Nebulized spray pyrolysis followed by consolidation and sintering was used for the first time to prepare Al-doped garnet-based Li7−3xLa3Zr2AlxO12 (x = 0–0.25) (LLZO) ultra-fine grained ceramics. The structural changes from the tetragonal (x = 0), via a mixture of the cubic and the tetragonal (x = 0.07, 0.10) to the cubic modification (x = 0.15–0.25) were observed. 27Al NMR study showed that aluminum occupy the tetrahedral 24d lithium sites. Despite their low relative density (47–56%), preliminary ionic conductivities of the LLZO ceramics, were found to be 1.2 · 10− 6 S cm− 1 and 4.4 · 10− 6 S cm− 1 for tetragonal and cubic LLZO at room temperature, with activation energies of 0.55 eV and 0.49 eV, respectively.