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  • 1. Azdouz, M
    et al.
    Manoun, B
    Azrour, M
    Bih, L
    El Ammari, L
    Benmokhtar, S
    Lazor, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Synthesis, Rietveld refinements and Raman spectroscopy studies of the solid solution Na1-xKxPb4(VO4)(3) (0 <= x <= 1)2010In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 963, no 2-3, p. 258-266Article in journal (Refereed)
    Abstract [en]

    In the present study we report the synthesis, crystal structure and Raman spectroscopy studies of Na1-xKxPb4(VO4)(3) orthovanaclates solid solutions (0 <= x <= 1). Rielveld refinements showed that this solid solution is continuous adopting P6(3)/m (no. 176) space group. Some of Pb(II) cations are located in the (6 h) sites. The ninefold coordination sites (4f) are equally occupied by the other lead cations and the K+ and Na+ monovalent ions. The structure can be described as built up from [VO4](3-) tetrahedral and Ph2+ of sixfold coordination cavities (6 h positions), which delimit void hexagonal tunnels running along [0 0 1]. These tunnels are connected by cations of mixed sites (4f) half occupied by Pb(II) and half by Na+/K+ mixed cations. The existence of this type of lacunar apatite seems to be conditioned by the presence of lone pair cations Pb(II). Raman spectra of all the compositions are similar and show some linear shifts in band positions as a function of the composition toward high values due the substitutions of Na+ by K+ with a larger radius. No considerable changes in the temperature dependence of the Raman modes and the corresponding FWHM are observed and thus no temperature induced phase transition is observed in Na0.5K0.5Pb4(VO4)(3) up to 650 K.

  • 2.
    Behzadi, Hadi
    et al.
    Kharazmi Univ, Fac Chem, Dept Phys Chem, Tehran, Iran.
    Roonasi, Payman
    Kharazmi Univ, Fac Chem, Dept Phys Chem, Tehran, Iran.
    Taghipour, Khatoon Assle
    Kharazmi Univ, Fac Chem, Dept Phys Chem, Tehran, Iran.
    van der Spoel, David
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Computational and Systems Biology.
    Manzetti, Sergio
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Computational Biology and Bioinformatics. Fjordforsk AS Inst Sci & Technol, N-6894 Midtun, Vangsnes, Norway.
    Relationship between electronic properties and drug activity of seven quinoxaline compounds: A DFT study2015In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 1091, p. 196-202Article in journal (Refereed)
    Abstract [en]

    The quantum chemical calculations at the DFT/B3LYP level of theory were carried out on seven quinoxaline compounds, which have been synthesized as anti-Mycobacterium tuberculosis agents. Three conformers were optimized for each compound and the lowest energy structure was found and used in further calculations. The electronic properties including E-HOMO, E-LUMO and related parameters as well as electron density around oxygen and nitrogen atoms were calculated for each compound. The relationship between the calculated electronic parameters and biological activity of the studied compounds were investigated. Six similar quinoxaline derivatives with possible more drug activity were suggested based on the calculated electronic descriptors. A mechanism was proposed and discussed based on the calculated electronic parameters and bond dissociation energies.

  • 3. Bensaid, H.
    et al.
    Bih, L.
    Manoun, B.
    Azrour, M.
    El Boari, A.
    Lazor, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    X-ray structure refinement of solid solution Ba2.15-xNa0.7+xNb5-xWxO15 and the investigation of the orthorhombic-tetragonal phase transition by Raman spectroscopy2011In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 988, no 1-3, p. 136-143Article in journal (Refereed)
    Abstract [en]

    Crystal structures of Ba2.15-xNa0.7+xNb5-xWxO15 (BaNaNbW) materials were investigated by X-ray diffraction and refined using the Rietveld method. It is shown that all the samples crystallize in the tungsten tetragonal bronze (TTB) like structure and form a solid solution in the range (0 ≤ x ≤ 1). To study the temperature induced phase transition in these compounds, Raman spectra were collected in situ at room pressure and elevated temperatures, up to 330°. The Raman results show strong evidence that the materials under study go through a phase transition around Te = 270 °C. The value of the transition temperature depends on the chemical composition and increases with increasing tungsten content in the materials at a linear rate. The observation of this phase transition by Raman technique is in agreement with dielectric spectroscopy anomaly.

  • 4.
    Bensaid, H.
    et al.
    LCMS, Laboratory of Chemistry of Solid Materials, Department of Chemistry, Faculty of Sciences, Ben M’Sik-Casablanca, Morocco.
    El Bouari, A.
    LCMS, Laboratory of Chemistry of Solid Materials, Department of Chemistry, Faculty of Sciences, Ben M’Sik-Casablanca, Morocco.
    Benmokhtar, S.
    LRCPGM, Research Laboratory of General Chemistry–Physics of Materials, Department of Chemistry, Faculty of Sciences, Ben M’Sik-Casablanca, Morocco.
    Manoun, B.
    LPCM, Laboratory of Physico-Chemistry of Materials, Department of Chemistry, FST Errachidia, Morocco.
    Lazor, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Bih, L.
    LPCM, Laboratory of Physico-Chemistry of Materials, Department of Chemistry, FST Errachidia, Morocco.
    New molybdate Li2Co2xNix(MoO 4) 3 (0≤x≤2) materials with a lyonsite structure: X-ray diffraction and Raman spectroscopy studies2013In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 1031, p. 152-159Article in journal (Refereed)
    Abstract [en]

    A solid solution was found to exist in the quaternary Li2O–CoO–NiO–MoO3 system between the two phases Li2Co2(MoO4)3 and Li2Ni2(MoO4)3. Both Li2Co2(MoO4)3 and Li2Ni2(MoO4)3 are isostructural with the mineral lyonsite, and substitution according to the formula Li2Co2−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.

  • 5. Bih, H.
    et al.
    Bih, L.
    Manoun, B.
    Azdouz, M.
    Benmokhtar, S.
    Lazor, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Raman spectroscopic study of the phase transitions sequence in Li3Fe2(PO4)(3) and Na3Fe2(PO4)(3) at high temperature2009In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 936, p. 147-155Article in journal (Refereed)
    Abstract [en]

    The phase transition properties of A3Fe2(PO4)3 (A = Li, Na) were studied by Raman spectroscopy. Several Raman bands change continuously in 25–400 °C temperature range, indicating a phase transition from the γ, β to the α-phase occurring at this range of temperature. Bands caused by vibrations of phosphate anion and different ions have been found. The spectra analysis reveals that the modes, located at low frequency range 100–400 cm−1, near 500 cm−1 at room temperature, are the most thermo-sensitive. In addition, the modes corresponding to bond valence stretching of (PO4) unit in the frequency region 970–1200 cm−1 show also evolution with temperature but less sensitive than the above ones. It is observed that phosphate groups show some ordering with temperature. According to our Raman study, we can state that each of the compounds LiFeP and NaFeP shows two reversible phase transformations in the temperature range studied.

  • 6. Bih, H.
    et al.
    Bih, L.
    Manoun, B.
    Azrour, M.
    Benmokhtar, S.
    Lazor, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    X-ray diffraction and vibrational Raman spectra of the Li2-xNaxCo2(MO4)3 (0<x<1.4) solid solution with a lyonsite structure2010In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 965, no 1-3, p. 7-13Article in journal (Refereed)
    Abstract [en]

    Synthesis, X-ray diffraction and Raman spectroscopy studies of Li2-xNaxCo2(MoO4) 3 (0 ≤ x ≤ 2) compositions have been investigated. These alkali-cobalt molybdates crystallize in the orthorhombic system (space group Pnma (D2h)) with a lyonsite structure (Z = 4). The cell parameters are determined by DICVOL04 software and confirmed by Rietveld refinements. The structure is formed by a framework of MoO4 tetrahedra and (Li/Na/Co)O6 octahedra, the tetrahedra provide links between sheets and columns formed by the octahedra. The structure shows that while octahedra share corners and edges in the sheets, they share faces columns. Alkali and cobalt are distributed statically in both the octahedral and trigonal prism sites. X-ray diffraction shows the presence of a solid solution in the range of compositions (0 ≤ x < 1.4). These results are in agreement with Raman studies where the spectra of all the compositions are similar and show linear shifts of the frequencies as a function of the composition toward low values due to the substitutions of Li+ by Na+ with a larger radius.

  • 7. Chen, Ruikui
    et al.
    Zhao, Guangjiu
    Yang, Xichuan
    Jiang, Xiao
    Liu, Jifeng
    Tian, Haining
    Gao, Yan
    Liu, Xien
    Han, Keli
    Sun, Mengtao
    Sun, Licheng.
    Photoinduced intramolecular charge-transfer state in thiophene-π-conjugated donor-acceptor molecules.2008In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 876, no 1-3, p. 102-109Article in journal (Refereed)
    Abstract [en]

    Novel thiophene-π-conjugated donor-acceptor mols., 5-[2-(1,2,2,4-tetramethyl-1,2,3,4-tetrahydroquinolin-6-yl)-vinyl]-thiophene-2-carbaldehyde (QTC) and (1-cyano-2-{5-[2-(1,2,2,4-tetramethyl-1,2,3,4-tetrahydroquinolin-6-yl)-vinyl]-thiophen-2-yl}-vinyl)-phosphonic acid di-Et ester (QTCP), were designed and synthesized. Combined exptl. and theor. methods were performed to investigate the photoinduced intramol. charge-transfer (ICT) processes of these compds. Steady-state absorption and fluorescence measurements in different solvents indicate the photoinduced ICT characters of QTC and QTCP. Solvent dependency of the large Stokes shifts and high dipole moment of the excited state also support the charge-transfer character of the excited state. Theor. calcns. based on time-dependent d. functional theory (TDDFT) method were performed to investigate ICT states of these compds. The results reveal that the excited states have adopted a distortion of the C=C double bond between the donor moiety and the thiophene-π-bridge. [on SciFinder(R)]

  • 8.
    El Hachmi, Abdelhadi
    et al.
    Univ Hassan 1er, LS3M, FP Khouribga, Khouribga, Morocco..
    Manoun, Bouchaib
    Univ Hassan 1er, LS3M, FP Khouribga, Khouribga, Morocco.;Mohammed VI Polytech Univ, Mat Sci & Nanoengn Dept, Ben Guerir, Morocco..
    Tamraoui, Y.
    Univ Hassan 1er, LS3M, FP Khouribga, Khouribga, Morocco.;Mohammed VI Polytech Univ, Mat Sci & Nanoengn Dept, Ben Guerir, Morocco..
    Mirinioui, F.
    Univ Hassan 1er, LS3M, FP Khouribga, Khouribga, Morocco..
    Abkar, R.
    Univ Hassan 1er, LS3M, FP Khouribga, Khouribga, Morocco..
    El Aamrani, M. A.
    Univ Hassan 1er, LS3M, FP Khouribga, Khouribga, Morocco..
    Saadoune, I.
    Mohammed VI Polytech Univ, Mat Sci & Nanoengn Dept, Ben Guerir, Morocco.;Univ Cadi Ayyad, FST Marrakech, LCME, Av A Khattabi, Marrakech 40000, Morocco..
    Sajieddine, M.
    Univ Sultan Moulay Sliman, Lab Phys & Mech Mat, Fac Sci & Tech, BP 523, Beni Mellal 23000, Morocco..
    Lazor, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Temperature induced structural phase transition in Sr3-xCaxFe2TeO9 (0 <= x <= 1) probed by Raman and Mossbauer techniques2017In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 1141, p. 484-494Article in journal (Refereed)
    Abstract [en]

    A series of perovskites Sr3-xCaxFe2TeO9 (0 <= x <= 1) have been prepared in polycrystalline form by solid-state reaction method in air. These materials have been studied by X-ray powder diffraction method (XRPD) and Raman spectroscopy. An analysis of the XRD patterns at room temperature has shown that these compounds crystallize in a tetragonal system, space group I4/m. The structure contains alternating (Fe/Te)(2a)O-6 and (Fe/Te)(2b)O-6 octahedra, tilted in anti-phase in the basal ab-plane. The study of Raman spectroscopy at various temperatures shows a transition from tetragonal to cubic phase: I4/m -> Fm (3) over bar m. This phase transition occurs at high-temperature. Analysis of Raman spectra recorded at several temperatures shows that this phase transition appears near similar to 375 degrees C for (x = 0), similar to 435 degrees C for (x = 0.5) and similar to 451 degrees C for (x = 1). A proportional and gradual increase of temperature phase transition is observed as function of the calcium amount.

  • 9. Ezzahi, A.
    et al.
    Manoun, Bouchaib
    Ider, A.
    Bih, L.
    Benmokhtar, S.
    Azrour, M.
    Azdouz, M.
    Igartua, J. M.
    Lazor, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    X-ray diffraction and Raman spectroscopy studies of BaSrMWO6 (M=Ni, Co, Mg) double perovskite oxides2011In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 985, no 2-3, p. 339-345Article in journal (Refereed)
    Abstract [en]

    In this work we report on the crystal structure and Raman spectroscopy of BaSrMWO6 (M=Ni, 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 in. 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 W-O 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.

  • 10. Henschel, Henning
    et al.
    Kloeckner, Jan-Peter
    Nicholls, Ian A.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Prosenc, Marc H.
    Computational and structural studies on the complexation of cobalt(II) acetate by water and pyridine2012In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 1007, p. 45-51Article in journal (Refereed)
    Abstract [en]

    Four different complexes of the cobalt(II) acetate-pyridine-water system were obtained as dominant species by crystallization from a series of dichloromethane and toluene solutions. The complexes were characterized by terms of X-ray crystal structure determination. Factors in solution properties leading to crystallization of certain complexes are discussed. Furthermore, trends in terms of structure and binding energies in a systematic series of mononuclear cobalt(II) complexes were studied using density functional calculations.

  • 11.
    Larsson, Karin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Tegenfeldt, Jörgen
    A Nuclear Magnetic Resonance Study of the Mobility of Water Molecules in NaHC2O4 H2O1988In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 178, p. 315-Article in journal (Refereed)
  • 12.
    Larsson, Karin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Tegenfeldt, Jörgen
    An NMR Study of the Moelcular Mobility in BeSO4 4H2O1988In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 176, p. 303-Article in journal (Refereed)
  • 13. Majerz, Irena
    et al.
    Olovsson, Ivar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Influence of proton transfer on the geometry of the donor and acceptor in NHN+ hydrogen bonds2010In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 976, no 1-3, p. 11-18Article in journal (Refereed)
    Abstract [en]

    The correlation between distances X-H and H-Y in hydrogen bonds has been studied extensively but it is difficult to determine experimentally individual changes in the internal structure of the molecules involved in the hydrogen bonds. In the present study the influence of proton transfer on the geometry of donors and acceptors in NHN+ hydrogen bonds has been investigated by theoretical calculations at the B3LYP/6-31++G** level of theory using the Gaussian03 system. The selected compounds provide examples of both inter- and intramolecular hydrogen bonds. Typically, the largest changes are in the bonds involving the closest neighbors to the NHN bridge atoms, but in certain cases the geometrical features of parts that are more remote from the bridge atoms are also affected, and can result in significant changes of the conformation of the molecules.

  • 14. Majerz, Irena
    et al.
    Olovsson, Ivar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    The influence of the OHO angle on the proton valency in inter- and intra-molecular hydrogen bonds2010In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 968, no 1-3, p. 48-51Article in journal (Refereed)
    Abstract [en]

    The influence of the OHO angle in the hydrogen bond on the potential-energy surface has been studied. The OHO angle has been artificially changed from 140 degrees to 180 degrees to study the influence of the angle on the location of the energy minimum relative to QMRC, the minimum energy reaction path, and BORC, the bond-order reaction path. In the intermolecular hydrogen bond QMRC and BORC are identical, independent on the OHO angle. The intramolecular hydrogen bond is very sensitive to a change in the OHO angle. The agreement between the theoretical results is confirmed by available experimental neutron data.

  • 15. Manoun, B.
    et al.
    Azdouz, M.
    Azrour, M.
    Essehli, R.
    Benmokhtar, S.
    Ammari, L. El
    Ezzahi, A. Ider
    Lazor, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Synthesis, Rietveld refinements and Raman spectroscopic studies of tricationic lacunar apatites Na1-xKxPb4(AsO4)3 (0 ≤ x ≤ 1)2010In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 986, no 1-3, p. 1-9Article in journal (Refereed)
    Abstract [en]

    Three compounds from the solid solution of lead lacunar ionic apatites Na1−xKxPb4(AsO4)3, with x = 0, 0.5 and 1, were successfully synthesized as single phases by solid state method at 700 °C. The samples were characterized by X-ray diffraction, the site of the metal ions (Na+, K+ and Pb2+) in the solid solutions was analyzed with the Rietveld method. A variation of the a and c lattice parameters in the solid solutions was observed, with an increase of a and c parameters, related to the radius of the corresponding substituted ions. It was found that Pb(II) ions in the solid solutions preferentially occupied the M(1) and M(2) sites in the lacunar anionic apatite structure. The structure contains channels running along the c axis and centred at (0 0 z). The channels are most probably occupied by the lone electron pairs of the Pb2+ cations. Raman spectra of all the compositions are similar and show some linear shifts, especially for the bending modes, in band positions as a function of the composition toward lower values due the substitutions of Na+ by K+ with a larger radius. No considerable changes in the temperature dependence of the Raman modes and the corresponding FWHM are observed and thus no temperature induced phase transition is observed in Na0.5K0.5Pb4(AsO4)3 up to 630 K.

  • 16. Manoun, B.
    et al.
    Azdouz, M.
    Azrour, M.
    Essehli, R.
    Benmokhtar, S.
    El Ammari, L.
    Ezzahi, A.
    Ider, A.
    Lazor, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Synthesis, Rietveld refinements and Raman spectroscopic studies of tricationic lacunar apatites Na1-xKxPb4(AsO4)(3) (0 <= x <= 1)2011In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 986, no 1-3, p. 1-9Article in journal (Refereed)
    Abstract [en]

    Three compounds from the solid solution of lead lacunar ionic apatites Na1-xKxPb4(AsO4)(3), with x = 0, 0.5 and 1, were successfully synthesized as single phases by solid state method at 700 degrees C. The samples were characterized by X-ray diffraction, the site of the metal ions (Na+, K+ and Pb2+) in the solid solutions was analyzed with the Rietveld method. A variation of the a and c lattice parameters in the solid solutions was observed, with an increase of a and c parameters, related to the radius of the corresponding substituted ions. It was found that Pb(II) ions in the solid solutions preferentially occupied the M(1) and M(2) sites in the lacunar anionic apatite structure. The structure contains channels running along the c axis and centred at (0 0 z). The channels are most probably occupied by the lone electron pairs of the Pb2+ cations. Raman spectra of all the compositions are similar and show some linear shifts, especially for the bending modes, in band positions as a function of the composition toward lower values due the substitutions of Na+ by K+ with a larger radius. No considerable changes in the temperature dependence of the Raman modes and the corresponding FWHM are observed and thus no temperature induced phase transition is observed in Na0.5K0.5Pb4(AsO4)(3) up to 630 K.

  • 17.
    Manoun, B.
    et al.
    Equipe Matériaux et Environnement, Laboratoire de Chimie Appliquée et Environnement, Université Hassan 1er, Morocco.
    Igartua, J.M.
    Fisika Aplikatua II, Zientzia eta Teknologia Fak., UPV/EHU, PB 644, Bilbao 48080, Spain.
    Lazor, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Ezzahi, A.
    Equipe Matériaux et Environnement, Laboratoire de Chimie Appliquée et Environnement, Université Hassan 1er, Morocco.
    High temperature induced phase transitions in Sr2ZnWO6 and Sr2CoWO6 double perovskite oxides: Raman spectroscopy as a tool2012In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 1029, p. 81-85Article in journal (Refereed)
    Abstract [en]

    In this paper we report high-temperature (up to 550 °C) Raman spectroscopy of phase transitions in Sr2MWO6 (M = Zn, Co) double perovskite oxides. For Sr2ZnWO6 modes centered at 137 cm−1, 152 cm−1, merge around 80 °C. The same behavior was observed for the 436 cm−1 and 447 cm−1 modes. The mode centered at 854 cm−1 shows a change in the slope at the same temperature, thus indicating a first order phase transition from the monoclinic (P21/n) to tetragonal (I4/m) structure. With increasing temperature, a little change in the slope of the temperature dependence of mode centered at 855 cm−1 is observed around 480 °C which might be a sign of the second phase transition in Sr2ZnWO6 (tetragonal (I4/m) to cubic (Fm-3m)). The temperature dependence of the full width at half maximum (FWHM) of the most intense modes in Sr2ZnWO6 spectra was studied. The width behaves linearly as a function of temperature with a break observed in the slope of the width of the modes at 80 °C; thus, showing the first phase transition occurrence. For Sr2CoWO6 the transition from tetragonal (I4/m) structure to cubic (Fm-3m) phase is accompanied by considerable changes in the temperature dependence of modes centered at 438 cm−1 and 845 cm−1. The transition was observed around 420 °C.

  • 18. Manoun, Bouchaib
    et al.
    Ezzahi, A.
    Benmokhtar, S.
    Bih, L.
    Tamraoui, Y.
    Haloui, R.
    Mirinioui, F.
    Addakiri, S.
    Igartua, J. M.
    Lazor, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    X-ray diffraction and Raman spectroscopy studies of temperature and composition induced phase transitions in Ba2-xSrxMWO6 (M = Ni, Co and 0 <= x <= 2) double perovskite oxides2013In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 1045, p. 1-14Article in journal (Refereed)
    Abstract [en]

    X-ray diffraction and Raman spectroscopy studies of Sr doped double perovskites compound Ba2-xSrxMWO6 with (M = Ni, Co and 0 <= x <= 2) were investigated. The samples show a transition from cubic to tetragonal phase as a function of composition while increasing strontium amount; both Rietveld refinements and Raman studies showed that this transition occurs between x = 1.2 and 1.4. Furthermore, increasing temperature for the tetragonal compositions (1.4 <= x <= 2), manifest the tetragonal to cubic phase transition. For this series, the transition from tetragonal (I4/m)/to cubic (Fm-3m) shows considerable changes in the composition and temperature dependence of the modes: all the Raman modes show a linear behavior when temperature is increased, then the slope change dramatically indicating the symmetry change from tetragonal to cubic. To better view this phase transition, the full width at half maximum (FWHM) temperature dependence of the most intense modes were studied; by this study, we have obtained a sensitive guide to the onset of the phase transition. A large increase of the FWHM with increasing temperature is observed for all modes in the spectrum, clear transitional effects were observed: the width behaves in a linear way as a function of temperature; when the temperature reached the transition temperature, a drop in the width of this mode was observed. 

  • 19. Manoun, Bouchaib
    et al.
    Igartua, Josu M.
    Lazor, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    High Temperature Raman Spectroscopy studies of the phase transitions in Sr2NiWO6 and Sr2MgWO6 double perovskite oxides2010In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 971, no 1-3, p. 18-22Article in journal (Refereed)
    Abstract [en]

    In this paper, we report on high temperature Raman spectroscopy studies (up to 550 °C) of the phase transitions in Sr2BWO6 (B = Ni, Mg) double perovskite oxides. For both compounds, the transition from the tetragonal (I4/m) phase to the cubic (Fm-3m) phase is accompanied by considerable changes in the temperature dependence of the modes. To better view this phase transition, the FWHM temperature dependence of the most intense modes were studied; by this study, we have obtained a sensitive guide to the onset of the phase transition. A large increase of the FWHM with increasing temperature is observed for all modes in the spectrum, clear transitional effects were observed: the width behaves in a linear way as a function of temperature; when the temperature reached around 300 °C, a drop in the width of this mode was observed; thus, showing the phase transition occurrence for both compounds. This drop is much more illustrated in Ni-containing compound than in Sr2MgWO6.

  • 20.
    Tamraoui, Y.
    et al.
    Univ Hassan 1er, LS3M, Khouribga 25000, Morocco..
    Manoun, Bouchaib
    Univ Hassan 1er, LS3M, Khouribga 25000, Morocco.;Mohammed VI Polytech Univ, Ctr Adv Mat, Lot 660 Hay Moulay Rachid, Ben Guerir 43150, Morocco..
    Mirinioui, F.
    Univ Hassan 1er, LS3M, Khouribga 25000, Morocco..
    Saadoune, I.
    Mohammed VI Polytech Univ, Ctr Adv Mat, Lot 660 Hay Moulay Rachid, Ben Guerir 43150, Morocco.;Univ Cadi Ayyad, FST Marrakech, LCME, Av A Khattabi, Marrakech 40000, Morocco..
    Haloui, R.
    Univ Hassan 1er, LS3M, Khouribga 25000, Morocco..
    Elhachmi, A.
    Univ Hassan 1er, LS3M, Khouribga 25000, Morocco..
    Saad, E.
    Univ Hassan 1er, Lab Physicochim Proc & Mat PCPM, Fst Settat, Morocco..
    Lazor, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Temperature and composition induced phase transitions in Sr2-xCa1+xTeO6 (0 <= x <= 2) double perovskite oxides2017In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 1131, p. 103-113Article in journal (Refereed)
    Abstract [en]

    Structures of Sr2-xCa1+xTeO6 double perovskites have been studied by the profile analysis of X-ray diffraction data and Raman spectroscopy at room temperature. This series adopts a monoclinic symmetry for the compositions (0 <= x <= 0.5) with P2(1)/n as space group and a triclinic system with P (1) over bar space group for the compositions (0.5 < x <= 2). These results were confirmed by the observed tolerance factor calculated from the distances obtained from the Rietveld refinements which indicates that the true tilt system for the compositions range (0.5 < x <= 2) is the triclinic tilt system. Clear changes in the Raman modes centered at 600, 610 and 620 cm(-1) and the FWHM of O-Te-O bending vibrations, centered at 738 cm(-1) confirmed that the triclinic symmetry takes place between the compositions x = 0.5 and x = 1. Furthermore, Raman spectroscopy studies at high temperature were done for Ca3TeO6. For this compound, considerable changes in the temperature dependence of the modes were well illustrated.

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