Influence of Al2O3 additions on crystallization mechanism and conductivity of Li2O–Ge2O–P2O5 glass–ceramics

The crystallization mechanism and conductivity of lithium aluminum germanium phosphate [LAGP] glass–ceramics fabricated from Li1+xAlxGe2−x(PO4)3 (x=0.0–0.7) glass system were investigated as a function of Al2O3 additions. A non-isothermal analysis was performed to study the crystallization behavior of LAGP glass–ceramics at various heating rates (5–25K min−1) by the Kissinger equation and the Augis–Bennett equation, illustrating volume crystallization for the glass-ceramics. The crystal identification and microstructure in glass–ceramics containing various Al2O3 contents were analyzed by means of XRD and FESEM. The main phase of the glass–ceramics was found to be LiGe2(PO4)3, with AlPO4 as the impurity phase. Additionally the highest total ionic conductivity (5.8×10−4 S/cm) at room temperature was obtained when x=0.5 for Li1+xAlxGe2−x(PO4)3 (x=0.0–0.7) glass–ceramics, suggesting that it was a promising electrolyte for practical application in all-solid-state lithium batteries.