Li6La3SnMO12(M = Sb, Nb, Ta), a Family of Lithium Garnets with High Li-Ion Conductivity

In order to investigate the influence of covalent bonding within the garnet framework on the conductivity of Li+ in the interstitial space, the Li+ conductivities in the family of Sn-based compounds Li6La3SnMO12 (M = Sb, Nb, Ta) have been obtained and are compared with those of Li6La3ZrMO12. Refinement of the neutron diffraction pattern of Li6La3SnNbO12 shows that the interstitial tetrahedral sites (24d) are about half-occupied and most of the Li in the interstitial bridging octahedral sites are displaced from the center position (48g). The Sb-based compound has the largest lattice parameter while the Ta-based compound has the highest Li+-ion conductivity of 0.42×10−4 S cm−1.