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Rare-earth sodium- and fluorine-substituted molybdates with the Na0.65La4.35Mo3O15.81±δF0.07±ε composition were synthesized for the first time as single crystals. An accurate X-ray diffraction analysis of three samples at room temperature showed that the obtained crystals are isostructural to undoped cubic compounds of the Ln5Mo3O16+δ family (space group Pn 3 ¯ n). Sodium cations partially occupy one of the two lanthanum positions and center the more distorted LaO8 polyhedra, while fluorine anions occupy over-stoichiometric oxygen positions in the vast interstices (cavities) of the structure. The partial substitution of fluorine atoms for oxygen ones affects the transport characteristics of compounds by activating the oxygen atoms in the anionic subsystem due to the effect of supplementary electrostatic repulsion between anions of different types. [ABSTRACT FROM AUTHOR]

Rare-earth fluorine-containing molybdates of the Ln5Mo3O16+δ oxygen–electron conductor family with the LiLa4Mo3O15F composition were synthesized for the first time as single crystals by the flux method. An accurate X-ray diffraction analysis of the obtained crystals was carried out at 20 and −183 °C. The LiLa4Mo3O15F compound is isostructural to the fluorine-free analogue with a cubic structure (space group Pn 3 ¯ n). It is shown that lithium atoms replace one of the two positions of lanthanum in the more distorted LaO8 polyhedron. According to X-ray diffraction analysis, fluorine atoms replace the positions of over-stoichiometric oxygen located in the vast cavities of the structure. So, fluorine anions can promote the interstitial conductivity of F-containing LiLa4Mo3O15F molybdates. [ABSTRACT FROM AUTHOR]

Undoped and Mg‐doped Pr2MoO6 oxymolybdate polycrystals and single crystals have been prepared by solid‐state reactions and flux growth. The compounds have been characterized by powder X‐ray diffraction, energy‐dispersive spectroscopy, inductively coupled plasma mass spectrometry, scanning transmission electron microscopy, single crystal X‐ray structure analysis, differential scanning calorimetry and thermogravimetry. The (MgO)x(Pr2O3)y(MoO3)z (x + y + z = 1) solid solution series has been shown to extend to x = 0.03. The structure of the Mg‐doped Pr2MoO6 single crystals can be represented as superimposed lattices of the main matrix (Pr2MoO6) and lattices in which Mo atoms are partially replaced by Mg. The incorporation of Mg atoms into the structure of Pr2MoO6 results in the disordering of the praseodymium and oxygen lattices. Both the polycrystalline and single‐crystal Mg‐doped samples are hygroscopic. [ABSTRACT FROM AUTHOR]