Synthesis and structural characterisation of the Li ion conducting garnet-related systems, Li6ALa2Nb2O12 (A = Ca, Sr)

In this paper we report structural data for the Li ion conducting garnet-related systems, Li6ALa2Nb2O12 (A = Ca, Sr). For both systems, the cell is cubic, space group Ia–3d, with the Li ions located in two partially occupied crystallographic sites, Li1 and Li2. High temperature studies for the A = Sr system show an increased occupancy of the Li2 site at higher temperatures. Both samples have high Li ion conductivity in agreement with previous results, and quenching the samples from elevated temperatures leads to an enhancement in the room temperature conductivity, which may be related to either increased occupancy of the Li2 site or reduced Li ion defect clustering/alkaline earth dopant-defect association in the quenched sample.