• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1439-1441
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• 2001

In this paper, the piezoelectric and dielectric properties as a function of x and r in $yPbZr_xTi_{1-x}O_3-(1-y)Pb(Mn_{1/3}Nb_{2/3})O_3$ piezoelectric ceramics is investigated. As a results, when y is 0.95 and x is 0.505, electromechanical coupling factor($k_p$), permittivity(${{\varepsilon}_{33}}^T/{\varepsilon}_0$), piezoelectric strain constant($d_{33}$) and mechanical quality factor($Q_m$) are 58[%], 1520, 272 [pC/N] and 1550, respectively. From XRD analysis, when x is 0.505, it is MPB which present rhombohedral and tetragonal phase in same quantity. Also, From SEM observation. when sintering temperature is 1150[$^{\circ}C$], grain size is about 2 [${\mu}m$]. As y decreases, piezoelectric and dielectric properties and curie temperature decreases, but mechanical quality factor and sintering temperature increases.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.160-161
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• 2009

In this study, in order to develop the lead free piezoelectric ceramics with excellent piezoelectric properties, (Na,K)$NbO_3$ ceramics according to the amount CuO addition were fabricated using a conventional mixed oxide process and their piezoelectric and dielectric characteristics were investigated. At the 0.8mol% CuO added composition, density, electromechanical coupling factor(kp), echanical quality factor(Qm), dielectric constant$(\varepsilon_r$) and piezoelectric constant($d_{33}$) showed the optimum value of $4.459g/cm^3$, 0.469, 540, 410, 69.57pC/N, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.181-182
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• 2005

In this study, in order to develop multilayer piezoelectric transformer, PMN-PZT ceramics were fabricated according to PFW substitution using $Li_2CO_3-CaCO_3$ as sintering aids and their dielectric and piezoelectric characteristics were investigated. As increasing the amount of PFW substitution, density was slightly increased due to the increased sinterability. At the 1[mol%] PFW substituted PMN-PZT ceramic sintered at 950[$^{\circ}C$], density, dielectric constant $\varepsilon_r$, electromechanical coupling factor kp, mechanical quality factor Qm and piezoelectric $d_{33}$ constant showed the optimum value of 7.761[$g/cm^3$], 1251, 0.479, 1425 and 282[pC/N], respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.6
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• pp.455-459
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• 2001

In this paper, the dielectric and pizoelectric properties of 0.05Pb(M $n_{04}$ $W_{0.2}$N $b_{0.4}$) $O_3$-0.95(PbZ $r_{x}$ $Ti_{1-x}$ ) $O_3$+yN $b_2$ $O_{5}$ , are investigated as a function of the mole ratio of Zr and the amount of N $b_2$ $O_{5}$ . Also, the phase is analyzed by XRD. When the mole ratio of Zr is 0.51, the electromechanical coupling coefficient( $k_{p}$ ), relative dielectric constant ($\varepsilon$$^{T}$ $_{33}$ /$\varepsilon$$_{0}$ ), piezoelectric stain constrain ( $d_{33}$ and dielectric loss tangent show maximum, while the mechanical quality factor shows minimum value ; $k_{p}$ =56.5%, $d_{33}$ =258pC/N, $\varepsilon$$^{T}$ $_{33}$ /$\varepsilon$$_{0}$ =1170, $Q_{m}$ =1150, tan$\delta$=0.51%. At that composition, MPB which rhombohedral and tetragonal phase coexist in this ternary system is shown by the results of XRD analysis. Also, when the amount of N $b_2$ $O_{5}$ is 0.3wt%, the mechanical quality factor is increased to about 2000. The phase transition temperature of the ternary piezoelectric ceramic system showed about 35$0^{\circ}C$.TEX>.>.>.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.219-219
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• 2008

Energy harvesting from the environment has been of great interest as a standalone power source of wireless sensor nodes for ubiquitous sensor networks (USN). There are several power generating methods such as thermal gradients, solar cell, energy produced by human action, mechanical vibration energy, and so on. Most of all, mechanical vibration is easily accessible and has no limitation of weather and environment of outdoor or indoor. In particular, the piezoelectric energy harvesting from ambient vibration sources has attracted attention because it has a relative high power density comparing with other energy scavenging methods. Through recent advances in low power consumption RF transmitters and sensors, it is possible to adopt a micro-power energy harvesting system realized by MEMS technology for the system-on-chip. However, the MEMS energy harvesting system hassome drawbacks such as a high natural frequency over 300 Hz and a small power generation due to a small dimension. To overcome these limitations, we devised a novel power generator with a spiral spring structure. In this case, the energy harvester has a lower natural frequency under 200 Hz than a normal cantilever structure. Moreover, it has higher an energy conversion efficient because shear mode ($d_{15}$) is much larger than 33 mode ($d_{33}$) and the energy conversion efficiency is proportional to the piezoelectric constant (d). We expect the spiral type MEMS power generator would be a good candidate as a standalone power generator for USN.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.9
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• pp.555-560
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• 2014

In this paper, in order to develop outstanding Pb-free composition ceramics, the $Fe_2O_3$-doped ($Na_{0.525}K_{0.443}Li_{0.037}$)($Nb_{0.883}Sb_{0.08}Ta_{0.037}$)$O_3$ + 0.3 wt% $Bi_2O_3$ + x wt% $Fe_2O_3$ (x= 0~1.0 wt%)(abbreviated as NKL-NST) lead-free piezoelectric ceramics have been synthesized using the ordinary solid state reaction method. The effect of $Fe_2O_3$-doping on their microstructure and electrical properties were investigated. XRD diffraction pattern studies confirm that $Fe_2O_3$ completely diffused into the NKL-NST lattice to form a new stable soild solution with $Fe^{3+}$ entering the $Nb^{5+}$, $Sb^{5+}$ and $Ta^{5+}$ of B-site. And, phase structure of all the ceramics exhibited pure perovskite phase and no secondary phase was found in the ceramics. The ceramics doped with 0.6 wt% $Fe_2O_3$ have the optimum values of piezoelectric constant($d_{33}$), planar piezoelectric coupling coefficient($k_p$) and mechanical quality factor($Q_m$) : $d_{33}$ = 233 [pC/N], $k_p$= 0.44, $Q_m$= 95. These results indicate that the ($Na_{0.525}K_{0.443}Li_{0.037}$)($Nb_{0.883}Sb_{0.08}Ta_{0.037}$)$O_3$ +0.3 wt% $Bi_2O_3$ + 0.6 wt% $Fe_2O_3$ ceramic is a promising candidate for lead-free piezoelectric ceramics.

• Journal of Sensor Science and Technology
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• v.19 no.2
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• pp.155-159
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• 2010

0.96$(Na_{0.5}K_{0.5})NbO_3$-0.04$(Ba_{(1-x)}Sr_x)TiO_3$ lead free piezoelectric ceramics were synthesized to enhance the piezoelectric properties of (Na,K)$NbO_3$. The systhesis and sintering method were the conventional solid state reaction method and general sintering method in air atmosphere. The polymorphic phase transition(PPT) was observed at all composition(0 $\leq$ x $\leq$ 0.05) when $(Ba_{(1-x)}Sr_x)TiO_3$ were added in the $(Na_{0.5}K_{0.5})NbO_3$. As Sr concentration was increased, grain size, dielectric loss(tan$\delta$) and mechanical quality factor($Q_m$) were decreased and piezoelectric constant($d_{33}$) and electromechanical coupling factor($k_p$) were increased within a limited value. The optimized piezoelectric and properties, $d_{33}$, $k_p$, $Q_m$, and tand, of 0.96$(Na_{0.5}K_{0.5})NbO_3$-0.04$(Ba_{(1-x)}Sr_x)TiO_3$ were 139 pC/N, 0.31 %, 95, 0.04 at the composition of x=0.04.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.68-69
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• 2005

Low temperature ($\leq900^{\circ}C$) sintering piezoelectric ceramics $0.01Pb(Mg_{1/2}W_{1/2})O_3$-0.41Pb$(Ni_{1/3}Nb_{2/3})O_3-0.35PbTiO_3-0.23PbZrO_3+0.1wt%Y_2O_3+xwt%ZnO$ $(0{\leq}x{\leq}2.5)$ have been developed and investigated. The electromechanical coupling coefficient ($k_p$), piezoelectric constant ($d_{33}$), and mechanical quality factor ($Q_m$) have been measured to characterize the piezoelectric materials system. When 2.0 wt% ZnO is added, the properties of the system, $d_{33}$ = 559 pC/N, $k_p$ = 55.0 % and $Q_m$ = 73.4 are obtained which are very suitable for piezoelectric actuators. A bending mode multilayer actuator has been also developed using the materials which size is $27(L)\times9(W)\times1.07(t)mm^3$. The actuators are fabricated by multilayer ceramic (MLC) process and consist of24 layers and each layer thickness is $35{\mu}m$. At this time, the displacement of actuator was $100{\mu}m$ at 28V.

• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.157-159
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• 2005

In this study, in order to develop Pb-free piezoelectric ceramics, $[Li_{0.04}(Na_{0.44}K_{0.52)-(Nb_{0.86}Ta_{0.10}Sb_{0.04})]O_3$ ceramics were fabricated by conventional mixed oxide method and their piezoelectric characteristics were investigated according to the poling condition. The transition temperature from orthorhombic phase to tetragonal phase observed at $93[^{\circ}C]$ and Curie temperature was $346[^{\circ}C]$. At $50[^{\circ}C]$ poling temperature, dielectric constant, electromecha nical coupling factor kp, piezoelectric $d_{33}$ const ant, coercive field Ec, remanant polarization Pr and mechanical quality factor Qm showed the optimum value of 737, 0.45, 209[pC/N], 1l.34[kV/cm], $7.14[{\mu}C/cm^2]$ and 205, respectively.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1337-1338
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• 2007

In this study, in order to develop low temperature sintering ceramics for multilayer piezoelectric actuator, 0.07Pb$(Mn_{1/3}Nb_{2/3})O_{3}-xPb(Ni_{1/3}Nb_{2/3})O_{3}-(0.93-x)Pb(Zr,Ti)O_{3}$ ceramics system were fabricated using $Li_{2}CO_{3}-Bi_{2}O_{3}$-CuO sintering aids and the specimens were sintered at $930^{\circ}C$. Thereafter their piezoelectric and dielectric characteristics were investigated with the amount of PNN substitution. At 9[mol%] PNN substitution, electromechanical coupling factor (kp), mechanical quality factor (Qm) and piezoelectric constant ($d_{33}$) showed the optimum value of 0.60, 1323 and 387pC/N, respectively.