• Goudjil, Meriem

Abstract

<jats:title>Abstract</jats:title> <jats:p>A series of six new single crystals of <jats:italic>fully stoichiometric</jats:italic> As<jats:sup>3+</jats:sup>-bearing Mo-oxides and partially W-substituted Mo-oxides with formula As<jats:italic><jats:sub>m</jats:sub></jats:italic>O(Mo<jats:sub>1−</jats:sub><jats:italic><jats:sub>x</jats:sub></jats:italic>W<jats:italic><jats:sub>x</jats:sub></jats:italic>O<jats:sub>3</jats:sub>)<jats:italic><jats:sub>p</jats:sub></jats:italic> (<jats:italic>m</jats:italic> = 1, 2; <jats:italic>p</jats:italic> = 5, 7, 9, 10 and 11 and 0 ≤ <jats:italic>x</jats:italic> ≤ 0.6) was successfully grown using vapor-phase transport <jats:italic>in vacuo</jats:italic>. The crystal structures were determined using single-crystal X-ray diffraction data. All these compounds exhibit acentric orthorhombic symmetry with <jats:italic>Z</jats:italic> = 2, and belong to the so-called (<jats:italic>n</jats:italic>)-ITB (intergrowth tungsten bronzes) family, with <jats:italic>n</jats:italic> = 2, 3, 4 and 5. The six (<jats:italic>n</jats:italic>)-ITB phases have the following formulae: (2)-AsMo<jats:sub>5</jats:sub>O<jats:sub>16</jats:sub> (<jats:italic>Pm</jats:italic> 2<jats:italic>a</jats:italic>), (2)-As<jats:sub>2</jats:sub>Mo<jats:sub>10</jats:sub>O<jats:sub>31</jats:sub> (<jats:italic>Pma</jats:italic> 2), (3)-AsMo<jats:sub>7</jats:sub>O<jats:sub>22</jats:sub> (<jats:italic>Pmn</jats:italic> 2<jats:sub>1</jats:sub>), (3)-As(Mo<jats:sub>5.53</jats:sub>W<jats:sub>1.47</jats:sub>)O<jats:sub>22</jats:sub> (<jats:italic>Pmn</jats:italic> 2<jats:sub>1</jats:sub>), (4)-As(Mo<jats:sub>4.33</jats:sub>W<jats:sub>4.67</jats:sub>)O<jats:sub>28</jats:sub> (<jats:italic>Pm</jats:italic> 2<jats:italic>a</jats:italic>) and (5)-As(W<jats:sub>6.63</jats:sub>Mo<jats:sub>4.37</jats:sub>)O<jats:sub>34</jats:sub> (<jats:italic>Pmn</jats:italic> 2<jats:sub>1</jats:sub>). Their structures consist of vertex-sharing MO<jats:sub>6</jats:sub> octahedral units (with M either Mo or Mo/W) connected so as to form three-dimensional frameworks. Such frameworks consist of perovskite tungsten bronzes (PTB) type slabs, from 2- to 5-octahedra wide, intergrown with single hexagonal tungsten bronzes (HTB) type slabs, stacked up to form pseudo-hexagonal tunnels along the <jats:bold>a</jats:bold>-axis. As<jats:sup>3+</jats:sup> and additional oxygen atoms are located in off-center positions inside the tunnels, forming As–O bonds with peculiar arrangements. In particular, we obtained the first examples of structures where, besides the usual AsO<jats:sub>3</jats:sub>E distorted pyramidal geometry, As<jats:sup>3+</jats:sup> adopts AsO<jats:sub>4</jats:sub>E coordination with a <jats:italic>seesaw</jats:italic> configuration.</jats:p>

Topics

• perovskite
• compound
• molybdenum
• single crystal
• phase
• x-ray diffraction
• Oxygen
• forming
• tungsten
• bronze
• Arsenic