Details

Autor(en) / Beteiligte

• Lacorre, Philippe
• Pautonnier, Antoine
• Coste, Sandrine
• Barré, Maud
• Béchade, Emilie
• Suard, Emmanuelle

Titel

Cationic Order–Disorder in Double Scheelite Type Oxides: the Case Study of Fergusonite La2SiMoO8

Ist Teil von

• Inorganic chemistry, 2021-02, Vol.60 (4), p.2623-2633

Ort / Verlag

American Chemical Society

Erscheinungsjahr

2021

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Up to now, the possible occurrence of a cationic ordering on the tetrahedral sublattices of stoichiometric double scheelite-type oxides was not settled, with somewhat contradictory X-ray diffraction and optical measurements [Blasse, G. J. Inorg. Nucl. Chem. 1968, 30, 2091]. Using two different synthesis routes, both ordered and disordered forms of fergusonite La2SiMoO8 were prepared. The crystal structure of the ordered form was determined using powder X-ray and neutron diffraction, which clearly evidence a tridimensional ordering between [SiO4] and [MoO4] tetrahedra. The crystal chemistry of ordered double sheelite-type LaIII 2(SiIVO4)­(MoVIO4) can be seen as an intermediate between those of simple regular scheelite or fergusonite LnIII(NbVO4) and of ordered triple scheelite BiIII 3(FeIIIO4)­(MoVIO4)2. The structure of the disordered La2SiMoO8 phase was analyzed using powder X-ray diffraction. A few small and larger diffraction peaks or bumps are observed in addition to the sharper peaks of a simple fergusonite cell. DIFFaX and FAULTS programs helped showing that these faint peaks originate from stacking faults between 2D ordered layers. The intermediate 2D–3D nature of SiO4/MoO4 ordering in seemingly disordered compounds might explain the previous discrepancy between optical and X-ray diffraction measurements.