Concentration-cell measurement of proton transference number of SrCe0.95Yb0.05O3-δ

It is not so transparent to determine the proton transference number (tH+) of a proton-conducting oxide, e.g., SrCe1-xYbxO3-δ, from a concentration-cell open-circuit voltage (U), because in this case U is, in general, no longer a path-independent state property. We clarify this issue to validate the concentration-cell method, and correctly determine tH+ of SrCe0.95Yb0.05O3-δ. The experimental values for tH+ are precisely documented in the ranges of oxygen activity − 4 < log aO2 < 0.1 and of water vapor activity, − 5 < log aH2O < − 2 at 600°, 700°, and 800 °C, respectively, and discussed, in association with the total conductivity at e.g., 800 °C, in the light of defect structure of the oxide.