Entity

Time filter

Source Type


Ben Taher Y.,University of Sfax | Moutia N.,Laboratoire Of Physique Des Materiaux Et Des Nanomateriaux Appliquee A Lenvironnement | Oueslati A.,University of Sfax | Gargouri M.,University of Sfax
RSC Advances | Year: 2016

Rubidium aluminium diphosphate was synthesized by a conventional solid-state technique and its conduction properties determined by impedance spectroscopy. X-ray diffraction analysis indicated the formation of a single-phase monoclinic structure (space group P21/c). The AC conductivity was determined using impedance spectroscopy over the frequency and temperature ranges of 40 Hz to 7 MHz and 400-700 K, respectively. The real and imaginary parts of the complex impedance were well-fitted to the equivalent circuit model and the frequency dependence of the AC conductivity followed Jonscher's law. The close values of the activation energies obtained from the relaxation time and the grain conductivity (σg) indicated that transport could be modelled by a hopping mechanism, probably dominated by the movement of Rb+ cations. The correlated barrier hopping model was used to describe the dominant conduction mechanism. A single relaxation peak was observed in the imaginary part of the modulus suggesting the grain response of the system. © The Royal Society of Chemistry 2016. Source


El Ghoul J.,Laboratoire Of Physique Des Materiaux Et Des Nanomateriaux Appliquee A Lenvironnement | El Mir L.,Laboratoire Of Physique Des Materiaux Et Des Nanomateriaux Appliquee A Lenvironnement | El Mir L.,Islamic University
Journal of Luminescence | Year: 2014

Zn2SiO4 and Zn2SiO4:Mn particles embedded in SiO2 host matrix prepared by sol gel method under supercritical conditions of ethyl alcohol in two steps. Were prepared by a simple solid-phase reaction under natural atmosphere at 1200 C after the incorporation of ZnO and ZnO:Mn nanoparticles, respectively, in silica monolith. In the case of SiO2/Zn2SiO4 nanocomposite, the powder with an average particle size of 80 nm shows a strong luminescence band centred at around 760 nm in the visible range. In addition, the PL spectrum for the SiO2/Zn2SiO4:Mn nanocomposite showed that a dominant peak at 525 nm appeared, which originated from the 4T 1-6A1 transitions of Mn2+ ions. The luminescence properties of nanocomposites were characterized by emission and excitation spectra as well their dependencies of upon temperature and power excitation density. © 2013 Elsevier B.V. Source


Omri K.,Laboratoire Of Physique Des Materiaux Et Des Nanomateriaux Appliquee A Lenvironnement | El Ghoul J.,Laboratoire Of Physique Des Materiaux Et Des Nanomateriaux Appliquee A Lenvironnement | Alyamani A.,King Abdulaziz City for Science and Technology | Barthou C.,CNRS Nanosciences Institute of Paris | And 2 more authors.
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2013

Green light emitting Mn2+ doped Zn2SiO4 particles embedded in SiO2 host matrix were synthesized by a sol-gel method. After the incorporation of ZnO:Mn nanoparticles in a silica monolith using sol-gel method with supercritical drying of ethyl alcohol in two steps, it was heat treated in air at 1200 C for 2 h in order to obtain the SiO 2/α-Zn2SiO4:Mn nanocomposites. The microstructure of phosphor crystals was characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). XRD results indicate that the pure phase α-Zn2SiO4 with rhombohedral structure was obtained after thermal treatment at 1200 C. The SiO2/α-Zn 2SiO4:Mn nanocomposites with a Mn doping concentration of 1.5 at% exhibit two broadband emissions in the visible range: a strong green emission at around 525 nm and a second one in the range between 560 and 608 nm. This nanocomposite with a Mn doping concentration of 0.05 shows the highest relative emission intensity. Upon 255 nm excitation, the luminescence decay time of the green emission of Zn2SiO4:Mn around 525 nm is 11 ms. The luminescence spectra at 525 nm (4T1- 6A1) and lifetime of the excited state of Mn2+ ions-doped Zn2SiO4 nanocrystals are investigated. © 2013 Elsevier B.V. Source


Rahmouni H.,Laboratoire Of Physique Des Materiaux Et Des Nanomateriaux Appliquee A Lenvironnement | Selmi A.,University of Monastir | Khirouni K.,Laboratoire Of Physique Des Materiaux Et Des Nanomateriaux Appliquee A Lenvironnement | Kallel N.,University of Monastir
Journal of Alloys and Compounds | Year: 2012

Transport measurements have been performed on La 0.7Sr 0.3Mn 1-xCr xO 3 using impedance spectroscopy technique, in order to study its electrical properties. The results indicate that the electrical properties of the material are strongly dependent on temperature and frequency. Evidences of temperature dependent electrical relaxation phenomena in the material have also been observed. Impedance spectrum analysis shows that the material can be described as a grain and grain boundary medium and permits to estimate the grain boundary contribution. Hopping mechanism dominates at small concentration. Electronic conduction is found to be dominated by thermally activated hopping of small polarons at high temperature and variable range hopping at low temperature. When the concentration of chromium increases, electrical behaviour of the material changes from semi-insulating to metallic behaviour. A regime of percolation appears and a metallic conduction becomes dominant. © 2012 Elsevier B.V. Source


El Ghoul J.,Laboratoire Of Physique Des Materiaux Et Des Nanomateriaux Appliquee A Lenvironnement | Barthou C.,CNRS Nanosciences Institute of Paris | El Mir L.,Laboratoire Of Physique Des Materiaux Et Des Nanomateriaux Appliquee A Lenvironnement | El Mir L.,Imam Muhammad ibn Saud Islamic University
Superlattices and Microstructures | Year: 2012

We report the elaboration of vanadium-doped ZnO nanoparticles prepared by a sol-gel processing technique. In our approach, the water for hydrolysis was slowly released by esterification reaction followed by a supercritical drying in ethyl alcohol. Vanadium doping concentration of 10 at.% has been investigated. After treatment in air at different temperatures, the obtained nanopowder was characterised by various techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and photoluminescence (PL). Analysis by scanning electron microscopy at high resolution shows that the grain size increases with increasing temperature. Thus, in the case of thermal treatment at 500 °C in air, the powder with an average particle size of 25 nm shows a strong luminescence band in the visible range. The intensity and energy position of the obtained PL band depends on the temperature measurement increase. The mechanism of this emission band is discussed. © 2012 Elsevier Ltd. All rights reserved. Source

Discover hidden collaborations