Nitrogen-free sol-gel synthesis of Al-substituted cubic garnet Li7La3Zr2O12 (LLZO)

A nitrogen-free sol-gel synthesis of Al-substituted cubic lithium lanthanum zirconium garnet (c-LLZO) was developed. Polycrystalline powders of c-LLZO of the composition Li6.42Al0.32La3Zr1.91O12.02 were prepared from the molecular mixtures of lithium acetate, lanthanum acetate, zirconium propoxide and aluminum chloride and subsequent annealing of the dried precursor sol at 1000 °C for 7 h free of nitrogen oxide gas emissions. The obtained powders had traces of lithium zirconate (<4 wt%), an ionic conductivity of the order of 10−5 S cm−1 and showed a heterogeneous microstructure, which was assumed to result from early melt formation.