• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.04b
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• pp.145-149
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• 2004

In this study, leed-free piezoelectric ceramics were investigated for pressure sensor applications as a function of the amount of $La_2O_3$ addition at BNKT system. With increasing amount of $La_2O_3$ addition, density and dielectric constant were increased up to 0.9wt% addition and decreased after 0.9wt% addition, electromechanical coupling factor$(k_p)$ and mechanical quality factor$(Q_m)$ showed the maximum values at 0.2wt% addition and decreased after 0.2wt% addition. The $k_p$, density, dielectric constant and $Q_m$ were showed the optimum values of 0.40, $5.71g/cm^3$, 768 and 118 at $La_2O_3$ 0.2wt% addition, 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 Korea Institute of Information and Communication Engineering
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• v.15 no.10
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• pp.2065-2071
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• 2011

The external quality factor ($Q_e$) is controlled by coupling condition between resonator and input/output ports in design of microwave filter. In this paper, we represent extracting method of external quality factor using phase response for resonator with input/output ports according to position of feed line from microstrip line resonator. The results regarding to position, coupling gap and line width for tapped line and coupled line structure are represented, and we got the exact $Q_e$ value from the this method. This results will be applied to coupled resonator filter design.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.8
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• pp.675-680
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• 2000

In this study the temperature coefficient of resonant frequency(TC $F_{r}$) dielectric and piezoelectric properties of Pb[(S $b_{1}$2//N $b_{1}$2/)$_{0.065}$)-(Z $r_{x}$, $Ti_{1-x}$ )$_{0.90}$] $O_3$ceramics were investigated with Zr/Ti ratio. The compositions near the morphotropic phase boundary (MPB) appeared when Zr/Ti ratio was 49.5/50.5 The dielectric constant and electromechanical coupling factor( $k_{p}$) also showed the highest values of 1,257, 0.653 respectively when the Zr/Ti ratio was 49.5/50.5 Moreover the mechanical quality factor( $Q_{m}$) showed th lowest value of 713 when the Zr/Ti ratio. The temperature coefficient of resonant frequency(TC $F_{r}$) abruptly change at the morphotropic phase boundary(MPB) which existed between the rhombohedral phase with highly negative TC $F_{r}$ of -106ppm/$^{\circ}C$ and the tetragonal phase with highly positive TC $F_{r}$ of +64pp $m^{\circ}C$ as Zr/Ti ratio varied from 50/50 to 49.5/50.5.50.5..50.5.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.05c
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• pp.157-160
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• 2001

We have investigated the Dielectric and Piezoelectric properties of $xPb(R_{1/2}Ta_{1/2})O_3-(1-x)Pb(Zr_{0.52}Ti_{0.48})O_3$ (R=Al,Y) solid solutions in which R ions are substituted for Al and Y ions. The maximum value of electromechanical coupling factor kp of 55% and 51% were obtained at the composition of 5mol% PAT and 5mol% PYT. However mechanical quality factor$(Q_m)$ had a minimum value of 44 and 69 at the composition of 5mol% PAT and 5mol% PYT. Also, the maximum value of piezoelectctric constant of $d_{33}(329[pC/N])$ and $d_{33}(310[pC/N])$ were obtained at the composition of 5mol% PAT and 5mol% PYT.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.53-53
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• 2008

Piezoelectric transformers have been widely used such as DC-DC convertor, invertor, Ballast, etc. Because, the y have some merits compared with electro-magnetic transformers such as step-up ratio, high efficiency, small size and lg hit weight, etc. Piezoelectric transformer require high electromechanical coupling factor kp in order to induce a large out put power in proportional to applied electric field. And also, high mechanical quality factor Qm is required to prevent mechanical loss and heat generation. In general, PZT system ceramics should be sintered at high temperatures between 1200 and $1300^{\circ}C$ in order to obtain complete densification. Accordingly, environmental pollution due to its PbO evaporation. Hence, to reduce its sintering temperature, various kinds of material processing methods such as hot pressing, high energy mill, liquid phase sintering, and using ultra fine powder have been performed. Among these methods, liquid phase sintering is basically an effective method for aiding densification at low temperature. In this study, In order to comparis on low temperature sintering and solid state sintering piezoelectric transformers, rosen type transformers were fabricated u sing two PZT ceramics compositions and their electrical properties were investigated.

• 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 Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.255-258
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• 2000

In this study, the structural, dielectric and piezoelectric properties of Pb[(Sb$\sub$1/2/Nb$\sub$1/2/)$\sub$x/- (Ni$\sub$1/3/Nb$\sub$2/3/)$\sub$0.15-x/- (Zr,Ti)$\sub$0.85/]O$_3$(x = 0, 0.01, 0.02, 0.03, 0.04, 0.05) ceramics is investigated as a function of Pb(Sb$\sub$1/2/Nb$\sub$1/2/)O$_3$ (abbreviated PSN) substitution. With the increase of PSN substitution, the crystal structure is transO$_3$formed from the tetragonal phase to the rhombohedral phase and the grain size is decreased abruptly. The curie temperature is decreased with the PSN substitution. The dielectric constant is increased with the PSN substitution and maximum value of 2290 is obtained at 4mol% PSN. With the PSN substitution, the coercive field is increased and the remnant polarization is decreased. The Electromechanical coupling factor(k$\sub$p/) Is showed the highest value of 0.622 at lmol% PSN and the mechanical quality factor(Q$\sub$m/) is decreased abruptly with the PSN substitution.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.391-395
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• 2000

In this study, the temperature coefficient of resonant frequency(TC $F_{r}$), dielectric and piezoelectric properties of Pb[(S $b_{1}$2/N $b_{1}$2/)$_{0.0035}$-(M $n_{1}$3/N $b_{2}$3/)$_{0.0065}$-(Z $r_{x}$ $Ti_{1-x}$ )$_{0.90}$] $O_3$ceramics is investigated with Zr/Ti ratio. The dielectric constant and electromechanical coupling factor( $k_{p}$) showed the highest values of 1257, 0.562 respectively when the Zr/Ti ratio is 49.5/50.5. The mechanical quality factor( $Q_{m}$) is the lowest value of 713 when the Zr/Ti ratio is 49.5/50.5, and increased with the decrease of the Zr/Ti ratio. The temperature coefficient of resonant frequency(TC $F_{r}$) change abruptly at the morphotropic phase boundary(MPB), which is between the rhombohedral phase with highly negative TC $F_{r}$ of -106ppm/$^{\circ}C$ and the tetragonal phase with highly positive TC $F_{r}$ of +64pp $m^{\circ}C$ as Zr/Ti ratio changes from 50/50 to 49.5/50.5.50.5..5.50.5.5.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.59-61
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• 2005

In this paper, in order to develop the low temperature sintering ceramics for multilayer piezoelectric transformer, $Pb[(Mn_{1/3},Nb_{2/3})_{0.07}(Zn_{1/3}Nb_{2/3})_a(Zr_{0.48}Ti_{0.52})_{1-0.07-a}O_3]$ ceramics were manufactured with the variations of PZN from 2 to 14mol% and their dielectric and piezoelectric properties were investigated. Sintering temperature was varied from 910 to $1000^{\circ}C$. At 8mol% PZN substituted specimen sintered at $970^{\circ}C$, electromechanical coupling factor(kp), mechanical quality factor(Qm), dielectric constant and peizoelectric constant($d_{33}$) showed the optimal values of 0.536, 1803, 1551 and 328[pC/N), respectively, for multilayer piezoelectric transformer application.