• 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.
    • 한국전기전자재료학회논문지
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    • 제15권4호
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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.

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

  • 황구현;최종건
    • 한국결정성장학회지
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    • 제18권1호
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    • pp.22-26
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    • 2008
  • [ $CaCO_3$ ]와 $ZrO_2$를 모체결정으로 하고 Pr을 부활제로, 융제로 $B_2O_3$을 사용하였으며 고상반응법으로 합성하여 $CaZrO_3$ : Pr 적색 축광성 형광체를 제조하였다. XRD 분석을 통하여 시료의 결정상을 확인하였고, PL 검사를 통하여 $480{\sim}570nm$영역과 $590{\sim}700nm$ 영역의 발광 스펙트럼을 관찰하였다. 융제로서 $B_2O_3$을 각각 1%, 5%, 10%를 첨가하여 고상반응법으로 합성하였을 때, 494 nm 에서 발광은 $B_2O_3$의 농도가 1%일 때 가장 높은 강도를 나타냈다. 적색을 나타내는 620 nm에서의 Peak는 $B_2O_3$의 농도가 10%일 때 가장 높은 강도를 나타내었다.

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

  • 류제혁;문정인;박연경;;송정환;김택남
    • 한국재료학회지
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    • 제22권5호
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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.

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

  • 이현구
    • 자원환경지질
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    • 제32권3호
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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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$Na_2O-CaO-MgO-Al_2O_3-SiO_2$계 Glass-Ceramics에 있어서 Bulk Crystallization에 관한 연구 (The Study on the Bulk Crystallization in $Na_2O-CaO-MgO-Al_2O_3-SiO_2$ Glass-Ceramics)

  • 강원호;이정호
    • 한국결정성장학회지
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    • 제2권2호
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    • pp.20-32
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    • 1992
  • $Na_2O-CaO-MgO-Al_2O_3-SiO_2$계를 기본조성으로 하여 $Na_2O$$Li_2O 0.05wt%, $K_2O$를, CaO에 MgO 12.0wt%, ZnO 6.0%를 각각 치환하여 조성을 선정하였다. 기본 유리조성의 결정상은 wollastonite이고, 치환된 조성들은 diopside, diopside.tremolite의 혼정이 나타났다. $Na_2O$$Li_2O$로 치환한 시편은 열팽창계수가 감소하였지만 CaO를 ZnO로 치환한 시편은 열팽창 계수가 증가하였다. 곡강도에 있어서는 치환에 따라 모두 증가시켰다. 핵행성제로 $ZrO_2$CaF_2$를 각각 1~2wt%의 변화를 시켜본 결과 핵형성제 $ZnO_2$$CaF_2$가 1:1, 1:2인 시편은 $1000~1050^{\circ}C$온도에서 급격한 결정성장을 보였으며 1:2시편이 가장 낮은 열팽창 계수값을 나타냈다. 곡강도는 모두 $1000~1050^{\circ}C$의 결정화 온도 범위에서 높은 강도를 나타내었다. 결정화에 필요한 활성화 에너지는 Ozawa와 Kissinger식으로 plot하여 각각 55.24kcal/mol과 53.05kcal/mol이다.

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

  • 박용완;김용욱
    • 한국세라믹학회지
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    • 제29권3호
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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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하소공정과 $ZrO_2$ 첨가량이 $BaTiO_3$의 전기적 특성에 미치는 영향 (Effects of Calcination Process and $ZrO_2$ Addition on the Electrical Properties of $BaTiO_3$ Ceramics)

  • 차진이;박재관;오태성;김윤호
    • 한국세라믹학회지
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    • 제28권11호
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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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Ca-Ce-Zr-Ti-O System에서의 파이로클로어 합성 및 상관계에 대한 연구 (Study on Phase Relation and Synthesis of Pyrochlore in the System of Ca-Ce-Zr-Ti-O)

  • 채수천;배인국;장영남
    • 자원환경지질
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    • 제37권6호
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    • pp.603-612
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    • 2004
  • 고준위 폐기물 내에 함유된 핵종을 고정화시킬 수 있는 매트릭스로써 파이로클로어$(pyrochlore;\;CaCeZr_xTi_{2-x}O_7,\;x=0.2\~2.0)$를 합성하여 상평형 관계 및 특성을 연구하였다. 합성방법은 CPS법이었으며, $1100\~1600^{\circ}C$에서 20시간 동안 가열하였다. 실험결과, 최적 합성조건은 각각의 조성에 따라 $1300\~1600^{\circ}C$로 다양하였다. 최적 합성조건에서 파이로클로어 또는 형석구조를 나타내는 산화물(이하 '형석'으로 기재)은 소량의 페롭스카이트와 더불어 $CeO_2$ 또는 $Ce_{0.75}Zr_{0.25}O_2$와 공존하였다. 또한 원조성인 $CaCeZr_xTi_{2-x}O_7$$x\leq0.6$인 경우 파이로클로어 구조가, 그리고 $x\geq0.6$에서는 형석구조가 안정한 것을 확인하였다. 특히 x값의 증가에 따라, Ca 및 Ti 성분이 결핍되었으며, 이와는 대조적으로 Zr과 Ce가 초과됨으로써 비화학양론적 조성을 나타내었다. 이러한 특성은 팔배위와 육배위를 차지하고 있는 원소들의 거동에 의한 것으로, 파이로클로어 또는 형석이 단일상이 아니라 페롭스카이트, $CeO_2$$Ce_{0.75}Zr_{0.25}O_2$와 공존하는 원인이 된 것으로 사료된다.

$(Pb_{1-x}Ca_x)ZrO_3$$(Pb_{0.63},Ca_{0.37-x}M_x)ZrO_3$ 세라믹스의 고주파 유전 특성 (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)

  • 윤중락;이헌용
    • E2M - 전기 전자와 첨단 소재
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    • 제10권6호
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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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불순물 첨가에 따른 $(Ba,Sr,Ca)TiO_{3}$ 세라믹의 유전특성 (Dielectric Properties of $(Ba,Sr,Ca)TiO_{3}$ Ceramics with Additon of Dopant)

  • 이성갑;이영희;임성수;박인길
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
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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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