Electrical conductivity studies and correlated barrier hopping transport in Europium-doped graphene oxide nanocomposites

The thermoelectric properties of europium-doped graphene oxide nanocomposite and determination of barrier hopping transport parameters.

Influence of Electrochemically Exfoliated Graphite Addition on the Dielectric Properties of Epoxy/Montmorillonite Nanocomposites

The influence of hydrophilic electrochemically exfoliated graphite (EEG) and hydrophobic reduced EEG (rEEG) on the electrical conductivity, dielectric properties, and high-frequency dielectric losses of epoxy-based composites with montmorillonite was described. It was confirmed, that the addition of EEG changes the low-temperature conduction mechanism. The electrical conductivity in composite with EEG and montmorillonite was described by correlated barrier hopping model, whereas for composites with montmorillonite and rEEG two models were used: non-overlapping small polaron tunneling and correlated barrier hopping. The addition of EEG drastically changes the activation energy of charge carriers motions from 2.68 to 0.83 eV, whereas the addition of rEEG only to 2.43 eV. Also composite with EEG was characterized by highest high-frequency dielectric losses.

Electrical conductivity and vibrational studies induced phase transition in [N(C3H7)4]2ZnBr4 compound

Bis-Tetrapropylammonium tetrabromozincate was synthesized and characterized by X-ray powder diffraction, as well as vibrational and impedance spectroscopy. Rietveld’s refinement of X-ray diffractogram confirmed the crystallization of the compound through the monoclinic system (space group [Formula: see text]. A temperature study of Raman scattering revealed two phase transitions at approximately [Formula: see text] = 340 K and [Formula: see text] = 393 K. The wavenumber and the line width’s evolution as a function of temperature showed some peculiarities associated with these transitions, which suggests that they are governed by the reorientation of the organic part [N(C3[Formula: see text]][Formula: see text]. The complex impedance plotted as a double semicircular arc in the studied temperature range and the centers of these semicircles lie below the real axis, which indicates that the material is an on-Debye type. These semicircular arcs are related to the bulk and the grain boundary effects. Furthermore, the alternating current conductivity of [N(C3[Formula: see text]]2ZnBr4 obeyed Jonscher’s law: [Formula: see text] = [Formula: see text] and the conduction could be attributed to the correlated barrier hopping (CBH) model in both region(I) and (II) and the Non-overlapping Small Polaron Tunneling (NSPT) in region (III).

Перенос заряда в тонких слоях стеклообразной гибридной системы Ge-=SUB=-28.5-=/SUB=-Pb-=SUB=-14.5-=/SUB=-Fe-=SUB=-0.5-=/SUB=-S-=SUB=-56.5-=/SUB=-

Представлены результаты исследования процессов переноса заряда в тонких слоях халькогенидной гибридной системы Ge28.5Pb14.5Fe0.5S56.5. Обнаружены степенная зависимость удельной проводимости от частоты и уменьшение значения показателя степени s с увеличением температуры. Перенос заряда является термически активированным процессом с энергией активации Ea=(0.64± 0.02) эВ. Полученные результаты объясняются в рамках модели проводимости в неупорядоченных системах СВН (correlated barrier hopping). Рассчитанная доля неподеленных электронных пар указывает на то, что при введении железа материал остается в стеклообразующей области. Ключевые слова:: прыжковый механизм переноса, тонкие слои, стеклообразная гибридная система, неподеленные электронные пары.

Dielectric relaxation and study of electrical conduction mechanism in BaZr0.1Ti0.9O3 ceramics by correlated barrier hopping model

This work aims to study the electrical conduction mechanism in the dielectric material BaZr0.1Ti0.9O3(BZT) ceramics by applying AC signal in the frequency range of 102Hz to 106Hz. The phase purity and microstructure of the sample have been studied by X-ray diffraction refinement and field-emission scanning electron microscope (FE-SEM) analysis. The appearance of resonance peaks in the loss tangent at high temperature is due to inherent dielectric relaxation processes of this oxide. The temperature dependent Cole-Cole plot has been studied in details to determine both the grain and grain boundary contribution to the conductivity. Electrical modulus analysis reveals that the hopping of charge carriers is the most probable conduction mechanism in BZT ceramics. The obtained data of AC conductivity obey the universal double power law and have been discussed in terms of microstructural network characteristics. The behavior of frequency exponent n of AC conductivity as a function of temperature verify the applicability of the correlated barrier hopping (CBH) model. The AC conductivity data are used to estimate the minimum hopping length, density of states at Fermi level, thermal conductivity and apparent activation energy. The value of activation energy confirms that the oxygen vacancies play a vital role in the conduction mechanism.

Electrical Dielectric Permittivity and Conductivity Analysis of Poly(N-Carbazole) (PVK) Blending with Polyvinylpyrrolidone (PVP)

Electrical dielectric spectra and alternating current (ac) conductivity of blended poly (N-vinlycarbazole) (PVK) with polyvinylpyrrolidone (PVP) at different temperature are investigated. The polymer blends were prepared by dissolving in dimethylformamide (DMF) using drop casting method and further dried in vacuum oven. The dielectric and ac conductivity of each sample was investigated using electrochemical impedance spectroscopy (EIS) method. Dielectric permittivity studies revealed that there are significant changes in the spectra at different temperature. The ac conductivity was further analyzed by using universal power law. The hopping parameter was calculated by using correlated barrier hopping model.