X-ray absorption near-edge spectroscopy study on Ge-doped Li7La3Zr2O12: enhanced ionic conductivity and defect chemistry

Ge-doped Li7La3Zr2O12 (LLZ) is prepared via the conventional solid-state reaction. Our results showed that doping Ge of less than 1 wt% could stabilize the cubic phase of garnet-type LLZ and also increase its ionic conductivity up to 8.28 × 10−4 S/cm at room temperature. When the content of Ge dopant is higher, GeO2 impurity phase would appear and there coexists cubic and tetragonal mixed structures, lowering the conductivity. By combining X-ray absorption near-edge spectroscopy and full multiple-scattering theory, we find that Ge more likely enters into the Li and La crystallographic sites instead of the Zr site, which provides understanding of the micro-structural modulation by Ge dopants and the subsequent enhancement in the ionic conductivity.