In 3+ in a layered arrangement (see Figure ). In this structure, Zr(IV) substitution does not lead to a phase transition . While the monoclinic structure type is less common in chlorides, similar structures are found for bromide and iodide analogues . Upon Zr-substitution, the changes in lattice parameter are small and the anionic framework remains quasi cubic-close-packed. It is therefore unlikely that the increase in ionic conductivity arises from a change in the size of the bottleneck or interaction of the Li-ions with the anionic lattice. This raises the question: To what extent is the increase in ionic conductivity on Zr(IV) substitution due to the change in charge carrier concentrations, changes in the crystal structure and/or changes in the diffusion pathway(s)?