• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2001년도 춘계학술발표강연 및 논문개요집
• /
• pp.116-116
• /
• 2001

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2001년도 추계 학술발표강연 및 논문개요집
• /
• pp.182-182
• /
• 2001

• 대한환경공학회지
• /
• 제22권12호
• /
• pp.2263-2273
• /
• 2000

희분식 고온/고압 미분반응기를 이용하여 습식산화 반응시 대표적 난분해성 중간 산화물질로 알려진 아세트산을 산화반응 기질로 하여 여러 가지 담체 및 촉매의 조합에 대한 산화반응성을 실험하였다. 사용된 담체는 다공성 실리카($SiO_2$), 티타니아($TiO_2$), 지르코니아($ZrO_2$), $ZrSiO_4$, $ZrO_2(10wt%)/TiO_2$ 등이었으며 촉매활성성분온 크게 Ru, Mn, Ce의 세 가지로서 단독 혹은 조합사용(2성분계 및 3성분계)시의 산화활성에 대하여 조사하였다. 이를 통하여 일차척인 활성이 우수한 것으로 나타난 $Mn(2.8)-Ce(7.2wt%)/TiO_2$ 혹은 $Ru(0.5)-Mn(2.7)-Ce(6.8wt%)/TiO_2$ 기준촉매의 활성증진을 위하여 p-type 반도체 물질(CoO, SnO 및 $Ag_2O$)를 첨가제로 소량 사용함으로써 이에 따른 습식산화 반응 상대 활성실험을 수행하였다. 우선, $Mn-Ce/TiO_2$ 기준촉매에 있어서, p-type 반도체 물질(CO, Sn Ag)을 첨가한 경우, 모두 활성증진효과를 보이며 크기 정도는 Co> Ag >Sn순이었다. 특히, $Mn(2.7)-Ce(6.8)-Co(0.5wt%) /TiO_2$에 있어서는 약 2.6배의 높은 활성상승이 나타났다. 이의 가시적인 주원인은 표면적 증가 및 시너지 효과에 기인하는 것으로 판단되었다. $Ru-Mn-Ce/TiO_2$ 기준 촉매에 있어서는 $Ru(O.5)-Mn(2.4)-Ce(6.1)-Co(1.0wt%)/TiO_2$에서만 활성증진효과를 보였으며 그 이외의 다른 경우에 있어서는 표면적 및 활성감소가 일어났다.

• 한국재료학회지
• /
• 제26권4호
• /
• pp.212-215
• /
• 2016

In this paper, cerium doped lutetium pyrosilicate (LPS) powders with cerium content (0.05 and 0.07 mol%) were prepared by sol-gel process. The formation of lutetium pyrosilicate (LPS) phase was confirmed by XRD analysis for the powders heated at $1,200^{\circ}C$; in these powders, a single phase of $Lu_2Si_2O_7$ (LPS) was observed. Cerium doped lutetium pyrosilicate (LPS) powder was agglomerated and constituted of small spherical particles with diameters of about 300 nm. The photoluminescence spectra of the $Lu_2Si_2O_7:Ce^{3+}$ powders showed the characteristic of excitation and there was an emission spectrum for $Ce^{3+}$ in the host of $Lu_2Si_2O_7$. The emission spectrum shows a broad band in the range of 350-525 nm; the broad wavelength on the right side of the spectra should be ascribed to the same 5d-4f transitions of $Ce^{3+}$, as in the case of cerium doped $Lu_2Si_2O_7$ single crystals.

• The Korean Journal of Ceramics
• /
• 제3권4호
• /
• pp.245-248
• /
• 1997

Photoluminescence (PL) and cathodoluminescence (CL) characteristics of Ce-activated $Y_{2-x}Ce_xSiO_5$ have been investigated as functions of Ce concentration and firing condition. According to the X-ray, PL and CL results, $Y_2SiO_5$ is found to have two phases depending on the firing temperature. For the specimen fired above 127$0^{\circ}C$, the emission band peaked at 395nm with a shoulder at 424 nm under ultraviolet (u.v.) and cathode-ray (c.r.) excitation. However, for the specimen fired below 120$0^{\circ}C$ in air the peak was observed at 424 nm and it shifted to longer wavelength with reduction level. The reduced specimen for x=0.02 showed the brightest emission under u.v. excitation whereas under c.r. excitation the brightest emission was observed for the reduced specimen for x=0.06.

• 한국전기전자재료학회논문지
• /
• 제14권9호
• /
• pp.695-699
• /
• 2001

Cerium dioxide (CeO$_2$) was used as the intermediate layer between the ferroelectric thin film and Si substrate in a metal-ferroelectric-semiconductor field effect transistor (MFSFET), to improve the interface property by preventing the interdiffusion of the ferroelectric material and the Si substrate. In this study, CeO$_2$ thin films were etched with a CF$_4$/Ar gas combination in inductively coupled plasma (ICP). The maximum etch rate of CeO$_2$ thin films was 270$\AA$/min under CF$_4$/(CF$_4$+Ar) of 0.2, 600 W/-200V, 15 mTorr, and $25^{\circ}C$. The selectivities of CeO$_2$ to PR and SBT were 0.21, 0.25, respectively. The surface reaction in the etching of CeO$_2$ thin films was investigated with x-ray photoelectron spectroscopy (XPS). There is a chemical reaction between Ce and F. Compounds such as Ce-F$_{x}$ remains on the surface of CeO$_2$ thin films. Those products can be removed by Ar ion bombardment. The results of secondary ion mass spectrometry (SIMS) were consistent with those of XPS. Scanning electron microscopy (SEM) was used to examine etched profiles of CeO$_2$ thin films. The etch profile of over-etched CeO$_2$ films with the 0.5${\mu}{\textrm}{m}$ line was approximately 65$^{\circ}$.>.

• 한국전기전자재료학회논문지
• /
• 제16권5호
• /
• pp.361-364
• /
• 2003

It was investigated that the structural and electrical Properties of Ce-doped Ba(Zr$_{x}$Ti$_{1-x}$ )O$_3$ (BCZT) thin films with a mole fraction of x=0.2 and a thickness about 100 nm. BCZT films were prepared on Pt/Ti/SiO$_2$/Si substrate by a RF magnetron sputtering system. We have measured the thickness profile with Ar/O$_2$ ratio and the surface roughness. It was observed that the oxygen gas, which introduced during the film deposition, have an influence on the roughness of the film and the film roughness was reduced by annealing from 2.33 nm to 2.02 nm (RMS at 500 $^{\circ}C$, Ar:6 sccm, $O_2$:6 sccm). It was found that annealing procedure after top electrode deposit can reduce the dissipation factor.

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 1997년도 한국재료학회 춘계학술발표회
• /
• pp.102-102
• /
• 1997

• 한국세라믹학회:학술대회논문집
• /
• 한국세라믹학회 2003년도 추계총회 및 연구발표회 초록집
• /
• pp.172.1-172
• /
• 2003

• 한국재료학회지
• /
• 제21권5호
• /
• pp.250-254
• /
• 2011

We have synthesized bluish-green, highly-efficient $BaSi_2O_2N_2:Eu^{2+}$ and $(Ba,Sr)Si_2O_2N_2:Eu^{2+}$ phosphors through a conventional solid state reaction method using metal carbonate, $Si_3N_4$, and $Eu_2O_3$ as raw materials. The X-ray diffraction (XRD) pattern of these phosphors revealed that a $BaSi_2O_2N_2$ single phase was obtained. The excitation and emission spectra showed typical broadband excitation and emission resulting from the 5d to 4f transition of $Eu^{2+}$. These phosphors absorb blue light at around 450 nm and emit bluish-green luminescence, with a peak wavelength at around 495 nm. From the results of an experiment involving Eu concentration quenching, the relative PL intensity was reduced dramatically for Eu = 0.033. A small substitution of Sr in place of Ba increased the relative emission intensity of the phosphor. We prepared several white LEDs through a combination of $BaSi_2O_2N_2:Eu^{2+}$, YAG:$Ce^{3+}$, and silicone resin with a blue InGaN-based LED. In the case of only the YAG:$Ce^{3+}$-converted LED, the color rendering index was 73.4 and the efficiency was 127 lm/W. In contrast, in the YAG:$Ce^{3+}$ and $BaSi_2O_2N_2:Eu^{2+}$-converted LED, two distinct emission bands from InGaN (450 nm) and the two phosphors (475-750 nm) are observed, and combine to give a spectrum that appears white to the naked eye. The range of the color rendering index and the efficiency were 79.7-81.2 and 117-128 lm/W, respectively. The increased values of the color rendering index indicate that the two phosphor-converted LEDs have improved bluish-green emission compared to the YAG:Ce-converted LED. As such, the $BaSi_2O_2N_2:Eu^{2+}$ phosphor is applicable to white high-rendered LEDs for solid state lighting.