• Korean Journal of Materials Research
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• v.10 no.1
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• pp.34-40
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• 2000

The $Pb_{0.94}Y_{0.04}[(Zr_{0.6}Sn_{0.4})_{0.915}Ti_{0.085}]O_3$ ceramics which corresponded to the antiferroelectric-ferroelectric phase boundary composition were prepared for digital-type-piezoelectric/electrostrictive device application. Their dielectric, field-induced polarization (P) and strain (X) behaviors were studied with variations in sintering condition and excess PbO content. The orthorhombic structure of specimens was hardly affected either by excess PbO addition or sintering temperature. With increasing excess PbO content, grains tended to be smaller and rounded ones, and the optimum sintering temperature was lowered. Excess PbO addition stabilized the antiferroelectric phase of the specimen effectively, which was confirmed by P-E and X-E analyses. Also the digital-type-strain character was found to be enhanced despite of slight increase in phase transition (AFE-FE) field and electrical resistivity, and decrease in maximum strain. These results were explained in terms of possible lattice defects and domain wall motion.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.7-12
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• 2004

탄화규소 전력반도체 소자는 실리콘 전력반도체 소자에 비해 우수한 물질특성을 갖고 있어 성능 측면에서 뿐 만 아니라 전력변환장비의 크기를 획기적으로 줄일 수 있는 새로운 반도체 소자이다. 특히 unipolar 계열의 소자에서 괄목할 만한 특성을 보이고 있다. 현재 쇼트키 장벽 다이오드의 경우 5kV급, UMOSFET의 경우 3kV급의 소자까지 보고되고 있으며 반도체 물질 중에서 가장 활발히 연구가 진행되고 있는 분야 중의 하나이다. 단결정성장 분야에서도 3인치 급이 상용화 되었으며 4인치 크기의 웨이퍼의 상용화가 조만간 실현될 것으로 기대되고 있다. 이러한 기술적 발전을 토대로 600V, 1200V급 쇼트키 다이오드가 PFC boost 용으로 시판되고 있으나 아직은 다른 반도체 소자에 비해 미미한 실정이다. 현재에는 $250^{\circ}C$까지의 온도영역에서 실리콘 SOI(Silicon on Insulator) 소자가 주로 사용되고 있다. 그러나 $300^{\circ}C$를 넘는 온도 영역에서는 실리콘으로는 한계가 있고, 특히 SOI는 전력소자에 적용하기는 한계가 있어 주로 저전력 고온소자가 필요한 부분에 적용이 되고 있다. 따라서 전력용에 적합한 고온소자로 탄화규소 소자의 연구가 활발히 진행되고 있다. 현재의 추세로 보아 $200-300^{\circ}C$ 영역의 응용분야에서는 SOI와 탄화규소가 함께 적용될 것으로 예상되며, $300^{\circ}C$를 넘는 온도영역에서는 탄화규소 소자의 우월적 지위가 예상된다. 이러한 이유로 탄화규소 반도체소자의 응용 분야는 크게 확대될 것으로 예상되며 국가적 차원의 지원 및 육성이 요구되는 분야 중의 하나이다.t로 사용한 소자보다 발광 소광 현상이 적게 일어난 것에 기인하였다고 생각된다. 두 소자 모두 $40mA/cm^2$ 에서 이상적인 화이트 발란스와 같은(0.33,0.33)의 색좌표를 보였다.epsilon}_0=1345$의 빼어난 압전 및 유전특성과 $330^{\circ}C$의 높은 $T_c$를 보였고 그 조성의 vibration velocity는 약4.5 m/s로 나타났다.한 관심이 높아지고 있다. 그러나 고 자장 영상에서의 rf field 에 의한 SAR 증가는 중요한 제한 요소로 부각되고 있다. 나선주사영상은 SAR 문제가 근원적으로 발생하지 않고, EPI에 비하여 하드웨어 요구 조건이 낮아 고 자장에서의 고속영상방법으로 적합하다. 본 논문에서는 고차 shimming 을 통하여 불균일도를 개선하고, single shot 과 interleaving 을 적용한 multi-shot 나선주사영상 기법으로 $100{\times}100$에서 $256{\times}256$의 고해상도 영상을 얻어 고 자장에서 초고속영상기법으로 다양한 적용 가능성을 보였다. 연구에서 연구된 $[^{18}F]F_2$가스는 친핵성 치환반응으로 방사성동위원소를 도입하기 어려운 다양한 방사성의 약품개발에 유용하게 이용될 수 있을 것이다.었으나 움직임 보정 후 영상을 이용하여 비교한 경우, 결합능 변화가 선조체 영역에서 국한되어 나타나며 그 유의성이 움직임 보정 전에 비하여 낮음을 알 수 있었다. 결론: 뇌활성화 과제 수행시에 동반되는 피험자의 머리 움직임에 의하여 도파민 유리가 과대평가되었으며 이는 이 연구에서 제안한 영상정합을 이용한 움직임 보정기

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.7
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• pp.511-515
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• 2012

A road energy harvester was designed and fabricated to convert mechanical energy from the vehicle load to electrical energy. The road energy harvester is composed of 24 piezoelectric cantilevers and a vehicle load transfer mechanism. Applying a vehicle load transfer mechanism rather than directly installing energy harvesters under roads decreases the area of road construction and allows more energy harvesters to be installed on the side of the road. The power generation amount with respect to the vehicular velocity change was assessed by installing the vehicle load transfer mechanism and the energy harvester in the form of speed bumps and underground. The energy harvester installed in a speed bump form generated power of 7.61 mW at the vehicular velocity of 20 km/h. Also, power generation of the energy harvester installed in the underground form was 63.9 mW at the vehicular velocity of 28 km/h. Although the number of piezoelectric cantilevers was reduced by 1/3 to 24 in comparison to the previous research results with 72 piezoelectric cantilevers, similar power generation characteristic value was obtained within the vehicular velocity of 20 km/h by altering the vehicle load transfer mechanism and cantilever vibration method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.194-194
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• 2008

Lead oxide based ceramics, represented by PZT, are the most widely used materials for piezoelectric actuators, sensors, and transducers due to their excellent piezoelectric properties. In particular, high-performance multilayered piezoelectric ceramics for advanced electronic components have drawn great attention. In order to develop piezoelectric ceramics capable of being sintered at low temperature for multilayer piezoelectric device applications, the effect of CuO additions on the microstructures and electromechanical properties of the 0.4Pb$(Mg_{1/3}Nb_{2/3})O_3-0.25PbZrO_3-0.35PbTiO_3$ ceramics was investigated. The samples with CuO addition were synthesized by ordinary sintering technique. X-ray diffractions indicated that all samples formed a single phase perovskite structure. The addition of CuO improved the sinterability of the samples and caused an increase in the density and grain size at low temperature. The optimum sintering temperature was lowered by CuO additions. Excellent piezoelectric and electromechanical responses, $d_{33}$ ~ 663 pC/N, $k_p$ ~ 0.72, were obtained for the samples of high density with 0.1 wt% CuO addition sintered at $1050^{\circ}C$ for 4 h in air. These results show that the piezoelectric properties of PMNZT ceramics can be improved by controlling the microstructure and this system is potentially a good candidate as multilayer piezoelectric device for a wide range of electro-mechanical transducer applications.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.1
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• pp.14-17
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• 2014

In this study, lead-free Piezoelectric $(Na_{0.47}K_{0.47}Sr_{0.03}Ca_{0.03})(Nb_{0.94}Ti_{0.06})O_3$-0.1 $MnO_2$ ceramics were fabricated using mixed oxide method and the effects of various sintering temperature on the structural and electrical properties were investigated. For the $(Na_{0.47}K_{0.47}Sr_{0.03}Ca_{0.03})(Nb_{0.94}Ti_{0.06})O_3$-0.1 $MnO_2$ (NKN-SCT-$MnO_2$) ceramics sintered at temperatures of $1,025{\sim}1,100^{\circ}C$. The results indicated that all specimens were perovskite single phase formation without any second phase. It has been shown that relative density is increased to increasing sintering temperature. When the sintered temperature at $1,075^{\circ}C$, highest sintered density and maximum value of $4.45g/cm^3$. Average grain size is increased to increasing sintering temperature. The electromechanical coupling factor, dielectric constant, dielectric loss, d33 and curie temperature at the sintering temperature $1,075^{\circ}C$ of NKN-SCT-$MnO_2$ specimens were 0.22, 511, 0.033, 103 and $380^{\circ}C$, respectively.

• Korean Journal of Materials Research
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• v.15 no.6
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• pp.413-418
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• 2005

Perovskite $Pb(Ni_{1/3}Nb_{2/3})O_3-Pb(Zr,Ti)O_3[PNN-PZT]$ ceramics were synthesized by conventional ceramic processing technique. In order to modify piezoelectric properties for sensor application in this system, NiO addition was considered to provide $Ni^{+2}$ as an acceptor, which was known to occupy with B site in the structure. The effect of NiO addition up to $8\;mol\%$ on the following piezoelectric properties as well as sintering properties was investigated. When NiO added more than $1\;mol\%$, average grain size was decreased and second phase was found to form. Moreover, the second phase caused decrease in relative dielectric constant $(\varepsilon_{33}T/\varepsilon0)$, electro-mechanical coupling factor $(k_p)$, and piezoelectric charge constant $(d_{33})$, while increasing mechanical quality factor $(Q_m)$. When $1\;mol\%$ NiO was added, density, dielectric properties and piezoelectric properties were abruptly increased.

• Journal of the Korean Society for Nondestructive Testing
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• v.14 no.4
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• pp.237-243
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• 1995

We have studied methods of detecting attenuation of solid materials such as silicon wafer and piezoelectric $LiTaO_3$ by means of optical probing techniques. We have performed measurements of surface acoustic waves(SAW) generated from 90 degree wedge type transducer and also from inter-digital transducers(IDT). SAW of 20.0 MHz was generated on a silicon wafer from the 90 degree wedge type transducer and those of 20.8 and 14.5 MHz are generated on a $LiTaO_3$ from the IDT. Then any surface-corrugation resulted from the above SAW was investigated by He-Ne laser beams. We projected laser beams, which were modulated by an optical chopper, on the SAW of the same frequency and then measured the scattered beam by the lock-in amplifier. We modulated and synchronized both SAW and the incident laser beam as well as the phase sensitive detector(PSD) to the same frequency in order to simplify our measurement system. We obtained the attenuation coefficients of SAW to be $0.62{\sim}0.75dB/mm$(from IDT1, 20.8 MHz), and $0.60{\sim}0.72dB/mm$(from IDT2, 14.5 MHz), $0.83{\sim}1.28dB/mm$(from the wedge type), respectively.

• Korean Journal of Materials Research
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• v.8 no.12
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• pp.1146-1151
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• 1998

The crystallization behaviour of perovskite $PbTiO_3$ for the samples heat- treated at various temperatures for various times in the $PbO-TiO_2-A1_2O_3-SiO_2$, glass system has been investigated by the means of X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. Higher crystallinity obtained in the sample heat-treated at higher temperature for longer time. With increasing heat-treatment time, dielectric constant of the samples heat-treated at $610^{\circ}C$ and $650^{\circ}C$ increased, but that of the sample heat- treated at $800^{\circ}C$ decreased. Loss tangent of the heat-treated samples was not much influenced by heat-treatment conditions. Piezodielectric charge constant was approximately $1.0\times10^{-12}~8.0$\times$10^{-12}C/N$ in the samples heat-treated at $800^{\circ}C$ for 1h, 2h, and 8h.

• Korean Journal of Materials Research
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• v.19 no.4
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• pp.198-202
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• 2009

For use in ultrasonic actuators, we investigated the structural and piezoelectric properties of $(1\;-\;x)Pb(Zr_{0.515}Ti_{0.485})O_3$ - $xPb(Sb_{1/2}Nb_{1/2})O_3$ + 0.5 wt% $MnO_2$ [(1 - x)PZT - xPSN + $MnO_2$] ceramics with a variation of x (x = 0.02, 0.04, 0.06, 0.08). All the ceramics, which were sintered at $1250^{\circ}C$ for 2 h, showed a typical perovskite structure, implying that they were well synthesized. A homogeneous micro structure was also developed for the specimens, and their average grain size was slightly decreased to $1.3{\mu}m$ by increasing x to 0.8. Moreover, a second phase with a pyrochlore structure appeared when x was above 0.06, which resulted in the deterioration of their piezoelectric properties. However, the 0.96PZT-0.04PSN+$MnO_2$ ceramics, which corresponds with a morphotropic phase boundary (MPB) composition in the (1 - x)PZT - xPSN + $MnO_2$ system, exhibited good piezoelectric properties: a piezoelectric constant ($d_{33}$) of 325 pC/N, an electromechanical coupling factor ($k_p$) of 70.8%, and a mechanical quality factor ($Q_m$) of 1779. The specimens with a relatively high curie temperature ($T_c$) of $305^{\circ}C$ also showed a significantly high dielectric constant (${\varepsilon}_r$) value of 1109. Therefore, the 0.96PZT - 0.04PSN + $MnO_2$ ceramics are suitable for use in ultrasonic vibrators.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.9
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• pp.581-588
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• 2016

Piezoelectric thick films of a soft $Pb(Zr,Ti)O_3$ (PZT) based commercial material were produced by a conventional tape casting method. Thereafter, the interdigitated (IDT) Ag-Pd electrode pattern was printed on the $25{\mu}m$ thick piezoelectric film at room temperature. Co-firing of the 10-layer laminated piezoelectric thick films was conducted at $1,100^{\circ}C$ and $1,150^{\circ}C$ for 1 h, respectively. Piezoelectric cantilever energy harvesters were successfully fabricated using the IDT electrode pattern embedded piezoelectric laminates for 3-3 operation mode. Their energy harvesting characteristics were investigated with an excitation of 120 Hz and 1 g under various resistive loads (ranging from $10k{\Omega}$ to $200k{\Omega}$). A parabolic increase of voltage and a linear decrease of current were shown with an increase of resistive load for all the energy harvesters. In particular, a high output power of 3.64 mW at $100k{\Omega}$ was obtained from the energy harvester (sintered at $1,150^{\circ}C$).