Crystallization of starting powders of LLZO induced by attrition milling

Attrition milling was used to treat the starting powders of lithium-ion conductor Li_6·4Ga_0·2La₃Zr₂O₁₂ (LLZO), which was prepared via solid-state reaction, in this study. The milling durations varied from 0 to 96 h and all the milled powders were then thermally treated at 850°C for 4 h. For the powders that had been milled for less than 96 h, only lanthanum zirconate (La₂ZrO₇) and lithium oxide (Li₂O) formed. After being milled for 96 h, a cubic LLZO phase developed in the milled powders, which indicates that appropriate attrition milling is capable of inducing the formation of a cubic garnet phase at a low temperature of 850°C, which was much lower than the reported values in the literature (i.e. 1230°C). The total conductivity of the sample made from 96 h-milled powders was the highest and its activation energy was the lowest, which indicates that crystallization prior to pelletizing could boost ionic transport in the sintered lithium-ion conductor of LLZO.