• 한국세라믹학회지
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• 제48권2호
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• pp.195-199
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• 2011

The effect of copper oxide on migration and interaction of protons in barium zirconate was investigated using density functional theory. One copper atom was substituted for a zirconium atom site, and a proton was added to a $3{\times}3{\times}3$ barium zirconate superstructure. An energy barrier of 0.89 eV for proton migration was the highest among several energy barriers. To investigate the interaction between multiple protons and a copper atom, two protons were added to the superstructure. Various proton positions were determined by the interaction between the two protons and the copper atom.

• 한국결정성장학회지
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• 제22권1호
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• pp.19-24
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• 2012

Barium zirconate는 화학적 안정성이 우수하고 고온에서의 프로톤 전도성이 뛰어나지만, 프로톤 전도도에 비해 전자전도도가 현저히 떨어진다. 따라서 본 연구에서는 높은 수소 분리 특성을 위해 다공성 지지체 상에 Pd-Barium zirconate를 얇고 치밀한 박막으로 제조하고자 하였고, dual sputtering법을 이용하여 성공적으로 증착하였다. X-선 회절 분석을 통해 증착된 $BaZr_{0.85}Y_{0.15}O_{3-{\delta}}$ 박막은 300 이상에서부터 $BaZrO_3$(Pm-3m) 결정상으로 결정화됨을 확인할 수 있었으며 표면과 단면에 대한 구조적 형상은 SEM과 TEM을 통해 관찰하였다. 관찰 결과 증착된 분리막은 치밀하였고 부채꼴의 주상으로 결정이 성장함을 확인할 수 있었다.

• 대한금속재료학회지
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• 제49권12호
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• pp.977-982
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• 2011

Migration and interaction of multi-protons in a zinc-doped barium zirconate (Zn-doped $BaZrO_3$) super cell were investigated using a density functional theory. O ions in the super cell form interconnected octahedrons with Zr or Zn ions positioned in their centers and Ba ions positioned among the eight octahedrons. When one proton was added to the super cell, the energy barrier of 0.80 eV for proton transfer from the first to second nearest O ion sites from the Zn ion reached its highest value. When two protons were added to the super cell, the two protons preferred the first nearest O ions from the Zn ion. The two protons were accommodated by pushing the neighboring Zn ion further away from the center of the octahedron. Energy barriers for proton transfer from the Zn-octahedron to the neighboring Zr-octahedron were spread in the range of 0.36 ~ 1.02 eV.

• 한국수소및신에너지학회논문집
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• 제23권6호
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• pp.670-677
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• 2012

Perovskite-type oxides such as doped barium zirconate ($BaZrO_3$) show high proton conductivity and chemical stability when they are exposed to hydrogen and water vapour containing atmospheres, thus it can be applicable to the hydrogen separation and the fuel cell electrolyte membranes. However the high temperature ($1700-1800^{\circ}C$) and long sintering times (24h) are generally required to prepare the fully densified $BaZrO_3$ pellets. These sintering conditions lead to the limitation of the grain size growth and the degradation of conductivity due to the acceleration of BaO evaporation at $1200^{\circ}C$. Here we demonstrate NiO-doped $BaZr_{0.85}Y_{0.15}O_{3-{\delta}}$ with lower calcination and sintering temperature, less experimental procedure and lower process cost than the conventional mixing method. The stoichiometry of $BaZr_{0.85}Y_{0.15}O_{3-{\delta}}$ was optimized by the control of excess amount of Ba (5mol%) to minimized BaO evaporation. We found that the crystal size of NiO-doped $BaZr_{0.85}Y_{0.15}O_{3-{\delta}}$ was increased with increase of calcination temperature from XRD analysis. NiO-doped $BaZr_{0.85}Y_{0.15}O_{3-{\delta}}$ powder was calcined at $1000^{\circ}C$ for 12h when its showed the highest conductivity of $3.3{\times}10^{-2}s/cm$.

• Bulletin of the Korean Chemical Society
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• 제23권8호
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• pp.1078-1084
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• 2002

The formation temperature for the perovskite lead zirconate titanate [Pb(Zr,Ti)O3, PZT] derived from sol-gel route was lowered by more than $100^{\circ}C$ with the addition of crystallographically suitable seed particles, such as barium titanat e (BT) or PZT. We investigated the effect of seeding on the crystallization of perovskite phase and in the microstructure of the sol-gel derived PZT powder by varying the concentration, size and chemical species of seed particles. The phase transition as a function of temperature was monitored by DTA, XRD, and Raman spectroscopy, and the interface between the seed particle and grown PZT layer was analyzed by SEM and high resolution TEM techniques. It was found that both the heterogeneous and homogeneous nucleation contributes competitively in the formation of perovskite PZT grains.

• 대한기계학회논문집B
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• 제36권9호
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• pp.931-935
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• 2012

본 연구에서는 저온형 연료전지와 고온형 연료전지의 작동 및 구성 요소 측면 단점들을 보완하기 위해 중온 영역에서 작동하는 박막 연료전지를 제작하였다. 박막 연료전지는 이트륨이 도핑된 바륨 지르코네이트(BYZ) 전해질과 백금 수소극/공기극으로 이루어져 있으며, 성능은 $350^{\circ}C$에서 측정하였다. 350nm의 두께를 가지는 백금 수소극은 다공성 기판 위에 스퍼터링 기법을 이용하여 증착하였다. BYZ전해질은 펄스레이저 기법을 이용하여 $1{\mu}m$ 증착하였고, 상부에 스퍼터링 기법을 이용하여 200nm의 두께를 가지는 백금 공기극을 증착하였다. 개회로 전압은 약 0.81V이었고, 최대 출력 성능은 11.9mW/$cm^2$이었다.

• 한국표면공학회지
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• 제34권5호
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• pp.481-485
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• 2001

We investigated the structural and electrical properties of the Ba ($Zr_{x}$ $T_{il-x}$ )$O_3$ (BZT thin films with a mole fraction of x=0.2 and thickness 150 nm for the application in MLCC (Multilayer Ceramic Capacitor). BZT films were prepared on $Pt/SiO_2$/Si substrate at various substrate temperatures by the RF-magnetron sputtering system. When the substrate temperature was above $500^{\circ}C$, we could obtain multi-crystalline BZT films oriented at (110), (111), and (200) directions. The crystallization of the film and high dielectric constant were observed with the increase of substrate temperature. Capacitance of the film deposited at high temperature is more sensitive to the applied voltage than that of the film deposited at low temperature. This paper reports surface morphology, dielectric constant, dissipation factor, and C-V characteristics for BZT films deposited at three different temperatures. The BZT film deposited at 40$0^{\circ}C$ shows stable electrical properties but a little small dielectric constant for MLCC application.

• 한국세라믹학회지
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• 제53권5호
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• pp.521-528
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• 2016

Kinetic Monte Carlo (KMC) and graph searches show that proton conduction limiting barriers and trajectories in $BaZr_{0.875}Y_{0.125}O_3$ are affected by the presence of other protons. At 1000 K, KMC limiting conduction barriers increase from 0.39 eV to 0.45 eV as the proton number is increased. The proton-proton radial distribution begins to rise at $2{\AA}$ and peaks at $4{\AA}$, which is half the distance expected, based on the proton concentration. Density functional theory (DFT) calculations find proton/proton distances of 2.60 and $2.16{\AA}$ in the lowest energy two-proton configurations. A simple average of the limiting barriers for 7-10 step periodic long range paths found via graph theory at 1100 K shows an increase in activation barrier from 0.32 eV to 0.37 eV when a proton is added. Both KMC and graph theory show that protons can affect each other's pathways and raise the overall conduction barriers.

• 한국수소및신에너지학회논문집
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• 제22권5호
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• pp.649-655
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• 2011

Methane direct cracking can be utilized to produce $CO_x$ and $NO_x$-free hydrogen for PEM fuel cells, oil refineries, ammonia and methanol production. We present the results of a systematic study of methane direct cracking using a mixed conducting oxide, Y-doped $BaZrO_3$ ($BaZr_{0.85}Y_{0.15}O_3$), membrane. In this paper, dense $BaZr_{0.85}Y_{0.15}O_3$ membrane with disk shape was successfully sintered at $1400^{\circ}C$ with a relative density of more 93% via addition of 1 wt% ZnO. The ($BaZr_{0.85}Y_{0.15}O_3$) membrane is covered with Pd as catalyst for methane decomposition with an DC magnetron sputtering method. Reaction temperature was $800^{\circ}C$ and high purity methane as reactant was employed to membrane side with 1.5 bar pressure. The $H_2$ produced by the reaction was transported through mixed conducting oxide membrane to the outer side. In addition, it was observed that the carbon, by-product, after methane direct cracking was deposited on the Pd/ZnO-$BaZr_{0.85}Y_{0.15}O_3$ membrane. The produced carbon has a shape of sphere and nanosheet, and a particle size of 80 to 100 nm.

• 한국세라믹학회지
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• 제52권5호
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• pp.320-324
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• 2015

Optimization of the fabrication process of NiO-yttrium doped barium zirconate (BZY) composite anode substrates using tape-casting for high performance thin-film protonic ceramic fuel cells (PCFCs) is investigated. The anode substrate is composed of a tens of microns-thick anode functional layer laminated over a porous anode substrate. The macro-pore structure of the anode support is induced by micron-scale polymethyl methacrylate (PMMA) pore formers. Thermal gravity analysis (TGA) and a dilatometer are used to determine the polymeric additive burn-out and sintering temperatures. Crystallinity and microstructure of the tape-cast NiO-BZY anode are analyzed after the sintering.