• 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.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.1
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• pp.33-38
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• 2003

Highly homogeneous PZT powder was prepared by a partial oxalate method using chemicals of (Z $r_{0.53}$ $Ti_{0.47}$) $O_2$, Pb(N $o_3$)$_2$and (COOH)$_2$ㆍ2$H_2O$. N $b_2$ $O_{5}$ addition effect on microstructure and electrical properties of PZT ceramics was investigated. When the precursors were calcined at 71$0^{\circ}C$, a single perovskite phase was obtained. After sintering at 110$0^{\circ}C$, X-ray diffraction Patterns showed coexistence of rhombohedral and tetragonal phases regardless of the N $b_2$ $O_{5}$ content. As the content of N $b_2$ $O_{5}$ increased, grain size decreased but sintered density increased. The electromechanical coupling factor of kp and the piezoelectric constant of $d_{31}$ increased linearly with the content of N $b_2$ $O_{5}$, and those values reached 0.7 and -200, respectively, when 1.2 mol% of N $b_2$ $O_{5}$ is added. is added.ded.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.03a
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• pp.2-4
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• 2010

Nowadays, application fields using piezoelectric ceramics are various. On this paper, Characteristics of thin-type ultrasonic motor generating elliptical displacements has been analyzed by FEM, and then the motor was fabricated. Structure of the motor consists of sixteen ceramic pieces attached elastic body upper and bottom. Principle of the motor is to apply alternative voltages which have 90 phase difference to attached ceramics, and then elliptical displacements is generated at four edges of clastic body. And then rotor is rotated by the elliptical displacements. In case of ceramic thickness 1.5[mm], characteristic of the highest speed was found at 79[kHz]. In case of ceramic thickness 2[mm], Characteristic of the highest speed was observed at 77.5 [kHz]. Consequently, speed and torque of USM were increased linearly with increasing in applied voltage.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.5
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• pp.502-507
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• 1992

To improve temperature stability, 0.05Pb(SnS11/2TSbS11/2T)OS13T-0.35PbTiOS13T-0.60PbZrOS13T+0.4[wt%]MnO S12T piezoelectic ceramics were manufactured with the addition of CrS12TOS13T by Hot Press method. And the SAW delay line was fabricated and effects of CrS12TOS13T to the propagation characteristics of SAW was investigated, and the SAW filter was fabricated on C4 specimen added by 0.2[wt%] CrS12TOS13T whose propagation characteriatics of surface acoustic wave were the bast and its frequency characteristics was investigated. Electromechancal coupling factor(kS1sTS02T) was 3.11[%] and its temperature coefficient of the center frequency(CS1foT)was -21.27[ppm/$^{\circ}C$] in C4. The 31[MHz]]SAW IF filter of C4 scarcely had diffraction phenomena and therefore it was proper.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.4
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• pp.274-280
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• 1998

Polycrystalline $Sr_2Nb_2O_7$ ceramics with very high Curie temperature were sintered using the powder derived by the chemical coprecipitation method (CCP). The phase evolution and grain-orientation of sintered samples were examined by XRD, while sintering behavior, dielectric properties and polarization were studied by SEM and ferroelectric tester. Extremely high degree of grain-orientation was observed along the (0k0) direction, which resulted in anisotropic dielectric properties of the sintered samples, with the dielectric constant values approaching those for single crystal. Thin film fabrication of $Sr_2Nb_2O_7$ in the pyroniobate family was also attempted on $SiO_2$/Si(100), Pt/$SiO_2$/Si(100), Pt/Ti/$SiO_2$/Si(100) and Pt/$ZrO_2/SiO_2/Si_2(100)$ substrates, using metalorganic decomposition (MOD) process. Neodecanoate precursor solution was prepared by mixing strontium neodecanoate with niobium neodecanoate synthesized from niobium ethoxide. It was found that $Sr_2Nb_2O_7$ single phase appeared in XRD patterns the samples annealed above $950^{\circ}C$. The effect of substrate type on film microstructure and dielectric properties was observed.

• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.193-195
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• 1994

In this study, the structural, dielectric and piezoelectrical properties of $xPb(Mg_{1/2}W_{1/2})O_3-(1-x)[0.41Pb(Ni_{1/3}Nb_{2/3})O_3-0.36PbTiO_3-0.23P Zr)_3]$ (x=0, 0.01, 0.02, 0.03, 0.04, 0.05) system ceramics were investigated. The dielectric constant ${\varepsilon_{33}}^{\tau}$ at loon temperature increased up to 3mol% PMW and decreased with further PMW content. The specimen with 1mol% $Pb(Mg_{1/2}W_{1/2})O_3$, which has the ${\varepsilon_{33}}^{\tau}=5509$, kp=59[%] and $d_{33}=758{\times}10^{-12}[C/N]$, exhibits good characteristics.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.321-322
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• 2007

In this thesis, the sintering properties and piezoelectric properties of $Pb[(Co_{0.5}W_{0.5})_{0.03}(Ni_{1/3}Nb_{2/3})_{0.07}(Zr_{0.52}Ti_{0.48})_{0.9}]O_3+0.5[wt%]MnO_2$ ceramics has been systematically investigated as a function of the sintering temperature after manufacturing the specimens with a general method. The lattice constant from the analysis of crystal structure showed that the pychlore structure was decreased with the increase of the sintering temperature. Density was decreased by increasing $B_2O_3$. TCFr was showed its minimum variation rate of 0.35~-0.52[%] in the sintered temperature 950[$^{\circ}C$], $B_2O_3$ 3[wt%]. The electromechanical coupling coefficient (Kp) showed its maximum of 31.116[%] in the sintered temperature 1050[$^{\circ}C$], and its minimum of 20.220[%] in the sintered temperature 1150[$^{\circ}C$].

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.798-801
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• 2004

In this study, in order to develop low temperature sintering ultrasonic vibrator, PCW-PMN-PZT ceramics with the amount of $Nb_2O_5$ addition were manufactured. All of the fabricated sample showed pure pervoskite structure of tetragonal phase. With increasing the amount of $Nb_2O_5$ addition, mechanical quality factor Qm were increased up to 0.2wt%$Nb_2O_5$ addition and then decreased. And also, with increasing the amount of $Nb_2O_5$ addition, grain size, kp, density and dielectric constant were linearly decreased. At the 0.2wt% $Nb_2O_5$ addition composition ceramic, kp of 0.48, Qm of 2186, ${\varepsilon}r$ of 1219 were shown, respectively. Their values were suitable for ultrasonic vibrator application.

• Journal of the Korean Ceramic Society
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• v.45 no.4
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• pp.220-225
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• 2008

Lead-free ferroelectric ceramics are widely researched today for industrial applications as sensors, actuators and transducers. Since $Pb(Zr_aTi_{1-a})O_3$-(PZT) has high Curie temperature($T_C$), high piezoelectric properties near its morphotropic phase boundary(MPB) composition and small temperature dependence electrical behavior, it has been used to commercial materials for wide temperature range and different application fields. According to the tolerance factor concept, since the $Bi^{3+}$ cation with 12-fold coordinate has a smaller ionic radius than 12-fold coordinate $Pb^{2+}$, most bismuth based perovskites possess a smaller tolerance factor. Therefore, MPBs with a higher $T_C$ may be expected in $Bi(Me^{3+})O_3PbTiO_3$ solid solutions. As in lead based perovskite systems, it is clear that we need to explore more materials in simple or complex bismuth based MPB systems. The objective of this study is to investigate the $Bi(Ni_{1_a}X_a)O_3-PbTiO_3(X=Ti^{4+},\;Nb^{5+})$ perovskite solid-solution. For improving the electronic conduction problem, the magnesium and manganese modified system was also studied.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.258-258
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• 2007

KNN계 세라믹스는 $400^{\circ}C$ 이상의 높은 큐리온도와 압전특성을 가져 Pb대체용 소재로 각광을 받고 있고 많은 연구들이 진행중이다. 하지만 potassium의 수분과의 반응성이 강하고 녹는점이 낮아 소결시 K2O의 휘발로 인해 화학양론적인 정확도를 맞추기가 어려운 단점을 가지고 있다. 이러한 단점을 보완하기 위하여 Hot pressing, Hot forging, SPS등 여러 가지 방법을 이용한 연구가 보고되었다. 본 연구에서는 낮은 소결밀도를 향상시키기 위하여 성형압과 성형방법을 달리하여 성형밀도에 따른 소결 밀도와 압전 특성 변화에 대하여 관찰하였다. 넓은 범위의 성형밀도를 얻기 위하여 낮은 성형압을 가할 수 있는 기계적으로 작동하는 press와 높은 성형밀도를 가할 수 있는 유압식 press를 사용하였고, 양산성을 고려하여 일반적인 세라믹 제조공정을 이용하였다.