• Bulletin of the Korean Chemical Society
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• 제30권12호
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• pp.3021-3024
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• 2009

$Zn_2Ti_{1-x}Fe_xO_4\;(0\;{\leq}\;x\;{\leq}\;0.7)$ photocatalysts were synthesized by polymerized complex (PC) method and investigated for its physico-chemical as well as optical properties. $Zn_2Ti_{1-x}Fe_xO_4$ can absorb not only UV light but also visible light region due to doping of Fe in the Ti site of $Zn_2TiO_4$ lattice because of the band transition from Fe 3d to the Fe 3d + Ti3d hybrid orbital. The photocatalytic activity of Fe doped $Zn_2TiO_4$ samples for hydrogen production under UV light irradiation decreased with an increase in Fe concentration in $Zn_2TiO_4$. Consequently, there exists an optimized concentration of iron for improved photocatalytic activity under visible light (${\lambda}{\leq}$420 nm)

• Journal of the Korean Chemical Society
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• 제37권4호
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• pp.401-407
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• 1993

The titanium oxide thin films were prepared by air oxidation and water vapor oxidation. The electrochemical properties of the electrodes were studied in 1M NaOH solution. The peak potentials of oxygen reduction from cyclic voltammogram techniques were observed at aroung -0.9 ∼ -1.0 V vs. SCE and the reaction was totally irreversible process. The electrochemical properties of titanium dioxide electrodes prepared by water vapor oxidation exhibited different from the air oxidized electrodes, but it was similar to single crystal $TiO_2$. The peak potentials of oxygen reduction were observed at slightly more positive than flat band potentials and depended on pH.

• Journal of Environmental Science International
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• 제14권2호
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• pp.221-230
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• 2005

Catalytic wet oxidation of trichloroethylene (TCE) in water has been conducted using $TiO_2-supported$ cobalt oxides at $36^{\circ}C$ with a weight hourly space velocity of $7,500\;h^{-1}.\;5\%\;CoO_x/TiO_2$, prepared by using an incipient wetness technique, might be the most promising catalyst for the wet oxidation although it exhibited a transient behavior in time on-stream activity. Not only could the bare support be inactive for the wet decomposition reaction, but no TCE removal also occurred by the process of adsorption on $TiO_2$ surface. The catalytic activity was independent of all particle sizes used, thereby representing no mass transfer limitation in intraparticle diffusion. XPS spectra of both fresh and used Co surfaces gave different surface spectral features for each $CoO_x,\;Co\;2P_{3/2}$ binding energy for Co species in the fresh catalyst appeared at 781.3 eV, which is very similar to the chemical states of $CoTiO_x$ such as $CO_2TiO_4\;and\;CoTiO_3$. The used catalyst exhibited a 780.3-eV main peak with a satellite structure at 795.8 eV. Based on XPS spectra of reference Co compound, the TCE-exposed Co surfaces could be assigned to be in the form of mainly $Co_3O_4$. XRD patterns for $5\%\;CoO_x/TiO_2$ catalyst indicated that the phase structure of Co species in the catalyst even before reaction is quite comparable to the diffraction lines of external $Co_3O_4$ standard. A model structure of $CoO_x$ present predominantly on titania surfaces would be $Co_3O_4$, encapsulated in thin-film $CoTiO_x$ species consisting of $Co_2TiO_4$ and $CoTiO_3$, which may be active for the decomposition of TCE in a flow of water.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 한국반도체및디스플레이장비학회 2006년도 추계학술대회 발표 논문집
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• pp.110-114
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• 2006

Dielectric properties of glass-ceramics with fresnoite(Ba2TiSi208) crystals have been investigated in xK20-(33.3-x)BaO-16.7TiO2-50SiO2 ($0{\leq}x{\leq}20mol%$) glasses. The glassy nature was analyzed by differential thermal analyses and glass-ceramics was variable and control table by the processing parameters like time and temperature. Dielectric constant was measured over a temperature from 125K to 425k at frequencies form 100Hz to 1MHz, and laid in the range 16-10. Piezoelectric constant d33 was measured using a YE2703A d33meter and changed from 5.9 to 4.8pCN-1 with x contents. The spontaneous polarization Ps estimated from the hysteresis at ${\pm}1.2kV$ was ${\sim}0.3\;{\mu}C/cm2$ at room temperature.

• Electrical & Electronic Materials
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• 제9권7호
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• pp.652-659
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• 1996

Sintering characteristics and electrical properties of xPb(Mg$_{1}$8/Te$_{1}$8/Mn$_{1}$4/Nb$_{1}$2/) $O_{3}$-(1-x) Pb (Zr$_{1}$2/ $Ti_{1}$2/) $O_{3}$ (x=0.075, 0.1, 0.125) ceramics are investigated. A sintering temperature of ceramics could be reduced to 950.deg. C by a reaction between PbO and B site compound material. The physical properties of 0.1Pb(Mg, Te, Mn, Nb) $O_{3}$ - 0.9Pb(Zr, Ti) $O_{3}$ bulk ceramic with 3wt% glass frit(0.857PbO-0.143W $O_{3}$) were following : den = 7.95 g/cm$^{3}$, T$_{c}$=340.deg. C, .epsilon.$_{33}$= 754, k$_{31}$=0.3 and Q.=1780. The 3-layer piezoelectric transformer by using a tape casting method showed a good monolithic structure, and its voltage setup ratio was 2.5 times higher than that of a single device by using bulk ceramics.s.s.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
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• pp.304-307
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• 1999

The Mg($_{1-x}$ )S $r_{x}$Ti $O_3$(x=0.1,0.2,0.3) ceramics were prepared by the conventional mixed oxide method. The structural properties were investigated with calcining temperature and composition ratio by XRD and DT-TGA. Increasing the calcining temperature from 80$0^{\circ}C$ to 100$0^{\circ}C$, second phase was decreased and average particle size was increased. The SrTi $O_3$ ceramics of calcined at 100$0^{\circ}C$ had a structure of polycrystalline perovskite without the secondary phases. The average particle size of the $Mg_{0.9}$S $r_{0.1}$Ti $O_3$ ceramics calcined at 100$0^{\circ}C$ were 0.67${\mu}{\textrm}{m}$..>......

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2001년도 춘계학술대회 논문집 유기절연재료 전자세라믹 방전플라즈마 연구회
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• pp.157-160
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• 2001

We have investigated the Dielectric and Piezoelectric properties of $xPb(R_{1/2}Ta_{1/2})O_3-(1-x)Pb(Zr_{0.52}Ti_{0.48})O_3$ (R=Al,Y) solid solutions in which R ions are substituted for Al and Y ions. The maximum value of electromechanical coupling factor kp of 55% and 51% were obtained at the composition of 5mol% PAT and 5mol% PYT. However mechanical quality factor$(Q_m)$ had a minimum value of 44 and 69 at the composition of 5mol% PAT and 5mol% PYT. Also, the maximum value of piezoelectctric constant of $d_{33}(329[pC/N])$ and $d_{33}(310[pC/N])$ were obtained at the composition of 5mol% PAT and 5mol% PYT.

• Journal of the Korean Electrochemical Society
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• 제24권3호
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• pp.52-64
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• 2021

The effect of Fe and BO₃ doping on structure, thermal, and electrical properties of Li_1+xFe_xTi_2-x(PO₄)_3-y(BO₃)_y (x = 0.2, 0.5)-based glass and glass ceramics was investigated. In addition, their crystallization behavior during sintering and ionic conductivity were also investigated in terms of sintering temperature. FT-IR and XPS results indicated that Fe²⁺ and Fe³⁺ ions in Li_1+xFe_xTi_2-x(PO₄)_3-y(BO₃)_y glass worked as a network modifier (FeO₆ octahedra) and also as a network former (FeO₄ tetrahedra). In the case of the glass with low substitution of BO₃, boron formed (PB)O₄ network structure, while boron preferred BO₃ triangles or B₃O₃ boroxol rings with increasing the BO₃ content owing to boic oxide anomaly, which can result in an increased non-bridging oxygen. The glass transition temperature (GTT) and crystallization temperature (CT) was lowered as the BO₃ substitution was increased, while Fe²⁺ lowered the GTT and raised the CT. The ionic conductivity of Li_1+xFe_xTi_2-x(PO₄)_3-y(BO₃)_y glass ceramics were 8.85×10^-4 and 1.38×10^-4S/cm for x = 0.2 and 0.5, respectively. The oxidation state of doped Fe and boric oxide anomaly were due to the enhanced lithium ion conductivity of glass ceramics.

• Korean Journal of Materials Research
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• 제6권5호
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• pp.449-456
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• 1996

BaO, SrCI2.6H2O 그리고 Ti(OPri)4를 출발 원료로 사용하여 균일한 BaxSr1-xTiO3(BST) 솔을 합성하였고, BST 박막을 회전 코팅 법으로 Si 및 Pt/Ti/SiO2/Si 기판위에 제조하였다. 적외선 및 NMR 스펙트럼 분석으로 킬레이션 조제로 사용한 acetylacetone(AcAc)이 엔올 형태로 Ti-알콕사이드와 결합하여 솔 안정화에 기여함을 확인하였다. Xedrogel에 대한 DT/TGA 및 적외선 스펙트럼 결과로부터 페로브스카이트 상생성이 $600^{\circ}C$ 이상에서 이루어짐을 관찰하였다. $700^{\circ}C$에서 열처리한 박마은 -300(10 KHz)의 상대유전율을 나타내었고, 결정립의 저항 및 입계의 병렬 RC 성분으로 등가회로를 구성할 수 있었다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• 제11권6호
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• pp.246-251
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• 2001

The $[(Pb_{1-x}$La_{2x/3})TiO_3$, X=0.2] powder was synthesized by the hydrothermal method, and their sintering and dielectric properties according to Mn additive were examined. The relative density of sintered PLT specimen at $1150^{\circ}C$ for 5 hrs with Mn 0.02 mol% additive was 96.7%. The dielectric properties of sintered PLT specimen were changed by content of Mn and increacement of sintering temperature. Dissipation factor was improved by increasing of measuring temperature. Curie temperature of sintered PLT specimens was decreased with increasing of Mn additive.