Superionically conducting lithium aluminum germanium phosphate (LAGP) glass-ceramic and barium strontium titanate, Ba0.6Sr0.4TiO3 (0.6BST)-doped specimens were processed and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and AC impedance techniques. The XRD patterns exhibited the existence of LiGe2(PO4)(3) as the primary phase with impurity phases AIPO(4) and Li2O. SEM images revealed the presence of large LAGP crystals. The highest conductivity (5.08 x 10(-3) S cm(-1)) at 27 degrees C was obtained for the glass-ceramic sheet specimen crystallized at 850 degrees C for 12 h. Pelletized specimens prepared from the glass-ceramic powder and sintered at 850 degrees C for 9 h exhibited a slightly lower conductivity (4.62 x 10(-3) S cm-1) at 27 degrees C. The nonlinearity in the Arrhenius plots of total conductivity was attributed to the impurity phases, AlPO4 and Li2O and mediated the transport of lithium ion which is associated with higher activation energy. Doping of dielectric 0.6BST to the LAGP led to the shifting of the temperature of inflection towards the higher temperature in the Arrhenius plot of total conductivity and enhanced the space charge effect. (C) 2008 Elsevier B.V. All rights reserved.