• 한국자기학회:학술대회 개요집
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• 한국자기학회 2011년도 자성 및 자성재료 국제학술대회
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• pp.155-155
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• 2011

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2000년도 춘계연구발표회 논문개요집
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• pp.84-85
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• 2000

• 대한화학회지
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• 제55권4호
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• pp.697-702
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• 2011

새로운 층상구조인 페로브스카이트 망가나이트 $La_{0.5}Sr_{1.5}Mn_{0.5}Cr_{0.5-x}Fe_xO_4$ (x=0.15, 0.3) 를 세라믹 방법에 의해 합성하였다. 분말 X-선 측정을 통하여 I4/mmm 의 정방정계 단위세포를 확인하였다. 전기전도도 측정을 통하여 부도체의 특성을 확인하였으며 전기전도도는 3D 홉핑 메커니즘에 의해 나타난다. 자기적 특성은 모두 반강자성의 특성을 보인다.

• 한국재료학회지
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• 제18권4호
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• pp.175-180
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• 2008

In this study, the thermoelectric power and resistivity of the perovskite manganite $La_{0.75}Ba_{0.25}MnO_3$ were investigated in the temperature range 300K-1200K. The electrical resistivity and thermoelectric power indicate a transport mechanism dominated by adiabatic small-polaron hopping. The power factor increases from $2{\times}10^{-6}W/mK^2$ to $1{\times}10^{-5}W/mK^2$ as to the temperature increases from 400K to 1200K, which indicates that the compound is highly feasible as a thermoelectric material at high temperatures.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 추계학술발표대회
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• pp.33.1-33.1
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• 2011

Strontium doped lanthanum manganite (LSM) with perovskite structure for SOFC cathode material shows high electrical conductivity and good chemical stability, whereas the electrical conductivity at intermediate temperature below $800^{\circ}C$ is not sufficient due to low oxygen ion conductivity. The approach to improve electrical conductivity is to make more oxygen vacancies by substituting alkaline earths (such as Ca, Sr and Ba) for La and/or a transition metal (such as Fe, Co and Cu) for Mn. Among various cathode materials, $LaSrMnCuO_3$ has recently been suggested as the potential cathode materials for solid oxide fuel cells (SOFCs). As for the Cu doping at the B-site, it has been reported that the valence change of Mn ions is occurred by substituting Cu ions and it leads to formation of oxygen vacancies. The electrical conductivity is also affected by doping element at the A-site and the co-doping effect between A-site and B-site should be described. In this study, the $La_{1-x}Sr_xMn_{0.8}Cu_{0.2}O_{3{\pm}{\delta}}$ ($0{\leq}x{\leq}0.4$) systems were synthesized by a combined EDTA-citrate complexing process. The crystal structure, morphology, thermal expansion and electrical conductivity with different Sr contents were studied and their co-doping effects were also investigated.

• 한국군사과학기술학회지
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• 제20권4호
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• pp.491-496
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• 2017

The hydrogen($H_2$) is promising energy carrier of renewable energy in the microgrid system such as small village and military base due to its high energy density, pure emission and convenient transportation. $H_2$ can be generated by photocatalytic water splitting, gasification of biomass and water electrolysis driven by solar cell or wind turbine. Solid oxide electrolysis cells(SOECs) are the most efficient way to mass production due to high operating temperature improving the electrode kinetics and reducing the electrolyte resistance. The SOECs are consist of nickel-yttria stabilized zirconia(NiO-YSZ) fuel electrode / YSZ electrolyte / lanthanum strontium manganite-YSZ(LSM-YSZ) air electrode due to similarity to Solid Oxide Fuel Cells(SOFCs). The Ni-YSZ most widely used fuel electrode shows several problems at SOEC mode such as degradation of the fuel electrode because of Ni particle's redox reaction and agglomeration. Therefore Ni-YSZ need to be replaced to an alternative fuel electrode material. In this study, We studied on the Double perovskite $PrBrMnO_{5+{\delta}}$(PBMO) due to its high electric conductivity, catalytic activity and electrochemical stability. PBMO was impregnated into the scaffold electrolyte $La_{0.8}Sr_{0.2}Ga_{0.85}Mg_{0.15}O_{3-{\delta}}$(LSGM) to be synthesized at low temperature for avoiding secondary phase generated when it exposed to high temperature. The Half cell test was conducted at SOECs and SOFCs modes.

• 한국자기학회지
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• 제10권4호
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• pp.149-153
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• 2000

변하는 자기장을 단결정 및 다결정 망간 산화물 La$_{0.7}$Ca$_{0.3}$MnO$_3$에 인가하였을 때 자기 엔트로피가 크게 변하는(거대 자기 엔트로피 변화)현상이 관측되었다. 이 거대 자기 엔트로피 변화는 Curie온도에서 유사 1차상전이에 의한 자화값의 급격한 변화에 의한 것으로 추측된다. 이 거대 자기 엔트로피 변화와 망간 산화물 Curie 온도의 100 K＜T＜400 K 내의 조절 용이성은 상온을 포함한 넓은 온도에서 망간 산화물을 이용한 자기 냉각 기관의 개발 가능성을 제시하고 있다. 있다.

• Journal of Magnetics
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• 제19권3호
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• pp.221-226
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• 2014

Significantly enhanced low-field magnetoresistance (LFMR) and maximum dMR/dH {$(dMR/dH)_{max}$} values were successfully achieved from $La_{0.7}Sr_{0.3}MnO_3$(LSMO)-manganese oxide composite samples prepared by liquid phase sintering, compared with those of the same composites prepared by solid state reaction. For this study, pure LSMO and LSMO-manganese oxide composites with various nominal compositions of (1-x)LSMO-$xMn_2O_3$ (x = 0.1, 0.2, 0.3, 0.4, and 0.8) were sintered at $1450^{\circ}C$, above the eutectic temperature of $1430^{\circ}C$, for 1 h in air. The highest LFMR value of 1.28% with the highest $(dMR/dH)_{max}$ value of 21.1% $kOe^{-1}$ was obtained from the composite sample with x = 0.3 at 290 K in 500 Oe. This enhancement of LFMR and $(dMR/dH)_{max}$ values is ascribed to efficient suppression of magnetic disorder at the LSMO grain boundary, by forming a characteristic LSMO-manganese eutectic structure.

• Journal of Magnetics
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• 제18권4호
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• pp.386-390
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• 2013

This paper studies the effects of A-site substitution by barium on the magnetic and magnetocaloric properties of $Pr_{0.5}Sr_{0.5-x}Ba_{x}MnO_{3}$ (x = 0, 0.04, 0.08 and 0.1). The tetragonal crystal structures of the samples are confirmed by room temperature X-ray diffraction. The dependence of the Curie temperature ($T_C$) and the magnetic entropy change (${\Delta}S_M$) on the Ba doping content has been investigated. The samples of all doping contents undergo the second order phase transition. As the concentration of Ba increased, the maximum entropy change ($|{\Delta}S_M|_{max}$) increased gradually, from 1.15 J $kg^{-1}$ $K^{-1}$ (x = 0) to 1.36 J $kg^{-1}$ $K^{-1}$ (x = 0.1), in a magnetic field change of 1.5 T. The measured value of $T_C$ is 265 K, 275 K, 260 K and 250 K for x = 0, 0.04, 0.08 and 0.1, respectively. If combining these samples for magnetic refrigeration, the temperature range of ~220 K and 290 K, where |${\Delta}S_M$|max is stable at ~1.27 J $kg^{-1}$ $K^{-1}$ and RCP = 88.9 $J{\cdot}kg^{-1}$ for ${\Delta}H$ = 1.5 T. $Pr_{0.5}Sr_{0.5-x}Ba_{x}MnO_{3}$ compounds, are expected to be suitable for magnetic-refrigeration application due to these magnetic properties.

• Journal of Magnetics
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• 제18권1호
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• pp.34-38
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• 2013

This paper studies the effects of the Mn-site substitution by nickel on the magnetic properties and the magnetocaloric properties of $La_{0.7}Ca_{0.3}Mn_{1-x}Ni_xO_3$ (x = 0, 0.05 and 0.1). The orthorhombic crystal structures of the samples are confirmed by the room temperature X-ray diffraction. The dependence of the Curie temperature ($T_C$) and the magnetic entropy change (${\Delta}S_M$) on the Ni doping content was investigated. The samples with x = 0 had the first order phase transition, while the samples with x = 0.05 and 0.1 had the second order phase transition. As the concentration of Ni increased, the maximum entropy change (${\mid}{\Delta}S_M{\mid}_{max}$) decreased gradually, from 2.78 $J{\cdot}kg^{-1}{\cdot}K^{-1}$ (x = 0) to 1.02 $J{\cdot}kg^{-1}{\cdot}K^{-1}$ (x = 0.1), in a magnetic field change of 15 kOe. The measured value of $T_C$ was 185 K, 150 K and 145 K for x = 0, 0.05 and 0.1, respectively. The phase transition temperatures became wider as x increased. It indicates that the Mn-site substitution by Ni may be used to tailor the Curie temperature in $La_{0.7}Ca_{0.3}Mn_{1-x}Ni_xO_3$.