• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.1
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• pp.25-30
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• 2007

In this paper, lead-free [$Li_{0.04}(Na_{y}K_{1-y})_{0.96}](Nb_{0.86}Ta_{0.1}Sb_{0.04})O_{3}$ (y=0.4 - 0.58) ceramics were manufactured using conventional miked oxide method for acoustic emission(AE) sensor application and their dielectric and piezoelectric properties were investigated with the variations of Na/K ratio. The samples in the composition Na/K=54/46 exhibited excellent electrical properties of $d_{33}=300$ PC/N and kp=0.49. Taking into consideration above piezoelectric properties, it can be concluded that the [$Li_{0.04}(Na_{y}K_{1-y})_{0.96}](Nb_{0.86}Ta_{0.1}Sb_{0.04})O_{3}$ system ceramics are the promising lead-free materials capable of substituting PZT system ceramics.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.302-302
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• 2010

The lead-free piezoelectric ceramics must have high piezoelectric properties and electrical properties for the applications of piezoelectric devices. Therefore, KNN ceramics were investigated as a function of the variation of Nb. The density was increased with the increase of Nb. The density was saturated above 0.8895 mol Nb. The maximum value of electromechanical coupling coefficient(kp) was obtained 0.428 at 0.8895mol Nb. This result can be attributed to the well sintered of specimens. Also, The maximum value of mechanical quality factor(Qm) showed 1554 at 0.8895mol Nb. Therefore, this composition can be used for application of piezoelectric device such as piezoelectric transformer and piezoelectric actuator.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.03a
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• pp.12-12
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• 2010

The piezoelecric properties of $(K_{0.5}Na_{0.5})(Nb_{0.96}Sb_{0.04})O_3$+$1.2mol%K_4CuNb_8O_{23}$+$xmol%La_2O_3$ lead-free piezoelecric ceramics were investigated as a function x. These ceramics were fabricated by conventional ceramics processing. Piezoelectric constant ($d_{33}$) and piezoelectric charge coefficient ($g_{33}$) of x=0.2 mol% composition exhibited good properties of 160.3pC/N and 37.4($10^{-3}Vm/N$), respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.7
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• pp.563-567
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• 2011

The most widely used piezoelectric ceramics are lead oxide based ferroelectrics (PZT). However, the toxicity of lead oxide and its high vapor pressure during processing have led to a demand for alternative lead-free piezoelectric materials. We synthesized Lead-free piezoelectric ceramics of $0.96(K_{0.5}Na_{0.5})NbO_3-0.04SrZrO_3+x$ mol% $ZrO_2$ [KNN-SZ+$xZrO_2$; x= 0~0.10] doped with 0.1 wt% $MnO_2$ by a conventional solid state method. We investigated the piezoelectric properties and microstructures of these disk samples sintered in reduced atmosphere in order to evaluate the possibility of the multilayered piezoelectric ceramics having the base metal such as Ni as a internal electrode. All of these KNN-SZ samples sintered in 3%$H_2-97%N_2$ atmosphere at $1,140^{\circ}C$ exhibit pure perovskite structure irrespective of the content of $ZrO_2$. Meanwhile, the sintering denisty and piezoelectric properties such as $K_p$, $Q_m$ and $d_{33}$ of KNN-SZ samples as a function of $ZrO_2$ content show the maxima ($k_p$=28.07%, $Q_m$= 101.34, $d_{33}$= 156 pC/N) at x= 0.04 and it is likely that there is some morphotropic phase boundary(MPB) in this KNN-SZ+$xZrO_2$ composition system. These results indicate that the ceramic composition is a promising candidate material for applications in lead free multilayer piezoelectric ceramics.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1436-1437
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• 2011

(1-x)(Na,K)$NbO_3$-xBa(Zr,Ti)$O_3$ lead free piezoelectric ceramics were synthesized to enhance the piezoelectric properties of (Na,K)$NbO_3$. The synthesis and sintering method were the conventional solid state reaction method and general sintering method in air atmosphere. We report the improved piezoelectric properties in the perovskite structure composed of the NKN and BZT ceramics. We investigated the effects of NKN, BZT on the structural and electrical properties of the NKN-BZT ceramics. The NKN-BZT ceramics show good performance with piezoelectric constant $d_{33}$=155pC/N. The results reveal that (1-x)(Na,K)$NbO_3$-xBa(Zr,Ti)$O_3$ ceramics are promising candidate materials for lead-free piezoelectric application.

• Korean Journal of Materials Research
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• v.25 no.6
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• pp.288-292
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• 2015

New lead-free piezoelectric ceramics $0.96[\{Bi_{0.5}(Na_{0.84}K_{0.16})_{0.5}\}_{1-x}La_x(Ti_{1-y}Nb_y)O_3]-0.04SrTiO_3$ (BNKT-ST-LN, where $x=y=0.00{\leq}(x=y){\leq}0.015)$ were synthesized using the conventional solid-state reaction method. Their crystal structure, microstructure, and electrical properties were investigated as a function of the La and Nb (LN) content. The X-ray diffraction patterns revealed the formation of a single-phase perovskite structure for all the LN-modified BNKT-ST ceramics in this study. The temperature dependence of the dielectric curves showed that the maximum dielectric constant temperature ($T_m$) shifted towards lower temperatures and the curves became more diffuse with an increasing LN content. At the optimum composition (LN 0.005), a maximum value of remnant polarization ($33C/cm^2$) with a relatively low coercive field (22 kV/cm) and high piezoelectric constant (215 pC/N) was observed. These results indicate that the LN co-modified BNKT-ST ceramic system is a promising candidate for lead-free piezoelectric materials.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.46 no.3
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• pp.15-22
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• 2023

BNKT Ceramics, one of the representative Pb free based piezoelectric ceramics, constitutes a perovskite(ABO3) structure. At this time, the perovskite structure (ABO3) is in the form where the corners of the octahedrons are connected, and in the unit cell, two ions, A and B, are cations, A ion is located at the body center, B ion is located at each corner, and an anion O is located at the center of each side. Since Bi, Na, and K sources constituting the A site are highly volatile at a sintering temperature of 1100℃ or higher, it is difficult to maintain uniformity of the composition. In order to solve this problem, there should be suppression of volatilization of the A site material or additional compensation of the volatilized. In this study, the basic composition of BNKT Ceramics was set to Bi_0.5(Na_0.78K_0.22)_0.5TiO₃ (= BNKT), and volatile site (Bi, Na, and K sources) were coated in the form of a shell to compensate additionally for the A site ions. In addition, the physical and electrical properties of BNKT and its coated with shell additives(= @BNK) were compared and analyzed, respectively. As a result of analyzing the crystal structure through XRD, both BNKT(Core) and @BNK(Shell) had perovskite phases, and the crystallinity was almost similar. Although the Curie temperature of the two sintered bodies was almost the same (TC = 290 ~ 300 ℃), it was confirmed that the d33 (piezoelectric coefficient) and Pr (residual polarization) values were different. The experimental results indicated that the additional compensation for a shell additive causes the coarsening, resulting in a decrease in sintering density and Pr(remanent polarization). However, coating shell additives to compensate for A site ion is an effective way to suppress volatilization. Based on these experimental results, it would be the biggest advantage to develop an eco-friendly material (Lead-free) that replaced lead (Pb), which is harmful to the human body. This lead-free piezoelectric material can be applied to a biomedical device or products(ex. earphones (hearing aids), heart rate monitors, ultrasonic vibrators, etc.) and skin beauty improvement products (mask packs for whitening and wrinkle improvement).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.160-161
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• 2009

In this study, in order to develop the lead free piezoelectric ceramics with excellent piezoelectric properties, (Na,K)$NbO_3$ ceramics according to the amount CuO addition were fabricated using a conventional mixed oxide process and their piezoelectric and dielectric characteristics were investigated. At the 0.8mol% CuO added composition, density, electromechanical coupling factor(kp), echanical quality factor(Qm), dielectric constant$(\varepsilon_r$) and piezoelectric constant($d_{33}$) showed the optimum value of $4.459g/cm^3$, 0.469, 540, 410, 69.57pC/N, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.10
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• pp.901-905
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• 2008

In this study, $0.95(K_{0.5}Na_{0.5})NbO_{3}-0.05Li(Sb_{0.8}Nb_{0.2})O_{3}+0.2\;wt%Ag_{2}O$ were investigated as a variations of sintering times in order to improve dielectric and piezoelectric properties of lead-free piezoelectric ceramics. $Ag_{2}O$ were used as sintering aids and the specimens were sintered during 3, 5, 7, 9 and 11 hours, respectively. At the specimen sintered during 7 hour, Electromechanical coupling factor ($k_p$), density, dielectric constant (${\epsilon}_{\gamma}$), piezoelectric constant ($d_{33}$) and curie temperature ($T_c$) of composition ceramics showed the optimal value of 0.450, 4.274 $[g/cm^3]$, 1007, 257 [pC/N] and $396^{\circ}C$, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.8
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• pp.665-670
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• 2009

Lead-free piezoelectric ($Na_{1/2}K_{1/2}$)$NbO_3$ ceramics doped with CuO and $MnO_2$ were fabricated using the conventional oxide-mixing technique. With increasing content of CuO and $MnO_2$, the dielectric constant(${\varepsilon}_{33}$) and mechanical quality factor($Q_m$) value increased, while electromechanical coupling factor($K_p$) and piezoelectric constant($d_{33}$) decreased. The piezoelectric and dielectric properties ($Na_{1/2}K_{1/2}$)$NbO_3$ ceramics doped with CuO 2.461 wt% and $MnO_2$ 0.538 wt% at sintered temperature $1050\;^{\circ}C$ were attained ${\varepsilon}_{33}$ = 403, $K_p$ = 15, $Q_m$ = 122 and $d_{33}$ = 36 pC/N. Based on response surface methodology results using design of experiment, it was concluded that ($Na_{1/2}K_{1/2}$)$NbO_3$ doped with CuO 0.477 wt% and $MnO_2$ 0.269 wt% has possibility composition of being used for piezoelectric transformer.