The doping effect of Si, In and Ge in Li 7 La 3 Zr 2 O 12 (LLZ) as the solid electrolyte was studied via conventional solid-state reaction. The crystal structure, cross-sectional morphology, element distribution and conductivity were characterized for the undoped and doped LLZ ceramics. Our results showed that Si and In doping deteriorate electrical properties of LLZ as electrolyte, while Ge doping obviously improves properties. Ge might thus be a promising element for further increasing the ionic conductivity of LLZ ceramics.
Strontium doped lithium ion garnets Li 7 La 3 Zr 2 O 12 (LLZ) with 0.9 wt% to 8.4 wt% content of added Sr were synthesized via conventional solid-state reaction. X-ray diffraction patterns confirmed the cubic garnet structure of the sintered samples. A small amount of strontium was substituted to lanthanum in LLZ lattice. Further analysis showed SrCO 3 acted as a sintering aid for cubic LLZ ceramics and significantly increased the grain size of the sintered pellets. A conductivity of 2.10 × 10 − 4 S/cm at 297 K was obtained for the undoped LLZ. The total ionic conductivity reached a maximum of about 5 × 10 − 4 S/cm at 297 K with an activation energy of about 0.31 eV for 1.7 wt% Sr added LLZ sintered for 20–24 h in alumina crucible.