Identification of the Li sites in the Li ion conductor, Li 6SrLa 2Nb 2O 12, through neutron powder diffraction studies

Abstract

In this paper a neutron powder diffraction structural study of the Li ion conducting garnet-related system, Li 6SrLa 2Nb 2O 12, is reported. The results show that this phase is cubic, space group I a - 3 d , and contains Li in two partially occupied crystallographic sites. The first site, Li1, corresponds to the ideal tetrahedral site in the garnet framework and possesses an occupancy of 0.59(1). The second site, Li2, is significantly more distorted and possesses an occupancy of 0.352(3). Compared to the related Li 5La 3Nb 2O 12 system, the Li2 site occupancy is greatly increased, while the Li1 site occupancy is reduced. Despite these large differences in site occupancies, the reported conductivities for Li 5La 3Nb 2O 12 and Li 6SrLa 2Nb 2O 12 are similar, showing the complexities of these new garnet Li ion conductors.