• The Korean Journal of Ceramics
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• 제4권4호
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• pp.297-303
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• 1998

The effect of aliovalent dopants, $ Nb_2O_5$ and MnO, on the phase stability of 12 mol% ceria partially-stabilized zirconia (Ce-TZP) polycrystals was studied. Both dopants (MnO and $ Nb_2O_5$) significantly increased the stability of the tetragonal zirconia phase (Mb temperature lower than liquid nitrogen temperature). The enhancement of the stability of the tetragonal phase in Ce-TZP doped with 1 mol% of Mno(Ce-TZP/MnO) andCe-TZP doped with 1 mol% of $ Nb_2O_5$(Ce-TZP/$ Nb_2O_5$) were explained by the significant reduction of the driving force, -${\Delta}$Gchem, for the tetragonal-to-mono-clinic phase transformation caused by the addition of MnO and $ Nb_2O_5$. The enhanced stability of the tetragonal phase in the Ce-TZP and Al2O3 composite (Ce-TZP/$Al_2O_3$) is believed to be caused by smaller grain size, moderate reduction in the chemical driving force and increase in the strain energy barrier to the transformation. Mechanical properties of the Ce-TZP and the Ce-TZP/$Al_2O_3$ with (i) the same grain size and (ii) the same Mb temperature were examined by measuring stress-strain behavior in 3 point bending. The Ce-TZP/$Al_2O_3$ composite doped with 1.3w% MnO (Ce-TZP/$Al_2O_3$/MnO), which had the same grain size as the Ce-TZP and De-TZP/$Al_2O_3$ showed more transformation plasticity than either the Ce-TZP or the Ce-TZP/$Al_2O_3$ composite. The Ce-TZP wihch had the same Mb temperature as that of the Ce-TZP/$Al_2O_3$/MnO did not show any transformation plasticity.

• Journal of the Korean Ceramic Society
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• 제39권8호
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• pp.711-714
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• 2002

The Ce, Mn: $LiTaO_3$ crystals were grown by Czochralski method in congruent ${\varphi}$3＂ $LiTaO_3$ single crystal growing conditions. Concentrations of Ce and Mn in melt were respectively 0.1 mole%. As-grown crystals were red, transparent and the grown crystals were tested with oxidation/reduction treatment for clor and other properties. Influence of Ce and Mn dopants on $LiTaO_3$ crystal properties was discussed. And the nonlinear optical properties of the Ce, Mn: $LiTaO_3$ crystal are being studied.

• Journal of the Korean Ceramic Society
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• 제35권9호
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• pp.981-987
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• 1998

$La_{0.5}Sr_{0.5}MnO_{3-\delta}$ as air electrode for soild oxide fuel cell was synthesized by a citrate process and its cathodic polarization was determinated by the current interruption method on the Gd-doped ceria as electrolyte. The addition of citric acid increased the exothermic heat for the formation of $La_{0.5}Sr_{0.5}MnO_{3-\delta}$ perovskite oxide. The degree of the initial particle agglomeration was affected by the exothermic heat. Also the increase of cal-cination temperature enlarged the particle size and the higher sintering temperature accelerated the den-sification of $La_{0.5}Sr_{0.5}MnO_{3-\delta}$ layer after its being painted on $Ce_{0.8}Gd_{0.2}O_{1.9}$ electrolyte. In this study $La_{0.5}Sr_{0.5}MnO_{3-\delta}$ synthesized by citrate process of which the molar ratio of citric acid to metal nitrate was 2 calcined at $650^{\circ}C$ for 2hr and sintered at 1100 at $1200^{\circ}C$ for 4 hrs after slurry coating on Ce0.8Gd0.2O1.9 electrlyte showed the lowest cathodic polarization.

• Proceedings of the Optical Society of Korea Conference
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• 한국광학회 2002년도 하계학술발표회
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• pp.96-97
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• 2002

불순물을 이용한 비휘발성 홀로그램저장[1,2]은 기존의 열정착을 광정착으로 대치하는 방법으로서 여러 가지 희토류 혹은 전이금속이온을 첨가한 LiMbO$_3$ (LNO) 단결정 재료에서 시도되고 있다. 대표적인 재료로서 Mn,Fe：LNO 가 있으나 Mn,Ce：LNO, Cu,Co：LNO, Tb,Fe：LNO 등도 연구되고 있고 Stoichiometric LNO 경우엔 Pr：LNO, Er：LNO, Tb：LNO 등이 연구되고 있다. 그 외에 Mn：YAlO$_3$도 약하긴 하지만 비휘발성이 최근 보고되었다. (중략)

• Journal of the Korean Crystal Growth and Crystal Technology
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• 제26권3호
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• pp.115-120
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• 2016

$CeO_2$ is used as a co-catalyst with $TiO_2$ to improve the catalytic activity of $MnO_x$ and characterization of nano-sized powder is identified with de-NOx efficiency. A comparison between $MnO_x-CeO_2/TiO_2$ and single $CeO_2$ was conducted in terms of microstructural analysis to observe the behavior of $CeO_2$ in the ternary catalyst. The $MnO_x-CeO_2/TiO_2$ catalyst was synthesized by sol-gel method and the average particle size of the single $CeO_2$ is about $285{\mu}m$ due to the low thermal stability, whereas the particle size $MnO_x-CeO_2/TiO_2$ is about 130 nm. The strong interaction between Ce and Ti was identified through the EDS mapping by transmission electron microscopy (TEM). The improvement about 20 % of $de-NO_x$ efficiency is observed in the low-temperature ($150^{\circ}C{\sim}250^{\circ}C$) and vigorous oxygen exchange by well-dispersed $CeO_2$ is the reason of catalytic activity improvement.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
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• pp.442-445
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• 2001

In this study, microstructural and dielectric properties of $Pb_{0.83}(La_{0.2}Ce_{0.8})_{0.08}TiO_3$(PCT) ceramics as a function of $MnO_2$ addition were investigated for 30MHz ceramic resonator application. Grain size was gradually increased according to the increase of $MnO_2$ addition amount and showed the highest value of $1.502{\mu}m$ at the 0.9wt% $MnO_2$. Moreover, density showed the highest value of $7.582 g/cm^3$ at the 0.7wt% $MnO_2$.All the composition ceramics,curie temperature was nearly constant around $330^{\circ}C$

• The Korean Journal of Ceramics
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• 제5권1호
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• pp.1-11
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• 1999

The effect of aliovalent dopents, $Nb_3O_5$ and MnO, on the grain growth kinetics of 12 mol% ceria stabilized tetragonal zirconia polycrystals (Ce-TZP) was studied. All specimens were sintered at $1550^{\circ}C$ for 20 minutes prior to annealing at different temperatures to study grain growth kinetics. Grain growth kinetics of Ce-TZP and 1 mol% $Nb_2O_5$ doped Ce-TZP (Ce-TZP/$Nb_3O_5$) during annealing at 1475, 1550, and $1600^{\circ}C$ adequately matched with square law $(D^2-D_\;o^2=k_at)$. However, grain growth in 1 mol% MnO suppressed grain growth in Ce-TZP by drag force exerted by $Mn^{+2}$ ions which segregated strongly to the positively-charged grain boundaries of Ce-TZP, $Nb_2O_5$ enhanced grain growth by increasing the concentration of vacancies of $Zr^{+4}$ ion and $Ce^{+4}$ ions. Surface analysis with X-ray photoelectron spectroscopy (XPS) showed the segregation of Mn+2 ions to grain boundaries. The kinetics of grain growth obtained in the base Ce-TZP and the Ce-TZPs with the aliovalent dopants were examined in the context of impurity drag effect and space charge effect.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• 제28권3호
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• pp.160-164
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• 2015

In this study, $(1-x)Pb(Mg_{1/2}W_{1/2})_{0.03}(Ni_{1/3}Nb_{2/3})_{0.09}(Zr_{0.5}Ti_{0.5})_{0.88}O_3+xCeMnO_3$ (x= 0~0.02) ceramics were prepared by Columbite precursor method. The phase structure, ferroelectric and piezoelectric properties were systematically investigated. It was found that PMW-PNN-PZT possessed superior electrical properties due to its composition close to the MPB (morphotropic phase boundary). Coercive electric field of 10.05 [kV/cm] and density of 7.88 [$g/cm^3$] were obtained when the substitution amount of $CeMnO_3$ is x=0.02. In contrast, specimens with x=0.01 showed the mechanical quality factor($Q_m$) of 1,091 and the electromechanical coupling factor($k_p$) of 0.613.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• 제24권3호
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• pp.194-199
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• 2011

In this study, non-stoichiometric 1-x$[(K_{0.5}Na_{0.5})_{0.97}(Nb_{0.96}Sb_{0.04})O_3]$ + x $CeMnO_3$ + 0.8 mol%CuO + 0.2 wt% $Ag_2O$ (x=0, 0.005) ceramics were prepared by a conventional mixed oxide and carbonate method, their dielectric and piezoelectric properties were investigated with the variations of sintering temperature. As $CeMnO_3$ substitution incereased, the density, piezoelectric constant($d_{33}$) and dielectric constant($\varepsilon_r$) were increased and the mechanical quality factor(Qm) was decreased. At the sintering temperature of $1100^{\circ}C$, the density, electromechanical coupling factor($k_p$), dielectric constant($\varepsilon_r$) and piezoelectric constant($d_{33}$) of 0.5mol% $CeMnO_3$ specimen showed the optimun values of 4.475 $g/cm^2$, 0.437, 552 and 166 pC/N, respectively. However, the mechanical quality factor($Q_m$) showed the minimum value of 380.

• Journal of the Korean Ceramic Society
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• 제30권9호
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• pp.761-767
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• 1993

Electrical and mechanical properties of Pb(Mg, Te, Mn, Nb)O3-PZT ceramics are investigated as a function of CeO2 addition (0 to 0.3wt%), and the output characteristics of piezoelectric transformer are also presented. The grain size decreased and the shapes of particles were more uniform with the addition of CeO2. The coercive electric field(9500V/cm), mechanical quality factor (2500) and bend strength (1065kg/$\textrm{cm}^2$) were improved by addition of CeO2 0.2wt%. After repetition of a number of stress cycles, the degradation of k33 was not found in this sample. The voltage step-up ratio (Vdc/Vrms) of piezoelectric ceramic transformer (half wavevoltage doubler, load resistor 100M.ohm) was about 950 in a linear region, its value was relatively higher than other materials.