• Title, Summary, Keyword: $CeMnO_3$

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Dependence of Phase Stability of Tetragonal Zirconia Polycrystal on Dopants

  • Chon, Uong
    • The Korean Journal of Ceramics
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    • v.4 no.4
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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.

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Growth and Properties of Co-doped Ce,Mn:LiTaO3 Single Crystals

  • Gang, Bong-Hoon;Rhee, Bum-Ku;Lim, Ki-Soo;Bae, Sung-Ho;Joo, Gi-Tae
    • Journal of the Korean Ceramic Society
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    • v.39 no.8
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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.

Mechanism of Ce promoting SO2 resistance of MnOx/γ-Al2O3: An experimental and DFT study

  • Zhang, Xiaopeng;Li, Zhuofeng;Zhao, Jijun;Cui, Yuezong;Tan, Bojian;Wang, Jinxin;Zhang, Chengxiang;He, Gaohong
    • Korean Journal of Chemical Engineering
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    • v.34 no.7
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    • pp.2065-2071
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    • 2017
  • Various physico-chemical techniques and theoretical chemistry computations are used to obtain a deep insight into the mechanism of Ce improving $SO_2$ resistance of the catalyst $Mn_{0.4}Ce_x/Al_2O_3$ (x stands for the molar ratio of Ce : Al). Theoretical computation with density functional theory (DFT) shows that Ce modification enhances the adsorption energy of $SO_2$ adsorbed on Ce surrounding, resulting in the preferential adsorption of $SO_2$ on Ce surrounding. It protects the surface Mn from $SO_2$ poisoning, leading to a better $SO_2$ resistance. FT-IR and TG results are in good accordance with DFT results. FT-IR results suggest that absorption peaks related to $SO_4{^{2-}}$ cannot be detected in $Mn_{0.4}Ce_{0.12}/Al_2O_3$. Moreover, TG results show that weight loss peaks due to sulfated $MnO_x$ decomposition disappears after Ce addition. Therefore, Ce modification inhibits sulfates formation on active components lead to a better resistance to $SO_2$ of $Mn_{0.4}Ce_x/Al_2O_3$.

Microstructural property and catalytic activity of nano-sized MnOx-CeO2/TiO2 for NH3-SCR (선택적 촉매 환원법 재료로서 나노 사이즈 MnOx-CeO2/TiO2 촉매에 대한 미세 구조적 특성과 촉매활성 평가)

  • Hwang, Sungchul;Jo, Seung-hyeon;Shin, Min-Chul;Cha, Jinseon;Lee, Inwon;Park, Hyun;Lee, Heesoo
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.26 no.3
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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.

Microstructural Properties of (Pb)(La,Ce)$TiO_3$ ceramics as a function of $MnO_2$ addition ($MnO_2$ 첨가에 따른 (Pb)(La,Ce)$TiO_3$ 세라믹스의 미세구조특성)

  • Oh, D.U.;Min, S.K.;Yoon, K.H.;Yoo, J.H.;Park, C.Y.
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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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 $330^{\circ}C$

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Space Charge Effect on Grain Growth Kinetics of Tetragonal Zirconia Polycrystal

  • Chon, Uong
    • The Korean Journal of Ceramics
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    • v.5 no.1
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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.

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Dielectric and Piezoelectric Properties of Low Temperature Sintering PMW-PNN-PZT Substituted with CeMnO3 (CeMnO3가 치환된 저온소결 PMW-PNN-PZT 세라믹스의 유전 및 압전 특성)

  • Kim, Yong-Jin;Yoo, Ju-Hyun
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.28 no.3
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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.

Dielectric and Piezoelectric Properties of (Na0.5K0.5)0.97NbO3 Ceramics Substituted with CeMnO3 (CeMnO3 치환된 (Na0.5K0.5)0.97NbO3 세라믹스의 유전 및 압전 특성)

  • Oh, Young-Kwang;Yoo, Ju-Hyun;Mah, Suk-Burm;Jeong, Yeong-Ho
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.24 no.3
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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.

Physical Properties and Out-put Characteristics of Piezoelectric Transformer of $Pb(Mg, Te, Mn, Nb)O_3-PZT$ Ceramics with Addition of $CeO_2$ ($CeO_2$을 첨가한 $Pb(Mg, Te, Mn, Nb)O_3-PZT$계 세라믹스의 물리적 성질과 압전트랜스의 출력특성)

  • 박순태;정수태;이종헌
    • Journal of the Korean Ceramic Society
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    • v.30 no.9
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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.

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Cathodic Polarization of $La_{0.5}Sr_{0.5}MnO_{3-\delta}$ on $Ce_{0.8}Gd_{0.2}O_{1.9}$ Electrolyte ($Ce_{0.8}Gd_{0.2}O_{1.9}$ 전해질에서 $La_{0.5}Sr_{0.5}MnO_{3-\delta}$ 양극의 과전압특성)

  • 윤희성;노의범;김병호
    • Journal of the Korean Ceramic Society
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    • v.35 no.9
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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.

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