We have investigated the effect of lithium yttrium-silicate glass 40.2Li(2)O.5.7Y(2)O(3).54.1SiO(2) on the density and total conductivity of tetragonal Li7La3Zr2O12. An optimal sintering temperature (1200 degrees C) was selected on the basis of a composite with 1 wt% of the glass having the highest density and total conductivity after annealing at this temperature. A series of composites Li7La3Zr2O12-x wt% 40.2Li(2)O.5.7Y(2)O(3).54.1SiO(2) (x = 1-10) was prepared. The samples were characterized by X-ray diffraction, scanning electron microscopy and differential scanning calorimetry. The data revealed that the sintering additive interacted with Li7La3Zr2O12, causing the glass to crystallize during annealing. The conductivity of the composites was studied using complex impedance spectroscopy over a temperature range of 20-250 C. The composite with x = 5 exhibited the highest total conductivity at room temperature: 2.5 x 10(-5) S cm(-1). (C) 2017 Elsevier Ltd. All rights reserved.