Rare-Earth Fluorite-like Li0.42La4.58Mo3O15.76±δF0.42±ε Molybdates: Crystal Growth and Atomic Structure

Abstract

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 Pn3¯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.