SmYb1-xMgxZr2O7-x/2 (0 <= x <= 0.15) ceramics are pressureless-sintered at 1973 K for 10 h in air. The structure and electrical conductivity of SmYb1-xMgxZr2O7-x/2 ceramics are investigated by the X-ray diffraction, scanning electron microscopy and impedance spectroscopy measurements. SmYb1-xMgxZr2O7-x/2 ceramics exhibit a defect fluorite-type structure. The measured electrical conductivities of SmYb1-xMgxZr2O7-x/2 ceramics obey the Arrhenius relation, and electrical conductivity of each composition increases with increasing temperature from 673 to 1173 K. At identical temperature levels, the electrical conductivity of SmYb1-xMgxZr2O7-x/2 ceramics gradually increases with increasing magnesia content. SmYb1-xMgxZr2O7-x/2 ceramics are oxide-ion conductors in the oxygen partial pressure range of 1.0 x 10(-4) to 1.0 atm at all test temperature levels. The electrical conductivity obtained in SmYb1-xMgxZr2O7-x/2 ceramics reaches the highest value of 2.72 x 10(-3) S cm(-1) at 1173 K for the SmYb0.85Mg0.15Zr2O6.925 ceramic. (C) 2010 Elsevier Ltd. All rights reserved.