Synthesis and characterization of highly conductive Ga/Y co-doped LLZO by facile combustion sol-gel method

Abstract

In this study, garnet material with the composition of Li6.4Ga0.2La3Zr(2-x)YxO12(x = 0,0.1,0.3,0.5) were synthesized by combustion sol-gel method. Phase evolution were studied by X-ray diffraction analysis and Raman. The microstructure and ionic conductivity were investigated by scanning electron microscopy and electrochemical impedance spectroscopy, respectively. Yttrium showed to be effective for promoting Densification while it did not affect the stability of cubic phase structure. However, high amounts of yttrium resulted in the formation of a secondary phase. Adding yttrium also caused microstructural grain growth. Maximum ionic conductivity (1.04 mS.cm−1 at 25 °C) was obtained in Li6.4Ga0.2La3Zr1.7Y0.3O12 sample with relative density of 96.6%. Compared to other reports with similar densities and ionic conductivities, lower sintering temperature and holding time were used in this work. This could be attributed to the effectivity of Ga/Y to promote sintering. Moreover, it may be originated from the good sinterability of combustion sol-gel synthesized powders. This synthesis method's reduced energy and time make it considerable for large-scale production.