Regards sur les migrations tunisiennes

Préface de Mohammed CharefNational audienceLes textes présentés dans cet ouvrage émanent des discussions menées dans le cadre du colloque international “La migration tunisienne : état des lieux, développement et enjeux”, qui s’est tenu à Gammarth, près de Tunis, les 28 & 29 mai 2007. Ces journées, coordonnées par M. Abderrazek Oueslati, ont montré l’évolution de cette migration dans l’espace et dans le temps. Les dynamiques migratoires transnationales tunisiennes, qu’elles soient estudiantines, irrégulières, féminines ou autres, ont des répercussions internes et externes qui prennent des formes originales et s’adaptent aux politiques, engendrant des recompositions démographiques, sociales, économiques et juridiques

Investigation of structural, morphological, and electrical conductivity study for understanding transport mechanisms of perovskite CH3NH3HgCl3.

peer reviewedAlong with morphological and structural studies, the temperature and frequency dependence of the electrical and dielectric properties of the CH3NH3HgCl3 (MATM) compound was investigated and analyzed. SEM/EDS and XRPD analyses proved the purity, composition, and perovskite structure of the MATM. DSC analysis reveals the existence of an order-disorder phase transition of a first-order type at about 342 ± 2 K and 320 ± 1 K (heating and cooling, respectively), attributed to the disorder of [CH3NH3]+ ions. The overall results of the electrical study provide arguments for the ferroelectric nature of this compound and aim to broaden the current knowledge on the thermally activated conduction mechanisms of the studied compound via impedance spectroscopy. The electrical investigations have shown the dominant transport mechanisms in different frequency and temperature ranges, proposing the CBH model in the ferroelectric phase and the NSPT model in the paraelectric phase. The temperature dependence of the dielectric study reveals the classic ferroelectric nature of the MATM. As for the frequency dependence, it correlates the frequency-dispersive dielectric spectra with the conduction mechanisms and their relaxation processes

A nickel-based semiconductor hybrid material with significant dielectric constant for electronic capacitors

A novel semiconducting Ni(II)-based hybrid material with the formula (C7H12N2) NiCl4, which exhibits interesting optical and electrical properties, is reported. The crystal structure was investigated using SCXRD, whereas physical properties were studied by means of thermal analysis, Ft-Infrared, optical, and electrical measurements. Its crystal packing is formed through organic rings surrounded by inorganic [NiCl4]2– tetrahedral and stacked along the a-crystallographic axis. This arrangement is stabilized by a dense network of intermolecular hydrogen bonds. The investigated compound displayed a wide absorption range across the visible spectrum, characterized by an optical gap energy of 2.64 eV, indicating its semiconducting nature and efficient sunlight absorption capabilities across various wavelengths. Such features are of utmost importance in achieving a high energy conversion efficiency in solar cell applications. Further analyses of the thermal behavior using differential scanning calorimetry revealed a single-phase transition occurring at around 413 K, which was further confirmed through electrical measurements. A deep investigation of the electric and dielectric performances demonstrated a significant dielectric constant (ε′ ∼ 104) at low frequencies and low dielectric loss at high frequencies. Thus, it highlights its exceptional dielectric potential, particularly in applications related to electronic capacitors