Synthèse et étude structrale de lyonsite-type (Na0,4,Li0,6)(Fe,Li2)(MoO4)3

Abstract

The new compound (Na0.4,Li0.6)(Fe,Li2)(MoO4)3 was synthesized by cooling from the melt. Its anionic framework is built up from two distinct MO6 octahedra, each containing disordered Li+ and Fe3+ ions in 0.6:0.4 and 0.7:0.3 ratios, and two MoO4 tetrahedra, which link by vertex-sharing of their O atoms. These tetrameric units are further linked by sharing edges between octahedra and by formation of M—O—Mo (M = Fe/Li) bridges, forming ribbons propagating in the [100] direction. The ribbons are cross-linked in both the b- and c-axis directions, giving rise to a three-dimensional framework having [100] tunnels in which the monovalent Na+/Li+ cations (0.4:0.6 ratio) lie. Bond-valence calculations are consistent with the disorder model for the cations. The structure of the title compound, which is isotypic with Li3Fe(MoO4)3 and Li3Ga(MoO4)3, is compared briefly with those of LiFeMo2O8 and Li1.6Mn2.2(MoO4)3.

Keywords

• crystal structure
• lyonsite-type
• monovalent cation molybdate
• bond-valence calculations