Entity

Time filter

Source Type


Azdouz M.,Laboratoire Of Physico Chimie Des Materiaux | Azdouz M.,Laboratoire des ressources naturelles et environnement | Manoun B.,Laboratoire Of Physico Chimie Des Materiaux | Essehli R.,Ecole des Mines de Nantes | And 5 more authors.
Journal of Alloys and Compounds | Year: 2010

The new solid solution series Ba3-xSrx(VO4)2 (0 ≤ x ≤3) has been synthesized and studied by a combination of X-ray powder diffraction and Raman vibrational spectroscopy. This continuous solid solution crystallise in the hexagonal system with R over(3, ̄) m space group. The structure has been determined at room temperature from X-ray diffraction by the Rietveld method analysis. It is formed by a 3D network of (Ba/Sr)(1)(VO4)2 4- layers linked into a crystal network by (Ba/Sr)2+ (2) cations. The vibrational spectra of this crystalline orthovanadate solid solution series are interpreted by means of factor group analysis in terms of space group R over(3, ̄) m (D3 d 5). Assignments of the V-O vibrational stretching and bending modes, as well as some of the external modes, have been made. While all the modes show a monotonous shift as a function of the composition x, a break in the curves of intensities, full width at half maximum and band areas as a function of x is observed and attributed to the statistical distribution of Ba and Sr ions in the same crystallographic sites. © 2010 Elsevier B.V. All rights reserved. Source


Bensaid H.,Laboratory of Chemistry of Solid Materials | El Bouari A.,Laboratory of Chemistry of Solid Materials | Benmokhtar S.,Research Laboratory of General Chemistry Physics of Materials | Manoun B.,Laboratory of Physico Chemistry of Materials | And 2 more authors.
Journal of Molecular Structure | Year: 2013

A solid solution was found to exist in the quaternary Li 2O-CoO-NiO-MoO3 system between the two phases Li 2Co2(MoO4)3 and Li 2Ni2(MoO4)3. Both Li 2Co2(MoO4)3 and Li 2Ni2(MoO4)3 are isostructural with the mineral lyonsite, and substitution according to the formula Li 2Co2-xNix(MoO4) 3 (0 ≤ x ≤ 2) demonstrates that a complete solid solution exits. Rietveld analysis revealed that solid solution crystallizes at room temperature in orthorhombic space group Pnma (D2h). The structure shows that if the corners and edges octahedra share in the leaves, they share faces columns. Nickel and cobalt are shared statically in the trigonal prism and octahedral sites. The results of these compositions are consistent with studies where the Raman spectra. Therefore, all compositions are similar and show linear changes frequencies depending on the composition due to the substitution of Co2+ by Ni2+ with a larger radius. © 2012 Elsevier B.V. All rights reserved. Source


Manoun B.,Hassan 1er University | Azrour M.,Laboratoire Of Physico Chimie Des Materiaux | Lazor P.,Uppsala University | Azdouz M.,Laboratoire Of Physico Chimie Des Materiaux | And 4 more authors.
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2015

Abstract In this work, using techniques of X-ray diffraction and Raman spectroscopy, we report the composition and high-temperature induced phase transition in the system LiZnV1-xAsxO4 (0 ≤ x ≤ 1). Both techniques showed that the increase of arsenic amount induced a structural transition from R-3 LiZnVO4 type to LiZnAsO4 type belonging to R3 space group, the transition occurring between x = 0.7 and x = 0.8. Furthermore, increasing temperature for the compositions (0.8 ≤ x ≤ 1) manifests a transition from the LiZnAsO4 structural type with R3 space group to the R-3 LiZnVO4 structural type. For this series, the transition from the space group R3 to the centro-symmetric space group R-3 shows considerable changes in the compositional and temperature dependencies of the bands: spectral positions of all the observed Raman bands exhibit shifts linearly proportional to the temperature increase, with points of shift-rate changes revealing a symmetry change. The Raman-spectra based temperature-composition phase diagram confirms the results obtained using the method of Rietveld refinements, thus showing the R-3 to R3 transition occurring between x = 0.7 and 0.8. © 2015 Elsevier B.V. Source


Ezzahi A.,Laboratoire Des Procedes Of Valorisation Des Ressources Naturelles | Manoun B.,Laboratoire Des Procedes Of Valorisation Des Ressources Naturelles | Manoun B.,Hassan 1er University | Ider A.,Laboratoire Des Procedes Of Valorisation Des Ressources Naturelles | And 6 more authors.
Journal of Molecular Structure | Year: 2011

In this work we report on the crystal structure and Raman spectroscopy of BaSrMWO6 (MNi, Co, Mg) double perovskite oxides. The results showed that the Ni, Co and Mg containing compounds crystallize in a cubic system with the space group Fm-3 m. The double perovskite structure can be represented as a three-dimensional network of alternating MO6 and WO6 octahedra, with Ba- and Sr-atoms occupying the interstitial spaces. The Raman spectra of this crystalline perovskite oxides are interpreted by means of factor group analysis in terms of space group Fm-3 m. Assignments of the WO vibrational stretching and bending modes have been made. High temperature Raman spectroscopy of BaSrNiWO6 showed that all lattice modes illustrate a linear decrease in wavenumbers while temperature is increased. No discontinuities, in the temperature changes, in wavenumber observed for all modes recorded: indicating that the structure remains cubic and stable up the highest temperature studied here. © 2010 Elsevier B.V. All rights reserved. Source

Discover hidden collaborations