Browsing by Author "Alghamdi, MM"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Synthesis, electrical properties and Na+ migration pathways of Na2CuP1.5As0.5O7
    (MDPI, 2020-03-06) ALQarni, OSA; Marzouki, R; Ben Smida, Y; Alghamdi, MM; Avdeev, M; Belhadj Tahar, R; Zid, MF
    A new member of sodium metal diphosphate-diarsenate, Na2CuP1.5As0.5O7, was synthesized as polycrystalline powder by a solid-state route. X-ray diffraction followed by Rietveld refinement show that the studied material, isostructural with β-Na2CuP2O7, crystallizes in the monoclinic system of the C2/c space group with the unit cell parameters a = 14.798(2) Å; b = 5.729(3) Å; c = 8.075(2) Å; β = 115.00(3)°. The structure of the studied material is formed by Cu2P4O15 groups connected via oxygen atoms that results in infinite chains, wavy saw-toothed along the [001] direction, with Na+ ions located in the inter-chain space. Thermal study using DSC analysis shows that the studied material is stable up to the melting point at 688 °C. The electrical investigation, using impedance spectroscopy in the 260–380 °C temperature range, shows that the Na2CuP1.5As0.5O7 compound is a fast-ion conductor with σ350 °C = 2.28 10−5 Scm−1 and Ea = 0.6 eV. Na+ ions pathways simulation using bond-valence site energy (BVSE) supports the fast three-dimensional mobility of the sodium cations in the inter-chain space. © MDPI
  • No Thumbnail Available
    Item
    Synthesis, structure and Na+ migration pathways of new Wylleite-type Na1.25Co2.187Al1.125(AsO4)3
    (IOP Publishing, 2019-12-04) Marzouki, R; Ben Smida, Y; Avdeev, M; Alghamdi, MM; Zid, MF
    A new sodium cobalt (II) aluminum arsenate Na1.25Co2.187Al1.125(AsO4)3 has been synthesized by solid state reaction method and its structure has been determined by single crystal X-ray diffraction at room temperature. The title material crystallizes in the monoclinic system, space group P21/c with the unit cell parameters: a = 6.532(2) Å, b = 12.492(2) Å, c = 11.060(2) Å, β = 99.44 (2)°, V = 890.3(3) Å3 and Z = 4. The peculiarity of this structure is the Al3+ and Co2+ distribution over four crystallographic independent sites. Charge distribution (CHARDI) calculations and bond-valence sum (BVS) analysis were used to support the proposed structural model. The crystal structure of the title compound features a 3D anionic framework built of corner-edge sharing (Al3+/Co2+)O6 and AsO4 polyhedra, with interconnecting channels where the Na+ cations are located. The title compound is a new member of Wylleite family with an additional new Na+ site denoted X(3). The modelling of pathways transport of Na+ in the anionic framework shows that only the sodium Na1 can diffuse through an infinite 1D pathway along [100] direction. The empirical activation energy deduced from the Bond-Valence Site Energy (BVSE) model is about 5.45 eV. © 2019 IOP Publishing Ltd