• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.10
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• pp.892-896
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• 2003

In this study, microstructure and piezoelectric properties of PSN-PZT ceramics modified with BiFeO$_3$ were investigated as a function of PNW substitution. With the increase of PNW substitution, tetragonality, Curie temperature and mechanical quality factor were decreased but grain size and electromechanical coupling factor(kp) was gradually increased. At 4 mol[%] PNW substitution, maximum kp of 0.567 was obtained.

• 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.

• 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.

• 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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.326-329
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• 2002

In this study, to develop the low temperature sintering ceramics for multilayer piezoelectric transformer, $0.02Pb(Sb_{1/2}Nb_{1/2})O_{3}-0.13Pb(Ni_{1/3}Nb_{2/3}O_3-0.85Pb(Zr,Ti)O_{3}$ system ceramics were manufactured with the variations of sintering temperature between 1,090 and $1240^{\circ}C$ and its dielectric and piezoelectric characteristics were investigated. With increasing the sintering temperature, electromechanical coupling factor (kp) and mechanical quality factor(Qm) were decreased. At $1,180^{\circ}C$ sintered specimen showed maximum value of 0.535 electromechanical coupling factor (kp). On the other hand,. The specimen sintered at $1,180^{\circ}C$ showed the maximum value of ${\varepsilon}r$=1,571, Qm=1,181 respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.260-264
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• 1999

In this paper, the structural, dielectrial and piezoelectrical properties of 0.03Pb(Sb$\sub$1/2/Ti$\sub$0.495/)O$_3$+Xwt% MnO(x= 0, 0.3, 0.4, 0.5, 0.7) system ceramics were investigated as a function of the addition of MnO. As a result, the samples of 0.3wt% MnO content showed the highest mechanical quality factor(Qm) of 1487, and its dielectric constant and electro mechanical coupling factor(Kp) 1357, 54.3%, respectively. Therefore, the dielectrial and piezoelectrical properties of the composition ceramics were indicated as the materials suitable for piezoelectric transformer.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.9
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• pp.794-797
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• 2002

Piezoelectric properties of PZT-PSN ceramics were investigated as a function of WO$_3$ addition from 0 wt% to 6.0 wt%. The dielectric and piezoelectric characteristics of PZT-PSN ceramics have been investigated at different calcination (80$0^{\circ}C$~90$0^{\circ}C$) and sintering (110$0^{\circ}C$~130$0^{\circ}C$) temperatures. The grain size was increased with the addition of WO$_3$and the sintering temperatures. Anisotropic properties of electromechanical coupling coefficient and piezoelectric coefficient are proven to be dependent on processing temperatures and amount of addition. At the specimen with 0.6 wt% WO$_3$ addition, using calcination temperature of 80$0^{\circ}C$ and sintering temperature of 110$0^{\circ}C$ , mechanical quality factor(Q$_{m}$) and electromechanical coupling coefficient(k$_{p}$) showed the excellent results of 1560 and 0.48, respectively Experimental results indicated that the PZT-PSN system ceramics with WO$_3$impurity could be effectively used for the microtransformer and actuator applications, etc.etc.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.721-723
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• 1992

The electrical resistivity and piezoelectric properties have been studied for Lead Zirconate-Titanate(PZT) with $Nb_2O_5$ dopant, fabricated from conventional mixed-oxide powders and molten salt synthesis. The resistivity and electromechanical coupling factor(Kp) were increased with increasing Nb contents. The reason for increasing of the electrical resistivity below the Curie Temperature(Tc), It is believed that the p-type electrical conduction in PZT is caused by the lead vacancies. The electromechanical coupling factor(Kr) and piezoelectric constant $d_{33}$ were improved by Nb additives. This behavior can be explained as a compensation effect and $Nb^{5+}$ can serve as a donar and contribute electrons to the conduction process. As a result, the optimized $Nb_2O_5$ dopants on the PZT specimens were 0.75 wt%.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.3
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• pp.155-160
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• 2000

The piezoelectric properties and the doping effect for$0.95Pb(Zr_xTi_{1-x})O_3+0.05Pb(Mn1/3Nb2/3)O_3$ compositions were studied. Also, the heat generation and the change of electromechanical characteristics, the important problem in practical usage, were investigated under high electric field driving. As a experiment results under low electric field, the values of kp and $\varepsilon33T$ were maximized, but Qm was minimized(Kp=0.57, Qm=1550) in the composition of x=0.51. In order to increase the values of Qm $Nb_2O_5$ was used as a dopant. As the result of that, the grain size was suppressed and the uniformity of grain was improved. Also, the values of kp decreased, and the values of Qm increased with doping concentration of $Nb_2O_5$. As a experiment results under high electric field driving, when vibration velocity was lower than 0.6[m/s], the temperature increase was $20[^{\circ}C]$, and the change ratio of mechanical quality factor was less than 10[%]. So, its electromechanical characteristics was very stable. Conclusively, piezoelectric ceramic composition investigated at this paper is suitable for application to high power piezoelectric devices.

• 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.