This study deals with the effect of alkaline-earth metal substitution on the transport properties of the solid electrolytes Li8-2xMxZrO6 (M = Mg, Sr).The region of the solid solution in the Li8-2xMxZrO6 (M = Mg, Sr) systems was determined. The best effect of the dopant on the conductivity was observed for solid electrolyte Li7.85MBo.o75Zr06: the grain boundary conductivity for Li7.85Mg0.075ZrO6 is 2.3 . 10(-3), for Li8ZrO6 is 1.7 . 10(-4) S/cm; the bulk conductivity for Li7.85Mg0.075ZrO6 is 7.2 . 10(-3), and for Li8ZrO6 is 1.5 . 10(-4) S/cm at 355 degrees C. From the nuclear magnetic resonance (NMR) and impedance spectroscopy studies we propose the mechanism of Li+ ion transfer in the phase Li8ZrO6 and the solid solutions based on it. The ceramic samples of Li8-2xMxZrO6 (M = Mg, Sr) solid solutions were found to be stable with respect to lithium. (C) 2016 Elsevier B.V. All rights reserved.