Synthesis of garnet structured Li7+x La3Y x Zr2-x O12 (x = 0–0.4) by modified sol–gel method

Preparation of lithium garnet Li7La3Zr2O12 (LLZ) in cubic phase by solid state method requires high temperature sintering around 1,200 °C for 36 h in Al2O3 crucible with intermittent grinding. Synthesis of LLZ in cubic phase at lower temperatures by wet chemical methods was reported earlier, however that decompose at high temperature around 850 °C. In this work we report the systematic studies on synthesis of garnet structured electrolytes by modified sol–gel method by the simultaneous substitution of Li+ and Y3+ for Zr4+ according to the formulae Li7+x La3Y x Zr2-x O12 (x = 0, 0.1, 0.2, 0.3 and 0.4). The present investigation revealed that the cubic garnet phase is obtained at much lower temperature for Li7La3Zr2O12 and the simultaneous increase of both Li+ and Y3+ in Li7+x La3Y x Zr2-x O12 requires slightly higher sintering temperatures for the formation of cubic garnet phase. SEM micrographs of the Li7+x La3Y x Zr2-x O12 (x = 0, 0.1, 0.2, 0.3 and 0.4) annealed at minimum sintering temperature required for the formation of cubic garnet phase revealed the increase in grain size and relatively dense structure with increase of x in Li7+x La3Y x Zr2-x O12.