• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 춘계학술회의 초록집
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• pp.21-21
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• 2010

(Ba,Sr)$TiO_3$ (BST) thin film with a perovskite structure has potential for the practical application in various functional devices such as nonvolatile-memory components, capacitor, gate insulator of thin-film transistors, and electro-optic devices for display. Normally, the BST thin films derived from sol-gel and sputtering are amorphous or partially crystalline when processed below $600^{\circ}C$. For the purpose of integrating BST thin film directly into a Si-based read-out integrated circuit (ROIC), it is necessary to process the BST film below $400^{\circ}C$. The microstructural and electrical properties of low-temperature crystallized BST film were studied. The BST thin films have been fabricated at $350^{\circ}C$ by UV-assisted rapidly thermal annealing (RTA). The BST films are in a single perovskite phase and have well-defined electrical properties such as high dielectric constant, low dielectric loss, low leakage current density, and high breakdown voltage. Photoexcitation of the organics contained in the sol-gel-derived films by high-intensity UV irradiation facilitates elimination of the organics and formation of the single-crystalline phase films at low temperatures. The amorphous BST thin film was transformed to a highly (h00)-oriented perovskite structure by high oxygen pressure processing (HOPP) at as low as $350^{\circ}C$. The dielectric properties of BST film were comparable to (or even better than) those of the conventionally processed BST films prepared by sputtering or post-annealing at temperature above $600^{\circ}C$. When external pressure was applied to the well-known contractive BST system during annealing, the nucleation energy barrier was reduced; correspondingly, the crystallization temperature decreased. The UV-assisted RTA and HOPP, as compatible with existing MOS technology, let the BST films be integrated into radio-frequency circuit and mixed-signal integrated circuit below the critical temperature of $400^{\circ}C$.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권9호
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• pp.459-463
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• 2004

In this study, the (l-x)$TiTe_3O_{8}$-x$MgTiO_3$ ceramics were investigated to obtain the improved dielectric properties of a high temperature stability and a sintering temperature of less than $900^{\circ}C$ which was necessary for the LTCC. According to the X-ray diffraction patterns of the (l-x)$TiTe_3O_{8}$-x$MgTiO_3$(x=0∼1) ceramics, the columbite structure of $TiTe_3O_{8}$ and ilmenite structure of $MgTiO_3$ were coexisted. Increasing the $MgTiO_3$ mole ratio(x), the density and dielectric constant were decreased and temperature coefficient of resonant frequency was moved to the negative direction and the quality factor was increased. In the case of the 0.6$TiTe_3O_{8}$-0.4$MgTiO_3$ ceramics sintered at $830^{\circ}C$ for 3hr., the microwave dielectric properties were $\varepsilon_{\gamma}$=29.3, Q${\times}$$f_{\gamma}$=39.600GHz and $\tau$$_{f}$=+9.3ppm/$^{\circ}C$.

• Journal of the Korean Physical Society
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• 제73권10호
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• pp.1561-1565
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• 2018

The dielectric properties of the uniaxial relaxor ferroelectric $Sr_xBa_{1-x}Nb_2O_6$ with x = 0.75 were investigated along the polar [001] direction as a function of temperature. The capacitance maximum showed the frequency dispersion commonly observed in relaxors. Additional weak dielectric anomalies were observed in the paraelectric phase; they were only seen during the heating process and disappeared upon subsequent cooling. These were attributed to the existence of large polar clusters strongly pinned at defects and/or to random fields and their metastable characters. Aligning the ferroelectric domains along the polar axis at room temperature removed the high-temperature dielectric anomalies. The dependences of the capacitance and the dielectric maximum temperature on the magnitude of the poling field were investigated.

• E2M - 전기 전자와 첨단 소재
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• 제7권3호
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• pp.187-199
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• 1994

In order to find an effect of structural changes due to variation of addition ratio of anhydride hardener and postcuring herat-treatments upon electrical properties of epoxy composites, the dielectric properties over a frequency range from 30[Hz] to l[MHz] were investigated in the temperature range of 20-180[.deg. C]. From the dielectric properties, the a peaks related with glass-transition phenomena of epoxy network appeared near 130[.deg. C], the conduction loss in high temperature region above 150[.deg. C] due to thermal dissociation of hardener started off with the low frequency side and the .betha. peak concerned with contribution of movable unreacted terminal epoxy groups and curing agents in the glass states concurred with the high-frequency side below 20[.deg. C]. And an effect of an hydride hardener upon structural changes and of postcuring heat treatments upon structural stability in epoxy composites would be explained through the estimation of the distribution of relaxation times and the activation energy for a .alpha. peak according to the WLF equations.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.48-48
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• 2010

In this paper, we have investigated temperature dependence of dielectric breakdown voltage at epoxy with added nano-filler(MgO), which is used as a filler of epoxy additives for HVDC(high voltage direct current) submarine cable insulating material with high thermal conductivity and restraining tree to improve electrical properties of epoxy resin in high temperature region. In order to find dispersion of the specimen, the cross sectional area of nano-composite material is observed by using the SEM(Scanning Electron Microscope) and it is conformed that each specimen is evenly distributed without the cohesion. As a result, it is confirmed that the strength of breakdown of all specimen at 50 [$^{\circ}C$] decreased more than that of the dielectric breakdown strength at room temperature. When temperature increases from 50 [$^{\circ}C$] to 100 [$^{\circ}C$], we have confirmed that breakdown strength of virgin specimen decreases, but specimens with added MgO show constant dielectric breakdown strength.

• 한국전기전자재료학회논문지
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• 제21권12호
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• pp.1118-1123
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• 2008

High voltage multilayer ceramic capacitors (MLCCs) are classified into two classes-those for temperature compensation (class I) and high dielectric constant materials (class II). We manufactured high voltage MLCC with temperature coefficient characteristics of C0G and X7R and studied the characteristics of electric properties. Also we studied the characteristics of dielectric breakdown voltage (V) as the variation of thickness in the green sheet and how to pattern the internal electrodes. The dielectric breakdown by electric field was caused by defects in the dielectric materials and dielectric/electrode interface, so the dielectric thickness increased, the withstanding voltage per unit (E) thickness decreased. To overcome this problem, we selected the special design like as floating electrode and this design affected the increasing breakdown voltage(V) and realized the constant withstanding voltage per unit thickness(E). From these results, high voltage application of MLCCs can be expanded and the rated voltage can also be develop.

• 한국응용과학기술학회지
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• 제35권3호
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• pp.676-682
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• 2018

주파수 변화에 따른 에폭시 복합체의 전기적 특성을 알아보기 위하여 온도 범위 $20[^{\circ}C]$, $100[^{\circ}C]$, $140[^{\circ}C]$, 주파수 범위 30[Hz]~3[MHz] 사에서 유전율 및 유전손실을 측정하였다. 저주파 영역에서 유전분산과 유전 손실이 나타나고 있음을 확인하였다. 또한 고온 영역에서는 충진제의 영향으로 유전율이 감소하는 것을 확인하였다.

• 한국재료학회지
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• 제16권8호
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• pp.466-472
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• 2006

The electrical, dielectric properties, and its stability of ZPCCL-based varistors were investigated for different sintering temperatures in the range of $1230{\sim}1300^{\circ}C$. As the sintering temperatures increased, the varistor voltage decreased in the range of $777.9{\sim}108$ V/mm, the nonlinear coefficient decreased in the range of $77.9{\sim}7.1$, and the leakage current increased in the range of $0.3{\sim}50.6\;{\mu}A$. The stability of electrical and dielectric characteristics was obtained from sintering temperature of $1260^{\circ}C$. the varistors sintered at $1260^{\circ}C$ marked the high electrical and dielectric stability, with $%{\Delta}{V_{1mA}=+1.9%,\;%{\Delta}{\alpha}=-10.6%,\;%{\Delta}I_L=+20%\;and\;%{\Delta}tan\;{\delta}=+9.9%$ for DC accelerated aging stress state of $0.95V_{1mA}/150^{\circ}C$/24 h.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1562-1563
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• 2011

Partial discharge measurement is one of the effective diagnostic techniques to predict abnormal high voltage dielectric insulation conditions of the electric equipments. Recently partial discharge diagnostic techniques were also utilized to evaluate the cryogenic dielectric insulation of high temperature superconducting electric equipment in liquid nitrogen. Generally, liquid nitrogen at 77 K is used used as the cryogenic and dielectric media for many high temperature superconducting high voltage applications. When a quench in the superconductor occurs, bubbles are generated which can affect the dielectric properties of the liquid nitrogen. So in order to reduce the bubble formation, subcooled nitrogen was also employed for this purpose. In this work, investigation of partial discharge characteristics of subcooled liquid nitrogen were conducted in order to clarify the retardation of partial discharge initiation voltage according to the different subcooling temperature of liquid nitrogen. And also the relation of partial discharge phenomena and the activities of bubbles were analyzed. It was observed that PD inception voltages shows rather different characteristics according to the decrease of subcooling temperature and the activities of bubbles were strongly influenced by temperature of the subcooled liquid nitrogen.

• E2M - 전기 전자와 첨단 소재
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• 제10권6호
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• pp.533-540
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• 1997

The microwave dielectric properties of ((P $b_{1-x}$ C $a_{x}$)Zr $O_3$ and (P $b_{0.63}$,C $a_{0.37-x}$ $M_{x}$)Zr $O_3$(M=Mg,Sr) ceramics were investigated. In (P $b_{1-x}$ C $a_{x}$)Zr $O_3$ (X=0.33~0.40) ceramics, high quality factor and small temperature coefficient of resonant frequency were obtain in (P $b_{0.63}$C $a_{0.37}$)Zr $O_3$with perovskite structure. In the case of (P $b_{0.63}$C $a_{0.37-x}$M $g_{x}$)Zr $O_3$ dielectric constant temperature coefficient of resonant frequency increased and quality factor decreased due to increase of polarization of A-O bonding. When replacing Ca ion with Sr ion with large ion radius, polarization decreased with increased of bonding length and thus dielectric constant and temperature coefficient of resonant frequency decreased.decreased.creased.