• 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 2003년도 제5회 학술대회 논문집 일렉트렛트 및 응용기술연구회
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• pp.72-76
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• 2003

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 RF magnetron sputtering method. The structural and electrical properties of SBT capacitors were influenced with annealing atmosphere. In the XRD pattern, the SBT thin films in all annealed atmosphere had (105) orientation. In the SEM images, Bi-layered perovskite phase was crystallized in all annealing atmosphere and grains largely grew in oxygen annealing atmosphere. The maximum remanent polarization and the coercive electric field in oxygen annealing atmosphere are $12.40[{\mu}C/cm^2]$ and 30[kV/cm] respectively. The fatigue characteristics of SBT capacitors did not change up to $10^{10}$ switching cycles.

• 한국전기전자재료학회논문지
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• 제14권6호
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• pp.460-465
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• 2001

(Ba$_{0.6-x}$Sr$_{0.4}$Ca$_{x}$)TiO$_3$(x=1.10,0.15,0.20) specimens were fabricated by the solid state reaction method and then the structural and dielectric properties as a function of he composition ratio and sintering temperature were studied. As a result of the differential thermal analysis(DTA), exothermic peak was observed at around 102$0^{\circ}C$ due to the formation of the polycrystalline perovskite phase. The BSCT(50/40/10) specimen sintered at 150$0^{\circ}C$ showed the highest average grain size(18.25${\mu}{\textrm}{m}$). The Curie temperature and dielectric constant at room temperature decreased with increasing Ca content. The dielectric constant and dielectric loss of the BSCT(50/40/10) specimen, sintered at 145$0^{\circ}C$, were about 4324 and 0.972% at 1KHz, respectively.ively.

• 한국전기전자재료학회논문지
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• 제15권6호
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• pp.486-491
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• 2002

We have fabricated $Bi_{3.25}La_{0.75}Ti_3O_12$ (BLT) thin films on the Pt/Ti/$SiO_2$/Si substrates using a metalorganic decomposition (MOD) method with annealing temperature from $550^{\circ}C$ to $750^{\circ}C$. The structural properties of BLT films examined by x-ray diffraction (XRD). From XRD analysis. BLT thin films show polycrystalline structure. The layered-perovskite phase was obtained by spin-on films at above $600^{\circ}C$ for 1h. Scanning electron microscopy (SEM) showed uniform surface composed of rodlike grains. The grain size of BLT films increased with increasing annealing temperature. The BLT film annealed at $650^{\circ}C$ was measured to have a dielectric constant of 279, dielectric loss of 1.85(%), remanent polarization of $25.66\mu C/\textrm{cm}^2$, and coercive field of 84.75 kV/cm. The BLT thin films showed little polarization fatigue test up to $3.5{\times}10^9$ bipolar cycling at 5 V and 100 kHz.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1995년도 춘계학술대회 논문집
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• pp.14-16
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• 1995

Pb($Zr_{0.52}Ti_{0.48}$)$O_3$ ceramic thin films were fabricated from an alkoxide-based solution by Sol-Gel method. Pb($Zr_{0.52}Ti_{0.48}$)$O_3$ co-ramic thin films were formed by spin coating method on Pt/$SiO_2$/Si substrate at 4000[rpm] for 30 [sec]. Coated specimens were dried on the hot-plate at 400[$^{\circ}C$] for 10[min]. The coating process was repeated 6 times and then sintered at temperature between 500 ~ 800[$^{\circ}C$] for 1 hour. The ferroelectric perovskite phases precipitated under the sintering of 700[$^{\circ}C$] for 1 hour. Pb($Zr_{0.52}Ti_{0.48}$)$O_3$ thin film sintered at 700[$^{\circ}C$] for 1hour showed good dielectric constant (2133) and dielectric loss (2.2[%]) Properties. The switching voltage, switching time and leakage currents density were 3.0[V], 1.7[${\mu}$sec] , 160[pA/$\textrm{cm}^2$] repectively.

• 한국전기전자재료학회논문지
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• 제23권12호
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• pp.949-955
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• 2010

Nd and Ti co-doped bismuth ferrite $(Bi_{1-x}Nd_x)(Fe_{1-y}Ti_y)O_3$ (x, y = 0, 0.05, 0.1, 0.2) ceramics and thin films were synthesized through the conventional mixed-oxide process and pulsed laser deposition (PLD), respectively. Nd and Ti co-doping effect was examined with emphasis on how these impurities affect phase formation behavior as there could be the improvement in leakage current problems often associated with multiferroic $BiFeO_3$ (BFO) thin films. The lattice constants of BFO ceramics decreased with Nd doping concentration up to 10mol%, while they further decreased with Nd and Ti co-doping to about 20%. BFO thin films obtained by the PLD process revealed random polycrystalline structure. Similar to bulk BFO ceramic, Nd and Ti co-doping effectively suppressed the formation of unwanted secondary phase and thus stabilized the perovskite phase in BFO thin films.

• Transactions on Electrical and Electronic Materials
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• 제15권2호
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• pp.100-102
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• 2014

$Ag(Ta,Nb)O_3$ materials have a perovskite structure with a low loss tangent. These materials have been widely researched for their applications as high-frequency, passive components. Also, $Ag(Ta,Nb)O_3$ materials have weak frequency dispersion with high dielectric permittivity which gives them enormous potential for use in electronic components, including the filters, and embedded capacitors. Therefore, our research will discuss the structural and electrical relaxation properties of $Ag(Ta_{0.8}Nb_{0.2})O_3$ ceramics for device applications. We will investigate using X-ray diffraction to understand their structural properties and will analyze voltage dependent leakage current and timedependent relaxation behavior to understand their material properties.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.668-671
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• 2001

The Sr$\_$0.8/Si$\_$2.4/Ta$_2$O$\_$9/(SBT) thin films are deposited on Pt-coated electrode(Pt/TiO$_2$/SiO$_2$/Si) using RF magnetron sputtering method. With increasing post-annealing temperature from 600[$^{\circ}C$] to 850[$^{\circ}C$], Bi-layered perovskite phase was crystallized above 650[$^{\circ}C$]. The maximum remanent polarization and the coercive electric field is 11.60[${\mu}$C/$\textrm{cm}^2$], 48[kV/cm] respectively. The leakage current density of SBT capacitor at post-annealing temperature of 750[$^{\circ}C$] is 1.01${\times}$10$\^$-8/ A/$\textrm{cm}^2$ at 100[kV/cm]. The fatigue characteristics of SBT thin films did not change up to 10$\^$10/ switching cycles.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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• pp.589-592
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• 2002

The $Sr_{0.7}Bi_{2.3}Ta_2O_9$(SBT) thin films are deposited on Pt-coated electrode(Pt/TiO2/SiO2/Si) using RF magnetron sputtering method. The structural and electric properties of SBT capacitors were influenced with annealing atmosphere. In the XRD pattern, the SBT thin films in all annealing atmosphere had (105) orientation. In the SEM images, Bi-layered perovskite phase was crystallized in all annealing atmosphere and grains largely grew in oxygen annealing atmosphere. The maximum remanent polarization and the coercive electric field in oxygen annealing atmosphere are $12.40{\mu}C/cm^2$ and 48kV/cm respectively. The dielectric constant and leakage current density annealing in oxygen atmosphere are 340 and $6.81{\times}10^{-10}A/cm^2$ respectively. The fatigue characteristics of SBT capacitors did not change up to $10^{10}$ switching cycles.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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• pp.570-573
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• 2002

Pb(Zr0.52Ti0.48)O3 (PZT) thin films were deposited on the Pt/Ti bottom electrode by rf magnetron sputtering method from target containing 5%, 25% and 50% Pb excess for applying ferroelectric random access memory (FRAM). PZT films were deposited at $300^{\circ}C$ and then they were crystallized by rapid thermal annealing (RTA) at $700^{\circ}C$. After RTA treatment, our results showed that all PZT films indicated perovskite polycrystalline structure with preferred orientation (110) and no pyrochlore phase was observed by X-ray diffraction (XRD) and by Scanning electron microscopy (SEM). A well-fabricated PZT film of excess Pb 25% capacitor showed a leakage current density in the order of $2.63{\times}10^{-7}A/cm^2$ at 100kV/cm, a remanent polarization of $3.385{\mu}C/cm^2$ and a coercive field of 41.32 kV/cm. The results showed that Pb excess of target affects to electrical properties of PZT thin film.