Sol–gel synthesis and electrical properties of Li5La3Ta2O12 lithium ionic conductors

Nanocrystalline Li5La3Ta2O12 powders were prepared by sol–gel method, in which acetic lithium, tantalum ethoxide, and lanthanum nitrate were used as starting materials, while ethylene glycol was used as solvent and acetic acid was used to control the pH value. Pure garnet-like Li5La3Ta2O12 powders with particle size of 100–200 nm were obtained after heating the gel precursor at 973 K for 5 h. The calcination temperature is nearly 250 K lower than that by the solid state reaction method, which would help to avoid the volatilization of lithium at high temperatures. The total conductivity at room temperature of a bulk Li5La3Ta2O12 sample sintered at 1173 K for 5 h from the sol–gel prepared powders was about 1.54 × 10− 6 S/cm and the corresponding activation energy of conductivity was about 0.57 eV, which are comparable with the results of the bulk Li5La3Ta2O12 synthesized by the solid state reaction method.