• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.251-251
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• 2007

A new type of a lead-free positive temperature coefficient of resistivity(PTCR) material. based on $(Bi_{1/2}Na_{1/2})TiO_3\;-\;BaTiO_3$ solid solution ceramics has been developed. The effect of $Nb_O_5$ and $Y_2O_3$ content on the electrical properties and the microstructure of (1-x) $(Bi_{1/2}Na_{1/2})TiO_3\;-\;x\;BaTiO_3$ (BNBT) ceramics made using a conventional mixed oxide process has been studied. The Curie Temperature was obviously increased with the increasing of $(B_{0.5}Na_{0.5})TiO_3$ content. The Y-doped BNBT ceramics(x=0.02) display low resistivity values of $10^2-10^3$ ohm*cm at room temperature and the Curie Temperature of $Tc=155^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• v.31 no.8
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• pp.2170-2174
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• 2010

The surfaces of $TiO_2$ and ZnO nanoparticles have been modified by gold (Au) nanoparticles by a reduction method in solution. Their interfacial electronic structures and optical absorptions have been studied by depth-profiling X-ray photoelectron spectroscopy (XPS) and UV-vis absorption spectroscopy, respectively. Upon Au-modification, UV-vis absorption spectra reveal a broad surface plasmon peak at around 500 nm. For the as-prepared Au-modified $TiO_2$ and ZnO, the Au $4f_{7/2}$ XPS peaks exhibit at 83.7 and 83.9 eV, respectively. These are due to a charge transfer effect from the metal oxide support to the Au. For $TiO_2$, the larger binding energy shift from that (84.0 eV) of bulk Au could indicate that Au-modification site of $TiO_2$ is different from that of ZnO. On the basis of the XPS data with sputtering depth, we conclude that cationic (1+ and 3+) Au species, plausibly $Au(OH)_x$ (x = 1-3), commonly form mainly at the Au-$TiO_2$ and Au-ZnO interfaces. With $Ar^+$ ion sputtering, the oxidation state of Ti dramatically changes from 4+ to 3+ and 2+ while that (2+) of Zn shows no discernible change based on the binding energy position and the full-width at half maximum (FWHM).

• Korean Journal of Materials Research
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• v.1 no.4
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• pp.206-213
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• 1991

The crystallized solder glasses with the low melting temperature for electronic package were prepared with the compositions of 77-80wt% PbO, 4.5-6wt% ZnO, 7.5-8.5wt% $B_2O_3$, 1-2wt% CaO, and 0.5-2.0wt% $P_2O_5$ containing 3-7wt% $TiO_2$. The Characterization of the solder glasses were studied using DTA, SEM and XRD. Frit containing 3wt% $TiO_2$ had crytallzation temperature range of $420-440^{\circ}C$. The major crystalline phase was identified as $2PbO{\cdot}ZnO{\cdot}B_2O_3$ by X-ray diffraction. Frits containing 4 wt% $TiO_2$ consisted of crysalline Phases of $PbTiO_3$ and $2PbO{\cdot}ZnO{\cdot}B_2O_3$ in the temperature range of $420-440^{\circ}C$, When g1ass frit containing 5wt% $TiO_2$ were heat-treated in the temperature range of $440-460^{\circ}C$, major crytalline phase was perovskite lead titanate.

• Journal of Magnetics
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• v.20 no.4
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• pp.353-359
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• 2015

Dielectric properties of $xBaTiO_3-(1-x)CoFe_2O_4$ composite materials have been investigated. Dielectric properties of $BaTiO_3$, $CoFe_2O_4$ and $0.5BaTiO_3-0.5CoFe_2O_4$ samples show frequency dependence, which is classified as relaxor behavior with different relaxing degree. The relaxor behaviors were described using the modified Curier-Weiss and Vogel-Fulcher laws. Among three above samples, the $BaTiO_3$ sample has highest relaxing degree. Photoluminescence spectral indicated defects, which might in turn control relaxing degree.

• Journal of the Korean Ceramic Society
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• v.33 no.11
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• pp.1195-1202
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• 1996

To prepare the dielectric thin films of (Pb1-xSrx)TiO3 (x=0.1, 0.2, 0.3, 0.35, 0.5) by the sol-gel process titanium (IV) isopropoxide (Ti[OCH(CH3)2]4) and Pb Sr, acetate were used therefore the thin films were fabricated by dip-coating method. Stability of the sol decreased with addition of Sr content thin films could be fabricated up to 35mol% Over this range precipitation of sol occured thin films couldn't be obtained. Transmittance of thin films at visible range decreased with the increase of heat-treatment temperature but exhibited transmit-tance above 60% in all case. Moreover transmittance of thin films at visible range slightly increased with of addition of Sr,. When thin film containing 30 mol% srontium was heated at 600℃ the best perovskite phase was obtained. The dielectric constant (ε) was 280 and dielectric loss factor (tan δ) was 0.021 and curie tempera-ture (Tc) decreased with the increase of addition of Sr.

• Proceedings of the Korean Ceranic Society Conference
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• 2000.04a
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• pp.53.1-53.1
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• 2000

• Journal of the Korean Ceramic Society
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• v.28 no.7
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• pp.525-530
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• 1991

The effects of 0.15mol% Y2O3 doped semiconducting (Ba1-xPbx)TiO3 ceramics with 0.5 mol% Pb5Ge3O11 as sintering additives have been investigated as function of Pb contents (from 0.05 mol to 0.3 mol) and sintering temperatures (from 1050$^{\circ}C$ to 1200$^{\circ}C$). As the Pb content increases in the (Ba1-xPbx)TiO3 system, the size and resistance of the grain increase but the capacitance of the grain boundary decreases due to the formation of liquid phase during the sintering. And with increasing the sintering temperatures, the resistance of the grain decreases but the capacitance of the grain boundary increases. The PTCR effects decrease with increasing the Pb content and the sintering temperature.

• Korean Journal of Crystallography
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• v.8 no.2
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• pp.97-104
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• 1997

Hydrothermal synthesis of PbZ1-xTixO3 has been investigated. Syntheses were performed using lead acetate triphdrate as Pb source, Ti/Zr gel by hydrolizing Ti-isopropoxide as Tiand Zr source and Zr-propoxide and KOH (0.5m, 1m, 2m) as mineralizer. The hydrothermal synthesis has been examined at 140℃, 150℃ and 160℃. Synthesized PZT powders showed a rectangular shape and were agglomerate. At 1m and 2m KOH concentrations PZT powders were synthesized the respective time of 8 hrs and 1hr but at 0.5m KOH concentration phase pure PZT powders were not synthesized for 5days reaction. At the conditions of low temperature and low KOH concentration unreacted Ti/Zr gel remained although synthesized powders were almost PZT. The size of PZT powders increased with KOH concentrations. PbO solid solutions were formed as intermediate phases and these were classified to PbO-10%TiO2 solid solution and PbO-3% TiO-3% TiO2 solid solution.

• Applied Chemistry for Engineering
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• v.31 no.1
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• pp.108-114
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• 2020

In this study, NH₃-selective catalytic oxidation (SCO) efficiencies according to calcination/reduction conditions were compared when preparing various Ru[1]/TiO₂ catalysts. The Ru[1]/TiO₂ red catalyst had better NH₃ conversion and NH₃ to N₂ conversion than those of Ru[1]/TiO₂ cal. Physico-chemical properties of Ru[1]/TiO₂ catalysts were confirmed by Brunauer Emmett Teller (BET), X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and temperature programmed reduction (H₂-TPR) analyses, and the properties were shown to affect the dispersion and surface adsorption oxygen species (O_β) ratio of the active metal.

• Bulletin of the Korean Chemical Society
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• v.16 no.12
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• pp.1180-1184
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• 1995

The precursors of Ba1-xSrxTiO3(x=0.0-0.3) were prepared by the rapid addition of aqueous solution of titanyl oxalate to the mixed aqueous solution of barium and strontium at room temperature. The optimum pH was theoretically calculated from the equilibrium constants and solubility products. The chemical formula of the precursors obtained corresponded to Ba1-xSrxTiO(C2O4)2·4H2O(x=0.0-0.3) as determined by thermal gravimetric analysis. The precursors were converted to stoichiometric Ba1-xSrxTiO3(x=0.0-0.3) with a particle size of 0.01-0.04 μm. As increasing the amount of strontium substituted to barium sites, the structure of crystal changed from the tetragonal phase to the cubic and the unit cell volume was decreased.