• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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• pp.121-121
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• 2003

NiO thin films are very attractive for use as an antiferromagnetic layer, p-type transparent conducting films, in electrochromic devices and functional sensor layer for chemical sensors, due to their excellent chemical stability, as well as optical, electrical and magnetic properties. In addition, (100)- and (111)-oriented NiO films can be used as buffer layers on which to deposit other oriented oxide films, such as c-axis-oriented perovskite-type ferromagnetic films and superconducting films, because of the similarity in symmetry of oxygen ion lattice and lattice constants between the NiO films and the oriented oxide films. Thus, controlling the crystallographic orientation and surface roughness of the NiO films for a buffer layer are very important.

• Korean Chemical Engineering Research
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• 제55권5호
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• pp.718-722
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• 2017

마이크로파 공정으로 제조된 순수한 $LaCoO_3$와 금속이온이 첨가된 $LaCoO_3$ 페롭스카이트 산화물에서 메틸오렌지의 광촉매 분해반응의 활성을 조사하였다. 순수한 $LaCoO_3$와 세슘 이온이 첨가된 $LaCoO_3$ 산화물들은 제조법과 무관하게 페롭스카이트 구조를 보여주었다. UV-Vis DRS 결과에 의하면 모든 촉매들은 가시광 영역에서 흡수스펙트럼을 나타내었다. 화학흡착된 산소종은 메틸오렌지의 광촉매 분해반응에서 중요한 역할을 하였으며, 화학흡착된 산소의 비율이 높을수록 더 높은 광촉매 활성을 보여주었다.

• 대한화학회지
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• 제37권2호
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• pp.255-258
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• 1993

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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• pp.82-82
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• 2008

• Bulletin of the Korean Chemical Society
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• 제32권8호
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• pp.2761-2764
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• 2011

A new Ruddlesden-Popper phase $NdSr_2MnCrO_7$ has been prepared by the standard ceramic method. The powder X-ray diffraction studies suggest that the phase crystallizes with tetragonal unit cell in the space group I4/mmm. The electrical transport properties show that the phase is an electrical insulator and the electrical conduction in the phase occurs by a 3D variable range hopping mechanism. The magnetic studies suggest that the ferromagnetic interactions are dominant.

• 대한환경공학회지
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• 제22권12호
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• pp.2255-2261
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• 2000

본 연구에서는 질소산화물 저감기술의 하나인 선태적 촉매 환원법(SCR)을 이용하여 실제 디젤엔진에서의 $NO_x$저감에 관한 실험을 수행하였다. 특히 선택적 촉매 환원법 중에서 금속산화물(metal oxide)과, 페롭스카이트(perovskite)형의 환원촉매를 사용하였으며 ${\gamma}-Al_2O_3$ 담체에 여러 가지 주촉매, 조촉매를 사용하여 배기가스 온도 범위 내에서 높은 $NO_x$제거효율을 가지고 있는 $LaCuMnO_x$을 선택하였다. $NO_x$ 제거를 위한 실험은 실제 디젤엔진에서 배출되는 배기가스를 이용하였으며 공간속도 $3,300h^{-1}$인 상태에서 촉매 반응기 통과전후의 $NO_x$의 변화량을 측정하였다. 그 결과 페롭스카이트 형태의 촉매가 활성화 온도범위가 우수함을 알 수 있었고 $LaCuMnO_x$의 경우에는 촉매 온도범위 $150{\sim}450^{\circ}C$하에서 $NO_x$의 제거효율이 전반적으로 우수하였다.

• 한국세라믹학회지
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• 제52권5호
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• pp.331-337
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• 2015

$LaBO_3$ (B = Cr, Mn, Fe, Co, and Ni) perovskites, the most common perovskite-type mixed ionic-electronic conductors (MIECs), are promising candidates for intermediate-temperature solid oxide fuel cell (IT-SOFC) cathodes. The catalytic activity on MIEC-based cathodes is closely related to the bulk ionic conductivity. Doping B-site cations with other metals may be one way to enhance the ionic conductivity, which would also be sensitively influenced by the chemical composition of the dopants. Here, using density functional theory (DFT) calculations, we quantitatively assess the activation energies of bulk oxide ion diffusion in $LaBO_3$ perovskites with a wide range of combinations of B-site cations by calculating the oxygen vacancy formation and migration energies. Our results show that bulk oxide ion diffusion dominantly depends on oxygen vacancy formation energy rather than on the migration energy. As a result, we suggest that the late transition metal-based perovskites have relatively low oxygen vacancy formation energies, and thereby exhibit low activation energy barriers. Our results will provide useful insight into the design of new cathode materials with better performance.

• 한국세라믹학회지
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• 제17권4호
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• pp.179-187
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• 1980

Perovskite-type oxide catalysts in the $\textrm{LaMnO}_3$ family were prepared by both freeze drying and precipitation technique, and their catalytic activities with respect to the oxidation of CO with $O_2$ were measured in the composite gases. Freeze drying is a new technique for the prevention of migration of the solutes during drying. Therefore, the corrugated cordierite monolith fabricated with the Ø 1mm stainless steel bar was directly impregnated with nitrate solutions containing the appropriate cations, freeze dried and calcined. Precipitation was done by using $\textrm{(NH_4)}_2\textrm{CO}_3$ but the precipitated catalysts gave lower catalytic than the freeze dried samples due to, in part, relatively high calcining temperature. In this study, freeze dried composition had high catalytic activity, and their apparent activation energy for oxidation of CO was calculated by the rate plots using the data where the percent conversion of CO was less than 20%.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2012년도 춘계학술발표대회
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• pp.70.1-70.1
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• 2012

In-situ X-ray photoelectron spectroscopy (XPS) and infrared (IR) spectroscopy studies of SOFC cathode materials will be discussed in this presentation. The mixed conducting perovskites (ABO3) containing rare and alkaline earth metals on the A-site and a transition metal on the B-site are commonly used as cathodes for solid oxide fuel cells (SOFC). However, the details of the oxygen reduction reaction are still not clearly understood. The information about the type of adsorbed oxygen species and their concentration is important for a mechanistic understanding of the oxygen incorporation into these cathode materials. XPS has been widely used for the analysis of adsorbed species and surface structure. However, the conventional XPS experiments have the severe drawback to operate at room temperature and with the sample under ultrahigh vacuum (UHV) conditions, which is far from the relevant conditions of SOFC operation. The disadvantages of conventional XPS can be overcome to a large extent with a "high pressure" XPS setup installed at the BESSY II synchrotron. It allows sample depth profiling over 2 nm without sputtering by variation of the excitation energy, and most importantly measurements under a residual gas pressure in the mbar range. It is also well known that the catalytic activity for the oxygen reduction is very sensitive to their electrical conductivity and oxygen nonstoichiometry. Although the electrical conductivity of perovskite oxides has been intensively studied as a function of temperature or oxygen partial pressure (Po2), in-situ measurements of the conductivity of these materials in contact with the electrolyte as a SOFC configuration have little been reported. In order to measure the in-plane conductivity of an electrode film on the electrolyte, a substrate with high resistance is required for excluding the leakage current of the substrate. It is also hardly possible to measure the conductivity of cracked thin film by electrical methods. In this study, we report the electrical conductivity of perovskite $La_{0.6}Sr_{0.4}CoO_{3-{\delta}}$ (LSC) thin films on yttria-stabilized zirconia (YSZ) electrolyte quantitatively obtained by in-situ IR spectroscopy. This method enables a reliable measurement of the electronic conductivity of the electrodes as part of the SOFC configuration regardless of leakage current to the substrate and cracks in the film.

• 센서학회지
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• 제10권3호
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• pp.173-179
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• 2001

현재 사용되어지는 반도체형 압력센서에는 압저항형과 용량형이 있다. 특히 반도체 마이크로 압력센서는 크기도 작고 신호처리회로를 동일칩 위에 집적화 할 수 있어 많은 관심을 모아왔다. 그러나 이러한 형태의 센서들은 제조공정이 복잡해서 생산성이 낮다. 기존의 센서들이 가지는 단점들을 극복하기 위해 새로운 형태의 FET형 압력센서(PSFET : pressure sensitive field effect transistor)를 제안하고 그 동작특성을 조사하였다. 압력 감지 물질은 PZT(Pb(Zr,Ti)$O_3$)를 사용하였다. RF 마그네트론 스퍼터링법을 사용하여 MOSFET의 게이트 절연막 위에 PZT 압전 박막을 증착하였다. PZT의 안정적 상태인 perovskite 구조를 형성하기 위하여 PbO 분위기에서 열처리하는 기법을 도입하였다. 제작된 PSFET의 감도는 0.38 mV/mmHg이다.