Mg₅TiO₄(BO₃)₂

Single crystals of penta-magnesium titanium(IV) tetra-oxide bis-(borate), Mg5TiO₄(BO₃)₂, were prepared by slow cooling of the melt from 1623 K in air. The crystal is isostructural with the mineral ludwigite (Mg2FeO₂BO₃). The Mg and Ti atoms are coordinated by six O atoms and the B atom is coordinated by three O atoms. There are three Mg sites and one mixed site statistically occupied by Mg and Ti atoms. Atoms are at the following special positions: 2a (0, 0, 0) and 2d (0, 1/2, 1/2) for two Mg atoms, 4g (x, y, 0) for the mixed Ti/Mg site and the BO₃ group, and 4h (x, y, ) for a third Mg and two oxide O atoms. MgO₆ and (Ti/Mg)O₆ octa-hedra are connected by sharing of edges to form zigzag folding layers along the c axis. Triangular prismatic tunnels are formed between the folding layers by sharing apical O atoms of the MgO₆ and (Ti/Mg)O₆ octa-hedra.