Polycrystalline tetragonal and cubic with garnet related type structured Li7La3Zr2O12 (LLZO) has been successfully synthesized at 700 degrees C (tetragonal) and 1100 degrees C (cubic), respectively by modified polymer complex synthesis. Citric acid was used for a chelating agent and ethylene glycol was applied for polymer complex agent. Thermal analysis indicated that the crystallization has been completed at the low temperature in case of applying high energy ball-milling process. It is presumed that applied mechanochemical energy promotes the earlier crystallization at lower temperature, which induces the reduction of particle size effectively. LLZOs with tetragonal and cubic phase showed ionic conductivities of 6.2 x 10(-7) Scm(-1) and 1.4 x 10(-4) Scm(-1), respectively. Prepared LLZO powders, having relatively small size, are expected to provide the large surface area for Li-ion conducting path in the design of all solid electrodes. (C) 2016 Elsevier Ltd. All rights reserved.