• 한국세라믹학회지
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• 제34권6호
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• pp.652-658
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• 1997

The phase stability in the interface of Sr-doped LaMnO3(LSM)/Gd-doped CeO2(CGO) was examined in this study in order to check the feasibility of using LSM as the cathode material in a low-temperature SOFC(solid oxide fuel cell) using CGO as the electrolyte. For the purpose, CGO powders of Ce0.82Gd0.18O0.91 and two LSM powders having different compositions, La0.9Sr0.1MnO3(LSM10) and La0.5Sr0.5MnO3(LSM50), were synthesized using Pechini method. Then, specimens having the LSM/CGO interface were prepared, heat-treated at 130$0^{\circ}C$ for up to 3 days, and analyzed by XRD and STEM/EDX. Face-centered cubic CGO powders of less than 10 nm size were obtained by calcination of polymeric precursor formed in the process at 45$0^{\circ}C$. Higher calcination temperature of $700^{\circ}C$ was necessary for monoclinic LSM10 and cubic LSM50 powders. LSM powders were coarser than CGO and observed to be in the range of 50~100 nm. No trace of LSM-CGO interaction product was found in the XRD pattern. Also it was known from the concentration profile in the vicinity of the interface that interdiffusion was occurred over only a small penetration depth of ~100 nm order.

• 한국결정학회지
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• 제1권2호
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• pp.66-75
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• 1990

Pd-Te계의 상평형도를 시차열분석, X선회절분석, 전자현미분석, 반사현미경을 사용해 연구하였다. 본 계의 0-50 at.%Te 부분의 새로운 상관계가 정립되었다. 본 계에는 Pd17Te4, Pd20Te7, Pd8Te3, Pd7Te3, PdgTe4, Pd3Te2, PdTe, PdTe2 등 8개의 화합물이 존재하며 이중 Pd17Te4와 Pd7Te3는 처음 보고되는 신종 화합물이다. Pd17Te4는 등축정계이며 공간군 Fd3r에 속하며 단위포 크기 (a)는 12. 678(5)차이다. PdaTe.4와Pd7Te3의 X선회절분말자료는 사방정계의 단위포 a=12.843(3), b=15.126(3), c=11.304(2)A와 단사 정계의 단위포 a=7.444(1), b=13.918(2), c=8.873 (2)il, β=92.46(2)에 의해 각각 격자지수화가 가능하였다. 본계에 존재하는 합성 화합물의 일부 물리적, 광학적 자료를 새로 보고하였다.

• 한국세라믹학회지
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• 제39권11호
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• pp.1055-1062
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• 2002

정방정 지르코니아의 상안정성 및 저온열화기구를 고찰하기 위해 Y2O3 안정화 지르코니아에 3가 양이온 산화물을 첨가한 후 그 소결체의 기계적 물성, 라만 스펙트럼 및 격자상수 변화 등을 관찰하였다. 2Y-TZP에 $Zr^{4+}$ 보다 이온크기가 큰 3가 양이온($Sc^{3+},\;Yb^{3+},\;Y^{3+},\;Sm^{3+},\;Nd^{3+},\;La^{3+}$)들을 2 mol%까지 첨가하여 $1500{\circ}C$에서 1시간 소결후, X-ray 상분석 결과 $La^{3+}$의 경우에는 0.5 mol% 이상 첨가시 pyrochlore 상$(La_2Zr_2O_7)$의 형성으로 정방정상의 상안정성이 저하되었다. 첨가량이 증가할수록 $Zr6{4+}$과 이온크기가 거의 비슷한 $Sc^{3+}$를 첨가한 경우에는 정방정상만 관찰되었으나 $Yb^{3+},\;Y^{3+},\;Sm^{3+},\;Nd^{3+}$를 첨가한 경우에는 입방정상이 형성되었다. 양이온 크기가 커질수록 c/a비는 증가하였으나 $220{\circ}C$에서 500시간까지 열처리후 상분석 결과 단사정량은 감소하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.125.2-125.2
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• 2015

The evolution of oxidation states of vanadium is monitored with ambient pressure X-ray photoemission spectroscopy. As the pressure of oxygen gas and surface temperature change, the formations of various oxidation states of vanadium are observed on the surface. Under 100mTorr of the oxygen gas pressure and 523K of sample temperature, VO2 and V2O5 are formed on the surface. The temperature-dependent resistance measurement on grown sample shows a clear metal-insulator transition near 350K. In addition, the measurement of Raman spectroscopy displays the structural change from monoclinic to rutile structures across the phase transition temperature.

• 한국재료학회지
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• 제25권9호
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• pp.492-496
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• 2015

Hydroxyapatite (HA), which is an important calcium phosphate mineral, has been applied in orthopedics, dentistry, and many other fields depending upon its morphology. HA can be synthesized with different morphologies through controlling the synthesis method and several parameters. Here, we synthesize various morphologies of HA using two simple methods: hydrothermal combustion and solution combustion. The phase purity of the synthesized HA is confirmed using X-ray diffractometry. It demonstrates that pure phased hydroxyapatite can be synthesized using both methods. The morphology of the synthesized powder is examined using scanning electron microscopy. The effects of pH and temperature on the final powder are also investigated. At $140^{\circ}C$, using the hydrothermal method, nano-micro HA rods with a hexagonal crystal structure can be synthesized, whereas using solution combustion method at $600^{\circ}C$, a dense cubic morphology can be synthesized, which exhibits monoclinic crystal structures.

• Bulletin of the Korean Chemical Society
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• 제32권9호
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• pp.3395-3399
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• 2011

Copper oxide thin films were synthesized by reactive radio frequency magnetron sputtering at different oxygen gas ratios. The chemical and physical properties of the thin films were investigated by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD). XPS results revealed that the dominant oxidation states of Cu were $Cu^0$ and $Cu^+$ at 0% oxygen ratio. When the oxygen ratios increased above 5%, Cu was oxidized as CuO as detected by X-ray induced Auger electron spectroscopy and the $Cu(OH)_2$ phase was confirmed independent of the oxygen ratio. The valence band maxima were $1.19{\pm}0.09$ eV and an increase in the density of states was confirmed after formation of CuO. The thickness and roughness of copper oxide thin films decreased with increasing oxygen ratio. The crystallinity of the copper oxide films changed from cubic Cu through cubic $Cu_2O$ to monoclinic CuO with mean crystallite sizes of 8.8 nm (Cu) and 16.9 nm (CuO) at the 10% oxygen ratio level.

• 한국세라믹학회지
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• 제30권6호
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• pp.449-456
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• 1993

Sintering behaviour of zirconia powders prepared by different processing treatment was discussed. About >99% densities of theoretical were obtaiend on sintering at 140$0^{\circ}C$ for 2h in case of 300MPa uniaxially cold-pressed compact. But the lower densities were obtained on sintering above this temperature due to abnormal grain growth enabling the tetragonal to monoclinic phase transformation during cooling resulted in microcracks. All kinds of different dried powders exhibited nearly the same shrinkage behaviour with end-point shrinkage between 19 and 20%, and had maximum shrinkage rate (0.99~1.27%/min) around 120$0^{\circ}C$. During whole sintering process densification was mainly governed by grain growth and rearrangement of agglomerates. Heterogeneous abnormal grain growth and abrupt decrease in shrinkage were observed when continuous interagglomerate pore collapsed into isolated pores.

• 한국결정성장학회지
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• 제13권6호
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• pp.267-271
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• 2003

In this work, chemical solution derived Ca-doped zirconia fiber has been prepared by using calcium- and zirconium-naphthenate. Fibrous $ZrO_2$-CaO was drawn from a sticky mixture. Dried gel fibers were finally annealed at $1000^{\circ}C$ for 1 h in argon. 91 mol%$ZrO_2$-9 mol%CaO fiber consisted of tetragonal, monoclinic and $CaZrO_3$ phases after annealing at $1000^{\circ}C$. On the other hand, samples annealed at $500^{\circ}C$ consisted of almost tetragonal single phase. Homogeneous fibers surface at $500^{\circ}C$ became rougher after $1000^{\circ}C$-annealing. The sample annealed at $1000^{\circ}C$ with relatively rough surface structure showed a high Calcium phocphate forming ability.

• 한국재료학회지
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• 제25권4호
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• pp.171-176
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• 2015

We present the detection characteristics of nitrogen monoxide(NO) gas using p-type copper oxide(CuO) thin film gas sensors. The CuO thin films were fabricated on glass substrates by a sol-gel spin coating method using copper acetate hydrate and diethanolamine as precursors. Structural characterizations revealed that we prepared the pure CuO thin films having a monoclinic crystalline structure without any obvious formation of secondary phase. It was found from the NO gas sensing measurements that the p-type CuO thin film gas sensors exhibited a maximum sensitivity to NO gas in dry air at an operating temperature as low as $100^{\circ}C$. Additionally, these CuO thin film gas sensors were found to show reversible and reliable electrical response to NO gas in a range of operating temperatures from $60^{\circ}C$ to $200^{\circ}C$. It is supposed from these results that the p-type oxide semiconductor CuO thin film could have significant potential for use in future gas sensors and other oxide electronics applications using oxide p-n heterojunction structures.

• 한국재료학회지
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• 제13권4호
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• pp.219-223
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• 2003

Zirconia gels dispersed with fine Au particles have been prepared by the sol-gel method. Starting solution with (OC$Zr_4$$H_{ 9}$)$_4$, $C_4$ $H_{9}$ OH, $H_2$O,$ HNO_3$, $HAuC1_4$ was used to prepare gels in several molar ratio. After hydrolysis, viscosity of solutions as 4∼5 cP and gelling time of sols were spent about 9 days. As the heat-treatment temperature was increased,$ ZrO_2$ had the phase transition from tetragonal to monoclinic at $750^{\circ}C$. Heat-treatments of the gel have performed at 500, 700, 750, 800, 1000 and $1100^{\circ}C$ for 3 hrs, respectively. We have investigated TG-DTA, X-ray diffraction patterns, SEM and EDS. The size of Au fine particles dispersed in the heat-treatmented gel was about 0.15∼0.23 $\mu\textrm{m}$ and the shape was most sphericity.