• E2M - 전기 전자와 첨단 소재
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• 제8권1호
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• pp.83-89
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• 1995

In this paper, the specimens-($Ba_{0.997}$ L $a_{0.003}$)Ti $O_{3}$ + xTi $O_{2}$, x=0.005, 0.01, 0.02, 0.03[mol]- were fabricated by a solid-state reaction method which is easy in microstructure control and good in mass production. Their crystalline structures and microstructures were analysed, and electrical properties were investigated. The perovskite-crystalline structure is confirmed by XRD, and it is exhibited by SEM that the grain grows with an addition of Ti $O_{2}$. Resistivity decreases with increasing sinteiing temperature, and the specimen of ($Ba_{0.997}$ L $a_{0.003}$)Ti $O_{3}$ + 0.02Ti $O_{2}$ sintered at 1350.deg. C shows the best PTC effects. The complex impedance plots exhibit the serial equivalent circuit of ( $R_{gb}$ / $C_{gb}$ ) and $R_{g}$ it is realized that PTC effect is attributed to the resistivity of grain boundary.ary.y.

• 한국세라믹학회지
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• 제28권2호
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• pp.101-108
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• 1991

0.2 mo1% La doped BaTiO3 samples were prepared by a wet chemical process (Pechini process) and electrical conductivity were measured from annealing temperatures(800-110$0^{\circ}C$) to room temperature continuously. 2 probe I-V characteristics showed that Pt electrodes were non-ohmic below about 80$0^{\circ}C$ for Ladoped sample. I-V curves showed varistor behavior and breakdown voltages showed PTC-like behavior. AC complex impedance of 0.2 La and 0.05 Mn mo1% doped BaTiO3 samples with three different electrodes (electroless Ni, Pt, Ag electrodes) were measured with temperature variation. Complex impedance plots showed that the samples with electroless Ni electrodes have negligible electrode resistance. Samples with Ag or Pt paste electrodes showed large electrode resistance. PTC effect, which is defined as the ratio of maximum resistance to minimum resistance, was found to be less than 10 for 0.2 mo1% La doped dense sample however greater than 105 with codoping of 0.05 mo1% Mn and 0.2 mol% La.

• 전기화학회지
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• 제13권4호
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• pp.223-234
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• 2010

본 총설에서는 캐패시터적인 특성을 가지는 다공성 전극의 전기화학특성 분석에 활용되는 임피던스의 복소캐패시턴스 분석법(complex capacitance analysis)의 이론 및 응용에 대해 정리하였다. 이론적으로 캐패시터적인 특성을 갖는 전기화학시스템에 대해 캐패시턴스허수부 도시를 활용하면 효과적인 해석이 가능함이 제시되었다. 또한, 복소캐패시턴스 분석법은 다공성 탄소 재료/전극의 EDLC 특성, 미세기공 내부의 이온전도 특성, 고분자전해질연료전지의 촉매층 이온저항 등의 분석에 효과적으로 적용될 수 있음이 검증되었다.

• 한국세라믹학회지
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• 제27권4호
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• pp.529-535
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• 1990

This paper describes the factors which control the impedance-relative humidity characteristics of the TiO2-V2O5 humidity sensor. To obtain the quantitative relationships between impedance and many manufacturing parameters such as V2O5mol%, the sintering time and temperature, various sets of samples are preared and tested. With changing relative hymidity from 20% to 80%, it is measrued that the corresponding capacitance and impedance from the semicircles which complex impedance plots make. As a result we found that the impedance-relative humidity characteristics are mainly controlled by the doping amount of V2O5 total pore volume and bulk resistence of the elements. We can assume the equivalent circuits of each samples and finally control the sintering time to get a linear humidity impedance response curve which plays an important role in device making. 4mol% V2O5-TiO2 specimen sintered at 90$0^{\circ}C$ for 10min. show liear log(Z) vs. RH characteristics and 10mol% V2O5-TiO2 specimen sintered at the same temp. for 20min. show linear (Z) vs. RH.

• 한국재료학회지
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• 제29권12호
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• pp.753-756
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• 2019

Orthorhombic dysprosium manganite DyMnO₃ with single phase is synthesized using solid-state reaction technique and the crystal structure and dielectric properties as functions of temperature and frequency are investigated. Thermally activated dielectric relaxations are shown in the temperature dependence of the complex permittivity, and the respective peaks are found to be shifted to higher temperatures as the measuring frequency increases. In Arrhenius plots, activation energies of 0.32 and 0.24 eV for the high- and low-temperature relaxations are observed, respectively. Analysis of the relationship between the real and imaginary parts of the permittivity and the frequencies allows us to explain the dielectric behavior of DyMnO₃ ceramics by the universal dielectric response model. A separation of the intrinsic grain and grain boundary properties is achieved using an equivalent circuit model. The dielectric responses of this circuit are discerned by impedance spectroscopy study. The determined grain and grain boundary effects in the orthorhombic DyMnO₃ ceramics are responsible for the observed high- and low-temperature relaxations in the dielectric properties.

• 전기화학회지
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• 제6권4호
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• pp.255-260
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• 2003

다공성 탄소전극의 전위에 짜른 EDLC(e)ectric double-layer capacitor)특성을 조사하기 위해 복소캐패시턴스분석(complex capacitance analysis)을 수행하였다. 하나의 원통형 기공에 대해 복소캐패시턴스를 이론적으로 유도하였고, 기공의 분포를 고려하여 다공성 전극에 대하여서도 계산하였다. 복소캐패시턴스의 허수부를 주파수에 대해 도시하면 피크 형태의 곡선이 얻어지는데, 이때 피크의 면적은 캐패시턴스 값의 크기와, 피크의 위치는 다공성전극의 전기화학 파라매터와 기공구조에 의해 결정되는 $\alpha_0$와 상관관계가 있음을 알 수 있었다. 이를 이용하면, 동일한 기공구조를 갖는 전극에 대해, 전위에 따른 캐패시턴스와 기공 내 이온전도도의 변화를 측정할 수 있다. 메조포러스 탄소전극에 대하여 전위를 변화시키며 electrochemical impedance spectroscopy를 측정하고 이를 복소캐패시턴스법에 의해 분석하였다. 피크 면적으로부터 구한 전위에 따른 캐패시턴스는 0.3V부근에서 최대값을 가졌는데, 이는 cyclic voltammetry 실험결과와도 일치하였다. 한편, 피크 위치로부터 구한 기공 내 이온전도도는 0.2V에서 최대 값을 가지고 전위가 증가할 수록 서서히 감소하였다. 이를 탄소 표면전하의 증가로 인해 이온/표면의 전기적 작용력이 커졌기 때문으로 해석하였다.