The different electrical properties, sigma, epsilon', tan delta and E-sigma of pure and Li2O-doped CuO/MgO solid solution were investigated. The mole fraction of CuO (MF) was varied between 0.048 and 0.2. Pure and doped samples were subjected to heat treatments at 673 and 1073 K. The results revealed that the amount of CuO dissolved in MgO lattice increases progressively by increasing the MF as evidenced from the progressive decrease in the intensity of all diffraction lines of undissolved CuO phase. The dissolution process of copper ions in MgO lattice was accompanied by progressive increase in its lattice parameter. This process being conducted at 1073 K was accompanied by a significant progressive increase in the values of or, e' and tan 6 with subsequent decrease in the value of E, The increase in the MF value of CuO from 0.048 to 0.2 led to a significant increase in the value Of sigma(DC), measured at room temperature, from 6.33 x 10(-12) to 9.9 x 10(-10) Omega(-1) cm(-1) and E-sigma decreases from 0.76 to 0.58 eV. Li2O doping of the investigated system followed by calcination at 1073 K resulted in a measurable increase in values of or, 81 and tan 8 with subsequent decrease in E, These results were discussed in the light of the possible effective increase in the charge carriers concentration (Cu2+ ions dissolved in MgO lattice) and also to an effective increase in mobility of these charge carriers by Li2O doping. (c) 2005 Elsevier Ltd. All rights reserved.