Synchrotron study of the garnet-type oxide Li6CaSm2Ta2O12

Abstract

Hexalithium calcium disamarium(III) ditantalum(V) dodecaoxide, Li6CaSm2Ta2O12, crystallizes in a cubic garnet-type structure. In the crystal structure, disordered Li atoms occupy two crystallographic sites. One Li has a tetrahedral coordination environment in the oxide lattice, whereas the other Li atom occupies a significantly distorted octahedral site, with site occupancies for the two Li atoms of 0.26 (7) and 0.44 (2), respectively. Ca and Sm atoms are statistically distributed over the same crystallographic position with a occupancy of 2/3 for Sm and of 1/3 for Ca, and are eightfold coordinated by O atoms. The TaO6 octahedron is joined to six others via corner-sharing LiO4 tetrahedra. One Li and the O atoms lie on general positions, while the other atoms are situated on special positions. The Sm/Ca position has 222, Ta has overline{3}, and the tetrahedrally coordinated Li atom has overline{4} site symmetry