• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.21 no.6
• /
• pp.538-543
• /
• 2008

Nanostructured materials are attracting increased interest and application. Exciting perspectives may be offered by electrical insulation. Epoxy/Organoclay nanocomposites may find new and upgraded applications in the electrical industry, replacing conventional insulation to provide improved performances in electric power apparatus, e.g, high voltage motor/generator stator winding insulation, dry mold transformer, etc. In the paper work, the electrical and thermal properties of epoxy/organoclay nanocomposites materials were studied. The electrical insulation characteristics were analyzed through the permittivity characteristics. by analyzing the permittivity spectra, it was found that dielectric constant becomes smaller with increase frequency and becomes larger with increase temperature. This indicates restriction of molecular motion and strong bonds at the epoxy/organoclay nanocomposites. The morphology of nanocomposites obtained was examined using TEM and X-ray diffraction. It has been shown that the presence of polar groups leads to an increased gallery distance and partial exfoliation. Nevertheless, full exfoliation of clay platelets has not been achieved.

• Journal of Powder Materials
• /
• v.25 no.6
• /
• pp.494-500
• /
• 2018

In this study, the effect of the content of $MgO-CaO-Al_2O_3-SiO_2$ (MCAS) glass additives on the properties of AlN ceramics is investigated. Dilatometric analysis and isothermal sintering for AlN compacts with MCAS contents varying between 5 and 20 wt% are carried out at temperatures ranging up to $1600^{\circ}C$. The results showed that the shrinkage of the AlN specimens increases with increasing MCAS content, and that full densification can be obtained irrespective of the MCAS content. Moreover, properties of the AlN-MCAS specimens such as microhardness, thermal conductivity, dielectric constant, and dielectric loss are analyzed. Microhardness and thermal conductivity decrease with increasing MCAS content. An acceptable candidate for AlN application is obtained: an AlN-MCAS composite with a thermal conductivity over $70W/m{\cdot}K$ and a dielectric loss tangent (tan ${\delta}$) below $0.6{\times}10^{-3}$, with up to 10 wt% MCAS content.

• Proceedings of the KIEE Conference
• /
• 2001.07c
• /
• pp.1387-1389
• /
• 2001

In this paper, the microstructure and the dielectric properties of the $Sr_{1-x}Ca_xTiO_3$($0{\leq}x{\leq}0.2$)-based grain boundary layer ceramics were investigated. The 2nd phase formed by thermal diffusing from the surface lead to a very high apparent dielectric constant, ${\varepsilon}_r$ > 50000, and tan$\delta$ < 0.05, $\Delta$C < ${\pm}$ 10%.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.22 no.1
• /
• pp.53-60
• /
• 2009

$ZrTiO_4$ dielectric thin films were coated by metal-organic decomposition, and annealed by rapid thermal processing up to $900^{\circ}C$ for their crytallization. Crystallized single-phase $ZrTiO_4$ thin films were fabricated above the annealing temperature of $800^{\circ}C$, but their grains were randomly oriented without specific textured orientation. Best dielectric properties were presented by the sample annealed at $800^{\circ}C$ which had crystalline structure and flat surface. Dielectric constant of the film was maintained at 32 throughout full frequency range up to 6 GHz, and dielectric loss was varied between 0.01 and 0.04.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.22 no.4
• /
• pp.290-296
• /
• 2009

$Bi_{4}Ti_{3}O_{12}$ (BiT) thin films were grown on the Pt/Ti/$SiO_2$/si substrate using a metal organic decomposition (MOD) method. Effects of oxygen annealing on the structural properties and dielectric properties of the BiT thin films were investigated. The BiT films were well developed when rapid thermal annealed at $>500^{\circ}C$ in oxygen ambient. For the film annealed at $700^{\circ}C$, no crystalline phase was observed under oxygen free annealing atmosphere while its crystallinity was significantly enhanced as the oxygen pressure increased. The BiT film also exhibited a smooth surface with defect free grains. A high dielectric constant and a low dielectric loss were achieved satisfactory in the frequency range from 75 kHz to 1 MHz. Especially, the BiT film, annealed at $700^{\circ}C$ and 10 torr oxygen pressure, showed good dielectric properties: dielectric constant of 51 and dielectric loss of 0.2 % at 100 kHz. Its leakage current was also considerably improved, being as $0.62\;nA/cm^2$ at 1 V. Therefore, it is considered that the oxygen annealing has effects on an enhancement of crystallinity and dielectric properties of the BiT films.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.05c
• /
• pp.53-57
• /
• 2002

Reduction of insulation thickness would be beneficial not only for increasing the cable length but would also improve its thermal performance. An interfacial diffusion method was devised to reduce insulation thickness by improving the interfacial properties of XLPE cable insulation. In this paper, to evaluate superficially the interface properties between XLPE insulation and semiconducting layer, the dielectric and insulation properties of tan${\delta}$ and volume resistance were measured with temperature dependence. Above the results, dielectirc and insulation properties with semiconductor/XLPE were more anormal than its bulk caused by the interfacial properties.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.05b
• /
• pp.29-32
• /
• 2005

Poly (methyl methacrylate) (PMMA) is one of the promising representive of polymer gate dielectric for its high resistivity and sutible dielectric constant. PMMA (Mw=96700) films were prepared on p-Si by spin coating method. PMMA were coated compactively and flatly as observeed by AFM. MIS(Al/PMMA/p-Si) structure was made and capacitance-voltage (C-V) and current-voltage (I-V) measurements were done with PMMA films for different thermal treatment temperature. PMMA films were showed proper dielectric constant and breakdown voltage. Above the glass transition temperature PMMA films degraded. C-V measured at various frequencies, dielectric constant increased a little. The absence of hysteresis in the C-V characteristics, which eliminate the possibility of mobile charges in the PMMA films. The observed thermal stability, smooth surfaces, dielectric constant, I-V behavior implies PMMA formed by spin coating can be used as an efficient gate dielectric layer in OTFTs.

• Journal of the Korean Ceramic Society
• /
• v.50 no.1
• /
• pp.70-74
• /
• 2013

Dependence of microwave dielectric properties on the crystallization behaviors of $CaMgSi_2O_6$ (diopside) glass-ceramics was investigated with different heat treatment methods (one and/or two-step). The crystallization behaviors of the specimens, crystallite size and degree of crystallization, were evaluated by differential thermal analysis (DTA), scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis by combined Rietveld and reference intensity ratio (RIR) methods. With an increase in heattreatment temperature, the dielectric constant (K) and the quality factor (Qf) increased due to the increase of the crystallite size and degree of crystallization. The specimens heat-treated by the two-step method had a higher degree of crystallization than the specimens heat-treated by the one-step method, which induced improvement in the quality factor (Qf) of the specimens.

• Journal of Radiation Industry
• /
• v.4 no.3
• /
• pp.285-288
• /
• 2010

Polyimide films have excellent thermal stability, reliable mechanical properties and low dielectric constant. Therefore, this material is widely used in many industrial fields such as microelectronics, flexible circuits, semiconductor products and aerospace materials. In space applications, earth-orbiting hardware operates in environments that generally include neutral particles, charged particles such as trapped protons and electrons, solar protons, and cosmic rays. Under these conditions, polyimide films were changed in the optical, electrical and mechanical properties. Therefore, in this study, we evaluated the effects of electron beam irradiation on polyimide. The O-H functional groups were created on the polyimide film surface in the results of FT-IR spectra. And it was found that the dielectric constants were changed as a function of electron beam dose.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.26 no.12
• /
• pp.867-871
• /
• 2013

The Ti adhesion layers were deposited onto the glass substrate for transparent capacitors using $Bi_2Mg_{2/3}Nb_{4/3}O_7$ (BMNO) dielectric thin films. Graphene was transferred onto the Ti/glass substrate after growing onto the Ni/$SiO_2$/Si using rapid-thermal pulse CVD (RTPCVD). The BMNO dielectric thin films were investigated for the microstructure, dielectric and leakage properties in the case of capacitors with and without Ti adhesion layers. Leakage current and dielectric properties were strongly dependent on the Ti adhesion layers grown for graphene bottom electrode.