• Korean Chemical Engineering Research
• /
• 제43권5호
• /
• pp.627-631
• /
• 2005

고온수증기 전기분해의 양극물질로 이용될 수 있는 $(La_{0.8}Sr_{0.2})_{0.95}MnO_3$/yttria-stabilized zirconia(LSM/YSZ) 복합체 전극을 x-ray diffractometry, scanning electron microscopy 그리고 galvanodynamic, galvanostatic polarization method로 연구하였다. 이런 목적으로 perovskite-type의 LSM 물질은 공침법을 이용하여 제조하였으며, 8 mol% YSZ와 몰분율을 달리하여 복합체 전극을 합성하였다. LSM/YSZ 복합체 전극은 평판의 YSZ 전해질에 LSM/YSZ 복합체를 스크린 프린팅 후 $1,100^{\circ}C$에서 열처리 코팅하여 제조하였다. 실험결과로부터 LSM/YSZ 복합체 전극의 전기화학적 특성은 전극을 이루는 삼상계면의 구조와 전기분해 온도에 영향을 받는다는 것을 확인하였다.

• 한국결정학회:학술대회논문집
• /
• 한국결정학회 2003년도 춘계학술연구발표회
• /
• pp.8-8
• /
• 2003

Electron-phonon interaction plays a significant role in forming of colossal magnetoresistance effect (CMR). Polaron formation was observed by neutron diffraction and by extended X-ray absorption fine structure (EXAFS) analysis. Local probe as given by the EXAFS is a useful method to study the polaronic charge and its dependence on temperature and ions size. Here we present the EXAFS study of polaronic charge in La/sub 0.7/Ca/sub 0.3-X/Ba/sub X/MnO₃ compositions. The single phase La/sub 0.7/Ca/sub 0.3-X/Ba/sub X/MnO₃ manganites (x=0; 0.03; 0.06, ..., 0.3) were prepared by ceramic technology [1]. The Curie temperature was determined by extrapolation of the temperature dependence of the magnetization (down to zero magnetization). EXAFS experiments were carried out at the 7C EC beam line of the Pohang Light Source (PLS) in Korea. The atomic pair distribution functions (PDF) were obtained by re-regularization method [2] from filtered spectra. The PDF for the x=0.3 sample showed a single peak function and for x=0.0, 0.03, 0.06, 0.09, 0.12 compositions were asymmetric in agreement with a small Jahn-Teller elongation of two (short and long) bonds of the MnO/sub 6/ octahedron. Dispersion, σ/sub Min-O//sup 2/, and asymmetry, σ/sub Min-O//sup 3/, of the Mn-O bond distances varied significantly with x and showed a maximums at x=0.09. The maximum of σ/sub Min-O//sup 2/ is caused by increase of dynamic rms displacements of the Mn-O distances near the T/sub C/. The observed x dependence of σ/sub Min-O//sup 3/ reflects the reduction of charge carriers mobility at approaching to T/sub C/ from low as well as high temperatures.

• 한국수소및신에너지학회논문집
• /
• 제24권6호
• /
• pp.543-549
• /
• 2013

In this study, $La_{0.9}Sr_{0.1}Cr_{0.7}M_{0.3}O_{3{\pm}{\delta}}$ (M=Mn, Ru, Fe, Ni) were prepared by sol-gel method and water gas shift reaction with simulated coal-derived syngas between $400{\sim}650^{\circ}C$ was conducted to evaluate the catalytic activity of prepared catalysts. Physico-chemical properties were characterized by XRD, BET, SEM-EDS and TPR. The formation of perovskite crystallite, $LaCrO_3$ was confirmed and the highest surface area was measured with $La_{0.9}Sr_{0.1}Cr_{0.7}Mn_{0.3}O_{3{\pm}{\delta}}$. Equilibrium conversion of CO above $550^{\circ}C$ was achieved except $La_{0.9}Sr_{0.1}Cr_{0.7}Fe_{0.3}O_{3{\pm}{\delta}}$. and methanation reaction was carried out as side reaction of water gas shift reaction with $La_{0.9}Sr_{0.1}Cr_{0.7}Ni_{0.3}O_{3{\pm}{\delta}}$ and $La_{0.9}Sr_{0.1}Cr_{0.7}Ru_{0.3}O_{3{\pm}{\delta}}$. Conclusively, $La_{0.9}Sr_{0.1}Cr_{0.7}M_n{0.3}O_{3{\pm}{\delta}}$ was the most suitable catalyst of water gas shift reaction above $500^{\circ}C$ for CO conversion and hydrogen production.

• E2M - 전기 전자와 첨단 소재
• /
• 제10권2호
• /
• pp.141-149
• /
• 1997

L $a_{0.7}$S $r_{0.3}$Mn $O_{3}$ powders were prepared by both GNP(Glycine-Nitrate Process) and solid state reaction method in various of calcination temperature(800-1000.deg. C) and time in air. Also, L $a_{0.7}$S $r_{0.3}$Mn $O_{3}$ cathode contacts on YSZ(Yttria-Stabilized Zirconia) substrate were prepared by screen printing and sintering method as a function of sintering temperature(1100-1450.deg. C) in air. Sintering behaviors have been investigated by SEM(Scanning Electron Microscope) and porosity measurement. Compositional and structural characterization were carried out by X-ray diffractometer and ICP AES(Inductively Coupled Plasma-Atomic Emission Spectrometry) analysis. Electrical characterization was carried out by the electrical conductivity with linear 4 point probe method. As the calcination period increased in solid state reaction method, L $a_{0.7}$S $r_{0.3}$Mn $O_{3}$ phase increased. Although L $a_{0.7}$S $r_{0.3}$Mn $O_{3}$ single phase was obtained only for 48hrs at 1000.deg. C, in GNP method it was easy to get single and ultra-fine L $a_{0.7}$S $r_{0.3}$Mn $O_{3}$ powders with submicron particle size at 650.deg. C for 30min. The particle size and thickness of L $a_{0.7}$S $r_{0.3}$Mn $O_{3}$ cathode contact by solid state reaction method did not change during the heat treatment, while those by GNP method showed good sintering characteristics because initial powder size fabricated from GNP method is smaller than that fabricated from solid state reaction method. Based on enthalpy change from thermodynamic data and ICP-AES analysis, it was suggested to make cathode contact in composition of (L $a_{0.7}$S $r_{0.3}$)$_{0.91}$ Mn $O_{3}$ which have little second phase (L $a_{2}$Z $r_{2}$ $O_{7}$) for high efficient solid oxide fuel cells applications. As (L $a_{0.7}$S $r_{0.3}$)$_{0.91}$Mn $O_{3}$ cathode contact on YSZ substrate was sintering at 1250.deg. C the temperature that liquid phase sintering did not occur. It was possible to obtain proper cathode contacts with electrical conductivity of 150(S/cm) and porosity content of 30-40%.m) and porosity content of 30-40%.

• 한국세라믹학회지
• /
• 제38권4호
• /
• pp.370-379
• /
• 2001

PLD(pulsed laser deposition) 기법을 이용하여 LaAl $O_3$(100) 기판 위에 L $a_{0.67}$ $A_{0.33}$Mn $O_{3-{\delta}}$ (A=Ca, Sr, Ba) 에피 박막을 성장하였다. 박막의 격자 상수 및 스트레인 상태는 GID(grazing incidence X-ray diffraction)법과 투과 전자 현미경 법을 이용하여 조사하였다. 박막의 <001> 방향은 기판 표면의 수직방향에 평행하게 놓였으며, 박막의 단위포는 기판과의 격자 불일치에 기인하여 a/c=0.98인 의사-정방정 페롭스카이트(pseudo-tetragonal perovskite) 구조를 가졌다. A 자리의 양이온 반경이 증가함에 따라 단위포의 체적, $\varepsilon$$^{∥}$, 그리고 $\varepsilon$$_{⊥}$이 각각 증가하였다. L $a_{0.67}$ $A_{0.33}$Mn $O_{3-{\delta}}$ (A=Ca, Sr, Ba) 박막의 온도 및 자장에 따른 전기 전도 특성 MR(%), Tc, $T_{MI}$ 들을 조사하였으며, 이 결과들을 박막의 구조적 특성과 상관하여 고찰하였다.여 고찰하였다.

• 한국세라믹학회지
• /
• 제20권4호
• /
• pp.315-323
• /
• 1983

Effect of NiO and $MnO_2$ addtivies on the dielectric piezoelectrics and polarization-reversal properties of $(Pb_{0.936} La_{0.064})$$(Zr_{0.60}Ti_{0.40})O_3$ ceramics have been investigated. The specimens were prepared by the mixed oxide techni-que and atmosphere sintering method. The room temperature X-ray diffraction studies show that perfect perovskite solution with tetragonal structure was obtained from PLZT and its additives. The dielectric constant and dissipation factor decreased with the addition of both NiO and $MnO_2$ The Curie of Curie temperature was not observed but they displayed broadened maxima. The planar coupling factor was improved by addition of NiO and also increased with increasing sintering time carried out at 105$0^{\circ}C$ Addition of $MnO_2$ yielded a markedly high mechanical quality factor. The space-charge field decreased with the addition of NiO but increased with the addition of $MnO_2$ The planar coupling factor and space-charge field showed same dependence on the additivies. The tetragonality Curie temperature and planar coupling factor of $(Pb_{0.936} La_{0.064})$$(Zr_{0.60}Ti_{0.40})O_3$ were higher than those of $(Pb_{0.936} La_{0.064})$$(Zr_{0.568}NU_{0.032}Ti_{0.40})_{0.984}O_3$ but the grain size lattic parameter dielectric constant dissipation factor mechanical quality factor and space-charge field of the former were lower than those of the latter.

• 한국자기학회지
• /
• 제12권1호
• /
• pp.14-19
• /
• 2002

CMR 자성물질인 LSMO 페롭스카이트 망간산화물에 $^{57}$ Fe를 미량 치환한 L $a_{0.67}$S $r_{0.33}$M $n_{0.99}$$^{57}$ F $e_{0.01}$ $O_3$물질에 대하여 그 결정학적 및 자기적 특성을 x-선 회절 실험, 진동시료 자화율 측정 실험, 자기저항 실험, Mossbauer 분광 실험을 통하여 연구하였다. 물을 용매로 한 sol-gel법을 이용하여 단일상의 polycrystalline L $a_{0.67}$S $r_{0.33}$M $n_{0.99}$$^{57}$ F $e_{0.01}$ $O_3$분말시료를 합성하였으며, 결정구조는 격자 상수 $a_{0}$ =5.480 $\AA$, $\alpha$=60.259$^{\circ}$를 갖는 rhombohedral구조로 분석되었다. 상온에서의 magnetic moment 값은 60.15 emu/g임을 알 수 있었고 큐리온도( $T_{c}$)는 375 K로 결정하였다. Mossbauer 스펙트럼은 20-400 K 영역에서 측정되었으며, 온도증가에 따라 관측되는 비대칭적 선폭증가는 이방성 초미세자기장 요동 모델로 설명할 수 있었다. 이 때 이방성 초미세 자기장이 + $H_{0}$ 및 - $H_{0}$ 로 진동하는 시간 비율은 $P_{+}$= 0.80 및 $P_{-}$= 0.20으로 분석되었다. 이방성 초미세자기장 요동 진동수로부터 온도변화에 따른 이방성 에너지를 계산하였으며, 150 K에서 124.01 erg/$cm^3$로 최대값을 갖음을 알 수 있었다.다.었다.었다.다.었다.

• 한국결정학회지
• /
• 제13권1호
• /
• pp.41-47
• /
• 2002

La/sub 1-x/Ca/sub x/MnO₃ 망간산화물을 할로겐 램프를 열원으로 하는 FZ법으로 결정성장시켰다. 결정성장조건은 공기 분위기 하에서 성장속도 4∼6 mm/hr, 원료봉의 회전속도 45∼50 rpm, 성장되는 결정의 회전속도는 20-25rpm이었다. 성장된 시편의 분석은 XRD, SEM, EPMA를 이용하였으며 EBSD로 결정성장 방위를 분석하였다. 전자기적 물성 측정은 4단자 탐침법으로 Quantum Design PPMS를 이용하였고 215 K에서 462%의 MR값을 얻을 수 있었다.

• 한국자기학회:학술대회 개요집
• /
• 한국자기학회 2011년도 임시총회 및 하계학술연구발표회
• /
• pp.60-61
• /
• 2011

• 한국자기학회지
• /
• 제8권4호
• /
• pp.179-184
• /
• 1998

일반적으로 페로브로스카이트 구조의 망간 산화물에서 많이 관찰되어온 초거대 자기 저항 현상은 임계점 (큐리온도) 부근에서 온도 변화에 의한 상자성-강자성 상전이와 동반한 전기 전도 기수 변화에 따른 급격한 저항 변화와 매우 밀접한 광계가 있다. 본 논문에서는 이러한 전기 저항-온도 거동을 모사하기 위해, 온도에 따른 상분율 변화 함수를 유효매질 이론(effective media theory)을 이용하여 모형식을 마련하엿다. 미 모형식은 실제 La0.7Ca0.3MnO3의 저항-온도 거동을 매우 정확하게 모사하였다.