Investigation of Low‐Temperature Synthesis Strategy for a Cubic Phase Li7La3Zr2O12

Abstract In the present work, a solid‐state reaction (SSR) method is used to prepare a cubic phase Li 7 La 3 Zr 2 O 12 (C‐LLZO) via a two‐step process from tetragonal phase Li 7 La 3 Zr 2 O 12 (T‐LLZO). To identify the tetragonal to cubic phase change region a thermogravimetric analysis (TGA) of the precursor material is carried out. Subsequently, another TGA analysis is carried out for tetragonal sample to identify tetragonal to cubic phase transition regions. TGA of tetragonal sample shows multiple phase transition regions at ≈250°, 400°, and 610 °C. A series of T‐LLZO samples are reheated to obtain C‐LLZO. The T‐LLZO samples reheated at 150 °C, and 650 °C show cubic symmetry, whereas the sample heated at 450 °C and 950 °C show mixed phase. The obtained C‐LLZO samples have lattice constant a = b = c = 12.9389 Å for 150 °C heated sample and a = b = c = 12.9375 Å for 650 °C heated samples with space group I a‐3d. Considering the TGA of the T‐LLZO sample and XRD analysis of the T‐LLZO samples reheated at different temperatures, the transition at ≈150 °C is attributed to the hydration process of T‐LLZO and 650 °C is due to structural deformation of LLZO.