• Journal of the Korean Crystal Growth and Crystal Technology
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• v.5 no.2
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• pp.152-164
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• 1995

$xPb(Fe_{1/2}Nb_{1/2})O_3 - (1 - x)Pb(Mg_{1/3}Nb_{2/3})O_3$ powders were synthesized by the molten salt synthesis method using the NaC!- KCI flux with 1 : 1 molar ratio, and their powders and dielectric properties were investigated. The synthesized powders showed less agglomerated shape with the average particle size of less than $2 \mu\textrm{m}$. The composition $x0.3Pb(Fe_{1/2}Nb_{1/2})O_3-0.7Pb(Mg_{1/3}Nb_{2/3})O_3$ could be sintered at $1000{\times}C$ and its dielectric constnat was over 11, 000.

• Transactions on Electrical and Electronic Materials
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• v.12 no.2
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• pp.72-75
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• 2011

In this study, $(K_{0.5}Na_{0.5})(Nb_{0.97}Sb_{0.03})O_3+0.9$ mol% $K_{5.4}Cu_{1.3}Ta_{10}O_{29}+x$ mol% $K_4CuNb_8O_{23}$ (x = 0, 0.2, 0.6, 0.8) ceramics were prepared by a conventional mixed oxide method. Their microstructure and electric properties were investigated. The secondary phase was made by virtue of $K_4CuNb_8O_{23}$ (KCN) addition in the $(K_{0.5}Na_{0.5})(Nb_{0.97}Sb_{0.03})O_3$ system ceramics. However, the sinterability of the ceramics increased with increasing $K_4CuNb_8O_{23}$ content. At the 0.6 mol% $K_4CuNb_8O_{23}$ added composition ceramics sintered at $1,060^{\circ}C$, kp and $d_{33}$ showed the optimum values of 0.39 and 145 pC/N, respectively, suitable for piezoelectric actuator application.

• Journal of the Korean Ceramic Society
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• v.32 no.7
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• pp.839-845
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• 1995

The structural and dielectric properties of Pb(Mg1/3Nb2/3)O3 ceramics substituted by Nd3+, La3+, K+ and Na+ were studied over 0~50 at.% substituent content. The 1 : 1 ordering behavior of Mg2+ and Nb5+ ions in the B site sublattice was observed in Nd3+-and La3+-modified compounds. The degree of ordering was increased with Nd3+, La3+ content in the compounds. But K+-or Na+-modified compounds did not exhibit the ordering behavior. This was explained by charge and size effect of A and B site cations and oxygen vacancies. As the mole fractions of substituent increased, the maximum values of dielectric constants were rapidly decreased and the phase transitions were broadened. Phase transition temperature was correlated with the covalency of A-O and B-O bonding.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.11
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• pp.925-929
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• 2009

In this study, $0.95(K_{0.5}Na_{0.5})NbO_3-0.05Li(Sb_{0.8}Nb_{0.2})O_3$ ceramics were investigated as a function of the amount of $Ag_2O$ addition in order to improve dielectric and piezoelectric properties of lead-free piezoelectric ceramics. With increasing the amount of $Ag_2O$ addition, density and electromechanical coupling factor ($k_p$) increased up to 0.2 wt.% $Ag_2O$ and decreased above 0.2 wt.% $Ag_2O$. At the sintering temperature of $1020^{\circ}C$, electromechanical coupling factor ($k_p$), density, dielectric constant (${\varepsilon}r$) and curie temperature (Tc) of ceramics with 0.2 wt% $Ag_2O$ showed the optimal values of 0.42, $4.33\;g/cm^3$, 738 and $393^{\circ}C$, respectively.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.11
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• pp.2093-2096
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• 2011

In this study, lead-free $(Na_{0.5}K_{0.5})NbO_3-BiTiO_3$ ceramics were fabricated by a conventional mixed oxide method. Structural and electrical properties of lead-free $(Na_{0.5}K_{0.5})NbO_3$ ceramics with the variation of $BiTiO_3$ were investigated. The results of X-ray diffraction analysis showed a typical polycrystalline perovskite structure without presence of the second phase in all specimens. Sintered density increased with an increasing of BTO and the specimen added with 0.07 mol% of $BiTiO_3$ showed the maximum value of 97.8%. Average grain size decreased and densification increased with an increasing of $BiTiO_3$ contents. The electromechanical coupling factor of the 0.01 mol% $BiTiO_3$ doped NKN specimens was 0.32. Dielectric constant, dielectric loss and Curie temperature of the 0.07 mol% $BiTiO_3$ doped NKN specimens were 1185, 0.145% and $400^{\circ}C$, 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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.216-217
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• 2005

In this paper, in order to develop Pb-free piezoelectric ceramics, $(Li_{0.05}Na_{0.57}K_{0.38})NbO_3$ ceramic was fabricated with the variation of $Bi_2O_3$ addition. Piezoelectric properties of the ceramic were varied with the amount of $Bi_2O_3$ addition and showed the maximum kp value at.0.2 wt% $Bi_2O_3$ addition. Qm of $Bi_2O_3$ added ceramics showed lower values than the non-added ceramics, however, the kp was increased by the addition of $Bi_2O_3$ 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=4.52g/$cm^3$, kp=0.47, $\varepsilon_r$=400 were obtained.

• Journal of the Korean Ceramic Society
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• v.40 no.11
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• pp.1078-1084
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• 2003

In order to develop a new type of nonlinear optical materials or photocatlaysts, Na$_2$O-Nb$_2$ $O_{5}$-Te $O_2$ glasses were prepared using conventional melt quenching method, and the crystallization behaviors and optical properties of these glasses was investigated. The optical and physical properties for Na$_2$O-Nb$_2$ $O_{5}$-Te $O_2$ glasses are: refractive index, n=2.04$\pm$0.04; density, p (g/㎤)=4.87$\pm$0.58; optical energy band of the transmission cut-off wavelength, E$_{0}$ (eV)=3.14$\pm$0.04. The transparent glass ceramics consisting of the nanocrysatls were obtained when the Na$_2$O-Nb$_2$ $O_{5}$-Te $O_2$ glass was first heat-treated at 3$50^{\circ}C$ for 1 h and than at 40$0^{\circ}C$ for 1 h. A cubic crystalline phase consisting of the nano-crysatls transforms into a stable phase at temperature above 47$0^{\circ}C$ for 1 h.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.4
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• pp.285-289
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• 2011

In this study, lead-free $(K_{0.5}Na_{0.5+X})(Nb_{0.96}Sb_{0.04})O_3+0.2mol%La_2O_3+1.2mol%$ $K_4CuNb_8O_{23}$ (X= 0~0.025) ceramics were fabricated by normal sintering method at $1060^{\circ}C$ for 5 h. Microstructures, piezoelectric and dielectric properties of specimens were investigated with special emphasis in the influence of Na excess addition. The grain size of specimen was slightly decreased with increasing Na content. In the 2 [mol%] Na excess addition of NKNS ceramics, density, electromechanical coupling factor, piezoelectric constant and electromechancal quality factor of specimen were found to reach the optimum values of 4.25 [$g/cm^3$], 0.4357, 154.43 [pC/N] and 580, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.315-316
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• 2006

Dense $0.95(Na_{0.5}K_{0.5})NbO_3-0.05LiTaO_3$ (NKN-LT) ceramics were developed by conventional sintering process. Sintering temperature was lowered by adding $Na_2O$ as a sintering aid. The electrical properties of NKN-LT ceramics were investigated as a function of $Na_2O$ concentration. When the sample sintered at $1000^{\circ}C$ for 4h with the addition of 1 mol% $Na_2O$, electromechanical coupling factor ($k_p$) and piezoelectric coefficient ($d_{33}$) of NKN-LT ceramics were found to reach the highest values of 0.43 and 190 pC/N, respectively.