The garnet-type cubic and tetragonal phases with respective high and low lithium ion conductivity were synthesized using precursors prepared by a sol-gel method. The electrical conductivities of the bulk and grain boundary of the cubic phase were estimated from impedance spectra to be 5.69 x 10(-4) and 1.39 x 10(-4) S cm(-1) at 25 degrees C, respectively. The garnet-type cubic phase was stable in a saturated solution of LiCl, and no changes in the XRD pattern or electrical conductivity were observed for a sample immersed in saturated LiCl solution at 50 degrees C for one week. Elemental analysis confirmed that the chemical compositions of the cubic and tetragonal phases were Li6La3Zr2O11.5 and Li7La3Zr2O12. respectively. (C) 2010 Elsevier BM. All rights reserved.