• 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.19 no.8
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• pp.707-711
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• 2006

ZnO was doped up to 0.3 wt% for improving the electrical properties of lead-free $[Li_{0.04}(Na_{0.44}Ko_{0.52})-(Nb_{0.86}\;Ta_{0.10}\;Sb_{0.04})]O_3$ piezoelectric ceramics. The ceramics were fabricated with the conventional sintering processes. Crystal structure of the samples was tetragonal phase regardless of ZnO amount. However, the piezoelectric properties were varied with the ZnO amount. The electro-mechanical coupling factor $(k_p)$ was with the ZnO amount up to 0.2 wt% but decreased with the further addition. the maximum value of $k_p$ was 0.475. Density, piezoelectric charge constant and relative dielectric constant was also showed maximum value at 0.2 wt%. The maximum values are $4.75g/cm^3$, 275 pC/N, 1403, respectively. In contrast, the mechanical quality factor $(Q_m)$ was not varied with increasing the ZnO addition up to 0.2 wt% but rapidly increased at 0.3 wt%.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.2
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• pp.104-108
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• 2013

In this paper, the $0.95(Na_{0.5}K_{0.5})_{0.04}[(Nb_{0.8}Ta_{0.20})_{0.994}Co_{0.015}]O_3$(abbreviated as NKNT) + $0.05KNbO_3$ lead-free piezoelectric ceramics were synthesized by the conventional mixed oxide method route with normal sintering. And also, the effects of calcination temperature on the microstructure, dielectric properties, and piezoelectric properties were investigated. A polymorphic phase transition(PPT) between orthorhombic and tetragonal phases was observed in specimens calcined at $810^{\circ}C{\sim}850^{\circ}C$. The ceramics calcined at $830^{\circ}C$ showed excellent piezoelectric properties: $d_{33}$= 179 pC/N, $k_p$= 0.384, $Q_m$= 79.73). These results indicate that the ceramic is a promising candidate material for lead-free piezoelectric ceramics.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.204-205
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• 2005

[ $(Na_{0.5},\;K_{0.5})NbO_3$ ] ceramics were studied as lead free Piezoelectric materials. The addition of CdO were enhanced the sinterability of the NKN ceramics. The $(Na_{0.5},\;K_{0.47}Cd_{0.02})NbO_3$ ceramics show that electromachanical coupling factor($k_p$) is 0.34and mechanical quality factor($O_m$) is 120.

• Journal of the Korean Ceramic Society
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• v.50 no.2
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• pp.157-162
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• 2013

The need for lead-free piezoceramics has caused a renewal of interest in $BaTiO_3$-based systems. Recently, it was found that ceramics in the $(Ba,Ca)(Zr,Ti)O_3$ system have properties comparable to those of $Pb(Zr,Ti)O_3$. However, these ceramics require rather high sintering temperatures of $1450-1550^{\circ}C$. In this work, the effect of $TiO_2$ and CuO addition on the sintering behavior, microstructure, dielectric and piezoelectric properties of $(Ba_{0.85}Ca_{0.15})(Zr_{0.1}Ti_{0.9})O_3$ (BCTZ) ceramics will be discussed. BCTZ ceramics were prepared by the mixed oxide route and 1 mol % of $TiO_2$ or CuO was added. Undoped and doped ceramics were sintered at $1350^{\circ}C$ for 1-5 h. CuO was found to be a very effective sintering aid, with samples sintered for 1 h at $1350^{\circ}C$ having a bulk density of 95% theoretical density; however the piezoelectric properties were greatly reduced, probably due to the small grain size.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1434-1435
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• 2011

In this study, NKN-LST ceramics were prepared by a conventional mixed oxide method and their structure and piezoelectric properties were investigated with the variations of sintering temperature. It was observed that the various sintering temperatures influenced the electrical properties and structural properties of the NKN-LST ceramics. It was found that the piezoelectric properties of NKN-LST ceramic sintered at $1080^{\circ}C$ for 4h has a piezoelectric constant and a planar electromechanical coupling coefficient of 161pC/N and 0.311% respectively. This ceramics look very promising as possible, practicable, lead-free replacements for lead zirconate titanate.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.6
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• pp.484-488
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• 2009

In this study, in order to develop the lead-free piezoelectric ceramics with high piezoelectric and dielectric properties, $[(K_{0.5}Na_{0.5})_{0.95}Li_{0.05}(Nb_{0.96}Sb_{0.04})]O_3$ ceramics were fabricated using $Ag_2O$ as sintering aid and a conventional mixed oxide process and their piezoelectric and dielectric characteristics were investigated according to the $SrTiO_3$ substitution. $SrTiO_3$ substitution enhanced density, dielectric constant(${\varepsilon}_r$) and electromechanical coupling factor($k_p$). However, mechanical quality factor was deteriorated. And also, Curie temperature ($T_c$), and phase transition temperature($T_p$) were rapidly decreased. At the 0.5 mol% $SrTiO_3$ substitution, density, electromechanical coupling factor($k_p$), dielectric constant(${\varepsilon}_r$) and piezoelectric constant($d_{33}$) of specimen showed the optimum value of $4.437\;g/cm^3$, 0.457, 1294, 265 pC/N, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.218-219
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• 2005

In this paper, in order to develop Pb-free piezoelectric ceramics, $[Li_{0.04}(Na_{0.44}K_{0.52})-(Nb_{0.86}Ta_{0.10}Sb_{0.04})]O_3$ ceramic was fabricated with the variation of ZnO addition. Piezoelectric properties of the ceramic were varied with the amount of ZnO addition and showed the maximum kp value at 0.2 wt% ZnO addition. Qm of ZnO added ceramics showed lower values than the non-added ceramics, however, the kp was increased by the addition of ZnO up to 0.2 wt%. At the sintering temperature of 1110$^{\circ}C$ and the calcination temperature of 850$^{\circ}C$, the optimal values of density=473g/$cm^3$, kp=0.473, $\varepsilon_r$=1403 were obtained.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.744-747
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• 2004

[ $0.96[Bio_{0.5}(Na_{0.84}K_{0.16})_{0.5}TiO_3]+0.04SrTiO_3+0.3wt%Nb_2O_5+0.2wt%La_2O_3+xwt%MnO_2$ ], were studied in order to develope the superior dielectric and piezoelectric properties of Lead-free Piezoelectric ceramics. With increasing amount of $MnO_2$ addition, density showed the maximum value of $5.79[gcm^3$] at 0.1wt% $MnO_2$ addition, and electromechanical coupling factor($k_p$) and dielectric constant decreased, and mechanical quality factor($Q_m$) increased and showed the maximum value of 161 at 0.3wt% $MnO_2$ addition.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.193-195
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• 2005

[ $0.96[Bi_{0.5}(Na_{0.84}K_{0.16})_{0.5}TiO_3]+0.04SrTiO_3+0.3wt%Nb_2O_5+0.2wt%La_2O_3+xwt%ZnO$ ], were studied in order to develope the superior piezoelectric properties of Lead-free piezoelectric ceramics. With increasing amount of ZnO addition, density showed the maximum value of 5.79(g/$cm^3$) at 0wt% ZnO addition, and electromechanical coupling factor($k_p$) and dielectric constant decreased, and mechanical quality factor($Q_m$) increased and showed the maximum value of 280 at 0.4wt% ZnO addition.