Al-doped Li7La3Zr2O12 synthesized by a polymerized complex method

Abstract Li 7 La 3 Zr 2 O 12 electrolytes doped with different amounts of Al (0, 0.2, 0.7, 1.2, and 2.5 wt.%) were prepared by a polymerized complex (Pechini) method. The influence of aluminum on the structure and conductivity of Li 7 La 3 Zr 2 O 12 were investigated by X-ray diffraction (XRD), impedance spectroscopy, scanning electron microscopy (SEM), and thermal dilatometry. It was found that even a small amount of Al (e.g. 0.2 wt.%) added to Li 7 La 3 Zr 2 O 12 can greatly accelerate densification during the sintering process. SEM micrographs showed the existence of a liquid phase introduced by Al additions which led to the enhanced sintering rate. The addition of Al also stabilized the higher conductivity cubic form of Li 7 La 3 Zr 2 O 12 rather than the less conductive tetragonal form. The combination of these two beneficial effects of Al enabled greatly reduced sintering times for preparation of highly conductive Li 7 La 3 Zr 2 O 12 electrolyte. With optimal additions of Al (e.g. 1.2 wt.%), Li 7 La 3 Zr 2 O 12 electrolyte sintered at 1200 °C for only 6 h showed an ionic conductivity of 2.0 × 10 −4 S cm −1 at room temperature.