• Title/Summary/Keyword: microwave dielectric properties

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Evaluation of Microwave Dielectric Properties of MgO-TiO2 System by Dielectric Mixing Rules

  • Kim, Eung-Soo;Seo, Seock-No
    • Journal of the Korean Ceramic Society
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    • v.47 no.2
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    • pp.163-168
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    • 2010
  • Effects of compositions on the microwave dielectric properties of the MgO-$TiO_2$ system were investigated as a function of the molar ratio of MgO to $TiO_2$ ($0.9{\leq}MgO/TiO_2\;(x){\leq}1.2$). With the compositional changes, secondary phases of $MgTi_2O_5$ and $Mg_2TiO_4$ were also detected along with $MgTiO_3$. Microwave dielectric properties of the specimens were dependent on the types of phases developed in the sintered specimens. A single phase of $MgTiO_3$ showed a dielectric constant (K) of 18.2, a quality factor (Qf) of 198,000 GHz, and a temperature coefficient of resonant frequency (TCF) of $-51\;ppm/^{\circ}C$. However, the dielectric properties of the specimens with a secondary phase of $MgTi_2O_5$ (K=19.9, Qf=48,000 GHz) and/or $Mg_2TiO_4$ (K=15.6, Qf=56,000 GHz) were worsened. Dependence of the microwave dielectric properties on the secondary phase of the MgO-$TiO_2$ system was also discussed in terms of dielectric mixing rules.

Effect of Dopants on the Microwave Dielectric Properties of $(1-x)MgTiO_3-xCaTiO_3$ Ceramics (불순물 첨가에 따른 $(1-x)MgTiO_3-xCaTiO_3$ 세라믹스의 마이크로웨이브 유전특성변화)

  • 우동찬;이희영;한주환;김태홍;최태구
    • Journal of the Korean Ceramic Society
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    • v.34 no.8
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    • pp.843-853
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    • 1997
  • The effect of dopant on microwave dielectric properties of (1-x)MgTiO3-xCaTiO3 ceramics, known to be used as microwave dielectric resonators for global positioning system and personal communication system, has been analyzed in terms of variations in defect concentrations and microstructural features with its addition. The addition of dopants was revealed to result in a significant change in the microstructure as well as defect concentration of the ceramics. For instance, the quality factor is proportional to sintered density of the ceramics by inversely proportional to grain size as well as vacancy concentration. Accordingly, it is believed that the dopant effect on the microwave dielectric properties should be separately analyzed with either microstructural change or the change in vacancy concentration.

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Dielectric Properties of Agricultural Properties and Their Use in Moisture Sensing and Other Applications

  • Nelson, Stuart O.
    • Proceedings of the Korean Society for Agricultural Machinery Conference
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    • 1996.06c
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    • pp.293-304
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    • 1996
  • Historical interest in dielectric properties of agricultural products and definitions of dielectric terms and basic principles governing their influence on elelctromagnetic energy are presented briefly . The nature of dielectric properties variation with frequency, temperature , and product density is discussed, Graphical data on the dielectric properties of products are presented that illustrate the dependence of these properties on moisture content, frequency, temperature, and density. Applications microwave dielectric properties of agricultural products are cited that include radio-frequency (RF) and microwave heating for seed treatment, improvement of nutritional and keeping qualities of some products, and controlling insects in grain. Uses of dielectric properties for product quality measurement and the rapid determination of moisture content are described. Principle of moisture determination in bulk grain by RF and microwave measurements are briefly presented.

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Microwave Dielectric Properties of Low-temperature Sintered $Mg_4Nb_2O_9$ Ceramics (저온소결 $Mg_4Nb_2O_9$ 세라믹스의 마이크로파 유전특성)

  • Lee, Ji-Hun;Bang, Jae-Cheol
    • 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.

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Numerical Method for Computing the Resonant Frequencies and Q-factor in Microwave Dielectric Resonator

  • Kim, Nam-young;Yoo, Hojoon
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1997.04a
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    • pp.245-248
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    • 1997
  • The dielectric resonators(DRs) with dielectric properties are widely used in microwave integrated circuit(MICs) and monolithic microwave integrated circuits(MMICS). The variational method as numerical simulation scheme would be applied to calculate the resonant frequencies(fr) and Q-factors of microwave dielectric resonators. The dielectric resonator with a cylindrical “puck” structure of high dielectric material is modeled in this simulation. The parameters, such as the diameter, the height, and the dielectric constant of dielectric resonator, would determine the resonant frequency and the Q-factor. The relationship between these parameters would effect each other to evaluate the approximate resonant frequency. This simulation method by the variational formula is very effective to calculate fr, and Q-factor. in high frequency microwave dielectric resonator The error rate of the simulation results and the measured results would be considered to design the microwave dielectric resonators.

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Dielectric Properties of Ceramic/Polymer Composites at Microwave Frequencies

  • Kim, Eung-Su;Jeon, Chang-Jun
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2011.05a
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    • pp.19.1-19.1
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    • 2011
  • Effects of particle size, crystal structures and multilayer structures of $ATiO_3$, $ATa_2O_6$, $ANb_2O_6$, $AWO_4$, and $AMoO_4$ (A=Ni, Mg, Zn, Co) ceramic fillers on the dielectric properties of polystyrene (PS), polypropylene (PP) and polytetrafluoroethylene (PTFE) polymer matrices were investigated at microwave frequencies. The microwave dielectric properties of $ATiO_3$ (ilmenite), $ATa_2O_6$ (tri-rutile), $ANb_2O_6$ (columbite), AWO4 (wolframite), and AMoO4 (wolframite) ceramics were largely dependent on the structural characteristics of oxygen octahedra. The dielectric constant (K) of the composites was increased with the ceramic content. However, the dielectric loss (tan ${\delta}$) of the composites was affected by the type of ceramics and the crystallinity of polymers. For the composites with same amount of ceramics, the K was decreased and the tan ${\delta}$ was increased with the particle size of ceramics. Also, the dielectric properties of the composites were dependent on the multilayer structures with different arrangements. Several theoretical models have been employed to predict the effective dielectric properties of the composites. The frequency dependence of dielectric properties and the temperature coefficient of resonant frequency (TCF) of the composites were also discussed.

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Synthesis and Microwave Dielectric Properties of $La(Zn_{1/2}Ti_{1/2})O_3$ ($La(Zn_{1/2}Ti_{1/2})O_3$의 합성 및 고주파 유전특성)

  • 서명기;조서용;홍국선;박순자
    • Journal of the Korean Ceramic Society
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    • v.33 no.9
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    • pp.1019-1023
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    • 1996
  • The dielectric properties at microwave frequencies of B site complex perovskite La(Zn1/2Ti1/2)O3 which has +3 ion in A site were investigated. maximum Q*F value of the specimens was 59000 dielectric constant 34, temperature coefficient of resonant frequency -52 ppm/$^{\circ}C$. XRD pattern of the sintered specimen shows (111) ssuperlattice reflection which indicates Zn and Ti cation ordering.

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Effects of Crystal Structure on Microwave Dielectric Properties of Ceramics

  • Kim, Eung-Soo;Jeon, Chang-Jun;Kim, Sung-Joo;Kim, Su-Jung
    • Journal of the Korean Ceramic Society
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    • v.45 no.5
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    • pp.251-255
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    • 2008
  • Microwave dielectric properties of $MgTiO_3,\;MgWO_4,\;MgNb_2O_6$, and $MgTa_2O_6$ were investigated based on the structural characteristics. The dielectric constant (K) was dependent on the dielectric polarizabilities of the specimens, and the deviation of the observed dielectric polarizabilities (${\alpha}_{obs.}$) from the theoretical dielectric polarizabilities (${\alpha}_{theo.}$) were decreased with increasing of Mg-site bond valence. Quality factors (Qf) were affected by the sharing type of $MgO_6$ and $BO_6$ octahedra. Temperature coefficient of resonant frequency (TCF) was decreased with increasing of average octahedral distortion.

A Study on the Microwave Dielectric Properties of 0.182BaO-0.818TiOS12T Ceramics (0.182BaO-0.818TiO2 세라믹스의 마이크로파 유전특성에 관한 연구)

  • 박인길;이영희;윤석진;정형진
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.43 no.3
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    • pp.442-446
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    • 1994
  • In this study, microwave dielectric properties of 0.182BaO-0.818TiOS12T ceramics were investigated with sintering temperature and annealing time, and the application for the microwave dielectric resonator was studied. In the specimen simtered at 1400[$^{\circ}C$], dielectric constant, unloaded Q and temperature coefficient of resonant frequency had good values of 35.36, 5692, -4.43[ppm/$^{\circ}C$], respectively. The specimen which temperature coefficient of resonant frequency($\tau$f) was vared positive to negative value was selected, thereafter microwave dielctric properties was investigated with annealing time(0~4[hr]) in the fixed annealing temperature of 1350[$^{\circ}C$]. Increasing the annealing time, dielectric constant and unloaded Q were increased and temperature coefficient of resonant frequency was decreased.

Microwave Dielectric Properties of xZnO+{1-x)$TiO_2$ Ceramic Systems (xZnO+(1-x)$TiO_2$계 세라믹의 마이크로파 유전특성)

  • Sim, Woo-Sung;Bang, Jae-Cheol
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2002.07b
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    • pp.605-608
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    • 2002
  • In order to improve the microwave dielectric properties of ZnO+$TiO_2$ ceramic systems, we studied the relations among microstructures, phases, and microwave dielectric properties at various mole ratio and sintering temperatures. The optimum composition was found to be 0.2ZnO+0.8$TiO_2$ when sintered at $1100^{\circ}C$, at which we could obtain following results: $Q{\times}f_o$ = 22,500 GHz, ${\varepsilon}_r$ = 73, and $\tau_f=+210ppm/^{\circ}C$.

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