• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.139-142
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• 2003

Microwave dielectric properties of $Ca(Li_{1/4}Nb_{3/4})O_3-CaTiO_3$ ceramic systems were investigated with calcination temperatures and amounts of $CaTiO_3$ in the range of 0.2 to 0.4mol. $Ca(Li_{1/4}Nb_{3/4})O_3$ ceramics having orthorhombic crystal structure could be synthesized at $750^{\circ}C$ and sintered well at $1250^{\circ}C$. They showed the dielectric constant of 26, quality factor($Q{\times}f_o$) of 13,000 and temperature coefficient of resonant frequency(${\tau}_f$) of $-49{\pm}2ppm/^{\circ}C$ With adding the $CaTiO_3$ amount the dielectric constant and ${\tau}_f$ increased due to the solute of $CaTiO_3$ but the quality factor decreased. The 0.7$Ca(Li_{1/4}Nb_{3/4})O_3-0.3CaTiO_3$ ceramic showed the dielectric constant of 44, quality factor($Q{\times}f_o$) of 12,000 and ${\tau}_f$ of $-9{\pm}1ppm/^{\circ}C$.

• 한국세라믹학회지
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• 제43권1호
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• pp.55-61
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• 2006

The microwave dielectric properties and low temperature sintering of $Ca[Ti_{1-x}(Ni_{1/3}Nb_{2/3})_x]O_3$ system were investigated at the sintering temperature $1,200\~1,350^{\circ}C$. The density and quality factors $(Q{\times}f)$ increased while dielectric constants slightly decreased with the decrease of Ti. The dielectric constant, quality factor, and temperature coefficient of resonance frequency $(\tau_f)$ were 64, 17,000 GHz, and $-9.1\;ppm/^{\circ}C$ respectively, when $CaTi_{1/2}(Ni_{1/3}Nb_{2/3})_{1/2}O_3$ ceramics were sintered at $1,300^{\circ}C$ for 4 h. $2Li_2O-B_2O_3$ was added to $CaTi_{1/2}(Ni_{1/3}Nb_{2/3})_{1/2}O_3$ to decrease the sintering temperature for LTCC application. The microwave dielectric properties of the samples sintered at $925^{\circ}C$ for 2 h with the addition of $6\;wt\%\;2Li_2O-B_2O_3$ were $\varepsilon_r=48.7,\;Q{\times}f=8,460\;GHz$, and $\tau_f=+5.6ppm/^{\circ}C$. Compatibility test of the composition with silver electrode shows no reaction with silver electrode, implying the feasibility as a high-K LTCC material.

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2003년도 춘계총회 및 연구발표회 초록집
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• pp.190.1-190
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• 2003

• 한국세라믹학회지
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• 제39권1호
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• pp.26-32
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• 2002

유전율(${\varepsilon}_r$) 126, $Q{\cdot}f_{0}(GHz)$값은 2240, 공진주파수의 온도계수(${\tau}_f$) $+68\;ppm/^{\circ}C$의 특성을 갖는 $0.3CaTiO_3-0.7(Li_{1/2}Nd_{1/2})TiO_3에\;Nd_2O_3$를 첨가하였을 때의 마이크로파 유전특성의 변화에 대해 고찰하였다. 유전율(${\varepsilon}_r$)은 5wt% $Nd_2O_3$ 첨가시 131로 가장높은 값을 나타내었으며, 이후 첨가량이 증가함에 따라 유전율은 감소함을 보였다. $Q{\cdot}f_{0}(GHz)$값은 9wt% $Nd_2O_3$ 첨가시까지 입계의 치밀화 등에 의해 3533까지 증가하다가 이후 l8wt% $Nd_2O_3$첨가시까지는 비정상적 입계성장의 영향으로 감소함을 보이고, 25 wt% 이상 첨가시에는 제2상인 $Nd_2Ti_2O_7$상의 영향으로 다시 증가함을 보였다. 공진주파수의 온도계수($({\tau}_f$)는 $Nd_2O_3$첨가에 따라 최초의 $+68\;ppm/^{\circ}C$에서 30wt% $Nd_2O_3$ 첨가시 $-46\;ppm/^{\circ}C$까지 변화함을 알 수 있었다. $0.3CaTiO_3-0.7(Li_{1/2}Nd_{1/2})TiO_3에\;Nd_2O_3$를 9wt% 첨가하여 $1425^{\circ}C$에서 3시간동안 소결한 시편에서 유전율(${\varepsilon}_r$)은 108, $Q{\cdot}f_{0}(GHz)$값은 3533, 공진주파수의 온도계수(${\varepsilon}_f$)가 $+6\;ppm/^{\circ}C$인 우수한 마이크로파 유전특성을 얻을 수 있었다.

• 한국전기전자재료학회논문지
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• 제29권12호
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• pp.781-785
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• 2016

With trend of the miniaturization and the high-functionalizing of mobile communication system, low-loss microwave dielectric materials are widely used for high frequency communication components. These dielectric materials should be co-sintered with highly electric-conducting metal such as silver or copper for high-frequency and thick film process application. Sintering temperature of $Ca(Li_{1/3}Nd_{2/3})_{0.2}Ti_{0.8}]O_{3-{\delta}}$, which has excellent dielectric properties such as ${\varepsilon}_r$ above 40, quality factor ($Q{\cdot}f_0$) above 16,000 GHz, and TCF (temperature coefficient of resonant frequency) of $-20{\sim}-10ppm/^{\circ}C$, is reported as high as $1,175^{\circ}C$, so it could not be co-sintered with silver or copper. Therefore in this study, low-temperature melting glasses of Zn-B-O and Zn-B-Si-O systems were added to $Ca[(Li_{1/3}Nb_{2/3})_{0.8}Ti_{0.2}]O_{3-{\delta}}$ to lower its sintering temperature under $900^{\circ}C$ without losing excellency of dielectric properties. With 15 weight % of Zn-B-Si-O glass and sintered at $875^{\circ}C$, specimen showed density of $4.11g/cm^3$, ${\varepsilon}_r$ of 40.1, $Q{\cdot}f_0$ of 4,869 GHz, and TCF of $-5.9ppm/^{\circ}C$. With 15 weight % of Zn-B-O glass and sintered at $875^{\circ}C$, specimen showed density of $4.14g/cm^3$, ${\varepsilon}_r$ of 40.4, $Q{\cdot}f_0$ of 7,059 GHz, and TCF of $-0.92ppm/^{\circ}C$.

• 한국세라믹학회지
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• 제40권10호
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• pp.925-930
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• 2003

The dielectric polarizability-related factors contributing to the $\tau$$_{\varepsilon}$ have been analysed in terms of dielectric permittivity $\varepsilon$, Tolerance Factor (TF), and octahedron tilt angles in (1-x)CaTi $O_3$-x[A(B', B″) $O_3$] (A=Ca, La, Li, B'=Al, Fe, Mg, B″=Nb, Ta) and (S $r_{0.2}$C $a_{0.8}$)( $Ti_{1-x}$ Z $r_{x}$) $O_3$. All the compounds have the orthorhombic Pbnm structure except the end members A(B', B″) $O_3$ and the solid solutions of x$\geq$0.8. The additional dipole field effect is suggested as a dominant factor contributing to $\tau$$_{\varepsilon}$ in CaTi $O_3$-based ceramics having relatively large $\varepsilon$, which has not been generally considered in the previous reports dealing with the $\tau$$_{\varepsilon}$. This study has been focussed on delineating the dipole field effect on the $\tau$$_{\varepsilon}$ in comparison to the octahedron tilt effect in CaTi $O_3$-based ceramics.cs..cs.

• 한국전기전자재료학회논문지
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• 제19권5호
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• pp.417-421
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• 2006

In this study, in order to develop low temperature sintering piezoelectric ceramics for LTCC (Low-Temperature Cofired Ceramic) multilayer piezoelectric actuator, PMW-PMN-PZT ceramics using $0.2wt%\; Li_2CO_3$ and $0.25wt%\;CaCO_3$ as sintering aids were investigated according to the varation of PMW substution. Composition ceramics could be sintered at $900^{\circ}C$ by adding sintering aids. As the amount of PMW substitution increased, the crystal structure of PMW-PMN-PZT ceramics moved from tetragonal phase to rhombohedral phase gradually, and MPB(Morphotrophic Phase Boundary) region appeared at 2 mol% PMW substitution. At the sintering temperature of $900^{\circ}C$, the density, electromechanical coupling factor(kp), mechanical quality factor(Qm), dielectric constant(${\epsilon}r$), piezoelectric constant(d33) and Curie temperature(Tc) of 2 mol% PMW substituted PMW-PMN-PZT ceramics showed the optimal values of $7.88g/cm^3$, 0.58, 1002, 1264, 352 pC/N and $336^{\circ}C$, respectively, for LTCC multilayer piezoelectric actuator application.

• 한국전기전자재료학회논문지
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• 제28권9호
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• pp.577-580
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• 2015

In this paper, in order to develop the composition ceramics with the outstanding piezoelectric properties, $Pb(Mg_{1/2}W_{1/2})_{0.03}(Ni_{1/3}Nb_{2/3})_{0.09}(Zr_{0.5}Ti_{0.5})_{0.88}O_3$ ceramics substituted with $BiFeO_3$ were prepared by the conventional solid-state reaction method. The addition of small amount of $Li_2CO_3$ and $CaCO_3$ as sintering aids decreased the sintering temperature of the ceramics. The effects of $BiFeO_3$ substitution on their piezoelectric and dielectric properties were investigated. when 0.015 mol $BiFeO_3$ was substituted, the optimal physical properties of $d_{33}=590pC/N$, $E_c=8.78kV/mm$ were obtained.