A. Ben Rhaiem

Alternative current conduction mechanisms of organic-inorganic compound [N(CH3)3H]2ZnCl4

The [N(CH3)3H]2CuCl4 single crystal has been analyzed by X-ray powder diffraction patterns, differential scanning calorimetry (DSC), and electrical impedance spectroscopy. [N(CH3)3H]2CuCl4 crystallizes at room temperature in the monoclinic system with P21/C space group. Three phase transitions at T1 = 226 K, T2 = 264 K, and T3 = 297 K have been evidenced by DSC measurements. The electrical technique was measured in the 10−1–107 Hz frequency range and 203–313 K temperature intervals. The frequency dependence of alternative current (AC) conductivity is interpreted in terms of Jonschers law (developed). The AC electrical conduction in [N(CH3)3H]2CuCl4 compound is studied by two processes which can be attributed to a hopping transport mechanism: the correlated barrier hopping model in phases I, II, and III, the non-overlapping small polaron tunneling model in phase IV. The conduction mechanism is interpreted with the help of Elliots theory, and the Elliots parameters are found.

A.c. conductivity and dielectric study of LiNiPO4 synthesized by solid-state method

LiNiPO4 compound was prepared by the conventional solid-state reaction. The sample was characterized by X-ray powder diffraction, infrared, Raman analysis spectroscopy and electrical impedance spectroscopy. The compound crystallizes in the orthorhombic system, space group Pnma with a = 10·0252(7) Å, b = 5·8569(5) Å and c = 4·6758(4) Å. Vibrational analysis was used to identify the presence of

Theoretical studies of vibrational spectra of [N(CH3)4]2ZnCl4−yBry compounds with y = 0, 2 and 4

\mathrm{PO}_4^{3- }

[N(CH3)3H]2ZnCl4: Ferroelectric properties and characterization of phase transitions by Raman spectroscopy

– group in this compound. The complex impedance has been measured in the temperature and frequency ranges 654–716 K and 242 Hz–5 MHz, respectively. The Z′ and Z″ vs frequency plots are well-fitted to an equivalent circuit consisting of series of combination of grains and grain boundary elements. Dielectric data were analysed using complex electrical modulus M* for the sample at various temperatures. The modulus plots are characterized by the presence of two peaks thermally activated. The frequency dependence of the conductivity is interpreted in terms of equation:

Complex impedance analysis and ionic conductivity studies of NaBaPO4

{\sigma_{\mathrm{a}.\mathrm{c}.}}\left( \omega \right)=\left[ {{{{{\sigma_{\mathrm{g}}}}} \left/ {{\left( {1+{\tau^2}{\omega^2}} \right)}} \right.}+\left( {{{{{\sigma_{\infty }}{\tau^2}{\omega^2}}} \left/ {{1+{\tau^2}{\omega^2}}} \right.}} \right)+A{\omega^{\mathrm{n}}}} \right]

Optical, structural characterization and dielectric relaxation of [C2H5NH3]2ZnCl4 compound

. The near values of activation energies obtained from the analysis of M″, conductivity data and equivalent circuit confirms that the transport is through ion hopping mechanism dominated by the motion of Li+ in the structure of the investigated material.

Dielectric relaxation and ionic conductivity studies of [N(CH3)4]2Cu0.5Zn0.5Cl4

The infrared and Raman spectra of [N(CH3)4]2ZnCl4−yBry, where y = 0, 2 and 4, have been analyzed with ab initio calculations of the vibrational characteristics of constitutive polyhedra, tetramethylammonium [N(CH3)4]+ and [ZnCl4−xBrx]2− (x = 0, 1, 2, 3 and 4) tetrahedra. The optimized geometries, calculated vibrational frequencies, infrared intensities and Raman activities are calculated using Hartree–Fock and density functional theory B3LYP methods with 3-21G, 6-31G(d) and 6-311G+(d,p) basis sets. Calculation of the root mean square difference δrms between the observed and calculated frequencies allows to give scaling factors and to deduce that the best agreements are obtained by B3LYP/6-311G+(d,p) for [N(CH3)4]+ and B3LYP/3-21G for [ZnCl4−xBrx]2−. The present study establishes a strongly reliable assignment of the vibrational modes of [ZnCl4−xBrx]2− tetrahedra based on comparison between experimental and ab initio calculations, both of the frequencies and the intensities of the Raman signals.

Electric and dielectric studies of the [N(CH3)3H]2CuCl4 compound at low temperature

The X-ray powder diffraction pattern shows that at room temperature, [N(CH3)3H]2ZnCl4 is crystallized in the orthorhombic system with Pnma space group. The phase transitions at T1 = 255 K, T2 = 282 K, T3 = 302 K, T4 = 320 K, and T5 = 346 K have been confirmed by the differential scanning calorimetry. The electrical technique was measured in the 10−1–107 Hz frequency range and 233–363 K temperature intervals. The temperature dependence of the dielectric constant at different temperatures proved that this compound is ferroelectric below 282 K. Besides, [N(CH3)3 H]2ZnCl4 shows classical ferroelectric behaviour near curie temperature. In order to characterize the phase transitions, Raman spectra have been recorded in the temperature range of 233–383 K and the frequency range related to the internal and external vibrations of the cations and anions (90–4000 cm−1). The temperature dependence of the Raman line shifts ν and the half-width Δν detects all phase transitions and confirms their nature, especially at 2...

Dielectric properties and relaxation behavior of [TMA]2Zn0.5Cu0.5Cl4 compound

The NaBaPO4 compound was obtained by conventional solid-state reaction. The sample was characterized by X-ray powder diffraction and electrical impedance spectroscopy. The impedance plots show semicircle arcs at different temperatures, and an electrical equivalent circuit has been proposed. The circuits consist of the parallel combination of bulk resistance Rp and constant phase elements CPE. The dielectric relaxation is described by a non-Debye model. The frequency dependence of the conductivity is interpreted in term of the well-known universal dynamic response