• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2315-2317
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• 2005

In this paper, an iterative method to model the electromagnetic heating of electrically large lossy dielectrics is presented. Frequency domain finite element (FEM) solutions of the wave equation are determined for the lossy inhomogeneous dielectric as the material properties are change with temperature and time. The power absorbed from microwave losses is applied to a finite element time domain (FETD) calculation of the heat diffusion equation. Time steps appropriate for updating the piecewise material properties in the wave equation and the time stepping of the heat equation are presented. The effects of preheating and source frequency are investigated.

• Journal of the Microelectronics and Packaging Society
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• v.18 no.3
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• pp.39-43
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• 2011

Effects of cavity material on the Q-factor measurement of microwave dielectric materials were studied by HFSS simulation and the measurements using metal cavity. $TE_{01\delta}$ mode resonant frequency was determined from the electric and magnetic field patterns and the loaded Q-factor was calculated from 3dB bandwidth of $S_{21}$ spectrum. When the cavity metal materials were Cu, SUS and Au cavity, the level of Q-factor was similar. However, Q-factor was significantly decreased when the cavity metal material was CuO. The Q-factor measurements of dielectric resonator by network analyzer using various metal cavity exhibits consistent behavior.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.4
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• pp.232-240
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• 1999

In this study, the $(1-\chi)Ba(Mg_{\fraction one-third}Ta_{\fraction two-thirds}O_3-\chiBa(Co_{\fraction one-third}\Nb_{\fraction two-thirds})O_3$ ceramics($\chi$=0.3,0.4,0.5,0.6) were prepared by the conventional mixed oxide method. The ceramics were sintered at the temperature of $1500~1575^{\circ}C$ for5 hours in air. The BMT-BCN ceramics have a complex perovskite structure, and have peaks of (101), (102), (201), (202) and (212). Increasing the sintering temperature, dielectric constant was increased. Temperature coefficients of resonant frequency of the specimens were decreasing with increasing BCN content. In the case of the 0.7BMT-0.3BCN ceramics sintered at $1575^{\circ}C$ for 5 hours, dielectric constant, quality factor and temperature coefficient of resonant frequency for microwave dielectrics application were a good value of 28, 235500 at ㎓ and -$1.2 ppm/^{\circ}C$, respectively.

• 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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• 2003.05c
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• pp.249-252
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• 2003

The microwave dielectric properties of $0.7Mg_4Ta_2O_9-0.3TiO_2$ ceramics were investigated. All samples were prepared by the conventional mixed oxide method. The structural properties were investigated with sintering temperature by X-ray Diffractor meter. According to. the X-ray diffraction patterns of the $0.7Mg_4Ta_2O_9-0.3TiO_2$ ceramics, major phase of the hexagonal $Mg_4Ta_2O_9$ were appeared. In the case of $0.7Mg_4Ta_2O_9-0.3TiO_2$ ceramics sintered at $1400^{\circ}C$, dielectric constant, quality factor and temperature coefficient of resonant frequency were 11.72, 126,419GHz, $-31.82ppm/^{\circ}C$, respectively.

• Journal of the Korean Ceramic Society
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• v.38 no.4
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• pp.308-313
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• 2001

We report the effects of the V$_2$O$_{5}$ additive on the sintering behavior and microwave dielectric properties of ZnNb$_2$O$_{6}$ ceramics. Densification temperatures of V$_2$O$_{5}$-doped ZnNb$_2$O$_{6}$ samples are lowered to the range of 875-9$25^{\circ}C$ because of the liquid phase sintering. Doped samples are composed of a Zn(Nb,V)$_2$O$_{6}$ solid solution and second phases. Up to 5 wt% V$_2$O$_{5}$ is the only second phase, however, V$_2$O$_{5}$ also exists as the second phase for 10 wt% V$_2$O$_{5}$ addition. In comparison with reported values of undoped ZnNb$_2$O$_{6}$ ceramics, microwave properties of V$_2$O$_{5}$-doped ZnNb$_2$O$_{6}$ samples are seriously degraded, which is confirmed to originate from the second phases. The optimum microwave properties (Q$\times$f=13,800, $\varepsilon$$_{r}$=23, $\tau$$_{f}$=-66ppm/$^{\circ}C$) are obtained from ZnNb$_2$O$_{6}$ with the addition of 5 wt% V$_2$O$_{5}$ sintered at 90$0^{\circ}C$.90$0^{\circ}C$.EX>.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.314-314
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• 2008

The low temperature sintering and the dielectric properties of $Al_2O_3/SiO_2$-zinc borosilicate glass composites were investigated in the view of the application for LTCC. When the sintering was conducted at $900^{\circ}C$ $ZnAl_2O_4$ and $ZnB_2O_4$ compounds formed at the $Al_2O_3$-rich and the $SiO_2$-rich compositions, respectively. The reaction between ZBS glass and $Al_2O_3/SiO_2$ caused the formation of these compounds. The $Al_2O_3/SiO_2$ ratio affected the dielectric properties. The excellent dielectric properties, i.e., Q$\times$f value= 40,000 GHz and ${\varepsilon}_r$=4.5, were obtained in the $Al_2O_3/SiO_2$-ZBS glass system and fabricated the LTCC substrate materials.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.196-199
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• 2000

마이크로파용 세라믹 유전체로 사용되는 MgTiO$_3$-CaTiO$_3$계 유전체에 Li을 첨가하여 이때 얻어지는 마이크로파 유전특성과 소결특성에 대하여 알아보았다. 94MgTiO$_3$-6CaTiO$_3$으로 주조성을 고정시키고 여기에 Li$_2$CO$_3$를 Li원자 기준으로 0 ~ 10 mol% 범위 안에서 첨가하여 1200~140$0^{\circ}C$의 온도에서 4시간 소결하였다. Li의 첨가량이 적을 때에는 유전체의 품질계수와 유전상수가 모두 감소하였으나 약 lmol% 이상 되면 다시 증가하였으며, 이후 첨가량이 과도해지면 다시 서서히 감소하는 경향을 볼 수 있었다. 1.0 ~ 3.0 mol%의 첨가량 범위 안에서 Li은 MgTiO$_3$-CaTiO$_3$계 유전체의 품질계수를 증가시켜주는 역할을 하는 것으로 나타났다 1.5mol%의 Li을 첨가하고 1275$^{\circ}C$에서 4시간 소결한 시편에서 유전상수는($\varepsilon$$_{r}$) 20.0, Qf는 78,000 그리고 공진주파수 온도계수($\tau$$_{f}$)는 -1.6ppm/$^{\circ}C$의 결과를 얻을 수 있었다.다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.6
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• pp.356-360
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• 2017

We investigated the phase evolution, microstructure, and microwave dielectric properties of Na- and Zr-doped $Ba(Mg_{0.5}W_{0.5})O_3$ [i.e., ($Ba_{1-2x}Na_{2x})(Mg_{0.5-x}Zr_xW_{0.5})O_3$] ceramics. $BaWO_4$ as a secondary phase was observed in all compositions, and it increased as the dopant concentration increased. All specimens revealed a dense microstructure. For the composition of x=0.01, polyhedral grains were observed. As the dopant concentration increased, the densification and the grain growth were promoted by a liquid phase. The quality factor($Q{\times}f_0$) decreased remarkably, whereas the dielectric constant (${\varepsilon}_r$) tended to decrease as the dopant concentration increased. The dielectric constant, quality factor, and temperature coefficient of the resonant frequency of the composition of x=0.01 sintered at $1,700^{\circ}C$ for 1 h were 18.6, 216,275 GHz, and $-22.0ppm/^{\circ}C$, respectively.

• Journal of the Korean Ceramic Society
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• v.56 no.6
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• pp.526-533
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• 2019

Indialite/cordierite glass-ceramics demonstrate excellent microwave dielectric properties such as a low dielectric constant of 4.7 and an extremely high quality factor Qf of more than 200 × 10³ GHz when crystallized at 1300℃/20 h, which are essential criteria for application to 5G/6G mobile communication systems. The glass-ceramics applied to dielectric resonators, low-temperature co-fired ceramic (LTCC) substrates, and direct casting glass substrates are reviewed in this paper. The glass-ceramics are fabricated by the crystallization of glass with cordierite composition melted at 1550℃. The dielectric resonators are composed of crystallized glass pellets made from glass rods cast in a graphite mold. The LTCC substrates are made from indialite glass-ceramic powder crystallized at a low temperature of 1000℃/1 h, and the direct casting glass-ceramic substrates are composed of crystallized glass plates cast on a graphite plate. All these materials exhibit excellent microwave dielectric properties.