• 제목/요약/키워드: pyrochlore phase

검색결과 122건 처리시간 0.035초

Miscut된 기판을 이용할 산화물 박막의 에피 성장 (Epitaxial growth of oxide films using miscut substrates)

  • 부상돈
    • 한국진공학회지
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    • 제13권4호
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    • pp.145-149
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    • 2004
  • RF magnetron sputtering 방법으로 miscut된 기판을 이용해서 양질의 압전 산화물 에피 박막을 제작하였다. 박막은 (001) $SrTiO_3$ 기판 위에 증착되었으며, (100) 방향으로 $0^{\circ}$-$8^{\circ}$의 miscut 각도를 갖는 기판들을 사용했다. $4^{\circ}$이상의 큰 miscut 각도를 갖는 기판 위에 성장된 박막의 경우, x-ray diffraction (XRD) 패턴은 perovskite 상의 순수한 PMN-PT 피크만을 보여 주었으며, wavelength dispersive x-ray fluorescence spectroscopy를 이용해서 분석한 조성비는 stoichiometric한 조성비에 가까운 값을 보여주었다. 반면에, miscut 각도가 없는 기판 위에 증착된 박막의 경우, 2차상인 pyrochlore 상을 포함하는 XRD 패턴을 보여주었다. $8^{\circ}$ 기판 위에 성장된 박막의 경우 실온에서 20$\mu$C/$\textrm{cm}^2$라는 높은 잔류분극 값을 보여주었다

졸-겔법에 의한 PLZT 박막의 결정화 및 균열 생성 (Crystallization and Crack Formation in Sol-Gel PLZT Thin Films)

  • 안기철;이전국;김호기;노광수
    • 한국세라믹학회지
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    • 제29권3호
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    • pp.216-222
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    • 1992
  • PLZT thin films were prepared using sol-gel spin coating. The films mainly consisted of perovskite phase when heat treated at 600$^{\circ}C$ and in O2 or air atmosphere for 2 hours after 7 coating cycles. Cracks were formed when smaller than after 9 coating cycles. When ITO interlayer existed between Corning 7059 glass substrate and the film, cracks were not formed after 9 coating cycles, but cracks were formed after 11 coating cycles because of large volume change of the film contracting on the substrate during the heat treatment. In the observation of microstructure, the thin films have perovskite phase of about 2 $\mu\textrm{m}$ grain size and pyrochlore phase of 100∼200${\AA}$ grain size.

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비오옴 ZnO 세라믹스의 형성과정에서 스피넬의 영향 (Effects of Spinel on the Formation Process of Nonohmic ZnO Ceramics)

  • 김경남;한상목
    • 한국세라믹학회지
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    • 제29권2호
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    • pp.101-106
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    • 1992
  • Sintering behavior, distribution of dopant oxides and electrical properties in the ZnO-Bi2O3-CoO-Sb2O3 and ZnO-Bi2O3-CoO-Sb2O3-Cr2O3 systems were studied. The linear shrinkage of ZnO varistors from 850 to 950$^{\circ}C$ was related to the decomposition reaction (py\longrightarrowsp+Bi2O3) of the pyrochlore phase. In the distribution of the dopant oxides (CoO, Sb2O3, Cr2O3), Co distribute uniformly throughout the sample, the distribution of Sb coincided with small particles (spinel phase, Zn7Sb2O12), and Cr distributed very consistently with Sb. The increase in breakdown voltage, due to the addition of Cr2O3, was not only attributed to the decrease in the ZnO grain size but also to the solution of Cr2O3 in the spinel phase. The leakage current (80% V60 ${\mu}\textrm{A}$) was increased by the addition of Cr2O3.

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Structure and Bonding of Perovskites A($Cu_{1/3}Nb_{2/3}$)$O_3$ (A=Sr, Ba and Pb) and their Series of Mixed Perovskites

  • Park Hyu-Bum;Huh Hwang;Kim Si-Joong
    • Bulletin of the Korean Chemical Society
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    • 제13권2호
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    • pp.122-127
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    • 1992
  • Some perovskites $A($Cu_{1}3}Nb_{2}3}$)O_3(A=$Sr^{2+}$$, $Ba^{2+}$ and $Pb^{2+}$) and their series of mixed perovskites have been prepared by solid state reaction. Single perovskite phase was obtained in Sr or Ba rich samples, but pyrochlore phase was found in Pb rich samples. The stability of perovskite phase is dependent on the ionicity of bonding as well as the tolerance factor. All the obtained perovskites have tetragonal symmetry distorted by Jahn-Teller effect of $Cu^{2+}$. In the case of $Sr(Cu_{1}3}Nb_{2}3})O_3$, some superlattice lines caused by threefold enlarging of fundamental unit cell were observed. And, the symmetry of B site octahedron and the bonding character of B-O bond have been studied by IR, ESR and diffuse reflection spectroscopy. It appeared that the symmetry and the bonding character are influenced by such factors as the size and the basicity of A cation.

3가 양이온 산화물이 첨가된 2Y-TZP의 저온 상안정성 (The Effect of Trivalent Cation Doping on the Low Temperature Phase Stability of 2Y-TZP)

  • 장주웅;김학관;이득용;김대준;박선민
    • 한국세라믹학회지
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    • 제39권11호
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    • pp.1055-1062
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    • 2002
  • 정방정 지르코니아의 상안정성 및 저온열화기구를 고찰하기 위해 Y2O3 안정화 지르코니아에 3가 양이온 산화물을 첨가한 후 그 소결체의 기계적 물성, 라만 스펙트럼 및 격자상수 변화 등을 관찰하였다. 2Y-TZP에 $Zr^{4+}$ 보다 이온크기가 큰 3가 양이온($Sc^{3+},\;Yb^{3+},\;Y^{3+},\;Sm^{3+},\;Nd^{3+},\;La^{3+}$)들을 2 mol%까지 첨가하여 $1500{\circ}C$에서 1시간 소결후, X-ray 상분석 결과 $La^{3+}$의 경우에는 0.5 mol% 이상 첨가시 pyrochlore 상$(La_2Zr_2O_7)$의 형성으로 정방정상의 상안정성이 저하되었다. 첨가량이 증가할수록 $Zr6{4+}$과 이온크기가 거의 비슷한 $Sc^{3+}$를 첨가한 경우에는 정방정상만 관찰되었으나 $Yb^{3+},\;Y^{3+},\;Sm^{3+},\;Nd^{3+}$를 첨가한 경우에는 입방정상이 형성되었다. 양이온 크기가 커질수록 c/a비는 증가하였으나 $220{\circ}C$에서 500시간까지 열처리후 상분석 결과 단사정량은 감소하였다.

Metal-citrate Process를 이용한 마이크로파 유전체용 (Pb0.5Ca0.5)(Fe0.5Nb0.5)O3 나노 분말의 저온 합성 (Low Temperature Synthesis of the Microwave Dielectric (Pb0.5Ca0.5)(Fe0.5Nb0.5)O3 Nano Powders by the Metal-citrate Process)

  • 이동욱;원종한;심광보;강승구;현부성
    • 한국세라믹학회지
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    • 제39권11호
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    • pp.1113-1118
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    • 2002
  • 마이크로파 유전체용 $(Pb_{0.5}Ca_{0.5})(Fe_{0.5}Nb_{0.5})O_3$ (PCFN) 나노 분말을 metal-citrate 공정을 이용하여 합성하였다. 금속 이온들과 유기 조직의 결합으로 이루어진 고분자 전구체를 형성시키고 이를 열처리하여 화학양론적 조성과 균일한 크기 분포를 갖는 PCFN 분말을 성공적으로 합성하였다. 초기 비정질상 PCFN 분말은 약 $400{\circ}$에서부터 결정화가 시작되어 $700{\circ}$에서 완전한 결정화를 이루었고, $900{\circ}$ 이상에서는 PbO의 해리로 인한 pyrochlore상이 생성되었다. $700{\circ}$에서 열처리된 단일상의 perovskite PCFN 분말은 약 40 nm의 평균 크기와 균일한 형상으로 분포되어 있었다.

이온주입이 PZT 박막의 결정화에 미치는 영향 (Effect of Ion Damage on the Crystallization of PZT thin films)

  • 박응철;이장식;박정호;이병일;주승기
    • 한국세라믹학회지
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    • 제37권5호
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    • pp.418-424
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    • 2000
  • Effects of Ar ion damage prior to the phase transformation from pyrochlore to perovskite structure of PZT thin films have been investigated. As the degree of damage increased by increasing the acceleration voltage in the ion mass doping system, the phase transformation temperature decreased such that the temperature could be lowered down to 550$^{\circ}C$ when the film was damaged at 15 kV for 5 minutes. When the film was damaged prior to the heat treatment grain size of the perovskite thin films became less than 300${\AA}$. It turned out that relatively high value of the remanent polarization (about 30${\mu}$C/$\textrm{cm}^2$) as well as improvement of the fatigue characteristics to a large extent is closely related to the fine grain size of thus obtained PZT films.

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졸-겔법으로 백금 기판위에 제조된 PLZT 박막의 구조적, 전기적 특성변화 (Structural and Electrical Characteristics of Ferroelectric PLZT Thin Film Prepared on Pt Substrate by Sol-Gel Route)

  • 오영제;김태송;정형진
    • 한국세라믹학회지
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    • 제31권2호
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    • pp.171-176
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    • 1994
  • The spin-casted PLZT(9/65/35) thin films through polymeric sol-gel process were prepared on Pt substrate. The crack-free, uniform and dense films were obtained by post-annealing at the temperature between 35$0^{\circ}C$ and $700^{\circ}C$. The composite structure mixed together with large grains called "rosette" and surrounding small grains were observed on the films annealed over $600^{\circ}C$. Pyrochlore phase was completely changed to perovskite phase above $600^{\circ}C$ with the increase of annealing temperature. Dielectric constant (k) was larger with the increase of film thickness and annealing temperature. from the measurements of dielectric constant as a function of measuring temperature, it was also observed that Curie temperature was shifted to higher temperature with the increase of film thickness and annealing temperature. The pyroelectric coefficient(P) of 10 times coated film annealed at $700^{\circ}C$ was 65 $\mu$C/$\textrm{cm}^2$.K.$.K.

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PZT-PNN-PZN계 세라믹스의 물리적 성질 (Physical Properties of PZT-PNN-PZN Ceramics)

  • 정수태;조상희;이우일
    • 한국세라믹학회지
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    • 제29권3호
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    • pp.183-188
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    • 1992
  • The physical properties of 0.5PZT-0.5(PNN-PZN) ceramics have been investigated as a function of PZN content. A pyrochlore phase exists in the range of 600∼850$^{\circ}C$ and a stable perovskite phase appears above 850$^{\circ}C$. The piezoelectric properties (except electro-mechanical coupling factor) of 0.5PZT-0.5(PNN-PZN) ceramics showed almost linear relationships of PZN content within the range of 0.5PZT-0.5PNN system and 0.5PZT-0.5PZN system. The temperature dependence of piezoelectric constant, the electric field dependence of induced strain and a bend strength are improved by addition of PZN.

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Pb(Zr, Ti)$O_3$ 박막에서 결정립 크기 포화 현상에 관한 연구 (A Study on the Saturation of Grain Size in Pb(Zr, Ti)$O_3$ Thin Films)

  • 이장식;김찬수;주승기
    • 한국세라믹학회지
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    • 제37권6호
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    • pp.530-536
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    • 2000
  • During the grain growth of the PZT thin films by selective nucleation method using PZT seed, it was found that the grain size was saturated with the annealing temperature. The saturation of grain size was analyzed by the interfacial energy which appeared during the crystallization. The factors affecting the saturation of grain size were found to be the interfacial energy between perovskite phase and pyrochlore phase, and PZT thin film and the bottom Pt electrode. When the ion damage was introduced to the grain-size saturated PZT thin films, further lateral growth was observed. Pt bottom electrode thickness was changed to control the interfacial energy between the PZT thin film and the Pt bottom electrode. When Pt thickness was increased, the grain size was also increased, because the lattice parameter of Pt films was increased with the thickness of the Pt films. The incubation time of nucleation was increased with the amount of the ion damage on the Pt films.

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