• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.11a
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• pp.59-63
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• 2002

Zinc-Magnesium borosilicate 유리에 CaF$_2$입자를 충진재로 첨가하여 혼합체의 소결거동, 결정화 거동 및 최종 소결체의 마이크로파 유전특성을 측정하였다. CaF$_2$첨가는 유리의 점도를 감소 시켜 결정화 및 수축개시온도를 감소시켰다. 이러한 CaF$_2$의 최대 첨가량은 주어진 유리조성에 있어서 15 vol. % 이었다. 이러한 소결성 및 결정화 개시온도의 변화는 모 유리와 CaF$_2$의 반응에 의한 결과로 보여지며 이 반응은 결정상의 변화나 이차상의 형성에는 영향을 미치지 않았다. 따라서 유전율 6.1에 품질계수가 40000GHz 인 CaF$_2$입자를 15 vol.% 첨가시 유전상수는 7.1에서 5.6로 품질계수는 2200에서 5000GHz로 유전특성이 향상되었고 소결온도는 75$0^{\circ}C$이었다.

• Korean Journal of Materials Research
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• v.6 no.11
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• pp.1121-1126
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• 1996

(Pb0.63Ca0.37)ZrO3 세라믹에 MgO와 SrO를 첨가하여 Ca를 Mg와 Sr 이온으로 치환하였을 때의 고주파 유전특성에 대해 연구하였다. Ca 이온의 일부를 Mg 이온으로 치환시킨 경우에는 A-O결합에 의한 분극의 증가로 인하여 유전상수는 직선적으로 증가하지만 품질계수는 감소한다. 또한 Ca 이온을 Sr 이온으로 치환시킨 경우에는 결합길이의 증가로 인해 분극이 감소되어 유전상수와 품질계수가 감소한다. 고주파용 유전재료의 설계에 있어서 관용인자와 이온결합성의 평가가 중요하다.

• Proceedings of the KAIS Fall Conference
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• 2003.06a
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• pp.87-90
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• 2003

B₂O₃침가에 따른 (Zn/sub 0.8.Mg/sub 0.2/)TiO₃계 세라믹스의 마이크로파 유전특성에 대하여 연구하였다. B₂O₃의 침가량에 비례하여 B₂O₃와 (Zn/sub 0.8.Mg/sub 0.2/)TiO₃와외 반응에 의한 TiO₂ 석출물의 양이 증가하며 공진주파수 온도계수가 증가하였다. 소결온도에 따라 액상의 양, 미세조직, TiO₂와 2차상의 석출거동이 상이하게 나타났다. 6.19mo1.％ B₂O₃물 첨가한 시편을 900℃에서 5시간 소결시 ε/sub r/ = 23.5, Q×f/sub o/ = 67,500 ㎓, T/sub f/ = -1.42 ppm/℃의 우수한 마이크로파 유전특성을 얻을 수 있었다.

• Proceedings of the KAIS Fall Conference
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• 2003.06a
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• pp.91-94
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• 2003

하소온도에 따른 (Zn/sub 0.8.Mg/sub 0.2/)TiO₃ 마이크로파 유전체 세라믹스의 소결거동과 마이크로파 유전특성의 변화를 연구하였다. 저온소결을 위하여 0.45 wt.％Bi₂O₃와 0.55wt.％V₂O/sub 5/를 첨가하였으며, 1000℃이하의 온도에서 소결하여 치밀한 소결체를 얻을 수 있었다. 800℃～1000℃의 범위의 여러 온도에서 하소를 하고 소결 전ㆍ후의 존재상과 미세구조의 분석을 통하여, 하소한 분말에 존재하는 미반응상 및 이차상이 최소화 될 때 높은 Q×f/sub o/값을 갖는 것을 알 수 있었다. 1000℃에서 하소한 후 900℃에서 소결했을 때, 주상이 Hexagonal이고 미세구조가 균일하였으며, 이때 Q×f/sub o/ = 42,000㎓, ε/sub r/ = 22를 나타냈다.

• Preventive Nutrition and Food Science
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• v.2 no.3
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• pp.269-279
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• 1997

Various nondestructive technologies for quality inspection of fruits and vegetables were reviewed through published literatures and selected agricultural databases. These technologies were grouped into nine categories, including acoustic response, dielectric response, machine vision, magnetic response, mechanical vibration response, microwave response, optical properties, and other possible sensing technologies. Their principles and characteristics were investigated and these technologies were presented with their current and potential applications. The link of appropriate nondestructive technologies with common principal quality parameters of fruits and vegetables was summarized.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1485-1487
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• 2002

The 0.96Mg$TiO_3$-0.04Sr$TiO_3$ ceramics with $V_2O_5$(5wt%) were prepared by the conventional mixed oxide method. The structural properties were investigated with sintering temperature by XRD and SEM. According to the X-ray diffraction patterns of the 0.96Mg$TiO_3$-0.04Sr$TiO_3$ceramics with $V_2O_5$(5wt%), the ilmenite $MgTiO_3$ and perovskite $SrTiO_3$ structures were coexisted and secondary phase $MgTi_2O_5$ were appeared. Increasing the sintering temperature, the grain size was increased and three types of grains were exhibited: larger circular grain, small square grain and lapth-shaped grain. In the case of 0.96Mg$TiO_3$-0.04Sr$TiO_3$ ceramics with $V_2O_5$(10wt%), dielectric constant, quality factor and temperature coefficient of resonant frequency were $15.24{\sim}18.55$, $22,890{\sim}42,100$GHz, -24.5${\sim}$+2.414ppm/$^{\circ}C$, respectively.

• Journal of the Korean Magnetics Society
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• v.19 no.6
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• pp.203-208
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• 2009

Magnetic and Ka-band absorbing properties have been investigated in Ti-Co substituted M-type barium hexaferrites with $BaTi_{0.5}Co_{0.5}Fe_{11}O_{19}$ composition. The ferrite powders were prepared by conventional ceramic processing technique and used as absorbent fillers in ferrite-rubber composites. The magnetic properties were measured by vibrating sample magnetometer. The complex permeability and dielectric constant were measured by using the WR-28 rectangular waveguide and network analyzer in the frequency range 26.5~40 GHz. For the Ti-Co substituted M-hexaferrites, the ferromagnetic resonance is observed at Ka-band (29.4 GHz). The matching frequency and matching thickness are determined by using the solution map of impedance matching. A wide band microwave absorbance is predicted with controlled ferrite volume fraction and absorber thickness.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.581-584
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• 2002

In this work, a CPW resonator was designed and fabricated to investigate the basic microwave properties, such as effective dielectric constant, of BST thin films. Their properties were used as basic data to simulate and design CPW tunable bandpass filter. We also report on gold/$Ba_{0.5}Sr_{0.5}TiO_3$(BST) ferroelectric thin film C-band tunable bandpass filters(BPFs) designed and fabricated on magnesium oxide substrates using CPW structure. The 2 pole filter was designed for a center frequency of 5.88 GHz with a bandwidth of 9 %. The BST based CPW filter offers a high sensitivity parameter as well as a low loss parameter. The tuning range for the bandpass filter with CPW structure was determined to be 170 MHz.

• Journal of the Korean Magnetics Society
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• v.5 no.1
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• pp.21-26
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• 1995

The systematic variation of complex permeability and complex permittivity and their relationship with micro-wave absorbing properties are investigated in sintered Ni-Zn ferrites of non-stoichiometric composition. The specirrens of ${(Ni_{0.5}Zn_{0.5}O)}_{1-x}(Fe_{2}O_{3})_{1+x}$ spinels were prepared by a conventional ceramic processing technique. In the present study. complex permeability and permittivity can be controlled by the variation of ${\alpha}-Fe_{2}O_{3}$ contents in the spinel lattice. The primary effect of the excess ${\alpha}-Fe_{2}O_{3}$ is to increase the dielectric constant. while the notable decrease of magnetic loss is observed in the iron-deficient ferrites. The results suggest that the matching fre-queocyand matching thickness could be controlled by the variation of ${\alpha}-Fe_{2}O_{3}$ contents in the Ni-Zn ferrite.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.11
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• pp.77-82
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• 1990

The temperature and the composition dependence of the dielectric properties of the solid solution materials in the system $xBa(Zn_{1/3}Nb_{2/3})O_{3}\[BZN]-(1-x)\Sr(Zn_{1/3}Nb{2/3)O_{3}\[SZN]$ at microwave frequency was studied. The dielectric constant and unloaded Q were $40.5{\pm}0.5,5980{\pm}100$ respectively for BZN at 10 GHz and $36.9{\pm}0.5,2700{\pm}100$ for SZN at 10.2GHz. The temperature coefficient of the resonant frequency was $+27.5ppm/{\circ}C$ for BZN and $-39.1ppm/{\circ}C$ for SZN. The results also showed that 0.3 BZN-0.7 SZN is the most temperature-stable composition among xBZN-(1-x) SZN solid solutions. In this case, the dielectric constant, the unloaded Q and $\tau_{f}$ at 9.8GHz were $41.5{\pm}0.2,2920{\pm}100$ and $-3.5ppm/{\circ}C$, respectively.