Papers by Keyword: Impedance Spectroscopy

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Authors: Min Ren Zhang, Hong Hui Lai, Yi Mu Lee, Chun Hung Lai, Yi Der Wu, Hsi Wen Yang
Abstract: N-type ZnO nanorod arrays and p-type NiO thin films have been prepared on the ITO substrates by chemical bath deposition (CBD) and sol-gel spin coating method, respectively, then followed by thermal treatment at 400 °C for 1 h. The ZnO nanorod arrays have length of around 1.5 μm and diameter of around 55 nm; the thickness of the NiO film is around 340 nm with average grain size of 22 nm. The sensing properties of the n-type ZnO and the p-type NiO for the detection of aqueous ethanol solutions at room temperature are investigated using electrical impedance spectroscopy (EIS). The EIS results reveal that the series resistance (Rs) is as low as 27 Ω; the charge-transfer resistance (Rct) remarkably contributes to the sensing properties of the ethanol sensor, and decreases with a decreasing concentration (99.5%-1%) from 17.0 kΩ to 2.6 kΩ. An equivalent circuit with capacitors and resistors was developed to investigate the conduction process according to complex impedance (Nyquist) diagrams. In low concentration range, the electron conduction process is dominated by the Rct and a constant phase element (CPE); however, in high concentration ethanol solution, the conduction process is dominated by polarization and decomposition of the absorbed water with larger Rct observed. Moreover, I-V measurements were carried out to evaluate the sensitivity of n-ZnO and p-NiO nanostructures at room temperature.
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Authors: P. Kuppusami, T. Dharini, Ajith Kumar Soman, A.M. Kamalan Kirubaharan, Arul Maximus Rabel
Abstract: In this study, a systematic investigation on in-situ sintering behavior of Ni-YSZ (50: 50wt. %) pellets of density of 4.2 (low density) and 4.9 g/cm3 (high density) in ambient and oxygen environment by impedance spectroscopy is presented. X-ray diffraction indicated the formation of cubic phases of NiO and YSZ. The low density pellet sintered for 16 h showed low content of monoclinic phase when compared to high density pellet. The microstructure of the high density pellet revealed finer and homogenous distribution of Ni in YSZ matrix due to longer sintering duration when compared with the low density pellet. AC impedance spectra were recorded for both low and high density pellets during sintering in ambient and oxygen environment in the temperature range 873-1173 K. The results indicate that for both the pellets, the impedance values decreased when sintering temperature increased from 873 to 1173 K in both ambient and oxygen environment. However, the impedance was low while sintering in oxygen atmosphere than in ambient. Besides these observation, impedance of the high density pellet was much lower than that of the low density pellet at all sintering temperature in both ambient and oxygen atmosphere. While the impedance decreased with increasing sintering temperature, the capacitance increased slowly in both the ambient and oxygen atmosphere. The change in the impedance behavior due to grain interior and grain boundaries is explained in relation with the microstructural changes that occur during sintering in different environments.
237
Authors: Kapil Sood, K. Singh, O.P. Pandey
Abstract: La0.95Sr0.05GaO2.975 has been prepared by conventional solid state reaction method. The calcined sample has been isostatically pressed into pellets at a load of 12 kN cm-2 and then sintered at 1400 °C for 12h. The crystalline phase formation and composition has been examined by X-ray diffraction (XRD) method. Dielectric relaxation of the samples has been investigated in the steps of 25 °C in the temperature range 200-600 °C and frequency range of 1-106 Hz. The bulk and grain boundary contribution with frequency has been studied using Nyquist plots. The equivalent circuit model have been drawn which are well fitted with the plots. The activation energy has been found in the range of Ea = 0.95 eV which indicates that the prepared sample is essentially ionic conductor.
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Authors: B.D. White, Olivera Kesler
Abstract: Porous composite cathodes containing (La0.8Sr0.2)0.98MnO3 (LSM) and yttria stabilized zirconia (YSZ) for use in solid oxide fuel cells (SOFCs) have been produced by air plasma spraying. Deposition was carried out using axial powder injection for increased deposition efficiency and composition control. A number of composite cathodes were produced using different combinations of parameter values within the identified range. Successful coatings were then characterized for composition and porosity using EDX and SEM. As a result of these tests, combinations of input parameter values were identified that are best suited to the production of coatings with microstructures appropriate for use in SOFC composite cathodes.
299
Authors: F. Mansfeld, L.T. Han, C.C. Lee, G. Zhang
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Authors: Yi Qing Zhang, Wen Jun Cao, Ai Min Li
Abstract: Composition of an AlGaAs/GaAs/Ge triple-junction solar cell were analyzed using an equivalent circuit. The currentvoltage (IV) characteristics and impedance spectroscopy (IS) of it were measured in the temperature range from 20°C to 180°C. In the high-temperature range (from 140°C to 200°C) the VOC changes faster than those in the low-temperature range (from 20°C to 80°C).This is because contribution of the VOC from the Ge subcell becomes nearly zero in the high temperature. R and C of the bottom subcell keep almost the same in the high temperature.
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Authors: Lubos Pazdera, Libor Topolář, Marta Kořenská, Jaroslav Smutny, Ivo Kusák, Miroslav Lunak
Abstract: It is known that concrete is one of the most popular building materials nowadays. There are many traditional, mainly destructive methods for monitoring its properties during its lifetime. It is clear that its properties depend significantly on the composition of concrete mixture. Concrete lifetime depends mainly on curing during the first 7 days after making the mixture. The paper shows the possibilities of applying Acoustic Emission and Impedance Spectroscopy methods during the early age of concrete.
257
Authors: Agata Lisińska-Czekaj, Beata Wodecka-Duś, Dionizy Czekaj
Abstract: Impedance spectroscopy is known as an important technique used for describing the electrical processes occurring in a system on applying an ac signal as input perturbation. In the present paper results of a study of BiNbO4 ceramics fabricated by mixed oxide method and sintered by free sintering are reported. Results on the ac response of the electroceramic samples by impedance spectroscopy at temperature T= 100 – 400 °C are given. The usual representation (i.e. Z” vs. Z’ where Z’ and Z” are the real and imaginary parts of the complex impedance, respectively) as well as the alternative representations of the impedance measurement (electrical modulus representation) was used to interpret the impedance spectra of BiNbO4 ceramics in order to obtain separate contributions of the bulk, grain boundary and electrode processes. The Kramers-Kronig data validation test was employed in the impedance data analysis. Experimental data of impedance spectroscopy were fitted to the corresponding equivalent circuit using the complex non-linear least squares method. Agreement between experimental and simulated data was established.
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Authors: Beata Wodecka-Dus, Jolanta Dzik, Henryk Bernard, Katarzyna Osinska, Agata Lisińska-Czekaj, Dionizy Czekaj
Abstract: In the present paper the synthesis conditions for fabrication of Bi1−xNdxFeO3 ceramics are reported. The single phase polycrystalline samples of Bi1−xNdxFeO3 were prepared by standard solid state reaction method from the mixture of oxides viz.: Bi2O3, Fe2O3 and Nd2O3. The samples were characterized by impedance spectroscopy in the frequency range 10Hz – 1MHz at room temperature.
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