• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.4
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• pp.356-360
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• 2002

The piezoelectric properties of $0.05Pb(Al_{0.5}Nb_{0.5})O_3-0.95Pb(Zr_{0.52}Ti_{0.48})O_3+0.7wt%Nb_2O_5+o.5wt%MnO_2$ ceramics with the additive of BaCO$_3$were investigated. As the addition of BaCO$_3$increased from 0 to 0.4 wt%, the dielectric constant ($\epsilon^T _{33}$), piezoelectric constant ($d_33$), electromechanical coupling factor ($k_p$), and mechanical quality factor ($Q_m$) increased, while the dielectric loss ($tan\delta$) decreased. The highest piezoelectric and dielectric properties were observed at $1200^{\circ}C$ of the sintered temperature with 0.4 wt% of $BaCO_3$, and the properties of $d_33$, $k_p$, and $Q_m$ were 339 pC/N, 60% and 1754, respectively.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.05a
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• pp.436-438
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• 2009

In this study, in order to develop the composition of ceramics capable of being sintered at low temperature with high piezoelectric properties, PZW-PMN-PZT system ceramics for piezoelectric energy harvesting application were manufactured according to the amount of PZW addition. And also, their microstructural, dielectric and piezoelectric properties were investigated. At the sintering temperature of $930^{\circ}C$, a 5 mol% PZW substituted specimen showed a maximum value of density = $7.905g/cm^3$, kp = 0.585, $d_{33}$ = 351pC/N and Qm =1,254, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.276-276
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• 2007

As a candidate for lead-free piezoelectric materials, dense $(Na_xK_{0.94-x}Li_{0.06})NbO_3$ ceramics were developed by conventional sintering process. Sintering temperature was lowered by adding 1 mol% $Li_2O$ as a sintering aid. The electrical properties of $(Na_xK_{0.94-x}Li_{0.06})NbO_3$ ceramics were investigated as a function of Na/K ratio. When the sample sintered at $950^{\circ}C$ for 4 h with the compositions of morphotropic phase boundary, 0.47 < x < 0.51, electro-mechanical coupling factor ($k_p$) and piezoelectric coefficient ($d_{33}$) were found to reach the highest values of 0.42 and 190 pC/N, respectively. These excellent piezoelectric and electro-mechanical properties indicate that this system is potentially good candidate for lead-free material 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.25 no.11
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• pp.867-872
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• 2012

In this study, in order to develop excellent lead free piezoelectric ceramics for piezoelectric actuators application, $Li_{0.04}(Na_{0.50}K_{0.50})_{0.96}[(Nb_{0.86}Ta_{0.10}Sb_{0.04})_{0.994}Co_{0.015}]O_3+0.0025SrO+0.15\;wt%K_2CO_3+x\;wt%Nb_2O_5$ (x = 0 - 0.5 wt%) (abbreviated as LNKNTSCS-xN) ceramics were fabricated by a conventional sintering technique. the phase structure, microstructure and electrical properties were investigated with a emphasis on the influence of the $Nb_2O_5$ content. High electrical properties of $d_{33}$=234 pC/N, kp=0.392, ${\varepsilon}_r$=1,395, ${\rho}=4.70g/cm^3$ were obtained from the specimen with x=0.4 wt%, which suggests that the composition ceramics is a promising lead-free piezoelectric material.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.10
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• pp.630-634
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• 2014

$(Na_{0.525}K_{0.4425}Li_{0.0375})(Nb_{0.9975}Sb_{0.065}Ta_{0.0375})O_3+0.3 wt%CoO$ ceramics were fabricated as a function of CuO addition by traditional solid state sintering process in order to develop excellent lead-free piezoelectric ceramics composition. The addition of CuO in the LNKNTS composition ceramics can effectively enhance the densification of the ceramics, resulting in the oxygen vacancies as hardening effect. The excellent piezoelectric properties of electromechanical coupling factor($k{\small}_P$) of 0.378, piezoelectric constant($d_{33}$) of 152 pC/N were obtained from the 1.0 mol% CuO doped LNKNTS ceramics sintered at $1,020^{\circ}C$ for 3 h.

• Journal of the Korean Ceramic Society
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• v.32 no.3
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• pp.378-384
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• 1995

Effects of $La_2O_3$, $MnO_2$ on the dielectric and piezoelectric properties of $0.02Pb(Y_{2/3}W_{1/3}O_3-0.98Pb(Zr_{0.52}Ti_{0.48})O_3$ system were investigated. The addition of La2O3 to the system enhanced electromechanical coupling factor (kp), piezoelectric constant (d33), but hardly changed mechanical quality factor (Qm). On the other hand, the addition of $MnO_2$ increased Qm significantly, but did not degrade kp and d33 so much. The piezoelectric properties of $0.02Pb(Y_{2/3}W_{1/3}O_3-0.98Pb(Zr_{0.52}Ti_{0.48})O_3$ containing 0.1wt% $La_2O_3$, 0.4wt% $MnO_2$ were very good and kp, d33, Qm were 55%, 350$\times$10-12C/N, 780, respectively. The size of the grains was proportional to the change of c/a (tetragonality) ratio caused by the addition of $La_2O_3$ and $MnO_2$, and dielectric, piezoelectric properties were sensitive to the amountof pyrochrole phase.

• 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.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.3
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• pp.227-231
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• 2008

In this study, in order to improve the electrical properties of low temperature sintering piezoelectric ceramics, $[0.05Pb(Zn_{1/2}W_{1/2})-0.07Pb(Mn_{1/3}Nb_{2/3})-0.088Pb(Zr_{0.48}Ti_{0.52})]O_3$(abbreviated as PZW-PMN-PZT) ceramic systems were fabricated using $Bi_2O_3$, CuO and $Li_2CO_3$ as sintering aids and then their piezoelectric and dielectric properties were investigated according to the amount of $Li_2CO_3$ and post-annealing process. Post-annealing process enhanced all physical properties except for mechanical quality factor (Qm). 0.2 wt% $Li_2CO_3$ added and post-annealed specimen showed the excellent values suitable for low loss piezoelectric actuator application as follow: the density = 7.86 $g/cm^3$ electromechanical coupling factor (kp) = 0.575, piezoelectric constant $d_{33}$ = 370 pC/N, dielectric constant ($\varepsilon_r$) = 1546, and mechanical quality factor (Qm) = 1161, respectively.

• Journal of the Korean Ceramic Society
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• v.45 no.6
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• pp.363-367
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• 2008

Lead-free $(K_{0.44}Na_{0.52})(Nb_{0.86}Ta_{0.10})-0.04LiSbO_3$ piezoelectric ceramics have been synthesized by conventional sintering process and then investigated on the sintering and piezoelectric properties by high energy ball milling (HEBM) treatment. The powders milled for different time are characterized by XRD, FE-SEM. The powders are pressed into a pellet and sintered. It is found that the piezoelectric properties of sintered specimens are strongly dependent on the milling time. The piezoelectric properties are enhanced by high energy ball milling treatment. The planer electromechanical coupling factor ($k_p$) and piezoelectric constant ($d_{33}$) of a specimen sintered at $1050^{\circ}C$ are 0.44 and 267 pC/N, respectively.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.4
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• pp.160-165
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• 2015

Lead-free piezoelectric materials have been actively studied to substitute for conventional PZT based solid solution, $Pb(Zr_xTi_{1-x}O_3)$, which occurs unavoidable PbO during the sintering process. Among them, Bismuth Sodium Titanate, $Na_{0.5}Bi_{0.5}TiO_3$ (abbreviated as NBT) based solid solution is attracted for the one of excellent candidates which shows the strong ferroelectricity, Curie temperature (Tc), remnant polarization (Pr) and coercive field (Ec). Especially, the solid solution of rhombohedral phase NBT with tetragonal perovskite phase has a rhombohedral - tetragonal morphotropic phase boundary. Modified NBT with tetragonal perovskite at the region of MPB can be applied for high frequency ultrasonic application because of not only its low permittivity, high electrocoupling factor and high mechanical strength, but also effective piezoelectric activity by poling. In this study, solid state ceramic processing of NBT and modified NBT, $(Na_{0.5}Bi_{0.5})_{0.93}Ba_{0.7}TiO_3$ (abbreviated as NBT-7BT), at the region of MPB using 7 % $BaTiO_3$ as a tetragonal perovskite was introduced and the structure between NBT and NBT-7BT were analyzed using rietveld refinement. Also, the ferroelectric and piezoelectric properties of NBT-7BT such as permittivity, piezoelectric constant, polarization hysteresis and strain hysteresis loop were compared with those of pure NBT.