Laboratoire Of Physique Des Materiaux Et Des Nanomateriaux Appliquee A Lenvironnement

Gabès, Tunisia

Laboratoire Of Physique Des Materiaux Et Des Nanomateriaux Appliquee A Lenvironnement

Gabès, Tunisia
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Rhimi T.,University of Sfax | Toumi M.,University of Sfax | Khirouni K.,Laboratoire Of Physique Des Materiaux Et Des Nanomateriaux Appliquee A Lenvironnement | Guermazi S.,University of Sfax
Journal of Alloys and Compounds | Year: 2017

In this paper, the potassium lithium dihydrogenphosphate, KLi(H2PO4)2, has been investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and electrical impedance spectroscopy. The X-ray diffraction analysis indicated the little compound was found to crystallize in the monoclinic system with space group P21/c. Electrical properties were studied using complex impedance spectroscopy as a function of frequency (4–7 MHz) at various temperatures (300–420 K). The impedance plots show semicircle arcs at different temperatures and an electrical equivalent circuit has been proposed to explain the impedance results. The equivalent circuit built up by a parallel combination of resistance (R), fractal capacitance (CPE) and capacitance (C). Single relaxation peak is observed in the imaginary part of the electrical modulus, suggesting the response of grain. Moreover, the frequency dependence of the conductivity is interpreted in term of Jonschers law: σ=σDC+fn. The near activation energies, obtained from the impedance, modulus spectra and conductivity confirms, that the transport is through a proton hopping mechanism in investigated materials. © 2017 Elsevier B.V.


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.


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.


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.


El Ghoul J.,Laboratoire Of Physique Des Materiaux Et Des Nanomateriaux Appliquee A Lenvironnement | Omri K.,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 | El Mir L.,Laboratoire Of Physique Des Materiaux Et Des Nanomateriaux Appliquee A Lenvironnement
Journal of Luminescence | Year: 2013

The sol gel method is used for the preparation of undoped and manganese-doped Zn2SiO4 particles embedded in SiO 2 host matrix with supercritical drying of ethyl alcohol in two steps. Zn2SiO4 and Zn2SiO4: Mn were prepared by simple solid-phase reaction in a natural atmosphere at 1200 °C after the incorporation of the nanoparticles of ZnO and ZnO: Mn, respectively, in the silica monolith. The photoluminescence (PL) measurements show a band centered at about 760 nm in the case of non-doped Zn2SiO4 which is attributed to energy transfer from Zn2SiO4 particles to NBOHs interface defects. In the case of Manganese doped Zn 2SiO4, the PL reveals a band centered at about 525 nm attributed to Mn2+ in Zn2SiO4. Photoluminescence excitation (PLE) measurements show different origins of the emission. It was suggested that electronic transition 4T 1(4G)→6A1(6S) associated with Mn2+ ions in willemite and the presence of Mn2+ in intensive crystal field were responsible for these luminescence band centered at 525 nm. © 2013 Elsevier B.V.


El Ghoul J.,Laboratoire Of Physique Des Materiaux Et Des Nanomateriaux Appliquee A Lenvironnement | Barthou C.,CNRS Nanosciences Institute of Paris | Saadoun M.,Laboratoire Of Nanomateriaux Et Des Systemes Pour Lenergie Lanse | El Mir L.,Laboratoire Of Physique Des Materiaux Et Des Nanomateriaux Appliquee A Lenvironnement
Journal of Physics and Chemistry of Solids | Year: 2010

Vanadium-doped Zn2SiO4 particles embedded in silica host matrix were prepared by a simple solid-phase reaction under natural atmosphere at 1200 °C after the incorporation of ZnO:V nanoparticles in silica monolith using sol-gel method with supercritical drying of ethyl alcohol in two steps. The obtained sample, exhibits a strong PL band in the visible range at 540 nm and two thin emission lines in the UV range at 394 and 396 nm under intensive power excitation. Photoluminescence excitation (PLE) measurements show different origins of the emission bands. It is suggested that radiative defects attributed to vanadium in the interfaces between Zn2SiO4 particles and SiO2 host matrix resulting from heat treatment and zinc oxide excitonic emissions, were responsible for theses luminescence bands. © 2009 Elsevier Ltd. All rights reserved.


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.


Rahmouni H.,Laboratoire Of Physique Des Materiaux Et Des Nanomateriaux Appliquee A Lenvironnement | Cherif B.,Laboratoire Of Physique Des Materiaux Et Des Nanomateriaux Appliquee A Lenvironnement | Baazaoui M.,University of Monastir | Khirouni K.,Laboratoire Of Physique Des Materiaux Et Des Nanomateriaux Appliquee A Lenvironnement
Journal of Alloys and Compounds | Year: 2013

In order to study the electrical properties of the samples La 0.67Ba0.33Mn1-xFexO3, transport measurements have been performed on this compound using admittance spectroscopy technique. For all temperatures the DC conductance decreases when increasing Fe content and x = 0.10 represents the limit value of Fe concentration which destroys metallic-insulating transition. From DC conductance study, electronic conduction is found to be dominated by thermally activated hopping. Activation energy is deduced from the variation of conductance with temperature. This energy increases with increasing Fe content from Ea = 27 meV for x = 0 to Ea = 154 meV for x = 0.20. The AC conductance spectrum is found to obey Jonscher universal power law. The exponent ''n'' changes with Fe concentration (n≈- 1 for x = 0.20 and n = 0 for x = 0). This indicates that the material evolves from metallic to semi-insulating behavior when increasing Fe content. Under polarization, the conductance of the material increases and activation energy decreases for all Fe concentrations. © 2013 Elsevier B.V. All rights reserved.


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.


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
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2012

We report the synthesis 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 characterized 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 B.V. All rights reserved.

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