• 한국세라믹학회지
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• 제30권5호
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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.

• 한국세라믹학회지
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• 제30권3호
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• pp.199-205
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• 1993

Effects of grain size distribution on the breakdown voltage of ZnO varistors were investigated in the ZnO-Bi2O3-CoO-Sb2O3 and ZnO-Bi2O3-CoO-Sb2O3-Cr2O3 systems, respectively. The grain size was increased with increasing sintering temperature maintaining lognormal distribution in both systems. The width of grain size distribution of ZnO-Bi2O3-CoO-Sb2O3 system was narrower than that of ZnO-Bi2O3-CoO-Sb2O3 system. The breakdown voltage(Vb) was decreased by increasing sintering temperature(1000~135$0^{\circ}C$) and sintering time(0.5~5hr), due to the enhancement of ZnO grain growth. The current path of the ZnO varistor was dependent on the distribution of the largest grains (chains of long grains) between the electrodes.

• 한국재료학회지
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• 제26권2호
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• pp.90-94
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• 2016

In this study, to increase the strength and enhance the sintering property of $Al_2O_3$, $Y_2O_3$ and $La_2O_3$ were added; the effects of these additions on the sintering characteristics of $Al_2O_3$ were observed. Adding 1% of $Y_2O_3$ to $Al_2O_3$ repressed the development of abnormal particles and reduced the grain boundary migration of $Al_2O_3$, curbing pores to capture particles; as such, the material showed a fine microstructure. But, when over 2% of $Y_2O_3$ was added, the sintering property was reduced because of abnormal particle grain growth and pore formation in particles. Adding 1% of $Y_2O_3$ and $La_2O_3$ to $Al_2O_3$ led to the development of abnormal particles and formed pores in the particles; when over 3% of $La_2O_3$ was added, the sintering property was reduced because the shape of the $Al_2O_3$ particles changed to angled plates.

• 한국세라믹학회지
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• 제31권10호
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• pp.1240-1246
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• 1994

While sintering the Pb(Mg1/3Nb2/3)O3-PbTiO3-BaTiO3 system through solid-reaction route, pyrochlore(Pb3Nb4O13) phase while reduces the dielectric constant is inevitably formed. Substitution of Pb(Mg1/3Nb2/3)O3 with PbTiO3 and BaTiO3 can retard the occurrence of pyrochlore phase. The perovskite solid-solution without containing pyrochlore phase can be obtained when we consolidated the materials consisting of PbTiO3 and BaTiO3 at 1200℃ for 2 hours. The sintered body composed of 0.8Pb(Mg1/3Nb2/3)O3-0.1PbTiO3-0.1BaTiO3 composition showed the diffused phase transition(DPT) phenomena and the maximum value of dielectric constant at 0℃ (Tc') with the value of 1.3×104.

• 한국통신학회논문지
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• 제18권8호
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• pp.1102-1107
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• 1993

CaO-TiO2 이성분계에서 40~50 mol% CaO 조성범위를 선택하여 CaTiO3과 CaTiO3-TiO2세라믹스의 마이크로파 유전특성을 조사하였다. CaTiO3 단일상 (50 mol% CaO조성)일 때 유전율(er) 178, 공진주파수 (fo)의 온도계수(r,)+1000ppm/C, 픔질계수인 Q값 2760(fo=2.7 GHz)으로 가장 큰 값을 나타내었다. CaTiO3와 TiO2상이 혼합상으로 있는 유전체에서는 CaO 함량이 감소함에 따라서 유전율과 공진주파수의 온도계수는 점차 감소하였으나 Q값과 밀도는 47 mol% CaO조성에서 가장 낮았다. 이것은 이상 혼합 세라믹에서 TiO2상의 감소로 인해 CaTiO3의 결정립 성장이 급속하게 일어남으로써 입계와 입내에 큰 기공이 존재하지 때문으로 생각된다.

• 공업화학
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• 제18권4호
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• pp.314-319
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• 2007

UV, $O_3$, $H_2O_2$, $Fe^{2+}$ 등의 산화반응을 조합한 고급산화 공정(advanced oxidation process)을 이용하여 아세트산 분해실험을 수행하였다. 적용된 고급산화 공정은 $UV/H_2O_2$, $UV/H_2O_2/Fe^{2+}$, $O_3$, $O_3/H_2O_2$, $UV/O_3/H_2O_2$ 및 $UV/O_3/H_2O_2/Fe^{2+}$ 공정이었다. 낮은 pH (3.5)에서의 아세트산 분해율은 $UV/H_2O_2/Fe^{2+}$, $O_3/H_2O_2$, $UV/O_3/H_2O_2$ 및 $UV/O_3/H_2O_2/Fe^{2+}$ 공정은 비교적 높고, $UV/H_2O_2$와 $O_3$ 공정은 20% 이하로 낮게 나타났다. $O_3/H_2O_2$, $UV/O_3/H_2O_2$ 공정의 아세트산 분해율은 반응시간 180 min까지 반응시간에 따라 지속적으로 증가하였으나 $UV/H_2O_2/Fe^{2+}$, $UV/O_3/H_2O_2/Fe^{2+}$ 공정에서는 반응시간 90 min까지 아세트산 분해율이 급격히 증가한 후 그 이후에는 분해율의 증가가 미미하였다. 고급산화 공정별 아세트산 분해율은$UV/H_2O_2/Fe^{2+}$ 공정은 55%, $O_3/H_2O_2$ 공정 및 $UV/O_3/H_2O_2$ 공정은 66%, $UV/O_3/H_2O_2/Fe^{2+}$ 공정은 64%이었다.

• Environmental Engineering Research
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• 제16권3호
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• pp.131-136
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• 2011

The degradation of 30 pharmaceuticals and personal care products (PPCPs) subjected to $O_3$, $O_3$/UV, and $O_3/H_2O_2$ treatments were investigated using semi-batch tests and evaluated by their pseudo-first-order rate constants. The additional application of UV or $H_2O_2$ during $O_3$ treatment significantly improved the degradation rate of most of the PPCPs. At the same $O_3$ feed rate, $O_3$/UV treatment exhibited much higher PPCP degradation efficiency than that of $O_3$ treatment. This was probably due to degradation of the PPCPs by $O_3$, direct UV photodegradation, and OH radicals that formed from the photodegradation of $O_3$ during $O_3$/UV treatment. PPCP degradation by $O_3$ was also promoted by adding $H_2O_2$ during the $O_3$ treatment. However, when the initial $H_2O_2$ concentration was high during $O_3$ treatment, OH radicals were likely to be scavenged by excess $H_2O_2$, leading to low PPCP degradation. Therefore, it is important to determine the appropriate $H_2O_2$ dosage during $O_3$ treatment to improve PPCP degradation when adding $H_2O_2$ during $O_3$ treatment.

• 한국세라믹학회지
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• 제41권1호
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• pp.57-61
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• 2004

Zinc Oxide (ZnO)은 wurtzite 결정구조를 가지고 있으며, 밴드갭 에너지가 약 3.3eV로 반도성 산화물이다. $In_2O_3$이 첨가된 ZnO 박막을 점자빔증착법을 이용하여 1737F 유리기판에 제조하였다. $400^{\circ}C$의 증착온도에서 $In_2O_3$의 첨가량에 따른 ZnO 박막의 결정성, 미세구조를 비롯한 전기.광학적 특성을 조사하였다. 첨가되는 $In_2O_3$의 양에 따라 투명전도성 산화막으로써의 ZnO 박막의 특성이 변화되었다. $In_2O_3$의 첨가량이 감소할수록 비정질상에서 결정성의 ZnO 막을 얻을 수 있었다. 0.2at%의 $In_2O_3$가 첨가된 출발물질에서 제조된 $In_2O_3$-doped ZnO막은 약 $6.0 {\times} 10^{-3} {\Omega}cm$ 정도의 비저항값과 가시광선 영역에서 85% 이상의 광투과도를 나타내었다.

• 한국세라믹학회지
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• 제11권3호
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• pp.19-26
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• 1974

Mechanical properties of the system PbO-B2O3-V2O5 low melting glass during crystallization by heat-treatment were investigated. Wettability of the system PbO-B2O3-V2O5 was excellent and appropriate for commercial sealing as a low melting solder glass. Crystals, during heat-treated at 30$0^{\circ}C$ of the system PbO-B2O3-V2O5 were $\beta$-4PbO.B2O3, 5PbO.4B2O3, and Pb2V2O7 mainly. The percent of crystallinity was 82$\pm$5%. Mechanical properties of the system PbO-B2O3-V2O5 were influenced not only by the differences of density and coefficient of thermal expansion and the stress induced from the difference in the density and coefficient of thermal expansion between glass phase and crystals but also crystallization conditions.

• 대한화학회지
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• 제38권4호
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• pp.309-318
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• 1994

La$_2O_3$-변형 BaTi$O_3$의 안정한 결함구조와 단일상 영역을 X-선 회절분석기와 주사전자현미경을 사용하여 연구하였다. La$_2O_3$-변형 BaTi$O_3$의 안정한 결함구조는 La$^{3+}$ 이온이 격자구조내의 Ba$^{3+}$ 이온을 치환하고 Ti빈자리가 전하 불균형을 보상하기 위한 결함으로 생성된 [($Ba^x_{Ba})_{1-2x}(La{\cdot}_{Ba})_{2x}][Ti^x_{Ti})_{1-x/2}(V""_{Ti})_{x/2}]O_3$이다. 안정한 결함구조가 형성되도록 BaTi$O_3$에 La$_2O_3{\cdot}3/2TiO_3$를 혼입할 때 단위격자는 약 3 mol%가 혼입될 때부터 정방정에서 입방정으로 변하였고, 고용한계는 약 14 mol%이었다. La2$O_3{\cdot}3/2TiO_2$를 고용한계 이상으로 혼입할 때는 이차상으로 La_4Ba_2Ti_5O){18}$가 생성되었다. La$_2O_3$-변형 BaTi$O_3$ 조성에서 BaO가 과량 존재하면 소결성이 나쁘지만, Ti$O_2$가 과량으로 존재하면 액상소결에 의하여 소결성이 좋아짐을 확인할 수 있다.