To address the safety issues related to liquid electrolyte and improve the battery performance, Solid State Electrolytes (SSEs) are now in frontier area of research interest. We report here synthesis of Li-SSE based on Li₂OAl₂O₃-GeO₂-P₂O₅ (LAGP) system with NASICON structure. Glass sample with nominal composition Li_1.5Al_0.5Ge_1.5P_2.5Si_0.5O₁₂ was prepared by melt-quenching technique. Non-isothermal crystallization kinetics was studied using DSC and activation energy of crystallisation was calculated to be ~ 246 kJ/mol using Kissinger’s equation. XRD of heat treated samples show the formation of required LiGe₂(PO₄)₃ phase along with other minor phases. Compositional analysis using SEM-EDX confirms enrichment of Ge and Si along the grain boundaries.