For each garnet synthesised, Rietveld refinements were performed in GSAS-II using room temperature powder X-ray diffraction (XRD) patterns and variable temperature X-ray diffraction (VTXRD) patterns (50°C to 1000°C, 50°C increments). All structural models were obtained from ISCD and atoms altered where required to give an analogous crystal structure. For Ce-doped LLZO, fractional occupancies were set to the intended ratio.