• Proceedings of the Korean Ceranic Society Conference
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• 2003.10a
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• pp.204.1-204
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• 2003

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.6
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• pp.558-566
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• 2003

We fabricated thick film monopole antennas using Li-doped BiNbO$_4$ ceramics and investigated their electrical properties as a function of the Li-doping concentration. Compared with undoped BiNbO$_4$ ceramics, addition of Li$_2$CO$_3$ improved dielectric constant by increasing of ionic polarization, but reduced quality value by increasing of lattice distortion. Antenna properties like gain, bandwidth and radiation patterns were also greatly affected by the addition of Li$_2$CO$_3$. With increasing amount of Li$_2$CO$_3$, the bandwidth of ceramic monopole antenna was increased to 81.7 %, but the gain was reduced to -10.03 dBi. Also radiation patterns were so distorted and showed low dB value by increasing of dielectric loss.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.313-314
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• 2006

$BiNbO_4$ ceramics were sintered under the presence of zinc-borosilicate(ZBS) glass and resultant microwave dielectric properties were investigated with a view to applying the composition to LTCC technology. The addition of 5~20 wt% ZBS glass ensured successful sintering below $900^{\circ}C$. In general, increased addition of ZBS glass increased sinterability and temperature coefficient of resonant frequency(${\tau}_f$), but it decreased the dielectric constant(${\varepsilon}_r$) and quality factor($Q{\times}f_0$) significantly due to the formation of an excessive liquid. The sintered $BiNbO_4$ ceramics at $900^{\circ}C$ with 15 wt% ZBS glass demonstrated 25 in dielectric constant(${\varepsilon}_r$), 3,700 in quality factor($Q{\times}f_0$), and -32 $ppm/{\circ}C$ in temperature coefficient of resonant frequency(${\tau}_f$).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.346-347
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• 2006

기계적 품질계수(Qm)를 향상시키기 위해 $Y_2O_3$와 $MnO_2$를 첨가함에 따른 $SrBi_2Nb_2O_9$ 세라믹스의 강유전 특성을 알아보았다. 합성분말의 입도를 분석 한 결과 $SrBi_2Nb_2O_9$의 경우 781.27nm였고, $Y_2O_3$와 $MnO_2$를 첨가한 경우 각 각 830.4nm와 981.1nm로 particle size는 증가하였고, 소결 후 소결밀도는 차이가 거의 없었으며, grain size는 $SrBi_2Nb_2O_9$과 $Y_2O_3$를 첨가했을 경우 $1{\mu}m$이하이며 반면, $MnO_2$를 첨가하였을 때 결정립이 성장하여 $3{\sim}4{\mu}m$로 나타났다. 또한, 모두가 $450^{\circ}C$ 이상의 상전이온도를 갖았다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.300-304
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• 2002

We fabricated thick film monopole antennas using Mo-doped $BiNbO_{4}$ ceramics and investigated their electrical properties as a function of the Mo-doping concentration. Compared with undoped $BiNbO_{4}$ ceramics, 10 at.% Mo-doping improved microwave dielectric properties of ceramics by increased sintered density as well as decreased space charge density. Further increase in the Mo-doping concentration caused formation of $Bi_{2}MoO_{6}$ phases, resulting in deterioration of the microwave characteristics. The gain and bandwidth of the ceramic monopole antenna were also greatly affected by the Mo-doping concentration. When Mo-doping concentration was 10 at%, highest gain of ~0.7dBi with lowest bandwidth of 30% at 2.3GHz was obtained.

• 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.35 no.10
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• pp.1040-1048
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• 1998

Ferroelectric properties of{{{{ { { { {SrBi }_{2 }Ta }_{2-x }Nb }_{x }O }_{9 } }} (SBIN) thin films were affected by the amount of Bi content in SBTN. The addition of Bi into the SBTN films could be accomplished by heat treating SBTN/Bi2O3/SBTN het-erostructures fabricated by r.f. magnetron sputtering method. The variation of Bi content was controlled by changing the thickness of the sandwiched Bi2O3 in SBTN/Bi2O3/SBTN heterostructure from 50 to 400$\AA$. As changing the thickness of the sandwiched Bi2O3 in Bi2O3 films was increased from 0 to 100$\AA$ the grain grew faster and the ferroelectric pro-perties were improved. On the other hand when the thickness of Bi2O3 films was thicker than 150$\AA$ the fer-roelectric properties were deteriorated Especially for SBTN thin films inserted by 400$\AA$ Bi2O3 layer a Bi2Phase appeared as a second phase resulting in poor ferroelectric properties. The maximum remanent po-larization (2Pr) and coercive field(Ec) were obtained for the SBTN/Bi2O3/(100$\AA$)/SBTN thin films. In this case 2Pr and Ec were 14.75 $\mu$C/cm2 and 53.4kV/cm at an applied voltage of 3V respectively.

• Transactions on Electrical and Electronic Materials
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• v.8 no.2
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• pp.84-88
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• 2007

[ $Bi_{1.5}Zn_{1.0}Nb_{1.5}O_7$ ] (BZN), $Bi_2Mg_{2/3}Nb_{4/3}O_7$ (BMN), and $Bi_2Cu_{2/3}Nb_{4/3}O_7$ (BCN) pyrochlore thin films were prepared on $Cu/Ti/SiO_2/Si$ substrates by pulsed laser deposition and the micro-structural and electrical properties were characterized for embedded capacitor applications. The BZN, BMN, and BCN films deposited at $25\;^{\circ}C$ and $150\;^{\circ}C$, respectively show smooth surface morphologies and dielectric constants of about $39\;{\sim}\;58$. The high dielectric loss of the films deposited at $150\;^{\circ}C$ compared with films deposited at $25\;^{\circ}C$ was attributed to the defects existing at interface between the films and copper electrode by an oxidation of copper bottom electrode. The leakage current densities and breakdown voltages in 200 nm thick-BMN and BZN films deposited at $150\;^{\circ}C$ are approximately $2.5\;{\times}\;10^{-8}\;A/cm^2$ at 3 V and above 10 V, respectively. Both BZN and BMN films are considered to be suitable materials for embedded capacitor applications.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.439-442
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• 2004

The effects of sintering additives on the low-temperature sintering and microwave dielectric properties of $Mg_4Nb_2O_9$ dielectric ceramics were studied. When $3{\sim}20wt%$ of $0.242Bi_2O_3-0.758V_2O_5$ was added, the sintering temperature decreased from $1100{\sim}1300^{\circ}C$ to $950^{\circ}C$ and high density was obtained. When $Mg_4Nb_2O_9$ was sintered at $950^{\circ}C$ with 10wt% of sintering additive, the microwave dielectric properties of $Q{\times}f_0\;=\;80.035GHz,\;\epsilon_r\;=\;13.3\;and\;\tau_f\;=\;-12.9\;ppm/^{\circ}C$ were obtained.

• Advances in materials Research
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• v.5 no.2
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• pp.93-105
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• 2016

KNN-based ceramics modified with small amounts of $Bi_4Zr_3O_{12}$ (BiZ) has been synthesized using high-throughput experimentation (HTE). The results from X-ray diffraction show that for samples with base composition $(K_{0.5}Na_{0.5})NbO_3$ (KNN), the phase present changes from orthorhombic to pseudo-cubic with more than 0.2 mol% BiZ addition; for samples with base composition $(K_{0.48}Na_{0.48}Li_{0.04})(Nb_{0.9}Ta_{0.1})O_3$ (KNNLT), the phase present changes from a mixture of orthorhombic and tetragonal symmetry to pseudo-cubic with more than 0.4 mol % while for samples with base composition $(K_{0.48}Na_{0.48}Li_{0.04})(Nb_{0.86}Ta_{0.1}Sb_{0.04})O_3$ (KNNLST), the phase present is tetragonal with <0.3 mol% BiZ addition and transforms to pseudo-cubic with more dopant addition. The microstructures of the samples show that addition of BiZ decreases the average grain size and increases the volume of pores at the grain boundaries. The values of dielectric constant for KNN and KNNLT compositions increase slightly with BiZ addition while that for KNNLST decreases gradually with BiZ addition. The dielectric loss values are between 0.02 and 0.04 for KNNLT and KNNLST compositions while they are ~ 0.05 for KNN samples. The resistivity values increases with BiZ addition and values in the range of $10^{10}{\Omega}cm$ and $10^{12}{\Omega}cm$ are obtained. The piezoelectric charge coefficient ($d{^*}_{33}$) is highest for KNNLST samples and decreases gradually from ~400 pm/V to ~100 pm/V with BiZ addition.