• Title/Summary/Keyword: $CaO-Y_{2}O_{3}-ZrO_{2}$

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Ionic Conductivity of Solid Solution Ceramics in The System of Stabilized ZrO2 Prepared by Self-Propagating High-Temperature Synthesis

  • Soh, Deawha;Korobova, N.
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.15 no.4
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    • pp.349-355
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    • 2002
  • The ionic conductivity of cubic solid solutions in the systems of CaO-$ZrO_2$, $Y_2O_3-ZrO_2$ prepared by SHS was examined. The higher conductivity appears to be related to a lower activation energy rather than to the number of oxygen vacancies dictated by composition. Conductivity-temperature data was obtained at 1000 $^{\circ}C$ in atmosphere of low oxygen partial pressure (~$10^{-40}$ atm) for $Y_2O_3-ZrO_2$ cubic solid solutions. The data indicated that these materials could be reduced, and the decree of reduction would be related with the measuring electric field.

A study on the luminescence characterization of red long persistent phosphors by the $B_2O_3$ addition ($B_2O_3$ 첨가에 의한 적색 축광성 형광체의 발광특성에 관한 연구)

  • Hwang, Ku-Hyeon;Choi, Jong-Koen
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.18 no.1
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    • pp.22-26
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    • 2008
  • Red long persistent phosphors of $CaZrO_3$ : Pr was synthesized by a solid reaction method. $CaCO_3\;and\;ZrO_2$ were used as hosting materials and Pr was doped as luminescence center element, and $B_2O_3$ was used as flux. The XRD pattern confirmed crystalline phase of the phosphor, and photoluminescence investigation showed emission spectrum at $480{\sim}570nm\;and\;590{\sim}700nm$. Phosphor samples were synthesized with $B_2O_3$ flux concentration of 1, 5, 10%, and luminescent peak of maximum intensity at 494 nm was obtained for 1% $B_2O_3$. Luminescent peak of red color at 620 nm was of highest intensity for 10% $B_2O_3$.

Hydrothermal Synthesis and Structural Characterization of x mol% Calcia-Stabilized ZrO2 Nanopowders (x mol% 칼시아-안정화 지르코니아 나노분말의 수열합성 및 구조적 특성평가)

  • Ryu, Je-Hyeok;Moon, Jung-In;Park, Yeon-Kyung;Nguyen, Tuan Dung;Song, Jeong-Hwan;Kim, Taik-Nam
    • Korean Journal of Materials Research
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    • v.22 no.5
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    • pp.220-226
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    • 2012
  • Pure zirconia and $x$ mol% calcia partially stabilized zirconia ($x$ = 1.5, 3, and 8) nanopowders were synthesized by hydrothermal method with various reaction temperatures for 24 hrs. The precipitated precursor of pure zirconia and $x$ mol% calcia doped zirconia was prepared by adding $NH_4OH$ to starting solutions; resulting sample was then put into an autoclave reactor. The optimal experimental conditions, such as reaction temperatures and times and amounts of stabilizer CaO, were carefully studied. The synthesized $ZrO_2$ and $x$ mol% CaO-$ZrO_2$ ($x$ = 1.5, 3, and 8) powders were characterized by XRD, SEM, TG-DTA, and Raman spectroscopy. When the hydrothermal temperature was as low as $160^{\circ}C$, pure $ZrO_2$ and $x$ mol% CaO-$ZrO_2$ ($x$ = 1.5 and 3) powders were identified as a mixture of monoclinic and tetragonal phases. However, a stable tetragonal phase of zirconia was observed in the 8 mol% calcia doped zirconia nanopowder at hydrothermal temperature above $160^{\circ}C$. To observe the phase transition, the 3 mol% CaO-$ZrO_2$ and 8 mol% CaO-$ZrO_2$ nanopowders were heat treated from 600 to $1000^{\circ}C$ for 2h. The 3 mol% CaO-$ZrO_2$ heat treated at above $1000^{\circ}C$ was found to undergo a complete phase transition from mixture phase to monoclinic phase. However, the 8 mol% calcia doped zirconia appeared in the stable tetragonal phase after heat treatment. The result of this study therefore should be considered as the preparation of 8 mol% CaO-$ZrO_2$ nanopowders via the hydrothermal method.

Geochemical Dispersion and Enrichment of Fluvial Sediments Depending on the Particla Size Distribution (입도분포에 따른 하상퇴적물의 지구화학적 분산 및 부화)

  • 이현구
    • Economic and Environmental Geology
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    • v.32 no.3
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    • pp.247-260
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    • 1999
  • Geochermical characteristics of the fluvial sediments deprnding on particle size distribution size were investigated in the respect of majir, minor and rare eath element chemisitry. Ratios of $Al_{2}O_{3}/Na_{2}O$ and $K_{2}O/Na_{2}O$ of the sediments show the homogeneous valus, and partly positive correlation with $SiO_{2}/Al_{2}O_{3}$, respecively. Characteristics of minor element ratios (V/Ni, Cr/V, Ni/Co and Zr/Hf)are within the lower and narrow range. Thesesuggested that sediment sources may be acidic to intermediate granitic rock, and may be explained by simple weathering and sedimentation. With increasing SiO2 contents, concentrations of $Al_{2}O_{3}$, $Fe_{2}O_{3}$, CaO and MgO decreased, but those of $K_{2}O$ and $Na_{2}O$ increased, Concentrations of Ba, Be, Cs, Cu, Li, Ni, Sr, V and Zr show comparatively normal negative and some positive trends. Compared with the mean composition of granite, concentrations of $Al_{2}O_{3}$, $Fe_{2}O_{3}$, MnO, CaO and MgO in the sediments of the study area were highly enriced. Among some minor and rare earth elements, concentrations of As, Cd, Cu, and V were enriched, but those of Be, Ce, Rb, Sc, Sr and Zn were depleted when compared with average composition of granite. By decreasing of particle size fractions, SiO2, Rb and Sr conterts decreased, but concentrations of $Al_{2}O_{3}$, $Fe_{2}O_{3}$, CaO, MgO, $TiO_{2}$, MgO, $P_{2}O_{5}$, Be, Cu, Hf, Pb, V and Zr increased. From the correlations between particle size fractions and element concenreations, some elements of $Fe_{2}O_{3}$, CaO, MgO, $P_{2}O_{5}$, Cu, Ni, Zn and Zr showed typical trends in the secondary contramination sediments. These trends are typically shown under 100 mesh fractions. It indicates that the fraction of minus 100 mesh is the optimum size fraction for geochemical and environmental survey.

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The Study on the Bulk Crystallization in $Na_2O-CaO-MgO-Al_2O_3-SiO_2$ Glass-Ceramics ($Na_2O-CaO-MgO-Al_2O_3-SiO_2$계 Glass-Ceramics에 있어서 Bulk Crystallization에 관한 연구)

  • 강원호;이정호
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.2 no.2
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    • pp.20-32
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    • 1992
  • $Na_2O-CaO-MgO-Al_2O_3-SiO_2$ glass was taken as a basic glass and then $Li_2O$ O.5wt%, $K_2O$ 2.0wt% were substituted to $Na_2O$content, MgO 12.0wt %, ZnO 6.0wt % to CaO content. And also nucleation agent $ZrO_2 and $CaF_2$ were added to 1-2wt% respectively. The crystal according to the compositions appeared wollastonite, diopside and diopside.tremolite. The glasses substituted NazO by LizO was decreased thermal expansion coeffcient but substituted by ZnO was opposite direction and both of them increased bending strength. In the ratio of ZrOz to CaF, each 1: 1 and 1: 2 have shown considerable crystal growth at $1000^{circ}C~1050^{\circ}C$ and high bending strength, but the glass in the ratio 1: 2 have shown lowest thermal expansion coefficient. The activation energy was at the glass in the ratio of ZrO, to CaFz 1:2 evaluated 55.24kvsl/mol by Ozawa type and 53.05kal/mol by kissinger type.

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A Study on the Transparent Glass-Ceramics On Al2O3-SiO2 System (투명 결정화 유리에 관한 연구 - $Al_2O_3-SiO_2$계에 관하여)

  • 박용완;김용욱
    • Journal of the Korean Ceramic Society
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    • v.29 no.3
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    • pp.223-231
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    • 1992
  • CaO and ZnO were added to Al2O3-SiO2 binary system respectively as flux, then ZrO2 and TiO2 were applied as nucleating agent to these CaO-Al2O3-SiO2 and ZnO-Al2O3-SiO2 ternary system glass. The transparency could not be kept in CaO-Al2O3-SiO2 system glass, whereas the transparent glass-ceramics were prepared in ZnO-Al2O3-SiO2 system glass containing ZrO2 as the nucleating agent. At this time the optimum heating temperatures for the nucleation and the crystal growth were 78$0^{\circ}C$ and 97$0^{\circ}C$. The sizes of the precipitated crystals in the transparent glass-ceramics were below 0.1 ${\mu}{\textrm}{m}$, and their light transmissibilities were more than 80%.

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Effects of Calcination Process and $ZrO_2$ Addition on the Electrical Properties of $BaTiO_3$ Ceramics (하소공정과 $ZrO_2$ 첨가량이 $BaTiO_3$의 전기적 특성에 미치는 영향)

  • 차진이;박재관;오태성;김윤호
    • Journal of the Korean Ceramic Society
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    • v.28 no.11
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    • pp.935-941
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    • 1991
  • Effects of calcination process and ZrO2 addition on the electrical properties of [(Ba0.82Sr0.08Ca0.1)O]m(Ti1-$\chi$Zr$\chi$)O2 ceramics have been investigated. With the variation of A/B-site ratio m of the dielectric formulations, sintering behavior and the resistivity after sintering in a reducing atmosphere have been affected by the calcination process. When the dielectric formulations of m=1.01 were sintered in a reducing atmosphere, the room-temperature resitivity of 109 {{{{ OMEGA }}.cm was obtained for samples processed with two-step calcination, which was much lower than 1012 {{{{ OMEGA }}.cm of samples calcined once. It was confirmed that high resistivity of Ca-doped BaTiO3 ceramics, after sintering in a reducing atmosphere, is maintained by acceptor-like behavior of CaTi" which is formed by Ca substitution to Ti-site. It was also found out that the critical amount of B-site Ca substitution for reduction inhibition of BaTiO3 is around 0.005 mol. With the increasing amount of ZrO2 addition to dielectric formulations, Curie peak was depressed and Curie temperature was lowered due to the enhanced diffuse phase transition.tion.

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Study on Phase Relation and Synthesis of Pyrochlore in the System of Ca-Ce-Zr-Ti-O (Ca-Ce-Zr-Ti-O System에서의 파이로클로어 합성 및 상관계에 대한 연구)

  • Chae Soo-Chun;Bae In-Kook;Jang Young-Nam;Yudintsev S.V.
    • Economic and Environmental Geology
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    • v.37 no.6 s.169
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    • pp.603-612
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    • 2004
  • Pyrochlore is known as one of the most promising materials for the immobilization of radionuclide in high level waste. This study included the synthesis, phase relation and characteristics of $pyrochlore(CaCeZr_xTi_{2-x}O_{7,\;x=0.2\~2.0)$ in the system of Ca-Ce-Zr-Ti-O. Using the CPS(Cold pressing and sintering) method, the mixtures of $CaCO3_,\;CeO_2,\;ZrO_2\;and\;TiO_2$ oxides were pressed, and sintered at $1100\~1600^{\circ}C$ for 20 hours. The optimal synthetic conditions at various compositions were differed from 1300 to $1600^{\circ}C$ Even in the optimal temperatures, pyrochlore or fluorite coexisted with minor amount of perovskite, $CeO_2\;or\;Ce_{0.75}Zr_{0.25}O_2$. It was confirmed that pyrochlore and fluorite structures were stable at $x\leq0.6\;and\;x\geq1.0$, respectively. Especially, the compositions of pyrochlore or fluorite showed non-stoichiometric compositions in that contents of Ca and Ti were more deficient and those of Zr and Ce were more excess than batch compositions with the increase of x value. These characteristics stemmed from the behavior of elements occupied at eight- and six-coordinated site, and then caused the coexistence of perovskite, $CeO_2\;or\;Ce_{0.75}Zr_{0.25}O_2$ along with pyrochlore or fluorite.

Microwave Dielectric Properties of $(Pb_{1-x}Ca_x)ZrO_3$ and $(Pb_{0.63},Ca_{0.37-x}M_x)ZrO_3$ (M = Mg, Sr) Ceramics ($(Pb_{1-x}Ca_x)ZrO_3$$(Pb_{0.63},Ca_{0.37-x}M_x)ZrO_3$ 세라믹스의 고주파 유전 특성)

  • 윤중락;이헌용
    • Electrical & Electronic Materials
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    • v.10 no.6
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    • pp.533-540
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    • 1997
  • The microwave dielectric properties of ((P $b_{1-x}$ C $a_{x}$)Zr $O_3$ and (P $b_{0.63}$,C $a_{0.37-x}$ $M_{x}$)Zr $O_3$(M=Mg,Sr) ceramics were investigated. In (P $b_{1-x}$ C $a_{x}$)Zr $O_3$ (X=0.33~0.40) ceramics, high quality factor and small temperature coefficient of resonant frequency were obtain in (P $b_{0.63}$C $a_{0.37}$)Zr $O_3$with perovskite structure. In the case of (P $b_{0.63}$C $a_{0.37-x}$M $g_{x}$)Zr $O_3$ dielectric constant temperature coefficient of resonant frequency increased and quality factor decreased due to increase of polarization of A-O bonding. When replacing Ca ion with Sr ion with large ion radius, polarization decreased with increased of bonding length and thus dielectric constant and temperature coefficient of resonant frequency decreased.decreased.creased.

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Dielectric Properties of $(Ba,Sr,Ca)TiO_{3}$ Ceramics with Additon of Dopant (불순물 첨가에 따른 $(Ba,Sr,Ca)TiO_{3}$ 세라믹의 유전특성)

  • Lee, Sung-Gap;Lee, Young-Hie;Lim, Sung-Soo;Park, In-Gil
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2001.11b
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    • pp.42-45
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    • 2001
  • $(Ba_{0.6}Sr_{0.4}Ca_{x})TiO_{3}+yZrO_{2}$ wt% (x=0.10, 0.15, 0.20, y=0.5~3.0) specimens were fabricated by the mixed-oxide method and then the structural and dielectric properties as a function of the composition ratio and $ZrO_2$ contents were studied. All BSCT specimens showed dense and homogeneous structure without the presence of the seconds phase. The Curie temperature and the dielectric constant at room temperature decreased with increasing the Ca/Ba composition ratio and $ZrO_2$ content. The BSCT(50/40/10) specimens showed the excellent tunability property. And the tunability were increased with increasing the contents of $ZrO_2$.

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