• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.3
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• pp.159-163
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• 2016

In this paper, in order to develop optimum composition ceramics with excellent piezoelectric properties, $(Na_{0.525}K_{0.443}Li_{0.037})(Nb_{0.823}Sb_{0.08}Ta_{0.037})O_3+0.3wt%Bi_2O_3+0.4wt%Fe_2O_3$ lead-free piezoelectric ceramics were synthesized by conventional soild-state method. The calcination temperature of columbite precursors were fabricated at temperature range from $950^{\circ}C$ to $1,150^{\circ}C$ and sintering aids with low melting point were added to densify these ceramics. Effect of calcination temperature on dielectric and piezoelectric properties of ceramics were investigated. the ceramics with B-site columbite precursors at temperature of $1,100^{\circ}C$ obtained the optimal values of $d_{33}=272$ [pC/N], $k_p=0.51$, $Q_m=102$, ${\varepsilon}_r=978$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.5
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• pp.292-296
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• 2014

We investigated the effect of Ta doping on the dielectric and piezoelectric properties of lead-free $(K_{0.5}Na_{0.5})NbO_3$ ceramics prepared using a conventional ceramic processing. X-ray diffraction analysis revealed that Ta was perfectly substituted into Nb-sites in the range of 0 to 20 at%. As Ta content in the KNN increased, the sinterability of KNN ceramics was significantly degraded while the Ta doping enhanced the piezoelectric constant $d_{33}$, planar mode piezoelectric coupling coefficient ($k_p$), and electromechanical quality factor ($Q_m$). The highest values for $d_{33}$, $k_p$, and $Q_m$ was found to be 156 pC/N, 0.37, and 155, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.4
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• pp.205-209
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• 2016

In this paper, piezoelectric ceramics with the composition of $(Na_{0.525}K_{0.4425}Li_{0.0375})(Nb_{0.8975}Sb_{0.065}Ta_{0.0375})O_3+0.3wt%\;CoO+x\;CuO$ ($0.005{\leq}x{\leq}0.025$) (abbreviated to NKL-NST) were fabricated for ultrasonic sensor application. The effects of CuO addition and sintering on the microstructure and the piezoelectric properties of the NKL-NST ceramics were systematically studied. Excellent piezoelectric properties such as electromchanical coupling $factor(k_p)=0.415$, piezoelectric constant $(d_{33})=166pC/N$ and piezoelectric figure of merit $d_{{33}*}g_{33}=5.47pm^2/N$ were obtained from the 2.5 mol% CuO doped NKL-NST+0.3 wt%CoO ceramics sintered at $1,000^{\circ}C$ for 3 h.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.271-271
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• 2006

The structural, dielectric and piezoelectric properties of $[Bi_{1-x}(Na_{0.7-x}K_{0.2}Li_{0.1})]_{0.5}BaxTiO_3$ (BNKLBxT) ceramics were studied for the compositional range, x = 0-0.08. The samples were prepared by conventional sintering technique. The result of X-ray diffraction (XRD) suggest that $Ba^{2+}$ diffuse into the $[Bi(Na_{0.7}K_{0.2}Li_{0.1})]_{0.5}TiO_3$ (BNKLT) lattices to form a solid solution with a single phase perovskite structure. The ceramic show excellent piezoelectric and ferroelectric properties, and optimum properties measured are as follows: piezoelectric constant $d_{33}=230pC/N$, planar electromechanical coupling factor $k_p\;=\;40.3%$, remanent polarization $P_r\;=\;30\;{\mu}C/cm^2$, and coercive field $E_c\; =\;2.5\;kV/mm$, respectively.

• Proceedings of the Korean Ceranic Society Conference
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• 2002.10a
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• pp.15.1-15
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• 2002

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.4
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• pp.801-804
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• 2011

Electrical properties and microstructure were investigated on the effects of $MnO_2$ and the lead-free $(Na_{0.44}K_{0.52}Li_{0.04})(Nb_{0.83}Sb_{0.07}Ta_{0.1})O_3$ ceramics with the addition of $MnO_2$ were fabricated by a conventional mixed oxide method. A gradual change in the crystal and microstructure was observed with the increase of $MnO_2$ addition. For the NKN-LST-xmol%$MnO_2$ sintered at $1100^{\circ}C$, bulk density increased with the addition of $MnO_2$ and showed maximum value at addition 1.0mol% of $MnO_2$. Curie temperature of the NKN-LST ceramics slightly decreased with adding $MnO_2$. The dielectric constant, piezoelectric constant ($d_{33}$) and electromechanical coupling factor ($k_p$) increased below 0.25mol% of $MnO_2$ addition, which might be due to the increase in density. The high piezoelectric properties = 145 pC/N, electromechanical coupling factor = 0.421 and dielectric constant = 2883 were obtained for the NKN-LST-0.25mol%$MnO_2$ sintered at $1100^{\circ}C$ for 4h.

• Korean Journal of Materials Research
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• v.25 no.10
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• pp.566-570
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• 2015

$Bi_{0.5}Na_{0.5}TiO_3$ (BNT) based ceramics are considered potential lead-free alternatives for $Pb(Zr,Ti)O_3$(PZT) based ceramics in various applications such as sensors, actuators and transducers. However, BNT-based ceramics have lower electromechanical performance as compared with PZT based ceramics. Therefore, in this work, lead-free bulk $0.99[(Bi_{0.5}Na_{0.5})_{0.935}Ba_{0.065}]_{(1-x)}La_xTiO_3-0.01SrZO_3$ (BNBTLax-SZ, with x = 0, 0.01, 0.02) ceramics were synthesized by a conventional solid state reaction The crystal structure, dielectric response, degree of diffuseness and electric-field-induced strain properties were investigated as a function of different La concentrations. All samples were crystallized into a single phase perovskite structure. The temperature dependent dielectric response of La-modified BNBT-SZ ceramics showed lower dielectric response and improved field-induced strain response. The field induced strain increased from 0.17%_for pure BNBT-SZ to 0.38 % for 1 mol.% La-modified BNBT-SZ ceramics at an applied electric field of 6 kV/mm. These results show that La-modified BNBT-SZ ceramic system is expected to be a new candidate material for lead-free electronic devices.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.6
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• pp.372-376
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• 2014

We investigated the effect of excess CuO on the sintering behavior, ferroelectric, and piezoelectric properties of lead-free $Bi_{0.5}(Na_{0.82}K_{0.18})_{0.5}TiO_3$ (BNKT) ceramics. The addition of excess CuO was found to greatly contribute to the densification and grain growth, however, excess CuO over 3 mol% was precipitated at grain boundaries after sintering. BNKT with 1~2 mol% CuO in excess sintered at $975^{\circ}C$ showed piezoelectric properties comparable to those of unmodified BNKT sintered at $1,175^{\circ}C$. These results seem meaningful for its application to low cost multilayer actuators (MLAs) because low firing ceramics make it possible to apply less expensive base metals to the inner electrode of MLAs.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.172-173
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• 2008

In this study, $0.95(K_{0.5}Na_{0.5})NbO_3$-0.05Li$(Sb_{0.8}Nb_{0.2})O_3$ + $Ag_2O$ + x wt% $MnO_2$ were investigated as a function of the amount of $MnO_2$ addition in order to improve dielectric and piezoelectric properties of Lead-free piezoelectric ceramics. With increasing the amount of $MnO_2$ addition, density and electromechanical coupling factor $(k_p)$ increased up to 0.3wt.% $MnO_2$ and decreased above 0.3wt.% $MnO_2$. At the sintering temperature of 1020 $^{\circ}C$, Electromechanical coupling factor $(k_p)$, density, dielectric constant $({\varepsilon}r)$ and mechanical quality factor $(Q_m)$ of composition ceramics with 0.4wt% $Ag_2O$ addition showed the optimal value of 0.431, 4.33 g/$cm^3$, 820 and 119, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.5
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• pp.355-359
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• 2013

In this paper, the $0.995(Li_{0.04}(Na_{0.56}K_{0.44})_{0.96}(Nb_{0.90}Ta_{0.10})_{0.998}Zn_{0.005}O_3+0.005KNbO_3+xwt%\;TeO_2$ lead-free piezoelectric ceramics for energy harvesting devices were fabricated by the conventional mixed oxide method. The microstructure, dielectric, and piezoelectric properties were investigated as a function of the $TeO_2$ addition. All the specimens showed an orthorhombic phase structure. At the composition ceramics doped with 0.1 wt%$TeO_2$, the optimum values of $d_{33}$= 212 pC/N, $d_{33}{\cdot}g_{33}=9.54pm^2/N$, and kp=0.448 were obtained, respectively. The results indicate that the composition ceramics is a promising candidate for energy harvesting devices applications.