New high lithium ion conductor glass-ceramics with NASICON-type structure (Li1 + x + yAlxCryGe2 - x - y(PO4)(3), x + y = 0.5) were synthesized using melt-quenching method and converted to glass-ceramics through heat treatment. Influence of addition of different concentrations of aluminum and chromium in LiGe2(PO4)(3) glass ceramic was investigated. Substitution of Ge4+ ions by Al3+ and Cr3+ ions induced more Li+ ions in A(2) vacant sites and also changed the unit cell parameters and resulted in ionic conductivity improvement of glass-ceramics. The glass-ceramics were characterized by X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy-Dispersive X-ray spectroscopy (EDX), Differential Scanning Calorimetry (DSC), Complex Impedance Spectroscopy (CIS) and cyclic voltammetry (CV). The highest lithium ion conductivity of 6.65 x 10(-3) S/cm was obtained for x = 0.4 and y = 0.1 (Li1.5Al0.4Cr0.1Ge1.5(PO4)(3)) crystallized at 850 degrees C for 8 h with minimum activation energy of 0.292 eV. (C) 2016 Elsevier B.V. All rights reserved.