• Journal of the Korean Ceramic Society
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• v.47 no.6
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• pp.638-642
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• 2010

The spinel material $Li_4Ti_5O_{12}$ has attracted considerable attention as an anode electrode material for many battery applications owing to its light weight and high energy density. However, the real capacity of $Li_4Ti_5O_{12}$ powder as determined by the solid-state method is lower than the ideal capacity. In this study, we investigated the effect of the dopants in M-doped spinel $Ba_xLi_{4-2x}Ti_5O_{12}$(x=0.005, 0.05, 0.1) powders prepared by the solid-state reaction method and used as the anode material in lithiumion batteries. The results confirmed the effect of the Ba and Sr dopants on the powder properties of the spinel $Li_4Ti_5O_{12}$, which exhibited a pure spinel structure without any secondary phase in its XRD pattern. Moreover, the electrochemical properties of the spinel M-LTO materials were investigated using a half cell. The electrochemical data show that cells with anodes made of undoped $Li_4Ti_5O_{12}$ and Ba- and Sr-doped $Li_4Ti_5O_{12}$ have discharge capacities of 97, 130, and 112 mAh/g, respectively, at the first cycle. Moreover, the Ba- and Sr-doped spinel $Li_4Ti_5O_{12}$ demonstrated good properties in the mid-voltage range at 1.55 V, showing stable cyclic voltammogram properties which surpassed those of the same material without Ba or Sr at 1 C after 100 cycles.

• 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 Institute of Electrical and Electronic Material Engineers
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• v.37 no.3
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• pp.274-279
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• 2024

Eu³⁺-doped BaZrO₃ (BaZrO₃:Eu³⁺) phosphor powders were prepared using a solid-state reaction by changing the molar concentration of Eu³⁺ within the range of 0.5 to 30 mol%. Irrespective of the molar concentration of Eu³⁺ ions, the crystal structures of all the phosphors were cubic. The excitation spectra of BaZrO₃:Eu³⁺ phosphors consisted of an intense broad band centered at 277 nm in the range of 230~320 nm. The emission spectra were composed of a dominant orange band at 595 nm arising from the ⁵D₀→⁷F₁ magnetic dipole transition of Eu³⁺ and two weak emission bands centered at 574 and 615 nm, respectively. As the concentration of Eu³⁺ increased from 0.5 to 10 mol%, the intensities of all the emission bands gradually increased, approached maxima at 10 mol% of Eu³⁺ ions, and then showed a decreasing tendency with further increase in the Eu³⁺ ions due to the concentration quenching. The critical distance between neighboring Eu³⁺ ions for concentration quenching was calculated to be 11.21 Å, indicating that dipole-dipole interaction was the main mechanism of concentration quenching of BaZrO₃:Eu³⁺ phosphors. The results suggest that the orange emission intensity can be modulated by doping the appropriate concentration of Eu³⁺ ions.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2006.10a
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• pp.22-25
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• 2006

Long lasting phosphor materials are in great demand for their applications in the area of light emitting diodes (LEDs), commercial displays and warning signals. After glow longevity, brightness, photo-resistance and chemical and environment stability are most important qualities that are desired for these materials. Alumina as host lattice with various rare earth elements has been found to be good at the same time inexpensive material for the synthesis of the phosphor materials. This communication explored the effect of mixed rare earth metal on the luminescence properties of these materials for the first time. Various permutations and combinations of $Sr^{2+}$ and $Ba^{2+}$ have been investigated in order to achieve robust and high luminescence characteristics in the tailored phosphor materials.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.338-341
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• 2002

$(Ba_{1-x}Sr_{0.4}Ca_x)TiO_{3}$ (x=0.10, 0.15, 0.20) powders were prepared by the sol-gel method and BSCT thick films were fabricated by the screen-printing method. Their structural and dielectric properties were investigated with variation of composition ratio and $Al_{2}O_{3}$ doping contents. As results of the X-ray diffraction and microstructure analysis, the grain size of BSCT thick films was decreased with increasing $Al_{2}O_{3}$ amount. The thickness of BSCT thick films by 4-coating/drying is about $110{\sim}120{\mu}m$. The tunability increased with decreasing Ca content, and the BSCT(50/40/10) specimen doped with 1.0wt% $Al_{2}O_{3}$ showed the highest value of 12.94% at 5kV /cm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.246-247
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• 2007

(Ba,Sr,Ca)$TiO_3$ powders, which were prepared by sol-gel method using a solution of Ba-acetate, Sr-acetate and Ca-acetate and Ti iso-propoxide, were mixed with organic vehicle and the BSCT thick films were fabricated by the screen-printing techniques on high purity alumina substrates. The structural and dielectric properties were investigated for various $Dy_2O_3$ doping contents. As a result of thermal analysis, the exothermic peak was observed at around $670^{\circ}C$ due to the formation of the polycrystalline perovskite phase. All BSCT thick films, sintered at $1420^{\circ}C$ for 2h, showed the typical XRD patterns of perovskite polycrystalline structure and no pyrochlore phase was observed. The average grain size of the specimens decreased with.

• Journal of the Korean Ceramic Society
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• v.22 no.4
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• pp.15-20
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• 1985

$(Ba_{0.5} Pb_{0.5})_{1-x} Nd_x TiO_3$ 중의 $_x(Nd$의 양)를 변화시키면서 격자상수와 전기전도도를 측정하였다 c축과 a축의 비(c/a) 의 극대값은 실온에 있어서 전기전도도의 극대값과 일치하였다. 이것은 Nd원자의 치환위치와 강유 전성의 변화에 의한 것으로 고찰되었다 Curie 온도이하에서는 Nd 첨가량의 증가에 따라 전기전도도의 활성화에너지가 증가하는 경향을 나타내었다 이것은 입경의 감소에 따른 Spontaneous polarization의 저하가 원인으로 고찰되었다 첨가량의 역학을 입계의 potential barrier의 높이와 관련지어 논하였다.

• 한국초전도학회:학술대회논문집
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• 2009.07a
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• pp.11-11
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• 2009

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.6
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• pp.278-282
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• 2010

The doping effect of thulium on electrical properties and degradation behavior in barium titanate ceramics ($BaTiO_3$) was investigated in terms of generations of core-shell structure and micro-chemical changes through highly accelerated degradation test. The dielectric specimens of pellet type and multi-layered sheets were prepared by using $BaTiO_3$ with undoped and doped with 1 mol% $Tm_2O_3$. The $BaTiO_3$ ceramics doped with 1 mol% $Tm_2O_3$ had 40% higher dielectric constant (${\varepsilon}$ = 2700) than that of the undoped $BaTiO_3$ specimen at curie temperature and met X7R specification. According to the result of highly accelerated degradation test conducted at $150^{\circ}C$, 70 V, and 24 hr, the oxygen diffusion was declined in dielectrics doped with 1 mol% $Tm_2O_3$. The $Tm^{3+}$ ion substituted selectively Ba site and Ti site and contributed to the generation of the core-shell structure. Oxygen vacancies occurred by substitution for Ti site could reduce excess oxygen that reacted to the Ni electrode.

• Transactions on Electrical and Electronic Materials
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• v.4 no.2
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• pp.24-28
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• 2003

(Ba,Sr,Ca)TiO$_3$ powders, prepared by the sol-gel method, were mixed with organic binder and the BSCT thick films were fabricated by the screen printing techniques on alumina substrates. All the BSCT thick films, sintered at 1420$^{\circ}C$, showed the typical XRD patterns of a perovskite polycrystalline structure. The average grain sizes decreased with increasing amounts of ZrO$_2$, and the BSCT(40/40/20) thick films doped with 2wt% MnO$_2$ showed a value of 8$\mu\textrm{m}$. The thickness of thick films by four-cycle on printing/drying was approximately 951$\mu\textrm{m}$. The relative dielectric constant decreased with increasing Ca content and MnO$_2$ doping amount. The relative dielectric constant, dielectric loss and tunability of the BSCT(50/40/10) thick films doped with 2.0wt% ZrO$_2$ were 772, 0.184％ and 15.62%, respectively.