Cubic garnets of composition Li6.75La3Zr1.75Ta0.25O12. Li6.15La3Zr1.75Ta0.25Al0.2O12, and Li6.15La3Zr1.75Ta0.25Ga0.2O12 were prepared from a co-precipitated precursor and consolidated by hot-pressing to a relative density of similar to 96-98%. The total Li-ion conductivities at 298 K and activation energies (in parentheses) of Li6.75La3Zr1.75Ta0.25O12. Li6.15La3Zr1.75Ta0.25Al0.2O12 and Li6.15La3Zr1.75Ta0.25Ga0.2O12 were 0.87 mS cm(-1) (0.22 eV), 0.37 mS cm(-1) (0.30 eV) and 0.41 mS cm(-1) (0.27 eV), respectively. The above results suggest that cubic stabilizing substitutions outside of the Li-ion sub-lattice are preferable to obtain faster Li-ion conductivity. Published by Elsevier B.V.