• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.206-210
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• 1997

In the fields of the optics, precise machine, semiconductors, the micro-positioning actuators are required for the control of position in the submicron range. PNN-P2N-PZT ceramics were fabricated with various mole ratio of the PZT[Pb(Zr$_{1}$2//Ti$_{1}$2)O$_3$]. PNN (Pb(Ni$_{1}$3/Nb$_{2}$3/)O$_3$]and PZN[Pb(Zn$_{1}$3//Nb/sbu 2/3/)O$_3$] powders prepared by double calcination and PZT powders prepared by molten- salt synthesis method. The relative permittivity of specimen with PZT 0.3 mole ratio was shown 5,320 and appeared the relaxor ferroelectric feature. The maximum Piezoelectric coefficient d$_{31}$ to be used for evaluation the displacement of piezoceramics in PNN-PZN-PZT ceramics was 324$\times$10$^{-12}$ (C/V) at the vicinity of morphotropic phase boundary and was larger than that of solid PZT ceramics(120$\times$10$^{-12}$ C/V).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.6
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• pp.342-347
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• 2016

We investigated the effect of $Bi_{1/2}(Na_{0.82}K_{0.18})_{1/2}TiO_3$ (BNKT) modification on the ferroelectric and electric-field-induced strain (EFIS) properties of lead-free $0.97Bi_{1/2}(Na_{0.82}K_{0.18})_{1/2}TiO_3-0.03LaFeO_3$ (BNKTLF) ceramics as a function of BNKT content (x= 0, 0.1, 0.2, 0.3, 0.5, and 1). BNKT-modified BNKTLF powders were synthesized using a conventional solid-state reaction method. As the BNKT content x increased from 0 to 1 the normalized electric-field-induced strain ($S_{max}/E_{max}$) was observed to increase at relatively low fields, i.e., below the poling field. Moreover, BNKTLF-30BNKT showed about 460 pm/V as low as at 3 kV/mm, which is a considerably high value among the lead-free systems reported so far. Consequently, it was confirmed that ceramic-ceramic composite, a mixture of an ergodic relaxor matrix and embedded ferroelectric seeds, is a salient way to make lead-free piezoelectrics practical with enhanced EFIS at low field as well as less hysterical.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.4
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• pp.139-144
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• 2016

Effects of the shape and size of the piezoelectric materials on the performance of tonpilz transducers were studied with a computer simulation using a finite element method (FEM). The diameter and height of the donut-shaped piezoelectric ceramics head mass were changed as variables. And the effect of the stack number was also investigated. Finally, if the piezoelectric ceramics were changed to a piezoelectric single crystal having high piezoelectric constants, how the performances especially, the output power and the TVR transmittance were affected was simulated by FEM. As a result, the output of transducer could be increased to 10 times of PZT-4 with replacement of relaxor single crystal of the same size.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.9
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• pp.766-771
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• 2009

Lead-free $0.94(Na_{0.5}K_{0.5})NbO_3$-0.06Ba$(Ti_{0.9}Sn_{0.1})O_3$ [0.94NKN-0.06BTS] ceramics doped with 1 mol% $MnO_2$ were synthesized by a conventional solid state method. The phase transitional behavior and piezoelectric properties of the ceramics sintered at various temperatures were investigated. The 0.94NKN-0.06BTS ceramics sintered at $1050^{\circ}C$, having morphotropic phase boundary of orthorhombic and tetragonal phases, exhibited a microstructure with abnormal grain growth. A diffused phase transition behavior for all the specimens was verified as high degree of diffuseness (${\gamma}$) values from 1.45 to 1.79. A high piezoelectric constant of $d_{33}=256$ pC/N and a satisfactory electromechanical coupling factor of $k_p=42%$ were obtained for the relatively dense 0.94NKN-0.06BTS ceramics sintered at $1050^{\circ}C$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.2
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• pp.157-160
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• 2019

P(VDF-TrFE-CFE) (Poly (vinylidene fluoride-trifluoroethylene-chlorofluoroethylene)), which exhibits a high electrostriction of about 7%, can transmit tactile output as vibration or displacement. In this study, we investigated the applicability of P(VDF-TrFE-CFE) to wearable piezoelectric actuators. The P(VDF-TrFE-CFE) layers were deposited through spin-coating, and interspaced with patterned Ag electrodes to fabricate a two-layer $3.5mm{\times}3.5mm$ device. This layered structure was designed and fabricated to increase the output and displacement of the actuator at low driving voltages. In addition, a laser vibrometer and piezoelectric force microscope were used to analyze the device's vibration characteristics over the range of ~200~4,200 Hz. The on-off characteristics were confirmed at a frequency of 40 Hz.

• Korean Journal of Crystallography
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• v.8 no.2
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• pp.75-80
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• 1997

A perovskite relaxor ferroelectrics PMN is used as an important material to investigate the diffusive phase transition phenomena. In this study PMN single crystals were grown and the microstructure were observed. For the growth of PMN single crystals, the spontaneous nucleation technique and the TSSG technique were used. 2-5mm single crystals were grown from PbO self flux and it was observed that only PMN crystals were grown when excess MgO was added over 100% as flux. Single crystals with well developed (001) faces were obtained from PbO-B2O3 flux. single crystals larger than 1 cm were grown from PbO-B2O3 flux by TXXG technique. For higher quality crystals, optimization of the variables such as the rotation speed of seed crystal, the orientation of seed crystal, and cooling rate is needed. With grown crystals, it was confirmed by TEM diffraction pattern of thin plate crystal that the 1:1 ordering of Mg2+ and Nb5+ with small volume exists.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.4
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• pp.457-463
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• 2024

(Bi_1/2Na_1/2)TiO₃(BNT) piezoelectric ceramics are one of the promising materials that can replace Pb(Zr, Ti)O₃(PZT) piezoelectric ceramics due to the high electromechanical strain properties. However, it is still difficult to use practical applications because the required electric field for inducing electromechanical strain is relatively higher than that of PZT ceramics. To overcome this problem, it has been intensively studied on doping impurity or modifying other ABO₃ for BNT-based piezoelectric ceramics. Therefore, this study investigated the effects of La₂O₃ doping on the phase transition behavior and electromechanical strain properties in BNT-SrTiO₃ (BNT-ST) lead-free piezoelectric ceramics. In the case of the temperature-dependent dielectric properties, it was confirmed that a phase transition from ferroelectrics to relaxors is induced with increasing La₂O₃ content. As a result, the electromechanical strain properties of BNT-ST ceramics were improved. The highest S_max/E_max value corresponding to 300 pm/V was obtained at 2 mol% La₂O₃-dopped BNT-ST ceramics. Accordingly, this study successfully demonstrated that La₂O₃ doping is effective on the inducing phase transition from ferroelectrics to relaxors and the improving electromechanical strain properties of BNT-ST lead-free piezoelectric ceramics.