The effects of Li2O doping on solid-solid interactions in cobalt/magnesium mixed oxides system were investigated. The electrical properties of the produced solids were also studied. Pure and doped solids having different proportions of cobalt oxide were subjected to heat treatment at 600-1000 degreesC. The amounts of dopant were 2.5 and 5 mol% li(2)O. Results revealed that cobalt oxide dissolved in MgO lattice at temperature above 600 C and a complete dissolution occurred at 900 C. A limited portion of Li2O added dissolved in MgO lattice and the other portion interacted readily with cobalt species in cobalt-magnesium solid solution yielding lithium cobaltite (LiCoO2). The electrical conductivity a of the investigated system increases by increasing the mol fraction (MF) of cobalt species present reaching to a maximum limit at MF=0.13. This is due to creation of charge carrier (Co2+ ions) in MgO lattice. A relatively small increase in sigma was observed as a result of dissolution of a limited portion of Li2O in the lattice of solid solution, thus increasing the mobility of charge carriers. (C) 2003 Elsevier Science B.V. All rights reserved.