• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.371-374
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• 2002

Bismuth lanthanum titanate thin films with excess Bi contents were prepared onto Pt/Ti/$SiO_2$/Si substrate by metalorganic decomposition (MOD) technique. The structure and morphology of the films were analyzed using X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. From the XRD analysis, BLT thin films show polycrystalline structure and the layered-perovskite phase was obtained over 10% excess of Bi contents. As a result of ferroelectric characteristics related to the Bi content of the BLT thin film, the remanent polarization and dielectric constant decreased with increasing over Bi content of 10 % excess. The BLT film with Bi content of 10% excess was measured to have a dielectric constant of n9 and dielectric loss of 1.85[%]. The BLT thin films showed little polarization fatigue test up to 3.5 x $10^{9}$ bipolar switching cycling.

• Bulletin of the Korean Chemical Society
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• 제33권7호
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• pp.2305-2308
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• 2012

Perovskite structured barium titanate particles ($BaTiO_3$) platelets were synthesized by molten salt synthesis and topochemical microcrystal conversion. As the precursors of $BaTiO_3$, plate-like $BaBi_4Ti_4O_{15}$ particles were first synthesized by the reaction of $Bi_4Ti_3O_{12}$, $BaCO_3$, and $TiO_2$ at $1080^{\circ}C$ for 3 h in $BaCl_2$-KCl molten salt. After the topochemical reactions, layer-structured $BaBi_4Ti_4O_{15}$ particles transformed to the perovskite $BaTiO_3$ platelets. $BaTiO_3$ particles with thickness of approximately $0.5{\mu}m$ and a length of $10-15{\mu}m$ retained the morphology feature of the $BaBi_4Ti_4O_{15}$ precursor. For <001> $Pb(Mg_{1/3}Nb_{2/3})O_3-32.5PbTiO_3$ (PMNT)-5 wt % PbO piezoelectric ceramics textured with 5 vol % of $BaTiO_3$ templates, the Lotgering factor reached 0.82, and $d_{33}$ was 870 pC/N.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.76-76
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• 2009

PZT세라믹스는 높은 압전특성과 우수한 큐리온도($400^{\circ}C$)를 보유하고 있어 오래시간에 걸쳐 주목받고 있다. 현재 압전변압기, 액츄에이터, 센서등의 압전소자는 PZT를 이용하여 제작하고 있지만 PZT는 고온 소결시 PbO의 휘발이 환경오염을 초래하며 인체의 유해하다는 연구결과가 나왔다. 이에 최근에는 PbO가 포함 되지않은 무연(lead-free)계 압전세라믹스가 주목받고 있다. 무연 압전 세라믹스의 종류로는 Bi-layer-structured ceramics, Bi-perovskite type ceramics, NKN base ceramics 가 존재하고 있다. 그 중 $(Na_{0.5}K_{0.5})NbO_3(NKN)$ 세라믹스는 높은 큐리온도와($400^{\circ}C$)와 높은 전기기계 결합계수(약 36%)를 보유하고 있어 많은 연구가 이루어 지고 있다. 하지만 NKN은 PZT에 비하여 치밀성이 낮으며 일반적인 산화물 소결방법으로는 밀도를 높이기가 어려운 단점이 존재한다. 이를 개선하기 위한 방법으로 hot pressing와 spak plasma sintering, RTGG와 같은 방법으로 밀도를 높일수 있지만 비용이 많이 들어 일반적으로 사용이 어렵다. 다른 방법으로 NKN에 첨가물을 넣는 방법을 사용하고 있는데 방법으로 $LiNbO_3$, $LiTiO_3$, $LiSbO_5$를 첨가하여 개선하는 방법이 있다. 본 실험은 첨가물을 넣는 방식으로 비화학양론적 $(Na_{0.5}K_{0.5})_{0.97}(Nb_{0.9}Ta_{0.1})O_3(NKNT)$조성에 CuO를 mol%로 변화주어 유전 및 압전 특성을 조사하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
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• pp.817-820
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• 2004

The $Sr_{0.7}Bi_{2.6}Ta_2O_9$(SBT) thin films are deposited on Pt-coated electrode($Pt/TiO_2/SiO_2/Si$) using a RF magnetron sputtering method. The ferroelectric properties of SBT capacitors with annealing time were studied. In the SEM images, Bi-layered perovskite phase was crystallized at 10min and grains largely grew with annealing tune. SBT thin films are transformed from initial amorphous phase to the fully formed layer-structured perovskite. During the annealing process at $750^{\circ}C$, we found that an fluorite-like stage is formed after 3min. In the XRD pattern, the SBT thin films after 3min annealing time had (105) orientation. The ferroelectric properties of SBT capacitor with annealing time represent a favorable properties at 60 min. The maximum remanent polarization and the coercive electric field with 60 min are $12.40C/cm^2$ and 30kV/cm, respectively. The leakage current density with 60min is $6.81{\times}10^{-10}A/cm^2$.