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Frequency and temperature dependent transport properties of NiCuZn ceramic oxide

Hossen M. B., Hossain A. K. M. A.

Materials Science Poland

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2015

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Vol. 33, No. 2

259--267

EN

A polycrystalline sample of ceramic oxide Ni0:27Cu0:10Zn0:63Fe2O4 was prepared by the solid state reaction method. The sintered sample was well polished to remove any oxide layer formed during sintering and the two surfaces of the pellet were coated with a silver paste as a contact material. Among dielectric properties, complex dielectric constant (ε* = ε' - jε"), loss tangent (tanδ) and ac conductivity (σac) in the frequency range of 20 Hz to 2 MHz were analyzed in the temperature range of 303 to 498 K using a Wayne Kerr impedance analyzer (model No. 6500B). The experimental results indicate that ε', ε", tanδ and σacdecrease with an increase in frequency and increase with increasing temperature. The transition temperature, as obtained from dispersion curve of ε', shifts towards higher temperature with an increase in frequency. The variation of dielectric properties with frequency and temperature shows the dispersion behavior which is explained in the light of Maxwell-Wagner type of interfacial polarization in accordance with the Koop’s phenomenological theory. The frequency dependent conductivity results satisfy the Jonscher’s power law, σT (ω) = σ(o)+Aωn, and the results show the occurrence of two types of conduction process at elevated temperature: (i) low frequency conductivity, due to long-range ordering (frequency independent, region I), (ii) mid frequency conductivity at the grain boundaries (region II, dispersion) and (iii) high frequency conductivity at the grain interior due to the short-range hopping mechanism (frequency independent plateau, region III).

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Electrical conduction in Ba(Bi0.5Nb0.5)O3 ceramics. Impedance spectroscopy analysis

Prasad K., Bhagat S., Amarnath K., Choudhary S. N., Yadav K. L.

Materials Science Poland

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2010

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Vol. 28, No. 1

317--325

EN

A new lead free perovskite ceramics Ba(Bi0.5Nb0.5)O3 was fabricated by a conventional ceramic technique at 1185 °C and subsequent sintering at 1200 °C in air atmosphere. The XRD analysis of Ba(Bi0.5Nb0.5)O3 powder indicated the formation of a single-phase monoclinic structure. The ac conductivity data were found to obey the power law and showed a negative temperature coefficient for the resistance behaviour. The ac conductivity values were used to evaluate the density of states at the Fermi level, minimum hopping length and activation energy of the compound. The correlated barrier hopping model was found to successfully explain the mechanism of charge transport in Ba(Bi0.5Nb0.5)O3.

3

Dielectric relaxation and ac conductivity of WO3 added (Na1/2Bi1/2)TiO3 ceramic

Prasad K., Kumari K., Chandra K. P., Yadav K. L., Sen S.

Materials Science Poland

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2009

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Vol. 27, No. 2

373--384

EN

Ceramic samples of WO3 added (Na1/2Bi1/2)TiO3 were prepared using a high-temperature solid-state reaction method. X-ray diffraction analyses indicate the formation of a single-phase orthorhombic structure. The apparent particle size and lattice strain are estimated using the Williamson-Hall plot. Dielectric studies revealed the relaxor behaviour and addition of WO3 shifted phase transition temperature as well as depolarization temperature of (Na1/2Bi1/2)TiO3 to higher side. ac impedance plots were used to analyse the electrical behaviour of samples in function of frequency at various temperatures. The ac impedance studies revealed the presence of the grain boundary effect and evidence of a negative temperature coefficient of resistance. Cole-Cole analysis indicated a non-Debye type dielectric relaxation. The ac conductivity obeys the universal power law. The pair approximation type correlated barrier hopping model explains the universal behaviour of the s exponent. The apparent activation energy of the conduction process and density of states at the Fermi level have been discussed.

4

Impedance spectroscopy : tool for structure investigation of thin semiconductor films

Kazimierski P.

Polish Journal of Applied Chemistry

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2005

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Vol. 49, nr 1-2

111-122

EN

Impedance spectroscopy is sensitive and easy to use experimental technique which can provide significant information on material structure. It is particularly effective in investigation of semiconductor heterostructure consisting of phases characterized by different permeativity. In this case impedance spectroscopy enables estimation of the phase distribution, specific dimension and shape. In this paper a range of experimental results obtained for: amorphous silicon, microcrystalline silicon, porous silicon, hydrogenated carbon-germanium semiconductors is reviewed. A special attention has been devoted to analysis of experimental data by means of equivalent circuit method.

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A Study on a Phase Transition in Electrodeposited Thin Film Polyaniline Using AC Conductivity Measurements

Grzeszczuk M., Bator G.

Polish Journal of Chemistry

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2002

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Vol. 76 / nr 8

1143-1150

EN

Ac conductivity - temperature dependencies of Au/polyaniline/Au structures with the electrodeposited thin film polyaniline are presented. The data for the reduced and reversibly oxidized polymer samples of estimated thickness being in 10-1-100 žm range are shown. The charge transport laws are found similar to that observed for the chemically prepared conducting polymer. The observed crossover in the conductivity - temperature dependence coincides with the increase in the electrical capacitance of the polyaniline electrode reported earlier.