• Journal of the Korean Ceramic Society
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• v.23 no.3
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• pp.53-61
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• 1986

A gas sensor which has been made by wet process had fabricated by coating each of the mixture on alumina tube and firing at 85$0^{\circ}C$ for 3hrs. A gas concentration such $H_2$, CO, $C_3H_8$, $C_2H_2$ and $CH_4$ vs its detection voltage characteristics has been in-vestigated on $SnO_2-In_2O_3-MgO$ system doped with PdO, $La_2O_3$, $ThO_2$, NiO and $Nb_2O_5$ The optimum sensitivity composition for various gases were 90w/o $SnO_2$-9w/o $In_2O_3$-1w/o MgO for $H_2$, $C_2H_2$ CO and $C_3H_8$ and 95w/o $SnO_2$-4w/o $In_2O_3$-1w/o MgO for $CH_4$. The sample which has been made by wet process than dry process had predominated sensitivity for each gases and particle size of the sample coprecipitated with PH=9 was 0.1${\mu}{\textrm}{m}$ The $SnO_2$-In2_O_3-MgO$ system doped with 2w/o $Nb_2O_5$ and NiO was the most sensitive for $H_2$ and $C_2H_2$ gas. In $SnO_2$-In2_O_3-MgO$ system doped with $ThO_2$ the sensitivity of $H_2$ gas was decreased but CO gas was in-creased when dopant con was increased.

• Journal of the Korean Ceramic Society
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• v.30 no.5
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• pp.397-403
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• 1993

Widely used dielectrics, barium titanate was promising material for ceramic capacitor. It was produced by specific formulation with various dopants-La2O3, ZrO2, SnO2, CaZrO3, CaTiO3, CaSnO3, Bi2O3, and etc.-according to demanded properties of capacitor. In this study, we would examinate the study of dielectric properties and temperatuer characteristics (T.C.) with the amount of Bi2O3. The sample was prepared with [BaTiO3]10＋[BaZrO3, SnO2, La2O3, ZrO2]10 and Bi2O3 varied from 1.0, 1.5, 2.0, 2.5 to 3.0wt%. After milling and mixing for 15hrs, each sample was dried and then pressed at 700kg/$\textrm{cm}^2$ into pellets. Pellets were fired at 131$0^{\circ}C$, for 3hrs in air. As the result of measurements, dielectric constant, break down voltage, and insulation resistance were increased with the amount of Bi2O3, and the resonant frequency was shifted from high frequency to low frequency range. In the case of temperature characteristics, capacitance change rate was symmetrically changed at -$25^{\circ}C$ and ＋85$^{\circ}C$ respectively. Therefore, it is recognized that the temperature characteristics can be moderated with doping Bi2O3 in our study.

• Journal of the Korean Ceramic Society
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• v.25 no.5
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• pp.488-494
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• 1988

Effects of MnO2 addition on themicrostructure, dielectric and piezoelectric properties of Rhombohedral, Tetragonal and Morphotropic phase boundary(MPB) in Pb(Ni1/3Nb2/3)O3-PbTiO3-PbZrO3 system were investigated and respectively the amount of MnO2 addition was 0, 0.2, 0.5, 1.0, 3.0wt%. In the tetragonal region, compared with the Rhombohedral and Morpotropic phase boundary, Mechanical quality factor(Qm), Curie temperature(Tc) and Dissipation factor were promoted by addition of MnO2. According to the results of the microstructure, dielectric and piezoelectric properties, the solid solution range of MnO2 addition in this system was 0.2-0.5wt%.

• Journal of the Speleological Society of Korea
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• no.78
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• pp.17-22
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• 2007

The melting temperature and critical temperature (Tc) of $YBa_2Cu_3O_x$ with deferent content impurities of PbO and $BaPbO_3$ were studied. When the PbO was used as addition in $YBa_2Cu_3O_x$, although the melting point could be reduced, the superconductivity (the transition wide, ${\Delta}T_c$) became poor. From the XRD pattern of the sintered mixture of $YBa_2Cu_3O_x$ and PbO it was known that there is a reaction between $YBa_2Cu_3O_x$ and PbO, and the product is $BaPbO_3$. In the process of the reaction the superconducting phase of $YBa_2Cu_3O_x$ was decreased and in the sample $BaPbO_3$ became the main phase. Therefore the superconductivity was reduced. $BaPbO_3$ was chosen as the impurity for the comparative study. The single phase $BaPbO_3$ was synthesized by the simple way from both mixtures of $BaCO_3$ and PbO, $BaCO_3$ and $PbO_2$. Deferent contents of $BaPbO_3$ (10%, 20%, 30%) were added in the $YBa_2Cu_3O_x$. By the phase analysis in the XRD patterns it was proved that there were not reactions between $YBa_2Cu_3O_x$ and $BaPbO_3$. When $BaPbO_3$ was used as impurity in $YBa_2Cu_3O_x$ the superconductivity was much better than PbO as impurity in $YBa_2Cu_3O_x$. But the melting point of $YBa_2Cu_3O_x$ with $BaPbO_3$ could not be found when the temperature was lower than $1000^{\circ}C$ in the DTA measurement.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.311-315
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• 2000

Vanadate glass in the $LiO_2-P_2O_5-Bi_2O_3-V_2O_5$ system containing 10mol% glass fonner, $P_2O_5$ and $Bi_2O_3$ was prepared by melting the batch in pt. crucible followed by Quenching on the copper plate. We found that $LiO_2-P_2O_5-Bi_2O_3-V_2O_5$ glass-ceramics obtained from nucleation of glass showed signifieantly higher capacity and longer cycle life than conventionally made crystalline $LiV_3O_{8}$. In the present paper, we describe the charge / discharge properties during crystallization process and find the best crystallization condition of $LiO_2-P_2O_5-Bi_2O_3-V_2O_5$ glass as cathod material.

• Journal of the Korean Ceramic Society
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• v.32 no.2
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• pp.234-238
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• 1995

MgFe2O4 formation, grain growth in Fe2O3, Fe solid-solution limit in MgO for MgO-Fe2O3 mixture were studied by means of investigating the distribution of phases and compositions in reaction area between MgO and Fe2O3. The reaction area at equlibrium was composed with MgO-FexO matrix and MgFe2O4 precipitation, MgFe2O4 was formed by precipitating from MgO-FexO matrix dependent on oxygen partial pressure. Fe contents was exponentially decreased with diffusion distance in MgO single crystal, and thus Fe solid-solution limitation in MgO was about 4mol%. The grain growth rate in Fe2O3 base was increased with Mg contents diffused from MgO single crystal.

• Korean Journal of Materials Research
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• v.4 no.2
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• pp.159-165
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• 1994

Two kinds of humidity sensor are made, one by anodizing pure aluminum and the other by evaporation Sn02 on the anodized pure alumia film, and their electrical characteristics are investigated in various humidity atmosphere. The change of surface resistance with humidity of $AI_2O_3/AI$ and $SnO_2-AI_2O_3/Al$ sensors are found to be $1.40 \times 10^{-2}\Omega$/RH and $1.56 \times 10^{-2}\Omega$/RH, respectively. The hysteresis phenomena associated with the irreversibility of surface resistance-humidity is less in $SnO_2-AI_2O_3/Al$ sensor than in $AI_2O_3/AI$. It is concluded that $SnO_2-AI_2O_3/Al$ film can be used as humidity sensor in room temperature region because temperature dependence of surface resistance of the film is found to be as $0.56 \times 10^{-2} \Omega /^{\circ}C$ in O~ $20^{\circ}C$ range, where as $2.50 \times 10^{-2} \Omega /^{\circ}C$ in 40-$50^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.28 no.4
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• pp.305-314
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• 1991

This study was conducted to research the formation and the color development of NiO-ZnO-Fe2O3-TiO2-SnO2 system for the purpose of synthesizing the spinel pigments which are stable at high temperature. After preparing ZnO-Fe2O3 as a basic composition, {{{{ chi }}NiO.(l-{{{{ chi }})ZnO.Fe2O3 system, {{{{ chi }}NiO.(l-{{{{ chi }})ZnO.TiO2 system, and {{{{ chi }}NiO.(l-{{{{ chi }})ZnO.SnO2 system were prepared with {{{{ chi }}=0, 0.2, 0.5, 0.7, 1 mole ratio respectively. The manufacturing was carried out at 128$0^{\circ}C$ for 30 minutes. The reflectance measurement and the X-ray analysis of these specimens were carried out and the results were summarized as follows. 1. In the specimens which included NiO, it was difficult for the spinel structure to be formed. 2. As increasing the contents of NiO and Fe2O3, all the groups which were yellow or green colored changed to brown. 3. NiO-ZnO-Fe2O3 system and NiO-ZnO-TiO2 system formed the spinel structure and the illmenite structure appeared in NiO-TiO2 system.

• Bulletin of the Korean Chemical Society
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• v.26 no.10
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• pp.1525-1528
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• 2005

The synthesis and characterization of ${K_3[Ru(C_2O_4)3]{\cdot}4H_2O\;(C_2O_4}^{2-}$ = oxalato anoin) complex are described, and its redox properties (in buffer solution of pH = 12) have been investigated. This complex is used for in situ generation of oxoruthenates complexes which have been characterized by electronic spectroscopy. Reaction of ${K_3[Ru(C_2O_4)3]{\cdot}4H_2O$ with excess ${S_2O_8}^{2-}$ in molar KOH generates trans-${[RuO_3(OH)_2]^{2-}/S_2O_8}^{2-}$ reagent while with excess ${BrO_3}^-$ in molar $Na_2CO_3$ generates ${[RuO_4]^-/BrO_3}^-$ reagent. Avoiding the direct use of [$RuO_4$] the organic-soluble $(n-Pr_4N)^+[RuO_4]^-$, (TPAP) has been isolated by reaction of $K_3[Ru(C_2O_4)3]{\cdot}4H_2O$ with excess ${BrO_3}^-$ in molar carbonate and n-$Pr_4$NOH. In a mixture of $H_2O/CCl_4$ ruthenium tetraoxide can be generated by reaction of $K_3[Ru(C_2O_4)3]{\cdot}4H_2O$ with excess ${IO_4}^-$. The catalytic activities of oxoruthenates that have been made from $K_3[Ru(C_2O_4)3]{\cdot}4H_2O$ towards the oxidation of benzyl alcohol, piperonyl alcohol, benzaldehyde and benzyl amine at room temperature have been studied.

• Bulletin of the Korean Chemical Society
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• v.32 no.11
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• pp.3991-3995
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• 2011

$TiO_2-SiO_2-In_2O_3$ nanocomposite thin film was deposited on the glass substrates using a dip coating technique. The morphology, surface composition, surface hydroxyl groups, photocatalytic activity and hydrophilic properties of the thin film were investigated by AFM, XPS, methyl orange decoloring rate and water contact angle measurements. The hydroxyl content for $TiO_2$, $TiO_2-SiO_2$ and $TiO_2-SiO_2-In_2O_3$ nanocomposite films was calculated to be 11.6, 17.1 and 20.7%, respectively. $TiO_2-SiO_2-In_2O_3$ film turned superhydrophilic after 180-min irradiation with respect to pure $TiO_2$ and $TiO_2-SiO_2$ thin films. The photocatalytic decomposition of methyl orange for $TiO_2$, $TiO_2-SiO_2$ and $TiO_2-SiO_2-In_2O_3$ thin films was measured as 38.19, 58.71 and 68.02%, respectively. The results indicated that $SiO_2$ and $In_2O_3$ had a significant effect on the hydrophilic, photocatalytic and self-cleaning properties of $TiO_2$ thin film.