• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1456-1458
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• 1998

The $(Sr_{1-x}Ca_x)TiO_3(SCT)$ thin films were deposited at various substrate temperature using rf magnetron sputtering method on optimized Pt-coated electrodes ($Pt/TiN/SiO_2/Si$). The dielectric constant changes almost linearly in the temperature region of $-80{\sim}+90[^{\circ}C]$, the temperature characteristics of the dielectric loss exhibited a stable value within 0.1. The capacitance characteristics appears a stable value within ${\pm}5$[%]. The drastic decrease of dielectric constant and increase of dielectric loss in SCT thin films is observed above 200[kHz]. Dielectric constant of SCT thin films deposited on Si wafer substrate are larger with the increase of deposition temperature.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.10
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• pp.1800-1808
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• 2003

This work deals with the electrical conductivity of dielectric on output parameters such as metal removal rate and surface roughness value of a carbon steel(SM25C) and sintered carbides cut by wire-electrical discharge machining(W-EDM). Dielectric has several functions like insulation, ionization, cooling, the removal of waste metal particles. The presence of minute particles(gap debris) in spark gap contaminates and lowers the breakdown strength of dielectric. And it is considered that too much debris in spark gap is generally believed to be the cause of arcing. Experimental results show that increases of cobalt amount in carbides affects the metal removal rate and worsens the surface quality as a greater quantity of solidified metal deposits on the eroded surface. Lower electrical conductivity of the dielectric results in a lower metal removal rate because the gap between wire electrode and workpiece reduced. Especially, the surface characteristics of rough-cut workpiece and wire electrode were analyzed too. Debris were analyzed also through scanning electron microscopy(SEM) and surface roughness tester. Micro cracks and some of electrode material are found on the workpiece surface by energy dispersive spectrometer(EDS).

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1615-1617
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• 1996

In this study, epoxidized bisphenolic resins laminated with glass fiber mat(GFRP) are ivestigated on surface, bulk aspect and dielectric constant(${\varepsilon}'$ and ${\varepsilon}''$) vs. frequency characteristics with temperature. The investigation shows the different characteristics accordig to the attachments of fiber surface, filler content, matrix properties, and the others. Especially, dielectric properties of this sample are highly increased above $100^{\circ}C$ and decreased with the rise of frequency. There is a resonance at the high frequency region ($1MHz{\sim}10MHz$). So, dielectric properties show the shift with frequency and temperature. Dielectric properties of EGL 10 are higher than those of EGL 40 with the frequency. Generally, dielectric properties of EGL 10 are more unstable than those of EGL 40 on the shift of frequency and temperature.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.6
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• pp.15-21
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• 2006

This work deals with the electrical conductivity of dielectric on output parameters such as metal removal rate and surface roughness value of a carbon steel(SM25C) and sintered carbides cut by wire electrical discharge machining (WEDM). Dielectric has several functions like insulation, ionization, cooling, the removal of waste metal particles. The presence of minute metal particles(debris) in spark gap contaminates and lowers the breakdown strength of dielectric. And it is considered that too much debris in spark gap is generally believed to be the cause of arcing. Experimental results show that increases of cobalt amount in carbides affects the metal removal rate and worsens the surface quality as a greater quantity of solidified metal deposits on the eroded surface. Lower electrical conductivity of the dielectric results in a lower metal removal rate because the gap between wire electrode and workpiece reduced. Especially, the surface characteristics of rough-cut workpiece and wire electrode were analyzed too. Debris were analyzed also through scanning electron microscopy(SEM) and surface roughness tester. Micro cracks and some of electrode material are found on the workpiece surface by energy dispersive spectrometer(EDS).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.293-294
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• 2005

We have investigated dielectric properties depending on frequency in organic light -emitting diodes using 8-hydroxyquinoline aluminum ($Alq_3$) as an electron transport and emissive material. We analyzed the dielectric properties of organic light-emitting diodes using impedance of characteristics. impedance characteristics was measured complex impedance Z and phase $\Theta$ in the frequency range of 40 Hz to $10^8$ Hz. We obtained complex electrical conductivity, dielectric constant, and loss tangent (tan$\delta$) of the device at room temperature. From these analyses, we are able to interpret a conduction mechanism and dielectric properties contributed by an interfacial and orientational polarization.

• Electrical & Electronic Materials
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• v.7 no.5
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• pp.403-408
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• 1994

Dielectric and structural properties of $Ba_{1-x}$(Z $n_{1}$3/T $a_{2}$3/) $O_{3}$+1 mol% Mn $O_{2}$ (x=0, 0.01, 0.02, 0.03, 0.04) ceramics was investigated at microwave frequencies. With $Ba_{+2}$ shortage, the sinterability and the unloaded Q( $Q_{u}$) were much improved, and the ordering in B site and the lattice distortion was greatly enhanced and the structure approached the completely ordered structure. $Q_{u}$ was strongly correlated with these factors such as ordering ratio, lattice distortion and sinterability, and had the maximum value of 7500 at x=0.01. The dielectric constant was near 30 and the temperature coefficient of the resonant frequency was 2 ppm/.deg. C at x=0.01.1.1.1.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.04a
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• pp.74-75
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• 2006

We have investigated dielectric properties depending on temperature in organic light-emitting diodes using 8-hydroxyquinoline aluminum ($Alq_3$) as an electron transport and emissive material. We analyzed the dielectric properties of organic light-emitting diodes using characteristics of impedance. he Impedance characteristics was measured complex impedance Z and phase $\theta$ in the temperature range of 10 K to 300 K. We obtained complex electrical conductivity, dielectric constant and loss tangent ($tan{\delta}$) of the device at room temperature. From these analyses, we are able to interpret a conduction mechanism and dielectric properties contributed by an interfacial and orientational polarization.

• Journal of the Korean Ceramic Society
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• v.50 no.1
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• pp.87-91
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• 2013

The doping effect of Sn on the microstructure evolution and dielectric properties was studied in $CaCu_3Ti_{4-x}Sn_xO_{12}$ polycrystals. Samples were produced by a conventional solid-state reaction method. Sintering was carried out at $1115^{\circ}C$ for 2-16 h in air. The dielectric constant and loss were examined at room temperature over a frequency range between $10^2$ and $10^6$ Hz. The microstructure was found to evolve into three stages. Addition of $SnO_2$ led to an increase in density and advanced formation of abnormal grains. The formation of coarse grains with a reduced thickness of the boundary brought about an enhanced dielectric constant and a lower dielectric loss below ~1 kHz. EDS data showed the Cu-rich phase along the grain boundary, which should contribute to the improved dielectric constant according to the internal barrier layer capacitor model. After all, $SnO_2$ was an effective dopant to elevate the dielectric characteristics of $CaCu_3Ti_{4-x}Sn_xO_{12}$ polycrystals as a promoter for abnormal grain growth.

• Journal of Korean Vacuum Science & Technology
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• v.3 no.2
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• pp.130-133
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• 1999

Paraelectric ZrTiO4 thin films were synthesized on a Si(100) substrate using DC magnetron reactive sputtering. Films deposited above-400$^{\circ}C$ exhibited crystalline characteristics. The dielectric constants ($\varepsilon$) and dielectric losses (tan$\delta$) of as-deposited and annealed films were measured in the 1 MHz range using a Pt upper electrode and a phosphorous-doped si bottom electrode. Preliminary data showed that as the deposition temperature increased, the dielectric losses decreased while the dielectric constants did not change significantly. similar trends for dielectric losses were observed when the as-deposited samples were annealed at 800$^{\circ}C$. The reduction of dielectric losses at high-deposition temperatures and post annealing correlated well with the x-ray diffraction peak widths.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.22-28
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• 2000

The fiber reinforced composite materials is widely used in aircraft, space structures and robot arms because of high specific strength and high specific modulus. The on-line cure monitoring during the cure process of the composite materials has become an important research area for the better quality and productivity. In this paper, the dielectric circuit of the wheatstone bridge type for measuring the dissipation factor was designed and manufactured. Also, the dielectric sensor for the cure monitoring of the high temperature composites was developed. The residual thermal stresses of the dielectric sensor were analyzed by the finite element method and its dielectric characteristics under high temperature were evaluated. The on-line cure monitoring of the BMI resin was performed using the wheatstone bridge type circuit and developed high-temperature dielectric sensor.