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 Li ₆La₃ZrMO₁₂. Refinement of the neutron diffraction pattern of Li₆La₃SnMO₁₂ 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 0.42x 10^-4 S cm^-1.