The solid solution 0.7Li(4)SiO(4)-0.3Li(3)PO(4) (LSP) is known to be a Li-ion conducting ceramic Aluminum doping of it was carried out to increase the ionic conductivity. The aluminum-doped LSP (LASP) was prepared with different amounts of dopant, to examine the effect of the amount of dopant on the ionic conductivity. LASP was synthesized using a sol-gel reaction and subsequent calcination. The crystalline phase of the LASP was analyzed by powder X-ray diffraction (PXRD) and identified as the monoclinic phase of 0.7Li(4 - y)Al(y)SiO(4)-0.3Li(3)PO(4). However, addition of aluminum results in the precipitation of a secondary crystalline Li2SiO3 phase. Li-ion conductivity was estimated by using electrochemical impedance spectroscopic (EIS) analysis on an LASP pellet that had been sintered at 1000 degrees C. In spite of the precipitation of the Li2SiO3 phase, Li-ion conductivity was increased by aluminum doping at 150 degrees C to approximately 20 times that of the undoped material (LSP), which effect is considered to be associated with vacancies generated by the aluminum doping providing conducting paths for the Li-ion. (C) 2016 Elsevier B.V. All rights reserved.