Tailoring calcination products for enhanced densification of Li7La3Zr2O12 ceramics

Abstract

The densification of Ga-doped Li7La3Zr2O12 (LLZO) ceramics was optimized by controlling the phase chemistry and morphology of green powders after calcination. A solution-based approach was used to synthesize the green powders which were calcined at temperatures between 600 °C and 950 °C and free-sintered into dense pellets. The ionic conductivity and relative density were optimized at a calcination temperature of 700 °C to be 1.28×10−3 S/cm and 96.2%, respectively. At this condition, the green powder consisted primarily of La2Zr2O7 pyrochlore nanoparticles (80–100 nm) and LLZO particles (0.5–1 µm), which promoted reaction-driven densification and enabled a favorable bimodal size distribution for improved packing density. Further increasing the calcination temperature was correlated with a reduction in density due to the detrimental effects of particle coarsening on sintering activity. These findings show that controlling the calcination conditions is an effective method for tailoring green body properties for improved densification of LLZO.