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Ion-electron mixed conductivity of the Ce1&-xZrxO2 (0 < x < 1) series, prepared by solid-state reaction, has been measured as a function of temperature, pO2 and pH2O relative pressures. The structural analysis of this series shows the formation of monoclinic, tetragonal, and cubic phases as the Ce content increases. The temperature used in samples preparation, 1,923 K, favors at intermediate compositions the homogeneous Ce and Zr mixing in the metastable tetragonal t′ phase. The variation of conductivity with the relative oxygen pressure indicates that electronic contribution increases, becoming preponderant, as the Ce-content increases. The modifications in conductivity observed in Ce-rich samples have been ascribed to the enhancement of the electronic contribution at the grain-boundary of ceramics. The differences observed at low temperatures in electronic dc-conductivity of Ce-rich samples during heating and cooling treatments, have been ascribed to the incorporation of water as hydroxide defects at the grain boundary and interior of the particles. The surface hydroxylation is maximal in samples with improved OSC capacity, decreasing drastically in samples heated at 740 K. Finally, the potential application of prepared materials in intermediate temperature solid oxide fuel cells (SOFC) is discussed.