Crystal Structure and Ionic Conductivity of the NASICON-Type Lithium Ion Conducting Solid Electrolyte

The LixAlx-1Ge3-x(PO4)(3) (x=1.1 similar to 1.9) solid solutions were prepared as glass ceramics pellets. The title compounds crystallize in the NASICON (Na Super Ionic Conductor), R3c type structure, space group, and the crystal structures were characterized by the Rietveld method with laboratory powder diffraction data. The annealed glasses and glass ceramics were also characterized by DSC, FESEM and AC impedance techniques. The results indicate that the major phase of the glass ceramics is LiGe2(PO4)(3), with AlPO4 and Li4P2O7 as the side-phases for some samples. Additionally, the highest total ionic conductivity (5.3x10(-4) S.cm(-1)) at room temperature is obtained when x=1.5 for LixAlx-1Ge3-x(PO4)(3) glass ceramics, with homogeneous crystals distribution and wide electrochemical window (7.2 V).