The tetragonal to cubic phase transition is readily noticeable in the VT-XRD patterns via the coalescence of the split peaks into sharp, singular peaks. Data were collected in 50°C increments (50°C -1000°C), but were plotted every 100°C for clarity, see figure . Near the phase change temperature patterns were commonly biphasic (cubic and tetragonal phases present) and not used for structure refinements. Rietveld refinements were performed for all other XRD patterns with cell volume, cell parameters and A/B site bond lengths studied. An exemplar refinement (with tabulated data at each temperature) for LLZO is shown in figure and table 1. Although these data were collected for all nine Li7 phases, only LLZO is shown in detail, whereas table shows the relevant data for the other eight phases only at room temperature and the transition temperature. Table and Cell volume increased with temperature (table ), as expected, across all the studied Li7-garnets. This increase in cell volume coupled with the increasing importance of entropic stabilisation helps to promote disorder and drives the phase transition from tetragonal to cubic. Two distinct phase transitions were observed in all studied garnets, one ~100°C and a second at higher temperature. The phase transition at ~100°C was attributed to H + /Li + exchange, as it was not possible to completely eliminate moisture. The second transition at much higher temperatures is attributed to the true tetragonal-cubic phase transition.