Proton-conducting SrCe_0.9Yb_0.1O_3-α ceramic was prepared by high-temperature solid state reaction.X-ray powder diffraction pattern shows that the ceramic is of a single orthorhombic phase of perovskite-type SrCeO₃.Using the ceramic as solid electrolyte and porous platinum as electrodes, the measurements of conductivities and ionic transport numbers on SrCe_0.9Yb_0.1O_3-α ceramic were performed by using ac impedence spectroscopy and gas concentration cell methods in the temperature range of 600～1000℃ in dry air and wet hydrogen, respectively.The results indicate that the sample is a mixed conductor of oxide-ion and hole with the maximal conductivity of 0.026 S·cm^-1 and the oxide-ionic transport numbers of 0.03～0.2 in dry air.In wet hydrogen atmosphere, the sample has the maximal conductivity of 0.015 S·cm^-1.The protonic transport number is unity and the sample is a pure protonic conductor from 600 to 800℃.But in the temperature range of 900～1000℃, the sample exhibited a mixed conduction of proton and electron with the protonic transport numbers of 0.91～0.97.

Key words: perovskite-type oxide, gas concentration cell, impedance spectroscopy, proton conductor