Microstructure and Li‐Ion Conductivity of Hot‐Pressed Cubic Li ₇ La ₃ Zr ₂ O ₁₂

The effect of hot‐pressing temperature on the microstructure and Li‐ion transport of Al‐doped, cubic Li 7 La 3 Zr 2 O 12 ( LLZO ) was investigated. At fixed pressure (62 MPa), the relative density was 86%, 97%, and 99% when hot‐pressing at 900°C, 1000°C, and 1100°C, respectively. Electrochemical impedance spectroscopy showed that the percent grain‐boundary resistance decreased with increasing hot‐pressing temperature. Hot pressing at 1100°C resulted in a total conductivity of 0.37 mS/cm at room temperature where the grain boundaries contributed to 8% of the total resistance; one of the lowest grain‐boundary resistances reported. We believe hot pressing is an appealing technique to minimize grain‐boundary resistance and enable correlations between LLZO composition and bulk ionic conductivity.