However, these tetragonal Li garnets, such as La3Zr2Li7O12, La3Hf2Li7O12 and Nd3Zr2Li7O12 , undergo a high temperature tetragonal-cubic phase transition (~700°C), believed to arise from increased unit cell size and entropy factors . It would therefore be of great interest if this transition temperature could be lowered to room temperature, thus forming a cubic Li7 phase, which should further optimise the conductivity of Li garnets. This requires a greater understanding of the factors which influence the temperature of this phase transition, which is somewhat limited in the literature. Some studies initially thought this transition occurred ~100-200°C in LLZO but this was determined to arise from hydration, due to either the direct insertion of water molecules or through a H + /Li + exchange mechanism .