High conductivity of dense tetragonal Li7La3Zr2O12

► Highest relative density (∼98%) tetragonal Li7La3Zr2O12 reported. ► Highest total ionic conductivity of ∼2.3 × 10−5 S cm−1 reported for tetragonal Li7La3Zr2O12. ► Microstructure of dense Li7La3Zr2O12 revealed twins within the grains.