• The Korean Journal of Ceramics
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• 제6권1호
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• pp.21-26
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• 2000

Nanosized powders of trimetallic orthoferrites containing La and Sm in different ratios were synthesised by the thermal decomposition at low temperatures of the corresponding hexacyanocomplexes. The precursors and their decomposition products were analyzed by simultaneous thermogravimetric and differential thermal analysis (TG/DTA), x-ray diffraction (XRD) and Raman spectroscopy. Single phase trimetallic precursors and oxides were obtained. The crystal structure of the perovskitic oxides was orthorhombic, and the lattice parameters were affected by the ionic size of the rare earth elements present in the oxides. Raman spectroscopy showed a disorder effect in the vibrational bands with increasing the La content.

• 공업화학
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• 제9권6호
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• pp.803-810
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• 1998

능금산법으로 제조된 페롭스카이트 촉매에서 입자상물질의 연소반응에 대하여 연구하였다. 페롭스카이트 산화물의 A 및 B site에 금속이온을 치환시켜 연소반응의 활성을 증가시켰다. 또한 반응온도, 산소의 농도, 공간속도, $SO_2$ 및 물의 영향에 대하여 조사하였다. $LaCoO_3$형 촉매의 A site에 알칼리족 금속을 치환시키면 연소개시 온도가 낮아졌고, 알카리족 금속은 Cs>K>Na의 순서로 연소활성을 증가시켰다. 그러나 $La_{0.6}Cs_{0.4}CoO_3 $촉매에서 B site에 Fe나 Mn을 치환시키더라도 연소개시 온도의 변화가 거의 없었다. 산소의 농도가 증가함에 따라 연소개시 온도는 낮아졌고 이산화탄소의 생성속도는 산소분압의 영향을 별로 받지 않았다. 한편 공간속도의 증가에 따라 연소개시온도가 낮아졌고, 이산화황에 대한 촉매의 비활성화는 일어나지 않았으며, 반응물 중에 첨가된 물에 의해 연소반응이 촉진되었다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1112-1113
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• 2006

The perovskite- type oxide $(ABO_3)$ containing transition metals on the B-site show mixed (electronic/ionic) conductivity. These mixed-conductivity oxides are promising materials for oxygen permeating membranes. The main objective of this research work is to synthesize and characterization ceramic powders of the Sr-Co-Fe-O system for methane conversion using membrane reactor. SCFO powders were synthesized from the route was based on the complex method of combination of acid EDTA and citrate and shown be available by control efficient of synthesis to performed $SrCo_{0.8}Fe_{0.2}O_{3-\delta$, moreover, it presented easy implementation, reproducibility and operation. Powder ceramic was characterized by XRD, microscopic optic, SEM and TG-DTA.

• 한국결정성장학회지
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• 제18권5호
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• pp.200-204
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• 2008

기계화학공정(MCP; Mechano Chemical Process)은 원료 분말이 기계적인 에너지로 인해 상 형성이 활성화되기 때문에 기존의 볼밀링을 이용한 고상반응에서 필수적인 높은 온도에서의 하소 공정이 필요하지 않다. 본 연구에서는 고 에너지 MCP 방법을 이용하여 perovskite 구조를 가지는 PLT 나노 분말을 제조하였다. 특히, 일반적으로 출발물질로 염을 이용하는 것과 달리 산화물을 원료 분말로 사용하여 어떠한 열처리 공정 없이 PLT 나노 분말을 합성하였다. 또한 건식으로 밀링을 하여 분말 건조 공정이 필요 없어서 공정이 간단하다. MCP 밀링은 시간 별로 12시간까지 진행하였으며, 제조된 분말의 상 분석과 결정면 분석 결과 3시간 이후에는 perovskite 구조의 순수한 PLT 상을 형성하였다. 또한 마이크로 크기의 원료 분말이 밀링 3시간이 지나자 약 20 nm 크기의 균일한 나노 입자가 생성되었다.

• 자연과학논문집
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• 제14권2호
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• pp.41-54
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• 2004

$LaMnO_3$(a=$5.51\AA$, c=$13.33\AA$) 페로브스카이트형 복합산화물에서 A site인 La자리에 Sr을 치환시킨 $La_{0.9}Sr_{0.1}MnO_3$(a=$5.33\AA$, c=$13.27\AA$)와 B site인 Mn을 Cu로 치환시킨 $LaMn_{0.9}Cu_{0.1}O_3$(a=$5.52\AA$, c=$13.31\AA$) 복합산화물을 Citrate sol-gel법을 이용하여 합성하였으며 분말 X-ray회절 분석기(XRD)을 이용하여 Rhombohedral의 페로브스카이트 구조임을 확인하였다. 수소 환원분위기에서의 TRR결과에 의하면 이들 산화물의 산소 화학양론은 $LaMnO_{3.16}$, $La_{0.9}Sr_{0.1}MnO_{3.10}$, $LaMn_{0.9}Cu_{0.1}O_{3.14}$의 조성을 갖는다. $LaMnO_3$는 2단계 환원반응을 일으키지만 각 자리를 치환시킨 $LaMnO_3$ 복합산화물은 3단계 환원반응을 일으켰다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.161-161
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• 2013

Two-dimensional electron gas (2DEG) has been investigated at the heterointerface between two insulating dielectric perovskite oxides, $LaAlO_3$ (LAO)/$SrTiO_3$ (STO). Properties of the 2DEG have attracted an enormous interest in condensed matter physics due to multifunctional properties such as the coexistence of ferromagnetism and superconductivity, as well as the high electron mobility. Here, we have grown $Ta_2O_5$ thin films using pulsed laser deposition on $SrTiO_3$ substrate to investigate the electric properties of the $Ta_2O_5$/STO heterointerface. Our research reveal that the non-polar $Ta_2O_5$/$TiO_2$ heterointerface favors the formation of 2DEG similar to that at the LAO/STO heterointerface. The metallic behavior was found in this heterointerface with the current about $10{\sim}100{\mu}A$ at 5 V by using conventional I-V measurements, when the $Ta_20_5$ film thickness reaches over critical thickness, $d_c{\simeq}2uc$. The finding that electrons was localized at $Ta_2O_5$/STO heterointerface have attracted to be strong and new candidate for nanoscale oxide device applications.

• Bulletin of the Korean Chemical Society
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• 제35권6호
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• pp.1613-1618
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• 2014

Perovskite-type oxides are promising oxygen carriers in producing oxygen-enriched $CO_2$ gas stream for oxyfuel combustion. In this study, a new series of $SrCo_{1-x}Fe_xO_{3-{\delta}}$ (x = 0.2, 0.4, 0.6, 0.8) was prepared and used to produce $O_2/CO_2$ mixture gas. The phase, crystal structure, and morphological properties of $SrCo_{1-x}Fe_xO_{3-{\delta}}$ were investigated through X-ray diffraction, specific surface area measurements, and environmental scanning electron microscopy. The oxygen desorption performance of $SrCo_{1-x}Fe_xO_{3-{\delta}}$ was studied in a fixed-bed reactor system. Results showed that the different x values of $SrCo_{1-x}Fe_xO_{3-{\delta}}$ have no obvious effects on crystalline structure. However, the oxygen desorption performance of $SrCo_{1-x}Fe_xO_{3-{\delta}}$ is improved by Co doping. Moreover, $SrCo_{0.8}Fe_{0.2}O_{3-{\delta}}$ synthesized via a new EDTA method has a larger BET surface area ($40.396m^2/g$), smaller particle size (48.3 nm), and better oxygen production performance compared with that synthesized through a liquid citrate method.

• 공업화학
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• 제10권3호
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• pp.331-335
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• 1999

진이급속 산화물은 전기화학적 산소 발생/환원에 대한 bifunctional 촉매효과가 있어 금속-공기 이차전지와 같은 에너지 저장기술 개발에 연구대상이 되어왔다. Amorphous citrate precursor법을 이용하여 perovskite 구조를 갖는 La-Ca-Co 산화물과 pyrochlore 구조를 갖는 Pb-Ru 산화물을 제조하고, 이후 열처리법으로 표면적이 큰 전이금속 산화물 촉매분말을 제조하였다. PTFE 결합 기체확산형 전극의 충방전 실험을 통하여 전기화학적 산소발생/환원에 대한 좋은 촉매능을 가짐을 확인하였고, ${\pm}25mA/cm^2$의 전류밀도를 가하고 공기를 공급하면서 충방전 실험한 결과 100시간 이내에서 두촉매분말 모두 안정하였다. ACP법으로 제조한 perovskite 구조의 La0.6Ca0.4CoO3과 pyrochlore 구조의 Pb2Ru2O6가 이차전지용 공기전극 재료로 사용할 수 있음을 확인하였다.

• 한국세라믹학회지
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• 제51권4호
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• pp.231-242
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• 2014

An interconnect in solid oxide fuel cells (SOFCs) electrically connects unit cells and separates fuel from oxidant in the adjoining cells. The interconnects can be divided broadly into two categories - ceramic and metallic interconnects. A thin and gastight ceramic layer is deposited onto a porous support, and metallic interconnects are coated with conductive ceramics to improve their surface stability. This paper provides a short review on ceramic materials for SOFC interconnects. After a brief discussion of the key requirements for interconnects, the article describes basic aspects of chromites and titanates with a perovskite structure for ceramic interconnects, followed by the introduction of dual-layer interconnects. Then, the paper presents protective coatings based on spinel-or perovskite-type oxides on metallic interconnects, which are capable of mitigating oxide scale growth and inhibiting Cr evaporation.

• Bulletin of the Korean Chemical Society
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• 제15권3호
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• pp.256-260
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• 1994

Perovskite type oxides of the $Sr_xHo_{1-x}FeO_{3-y}$ system with compositions of x=0.00, 0.25, 0.50, 0.75, and 1.00 have been prepared at 1200$^{\circ}$C in air. X-ray powder diffraction assigns the compositions with x=0.00 and 0.25 to the orthorhombic crystal system and those with x=0.50, 0.75, and 1.00 to the cubic one. The unit cell volumes of solid solutions increase with x in the system. Nonstoichiometric chemical formulas were determined by Mohr salt titration. The mole ratio of $Fe^{4+}$ ions to total iron ions and the concentration of oxygen ion vacancies increase with x. Mossbauer spectra for the compositions of x= 0.00, 0.25, and 0.50 show six lines indicating the presence of $Fe^{3+}$ ions in the octahedral site. However, the presence of $Fe^{4+}$ ions may also be detected in the spectra for the compositions with x=0.25 and x=0.50. In the compositions with x=0.75 and 1.00, single line patterns show also the mixed valence state of $Fe^{3+}$ and $Fe^{4+}$ ions. The electrical conductivity in the temperature range of -100$^{\circ}$C to 100$^{\circ}$C under atmospheric air pressure increases sharply with x but the activation energy decreases with the mole ratio of $Fe^{4+}$ ion. The conduction mechanism of the perovskite system seems to be hopping of the conduction electrons between the mixed valence iron ions.