• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.5
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• pp.397-403
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• 2003

Microwave dielectric properties of (1-x)ZnW $O_4$-xTi $O_2$ ceramic systems were investigated with calcination temperatures and Ti $O_2$ contents. The ZnW $O_4$ ceramic could be suitably sintered at 1075$^{\circ}C$ and showed the dielectric constant of 13.6, quality factor(Q$\times$ $f_{O}$value) of 22,000 and temperature coefficient of resonant frequency($\tau$$_{f}$) of -65$\pm$2ppm/$^{\circ}C$. Increasing the amount of Ti $O_2$ in the range of 0.25 to 0.45 mol, the dielectric constant and $\tau$$_{f}$ increased due to the role of Ti $O_2$ but the quality factor decreased due to the increase of phase boundaries. The 0.7ZnW $O_4$-0.3Ti $O_2$ ceramic showed the dielectric constant of 19.8, qualify factor(Q$\times$ $f_{0}$) of 20,000 and $\tau$$_{f}$ of -3$\pm$1ppm/$^{\circ}C$.>.EX>.>.>.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.642-645
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• 2002

Microwave dielectric properties of $ZnWO_4$ ceramic were investigated with calcination and sintering temperatures. The dielectric properties required for such application are high dielectric constant$(\varepsilon_r)$, high $Q{\times}f_o$ value and low temperature coefficient of resonant frequency$(\tau_f)$. These requirement correspond to necessities for size reduction, excellent frequency selectivity, good temperature stability of devices. $ZnWO_4$ ceramics could be sintered at low $1075^{\circ}C$, which was comparatively low temperature for microwave dielectrics. As a result, $ZnWO_4$ showed the dielectric constant of 13, quality factor($Q{\times}f_o$ value) of 22000 and 'temperature coefficient of resonant frequency$(\tau_f)$ of $-65{\pm}5ppm/^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.131-134
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• 2003

[ $ZnWO_4$ ] shows excellent frequency selectivity due to its high quality factor($Q{\times}f$) at microwave frequencies. However, in order to use $ZnWO_4$ as multilayered wireless communication components, its other properties such as sintering temperature($1050^{\circ}C$), ${\tau}_f$ ($-70ppm/^{\circ}C$) and ${\varepsilon}_r(15.5)$ should be modified. In present study, $TiO_2$ and LiF were used to improve the microwave dielectric and sintering properties of $ZnWO_4$. $TiO_2$ additions to $ZnWO_4$ changed ${\tau}_f$ from negative to positive value, and also increased ${\varepsilon}_r$ due to its high ${\tau}_f$ ($+400ppm/^{\circ}C$) and ${\varepsilon}_r$(100). At 20 mol% $TiO_2$ addition, ${\tau}_f$ was controlled to near zero $ppm/^{\circ}C$ with ${\varepsilon}_r=19.4$ and $Q{\times}f=50000GHz$. However, the sintering temperature was still high to $1100^{\circ}C$. LiF addition to the $ZnWO_4+TiO_2$ mixture was greatly reduced the sintering temperature from $1100^{\circ}C$ to $850^{\circ}C$ due to liquid phase formation. Also LiF addition decreased the ${\tau}_f$ value due to its high negative ${\tau}_f$ value. Therefore, by controlling the $TiO_2$ and LiF amount, temperature stable LTCC material in the $ZnWO_4$-TiO_2-LiF$ system could be fabricated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.64-67
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• 1997

Microwave dielectric properties of A1$_2$O$_3$ ceramics resonator were investigated with impurity addition. Increasing the contents of Bi$_2$O$_3$Q-value and Q $\times$ f were increased. In the specimen with the content of Bi$_2$O$_3$(0.3wt%), dielectric constant, quality factor and temperature coefficient of resonant frequency(TCRF, $\tau$$_{f}$) had a good values of 10.76,23,253(at 9.68[GHz]) and -39.09(ppm/$^{\circ}C$), respectively. The TCRF value was decreased with MnO$_2$ and increased with Sm$_2$O$_3$. La$_2$O$_3$.>.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.143-148
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• 2001

PbWO$_4$ can be densified at 85$0^{\circ}C$ and it shows fairy good microwave dielectric properties; dielectric constant($\varepsilon$$_{r}$) of 21.5, quality factor(Q $\times$f$_{0}$) of 37,224 GHz, and temperature coefficient of resonant frequency($\tau$/suf f/) of -31ppm/$^{\circ}C$. Due to its low sintering temperature, PbWO$_4$ can be used as a multilayered chip component at microwave frequency with high electrical performance by using high conductive electrode metals such as Ag and Cu. However, in order to use this material for microwave communication devices, the $\tau$$_{f}$ of PbWO$_4$ must be stabilized to near zero with high Q$\times$f$_{0}$. In present study, PbWO$_4$ was modified by adding TiO$_2$, B$_2$O$_3$, and CuO in order to improve the microwave dielectric properties without increasing the sintering temperature. The addition of TiO$_2$ increased the $\tau$$_{f}$ and $\varepsilon$$_{r}$, due to its high rr(200ppm/$^{\circ}C$) and $\varepsilon$$_{r}$(100). However, the addition of TiO$_2$ reduced the Q$\times$f$_{0}$ value. When the mot ratio of PbWO$_4$ and TiO$_2$ was 0.913:7.087, near zero $\tau$$_{f}$(0.2ppm/$^{\circ}C$) was obtaibed with $\varepsilon$$_{r}$=22.3, and Q$\times$f/$_{0}$=21,443GHz. With this composition, various amount of B$_2$O$_3$ and CuO were added in order to improve the quality factor. The addition, of B$_2$O$_3$ decreased the $\varepsilon$$_{r}$. However, increased Q$\times$f$_{0}$ and $\tau$$_{f}$. When 2.5 wt% of B$_2$O$_3$ was added to the 0.913PbWO$_4$-0.087TiO$_2$ ceramic, $\tau$$_{f}$ =8.2, $\varepsilon$$_{r}$=20.3, Q$\times$f$_{0}$=54784 GHz. When CuO added to the 0.913PbWO$_4$-0.087TiO$_2$ ceramic, $\tau$$_{f}$ was continuously decreased. And $\varepsilon$$_{r}$ . and Q$\times$f$_{0}$ were increased up to 1.0 wt% then decreased. At 0.1 wt% of CuO addition, the 0.913PbWO$_4$-7.087Ti0$_2$ Ceramic Showed $\varepsilon$$_{r}$=23.5, $\tau$$_{f}$=4.4ppm/$^{\circ}C$, and Q$\times$f$_{0}$=32,932 GHz.> 0/=32,932 GHz.X>=32,932 GHz.> 0/=32,932 GHz.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.7
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• pp.305-310
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• 2002

The microwave dielectric properties of Ba(Mg$_{1}$3/Ta$_{2}$3/O$_3$-Ba(Co$_{1}$3/Nb$_{2}$3/O$_3$[BMT-BCN] ceramics were investigated. The specimens were prepared by the conventional mixed oxide method with the sintering temperature of 15$25^{\circ}C$~1575$^{\circ}C$. It was found that Ba(Mg$_{1}$3/Ta$_{2}$3/O$_3$[BMT] and BCN formed a solid solution with complex perovskite structure. As increasing the mole fraction of BCN, dielectric constant increased while the temperature coefficient of resonant frequency was changed from positive to negative value. The highest value of quality factor, Q$\times$f$_{0}$=138,205GHz, obtained in the 0.9BMT-0.1BCN ceramics sintered at 1575$^{\circ}C$. In the range of x$\geq$0.4, the dielectric constant was about 30. The 0.55BMT-0.45BCN ceramics sintered at 15$25^{\circ}C$ for 5 hours showed the microwave dielectric properties of $\varepsilon$$_{r}$=30.21, Q$\times$f$_{0}$=85,789GHz and $\tau$$_{f}$=2.9015ppm/$^{\circ}C$.EX>.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.9
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• pp.826-834
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• 2004

In this paper, we fabricated thick film monopole antennas using Bi$_2$O$_3$-doped BaTi$_4$$O_{9}$ ceramics for small size and broadband intenna. In the result, the high permittivity was fixed and the quality factor was also significantly decreased by the formation of secondary phase of Bi$_4$Ti$_3$O$_{12}$ repleced by addtion Bi. The antenna property influenced by the quality value more than the permittivity. The bandwidth of antenna was increased to 33 %. On the other hand, the gain was reduced to -4.3 dBi. Also radiation patterns were showed low dBi value by increasing of dielectric loss. Specially, Measured x-y plane radiation patterns was distorted as the dispersion of wavelength and high permittivity difference. But the result is showed execellent bandwidth because of low quality value in all formation range.nge.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.4 no.4
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• pp.341-345
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• 2003

ZnWO$_4$shows excellent frequency selectivity due to its high quality factor(Q${\times}$f) at microwave frequencies. However, in order to use ZnWO$_4$as multilayered wireless communication components, its other properties such as sintering temperature(105$0^{\circ}C$). $$\tau$_f$(-70ppm/$^{\circ}C$) and $$\varepsilon$_r$(15.5) should be modified. In present study, TiO$_2$and LiF were used to improve the microwave dielectric and sintering properties of ZnWO$_4$. TiO$_2$ additions to ZnWO$_4$changed $\tau$$_{f}$ from negative to positive value, and also increased $$\varepsilon$_r$, due to its high $$\tau$_f$(＋400ppm$^{\circ}C$) and $$\varepsilon$_r$(100). At 20 mol% TiO$_2$ addition, $$\tau$_f$was controlled to near zero ppm/$^{\circ}C$ with $$\varepsilon$_r$=19.4 and Q${\times}$ f=50000GHz. However, the sintering temperature was 110$0^{\circ}C$. LiF addition to the ZnWO$_4$＋TiO$_2$ mixture greatly reduced the sintering temperature from 110$0^{\circ}C$ to 85$0^{\circ}C$ due to liquid phase formation. Also LiF addition decreased the $$\tau$_f$value due to its high negative $$\tau$_f$ value. Therefore, by controlling the TiO$_2$and LiF amount. temperature stable LTCC(Low Temperature Cofired Ceramics) material with low loss in the ZnWO$_4$-TiO$_2$-LiF system could be fabricated.d.d.

• Journal of the Korean Ceramic Society
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• v.55 no.4
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• pp.364-367
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• 2018

The phase evolution, microstructure, and microwave dielectric properties of Sr-substituted $Ba(Mg_{0.5}W_{0.5})O_3$ ceramics, i.e., $(Ba_{1-x}Sr_x)(Mg_{0.5}W_{0.5})O_3$ ($0{\leq}x{\leq}0.30$), sintered at $1700^{\circ}C$ for 1 h were investigated. All compositions showed a 1 : 1 ordered perovskite structure. In all the compositions, $BaWO_4$ was detected as the secondary phase. With increasing x in ($Ba_{1-x}Sr_x$) $(Mg_{0.5}W_{0.5})O_3$, the lattice parameter increased linearly, indicating that a substitutional solid solution occurred. All compositions exhibited a dense microstructure. The value of ${\varepsilon}_r$ increased slightly with increasing x. The value of $Q{\times}f_0$ increased with the increase in x up to x = 0.10 and reached a saturated value of about 100,000 GHz. The composition for x = 0.20, i.e., $(Ba_{0.80}Sr_{0.20})(Mg_{0.5}W_{0.5})O_3$, sintered at $1700^{\circ}C$ for 1 h exhibited superior microwave dielectric properties of ${\varepsilon}_r=19.6$, $Q{\times}f_0=99,358GHz$, and ${\tau}_f=0.0ppm/^{\circ}C$, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.46-50
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• 2003

Crystal structure and microwave dielectric properties of $Ba(Mg_{1/3-x}Nb_{2/3})O_3$ (BMN) ceramics were investigated. $Ba(Mg_{1/3}Nb_{2/3})O_3$ has the 1:2 ordered hexagonal structure. The 1:2 ordering and relative density of specimens increased with small Mg deficiency(x). The variation of Q-value with Mg deficiency is very similar to that of 1:2 ordering and relative density. The highest $Q{\times}f_0$ achieved in this investigation is about 96,000 for $Ba(Mg_{1/3-0.02}Nb_{2/3})O_3$. The improvement of Q-value with Mg-deficiency is related to the increase of degree of ordering and relative density of the specimen.