• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.2
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• pp.144-150
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• 2008

Recently, there has been growing interest in low loss and low dielectric constant material for LTCC application, as the frequency range for electronic devices increases. This study was designed to evaluate the effect of cordierite filler for low dielectric constant LTCC material. From the previous experiments, two glass compositions of B-Si-Al-Zn-Ba-Ca-O and B-Si-Al-Sr-Ca-O system, were chosen. Each powder of two glass compositions was sintered respectively with commercial cordierite powder in temperature range from $800^{\circ}C\;to\;900^{\circ}C$. Crystalline cordierite and glass peaks were affected only with two factors of composition and sintering temperature among various factors. With the optimized condition of two cordierite/glass compositions, obtained dielectric constant was below 5.5 and quality factor was above 1,000. Closed pore of sintered body was controled by sintering temperature and sintering time. When cordierite/glass composite with ratio of 5.5:4.5 was sintered at $900^{\circ}C$, densification was sufficient with good dielectric characteristics of ${\epsilon}_r<5.1,\;Q{\ge}1,000$. Residual fine closed pores could be reduced with control of sintering temperature and time. 3 point bending strength and chemical durability were evaluated to obtain feasibility for substrate material.

• 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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• 2005.07a
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• pp.518-519
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• 2005

We have studied the transmittance of fringe-filed switching(FFS) using a liquid crystal with positive dielectric anisotropy. Generally, FFS having positive dielectric anisotropy has less transmittance than FFS using negative dielectric anisotropy. FFS mode transmittance depends on horizontal director deformation, however fringe filed is composed of vertical and horizontal field. Vertical field in the middle of electrode suppresses the transmittance of FFS mode, especially when we use positive one. So, it is important to prevent the LC director from the effect of vertical field. We changed the splay elastic constant and checked the transmittance. The transmittance of FFS having positive dielectric anisotropy was improved. Less tilted LC directors improve the transmittance of FFS using positive dielectric anisotropy. We can improve the transmittance by using LC which have high splay elastic constant when another LC properties are equal.

• Journal of the Korean Chemical Society
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• v.56 no.1
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• pp.20-27
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• 2012

Complex permittivity spectra of Allyl Chloride (AC), 2-Butanone (2-BU) and their binary mixtures over the entire range of concentration were obtained using the Time Domain Reflectometry (TDR) technique in microwave frequency range at various temperatures. Static dielectric constant and relaxation time are obtained from complex permittivity spectra. Density ($\rho$) and refractive index ($n_D$) are also measured. These parameters are used to determine excess dielectric constant, excess inverse relaxation time, excess molar volume, excess molar refraction, polarity, Bruggeman factor and thermodynamic parameters viz. enthalpy of activation and entropy of activation. The values of static dielectric constant and relaxation time increases while density and refractive index decreases with the percentage of 2-Butanone in Allyl Chloride increases. Excess parameters were fitted to a Redlich-Kister equation.

• Journal of the Korean Ceramic Society
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• v.28 no.4
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• pp.329-337
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• 1991

The Ni-MgO composites were prepared by coprecipitation of NiO-MgO solid solutions and their selective reduction in a hydrogen atmosphere. We report on the measurements of both ac conductivity $\sigma$ ($\omega$, f) and dielectric constant $textsc{k}$'($\omega$, f) for the Ni-MgO composites in the frequency range from 10 Hz to 10 MHz at room temperature. The frequency exponents of conductivity and dielectric constant, x and y, are found to be x=0.98$\pm$0.05 and y=0.05$\pm$0.01. These results are in good agreement with a general scaling relation $\chi$-y=1, although these values are different from the theoretical predications. The dielectric constant exponent ($textsc{k}$' f-fc -s) is found to be s=0.62$\pm$0.07 with estimated percolation threshold fc=0.20$\pm$0.02.

• Journal of the Korean Ceramic Society
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• v.30 no.2
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• pp.93-100
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• 1993

The effects of MgO addition on thermal expansiion coefficient and dielectric constant of mullite were studied. Thermal coefficient and dielectric constant decrease with increasing MgO content and exhibit a minimum value at 1wt% MgO. However, above 3wt% MgO content both values increase. Result of X-ray diffraction analysis how that mullite compositions which include more than 0.1wt% MgO form cordierite. Spinel is also formed as well as cordierite in the composition containing more than 3wt% MgO. The results indicate that addition of MgO affect the thermal expansion coefficient and dielectric constant of mullite substrate because of the formation of new phases; cordierite and spinel. The thermal expansion coefficient and dielectric constant are affected mainly by cordierite and spinel in the regions containing less than more than 3wt% MgO, respectively.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.1
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• pp.22-24
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• 2012

Depending on the status of the engine oil, the dielectric constant is changed. Dielectric constant of oil is related to the characteristic impedance of the probe and the characteristic impedance of the probe determines the reflected signal. In this paper, we derive an equivalent circuit of the probe and using the dielectric constant obtained by measuring the capacitance, the theoretical reflection coefficient of the probe was calculated. In the results, if the engine oil is deteriorated, we can see that the reflection coefficient is increased.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.267-270
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• 1999

We measured the dielectr~c constant of undoped GaN thin films grown on (0001) sapphire substrates In 0.8 - 4.5 eV energy (276 - 1550 nm wavelength) range by spectroscopic ellipsometry. For more accurate data analysis we also performed X-ray diffraction, photolurninescence and Rutherford backscattering spectroscopy on samples. Data were analyzed with a four-phase model. The dielectric constant of GaN thin films was obtained not only in the transparent region but also around the absorption edge. Absorption edge energy, $3.3992{\pm}0.002$eV was determined from the obtained dielectric function.

• Journal of Sensor Science and Technology
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• v.20 no.4
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• pp.243-248
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• 2011

The purpose of this study is to develop a sensing system to measure the capacitance of a pre-developed engine oil deterioration detection sensor integrated with an oil filter. To measure the capacitance of engine oil in the sensor, it is used the way measuring the electric charging time in a capacitor by impressing DC volt. This method has merits on cost and signal stability. The measured capacitance is compensated by comparison with the one measured by an impedance analyzer. Also, using the dielectric constant gained by an impedance analyzer, the calculating equation of the dielectric constant of engine oil related with the currently developed sensor is decided. Finally, the degradation degree of engine oil is estimated according to the change rate of dielectric constant between green oil and used oil. The newly developed personal controller is to control a series of the processes.

• Transactions on Electrical and Electronic Materials
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• v.10 no.2
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• pp.49-52
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• 2009

Barium strontium calcium titanate powders were prepared with the sol-gel method. Ferroelectric $(Ba_{0.54}Sr_{0.36}Ca_{0.1})TiO_3$(BSCT) thick films were fabricated by the screen-printing method on alumina substrate. Then we investigated the structural and dielectric properties of the BSCT thick films at different sintering temperatures. The thermal analysis showed that the BSCT polycrystalline perovskite phase formed at around $660^{\circ}C$. The X-ray diffraction analysis showed a cubic perovskite structure with no second phase present in all of the BSCT thick films. The average grain size and the thickness of the specimens sintered at $1450^{\circ}C$ were about $1.6{\mu}m$ and $45{\mu}m$, respectively. The relative dielectric constant increased and the dielectric loss decreased as the sintering temperature was increased; for BSCT thick films sintered at $1450^{\circ}C$ the values of the dielectric constant and the dielectric loss were 5641 and 0.4%, respectively, at 1 kHz.