Preparation of a Li7La3Zr1.5Nb0.5O12 Garnet Solid Electrolyte Ceramic by using Sol-gel Powder Synthesis and Hot Pressing and Its Characterization

In this study, we prepared and characterized Nb-doped Li7La3Zr2-xO12 (LLZNO) powder and pellets with a cubic garnet structure by using a modified sol-gel synthesis and hot pressing. LLZNO powder with a very small grain size and cubic structure without secondary phases could be obtained by using a synthesis method in which Li and La sources in a propanol solvent were mixed together with Zr and Nb sources in 2-methoxy ethanol. A pure cubic phase LLZNO pellet could be fabricated from the prepared LLZNO and an additional 6-wt% of Li2CO3 powder by hot pressing at 1050 degrees C and 15.8 MPa. The hot-pressed LLZNO pellet with a relative density of 99% exhibited a very dense surface morphology. The total Li ionic conductivity of the hot-pressed LLZNO was 7.4 x 10 (-4) S/cm at room temperature, which is very high level compared to other reported values. The activation energy for ionic conduction was estimated to be 0.40 eV.