• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.1
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• pp.94-103
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• 2005

The low foamed high strengthen styrofoam samples made by dielectric heating are discussed. We used the oscillator which have the frequency of 13.6 MHz and the power of 7 kW. 3 times expanded beads by steaming method were used in our foam-molding test. Internal fusion properties and density of internal structure were improved by dielectric foaming process. At the temperature of $105-110^{\circ}C$, the internal fusion property was maximally improved.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.413-416
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• 1996

The ceramic dielectrics were fabricated by mixing of Mn $O_2$ and ZnO at (B $a_{0.85}$ $Ca_{0.15}$)Ti $O_3$ and studied for dielectric relaxation characteristics. The dielectric relaxation time was increased by space charge polarization of palaelectric layer at the low temperature and frequency but it was decreased by Interface polarization at the high temperature and frequency. The remnant polarization and coercive field of ceramic dielectrics was decreased by rising temperature.ure.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1357-1359
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• 1994

In this study, in order to improve the problem that dielectric breakdown strength decrease remarkably at high temperature, simultaneous interpenetrating polymer networks method was Introduced so that epoxy insulating material could have stable temperature characteristics and stable dielectric breakdown characteristics at whole temperature range. So network structure of epoxy/$SiO_2$ composite material was changed by adding MA and MA/PU into epoxy resin. DC voltage is applied into the specimen fabricated by this method, and then the result was compared and investigated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.229-233
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• 2000

In this study, the temperature coefficient of resonant frequency($TCF_r$), dielectric and piezoelectric properties of $Pb_{1-x}Sr_x[(Sb_{1/2}Nb_{1/2})_{0.035}(Mn_{1/3}Nb_{2/3})_{0.065}(Zr_{0.49},Ti_{0.51})_{0.90}]O_3$ ceramics were investigated with the Sr substitution to Pb site. The dielectric constant was increased according to the increase of Sr substitution and electromechanical coupling factor($k_t$) also showed the highest values of 0.485 when the Sr substitution was 5 mol%. Moreover, the mechanical quality factor($Q_{mt}$) showed the highest value of 233 when the Sr substitution was 2 mol%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.9-12
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• 2000

Insulators for high-voltage and large-power should be endured mechanically the weight of mold bushing itself and the force of pushed from contact with circuit breaker and conductor. But dielectric breakdown could be occurred result from the external circumstances and internal factors such as chemical reaction, partial discharge, change of temperature and the relation of temperature-time in process of casting. Therefore, to get rid of external and internal factors of dielectric breakdown. Furthermore, to prevent the internal cracks, void, cavity which resulted from the contraction originated on the interface between copper and epoxy resin, formed semi-conductive layer with partially carbon painted on copper bar. The PD properties and the insulation qualities of epoxy molded insulators were improved by roles of cushions for the direction of diameter and natural sliding effects as like separated from conductor for the direction of length.

• Journal of Ceramic Processing Research
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• v.13 no.spc2
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• pp.163-165
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• 2012

Impedance spectroscopy informs electrical properties of materials as accumulated charges, contact status between electrode and organic materials. We carried out impedance spectroscopy of organic light-emitting diodes as ITO/Alq3(60 nm)/Al on temperatures from 10 K to 300 K. The result described Z'-Z" plot, cole-cole plot and dielectric relaxation time τ. Z'-Z" plot means that real and imaginary part of materials in organic and electrode by frequencies and temperature. Z' as real part of impedance by applied frequency depending on temperature shows the plateau in low frequency region as Rs+ Rp and over 100 kHz in high frequency region as Rs. Cole-cole plot shows resistance of materials in equivalent circuit of the device by temperatures. And equivalent circuit and dielectric relaxation could be accomplished by using the complex impedance analysis.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.37-37
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• 2010

Silicate-silsesquioxane or siloxane-silsesquioxane hybrid thin films are strong candidates as matrix materials for ultra low dielectric constant (low-k) thin films. We synthesized the silicate-silsesquioxane hybrid resins from tetraethoxyorthosilicate (TEOS) and methyltrimethoxysilane (MTMS) through hydrolysis and condensation polymerization by changing their molar ratios ([TEOS]:[MTMS] = 7:3, 5:5, and 3:7), spin-coating on Si(100) wafers. In the case of [TEOS]:[MTMS] 7:3, the dielectric permittivity value of the resultant thin film was measured at 4.30, exceeding that of the thermal oxide (3.9). This high value was thought to be due to Si-OH groups inside the film and more extensive studies were performed in terms of electronic, ionic, and orientational polarizations using Debye equation. The relationship between the mechanical properties and the synthetic conditions of the silicate-silsesquioxane precursors was also investigated. The synthetic conditions of the low-k films have to be chosen to meet both the low orientational polarization and high mechanical properties requirements. In addition, we have investigated a new solution-based approach to the synthesis of semiconducting chalcogenide films for use in thin-film transistor (TFT) devices, in an attempt to develop a simple and robust solution process for the synthesis of inorganic semiconductors. Our material design strategy is to use a sol-gel reaction to carry out the deposition of a spin-coated CdS film, which can then be converted to a xerogel material. These devices were found to exhibit n-channel TFT characteristics with an excellent field-effect mobility (a saturation mobility of ${\sim}\;48\;cm^2V^{-1}s^{-1}$) and low voltage operation (< 5 V). These results show that these semiconducting thin film materials can be used in low-cost and high-performance printable electronics.

• Advances in materials Research
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• v.2 no.3
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• pp.141-153
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• 2013

Nanocrystalline Barium niobate ($BaNbO_3$) has been synthesized by a novel auto-igniting combustion technique. The X-Ray diffraction studies reveals that $BaNbO_3$ posses a cubic structure with lattice constant $a=4.071{\AA}$. Phase purity and structure of the nano powder are further examined using Fourier-Transform Infrared and Raman spectroscopy. The average particle size of the as prepared nano particles from the Transmission Electron Microscopy is 20 nm. The UV-Vis absorption spectra of the samples are recorded and the calculated average optical band gap is 3.74eV. The sample is sintered at an optimized temperature of $1425^{\circ}C$ for 2h and attained nearly 98% of the theoretical density. The morphology of the sintered pellet is studied with Scanning Electron Microscopy. The dielectric constant and loss factor of a well-sintered $BaNbO_3$ at 5MHz sample is found to be 32.92 and $8.09{\times}10^{-4}$ respectively, at room temperature. The temperature coefficient of dielectric constant was $-179pp/^{\circ}C$. The high dielectric constant, low loss and negative temperature coefficient of dielectric constant makes it a potential candidate for temperature sensitive dielectric applications.

• Proceedings of the Materials Research Society of Korea Conference
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• 2008.11a
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• pp.22.2-22.2
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• 2008

• Proceedings of the Materials Research Society of Korea Conference
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• 2007.11a
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• pp.54.1-54.1
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• 2007