• Journal of the Korean Ceramic Society
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• v.27 no.7
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• pp.934-942
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• 1990

The quarternary system ceramics 0.5[yPb(Zn1/3Nb2/3)O3-(1-y)Pb(Ni1/3Nb2/3)O3]-0.5[xPbTiO3-(1-x)PbZrO3](PZN-PNN-PT-PZ) was fabricated by the columbite precursor method to obtain a stabilized perovskite structure and by conventional method to evaluate the efficiency of the former methd. Dielectric and piezoelectric properties were investigated and the stability of the perovskite phase was studied as a function of PZN and PT contents and firing temperature. In the samples prepared by the columbite precursor method, the pyrochlore phase, which is detrimental to both the dielectric and piezoelectric properties, was not observed in the absence of PZN, and electric properties were improved even when fabricated at low temperature. By adding PZN, some pyrochlore phase appeared and the morphotropic phase boundary of the samples shifted to more Zr-rich composition. The temperature dependence of piezoelectric constant decreased with the addition of PZN, due to the rising of the Curie point.

• Journal of Powder Materials
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• v.10 no.6
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• pp.448-455
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• 2003

$TiO_2$ nanopowder has been synthesized by means of the flame method using a precursor of titanium tetraisopropoxide (TTIP, Ti$(OC_3H_7)_4)$. In order to clarify the effect of cooling rate of hot flame on the formation of $TiO_2$ crystalline phases, the flame was controlled by varying the mixing ratio and the flow rate of gases. Anatase phase was predominantly synthesized under the condition having the steep cooling gradient in flame, while a slow cooling gradient enabled to form almost rutile $TiO_2$ nanopowder of above 95%.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.5
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• pp.213-218
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• 2014

An investigation of the influence of $WO_3$ addition with different precursors and preparation methods on the phase formation and selective catalytic reduction (SCR) efficiency of anatase-$TiO_2$ powders has been carried out. An anatase-$TiO_2$ synthesized by precipitation process was used as a catalyst support. For $WO_3(10wt%)/TiO_2$, the W loading to the $TiO_2$ support led to the lower in anatase to rutile transition temperature to ${\sim}900^{\circ}C$ from $1200^{\circ}C$ of the $TiO_2$ support alone. In the case of $WO_3(10wt%)/TiO_2$ SCR powders obtained from a wet process with ammonium meta-tungstate (AMT) precursor, the highest $NO_X$ conversion efficiency was achieved at $450^{\circ}C$ remaining high efficiency at $500^{\circ}C$, while the same composition prepared from a dry process with $WO_3$ addition showed the lowered efficiency with temperature after reaching the efficiency maximum at $350^{\circ}C$. The same tendency has been found that the $V_2O_5(5wt%)-WO_3(10wt%)/TiO_2$ SCR powders obtained from the wet process with AMT precursor has shown the superior $NO_X$ conversion efficiency over 90 % in a wider temperature range of $300{\sim}500^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.55 no.2
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• pp.140-144
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• 2018

$ZnO/TiO_2$ nanocomposites were synthesized via a modified sol-gel technique by incorporating 30 and 70 wt% $TiO_2$ nanopowder into a ZnO sol-gel matrix. Zinc acetate dihydrate was used as the ZnO precursor and de-ionized water as the solvent, while titanium oxysulfate was employed for the synthesis of $TiO_2$ nanopowder. The synthesized $ZnO/TiO_2$ nanocomposites were characterized by x-ray diffraction, UV-vis spectroscopy, scanning electron microscopy, and transmission electron microscopy. The $ZnO/TiO_2$ nanocomposites showed both the ZnO (wurtzite) and $TiO_2$ (anatase) phases. The average ZnO crystallite size of the $ZnO/TiO_2$ nanocomposites was found to be about 26.3 nm. The TEM results confirmed that spherical $TiO_2$ particles were embedded in the ZnO matrix. $TiO_2$ particles attached onto the rod-like ZnO particles were also observed. The $ZnO/TiO_2$ nanocomposites exhibited optical absorption properties superior to those of pure ZnO and $TiO_2$.

• Korean Journal of Materials Research
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• v.20 no.12
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• pp.669-675
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• 2010

One of the greatest challenges for our society is providing powerful electrochemical energy conversion and storage devices. Rechargeable lithium-ion batteries and fuel cells are among the most promising candidates in terms of energy and power density. As the starting material, $TiCl_4{\cdot}YCl_3$ solution and dispersing agent (HCP) were mixed and synthesized using ammonia as the precipitation agent, in order to prepare the nano size Y doped spherical $TiO_2$ precursor. Then, the $Li_4Ti_5O_{12}$ was synthesized using solid state reaction method through the stoichiometric mixture of Y doped spherical $TiO_2$ precursor and LiOH. The Ti mole increased the concentration of the spherical particle size due to the addition of HPC with a similar particle size distribution in a well in which $Li_4Ti_5O_{12}$ spherical particles could be obtained. The optimal synthesis conditions and the molar ratio of the Ti 0.05 mol reaction at $50^{\circ}C$ for 30 minutes and at $850^{\circ}C$ for 6 hours heat treatment time were optimized. $Li_4Ti_5O_{12}$ was prepared by the above conditions as a working electrode after generating the Coin cell; then, electrochemical properties were evaluated when the voltage range of 1.5V was flat, the initial capacity was 141 mAh/g, and cycle retention rate was 86%; also, redox reactions between 1.5 and 1.7V, which arose from the insertion and deintercalation of 0.005 mole of Y doping is not a case of doping because the C-rate characteristics were significantly better.

• Korean Journal of Materials Research
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• v.9 no.11
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• pp.1129-1136
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• 1999

TIN films were prepared on Si(100) substrate by ICP-CVD(inductive1y coupled plasma enhanced chemical vapor deposition) using TEMAT(tetrakis ethylmethamido titanium : Ti$[\textrm{N}\textrm{(CH)}_{3}\textrm{C}_{2}\textrm{H}_{5}]_{4}$) precursor at various deposition conditions. Phase, microstructure, and the electrical properties of TIN films were characterized by x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM) and electrical measurements. Polycrystalline TiN films with B1 structure were grown at temperatures over $200^{\circ}C$. Preferentially oriented along TiN(111) films were obtained at temperatures over $300^{\circ}C$ with the flow rates of 10, 5, and 5 sccm for TEMAT, $\textrm{N}_{2}$ and Ar gas. The TiN/Si(100) interface was flat and no chemical reaction between TIN and $\textrm{SiO}_2$ was found. The resistivity, carrier concentration and the carrier mobility for the TiN sample prepared at $500^{\circ}C$ are 21 $\mu\Omega$cm, 9.5$\times\textrm{10}^{18}\textrm{cm}^{-3}$ and $462.6\textrm{cm}^{2}$/Vs, respectively.

• Journal of the Korean Ceramic Society
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• v.42 no.7 s.278
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• pp.461-468
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• 2005

Transparent TiO$_{2}$ sols were prepared by hydrothermal synthesis to heat Ti precursor solutions, from Ti hydroxides obtained with neutralizing aqueous TiOCl$_{2}$ solutions having various concentrations of NaCI by aqueous NaOH solution, in the autoclave at 120$^{\circ}C$ The photocatalytic abilities of glass beads coated with the sol for gaseous benzene were evaluated. As a result, it was found that due to the increase of brookite phase in TiO$_{2}$ by controlling the concentration of Na ion the optical absorption of TiO$_{2}$ increases toward long wavelength but that in the area of short wavelength becomes relatively low and consequently the photocatalytic performance of TiO$_{2}$ thin film for benzene gas rather decreases, compared to that of composite film of anatase and brookite phases. These results suggest that in order for coated TiO$_{2}$ thin film to have high dissociation performance for benzene gas it is effective to form anatase and brookite phases compositely in TiO$_{2}$.

• Korean Journal of Materials Research
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• v.15 no.7
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• pp.444-447
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• 2005

In this study, $Hydroxyapatite+TiO_2(HAp+TiO_2)$ composite sol coatings on Cp-Ti substrates were deposited by using a sol-gel derived precursor. Prior to hydroxyapatite coating, the samples were micropolished and divided into three sets. The first set was coated with hydroxyapatite (HAp) directly on Cp-Ti. The second set was first coated with intermediate titania layer and then coated with HAp. The third set samples were coated with $HAp+TiO_2$ (50:50) composite sol. Each samples were predried at $200^{\circ}C$, and heat treated at $600^{\circ}C$. The formation of hydroxyapatite has been confirmed by XRD analyses and the substrate material was found to be oxidized with negligible amount of CaO in the coating. The NaOH treated samples showed the presence of rutile crystal. The SEM studies revealed surface morphologies of each samples. $HAp+TiO_2$ composite sol coating layer was found to be smooth. The bonding strength of each samples were calculated using pull out tests. The bonding strength of the $HAp+TiO_2$ composite sol coating on substrate was 29.35MPa.

• Korean Chemical Engineering Research
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• v.43 no.5
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• pp.609-615
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• 2005

$TiO_2$ particles, 30-300 nm in diameter, were prepared by thermal decomposition of titanium tetraisopropoxide (TTIP) using an aerosol microreactor, by which about $1{\mu}l$ of the liquid precursor is injected into an evaporator, 1 cc in volume, and vaporized precursor is then transported by nitrogen as a bolus to a tubular reactor 4 mm in diameter and 35 cm in length. Investigated were the effects of the reactor temperature and the concentration of TTIP vapor on the morphology, particle size distribution and crystalline structure of produced $TiO_2$ particles. With TTIP vapor concentration kept constant at 1 mol%, the reactor temperature was varied from 300 to 500 and $700^{\circ}C$. The primary particle size decreased with increasing the temperature, and the size distributions were mono-modal at 300 and $500^{\circ}C$, but bi-modal at $700^{\circ}C$. The TTIP vapor concentration was increased from 1 to 3.5 and 7 mol%, holding the reactor temperature at $700^{\circ}C$. The bi-modal distribution seen at the concentration of 1 mol% disappeared and the number of particles composing an agglomerate increased at the higher concentrations. These effects of the reactor temperature and the precursor concentration were discussed in comparison with experimental results reported earlier.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.118-118
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• 1999

CVD방법에 의한 TiN 박막 형성에 있어서 ICP-CVD 방법이 대두되고 있다. 이것은 precursor에 대한 radical 형성, 식각된 패턴에서 양 벽의 self-shadowing 효과, 낮은 tress등으로 dense 한 박막을 얻을 수 있기 때문이다. TiN 박막은 Si 기판의 온도를 상온에서 50$0^{\circ}C$까지 유지하면서 TEMAT의 유량을 5-20sccm으로 변화시키면서 증착하였다. 증착 후 TiN 박막의 결정화에 따른 열처리는 Ar과 N2-가스분위기에서 in-situ로 증착하였다. 증착 후 TiN 박막증착 조건수립에 따른 플라즈마 특성진단은 전자의 온도와 밀도, 평균 전자밀도, 이온 에너지 분포, radical 분포, negative 이온분포 등으로 측정하였다. 플라즈마 변수에 따른 TiN 박막의 결정성과 상 변화는 XRD로 분석하였고, 조성비 및 TiN 박막의 원소화학적 상태, 결합에너지, 각 상에 따른 결합 에너지 천이정도, 초기 형성과정 및 반응기구 등은 RBS와 XPS로 조사하였다. TiN 박막의 표면상태, morphology 거칠기, TiN/Si(100)구조에서 계면상태 등은 SEM, AFM, 그리고 HRTEM으로 분석하였다. TiN 구조 박막의 비저항, carrier concentration 그리고 mobility 측정은 박막의 표면이 균일하고 bls-홀이 없는 것으로 하여 4-point probe 방법으로 측정하였다. 이들 분석으로부터 ICP-CVD 방법에 의하여 형성된 TiN 박막이 초고집적 반도체 소자의 contact barrier layer로서의 적용 가능성을 평가하였다.