Rapid low‐temperature synthesis of tetragonal single‐phase Li 7 La 3 Zr 2 O 12

The formation of Li 7 La 3 Zr 2 O 12 ( LLZ ), a Li ion conducting oxide with a garnet‐type crystal structure, from a powder mixture of Li 2 CO 3 , La( OH ) 3 , and ZrO 2 was investigated, and two possible reaction pathways were identified. Based on the obtained results, LLZ was synthesized at low temperatures and short reaction times, using Li 2 CO 3 , La( OH ) 3 , and La 2 Zr 2 O 7 (instead of ZrO 2 ) as starting materials. According to the proposed method, single‐phase LLZ was obtained by heating the initial mixture to 800°C for 1 hour in air, which eliminated possible Li losses. The produced LLZ species exhibited a tetragonal crystal structure with the lattice parameters a= 1.3189(3) nm and c= 1.2694(1) nm, while their transmission electron microscopy images confirmed that LLZ formation occurred through the dissolution of La 2 Zr 2 O 7 and La( OH ) 3 in a Li 2 CO 3 melt followed by LLZ precipitation from solution.