• Title/Summary/Keyword: Layered perovskite

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Comparison of Electrical Conductivities in Complex Perovskites and Layered Perovskite for Cathode Materials of Intermediate Temperature-operating Solid Oxide Fuel Cell (중·저온형 고체산화물 연료전지 공기극 물질로 사용되는 이중층 페로브스카이트와 컴플렉스 페로브스카이트의 전기 전도도 비교)

  • Kim, Jung Hyun
    • Journal of the Korean Ceramic Society
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    • v.51 no.4
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    • pp.295-299
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    • 2014
  • Electrical conductivities of complex perovskites, layered perovskite and Sr doped layered perovskite oxides were measured and analyzed for cathode materials of Intermediate Temperature-operating Solid Oxide Fuel Cells (IT-SOFCs). The electrical conductivities of $Sm_{1-x}Sr_xCoO_{3-\delta}$ (x = 0.3 and 0.7) exhibit a metal-insulator transition (MIT) behavior as a function of temperature. However, $Sm_{0.5}Sr_{0.5}CoO_{3-\delta}$ (SSC55) shows metallic conductivity characteristics and the maximum electrical conductivity value compared to the values of $Pr_{0.5}Sr_{0.5}CoO_{3-\delta}$ (PSC55) and $Nd_{0.5}Sr_{0.5}CoO_{3-\delta}$ (NSC55). The electrical conductivity of $SmBaCo_2O_{5+\delta}$ (SBCO) exhibits a MIT at about $250^{\circ}C$. The maximum conductivity is 570 S/cm at $200^{\circ}C$ and its value is higher than 170 S/cm over the whole temperature range tested. $SmBa_{0.5}Sr_{0.5}Co_2O_{5+\delta}$ (SBSCO), 0.5 mol% Sr and Ba substituted at the layered perovskite shows a typically metallic conductivity that is very similar to the behavior of the SSC55 cathode, and the maximum and minimum electrical conductivity in the SBSCO are 1280 S/cm at $50^{\circ}C$ and 280 S/cm at $900^{\circ}C$.

Exfoliation of Dion-Jacobson Layered Perovskite into Macromolecular Nanoplatelet

  • Lee, Won-Jae;Yeo, Hyun Jung;Kim, Do-Yun;Paek, Seung-Min;Kim, Young-Il
    • Bulletin of the Korean Chemical Society
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    • v.34 no.7
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    • pp.2041-2043
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    • 2013
  • A layered perovskite of Dion-Jacobson phase, $RbLaTa_2O_7$, was successfully exfoliated into colloidal suspension via successive ion-exchange and intercalation reaction. The pristine perovskite $RbLaTa_2O_7$ was synthesized by conventional solid-state reaction, and then, it was ion-exchanged with hydrochloric acid to obtain a protonic form of perovskite. The resulting proton-exchanged perovskite was reacted with ethylamine to increase interlayer spaces for further intercalation reaction. Finally, the ethylamine-intercalated form was exfoliated into nanosheets via an intercalation of bulky organic cations (tetrabutylammonium). According to X-ray diffraction (XRD) analysis, the TBA-intercalated form showed remarkably increased interlayer spacing (${\Delta}d$ = 1.67 nm) in comparison with that of the pristine material. Transmission electron microscopic image of exfoliated perovskite clearly revealed that the present exfoliated perovskite were composed of very thin layers. This exfoliated perovskite nanosheets could be applicable as building blocks for fabricating functional nanocomposites.

Synthesis and Characterization of Layered Perovskite $La_{1+x}Sr_{2-x}Mn_2O_7$ Phases (층상구조형 Perovskite $La_{1+x}Sr_{2-x}Mn_2O_7$ 상의 합성 및 특성연구)

  • 송민석;서상일;이재열
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1998.11a
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    • pp.271-274
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    • 1998
  • Metallic ferromagnet LA$_{1-x}$ Sr$_{x}$MnO$_3$ has received considerable attentions because of its metallic conductivity and giant magnetic resistivity. It is generally believed that layered perovskite SrO(LA$_{1-x}$ Sr$_{x}$MnO$_3$)$_{n}$ phase is insulating and shows no metallic transition. But recent report revealed that some single crystal SrO(LA$_{1-x}$ Sr$_{x}$MnO$_3$)$_{n}$ phase showed MR effect. In this study, layered perovskite SrO(LA$_{1-x}$ Sr$_{x}$MnO$_3$)$_2$ Phases were synthesized by solid state reaction at 140$0^{\circ}C$ in air atmosphere, for wide range of x and their phases were confirmed by X-ray diffraction. Electrical and magnetic properties were measured down to 10K and the possibility of MR effects was investigated.as investigated.

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The preparation and Characterization of Bismuth Layered Ferroelectric Thin Films by Sol-Gel Process (솔-젤법을 이용한 Bismuth Layered Structure를 가진 강유전성 박막의 제조 및 특성평가에 관한 연구)

  • 주진경;송석표;김병호
    • Journal of the Korean Ceramic Society
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    • v.35 no.9
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    • pp.945-952
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    • 1998
  • Ferroelectric Sr0.8Bi2.4Ta2O9 stock solutions were prepared by MOD(Metaloganic Decompostion) process. The phase transformation for the layered perovskite of the SBT thin films by changing RTA(Rapid her-mal Annealing) temperatuer from 700$^{\circ}C$to 780$^{\circ}C$ were observed using XRD and SEM. Layered perovskite phase began to appear above 740$^{\circ}C$ and then SBT thin films were annealed at 800$^{\circ}C$ for 1hr for its com-plete crystallization. The specimens showed well shaped hysteresis curves without post annealing that car-ried out after deposition of Pt top electrode. The SBT thin films showed the asymmetric ferroelectric pro-perties. It was confirmed that the properties were caused by interface effect to SBT and electrode by leak-age current density measurement and asymmetric properties reduced by post annealing. At post annealing temperature of 800$^{\circ}C$ remanant polarization values (2Pr) were 6.7 9 ${\mu}$C/cm2 and those of leakage current densities were 3.73${\times}$10-7 1.32${\times}$10-6 A/cm2 at 3, 5V respectively. Also bismuth bonding types of SBT thin film surface were observed by XPS.

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Syntheses and Characteristics of Layered Perovskite $La_{2-x}Ca_{1+x}Mn_{2}O_{7}$ (층상구조형 페롭스카이트 $La_{2-x}Ca_{1+x}Mn_{2}O_{7}$상의 합성 및 특성)

  • 서상일;이재열
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2000.11a
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    • pp.555-558
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    • 2000
  • Layered perovskite La$_{2-x}$Ca$_{l-x}$Mn$_2$O$_{7}$ phases were synthesized by solid state reaction. Single phase R-P could be obtained in the range of 0.4$_{2-x}$Ca$_{l-x}$Mn$_2$O$_{7}$. About 30% of MR ratio was obtained at 270K when 5 T of magnetic field was applied.ied.ied.ied.

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Investigation on the Structural, Electrical and Magnetic Properties of Layered Perovskite Manganite La0.5Sr1.5Mn0.5Cr0.5-xFexO4 (x=0.15, 0.3) System (층상 페로브스카이트 구조인 La0.5Sr1.5Mn0.5Cr0.5-xFexO4 (x=0.15, 0.3) 망가나이트의 구조적, 전기적, 자기적 특성의 연구)

  • Singh, Devinder
    • Journal of the Korean Chemical Society
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    • v.55 no.4
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    • pp.697-702
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    • 2011
  • The new layered perovskite manganites $La_{0.5}Sr_{1.5}Mn_{0.5}Cr_{0.5-x}Fe_xO_4$ (x=0.15, 0.3) have been prepared by standard ceramic method. The powder X-ray diffraction studies show that the phases crystallize with tetragonal unit cell in the space group I4/mmm. The electrical transport properties suggest that the phases show insulating behaviour and the electrical conduction in the phases occurs by a 3D variable range hopping mechanism. The magnetic properties suggest that both the phases are antiferromagnetic.

Syntheses and structure refinement of $Ln_{x}MnO_{4}$ {Ln=Gd, Nd, Pr, Sm} ($Ca_{2-X}-Ln_{x}MnO_{4}$상의 합성과 결정구조 정밀화 {Ln=Gd, Nd, Pr, Sm})

  • 서상일;이재열
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2000.07a
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    • pp.726-729
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    • 2000
  • Though L $a_{1+x}$S $r_{2-x}$M $n_2$ $O_{7}$ n=2 R-P phases have been well known to have CMR effect, it was generally believed that n=1 phase was insulating. But recently monolayered perovskite $Ca_{2-x}$L $n_{x}$Mn $O_4$phase has been reported to show magnetoresistance. In this study, layered perovskite $Ca_{2-x}$L $n_{x}$Mn $O_4$ (x=0, 0.5, Ln=Pr, Nd, Sm, Gd) phases were synthesized by solid state reaction and their structures were refined by Rietveld method. The space groups of $Ca_2$Mn $O_4$, N $d_{0.5}$C $a_{1.5}$Mn $O_4$phases were refined as C2cb and Fmmm, respectively.y.ely.y.y.y.y.y.y.

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The Preparation and Characterization of Bismuth Layered Ferroelectric Thin Films by Sol-Gel Process (II. Dielectric Properties of Ferroelectric $Sr_{0.7}/B_{2.3}(Ta_{1-x}Nb_x)_2O_9$ Thin Films Prepared by MOD Process) (솔 - 젤법을 이용한 Bismuth Layered Structure를 가진 강유진성 박막의 제조 및 특성평가에 관한 연구 (II. MOD법으로 제조한 강유전성 $Sr_{0.7}/B_{2.3}(Ta_{1-x}Nb_x)_2O_9$ 박막의 유전특성))

  • 최무용;송석표;정병직;김병호
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.12 no.1
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    • pp.62-68
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    • 1999
  • Ferroelectric $Sr_{0.7}/B_{2.3}(Ta_{1-x}Nb_x)_2O_9$(x=0, 0.1, 0.2, 0.3) thin films were deposited on $Pt/SiO_2/Si$ substrate by MOD(Metalorganic Decomposition) process. Metal carboxylate and metal alkoxide were used as precursors, and 2-methoxyethanol, xylene as solvents. After spin coating, thin films were pre-annealed at $400^{\circ}C$, followed by RTA(Rapid Thermal Annealing) and final annealing at $800^{\circ}C$ in oxygen atmosphere. These procedures were repeated three times to obtain thin films with the thickness of $2000{\AA}$. To enhance the nucleation and growth of layered-perovskite phase, thin films were rapid-thermally annealed above $720^{\circ}C$ in oxygen atmosphere. As RTA temperature increased, fluorite phase was transformed to layered-perovskite phase. And the change of Nb contents affected dielectric / electrical properties and microstructure. The ferroelectric characteristics of $Sr_{0.7}/B_{2.3}(Ta_{1-x}Nb_x)_2O_9$ thin film were Pr=8.67 $\mu{C}/cm^2$, Ec=62.4kV/cm and $I_{L}=1.4\times10^{-7}A/cm^2$ at the applied voltage of 5V, respectively.

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Synthesis and Characterization of Molecular Composite Prepared from Layered Perovskite Oxide, $HLa_2Ti_2NbO_{10}$

  • 홍영식;김시중
    • Bulletin of the Korean Chemical Society
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    • v.18 no.6
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    • pp.623-628
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    • 1997
  • A layered perovskite oxide, $RbLa_2Ti_2NbO_{10}$, was prepared and investigated for proton exchange and intercalation behaviors. Its protonated form, $Hla_2Ti_2NbO_{10}$, exhibits the Bronsted acidity and reacts with organic amines. Polyoxonuclear cation, 4Al_{13}$, was then introduced into the interlayer by refluxing octylamine-intercalated compound with an $Al_{13}$ pillaring solution. These layered oxides were characterized by X-ray diffractometer, thermogravimeter, FT-infrared spectrometer and elemental analyzer. It is observed that the polyoxonuclear cation-pillared material exhibits a bilayer structure and is thermally more stable than organic counterpart at higher temperatures. The surface area of the pillared material annealed at 400 ℃ was the value of 25.1 m²/g.