• 한국군사과학기술학회지
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• 제25권6호
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• pp.580-585
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• 2022

In this study, the high-temperature dielectric constant of Si₃N₄ ceramics, a representative non-oxide-based radome material, was evaluated and the cause of the dielectric constant change was analyzed in relation to the oxidation behavior. The dielectric constant of Si₃N₄ ceramics was 7.79 at room temperature, and it linearly increased as the temperature increased, showing 8.42 at 1,000 ℃. As results of analyzing the microstructure and phase for the Si₃N₄ ceramics before and after heat-treatment, it was confirmed that oxidation did not occur at all or occurred only on the surface at a very insignificant level below 1,000 ℃. Based on this, it is concluded that the increase in the dielectric constant according to the temperature increase of Si₃N₄ ceramics is irrelevant to the oxidation behavior and is only due to the activation of charge polarization.

• 한국전기전자재료학회논문지
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• 제16권9호
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• pp.795-800
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• 2003

The dielectric and piezoelectric properties of the xPb(A $l_{0.5}$N $b_{0.5}$) $O_3$-(1-x)Pb(Z $r_{0.52}$ $Ti_{0.48}$) $O_3$ [xPAN-(1-x)PZT] thin films by pulsed laser deposition (PLD) were investigated as a function of PAN contents. The effect of texture on dielectric and piezoelectric properties of the 0.05PAN-0.95PZT thin films having the highest piezoelectric constant( $d_{33}$) was studied more precisely. For 0$\leq$x$\leq$0.15 compositions in xPAN-(1-x)PZT thin films, the well-developed perovskite phase with (111) preferred orientation was obtained at the deposition temperature of 50$0^{\circ}C$. With increasing PAN content, remanent polarization and coercive field decreased. The dielectric constant increased with an increase of PAN content until it reached 1450 at $\chi$= 0.05, and then decreased for higher PAN content. The maximum points of dielectric constant coincides with the maximum points of the piezoelectric constant $d_{33}$.33/.33/././.

• 한국세라믹학회지
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• 제20권4호
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• pp.315-323
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• 1983

Effect of NiO and $MnO_2$ addtivies on the dielectric piezoelectrics and polarization-reversal properties of $(Pb_{0.936} La_{0.064})$$(Zr_{0.60}Ti_{0.40})O_3$ ceramics have been investigated. The specimens were prepared by the mixed oxide techni-que and atmosphere sintering method. The room temperature X-ray diffraction studies show that perfect perovskite solution with tetragonal structure was obtained from PLZT and its additives. The dielectric constant and dissipation factor decreased with the addition of both NiO and $MnO_2$ The Curie of Curie temperature was not observed but they displayed broadened maxima. The planar coupling factor was improved by addition of NiO and also increased with increasing sintering time carried out at 105$0^{\circ}C$ Addition of $MnO_2$ yielded a markedly high mechanical quality factor. The space-charge field decreased with the addition of NiO but increased with the addition of $MnO_2$ The planar coupling factor and space-charge field showed same dependence on the additivies. The tetragonality Curie temperature and planar coupling factor of $(Pb_{0.936} La_{0.064})$$(Zr_{0.60}Ti_{0.40})O_3$ were higher than those of $(Pb_{0.936} La_{0.064})$$(Zr_{0.568}NU_{0.032}Ti_{0.40})_{0.984}O_3$ but the grain size lattic parameter dielectric constant dissipation factor mechanical quality factor and space-charge field of the former were lower than those of the latter.

• 한국전기전자재료학회논문지
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• 제14권1호
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• pp.20-25
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• 2001

To develop the piezoelectric actuator, the structural, dielectric and piezoelectric properties and electric fieldinduced strain of the ceramics(Pb$\_$1-2/Ba$\_$x/)[Mg$\_$1/2/W$\_$1/2/)$\_$0.03/-Ni$\_$1/3/Nb$\_$2/3/)$\_$0.12/-(Zr$\_$0.5/Ti$\_$0.5/)$\_$0.85/]O$_3$(x=0, 0.01, 0.03, 0.05, 0.07, 0.1) were investigated with the substitution of Ba. The tetragonality of crystal structure and grain size decreased by the substitution of Ba. Curie temperature decreased due to the decrease of the tetragonality, and dielectric constants increased with the substitution of Ba. The coercive field, remnant polarization and electromechanical coupling factor also decreased, whereas the piezoelectric constatns d$\_$33/ and d$\_$31/ were showed the highest value of 430 and 209(x10$\^$-12/C/N), respectively, because of the increase of dielectric constant. The strain induced by 60Hz AC electric field had the maximum value of 204x10$\^$-6/Δℓ/ℓ at the substitution of Ba 3mol%. As the applied electric field approaches to the coercive field, the piezoelectric element is depolarized and the electric field induced strain revealed non-linearity.

• 한국세라믹학회지
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• 제36권9호
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• pp.915-922
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• 1999

Microwave dielectric properties and far infrared reflectivity spectra of the (Zr0.8Sn0.2)TiO4 ceramics were inves-tigated with the various cooling rate. Dielectric constant was nearly same value while the unloaded Q value was largely affected by cooling rate. The Q.f of 42,140 at 7 GHz was obtained for the specimens with cooling rate of 1$^{\circ}C$/min. The effect of the cooling rate on the change of the ionic the electronic polarization and the intrinsic microwave loss of the specimens were investigated by the infrared reflectivity spectra from 50 to 4000cm-1 which were calculated by Kramers-Kroning analysis and the classical oscillator model. The relative tendency of microwave dielectric properties of the specimens calculated from the relfectivity data were in good agreement with the results by the post resonant method.

• 대한전자공학회논문지SD
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• 제48권8호
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• pp.1-4
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• 2011

SiOC 박막과 같은 유무기 하이브리드 저유전 물질에서의 열처리효과에 의한 전기적인 특성의 변화와 유전상수에 관하여 연구하였다. SiOC 박막은 분극에 따른 특성을 분석하기 위해서 TMS과 산소의 혼합가스를 이용한 CVD방법에 의하여 증착되었으며, 300~500도까지 변화하면서 열처리를 하였다. SiOC 박막은 열처리에 의하여 유전상수는 더욱 낮아지며, 400도에서 열처리 한 경우 전기적인 특성이 우수한 것을 확인하였다. XRD 패턴에 의하면 300도이하에서 열처리한 박막과 400도 이상에서 열처리 한 경우 결합구조가 달라지는 것을 알 수 있고 400도 근처에서 급격한 변화가 일어나고 있는 것을 확인하였다.

• 대한화학회지
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• 제34권5호
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• pp.404-412
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• 1990

시간분해 ESR 분광법에서는 CIDEP법과 흡수 ESR 분광법을 사용하였다. 2-프로판올과 트리에틸아민 혼합용매에서 anthraquinone이 레이저 광선에 의해서 생성된 anthraquinone 라디칼 음이온을 시간분해 ESR 분광법으로 측정하였다. 이 semiquinone 라디칼은 대단히 안정하여 cw ESR을 측정할 수 있었다. 분극된 semiquinone 라디칼이 열적 평형상태로 소멸되는 속도상수는 스핀-격자 완화시간의 역수로서 2.6 ${\times}\;1-^5$ sec$^{-1}$이다. 그리고, 그 라디칼의 소멸속도상수는 300.0 sec$^{-1}$이다. CIDEP스펙트럼의 시간의존성에 대한 강도 변화는 마이크로파 출력이 강할수록 일반적으로 증가하였다. 그러나, 지나치게 출력을 높이면 감소 곡선상에 Torrey 진동이 뒷따라 일어났다.

• 한국표면공학회지
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• 제34권5호
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• pp.435-444
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• 2001

WC-( $Ti_{1-x}$ A $l_{x}$) N coatings of constant changing Al concentration were deposited on S45C substrates by high-ionization sputtered PVD method. The Al concentration could be controlled by using evaporation source for Al and fixing the evaporation rate of the metals (i.e, WC- $Ti_{0.86}$A $l_{0.14}$N, WC- $Ti_{0.72}$A $l_{0.28}$N, and WC- $Ti_{0.58}$A $l_{0.42}$N). The corrosion behavior of WC-( $Ti_{1-x}$ A $l_{x}$)N coatings in a deaerated 3.5% NaCl solution was investigated by electrochemical corrosion tests and surface analyses. The measured galvanic corrosion currents between coating and substrate indicated that WC- $Ti_{0.72}$A $l_{0.28}$N coating showed the best resistance of the coating tested. The results of potentiodynamic polarization tests showed that the WC- $Ti_{0.72}$A $l_{0.28}$N coating deposited with 32W/c $m^2$ of Al target revealed higher corrosion resistance. This indicated that the WC- $Ti_{0.72}$A $l_{0.28}$N coating is effective in improving corrosion resistance. In EIS, the WC- $Ti_{0.72}$A $l_{0.28}$N coating showed one time constant loop and increased a polarization resistance of coating ( $R_{coat}$) relative to other samples. Compositional variations of WC-( $Ti_{1-x}$ A $l_{x}$)N coatings were analyzed by EDS and XRD analysis was performed to evaluate the crystal structure and compounds formation behavior. Surface morphologies of the films were observed using SEM and AFM. Scratch test was performed to measure film adhesion strength.strength. adhesion strength.strength.

• 한국재료학회지
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• 제34권5호
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• pp.242-246
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• 2024

La modified lead zirconate titanate ceramics (Pb_0.92La_0.08)(Zr_0.95Ti_0.05)O₃ = PLZT-8/95/5 were prepared using the conventional solid state reaction method in order to investigate the complex impedance characteristics of the PLZT-8/95/5 ceramic according to temperature. The complex impedance in the PLZT-8/95/5 ceramic was measured over a temperature range of 30~550 ℃ at several frequencies. The complex dielectric constant anomaly of the phase transition was observed near T_U1 = 179 ℃ and T_U2 = 230 ℃. A remarkable diffuse dielectric constant anomalous behaviour of the complex dielectric constant was found between 100 ℃ and 550 ℃. The complex impedance spectra below and above T_U1 and T_U2 were fitted by the superposition of two Cole-Cole types of impedance relaxations. The fast component in the higher frequency region may be due to ion migration in the bulk, and the slow component in the lower frequency region is interpreted to be the formation and migration of ions at the grain boundary or electrode/crystal interfacial polarization.

• 한국전자파학회논문지
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• 제10권2호
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• pp.247-256
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• 1999

유전체 코팅된 유한한 두께의 주기적인 슬롯을 갖는 명행명판 도파관으로부터 누설파 안테나를 H-편파 경 우에 대하여 해석하였다. 이러한 구조에 대해 슬롯영역의 전자계는 명행평판 도파관의 TM 모드의 합으로 전 개하고 그 외의 모든 영역의 전자계는 역퓨리에 변환을 이용하여 파수영역 형태로 표현되어진다. 경계조건을 적용하여 선형동차 방정식을 유도한다. 슬롯 폭과 슬롯 두께, 유전체층 두께, 슬롯 개수의 영향이 위상 상수. 누설 상수 및 복사패턴 등과 같은 복사 특성에 미치는 영향을 조사하였다. 유한한 슬롯 개수의 결과와 무한 구조의 결과와 비교하여 잘 일치함을 확인하였다.