Synthesis of garnet-type Li7 − xLa3Zr2O12 − 1/2x and its stability in aqueous solutions

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 × 10−4 and 1.39 × 10− 4 S cm−1 at 25 °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 °C for one week. Elemental analysis confirmed that the chemical compositions of the cubic and tetragonal phases were Li6La3Zr2O11.5 and Li7La3Zr2O12, respectively.