$Bi_3O_4Cl$, exhibiting considerable visible-light photocatalytic efficiency, were prepared by a simple wet-chemical process at ambient condition. The prepared nanocomposites were characterized by XRD, TEM, and UV-visible diffuse reflectance spectra. Under visible light (${\lambda}\geq$420 nm) irradiation, BiOCl/$Bi_3O_4Cl$ exhibited an enhanced photocatalytic activity in decomposing 2-propanol (IP) in gas phase and salicylic acid (SA) in aqueous solution, whereas the bare BiOCl and $Bi_3O_4Cl$ showed negligible activities. It is deduced that the remarkable visible-light photocatalytic activity of the BiOCl/$Bi_3O_4Cl$ originates from the hole $(h^+)$ transfer between VB of the $Bi_3O_4Cl$ and BiOCl semiconductors.

Exsolution of $Bi_4Ge_3O_12$ in $Bi_12GeO_20$ Crystals Grown by Pulling Method (인상 육성한 $Bi_12GeO_20$ 결정내의 $Bi_4Ge_3O_12$석출상)

  • 이태근;정수진
    • Journal of the Korean Ceramic Society
    • /
    • v.28 no.12
    • /
    • pp.981-988
    • /
    • 1991
  • Various crystal defects such as voids, inclusions dislocations, stacking faults and precipitates were observed in the Czochralski-grown Bi12GeO20 crystals. Particularly, precipitates were found in the whole crystals. The phase of these precipitates was identified as Bi4Ge3O12 by EPMA and transmission electron microscopy. The precipitates were produced by pulling rapidly from a non-stoichiometric charge. During the pulling of Bi12GeO20 crystals, the melt composition of stoichiometric charge was changed Bi-deficent with gradual volatilization of Bi2O3. Precipition of the second phase may have been affected by an abrube thermal stress. By adding excess Bi2O3 into the stoichiometric batch, the precipitation of Bi4Ge3O12 was suppressed. At a pulling speed of 2 mm/hr, clear and precipitate from crystals of Bi12GeO20 were grown from the melt of the Bi2O3 excess charge.

  • PDF

Growth of Bi:YIG Thick Films by Change of PO/Bi2O3 Molar Ratio (PO/Bi2O3 변화에 따른 Bi:YIC 단결정 후박의 성장)

  • 윤석규;김근영;김용탁;정현민;임영민;윤대호
    • Journal of the Korean Ceramic Society
    • /
    • v.39 no.6
    • /
    • pp.589-593
    • /
    • 2002
  • The single crystalline thick fi1ms of Bi:Y$_3$Fe$_{5}$ $O_{12}$(Bi:YIG) were grown on (GdCa)$_3$(GaMgZr)$_{5}$ $O_{12}$(SGGG) by Liquid Phase Epitaxy (LPE). The changes of lattice mismatch and Bi concentration were investigated in the thick film growth as a function of PO/Bi$_2$ $O_3$ molar ratio, with keeping constant of substrate rotation speed, supercooling and growth time. It was grown that the lattice constant of the garnet single crystalline thick films and Bi content increased with decreasing of PO/Bi$_2$ $O_3$ molar ratio. Bi concentration decreased with increasing of the film thickness.

Band-Gap Energy and Thermoelectric Properties of 90% $Bi_2Te_3-10% Bi_2Se_3$ Single Crystals (90% $Bi_2Te_3-10% Bi_2Se_3$ 단결정의 밴드갭 에너지와 열전특성)

  • Ha, Heon-Pil;Hyeon, Do-Bin;Hwang, Jong-Seung;O, Tae-Seong
    • Korean Journal of Materials Research
    • /
    • v.9 no.4
    • /
    • pp.349-354
    • /
    • 1999
  • The temperature dependences of the Hall coefficient, carrier mobility, electrical resistivity, Seebeck coefficient, thermal conductivity, and figure-of-merit of the undoped and $CdI_2$-doped 90% $Bi_2Te_3-10% Bi_2Se_3$, single crystals, grown by the Bridgman method, have been characterized at temperatures ranging from 77K to 600K. The saturated carrier concentration and degenerate temperature of the undoped 90% $Bi_2Te_3-10% Bi_2Se_3$ single crystal are $5.85\times10_{18}cm^{-3}$ and 127K, respectively. The scattering parameter of the 90% $Bi_2Te_3-10% Bi_2Se_3$ single crystal is determined to b -0.23, and the electron mobility to hole mobility ratio ($\mu_e/\mu_h)$ is 1.45. The bandgap energy at 0K of the 90% <$Bi_2Te_3-10% Bi_2Se_3$ single crystal is 0.200 eV. Adding $CdI_2$as a donor dopant, a maximum figure-of-merit of $3.2\times10^{-3}/K$$CdI_2$-doped specimen.

  • PDF

Thermoelctric Propretries of Bi2Te3 Fabricated by Mechanical Grinding-Mixing Process (기계적분쇄-혼합공정에 의해 제조된 Bi2Te3 소결체의 열전특성)

  • 이근길
    • Journal of Powder Materials
    • /
    • v.7 no.1
    • /
    • pp.6-11
    • /
    • 2000
  • Two kinds of Bi2Te3 powders, pure Bi2Te3/2vol.%ZrO2, have been prepared by a mechanical grinding process process. Effect of mixing of the powders on thermoelectric of the sintered body has been investigated by measuring Seebeck Coeffcient, specific electric resistivity and thermal conductivity. With an increase in the weight fraction of the Bi2Te3/2vol.%ZrO2 powder from 0 to 40wt.%. Especially, the figure of merit of the mixedBi2Te3 sintered body increases and thereafter dedreases above 40wt.%. Especially. the figure of merit of the mixed Bi2Te3 sintered bodies with mixing of Bi2Te3/2vol.%ZrO2 powder increased about 1.3time in comparison with the value of the specimen before mixing. Mixing of two kinds of Bi2Te3 powders which have different theramal and electric propertries with each other seemed to be useful methob to increase the figure of merit of Bi2Te3 sintered body.

  • PDF

The Effect of Bismuth Composition Controlled by Heat Treating Heterostructure on the Ferroelectric Properties of SrBi$_2$Ta$_{2-x}$Nb$_x$O$_9$ Thin Films (Heterostructure 열처리에 의한 Bi 조성 제어가 SrBi$_2$Ta$_{2-x}$Nb$_x$O$_9$ 박막의 강유전 특성에 미치는 영향)

  • 박윤백;이전국;정형진;박종완
    • Journal of the Korean Ceramic Society
    • /
    • v.35 no.10
    • /
    • pp.1040-1048
    • /
    • 1998
  • Ferroelectric properties of{{{{ { { { {SrBi }_{2 }Ta }_{2-x }Nb }_{x }O }_{9 } }} (SBIN) thin films were affected by the amount of Bi content in SBTN. The addition of Bi into the SBTN films could be accomplished by heat treating SBTN/Bi2O3/SBTN het-erostructures fabricated by r.f. magnetron sputtering method. The variation of Bi content was controlled by changing the thickness of the sandwiched Bi2O3 in SBTN/Bi2O3/SBTN heterostructure from 50 to 400$\AA$. As changing the thickness of the sandwiched Bi2O3 in Bi2O3 films was increased from 0 to 100$\AA$ the grain grew faster and the ferroelectric pro-perties were improved. On the other hand when the thickness of Bi2O3 films was thicker than 150$\AA$ the fer-roelectric properties were deteriorated Especially for SBTN thin films inserted by 400$\AA$ Bi2O3 layer a Bi2Phase appeared as a second phase resulting in poor ferroelectric properties. The maximum remanent po-larization (2Pr) and coercive field(Ec) were obtained for the SBTN/Bi2O3/(100$\AA$)/SBTN thin films. In this case 2Pr and Ec were 14.75 $\mu$C/cm2 and 53.4kV/cm at an applied voltage of 3V respectively.

  • PDF

Effect of the Structure of MoO3/bismuth molybdate Binary Phase Catalysts on the Selective Oxidation of Propylene (MoO3/bismuth molybdate 혼합 2상 촉매의 구조에 따른 프로필렌 선택산화반응 특성)

  • Cha, T.B.;Choi, M.J.;Park, D.W.;Chung, J.S.
    • Applied Chemistry for Engineering
    • /
    • v.3 no.1
    • /
    • pp.53-63
    • /
    • 1992
  • M/BM -series catalysts, $MoO_3$ supported on ${\alpha}-Bi_2Mo_3O_{12}$ were also prepared by impregnation method. BM/M-series catalysts, ${\alpha}-Bi_2Mo_3O_{12}$ supported on $MoO_3$ were also prepared by coprecipitation. Structure and catalytic properties of the two phase catalysts were studied by means of using nitrogen adsorption, X-ray diffraction, and scanning electron microscopy. The reaction test for the selective oxidation of propylene to acrolein over Bi-molybdate catalysts was studied using a fixed-bed reactor system. In M/BM-series catalysts, $MoO_3$ was dispersed on ${\alpha}-Bi_2Mo_3O_{12}$, and the crystal structure of ${\alpha}-Bi_2Mo_3O_{12}$ remains unchanged by the presence of excess $MoO_3$. However the surface morphology and bulk structure of BM/M-series catalysts were altered probably because the precipitated $Bi(OH)_3$ reacted with $MoO_3$ during the calcination to form ${\alpha}-Bi_2Mo_3O_{12}$ phase. The results of propylene oxidation on both series catalysts showed that the reaction took place over the surface of ${\alpha}-Bi_2Mo_3O_{12}$ particle and the role of excess $MoO_3$ was to supply oxygen to ${\alpha}-Bi_2Mo_3O_{12}$. These increasing effects on activity were also observed in the mechanical mixtures of ${\alpha}-Bi_2Mo_3O_{12}$ and $MoO_3$.

  • PDF

Occurrence and Mineral Chemistry of Pb-Ag-Bi-S System Minerals in the Nakdong As-Bi Deposits, South Korea (낙동 비소-비스무스 광상의 Pb-Ag-Bi-S계 광물의 산출양상과 화학조성)

  • Shin, Dong-Bok
    • Economic and Environmental Geology
    • /
    • v.39 no.6 s.181
    • /
    • pp.643-651
    • /
    • 2006
  • The Pb-Ag-Bi-S system minerals such as galena-matildite solid solutions, cosalite and heyrovskyite occur in the Nakdong As-Bi deposits. Galena-matildite solid solutions commonly coexisting with native bismuth fill in microfractures of pyrite grains and form irregular shapes. Cosalite forms composite grains including native bismuth, heyrovskyite and Bi-Te-S system minerals in the matrix of quartz vein. Matildite from the Nakdong deposits has an end member composition, $Ag_{1.07-1.11}Bi_{1.12-1.20}S_2$, and an excess concentration of $0.3{\sim}2.4$ mole % $Bi_2S_3$ compared to the stoichiomeoic value. PbS concentrations in $PbS-AgBiS_2$ solid solutions do not exceed 54 mole %. The average chemical composition of cosalite in the study area is $Pb_{1.79}Bi_{2.29}Ag_{0.12}S_5$. Pb is slightly depleted compared to the ideal composition, but the concentrations of Ag and Cu reach as much as 1.47 wt.% and 0.27 wt.%, respectively. Heyrovskyite has the chemical formula of $Pb_{5.01}Ag_{0.26}Bi_{2.70}S_9$ suggesting that there occurs the coupled substitution of $2Bi^{3+}$ for $3Pb^{2+}$ as well as that of $Ag^++Bi^{3+}$ for $2Pb^{2+}$. The genetic condition of Pb-Ag-Bi-S system minerals can be confined to the temperature of $220{\sim}270^{\circ}C$ and the pressure below 200 bars.

Effects of Bi in Sn-based Pb free solder on interfacial reaction and Electroless Ni-PUBM (Electroless Ni-PUBM과 Sn-based 무연솔더의 계면반응에 미치는 Bi합금원소의 영향)

  • 조문기;전영두;백경욱;김중도;김용남
    • Proceedings of the International Microelectronics And Packaging Society Conference
    • /
    • 2003.11a
    • /
    • pp.128-132
    • /
    • 2003
  • 무전해 Ni-P UBM과 3가지 경우의 무연 솔더간의 계면연구를 통해 Bi가 솔더의 합금원소로 들어감에 따라 계면반응에 어떠한 영향을 줄 수 있는 가를 연구했다. 3가지 다른 무연 솔더는 Bi가 각각 $0wt\%,\;4.8wt\%,\;58wt\%$들어간 Sn3.5Ag, Sn3.5Ag4.8Bi, Sn58Bi 이다. reflow를 수행한 후에 세 가지 솔더에서 나타나는 계면에서의 IMC는 $Ni_3Sn_4$로서 어떤 다른 솔더도 Bi를 함유한 IMC가 계면에선 관찰되지 않았다. 다만 SnAgBi 솔더의 경우 특이하게 솔더내에서 침상의 $Ni_3Sn_4$가 reflow후에 관찰되었다. 또한 반응속도의 척도가 되는 Ni-P UBM소모속도를 비교해 보면 reflow후의 SnAg와 SnAgBi의 경우에는 비슷하나 SnBi의 경우에는 알서 두 솔더에 비해 눈에 띠게 느림을 관찰하였다. 이러한 Ni-P UBM의 소모경향을 Bi의 함량, 그에 따른 Sn의 상대적인 함량의 관점에서 고찰하고자 한다.

  • PDF