• 한국재료학회지
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• 제7권3호
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• pp.196-202
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• 1997

PLT 박막의 증착방법으로 ECR PECVD법을 이용한 경우 $440~500^{\circ}C$의 비교적 낮은 온도에서 순수한 perovskite구조를 가진$(Pb,La)TiO_{3}$박막을 성공적으로 제조하였다. 기판온도 증가에 따라 반응기체 및 산화물(특히 Pb oxkde)의 휘발성이 증대되어 증착속도가 감소하고 (Pb oxide)의 휘발성이 증대되어 증착속도가 감소하고 (Pb+La)/Ti조성비가 감소하였다. $460~480^{\circ}C$의 온도범위에서 증착한 PLT 박막이 화학양론비를 가장 잘 만족하였으며 이때 높은 유전상수와 가장 우수한 누설전류 특성을 나타내었다. $La(DPM)_{3}$ 유입량 증가에 따라 $(Pb, La)TiO_{3}$ 박막의 La 조성이 거의 직선적으로 비례하여 증가하였는데 La/Ti비가 3.0%에서 9.5%까지 증가함에 따라 PLT 박막의 유전 상수는 360부터 650까지 증가하였고 100kV/cm 전기장하에서의 누설전류도 $4{\times}10^{-5}$에서 $4{\times}10_{-8}A/cm^2$로 향상되었다.

• 한국세라믹학회지
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• 제53권5호
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• pp.489-493
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• 2016

Scandia ($Sc2O_3$)-stabilized zirconia (ScSZ) electrolyte-supported symmetrical solid oxide electrolyzer cells (SOECs), in which lanthanum strontium cobalt ferrite (LSCF)-gadolinia ($Gd_2O_3$)-doped ceria (GDC) composite materials are used as both the cathode and anode, were fabricated and their high temperature steam electrolysis (HTSE) performance was investigated. Current density-voltage curves were obtained for cells operated in 10% $H_2O$/90% Ar at 750, 800, and $850^{\circ}C$. It was possible to determine the ohmic, cathodic, and anodic contributions to the total overpotential using the three-electrode technique. The HTSE performance was significantly improved in the symmetrical cell with LSCF-GDC electrodes compared to the cell consisting of an Ni-YSZ cathode and LSCF-GDC anode. It was found that the overpotential due to the LSCF-GDC cathode largely decreased and, at a given current density, the total cell voltage decreased, which resulted in the enhanced hydrogen production rate in the symmetrical cell.

• 한국세라믹학회지
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• 제53권5호
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• pp.500-505
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• 2016

Scandia-stabilized zirconia co-doped with $CeO_2$ is a promising electrolyte for intermediate temperature SOFC, but still shows rapid degradation during a long-term operation. In this study, $CeO_2$ (1 mol%) as a stabilizer is partially substituted with lanthanum oxides ($M_2O_3$, M=Yb, Gd, Sm) to stabilize a cubic phase and thus durability in reducing atmosphere. 0.5M0.5Ce10ScSZ electrolytes were prepared by solid state reaction and sintered at $1450^{\circ}C$ for 10 h to produce dense ceramic specimens. With addition of the lanthanum oxide, 0.5M0.5Ce10ScSZ showed lower degradation rates than 1Ce10ScSZ. Since $Gd_2O_3$ showed the highest ionic conductivity among the co-dopants, an electrolyte-supported cell with 0.5Gd0.5Ce10ScSZ was prepared to compare its long-term performance with that of 1Ce10ScSZ-based cell. Maximum power density of 0.5Gd0.5Ce10ScSZ-based cell was degraded by about 2.3% after 250 h, which was much lower than 1Ce10ScSZ-based cell (4.2%).

• Journal of Electrochemical Science and Technology
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• 제11권4호
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• pp.336-345
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• 2020

Nickel-doped lanthanum cobalt oxide (LaCo_1-xNi_xO_3-δ, LCN) was investigated as an alternative anode material for solid oxide fuel cells. To improve its catalytic activity for steam methane reforming (SMR) reaction, Ni²⁺ was substituted into Co³⁺ lattice in LaCoO₃. LCN anode, synthesized using the Pechini method, reacts with yttria-stabilized zirconia (YSZ) electrolyte at high temperatures to form an electrochemically inactive phase such as La₂Zr₂O₇. To minimize the interlayer by-products, the LCN was coated via a double-tape casting method on the Ni/YSZ anode as a catalytic functional layer. By increasing the Ni doping amount, oxygen vacancies in the LCN increased and the cell performance improved. CH₄ fuel decomposed to H₂ and CO via SMR reaction in the LCN functional layer. Hence, the LCN-coated Ni/YSZ anode exhibited better cell performance than the Ni/YSZ anode under H₂ and CH₄ fuels. LCN with 12 mol% of Ni (LCN12)-modified Ni/YSZ anode showed excellent long-term stability under H₂ and CH₄ conditions.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1440-1441
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• 2011

Apatite-lanthanum silicate has attracted considerable interest in recent years due to its high oxide ion conductivity, In this paper, Bi-doped samples $La_8Bi_2(SiO_4)_6O_3$ were prepared by conventional solid-state method and the influences of Bi-dopant content on calcining temperature were reported. The Samples were characterized by X-ray diffraction (XRD) and scanning electron micrograph (SEM) and impedance analysis.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.85.2-85.2
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• 2011

현재 중온의 고체산화물 연료전지를 위해 다양한 전해질에 대한 연구되었으며 1994년 Ishihara et al.에서 1074K의 온도에서 높은 이온전도도를 갖는 페록스카이 구조를 갖는 LSGM 물질을 발표하였다. Sr과 Mg을 도핑한 Lanthanum gallate는 이온전도도가 1073K에서 0.14S/cm로 YSZ의 5배로 높은 이온전도도를 갖고 있으며 산화환경에서부터 환원환경에서 화학적으로 안정한 특성을 갖고 있다. 또한 LSGM 전해질은 넓은 산소 농도범위에서 안정적인 특성을 갖는 장점을 갖고 있다. 그러나 LSGM은 가장 널리 사용되는 연료극의 Ni 촉매와 고온 소결시 상호확산현상에 의한 2차상을 생성시켜 성능 저감의 원인으로 그 해결방안이 요원한 실정이다. 이에 본 논문에서는 LSGM 전해질에 LSGM scaffold를 형성하고 형성된 scaffold에 연료극 촉매 solution을 infiltration 시켜 저온에서 anode를 형성하여 그 성능을 연구하였다.

• The Korean Journal of Ceramics
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• 제6권4호
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• pp.364-369
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• 2000

Silicon nitride with adding La$_2$O$_3$ was sintered by gas pressure sintering (GPS) technique at $1950^{\circ}C$, in $N_2$ gas at 3 MPa, for 2h. Mechanical properties such as hardness, flexural strength, and fracture toughness were determined as a function of the GPS holding time and the contents of La$_2$O$_3$ in silicon nitride. Also machinability of silicon nitride ball with various GPS holding time and amount of La$_2$O$_3$ was evaluated by magnetic fluid grinding (MFG) method. In this study it was found that machinability was influenced significantly with La$_2$O$_3$ contents. However, the different GPS holding time did not affect the machinability very much.

• Nuclear Engineering and Technology
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• 제48권4호
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• pp.997-1001
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• 2016

Conductive ceramics are being developed to replace current Pt anodes in the electrolytic reduction of spent oxide fuels in pyroprocessing. While several conductive ceramics have shown promising electrochemical properties in small-scale experiments, their long-term stabilities have not yet been investigated. In this study, the chemical stability of conductive $La_{0.33}Sr_{0.67}MnO_3$ in $LiCl-Li_2O$ molten salt at $650^{\circ}C$ was investigated to examine its feasibility as an anode material. Dissolution of Sr at the anode surface led to structural collapse, thereby indicating that the lifetime of the $La_{0.33}Sr_{0.67}MnO_3$ anode is limited. The dissolution rate of Sr is likely to be influenced by the local environment around Sr in the perovskite framework.

• Journal of Electrochemical Science and Technology
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• 제2권1호
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• pp.39-44
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• 2011

Sub-micrometer $La_{0.8}Ca_{0.2}CrO_3$ powders for ceramic interconnects of solid oxide fuel cells were synthesized by the aqueous combustion process. The materials were prepared from the precursor solutions with different glycine (fuel)-to-nitrate (oxidant) ratios (${\phi}$). Single-phase $La_{0.8}Ca_{0.2}CrO_3$ powders with a perovskite structure were obtained after combustion when ${\phi}$ was equal to or larger than 0.480. Especially, the stoichiometric precursor with ${\phi}$ = 0.555 yielded the spherical $La_{0.8}Ca_{0.2}CrO_3$ particles with 150-250 nm diameters after calcination at $1000^{\circ}C$. When compared with the powders synthesized by the solid-state reaction, the combustion-derived, fine powders exhibited improved sinterability, leading to near-full densification at $1400^{\circ}C$ in oxidizing atmospheres. Moreover, a small quantity of glass additives was used to reduce the sintering temperature, and considerable densification was indeed achieved at temperatures as low as $1100^{\circ}C$.

• 자원리싸이클링
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• 제29권3호
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• pp.61-74
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• 2020

본 연구에서는 폐형광등 처리 공정의 경제성 확보를 위하여 수행되었으며, 폐형광등 유리의 글래스비드용 원료로서의 사용 가능성, 폐형광체 분말로부터 희토류의 침출, 희토류 침출액으로부터 희토류의 용매추출 가능성 등을 검토하였다. 폐형광체는 산화이트륨 28.9%, 산화세륨이 3.46%, 산화유로퓸 1.95%, 산화터븀 1.76%, 산화란탄 1.43% 순으로 함유되어 있어 회수 및 정제 시 경제성이 충분할 것으로 판단되었다. 폐형광등 유리를 사용하여 글래스비드를 시험 생산 한 결과 그 생산수율과 품질이 우수하여 폐형광등 유리를 글래스비드용 원료로 사용할 수 있을 것으로 판단되었다. 소다배소한 폐형광체를 수침출하면 알루미늄과 규소성분 및 잔류 탄산나트륨 등이 용해하며, 이 수용액에 탄산가스를 불어 넣어 pH를 7 정도로 떨어뜨리면 NaAl₂(CO₃)(OH)₂와 SiO₂ 등이 침전하였다. 자이렌을 희석제로 사용하는 cyanex272-hydrochloric acid, cyanex272-sulfuric acid, D2EHPA-hydrochloric acid, D2EHPA-sulfuric acid, lonquest290-hydrochloric acid, lonquest290-sulfuric acid, p507-hydrochloric acid 조합의 용매추출에서 Y, Eu, Ce, La, Tb의 추출률이 100%에 가깝다. 그러나 동일 조건에서의 원소별 추출률의 차이, 즉 선택성은 16% 이하이다.