• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.1371-1373
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• 2000

In this paper, the complex accelerating degradation of traction motor driven with VVVF controlled inverter were performed on the form coil samples with the 200 Class insulation system. in order to evaluate the reliability and the long-term life. After aging, the dielectric and PD properties were investigated on the 10 cycles aging sample in the range of $20{\sim}160[^{\circ}C]$ and AC $250{\sim}2250[V]$ to diagnosis the condition of end-life and find the dominative factors of degradation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.238-241
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• 2000

In this paper, we manufactured Pb($Ni_{1/2}$ $W_{1/2}$)$O_3$-Pb($Mn_{1/3}$$Nb_{2/3}$)$O_3$-Pb($Zr_3$Ti)$O_3$ceramics with variation of milling time and investigated its dielectric and piezoelectric properties. Density was increased with the increase of milling time because the sinterability of specimens were improved with the decrease of particle size. The highest value of electromechanical coupling factor was 0.518 at milling time 5hour. The highest values of mechanical quality factor and dielectric constant were 1566, 1590 at milling time 4hour, respectively.

• Proceedings of the KIEE Conference
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• 1993.07a
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• pp.12-15
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• 1993

The correlation between electrical conduction and dielectric relaxation properties of copper ion conducting glasses is discussed. The glasses were prepared in the system $CuI-Cu_2S-Cu_2O-MoO_3$ using rapid quenching technique. These glasses have high ionic conductivities at room temperature in the range of $10^{\circ}$[S/m], and the conductivities increase with increasing CuI content. The activation energies for conduction are 0.26 - 0.57 eV. The dielectric relaxation times are 1 - 10uS, and the activation energy for ion jumping are 0.18 - 0.41eV. It is shown that the tendency of conduction properties depending on composition of the glass is similar those of dilectric relaxation.

• Applied Microscopy
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• v.46 no.4
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• pp.227-237
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• 2016

This investigation deals with the process of field electron emission from composite microemitters. Tested emitters consisted of a tungsten or carbon-fiber core, coated with a dielectric material. Two coating materials were used: (1) Clark Electromedical Instruments Epoxylite resin and (2) Epidian 6 Epoxy resin (based on bisphenol A). Various properties of these emitters were measured, including the current-voltage characteristics, which are presented as Fowler-Nordheim plots, and the corresponding electron emission images. A field electron microscope with a tip (cathode) to screen (anode) distance of 10 mm was used to electrically characterize the emitters. Measurements were carried out under ultra-high vacuum conditions with a base pressure of $10^{-6}$ Pascal ($10^{-8}$ mbar).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.213-214
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• 2007

에폭시/마이카는 높은 절연성과 강도, 열 안정성 등으로 인하여 고전압 회전기 고정자 권선의 절연재료로 사용되고 있다. 그러나 최근 청단기기의 등장과 냉난방 부하의 증가로 첨두 부하가 크게 증가하여 발전기 부하변동과 자동 정지횟수가 빈번해지고 있다. 이에 따라 기존에 사용되고 있는 절연재료를 획기적으로 발전시킨 새로운 소재의 개발이 필요하게 되었다. 최근 나노기술은 이러한 기술적 한계를 극복할 수 있는 좋은 대안으로 떠오르고 있다. 그리고 나노 크기의 층상화합물은 기존의 재료에 비해 월등한 전기적, 기계적, 열적 특성을 지닌 것으로 알려져 있다. 본 논문에서는 에폭시 기지에 층상 마이카와 점토를 혼합한 나노복합재료를 제조하여 주파수별, 온도별 유전특성을 살펴보았다.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.546-549
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• 1993

The correlation between electrical conduct ion and dielectric relaxation properties of copper ion conducting glasses is discussed. The glasses were prepared in the system $CuI-Cu_2S-Cu_2O-MoO_3$ using rapid quenching technique. These glasses have high ionic conductivities at room temperature in the range of $10^{circ}$[S/m], and the conductivities increase with increasing CuI content. The activation energies for conduction are 0.26-0.57 eV. The dielectric relaxation times are 1-10uS, and the activation energy for ion jumping are 0.18-0.41eV. It is shown that the tendency of conduction properties depending on composition of the glass is similar those of dilectric relaxation.

• Korean Journal of Materials Research
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• v.20 no.7
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• pp.374-378
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• 2010

$MgTiO_3$ thin films were prepared by r.f. magnetron sputtering in order to prepare miniaturized NPO type MLCCs. $MgTiO_3$ films showed a polycrystalline structure of ilmenite characterized by the appearance of (110) and (202) peaks. The intensity of the peaks decreased with an increase in the chamber pressure due to the decrease of crystallinity which resulted from the decrease of kinetic energy of the sputtered atoms. The films annealed at $600^{\circ}C$ for 60min. showed a fine grained microstructure without micro-cracks. The grain size and roughness of the $MgTiO_3$ films decreased with the increase of chamber pressure. The average surface roughness was 1.425~0.313 nm for $MgTiO_3$ films prepared at 10~70 mTorr. $MgTiO_3$ films showed a dielectric constant of 17~19.7 and a dissipation factor of 2.1~4.9% at 1MHz. The dielectric constant of the films is similar to that of bulk ceramics. The dielectric constant and the dissipation factor decreased with the increase of the chamber pressure due to the decrease of grain size and crystallinity. The leakage current density was $10^{-5}\sim10^{-7}A/cm^2$ at 200kV/cm and this value decreased with the increase of the chamber pressure. The small grain size and smooth surface microstructure of the films deposited at high chamber pressure resulted in a low leakage current density. $MgTiO_3$ films showed a near zero temperature coefficient and satisfied the specifications for NPO type materials. The dielectric properties of the $MgTiO_3$ thin films prepared by sputtering suggest the feasibility of their application for MLCCs.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.298-298
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• 2007

Influence of $TiO_2$ on the dielectric properties of the $Bi(Nb_{0.7}Ta_{0.3})O_4$ ceramic with 7 wt% zinc borosilicate(ZBS) glass was investigated as a function of the $TiO_2$ contents with a view to applying this system to LTCC technology. The $Bi(Nb_{0.7}Ta_{0.3})O_4$ ceramic addition of 7 wt% ZBS glass ensured successful sintering below $900^{\circ}C$. But, TCF of $Bi(Nb_{0.7}Ta_{0.3})O_4$ ceramic is large negative values, respectively, it is necessary to adjust to zero TCF for practical applications Therefore, the addition of materials having positive TCF, such as $TiO_2$, might be an effective method for the improvement. In general, increasing addition of $TiO_2$ increased dielectric constant and TCF but it decreased the sinterability and $Q{\tiems}f$ value significantly due to the dielectric property and high sintering temperature of $TiO_2$. $Bi(Nb_{0.7}Ta_{0.3})O_4$ ceramic with 7 wt% ZBS glass and then addition 0.5 wt% $TiO_2$ sintered at $900^{\circ}C$ demonstrated 42 in the dielectric constant(${\varepsilon}_r$), 1,000 GHz in the $Q{\times}f$ value, and $10{\pm}5\;ppm/^{\circ}C$ in the temperature coefficient of resonant frequency(${\tau}_f$).

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1275-1276
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• 2007

For fabrication of $BaTiO_3$ system Ferroelectric thick films, (Ba,Sr,Ca)$TiO_3$ (BSCT) powders, prepared by using the alkoxide-based sol-gel method, were doped $MnCO_3$ as acceptor and $Dy_{2}O_{3}$ as donor. $MnCO_3$ and $Dy_{2}O_{3}$-doped (Ba,Sr,Ca)$TiO_3$ thick films were fabricated by screen printing techniques on high purity alumina substrates. The structure and dielectric properties were investigated with variation of $Dy_{2}O_{3}$ amount. As a result of the differential thermal analysis(DTA), exothermic peak was observed at around $670^{\circ}C$ due to the formation of the polycrystalline perovskite phase. All the BSCT thick films, sintered at $1420^{\circ}C$ for 2h, showed the typical XRD patterns of perovskite polycrystalline structure and no pyrochlore phase was observed. The average grain size and thickness of specimens no doped with $Dy_{2}O_{3}$ was 1.32mm, 52mm, respectively. The relative dielectric constant decreased and dielectric loss increased with increasing amount of $Dy_{2}O_{3}$ dopant, the values of the BSCT thick films no doped with $Dy_{2}O_{3}$ were 4043 and 0.4% at 1 kHz, respectively. The relative dielectric constant gradually decreased in the measured frequency range from 0.1 to 100 kHz

• Polymer(Korea)
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• v.33 no.1
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• pp.39-44
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• 2009

Polymer substrates were fabricated by using poly (phenylene ether) as a base resin, N,N'-m-phenylenedimaleimide (PDMI) as a crosslinking agent and decabromodiphenylethane as a flame retardant. The effects of crosslinking agent and flame retardant on physical properties such as dielectric property of the substrate were investigated. Thermal curing feature of PDMI with or without an initiator was analyzed by DSC, and then, PPE-PDMI test compositions were designed based on this result. Composite sheets were cast by film coater, laminated under vacuum and pressure, and then, the changes of dielectric constant, dielectric loss, peel strength, solder heat resistance and inflammability according to increasing amount of PDMI and flame retardant were evaluated, Dielectric constant and dielectric loss showed increasing trend with increasing amount of PDMI and flame retardant, but solder heat resistance and inflammability were improved. Peel strength was obtained higher than 1 kN/m when PDMI above 10 wt% was added, but slightly decreased as the amount of flame retardant increased. From the measured gel contents, the reaction mechanism of PPE-PDMI system was deduced to the formation of network structure by crosslinking PDMI with PPE rather than the formation of semi-IPN structure. In conclusion, the polymer composite substrate materials with dielectric constant of 2.52$\sim$2.65 and dielectric loss below 0.002 at 1 GHz were obtained and they will be proper for high frequency applications.