• Korean Chemical Engineering Research
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• v.45 no.4
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• pp.378-383
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• 2007

A novel fabrication method for the multi-component metal oxides such as zirconium titanate($Zr_xTi_{1-x}O_2$) has been suggested, which would yield the uniform film characteristics and control the film composition at relatively low process temperature. The method has the basic concept that firstly layer-by-layer structure is constructed with the primitive oxide layers, which are components of the desired multi-component oxides, and secondly the film is annealed at appropriate thermal conditions for the transformation to a single-phase multi-component oxides. In this study, PRTMOCVD(pulsed rapid thermal metalorganic chemical vapor deposition) possessing the superior thickness controllability was introduced to prepare $ZrO_2$ and $TiO_2$ thin film for zirconium titanate. Single-phase zirconium titanate thin films have been prepared successfully by the interdiffusion of oxide multilayers having several alternating layers of $ZrO_2$ and $TiO_2$. The Zr/Ti ratio of zirconium titanate could be controlled easily by altering the thickness of $ZrO_2$ and $TiO_2$ thin film.

• Analytical Science and Technology
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• v.15 no.1
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• pp.15-19
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• 2002

The pretreatment of tungsten added $BaTiO_x$ ceramics was performed to improve the recovery of Ba, Ti and W. $BaTiO_x$ ceramics were digested with HF : HCl ( 1 : 2 ) mixture in an acid digestion bomb at $220^{\circ}C$ for 3 hrs. The concentration of Ba, Ti and W were determined by ICP-AES. Recoveries of Ba, Ti and W were 99.6%, 99.8% and 99.2%, respectively. And their C.V. values were 1.02%, 0.73% and 1.79%. Using this method, the analytical results of Ba, Ti and W for a real sample were obainted to be 25.9% (w/w), 38.8% (w/w) and 3.31% (w/w), respectively.

• Korean Journal of Materials Research
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• v.11 no.8
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• pp.708-712
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• 2001

Microwave dielectric properties of $(Pb_{0.2}Ca_{0.8})[(Ca_{1/3}Nb{2/3})_{1-x}Ti_x]O_3$ ceramics were investigated as a function of $Ti^{4+}$ content (0.05$\leq$x$\leq$0.35). A single perovskite phase was obtained from x=0.05 to x=0.15, and $TiO_2$ and $CaNb_2O^6$ were detected as a secondary phase beyond x=0.2. The structure was changed from orthorhombic at x=0.05 to cubic at x=0.35. Dielectric constant(K) was increased with increase of $Ti^{4+}$ content due to increase of rattling effect, and was inversely proportional to the cube of the average radius of B-site cation, however, Qf value was decreased, which was due to the decrease of grain size and the secondary phase. With the increase of $Ti^{4+}$ content, the temperature coefficient of resonant frequency(TCF) was controlled from -27.36 ppm/$^{\circ}C$ value to +18.4 ppm/$^{\circ}C$ value, which was caused by the influence of tolerance factor(t) and the bond valence of B-site. Typically, K of 51.67, Qf of 7268(GHz), TCF of 0 ppm/$^{\circ}C$ were obtained in the $(Pb_{0.2}Ca_{0.8})[(Ca_{1/3}Nb_{2/3})_{0.8}Ti_0.2]O_3$ sintered at 13$50^{\circ}C$ for 3h.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.286-287
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• 2012

Reset-first resistive switching mechanism based on reduction reaction in HfO2-x with oxygen drift-diffusion was studied. we first report that the indirect evidence of local filamentary conductive path formation in bulk HfO2 film with local TiOx region at Ti top electrode formed during forming process and presence of anion-migration at interface between electrode and HfO2 during resistive switching through high resolution transmission electron microscopy (HRTEM), electron disperse x-ray (EDX), and electron energy loss spectroscopy (EELS) mapping. Based on forming process mechanism, we expected that redox reaction from Ti/HfO2 to TiOx/HfO2-x was responsible for an increase of initial current with increasing the post-annealing process. First-reset resistive switching in above $350^{\circ}C$ annealed Ti/HfO2 film was exhibited and the redox phenomenon from Ti/HfO2 to TiOx/HfO2-x was observed with high angle annular dark field (HAADF) - scanning transmission electron microscopy (STEM), EDX and x-ray photoelectron spectroscopy. Therefore, we demonstrated that the migration of oxygen ions at interface region under external electrical bias contributed to bipolar resistive switching behavior.

• Bulletin of the Korean Chemical Society
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• v.30 no.12
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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 Korean Ophthalmic Optics Society
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• v.2 no.1
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• pp.9-16
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• 1997

Ferroelectric $Pb_5Ge_{3-x}Ti_xO_{11}$(x=0, 0.015, 0.021, 0.03) single crystals were obtained from the melt by the Czochralski method. Grown crystals were pale brownish yellow and fully transparent. The dielectric relaxation of the $Pb_5Ge_{3-x}Ti_xO_{11}$ single crystals has been studied in the frequency range from 100 Hz to 10 MHz between $20^{\circ}C$ and $600^{\circ}C$. From the results of the these measurements. the temperature of the permittivity maximum was shifted to low temperature with increasing Ti content and the permittivity maximum decreased with increasing Ti content. The frequency dependent dielectric response of $Pb_5Ge_{3-x}Ti_xO_{11}$ single crystals exhibits a Debye type relaxation, with a distribution of relaxation times. Dielectric behavior is characteristic of carrier-dominated response.

• Journal of the Korean Chemical Society
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• v.30 no.1
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• pp.19-26
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• 1986

A titanium oxide thin films were prepared by air oxidation and vapour oxidation and a $TiO_2$ single crystal was reduced by heating in an argon atmosphere. All the electrode characteristics of the Ti$O_{2-x}$, thin films are not different from those of slightly reduced single crystal rutile. In cyclic voltammogram of oxygen containing electrolyte solution at Ti$O_{2-x}$ electrodes, cathodic peaks were observed at between -0.8V and -1.0V vs. SCE. The cathodic current near 0V vs. SCE in saturated solution with nitrogen was observed to be greater than in saturated solution with air. The chronoamperogram was represented by the equation of i = $i_0e^{-kt}$, when the rate constant k was represented by the equation of k =$k_0{[H^+]}^nexp(A{\eta}+E_a/RT)$ The values of activation energy $E_a $were found to be 4.6~4.8kcal/mole in overpotential range of 0.035∼0.145 V and 1.6kcal/mole in overpotential range of 0.2∼0.5V. The values of n and A were found to be 0. 1 and 5.4~5.6/V in range of 0.035~0.145V, and in range of 0.2~0.5V, to be 0.04 and 1.3/V, respectively. This can be interpreted as an totally irreversible reduction of oxygen.

• Journal of the Korean Ceramic Society
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• v.45 no.12
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• pp.821-826
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• 2008

Nanocrystallized glasses with the composition of $(50-x)BaO-xTiO_2-50SiO_2$ (x=10, 15, 16.7 and 20) have been prepared by heat-treatment at $T_x$ (crystallization onset temperature) for 3 h, and their optical properties, photoluminescence (PL), XRD and Raman spectra have been examined. The absorption edges of the glasses were red-shifted and the absorption coefficient increased with an increase of $TiO_2$. The glass subjected to the heat-treatment showed a dense formation of ${Ba_2}{TiSi_2}{O_8}$ crystals. The XRD and Raman results show that the nanocrystallized glasses formed fresnoite phase up to $TiO_2$ concentrations of 15 mol%. Further-more, blue luminescence with a peak at the wavelength of around 470nm was observed in the nanocrystallized glass, demon strating the optical multifunctional nanocrystallized material such as non-linear optics and photo-luminescence. It is thought that the blue luminescence from the ${Ba_2}{TiSi_2}{O_8}$ nanocrystallized glass originated from the presence of $Ti^{4+}$ incorporated into the fresnoite-type structure.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.5
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• pp.216-221
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• 2006

An investigation of the influence of $WO_3$ and $V_2O_5$ catalysts on the microstructure, phase formation and selective catalytic reduction (SCR) efficiency of the synthesized SCR powders has been carried out. A commercial anatase-$TiO_2$ was used as the catalysts 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 from $1200^{\circ}C$ of $TiO_2$ support to ${\sim}900^{\circ}C$. The transition temperature was also lowered to below $650^{\circ}C$ in the $V_2O_5$(5 and 10 wt%) added composition. The $WO_3(10wt%)/TiO_2$ SCR powder obtained at $450^{\circ}C$ showed near 100% of $NO_x$ conversion efficiency at $350{\sim}400^{\circ}C$ and for the powder prepared at $650^{\circ}C$ the same efficiency was achieved in wider temperature range $300{\sim}400^{\circ}C$. The highest $NO_x$ conversion efficiency of 100% was obtained in the $V_2O_5(5wt%)/TiO_2$ SCR composition calcined at $650^{\circ}C$ in the relatively wider temperature range $250{\sim}350^{\circ}C$, while the catalytic efficiency considerably decreased for the $V_2O_5(10wt%)/TiO_2$. The lowered conversion efficiency of $NO_x$ observed in the $V_2O_5(10wt%)/TiO_2$ composition calcined at $650^{\circ}C$ was considered to be correlated with the lowered surface area resulting from the increased crystallite growth by highly reactive vanadium loading.

• Journal of the Korean Ceramic Society
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• v.43 no.1 s.284
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• pp.55-61
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• 2006

The microwave dielectric properties and low temperature sintering of $Ca[Ti_{1-x}(Ni_{1/3}Nb_{2/3})_x]O_3$ system were investigated at the sintering temperature $1,200\~1,350^{\circ}C$. The density and quality factors $(Q{\times}f)$ increased while dielectric constants slightly decreased with the decrease of Ti. The dielectric constant, quality factor, and temperature coefficient of resonance frequency $(\tau_f)$ were 64, 17,000 GHz, and $-9.1\;ppm/^{\circ}C$ respectively, when $CaTi_{1/2}(Ni_{1/3}Nb_{2/3})_{1/2}O_3$ ceramics were sintered at $1,300^{\circ}C$ for 4 h. $2Li_2O-B_2O_3$ was added to $CaTi_{1/2}(Ni_{1/3}Nb_{2/3})_{1/2}O_3$ to decrease the sintering temperature for LTCC application. The microwave dielectric properties of the samples sintered at $925^{\circ}C$ for 2 h with the addition of $6\;wt\%\;2Li_2O-B_2O_3$ were $\varepsilon_r=48.7,\;Q{\times}f=8,460\;GHz$, and $\tau_f=+5.6ppm/^{\circ}C$. Compatibility test of the composition with silver electrode shows no reaction with silver electrode, implying the feasibility as a high-K LTCC material.