Sol-gel synthesis and lithium ion conductivity of Li7La3Zr2O12 with garnet-related type structure

Lithium ion conducting garnet-related type Li7La3Zr2O12 (LLZO) nanopowders were prepared by the modified sol-gel Pechini method from the stoichiometric mixtures of lithium carbonate, lanthanum oxide and zirconium ethoxide. The LLZO precursor powders were annealed at various temperatures between 923 and 1173 K for 5 h in air atmosphere. The products were characterized by thermal analysis (TG/DTA) and X-ray powder diffraction (XRPD) to verify the transformation from precursor powder to crystalline garnet-related phase. XRPD analysis shows that cubic phase of garnet-related type Li7La3Zr2O12 is formed at 978 K and the tetragonal garnet-related phase above 997 K. The morphology of the particles was investigated by Scanning Electron Microscopy (SEM). The lithium ionic conductivity of the tetragonal Li7La3Zr2O12 sample prepared by sol-gel synthesis method is found to be 3.12 x 10(-7) S/cm at 298 K while the corresponding activation energy is 0.67 eV. The results of the ionic conductivities are in good agreement with those of the tetragonal LLZO synthesized by conventional solid-state synthesis method. (c) 2011 Elsevier B.V. All rights reserved.