Li3Al(MoO4)3, a lyonsite molybdate

Abstract

Trilithium aluminium trimolybdate(VI), Li3Al(MoO4)3, has been grown as single crystals from α-Al2O3and MoO3in an Li2MoO4flux at 998 K. This compound is an example of the well known lyonsite structure type, the general formula of which can be written asA16B12O48. Because this structure can accomodate cationic mixing as well as cationic vacancies, a wide range of chemical compositions can adopt this structure type. This has led to instances in the literature where membership in the lyonsite family has been overlooked when assigning the structure type to novel compounds. In the title compound, there are two octahedral sites with substitutional disorder between Li+and Al3+, as well as a trigonal prismatic site fully occupied by Li+. The (Li,Al)O6octahedra and LiO6trigonal prisms are linked to form hexagonal tunnels along the [100] axis. These polyhedra are connected by isolated MoO4tetrahedra. Infinite chains of face-sharing (Li,Al)O6octahedra extend through the centers of the tunnels. A mixed Li/Al site, an Li, an Mo, and two O atoms are located on mirror planes.