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Antony C.J.,Kingston Engineering College | Aatiq A.,Laboratoire Of Chimie Des Materiaux Solides | Bushiri M.J.,Cochin University of Science and Technology | Varghese H.T.,Fatima Mata National College | Manojkumar T.K.,Indian Institute of Information Technology and Management Gwalior
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2011

FT-Raman and FT-IR spectra of ASnFe(PO4)3 [A = Na2, Ca, Cd] were recorded and analyzed. The bands were assigned in terms of the vibrational group frequencies of SnO6 octahedral and PO4 tetrahedral. The spectral analysis shows that the symmetry of corner shared octahedral (SnO6) and the tetrahedral (PO4) are lowered from their free ion symmetry state. The presence of Fe3+ ions disrupts the S-N-O-S-N chain in the structure. This causes distortion of SnO6 and PO4 in the structure of all the compounds. Also it is seen that there are two distinct PO4 tetrahedra of different P-O bond lengths. One of these tetrahedra is linearly distorted in all the title compounds. The PO4 frequencies and bond lengths are calculated theoretically and are in agreement with the experimental values. The presence of PO4 polyanion in the structure can reduce the redox energy and hence reduce the metal oxygen covalency strength in the structure. © 2010 Elsevier B.V. All rights reserved.


Sinouh H.,British Petroleum | Bih L.,Equipe science de la Matiere Condensee | El Bouari A.,Laboratoire Of Chimie Des Materiaux Solides | Azrour M.,British Petroleum | And 2 more authors.
Journal of Non-Crystalline Solids | Year: 2014

The glasses in the Na2O-SrO-BaO-TiO2-B2O3-P2O5system were prepared by the conventional quenching route. In the present work, we studied the effect of BaSr substitution on some physical parameters such as density, molar volume, micro-hardness, glass transition temperature (Tg), and crystallization temperature (Tc) of series of glasses with the following composition 33.33Na2O-(10 - x)SrO - xBaO-10TiO2-30B2O3-16.67P2O5. The crystallization of the glasses by heat-treatments is performed and X-ray diffraction (XRD) showed the formation of a ferroelectric phase SrTiO3and Na4Ba2(PO3)6in their network. The kinetic of the crystallization is carried out by using DSC technique, and the activation energy and the Avrami parameter (n) are determined. © 2014 Published by Elsevier B.V.


Essehli R.,University Mohammed Premier | Bali B.E.,University Mohammed Premier | Benmokhtar S.,Laboratoire Of Chimie Des Materiaux Solides | Bouziane K.,Sultan Qaboos University | And 3 more authors.
Journal of Alloys and Compounds | Year: 2011

Crystal structures from two new phosphates Na4NiFe(PO 4)3 (I) and Na2Ni2Fe(PO 4)3 (II) have been determined by single crystal X-ray diffraction analysis. Compound (I) crystallizes in a rhombohedral system (S. G: R-3c, Z = 6, a = 8.7350(9) , c = 21.643(4) , R1 = 0.041, wR2=0.120). Compound (II) crystallizes in a monoclinic system (S. G: C2/c, Z = 4, a = 11.729(7) , b = 12.433(5) , c = 6.431(2) , β = 113.66(4)°, R 1 = 0.043, wR2=0.111). The three-dimensional structure of (I) is closely related to the Nasicon structural type, consisting of corner sharing [(Ni/Fe)O6] octahedra and [PO4] tetrahedra forming [NiFe(PO4)3]4+ units which align in chains along the c-axis. The Na+ cations fill up trigonal antiprismatic sites within these chains. The crystal structure of (II) belongs to the alluaudite type. Its open framework results from [Ni2O10] units of edge-sharing [NiO6] octahedra, which alternate with [FeO6] octahedra that form infinite chains. Coordination of these chains yields two distinct tunnels in which site Na+. The magnetization data of compound (I) reveal antiferromagnetic (AFM) interactions by the onset of deviations from a Curie-Weiss behaviour at low temperature as confirmed by Mössbauer measurements performed at 4.2 K. The corresponding temperature dependence of the reciprocal susceptibility χ-1 follows a typical Curie-Weiss behaviour for T > 105 K. A canted AFM state is proposed for compound (II) below 46 K with a field-induced magnetic transition at H ≈ 19 kOe, revealed in the hysteresis loop measured at 5 K. This transition is most probably associated with a spin-flop transition. © 2010 Elsevier B.V. All rights reserved.


Iturbe-Zabalo E.,Laue Langevin Institute | Iturbe-Zabalo E.,University of the Basque Country | Igartua J.M.,University of the Basque Country | Aatiq A.,Laboratoire Of Chimie Des Materiaux Solides | Pomjakushin V.,Paul Scherrer Institute
Journal of Molecular Structure | Year: 2013

The new ALn2CuTi2O9 (A = Ca, Ba; Ln = La, Pr, Nd, Sm) series have been synthesized and the structures have been characterized by X-ray and neutron powder diffraction techniques. The whole series show a cationic disordered distribution over the A- and B-sites of the perovskite structure. CaLn2CuTi2O9 samples are isostructural, crystallizing at room temperature in an orthorhombic cell with space group Pbnm (ITA No. 62); and BaLn2CuTi2O9 samples in the tetragonal I4/mcm (ITA No. 140) space group. The homovalent substitution of a larger lanthanide cation leads to an increase in the unite-cell volume, but a decrease in the Cu/TiO6 octahedra tilting. By comparing the room temperature symmetry structure with an archetype (Pm3̄m, ITA, No. 221) phase of Pbnm or I4/mcm symmetry, two distortion modes R4+ and M3+ were found to be dominant for the orthorhombic phase; whereas for tetragonal phase there is a unique active mode, R4+. They correspond to Cu/TiO6 octahedron tilt modes, commonly found in many perovskite type materials. The high temperature study for CaLa2CuTi 2O9, CaNd2CuTi2O9 and CaSm2CuTi2O9 materials (300-1670 K) showed that the room temperature Pbnm orthorhombic symmetry seems to be stable up to 1475 K; and irreversible phase transition is observed above that temperature. © 2012 Elsevier B.V. All rights reserved.


Essehli R.,Ecole des Mines de Nantes | Essehli R.,University Mohammed Premier | El Bali B.,University Mohammed Premier | Faik A.,CIC Energigune | And 6 more authors.
Journal of Alloys and Compounds | Year: 2012

Nickel titanium oxyphosphate Ni 0.5TiOPO 4 (NTP), was prepared by co-precipitation route. Its structure was determined by single crystal X-ray diffraction. The compound crystallizes in the monoclinic system, S.G: P2 1/c [a = 7.333(1), b = 7.316(2), c = 7.339(2), β = 119.62(3)°, Z = 4, R 1 = 0.0142, wR 2 = 0.0429]. The structure might be described as a {TiOPO 4} framework made of corner-sharing [TiO 6] octahedra chains running parallel to [0 0 1] and cross linked by phosphate [PO 4] tetrahedral, where half of octahedral cavities created are occupied by Ni atoms, and the other half of octahedral sites are vacant. During the first discharge, the NTP electrode delivered a capacity of 530 mAh/g, upon cycling within 0.5-4 V. To understand the electrochemical reaction mechanism using different characterization techniques viz. in situ synchrotron diffraction. Reciprocal magnetic susceptibility (χ -1) of NTP, between 4 and 300 K, shows an almost linear behavior and can be fitted by the simple Curie-Weiss law. © 2012 Elsevier B.V. All rights reserved.


Boujnah M.,Mohammed V University | Labrim H.,National Center for Energy | Allam K.,Laboratoire Of Chimie Des Materiaux Solides | Belhaj A.,National Center for Energy | And 6 more authors.
Journal of Superconductivity and Novel Magnetism | Year: 2013

Using the Korringa-Kohn-Rostoker Coherent Potential Approximation (KKR-CPA) method in connection with the Generalized Gradient Approximation (GGA), we study the magnetic and electronic properties of different point defects in cubic ZrO2. In particular, we discuss the zirconium interstitial (Zr i), zirconium antisite (ZrO), zirconium vacancy (V Zr), oxygen interstitial (Oi), oxygen antisite (O Zr), and oxygen vacancy (VO) defects. It has been shown that oxygen vacancy and zirconium interstitial (VO, Zri) are n-type, while the other point defects are p-type. The magnetic moments are observed only in the oxygen interstitial and antisite (Oi, O Zr) cases. The corresponding ferromagnetic states are more stable than the spin-glass states. It has been found that the mechanism responsible of such stabilities is the double exchange. Based on Mean Field Approximation (MFA), the Curie temperature (TC ) is estimated. Moreover, it has been found that the Oi and OZr defects provide half-metallic properties being the responsible for ferromagnetism. © 2012 Springer Science+Business Media New York.


El Hafid H.,CNRS Laboratory of Condensed Matter Chemistry, Bordeaux | Velazquez M.,CNRS Laboratory of Condensed Matter Chemistry, Bordeaux | Perez O.,CNRS Crystallography and Material Science Laboratory | El Jazouli A.,Laboratoire Of Chimie Des Materiaux Solides | And 5 more authors.
Journal of Solid State Chemistry | Year: 2013

The PbFe3O(PO4)3 powder compound was studied by means of X-ray diffraction (XRD) from 300 to 6 K, electron-probe microanalysis (EPMA) coupled with wavelength dispersion spectroscopy (WDS), calorimetric (DSC and specific heat) and magnetic properties measurements. Magnetization, magnetic susceptibility and specific heat measurements carried out on PbFe3O(PO4)3 powders firmly establish a series of three ferromagnetic (FM)-like second order phase transitions spanned over the 32-8 K temperature range. Discrepancies between magnetization and specific heat data obtained in PbFe3O(PO4)3 powders and single crystals are highlighted. A first extraction of the critical exponents (β,γ,δ) was performed by ac magnetic susceptibility in both PbFe3O(PO4)3 powders and single crystals and the values were found to be consistent with mean-field theory. Further exploration of the PbO-Fe2O3-P2O 5 system led to the discovery of a new langbeinite phase, Pb 1.5Fe2(PO4)3, the crystal structure of which was solved by room temperature single crystal XRD (P213, Z=4, a=9.7831(2) Å). This phase does not undergo any structural phase transition down to 6 K nor any kind of long range ordering down to 2 K. © 2013 Elsevier Inc.


Bih L.,British Petroleum | Bih H.,British Petroleum | Amalhay M.,Direction Recherche and Developpement | Mossadik H.,Direction Recherche and Developpement | And 4 more authors.
Procedia Engineering | Year: 2014

As the increasing demands of compact and space-saving electronics, capacitors with high energy-storage density are eagerly desired. One of the greatest challenges in the development of new high energy density materials is to increase dielectric permittivity. In this present work, we present some first results relative to phosphate glasses, which could be used as the dielectric energy-storage materials to fabricate high energy density devices. They were prepared by means of rapid quenching method. DTA and X-ray diffraction analysis were used to control their vitreous states. Dielectric constant of the glasses was measured at the frequency from 1Hz to 1MHz under the testing temperature from 120 K to 360 K. The results indicated that some samples exhibit high dielectric properties. © 2014 The Authors.


El Bouari A.,Laboratoire Of Chimie Des Materiaux Solides | El Jazouli A.,Laboratoire Of Chimie Des Materiaux Solides | Benmokhtar S.,Laboratoire Of Chimie Des Materiaux Solides | Ravereau P.,CNRS Laboratory of Condensed Matter Chemistry, Bordeaux | Wattiaux A.,CNRS Laboratory of Condensed Matter Chemistry, Bordeaux
Journal of Alloys and Compounds | Year: 2010

The phosphate Na2FeSn(PO4)3, obtained by solid state reaction, was found to be isotypic with Na2CrTi(PO 4)3, with space group R-3c and unit cell parameters a = 8.6617(2)Å, c = 22.0161(7)Å, V = 1430.47(5)Å3, Z =6. The structural parameters refined using Rietveld method showed that the Na+ ions occupy totally the M1 sites and partially the M2 sites and sharing faces with the [Sn/FeO6] octahedra. The presence of the unique valence of ferric iron in the reported phosphate was confirmed using UV-visible diffuse-reflectance spectroscopy, magnetic measurements and Mossbauer spectroscopy. © 2010 Elsevier B.V. All rights reserved.


El Hafid H.,CNRS Laboratory of Condensed Matter Chemistry, Bordeaux | Velazquez M.,CNRS Laboratory of Condensed Matter Chemistry, Bordeaux | Perez O.,CNRS Crystallography and Material Science Laboratory | El Jazouli A.,Laboratoire Of Chimie Des Materiaux Solides | And 5 more authors.
European Journal of Inorganic Chemistry | Year: 2011

A new oxyphosphate, PbFe3O(PO4)3, has been discovered and its structure has been characterized by single-crystal XRD between 293 and 973 K (monoclinic, space groupP21/m, a = 7.5826 Å, b = 6.3759 Å, c = 10.4245 Å, β = 99.956°, Z = 2, at r.t.). Direct-current (DC) magnetic susceptibility and specific heat measurements performed on single crystals revealed an unusual sequence of second-order ferromagnetic-like phase transitions at Tc1 = 31.8 K, Tc2 = 23.4 K and Tc3 â 10 K. Alternating-current (AC) magnetic susceptibility measurements suggest glass-like dynamics between ca. 20 K and Tc3. A new oxyphosphate, PbFe3O(PO4)3, has been discovered and its structure has been characterized by single-crystal XRD. Direct-current (DC) magnetic susceptibility and specific heat measurements performed on single crystals revealed an unusual sequence of second-order ferromagnetic-like phase transitions. Alternating-current (AC) magnetic susceptibility measurements suggest glass-like dynamics. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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