A series of single phase Ba1-xKxCe0.8Y0.2O3-delta (x = 0,0.1,0.2,0.3) perovskite oxides were fabricated with 60% potassium excess at 1000 degrees C for 3 h and further sintered at 1500 degrees C for 4 h via a citrate-nitrate combustion process. ICP-OES and AAS were used to verify the accurate composition. Conductivities of the perovskite oxides were measured under the atmosphere of 3%O-2 and 4.75 kPa H2O/Ar by using AC impedance spectroscopy technique. The bulk conductivity was significantly higher than the grain boundary conductivity, and the total conductivities increased with the increase of the measuring temperature. Among the perovskite oxides studied, Ba0.9K0.1Ce0.8Y0.2O3-delta displayed the highest total conductivity. Additionally, the transport numbers of proton, oxide ion and electron were measured by oxygen and water concentration cell. The results indicated that Ba1-xKxCe0.8Y0.2O3-delta were almost pure ionic conductors at 300-450 degrees C and mixed protonic-oxide ionic-electronic conductors at 450-900 degrees C under wet oxygen atmosphere, and Ba0.7K0.3Ce0.8Y0.2O3-delta displayed the highest protonic transport number. (C) 2017 Elsevier Ltd. All rights reserved.