• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.109-114
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• 2002

Aging stabilities of the operating frequency of piezoelectric devices such as filter, oscillator and discriminator are very important. In this study it was studied aging stabilities of the length-extensional vibration mode of Pb(Zr$\_$y/Ti$\_$1-y/)O$_3$+x[wt%]Cr$_2$O$_3$ ceramics. PZT ceramics in Morphotropic phase boundary have higher aging rates of k$\_$31/ and resonant frequency than those in tetragonal phase or rhombohedral phase. Thermal aging moves the composition with maximum aging rate to Zr-rich side in Cr not added PZT system. Aging rate of resonant frequency of the ceramics with x=0.1, y=0.53 and x=0.3, y=0.53 increased by thermal aging.

• Journal of Sensor Science and Technology
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• v.13 no.2
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• pp.152-156
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• 2004

The dielectric and piezoelectric properties of 0.36Pb($Sc_{1/2}Nb_{1/2}$)$O_{3}$-0.25Pb($Ni_{1/3}Nb_{2/3}$)$O_{3}$-0.39Pb$TiO_{3}$ (hereafter PSNNT) at the morphotropic phase boundary (MPB) composition were investigated with $0{\sim}2.5$ mot% $MnO_{2}$ doping. Bulk density, dielectric loss and tetragonality of crystal structure were all improved with increasing $MnO_{2}$ additive content. With increasing $MnO_{2}$ additive content, the electromechanical coupling factor and quality factor were also increased: Electromechanical coupling $k_{p}$ and quality factor $Q_{m}$ at 2.0 mol% $MnO_{2}$ doping with were showed highest values of 55.6 % and 252, respectively.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1508-1511
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• 1996

In the fields of the optics, precise machine, semiconducting processing, the micro-positioning actuators are required for the control of position in submicron range. In this study, dielectric properties of 0.5PNN-(0.5-x)PZN-xPZT system ceramics with different PZT mole ratio were investigated. As the amount of PZT incerases, curie temperature was increased. The maximum of dielectric and piezoelectric constant was shown at 0.3 mole ratio of PZT amount. As a results, we have found that the structrue of ceramics with PZT 0.3 mole was morphotropic phase boundary.

• Electrical & Electronic Materials
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• v.7 no.1
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• pp.73-79
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• 1994

페로브스카이트형 강유전체의 활발한 연구는 제2차 세계대전중 미국과 구 소련등에서 TiO$_{2}$ 고체 콘덴서를 개량하던 중에 Ba 이 첨가된 BaTiO$_{3}$를 발견하면서부터 시작되었고, 일본에서는 PbZr$_{0.5}$Ti$_{0.5}$O$_{3}$의 morphotropic phase boundary를 발견하면서부터 이루어졌으며, 그것이 지니는 특성때문에 고체콘덴서, 초전형 적외선 센서, 초음파 발생과 검출기, 압전 점화기 및 표면파필터기 등 여러방면에 실용화 되고 있다. 따라서, 본 보고에서는 지금까지 연구된 페로브스카이트형 강유전체 세라믹 재료의 물성을 소개하고 앞으로의 연구동향 등에 관하여 서술하고자 한다.

• Journal of the Korean Ceramic Society
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• v.26 no.6
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• pp.802-810
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• 1989

The temperature dependence of piezoelectric strain constant and the electric field induced strain are investigated as a function of PT in 0.5[xPT-(1-x)PZ]-0.5PNN ceramics. The piezoelectric strain constant d31 has the highest value(360$\times$10-12m/V) at PT=0.68. The temperature dependence of d31 is improved as Curie temperature of sample is increased, and the electric field dependence of induced strain is decreased with the coercive field increased. This ceramic system shows both piezoelectric effect and electrostrictive effect under the applied electric field. The piezoelectric of tetragonal phase is higher than that of rhombohedral phase, and the magnitude of electrostrictive constant is appeared in the order of morphotropic, rhombohedral and tetragonal phase. The piezoelectric strain constant with applied field must be considered theelectrostrictive effect due to 90$^{\circ}$domain wall displacements, and the displacement of bimorph type actuator agrees with the calulated value well.

• Electrical & Electronic Materials
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• v.9 no.4
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• pp.351-356
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• 1996

The quartemary system ceramics 0.5[xPb(Zn$_{1}$3/Nb$_{2}$3/)O$_{3}$-(1-x)Pb(Ni$_{1}$3/Nb$_{2}$3/)O$_{3}$]-0.5[yPbTiO$_{3}$-(1-y) PbZrO$_{3}$ for piezoelectric actuators were prepared bv the were added to the raw materials up to 5 mole. Sintering temperature was varied form 1000.deg. C to 1200.deg. C. Sintering characteristrics, dielectric and piezoelectric properties were then investigated. Piezoelectric properties of sample prepared by the molten salt method were improved compared to those prepared by the conventional method. Addition of PZN shifted morphotropic phase boundary to more Zr-rich composition and decreased the piezoelectric properties.

• Journal of the Korean Ceramic Society
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• v.33 no.1
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• pp.49-55
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• 1996

The aim of this study is to investigate the change of bending strength and fatigue strength in the unpoled and poled Pb(Zr, Ti)O3 ferroelectrics of tetragonal morphotropic phase boundary (MPM) and rhombohedral com-position in terms of internal stress which is measured by XRD method. Before poling treatment the highest bending strength was found in rhombohedral composition. After poling treatment the bending strength decreas-ed in all compositions but it decreased most remarkably in tetragonal composition. The most prominent de-crease of bending strength after poling treatment in tetragonal was attributed to the occurrence of microcracks due to highanisotropic internal stress around grain boundary which was induced of bending strength after poling in MPB and rhombohedral composition was not due to the occurrence of microcracks but to the increase in tensile internal stress perpendicular to the direction of crack propagation by domain alignment. Fatigue strength was higher before poling treatment than after poling treatment for various compositions.

• The Korean Journal of Ceramics
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• v.1 no.4
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• pp.197-203
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• 1995

Nearly fully dense PZT samples both with tetragonal and with morphotropic phase boundary compositions were prepared by the conventional powder processing and sintering. A micro-indentation technique was used to evaluate the dependence of fracture toughness on remanent polarization, crack length and the direction of crack propagation. The result shows that the toughness increases with the remanent polarization along the poling direction and decreases in the transverse direction. The dependence of toughness on the remanent polarization is neither symmetric nor linear but rather shown to be saturated quickly with the increase in remanent polariztion. R-curve behaviors are observed in both poled and unpoled samples. Sequential SEM and XRD studies on annealed, poled, ground, fractured and etched samples show that domain switching is evident as a viable toughening mechanism but might depend upon the rate of crack propagation. Grain bridging is also observed as one of the active toughening mechanisms.

• Journal of the Korean Ceramic Society
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• v.37 no.1
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• pp.12-20
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• 2000

Dielectric property of Ba-modified 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 ceramics having compositions near the morphotropic phase boundary was investigated. For the specimens having Ba contents between 0 and 20 at%, the average transition temperature was decreased linearly with increasing Ba contents and the degree of hysteresis was also decreased with increasing Ba contents. The maximum dielectric constants (K), electric field induced polarization(P) and electrically-induced strain(S) were found to exihibit a maximum value at∼3 at% of Ba. The increase of S and the decrease of hysteresis by minor additions of Ba impurities indicated the development of new higher perfomance actuator materials. The composition of Ba-PMN-PT (10/65/35) may be appropriate for capacitor materials because of low hysteresis and high polarization.

• Journal of the Korean Ceramic Society
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• v.37 no.1
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• pp.63-69
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• 2000

Electrically-induced strain(S) and polarization(P) for Pb(Sc1/2Nb1/2)O3-PbTiO3(1-x)PSN-xPT) crystalline solutions were studied. From the compositional dependence of S and P we could observe two maximum values at x=0.10 and x=0.425. It is considered that PSNT10(x=0.10) composition is the structural phase boundary to indicate the variable order-disorder[VOD] region. PSNT(x=0.425) composition is the morphotropic phase boundary[MPB] to indicate the rhombohedral to tetragonal phase transition. Higher S (0.437%) and P (0.3974$\mu$C/$\textrm{cm}^2$) values were attained by the La substitution (5 wt%) at Pb site in the MPB composition of 57.5PSN-42.5PT.